A wafer polishing apparatus includes a wafer polishing assembly having a plurality of wafer carriers for substantially simultaneously polishing a plurality of wafers against a rotating polishing surface. A plurality of wafers to be polished are substantially simultaneously loaded into the plurality of wafer carriers by wafer holding apparatus of an index table. Similarly, a plurality of wafer carriers are substantially simultaneously unloaded into wafer holding apparatus of the index table. The wafer carriers are individually computer controlled for exact polishing and different polishing requirements can be met at the same time by different wafer carriers.
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0. 35. An apparatus for processing a thin wafer of material, comprising:
first and second stations for performing operations on said wafer; and computer means for carrying out a plurality of processes; wherein said computer means is coupled to said first and said second stations to control operations of said first and said second stations and to detect conditions associated with said first and said second stations, and wherein said computer means starts a new process in response to the detecting of a condition while conducting a second process.
0. 38. A control system for controlling a wafer processing system including at least a first station and a second station, comprising:
a memory for storing data associated with a plurality of processes; and a processor coupled to said memory; wherein said processor is configured for executing a first process and a second process of said plurality of processes, said first process being configured to control an operation of said first station, said first process having a condition; and wherein said processor is further configured to reset said first process when said condition in said first process is met while continuing to execute said second process.
0. 29. The apparatus for processing a thin wafer of material, comprising:
storage means for storing a plurality of input variables associated with a plurality of processes, wherein a first process of said plurality of processes is configured to control an operation at a first station and a second process of said plurality of processes is configured to control an operation at a second station; computer means for controlling said plurality of processes and for executing and for resetting said first process and for executing said second process, based upon at least some of said input variables; coupling means for coupling said storage means to said computer means; and condition indicating means coupled to said computer means for indicating to said computer means when a condition in said first process is met; wherein said computer means is responsive to an indication of a condition by said condition indicating means so as to reset said first process while continuing to execute said second process.
0. 47. A method for processing a thin wafer of material, comprising the steps of:
(a) providing a wafer processing system comprising a first station and a second station for performing operations on a wafer, and a control system including a memory and a processor, said control system configured for executing a plurality of processes so as to control said wafer processing system; (b) executing a first process of said plurality of processes, said first process configured for controlling an operation at said first station; (c) executing, a second process of said plurality of processes, said second process configured for controlling an operation at said second station, wherein said second process executes at least partly simultaneously with said first process; (d) during the execution of said first process, monitoring said first process for an occurrence of a condition; and (e) upon the occurrence of said condition in said first process, resetting said first process while continuing to execute said second process.
1. computer controlled apparatus for polishing a surface of a thin wafer material comprising:
a rotating polishing surface; means for measuring the rotation rate of said polishing surface; a wafer carrier for securing a thin wafer of material to a surface thereof; air cylinder means for pressing a wafer secured to said wafer carrier against said polishing surface; pressure sensing means for measuring the pressure applied by said wafer carrier to said polishing surface; means for rotating said wafer carrier while said wafer of material is being pressed against said polishing surface; means for measuring the rotation rate of said carrier; means for establishing ranges of wafer carrier pressure, polishing table rotation rate and wafer carrier rotation rate; and computer means responsive to said pressure sensing means, said means for sensing the polishing surface rotation rate and said means for sensing wafer carrier rotation rate for substantially continuously maintaining the pressure, polishing surface rotation rate and wafer carrier rotation rate within the ranges established by the means for establishing.
0. 48. computer controlled apparatus for polishing a surface of a thin wafer of material, comprising:
a moving polishing surface; means for measuring the rate of movement of said polishing surface; a wafer carrier for securing a thin wafer of material to a surface thereof; air cylinder means for pressing a wafer secured to said wafer carrier against said polishing surface; pressure sensing means for measuring the pressure applied by said wafer carrier to said polishing surface; means for rotating said wafer carrier while said wafer of material is being pressed against said polishing surface; means for measuring the rotation rate of said carrier; means for establishing ranges of wafer carrier pressure, polishing surface movement rate and wafer carrier rotation rate; and computer means responsive to said pressure sensing means, said means for sensing the polishing surface movement rate and said means for sensing wafer carrier rotation rate for substantially continuously maintaining the pressure, the polishing surface movement rate and the wafer carrier rotation rate within the ranges established by the means for establishing.
