Laser segmented cutting, multi-step cutting, or both

Abstract

UV laser cutting throughput through silicon and like materials is improved by dividing a long cut path (112) into short segments (122), from about 10 μm to 1 mm. The laser output (32) is scanned within a first short segment (122) for a predetermined number of passes before being moved to and scanned within a second short segment (122) for a predetermined number of passes. The bite size, segment size (126), and segment overlap (136) can be manipulated to minimize the amount and type of trench backfill. Real-time monitoring is employed to reduce rescanning portions of the cut path 112 (112) where the cut is already completed. Polarization direction of the laser output (32) is also correlated with the cutting direction to further enhance throughput. This technique can be employed to cut a variety of materials with a variety of different lasers and wavelengths. A multi-step process can optimize the laser processes for each individual layer.

Description

FIGS. 5A-5F are simplified and partly schematic views of several possible embodiments of a laser processing system suitable for multi-step laser dicing or drilling.Nd:YAP,

With reference to FIGS. 21 and 22, a typical slider 210 includes a non-magnetic substrate 22 typically made of a ceramic material. Substrate 222 typically has a substrate depth, d_s, of about 300 μm deep and forms a majority of the body of slider 210. Substrate 222 generally, therefore, defines an air-bearing surface (ABS) 224 having an aerodynamic configuration suitable for lifting slider 210 a desired distance above the surface of disk 220 as it rotates. Transducer or magnetic head 214 has first and second spaced-apart magnetic pole pieces 228 and 230 which are located in proximity to trailing edge 212 of slider 210. Magnetic pole pieces 228 and 230 include first and second pole tips 232 and 234 that are aligned with the air-bearing surface 224. A non-magnetic gap layer 236 is located between the first and second pole pieces 228 and 230. Additionally, an insulating layer 238 is positioned between the non-magnetic layer 236 and the second magnetic pole piece 230. The insulating layer 238 is typically made of a polymeric material such as hard-baked photoresist, and a coil 240 is located within insulating layer 238. Finally, an overcoat layer 242, typically comprising 20-50 microns of a vacuum-deposited alumina (Al₂O₃), covers magnetic head 214 and forms trailing edge 212 of slider 210.

FIGS. 23-25 illustrate various steps or stages of a method for manufacturing typical sliders 210. FIG. 23 shows a deposited end view of a ceramic wafer 250 supporting a plurality of sliders 210. The various layers of each slider 210 are built up layer by layer upon the wafer 250 to form the previously described slider features by deposition processes known to the semiconductor industry. An exemplary technique for generating the layers of a slider having a thin-film magnetic head is described in U.S. Pat. No. 4,652,954.

Wafer 250 is then typically cut into sections and then sliced into rows 260 along straight slicing lanes 262 by a mechanical cutting blade to form coarse air-bearing surfaces 224 and generally parallel nonair-bearing surfaces 264. The mechanical cutting process creates sharp edges 266 and 268 (FIGS. 21 and 22) with small chips along slicing lanes 262. Conventional slicing blades typically have a narrow dimension of about 200-300 μm along their cutting axis and produce cuts that are wider than the blades. The slicing blades currently need to be this wide to withstand stresses of making straight cuts through the strength and thickness of conventional slider wafers 250, for example. Thus, the lane width, w₁, between rows 260 of sliders 210 is greater than cut width to accommodate cut width variations due to blade wear and misalignments. Hence, the row pitch equals w₁ plus h_s, and the maximum number of rows equals the usable wafer diameter, d_w, divided by the row pitch. A conventional row pitch is, for example, 600 μm.

Course air-bearing surfaces 224 formed in the wafer slicing process are polished using advanced but cumbersome and time-consuming lapping techniques and slurries. Rows 260 are mounted on a fixture or carrier 270 after ABS polishing so that multiple rows 260 can simultaneously be processed through subsequent steps. The mounting procedure must employ an adhesive between nonair-bearing surfaces 264 and carrier 270 that is selected for sufficient mechanical strength to withstand the stresses of a later step of mechanically dicing the rows 260 into individual sliders 210. Unfortunately, these adhesives make it difficult to debond sliders 210 from carrier 270 at a later time.

FIG. 24 illustrates rows 260 of sliders 210 mounted on carrier 270 and oriented so that the air-bearing surfaces 224 of magnetic heads 214 are facing upwards. With reference to FIG. 24, polished air-bearing surfaces 224 are covered by photoresist pattern masks 272 that correspond with a desired air-bearing surface configuration having aerodynamic characteristics suitable for causing heads 214 to fly a desired level above disks 220. Photoresist masks are formed by first coating the entire surface with photoresist. Then, a masking tool having a predetermined pattern is aligned relative to the pole tips 232 and 234 or other fiducials, and light is directed through the masking tool so that selected portions of the photoresist on the polished ABSs 224 are exposed. Alignment of the masking tool is achieved by using a stepper with row-bar alignment or a well-aligned contact/projected aligner. After exposure, the photoresist is developed such that the desired air-bearing surface configurations are left covered with the photoresist masks 272, while the remainder of the photoresist is removed.

Once rows 260 of sliders 210 have been masked with the desired pattern of photoresist, the polished ABSs are etched by etching techniques such as ion milling or reactive ion etching which are expensive and slow. Such etching techniques etch away the exposed regions 274 of surfaces 224 to a desired depth to form raised covered regions or rails 276 underlying masks 272. The photoresist mask 272 is finally stripped away to reveal the desired patterns on the air-bearing sides of sliders 210.

With reference again to FIG. 24, rows 220 are diced by mechanical dicing blade along straight dicing singulation or paths 278 to create edges 282. The dicing blades for this cutting operation have a narrow dimension of about 75-150 μm along their cutting axis and produce cuts of about 150 μm wide. Thus, the path width, w_p, between rows 260 of sliders 210 is slightly greater. Hence, the slider pitch equals w_p plus w_s, and the maximum number of sliders 210 per row 260 equals the row length (or usable wafer diameter) divided by the slider pitch. A conventional slider pitch is, for example, 1150 μm for a 100 μm wide dicing path. The dicing process creates small chips as it creates sharp edges 282, 284, and 286 and sharp corners 285 and 287 (FIG. 21) along singulation paths 278.

FIG. 25 also shows carrier 270 supporting a number of rows 260a, 260b, 260c, and 260d (generically rows 260) prior to dicing into individual sliders 210 with sides 280. Although row 260a depicts a typical row 260, rows 260b, 260c, and 260d demonstrate common slider manufacturing problems. Row 260b is relatively straight but is fixed to carrier 270 such that it is askew to row 260a. Row 260c is also relatively straight and relatively parallel to row 260a, but the pole tips 232 and 234 and/or the rails 276 of row 260c are offset with respect to those in row 260a. Row 260d exhibits row bow that may be primarily caused by stresses resulting from the mechanical slicing of wafer 250 into rows 260.

Because the dicing blade must cut along straight singulation paths 278, the sides 280 of sliders 210 in any column must be aligned within about one-half of the remainder of the path width minus the cut width. In view of the foregoing, rows 260b, 260c, and 260d can create a problem for the mechanical dicing operation and may reduce yield of sliders 210 with acceptable magnetic or aerodynamic properties. If the slant of row 260b is significant, the edges 282 of sliders in row 260b are askew with respect to rails 276, and the sliders 210 in row 260b will be defective. Similarly, many of sliders 210 in bowed row 260d, especially those at the ends for the case depicted, will be defective depending on the significance and position of the curves. With respect to row 260c, if the ABS features are sufficiently offset with respect to the other rows 260, then all sliders in row 260c will be defective since the edges of the sliders will be in improper positions or the dice paths will cut into ABS features.

The above-described process for manufacturing sliders 10 has several other drawbacks. In particular, sharp edges 266, 268, 282, 284, and 286, sharp corners 285 and 287, and chips formed during the dicing process make sliders 210 more susceptible to damage. For example, external shocks, such as by dropping a disk drive on the floor, can cause the sharp corners of the slider 210 to cut into the disk media, can cause cracks to propagate, or can cause particles to break loose at chipped which can then interfere with the ability of head 214 to make proper contact with disk 220. Polishing steps, which are time-consuming and employ expensive reagents, do not generally eliminate these chips or sharp edges.

In addition, the wide cuts made by the mechanical cutting blades significantly reduce the number of rows 260 and sliders 210 that can be fit onto each wafer 250. Skilled persons will also note that dicing blades tend to wear relatively quickly such that the width of their cuts may vary over time. In some cases, the blades can be inadvertently bent and then they produce curved or slanted cuts or increased chipping.

U.S. Pat. Nos. 5,872,684 of Hadfield et al. ('684 Patent) describes a method for etching a portion 288 of overcoat layer 242 wherein the etched portion 288 extends between the second pole tip 234 and trailing end 212 of slider 210. Etched portion 288 is sloped with respect to air-bearing surface 224 of slider 210 and is arranged and configured for preventing the overcoat layer from protruding past the air-bearing surface upon expansion of overcoat layer 242 during operation of magnetic head 214. Otherwise, overcoat layer 214 could form a protruding portion 290 due to localized heating when coil 240 is subjected to write currents and could interfere with slider/disk contact. Photolithography masking and etching techniques, like those described above, are used to etch away the potential protrusion regions of alumina overcoat layer 242. The '684 Patent does not address the dicing-generated chips or other dicing-related reliability problems.

Accordingly, one embodiment of the present invention employs a UV laser to cut ceramics, glasses, or silicon which may comprise the body of sliders 210, and particularly separate rows 260 or sliders 210 or round edges. A preferred process entails covering the surfaces of wafers 250, rows 260, or sliders 210 with a sacrificial layer such as photoresist, removing a portion of the sacrificial layer to create uncovered zones along existing edges or over intended edges; laser cutting wafers 250 into rows 260 or rows 260 into sliders 250; laser rounding edges 266, 268, 282, 284, and/or 286, and/or corners 285 and/or 287; cleaning debris form the uncovered zones such as by ion milling; and removing the sacrificial layer. Another process sequence includes an initial notching of the air-bearing surface 224 to form kerfs between rows 260 or sliders 210; laser processing to round the edges of the corners formed during the notching; and a final cutting to separate the rows or singulate the sliders.

FIGS. 26 and 27 are exemplary deposited end perspective views of alternative slider embodiments after processing in accordance with the invention as described herein. With reference to FIGS. 26 and 27, processed slider 350 exhibits rounded edges 352 where edges 282 have been processed by laser system output 330, and processed slider 360 exhibits rounded edges 362, 364, and 366 where edges 282, 266, and 286 have been processed by laser system output. Processed slider 360 also exhibits rounded corners 368 even when corners 285 have not been separately and intentionally processed by laser system output. Separately and intentionally processing corners 285 provides, however, a greater radius of curvature. Skilled persons will appreciate that upper edges 268 and/or 284 and/or upper corners 287 can also be rounded by laser system output if desirable. Sliders 350 and 360 are less susceptible to external shocks or chip generation than sliders 210, and sliders 350 and 360 can also ride closer to and make proper contact with disk 220.

FIG. 27A shows a variation of FIG. 27. With reference to FIG. 27A, a selected portion of edge 266 in proximity tip 369 is not rounded. In general, selected portions of any edge can be left unrounded whenever it is beneficial to do so. The positioning system 314 can simply be instructed to pass over such portions.

FIGS. 28a-28h (collectively FIG. 28) show simplified side sectional views of a generic workpiece as it undergoes process steps of an exemplary laser rounding process. In one embodiment, a mechanical cutting blade separates rows 60 or sliders 10 along lanes 62 or paths 78 to form surfaces 24 or sides 80, respectively. The respective edges 66 and/or 82 can then be rounded with laser system output. An advantage of this technique is that it suits the established infrastructure in the industry. Another advantage of mechanically cutting lanes 262 or paths 278 first is that there is no debris surrounding the cut so mechanical cutting provides the laser rounding operation with a flat surface that facilitates rounding the edges to a preferred radius of curvature.

With reference to FIG. 28a, an optional sacrificial protection layer 370 may be applied to patterned ABS 224 or all of the workpiece surfaces prior to laser rounding to protect ABS surface 224 and important ABS features 372, including rails 276 and pole tips 232 and 234, from redep and/or to facilitate cleaning of nonpermanent redep. A preferred sacrificial layer 370 comprises a conventional lithographic photoresist or a laser ablatable resist. Unfortunately, conventional materials used for sacrificial layer 370 have a tendency to burn when impinged by laser output suitable for laser rounding.

With reference to FIGS. 28b and 28c, it is preferable, therefore, to remove about a 10-25 μm wide area of sacrificial layer 370 from covering the ABS 224 in proximity to edges 266 or 282 to create a small uncovered zone 374. Uncovered zone 374 is preferably wider than the spot area of output but narrow enough so that all ABS features 372 remain covered. These strips of sacrificial layer 370 can be removed by conventional lithographic techniques, or by direct ablation or expose and etch solid-state UV laser techniques disclosed in U.S. Pat. No. 6,025,256 of Swenson et al. An example of parameters for resist-processing laser output 376 includes a beam positioning offset 378 of 10-20 μm from edge 266 or 282, a 7 μm bite size, at 14 kHz at 30 μJ at 266 nm. If direct laser ablation is performed, the laser output parameters, particularly the power density, are adapted to be insufficient to adversely affect ABS 24. In a preferred embodiment, the same laser system that is used to round edges 266 or 282 is used to remove the strip of sacrificial layer 370, but the laser output is generated at a higher repetition rate or the laser spot may be defocused to reduce the power density. FIG. 28c shows uncovered zone 374 after a strip of sacrificial layer 370 has been removed.