0. 43. A method for polishing a surface of a thin wafer of material, the steps comprising:
(a) providing a rotating polishing surface, a wafer carrier for securing a thin wafer of material to a surface thereof, and a computer for controlling the operation of said polishing surface and said wafer carrier; (b) establishing ranges of polishing surface rotation rate, wafer carrier rotation rate and wafer polishing pressure; (c) rotating said polishing surface at a rotation rate within the range established in step (b), and monitoring and adjusting the rotation rate of said polishing surface so that the rotation rate is maintained within the established range; (d) rotating said wafer carrier at a rotation rate within the range established in step (b), and monitoring and adjusting the rotation rate of said wafer carrier so that the rotation rate of said wafer carrier is maintained within the established range; and (e) using said wafer carrier, pressing said wafer against said polishing surface with a pressure that is within the wafer polishing pressure range established in step (b), and monitoring and adjusting the pressure applied to said wafer against said polishing surface so that the pressure is maintained within the established wafer polishing pressure range.
0. 16. A computer controlled apparatus for polishing a surface of a thin wafer material, comprising:
a rotating polishing surface; surface rotation sensing means for measuring the rotation rate of said polishing surface; a plurality of wafer carriers, wherein each of said wafer carriers is configured for securing a thin wafer of material to a surface thereof; air cylinder means for pressing the wafers secured to each of said wafer carriers against said polishing surface; pressure sensing means for measuring a pressure applied by each of said wafer carriers to said polishing surface; wafer carrier rotation means for rotating each of said wafer carriers while said wafers are being pressed against said polishing surface; wafer carrier rotation sensing means for measuring the rotation rate of each of said wafer carriers; means for establishing ranges of polishing table rotation rate, and wafer carrier pressure and rotation rate for each of said wafer carriers; and computer means responsive to said pressure sensing means, said surface rotation sensing means and said wafer carrier rotation sensing means for substantially continuously maintaining the polishing surface rotation rate, and the wafer carrier pressure and rotation rate for each of said wafer carriers within the ranges established by the means for establishing.
0. 45. A method for polishing a respective surface of each of a plurality of thin wafers, comprising the steps of:
(a) providing a rotating polishing surface, a plurality of wafer carriers, wherein each of said wafer carriers is configured to secure one of said wafers to a surface thereof, and a computer for controlling the operation of said polishing surface and said plurality of wafer carriers; (b) establishing ranges of polishing surface rotation rate, and wafer polishing pressure and wafer carrier rotation rate for each one of said plurality of wafer carriers, wherein said wafer polishing pressure ranges and said wafer carrier rotation rate ranges may differ for each one of said wafer carriers; (c) rotating said polishing surface at a rotation rate within the range established in step (b) and monitoring and adjusting the rotation rate of said polishing surface so that the rotation rate is maintained within the established range; (d) rotating each one of said plurality of wafer carriers at a rotation rate within the ranges established in step (b), and monitoring and adjusting the rotation rate of each one of said plurality of wafer carriers so that the rotation rate of each one of said plurality of wafer carriers is maintained within the established ranges; and (e) using each one of said plurality of wafer carriers, pressing each one of said plurality of wafers secured to each one of said plurality of wafer carriers against said polishing surface with a pressure that is within the wafer polishing pressure ranges established in step (b) for each one of said plurality of wafer carriers, and monitoring and adjusting the pressures applied to each one of said wafers against said polishing surface so that the pressures are maintained within the established wafer polishing pressure ranges.