With reference to FIG. 28d, laser output is applied to ABS 224 in uncovered zone 374. Laser output is preferably positioned perpendicular to the ABS 224, with the spot centered at edges 266 or 282 (or corners 287), as shown; however, skilled persons will appreciate that other impingement angles and offsets from edges 266 or 282 can be employed. Although a single laser pass is preferable, multiple passes of laser output can be employed. FIG. 28e shows redep 380a on the surface of sacrificial layer 370 and redep 380b on the surface of rounded edge 362 or 164, collectively redep 380, that may result from application of laser output.

After the laser rounding operation shown in FIG. 28d, a cleaning operation shown in FIG. 128f can be used to remove any laser-generated debris 380 that may have accumulated in the uncovered zone 374. A major advantage of employing a sacrificial layer is that it permits the use of more aggressive cleaning techniques, such as ion milling or reactive ion etching (RIE), to remove redep 380b without risk of damage to ABS features 372. These aggressive cleaning techniques may also remove a surface portion of sacrificial layer 370 and any redep 380a thereon. Without sacrificial layer 370, less aggressive cleaning techniques, such as solvent or surfactant applications with or without ultrasound or mechanical scrubbing, are preferred. FIG. 28g shows slider 210 after cleaning. Finally, sacrificial layer 370 is stripped off the entire ABS 224, removing any remaining laser-generated debris 380a with it. FIG. 28h shows an uncovered slider 350 or 360 with its sharp edge removed.

FIGS. 29a-29f (collectively FIG. 29) show simplified side sectional views of a generic workpiece as it undergoes process steps of an exemplary laser cutting process (row slicing or slider dicing). With reference to FIG. 29a, an optional sacrificial protection layer 370 may be applied to patterned ABS 224 or all of the workpiece surfaces, as previously described, prior to laser cutting. With respect to the overall process of manufacturing sliders 210, in one example, sacrificial layer 370 is applied directly after ABS 224 has been patterned and before the photoresist mask 272 has been removed. Alternatively, the rounding and/or severing processes can be performed using mask 272 before or after patterning. It can also alternatively be applied after mask 272 has been removed or after sliders 210 have been singulated. Instead of, or in addition to, covering the surface with sacrificial layer 370, laser cutting may be performed from the back side of wafer 250 so that laser-generated debris 380 becomes irrelevant. Back side alignment can be accomplished with laser or other markings or through holes made from ABS 224 side of wafer 250, and/or edge alignment and/or calibration with a camera view of ABS features 372 or deposited face of trailing end 212.

With reference to FIGS. 29b and 29c, preferably a 10-50 μm wide area of sacrificial layer 370 covering ABS 224 in proximity to intended edges 266 and 268 or 282 is removed to create an uncovered zone 374. These strips of sacrificial layer 370 can be removed as previously described. If appropriate for a specific layout of rows 260 or sliders 210, a larger spot size 376a or multiple adjacent or overlapping trim lines 340 of laser output 376 can be employed for ablative removal of a strip of sacrificial layer 370. FIG. 29c shows uncovered zone 374 after the strip of sacrificial layer 370 has been removed.

With reference to FIG. 29d, laser output 390 is applied to ABS 224 in uncovered zone 374. Laser output 390 is preferably positioned perpendicular to the ABS 224, with the spot centered between intended edges 266 and 268 or 282 (or on corners 285), as shown; however, skilled persons will appreciate that other impingement angles and offsets from intended edges 266 and 268 or 282 can be employed. Multiple passes of laser output 390 are typically employed for both row slicing and slider dicing; however, slider dicing can be achieved in a single pass. Laser output 390 used for laser cutting may employ a higher peak power density than laser output used for laser rounding.

Although using common parameters for slicing through both the alumina and the AlTiC is advantageous for simplification, it may be desirable for throughput, for example, to employ different parameters for alumina slicing output 390a to slice through the alumina than for AlTiC slicing output 390b to slice through AlTiC. In particular, it may be desirable to use 266 nm or 355 nm to cut the alumina and 355 nm or 532 nm to cut the AlTiC. In one embodiment, row slicing through the alumina on multiple rows is performed with output 390a and then slicing through the AlTiC is performed in the notches with output 390b to finish the cuts. Alternatively, a row 260 may be sliced completely through with outputs 390a and 390b before a second row 260 is sliced. Each of the two different laser outputs 390 maybe applied in a single or in multiple passes. Switching the parameters of output 390 can be achieved with a single laser employing a switchable wavelength, repetition rate, or focus depth, or can be achieved through a multi laser head system, with different laser heads responsible for the different laser outputs 390. With respect to slider dicing, each traverse cut 396 (FIG. 31) traverses regions of slider 210 that are completely alumina and regions that are completely AlTiC. Accordingly, output 390a can be applied in one or more passes along the alumina portions of cuts 396 and then output 390b can be applied in one or more passes along the AlTiC portions of cuts 396. Alternatively, each cut 396 can be made completely one at a time, switching between alumina processing output 390a and AlTiC processing output 390b for each pass.

FIG. 29e shows separated edges 266, 268, or 282 with redep 380a on the surface of sacrificial layers 370 and redep 380b on the surface of edges 266, 268 or 282. FIG. 29f shows the beginning of the laser rounding process, described in connection with FIG. 28, that is applied to both edges 266 or 282. The debris 380 can optionally be cleaned off before the laser rounding process is performed to provide a flatter surface to facilitate rounding the edges to a preferred radius of curvature of about 20-25 μm. Although laser cutting without the additional laser rounding step will provide benefits over mechanical cutting, performing a laser rounding step in addition to laser cutting is preferred.

Applying one or more additional laser processing passes along the newly formed edges can change the radius of curvature along the edges. Furthermore, a more gradual slope can be obtained by employing one or a small number of passes slightly interior of an edge and gradually increasing the number of passes as the beam is positioned more closely to the edge. FIG. 30 shows a symbolic representation of forming such a gradually sloped edge 400 with the number of arrows in each column representing the number of passes. It is noted that an increased radius of curvature can also be achieved by performing one or multiple passes directly centered at the edge. Generally, the slope or angle of the edge or sidewall can be controlled by controlling the spacing of the lines of laser spots as well as the distances from the edge and number of passes. More passes at or near the edge results in a steeper angle, and passes further from the edge can be used to produce a shallower slope.

Although laser sacrificial layer strip removal, laser cutting, and laser rounding may entail multiple laser process steps at different parameters, an all laser process has many advantages and employs repositioning along only a single axis for each linear operation.

Laser cutting destroys significantly less material (kerfs of less than 50 μm wide and preferably less than 25 μm wide and typically about 10 μm wide) than does mechanical cutting (slicing lanes of about 300 μm wide and dicing paths of about 150 μm wide) so that devices on wafers can be manufactured much closer together, allowing many more devices to be produced on each wafer. Thus, the laser cutting process minimizes the pitch between rows and the pitch between devices. In an example, the pitch between rows 260 can be 350 μm and the pitch between slider can be 1025 μm, realizing about a 33% increase in the number of rows 260 and a gain of about one slider 210 for every thirteen sliders 210 per row 260.

Elimination of the mechanical cutting can also simplify manufacture of devices on workpieces 12. In particular, mechanical cutting can impart significant mechanical stress to devices such that they come off their carriers. To avoid losing rows, device manufacturers may employ strong adhesives or epoxies between the rows and the carrier. An all laser process significantly reduces the mechanical strength requirements of the adhesive used for fixturing the rows onto a carrier. Laser rounding and cutting, therefore, permits the elimination of strong adhesives or epoxies used to affix the rows to the carrier and the harsh chemicals needed to remove them. Instead, the adhesives can be selected for ease of debonding, such as the reduction of debond time and less exposure to potentially corrosive chemicals, and for amenability to UV laser processing, greatly reducing risk of damage to the devices, and thereby enhancing yield.

Laser row slicing reduces row bow because laser slicing does not exert as much mechanical stress as mechanical slicing. However, if row bow or other of the row defects are apparent, the rows can be laser diced (and re-sliced) to compensate for these defects without concern for the critical device to device alignment needed between rows for mechanical dicing. For convenience, the term (through) cutting may be used generically to include slicing (often associated with wafer row separation) or dicing (often associated with part singulation from wafer rows), and slicing and dicing may be used interchangeably in the context of this invention.

Because positioning system 30 can align to through holes or fiducials, laser system 10 can process each row and/or each device independently. With respect to slanted rows, the laser spot can perform traverse cuts across the slanted rows at appropriate positions with respect to outer edges of the devices with stage and/or beam translations between each cut to effect a rectangular or curvilinear wave patterns as desired. Thus, laser dicing can compensate for row fixturing defects and perhaps save entire rows of devices that would be ruined by mechanical dicing.

FIG. 31 demonstrates an exemplary laser process for row defect compensation using transverse cuts 396 and stage and/or beam translations 398 to generally make cuts 396 at angles such that the surfaces of sliders 210 are substantially perpendicular to each other. Numerous other cutting patterns are possible such as making all cuts in a first column before making all cuts in second column. Sliders 210 in rows 260a, 260b, and 260c can be singulated in a similar fashion regardless of angle or offset. With respect to row 260d, the rectangular wave cut and translate pattern can be curved to align with the row bow.

FIG. 32 shows a flow diagram of a simplified cutting and rounding process with simplified side sectional views of a generic workpiece such as wafer 250 as it undergoes process steps. In this alternative embodiment, a mechanical cutting blade or laser output 390 notches rows 260 or sliders 210 along lanes 262 or paths 278 to a depth, preferably above an adhesive layer if a combination of laser and mechanical notching or cutting is to be employed. Alternatively, for preslice notching, laser output 390a may be employed to notch all the way through the alumina material. FIG. 32b shows the result of laser notching with a solid line and shows the result of mechanical notching with a broken line. Laser output then rounds the desired edges and/or corners, and finally the mechanical cutting blade or laser output 390 finishes the separation of rows 260 or singulation of sliders 350 or 360. The width of the kerf or diameter used for the cutting process can be less than or equal to the width of the kerf or diameter used for the notching process. A sacrificial layer 370 and the related steps associated with it may be employed prior to a notching process. Skilled persons will appreciate that edges on the bottom side can optionally be done by this notching technique, preferably such that top and bottom alignment is conserved. Such notching would greatly facilitate subsequent laser separation of the rows 260 or sliders 210, 350, or 360. One advantage of this technique is that there are fewer pieces to align since the parts are still referenced to each other, i.e., the rounding is completed before the pieces are separated. Another advantage is that the preliminary notch does not expose the adhesive layer where mechanical cutting is to be employed, since the adhesives needed to withstand mechanical cutting are particularly volatile in response to laser radiation.

FIG. 33 shows a flow diagram of an alternative cutting and rounding process with simplified side sectional views of a generic workpiece as it undergoes process steps. With reference to FIG. 33, rounding laser output 330 is applied along two parallel trim lines. The trim lines are spaced such that the edges 282 of the dice lane 278 align with the centers of the trenches 402 produced by the laser outputs 330. In FIG. 33b, a dice blade or laser cuts the workpiece surface between the trenches 402 to produced rounded separate parts shown in FIG. 33c.

FIG. 34 shows an alternative rounding, notching, and separating process. In FIG. 34a, multiple adjacent passes of laser output 330 or 390 create an extra wide notch (FIG. 34b) with rounded edges. Then output 390 or a cutting blade is applied to separate the rows 260 or sliders 210. This process creates a shelfed edge shown in FIG. 34c. The edges of the lower shelves can be rounded with processes previously discussed. It may be useful to use several different parameters for various passes in one notching step to tailor the notch geometry, including sidewall angle (FIG. 34b₂ or 34b₃)).

With reference to FIGS. 29 and 31-34, it may be desirable to notch through one side of the workpiece, preferably about one half the thickness of the workpiece, and then finish the row or slider separation from the opposite side, preferably by flipping the workpiece and using alignment techniques previously discussed. This embodiment may provide significant throughput advantages particularly for high-aspect ratio kerfs. The rounding process can be performed before or after notching or after row or slider separation.

FIG. 35 demonstrates that an excimer laser at an appropriate UV wavelength can be used with appropriate-sized line-making masks 410 or 412 (about the width of preferred Gaussian spot sizes) for the above-described laser dicing or rounding operations without employing the preferred bite size technique. The line-making masks 410 or 412 can have a length the size of an entire column or as little as the desired edge. For example, the surfaces of wafers 250, rows 260, or sliders 210 can be covered with sacrificial layer 370; the portions of the sacrificial layer 370 can be removed to create uncovered zones; wafers 250 and/or rows 260 can be diced and edges 266, 268, 282, 284, and/or 286, and/or corners 285 and/or 287 can be rounded with a UV excimer through a line mask of an appropriate shape and size; the entire surface can be aggressively cleaned to remove debris from the uncovered zones; and the sacrificial layer can be removed.

Another application of the segment cutting method is to produce MEMS (microelectronic machine system) devices 160. FIG. 19 is a representative illustration of ultraviolet laser cutting of a MEMS device 160. In one preferred embodiment, the MEMS device 160 is cut using the method described above to create trenches 162a, 162b, 162c, 162d, and 162e (generically trenches 162) in silicon and to create a depression 164 by employing a pattern of adjacent trenches 162. Skilled persons will appreciate that through computer control of the X and/or Y axes of the laser positioning system 30, the directed laser system output pulses 32 can be directed to the work surface such that overlapped pulses create a pattern which expresses any complex curvilinear geometry. Skilled persons will appreciate that the segmented cutting techniques and other processing techniques disclosed herein can be used to cut arcs and other curves for nonMEMS applications as well.