2. Apparatus in accordance with
3. Apparatus in accordance with
oscillation measurement means for measuring the distance and rate of such wafer carrier oscillation; and said computer means comprises means responsive to said oscillation measurement means for maintaining said wafer carrier oscillation within predetermined ranges.
0. 4. The apparatus in accordance with
0. 5. The apparatus in accordance with
0. 6. The apparatus in accordance with
a load station for loading and securing the wafer to the surface of the wafer carrier prior to polishing the wafer, and an unload station for subsequently unloading the wafer from the wafer carrier after the wafer has been polished; a polishing station which includes the rotating polishing surface, for polishing the surface of the workpiece; and an airflow system for keeping particles that may exist in said polishing station from entering said load and unload station, so that said load and unload station is maintained at a cleaner clean room environment class than said polishing station.
0. 7. The apparatus in accordance with
0. 8. The apparatus in accordance with
0. 9. The apparatus in accordance with
0. 10. The apparatus in accordance with
0. 11. The apparatus in accordance with
0. 12. The apparatus in accordance with
0. 13. The apparatus in accordance with
0. 14. The apparatus in accordance with
0. 15. The apparatus in accordance with
0. 17. The apparatus in accordance with
0. 18. The apparatus in accordance with
0. 19. The apparatus in accordance with
0. 20. The apparatus in accordance with
a load station for loading and securing the wafer to the surface of the wafer carrier prior to polishing the wafer, and an unload station for subsequently unloading the wafer from the wafer carrier after the wafer has been polished; a polishing station, which includes the rotating polishing surface, for polishing the surface of the workpiece; and an airflow system for keeping particles that may exist in said polishing station from entering said load and unload station, so that said load and unload station is maintained at a cleaner clean room environment class than said polishing station.
0. 21. The apparatus in accordance with
0. 22. The apparatus in accordance with
oscillating means for oscillating each of said wafer carriers on said polishing surface; oscillation measurement means for measuring the distance and rate of each of said wafer carriers oscillation; and said computer means further comprising means responsive to said oscillation measurement means for maintaining the oscillation of each of said wafer carriers within predetermined ranges.
0. 23. The apparatus in accordance with
0. 24. The apparatus in accordance with
0. 25. The apparatus in accordance with
0. 26. The apparatus in accordance with
0. 27. The apparatus in accordance with
0. 28. The apparatus in accordance with
0. 30. The apparatus as recited in
0. 31. The apparatus as recited in
0. 32. The apparatus as recited in
start-up; input; load; unload; polish; and cleaning workpieces.
0. 33. The apparatus as recited in
0. 34. The apparatus as recited in
0. 36. The apparatus as recited in
0. 37. The apparatus as recited in
0. 39. The apparatus as recited in
0. 40. The control system as recited in
0. 41. The apparatus as recited in
start-up; input; load; unload; polish; and cleaning workpieces.
0. 42. The apparatus as recited in
0. 44. The method as recited in
(f) establishing ranges of oscillation distance and rate for said wafer carrier on said polishing surface; and (g) oscillating said wafer carrier a distance and at a rate within the ranges established in step (b), and monitoring and adjusting the oscillation distance and rate of said wafer carrier so that they are maintained within the established ranges.
0. 46. The method as recited in
(f) establishing ranges of oscillation distance and rate for each one of said wafer carriers on said polishing surface, wherein said oscillation distance and rate ranges may differ for each one of said wafer carriers; and (g) oscillating each one of said wafer carriers a distance and at a rate within the ranges established in step (b), and monitoring and adjusting the oscillation distance and rate of each one of said wafer carriers so that they are maintained within the established ranges.