Another application of the segmented cutting method is to process optical integrated circuits, such as an arrayed waveguide gratings (AWG) device 170 produced on semiconductor wafer workpieces 12. FIG. 20 is a representative illustration of ultraviolet ablative patterning of an AWG device 170. In one preferred embodiment, the AWG device 170 is patterned using the method described above to create curvilinear trenches 172, with portions 172a, 172b, 172c, 172d, and 172e in silicon, for example. Although trench 172 is shown to be symmetric, skilled persons will appreciate that through computer control of the X and/or Y axes of the beam positioning system 30, the laser system output pulses 32 can be directed to the work surface such that overlapped pulses 32 create a pattern which expresses any complex curvilinear profile or geometry. Skilled persons will appreciate that segments 122 are not required to be linear and can be arcs such that each portion 172 can be processed with one or more nonlinear segments 122. This capability may be used to produce complex curvilinear geometric patterns in silicon useful for efficient production of a variety of AWG devices 170. Skilled persons will also appreciate that the segmented cutting techniques could be employed to produce large diameter through hole or blind vias.

The '382 application of Fahey et al. describes techniques for forming rounded edges along cuts, as well as for laser slicing and dicing ceramic wafers. Many of these techniques, as well as the alignment techniques disclosed therein, can be advantageously incorporated into the present invention to cut silicon wafers and further improve the quality of and processing speed for cutting ceramic or other brittle, high melting temperature materials, such as glasses. U.S. patent application Ser. No. 09/803,382 is herein incorporated by reference.

It is contemplated that performing the cuts in a reactive gas atmosphere, such as an oxygen-rich atmosphere, will generate debris that is easier to cut. In an oxygen rich environment, for example, it is proposed that the hot ejected silicon will more likely form SiO₂ in an exothermic reaction that may keep any resulting SiO₂ backfill redep at a higher temperature for a longer time making it less likely to stick strongly on the silicon and/or making it easier to clean from a trench with a quick subsequent laser pass 132. To the extent that redep (or exposed trench material) cooling or resolidification is a factor, this recharacterization time interval may to some extent influence the maximum preferred length 126 of segments 122 such that the laser spot can process length 126 and return to impinge again any redep (or warmed exposed trench material) at the initial laser pass 132a and subsequent laser passes 132 before the redep (or exposed trench material) cools or sticks strongly.

Skilled persons will also appreciate that purge gases, such as nitrogen, argon, helium, and dry air, may be usefully employed to assist in the removal of waste fumes from the workpiece 12 and more preferably to blow potential backfill through any existing throughcut portions along cut path 112. Such purge gases can be delivered to the close vicinity of the work surface using delivery nozzles attached to laser system 10.

If desirable, silicon workpieces 12 processed in accordance with the present invention may be cleaned using ultrasonic baths in liquids including but not limited to water, acetone, methanol, and ethanol to improve the surface quality of affected areas. Those skilled in the art will also recognize that cleaning of processed silicon workpieces 12 in hydrofluoric acid can be beneficial in removing unwanted oxide layers.

Although the present invention is presented herein only by way of example to silicon wafer cutting, skilled persons will appreciate that the segmented cutting techniques described herein may be employed for cutting a variety of target materials including, but not limited to, other semiconductors, GaAs, SiC, SiN, indium phosphide, glasses, ceramics, AlTiC, and metals with the same or different types of lasers including, but not limited to, solid-state lasers, such as YAG or YLF, and CO₂ lasers, of similar or different UV, visible, or IR wavelengths.

U.S. Prov. Pat. Appl. No. 60/301,701, filed Jun. 28, 2001, entitled Multi-Step Laser Processing for the Cutting or Drilling of Wafers with Surface Device Layers of Fahey et al., which is herein incorporated by reference describes multi-step techniques for cutting wafers and the device layers they support with different severing processes, such as different laser parameters. This multi-step process involves the optimization of laser processes for each individual layer, such that the processing of any one layer or the substrate material does not negatively affect the other layers. A preferred process entails the use of UV lasers for cutting layers that are transparent in the IR or visible range, allowing for a different laser to be used for cutting the wafer than is used for cutting the layers. This process permits significantly less damage to the layer than would occur if only one laser, such as an IR laser, were used to cut through the entire layer and wafer structure. Furthermore, this laser processing of the layers allows for the optimization of other cutting processes, such as the use of a wafer saw, in order to reduce or eliminate the damage to the layers on the wafer. One example employs a UV laser 10 to cut layers that include ceramic, glass, polymer or metal films on the top or bottom surfaces of the wafer substrate, while a different laser, such as a 532 nm laser or IR laser, or the same laser or optical system run with different process parameters is used to cut through the substrate material after the surface layers have been cleared away. Each of the laser processes may employ the same or different segmented cutting techniques that cooperate with the other laser parameters chosen to facilitate high quality and throughput. Alternatively, surface layers may be processed by conventional full scan processing while the thicker substrate layer may be processed by a segmented technique.

One embodiment entails covering the surfaces of the wafer with a sacrificial layer such as photoresist; optionally removing a portion of the sacrificial layer to create uncovered zones over intended cutting areas; laser cutting the layers atop the wafer substrate to a width equal or greater than that which will occur in the subsequent substrate cutting step; then cutting the wafer with a separate processing step or steps using a different laser, wavelength, pulse width, fluence, bite size, and/or other laser processing parameters.

Another embodiment allows for removal of the surface layer or layers with one laser process or several laser processes and then employs a subsequent process or several subsequent processes that complete the cutting with a non-laser technique that only has to remove the wafer substrate material. One example of such technique is the removal of all metal, polymer or other soft material from the cutting lane using the laser, such that during subsequent cutting with a saw blade, the blade only makes contact with the substrate material. This technique will be of particular use when cutting wafers with metallization in the dice lanes, such as that due to the presence of test devices, or wafers which have a polymer dielectric material such as some of the low-K materials that are presently on the market.

FIGS. 36a-36f (collectively FIG. 36) show simplified side sectional views of a generic workpiece as it undergoes process steps of an exemplary laser dicing or drilling process. In one embodiment, separate processing steps are used in succession to cut through the layers 470, 472 in order from the top layer 470 down to the substrate 522 (FIGS. 36a, 36b, 36c, and 36e). Depending upon preference and upon the layer materials, it may be of interest to choose the FIGS. 36c-36d process, in which lower layers 472 are opened to successively smaller cut widths in order to not have the successive processes affect the overlayer. The typical best case would be the process of FIGS. 36e-36f, where all layers are cleared open to the same width. Finally (FIGS. 36d, 36f), the substrate 522 is cut in the position where the layers have been cleared off by the earlier processes. In this figure, the cuts shown are cross sections of a cut which may either be a dicing cut or a drilled via. If necessary, further process steps may occur where the laser is used to clean up the edges of the cuts made in the earlier steps. While the layer cuts and cleanup steps will be done with a laser, the step which involves cutting through the substrate may be done with a laser or with another technique such as mechanical sawing.

With reference to FIG. 36a, the top layer 470 could either be a device layer, or could be an optional sacrificial protection layer to protect important features, such as solder bumps on die or features on die (laser diodes, optical waveguides or MEMS components, etc.) from redep and/or to facilitate cleaning of nonpermanent redep. A preferred sacrificial layer comprises a conventional lithographic photoresist or a laser ablatable resist. Unfortunately, conventional materials used for sacrificial layer have a tendency to burn when impinged by laser output suitable for dicing or removal of many types of device layer. As shown in FIG. 36c, it is therefore preferable to remove about a 10-25 μm wider area of the sacrificial layer in proximity to the edges of the notches to be made in the underlying layers to create a small uncovered zone. These strips of sacrificial layer can be removed by conventional lithographic techniques, or by direct ablation or expose and etch solid-state UV laser techniques disclosed in U.S. Pat. No. 6,025,256 of Swenson et al. An example of parameters for resist-processing laser output includes a beam positioning offset 178 of 10-20 μm from edge 266 or 282, a 7 μm bite size, at 14 kHz at 30 μJ at 266 nm. If direct laser ablation is performed, the laser output parameters, particularly the power density, are adapted to be insufficient to adversely affect the underlying device layers or substrate material. In a preferred embodiment, the same laser system that is used to round edges 266 or 282 is used to remove the strip of sacrificial layer, but the laser output 522 is generated at a higher repetition rate or the laser spot may be defocused to reduce the power density.

One skilled in the art will realize that an excimer laser at an appropriate UV wavelength can be used with appropriate-sized line-making masks (about the width of preferred Gaussian spot sizes) for the above-described laser dicing operations for those layers which require UV ablation. The line-making masks can have a length the size of an entire column or as little as the desired edge of each die. For example, in FIG. 36, a UV excimer through a line mask of an appropriate shape and size could be used to perform the ablation steps in FIG. 36b, 36c, 36e, 36d, or 36f if that laser is appropriate for cutting the material of interest in that particular process step. In addition, it could be used for the removal of any sacrificial layer atop the wafer. Skilled persons will appreciate that if the semiconductor industry moves toward making die on different types of wafers, like InP, SOS, SOI, etc., the rounding and cutting processes disclosed herein can be applied to devices manufactured with or on such wafers. Silicon carbide and titanium carbide, or other insulating (non-semiconductor) substrates, may also be similarly processed.

Another embodiment of the invention provides such a method or system that modifies the geometry of the layer or layers by one or several laser processes 530 such that the subsequent cutting or drilling of the substrate does not cause damage in the active area of the devices. For example (FIG. 8), a process sequence may include an initial notching of layer or layers on either side of the cut without removing all the material from the dice lane area such that the outermost edges formed by the laser trenches are unaffected by the subsequent substrate dicing process. As discussed above, this laser notching would be performed using parameters specifically optimized for cutting the layers cleanly without inducing damage that would occur if substrate dicing parameters were used. Use of this geometry modification would include, but is not limited to, the formation of trenches or other shapes outside the dicing kerf which would act as crack stops or mechanisms for arresting delamination which may be induced by the wafer substrate dicing step. These notches may extend only to the bottom of the layers or may extend further into the substrate material depending on the damage mode which is anticipated during the dicing process. For example, if the layers are delaminating during the subsequent cutting process, the notches need only go below the interface of interest. If the substrate material is being damaged during the subsequent cutting process, it may be of interest to make the notches penetrate more deeply into the substrate material.

It will be obvious to those having skill in the art that many changes may be made to the details of the above-described embodiment of this invention without departing from the underlying principles thereof. The scope of the present invention should, therefore, be determined only by the following claims.

Claims

1. A method of increasing throughput in a laser cutting process, comprising:

directing a first pass of first laser pulses to impinge along a first segment of a cutting path having a cutting path length greater than 100 μm, each first laser pulse having a first spot area on a workpiece, the first segment having a first segment length that is longer than the first spot area and shorter than the cutting path length;

directing a second pass of second laser pulses to impinge along a second segment of the cutting path, each second laser pulse having a second spot area on the workpiece, the second segment having a second segment length that is longer than the second spot area and shorter than the cutting path length, the second segment overlapping the first segment by an overlap length greater than at least the first or second spot areas; and

after directing at least the first and second passes of laser pulses, directing a third pass of third laser pulses to impinge along a third segment of the cutting path, each third laser pulse having a third spot area on the workpiece, the third segment having a third segment length that is longer than the third spot area and shorter than the cutting path length, the third segment including a subsequent portion of the cutting path other than the first or second segments, wherein the subsequent portion of the cutting path has a nonoverlap length greater than the first, second, or third spot areas.

2. The method of claim 1 in which major portions of the first and second segments overlap.

3. The method of claim 1 in which the second segment includes the first segment.

4. The method of claim 3 in which the first and second segments are processed in a same direction.

5. The method of claim 3 in which the first and second segments are processed in opposite directions.

6. The method of claim 1 in which the first and second segments are processed in a same direction.

7. The method of claim 1 in which the first and second segments are processed in opposite directions.

8. The method of claim 1 in which additional sets of first and/or second laser pulses are applied to the first and/or second segments to form a through trench within the first and/or second segments prior to applying the third laser pulses.

9. The method of claim 1 further comprising:

forming a through trench in the first and/or second segments prior to applying the third laser pulses.

10. The method of claim 1 further comprising:

forming a through trench in the first and/or second segments with multiple passes of laser pulses prior to applying the third laser pulses; and

forming a through trench within the third segment.

11. The method of claim 10 further comprising:

forming a through trench along the entire cutting path length.

12. The method of claim 11 in which the cutting path length is greater than 1 mm and the first, second, and third segment lengths are between about 10 μm and about 500 μm.

13. The method of claim 1 in which the cutting path length is greater than 1 mm and the first, second, and third segment lengths are between about 10 μm and about 500 μm.

14. The method of claim 13 in which the cutting path length is greater than 10 mm and the first, second, and third segment lengths are between about 200 μm and about 500 μm.

15. The method of claim 13 in which the first, second, and third laser pulses are characterized by a UV wavelength, a pulse repetition frequency of greater than 5 kHz, pulse energies of greater than 200 μJ, and a bite size of about 0.5 to about 50 μm.

16. The method of claim 1 in which the first, second, and third laser pulses are characterized by a UV wavelength, a pulse repetition frequency of greater than 5 kHz, pulse energies of greater than 200 μJ, and a bite size of about 0.5 to about 50 μm.

17. The method of claim 16 in which the workpiece has a thickness greater than 50 μm.

18. The method of claim 17 in which the workpiece has a thickness greater than 500 μm.

19. The method of claim 12 in which the workpiece has a thickness greater than 50 μm.

20. The method of claim 12 in which the workpiece has a thickness greater than 500 μm, the cutting path length is greater than 100 mm, and the throughout along the entire length of the cutting path is made with fewer than 25 passes of laser pulses over any position along the cutting path.

21. The method of claim 13 in which the workpiece has a thickness greater than 200 μm, further comprising:

cutting through the entire thickness along the cutting path at a cutting speed of greater than 10 mm per minute.

22. The method of claim 21 in which a major portion of the thickness of the workpiece comprises a semiconductor material, a glass material, a ceramic material, or a metallic material.

23. The method of claim 21 in which a major portion of the thickness of the workpiece comprises Si, GaAs, SiC, SiN, indium phosphide, or AlTiC.

24. The method of claim 22 in which the laser pulses are generated from a solid-state laser or a CO₂ laser.

25. The method of claim 1 in which the laser pulses are generated from a solid-state laser or a CO₂ laser.

26. The method of claim 2 in which the overlap length of the first and second portions or the first or second segment lengths are sufficiently short such that the second laser pulses impinge along the overlap length before a major portion of any debris generated by the first laser pulses cools along the overlap length to ambient temperature.

27. The method of claim 1 in which the third segment excludes the first or second segments.

28. The method of claim 1 in which the first laser pulses impinge along the cutting path in a first cutting direction and the first laser pulses have a first polarization orientation that is parallel to the first cutting direction, in which the third laser pulses impinge along the cutting path in a third cutting direction and the third laser pulses have a third polarization orientation that is parallel to the third cutting direction, and in which the first and third cutting directions are transverse.

29. The method of claim 28 further comprising:

employing a polarization control device to change from the first polarization orientation to the third polarization orientation.

30. The method of claim 10 further comprising:

monitoring throughout status with a throughout monitor to determine throughout positions where throughcuts have been affected along the cutting path; and

reducing impingement of the throughcut positions during the passes of first, second, third, or subsequent laser pulses in response to information provided by the throughout monitor.

31. The method of claim 1 in which the laser pulses within the first pass have generally similar parameters.

32. The method of claim 1 in which the laser pulses of the first, second, and third passes have generally similar parameters.

33. The method of claim 1 in which the laser pulses of at least two of the first, second, and third passes have at least one generally different parameter.

34. The method of claim 1 in which at least two of the laser pulses in at least one of the first, second, or third passes have at least one generally different parameter.

35. The method of claim 1 in which multiple passes of laser pulses are applied to the first segment to form a throughout within the first segment.

36. The method of claim 35 in which the throughcut is formed in the first segment before the pass of second laser pulses is applied to the second segment.

37. The method of claim 36 in which multiple passes of laser pulses are applied to the second segment to form a throughout within the second segment.

38. The method of claim 37 in which the throughout is formed in the second segment before the pass of third laser pulses is applied to the third segment.

39. The method of claim 38 in which multiple passes of laser pulses are applied to subsequent segments to sequentially form throughcuts within the respective subsequent segments to form a full length throughcut along the cutting path length.

40. The method of claim 1 in which only minor portions of the first and second segments overlap.

41. The method of claim 1 in which the first laser pulses impinge along the cutting path in a first cutting direction and the first laser pulses have a first polarization orientation that is oriented to the first cutting direction to enhance throughput or cut quality, in which the third laser pulses impinge along the cutting path in a third cutting direction and the third laser pulses have a third polarization orientation that is oriented to the third cutting direction to enhance throughput or cut quality, and in which the first and third cutting directions are transverse and the first and third polarization orientations are transverse.

42. The method of claim 1 in which at least one of the segments is an arc.

43. The method of claim 1 in which a purge gas is employed to facilitate blowing potential backfill debris through throughcuts along the cutting path.

44. The method of claim 1 in which an elongated laser pass that includes at least three first, second, and third segments is applied to the cutting path.

45. The method of claim 1 in which each spot area along a segment is in proximity to or partly overlaps the spot area of a preceding laser pulse.

46. A method of increasing throughput for forming a cut along a cutting path having a cutting path length on a workpiece, comprising:

selecting a segment length that is shorter than the cutting path length;

directing a first pass of first laser pulses having first spot areas to impinge the workpiece along a first segment of about the segment length along the cutting path;

directing a second pass of second laser pulses having second spot areas to impinge the workpiece along a second segment of about the segment length along the cutting path, the second segment overlapping the first segment by an overlap length greater than at least the first or second spot areas; and

after directing at least the first and second passes of laser pulses, directing a third pass of third laser pulses having third spot areas to impinge along a third segment of about the segment length along the cutting path, the third segment including a portion of the cutting path that extends beyond the first or second segments, wherein the portion of the cutting path has a portion length greater than the first, second, or third spot areas.

47. The method of claim 46 in which impingement of laser pulses along the cutting path generates debris and in which the overlap length or the segment length is sufficiently short such that the second pass of second laser pulses impinge along the overlap length before a major portion of any debris generated by the first laser pulses cools to ambient temperature along the overlap length.

48. A method of increasing throughput in a laser cutting process, comprising:

directing a first pass of first laser pulses to impinge along a first segment of a cutting path having a cutting path length, each first laser pulse having a first spot area on a workpiece, the first segment having a first segment length that is longer than the first spot area and shorter than the cutting path length;

directing second passes of second laser pulses to impinge along a second segment of the cutting path, the second segment including an overlap length that overlaps at least a portion of the first segment until a throughcut is made within the overlap length, each second laser pulse having a second spot area on a workpiece, the second segment having a second segment length that is longer than the second spot area and shorter than the cutting path length, the overlap length being greater than at least the first or second spot areas; and

after directing at least the first and second passes of laser pulses, directing third passes of third laser pulses to impinge along a third segment of the cutting path until a throughcut is made within the third segment, each third laser pulse having a third spot area on a workpiece, the third segment having a third segment length that is longer than the third spot area and shorter than the cutting path length, the third segment including a portion of the cutting path that extends beyond the first or second segments, wherein the portion of the cutting path has a portion length greater than the first, second, or third spot areas.

49. The method of claim 1 in which the overlap length of the first and second portions or the first or second segment lengths are in a range appropriate so as to exploit with second laser pulses persistence of a selected transient effect arising from the interaction of first pulses with the workpiece along the overlap length.

50. The method of claim 46 in which the overlap length of the first and second portions or the first or second segment lengths are in a range appropriate so as to exploit with second laser pulses persistence of a selected transient effect arising from the interaction of first pulses with the workpiece along the overlap length.

51. The method of claim 48 in which the overlap length of the first and second portions or the first or second segment lengths are in a range appropriate so as to exploit with second laser pulses persistence of a selected transient effect arising from the interaction of first pulses with the workpiece along the overlap length.

52. A method for laser processing, comprising:

directing to a workpiece a primary group of passes of primary laser pulses to impinge locations along a primary segment of a cutting path that is continuous and has a cutting path length, each primary laser pulse having a primary spot area that defines a primary spatial major axis on the workpiece and impinging a location along the primary segment, the primary segment having a primary segment length that is longer than the primary spatial major axis and shorter than the cutting path length, and at least some of the locations along the primary segment length being impinged multiple times by the primary laser pulses of the primary group of passes;

directing to the workpiece a secondary group of passes of secondary laser pulses to impinge locations along a secondary segment of the cutting path, each secondary laser pulse having a secondary spot area that defines a secondary spatial major axis on the workpiece and impinging a location along the secondary segment, the secondary segment having a secondary segment length that is longer than the secondary spatial major axis and shorter than the cutting path length, and at least some of the locations along the secondary segment length being impinged multiple times by the secondary laser pulses of the secondary group of passes, the secondary segment overlapping the primary segment by an overlap length greater than at least the primary or secondary spatial major axes; and

after directing to the workpiece at least the primary and secondary groups of passes of respective primary and secondary laser pulses, directing to the workpiece a tertiary group of passes of tertiary laser pulses to impinge locations along a tertiary segment of the cutting path, each tertiary laser pulse having a tertiary spot area that defines a tertiary spatial major axis on the workpiece and impinging a location along the tertiary segment, the tertiary segment having a tertiary segment length that is longer than the tertiary spatial major axis and shorter than the cutting path length, and at least some of the locations along the tertiary segment length being impinged multiple times by the tertiary laser pulses of the tertiary group of passes, the tertiary segment including a subsequent portion of the cutting path other than the primary or secondary segments, wherein:

the subsequent portion of the cutting path has a nonoverlap length greater than any one of the primary, secondary, and tertiary spatial major axes;

the workpiece comprises a wafer substrate supporting an electronic device, the wafer substrate including a ceramic or glass target material;

at least one of the primary, secondary, and tertiary groups of passes of respective primary, secondary, and tertiary laser pulses comprises a first laser pulse of first Gaussian laser output having a substantially Gaussian irradiance profile characterized by a center of a peak irradiance amount and a peripheral region of a peripheral irradiance amount that is less than the peak irradiance amount;

a major portion of the first Gaussian laser output propagates through an aperture configured to convert the major portion of the first Gaussian laser output into a first apertured output having an irradiance profile characterized by an apertured peripheral irradiance amount that is reduced relative to the peak irradiance amount;

the first apertured output is directed to impinge a first target location in the respective primary, secondary, or tertiary segment with a first spot area defining a first respective primary, secondary, or tertiary spot area on the ceramic or glass target material, the first apertured output causing depthwise removal of an amount of target material at the first target location on the surface;

the at least one of the primary, secondary, and tertiary groups of passes of respective primary, secondary, and tertiary laser pulses comprises a second laser output pulse of second Gaussian laser output having a substantially Gaussian irradiance profile characterized by a center of a peak irradiance amount and a peripheral region of a peripheral irradiance amount that is less than the peak irradiance amount;

a major portion of the second Gaussian laser output propagates through an aperture configured to convert the major portion of the second Gaussian laser output into a second apertured output having an irradiance profile characterized by an apertured peripheral irradiance amount that is reduced relative to the peak irradiance amount; and

the second apertured output is directed to impinge a second target location in the respective primary, secondary, or tertiary segment with a second spot area defining a second respective primary, secondary, or tertiary spot area that partly overlaps the first spot area by a region of spot overlap on the target material, the second apertured output causing depthwise removal of an amount of target material at the second location and generating debris that contacts the workpiece, the region of spot overlap specifying a region of spot nonoverlap of the second and first spot areas that corresponds to a bite size of the second apertured output, the bite size being set, in cooperation with the configuration of the aperture converting the major portion of the second Gaussian laser output into the second apertured output, to facilitate laser spot irradiance profile and target material depthwise removal control of the second apertured output and thereby cause the generation of debris in a form of cleanable, nonpermanent redeposited material contacting the workpiece.

53. The method of claim 52, further comprising removing the nonpermanent redeposited material contacting the workpiece by a nonaggressive cleaning technique that entails mechanical scrubbing, solvent bathing, or ultrasonic vibrating.

54. The method of claim 52, further comprising:

directing each of the first and second Gaussian laser outputs to propagate along an optical path through a beam-shaping component that imparts greater uniformity to the major portion of the Gaussian laser output before it propagates through the aperture.

55. The method of claim 54, in which the major portions of the first and second Gaussian laser outputs to which uniformity is imparted become respective first and second shaped outputs having shaped irradiance profiles, and further comprising:

directing the first and second shaped outputs through one or more imaging lens components to form for the first and second apertured outputs imaged, shaped irradiance profiles.

56. The method of claim 55, in which the first and second apertured outputs formed with imaged, shaped irradiance profiles have respective first and second energy densities over the respective first and second spot areas, and the first and second energy densities are greater than a fluence below which the second apertured output generates debris in a form of permanent redeposited material contacting the workpiece.

57. The method of claim 52, further comprising removing the nonpermanent redeposited material contacting the workpiece by mechanical scrubbing, solvent bathing, ultrasonic vibrating, ion milling, or reaction ion etching.

58. The method of claim 52, in which the first and second apertured outputs comprise energy densities of greater than about 500 MW/cm² per pulse.

59. The method of claim 52, in which the region of spot nonoverlap of the second and first spot areas comprises a bite size of 1-7 μm.

60. The method of claim 52, in which the workpiece includes an air-bearing surface of an electronic device, the air-bearing surface has an edge, and the first and second apertured outputs are applied in proximity to the edge of the air-bearing surface to round the edge.

61. The method of claim 52, in which each of the first and second spot areas has a spatial major axis of about 5-15 μm.

62. The method of claim 52, further comprising delivering the first and second Gaussian laser outputs at repetition rates of greater than about 5 kHz.

63. The method of claim 52, in which the surface of target material comprises AlTiC or vacuum-deposited alumina.

64. The method of claim 52, in which the surface of target material comprises silicon, silicon carbide, or titanium carbide.

65. The method of claim 52, in which the target material forms a layer of a laser diode, an optical waveguide, or a MEMS component.

66. The method of claim 52, in which the beam-shaping component comprises a diffractive optical element.

67. The method of claim 52, in which the beam-shaping component comprises aspheric optics.

68. The method of claim 52, in which the first and second apertured outputs have a UV wavelength.