0. 49. The apparatus in accordance with
0. 50. The apparatus in accordance with
0. 51. The apparatus in accordance with
0. 52. The apparatus in accordance with
a load station for loading and securing the wafer to the surface of the wafer carrier prior to polishing the wafer, and an unload station for subsequently unloading the wafer from the wafer carrier after the wafer has been polished; a polishing sation, which includes the rotating polishing surface, for polishing the surface of the workpiece; and an airflow system for keeping particles that may exist in said polishing station from entering said load and unload station, so that said load and unload station is maintained at a cleaner clean room environment class.
0. 53. The apparatus in accordance with
0. 54. The apparatus in accordance with
0. 55. The apparatus in accordance with
0. 56. The apparatus in accordance with
0. 57. The apparatus in accordance with
0. 58. The apparatus in accordance with
means for oscillating said wafer carrier on said polishing surface; oscillation measurement means for measuring the distance and rate of such wafer carrier oscillation; and said computer means comprises means responsive to said oscillation measurement means for maintaining said wafer carrier oscillation within predetermined ranges.
0. 59. The apparatus in accordance with
0. 60. The apparatus in accordance with
0. 61. The apparatus in accordance with
0. 62. The apparatus in accordance with
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This is a division of application Ser. No. 07/898,876, filed Jun. 15, 1992, now U.S. Pat. No. 5,329,732.
This invention relates to polishing methods and apparatus and more particularly, to such methods and apparatus for accurately polishing wafers of semiconductor material with high throughput and in a manner compatible with semiconductor processing clean room environments.
The production of integrated circuits begins with the creation of high quality semiconductor wafers. Each wafer is of relatively high cost due to the detailed processing needed to produce it. During the integrated circuit production process, an extremely flat surface is desired on at least one face of the wafer. Wafer polishing to achieve such a flat surface is a known technique.
Such polishing generally includes attaching one side of the wafer to a flat surface of a wafer carrier or chuck and pressing the wafer against a flat polishing surface. The polishing surface is moved under the wafer, and the wafer may also be rotated about its vertical axis and oscillated back and forth to improve polishing action. The polishing surface is generally a pad attached to a rigid flat table which is rotated to provide movement and onto which an abrasive and/or chemical slurry is pumped. The joint functions of the pad, the slurry, and the relative movements of the components produces a combined mechanical and chemical process at the wafer surface which produces a highly flat surface on a wafer where surface variations are kept to less than, for example, 0.5 μm.
Polishing has typically been performed prior to integrated circuit fabrication so that a flat surface is available on the semiconductor wafer on which the circuit fabrication can take place. As integrated circuits increase in complexity, the conductive line widths have reduced considerably, making the focus and depth of field of the imaging process more sensitive to surface variations on the substrate. This has increased the desire for wafers with improved surfaces. Further during the integrated circuit fabrication process, layers of, for example, conductors and dielectrics, are built up on the wafer, on top of which other such layers are to be created. Thus, it has become necessary to "re-flatten" the wafer surface during the actual fabrication of the integrated circuit and not merely before it. The act of re-flattening is referred to as planarization. At each successive one of several planarization operations the wafer is considerably more valuable. Given semiconductor processing costs, it is quite possible that a single 8" partially processed wafer is worth $10,000 or more when planarization is performed. Great care in handling of each such wafer is obviously required.
Speed of wafer polishing has always been of interest but has become more important when planarization is one of the necessary sequential processing steps. Prior arrangements, typically, polish one or two wafers, with substantial waiting time to load and unload wafers. Methods and apparatus are needed to speed up the polisher process.
The increase in value of the wafers being polished has greatly increased the need for precision in the planarization process. Improper polishing of a wafer worth $100 is a completely different matter than improperly polishing one worth $10,000. Methods and apparatus are needed to provide improved polishing, particularly in a rapid production environment.
These needs are met by the present invention.
Wafer polishing apparatus in accordance with the present invention comprises a polishing assembly having a plurality of wafer carriers for substantially simultaneously engaging a plurality of wafers of material with a polishing surface. The apparatus includes an index table for holding wafers to be polished, and positioning apparatus to move the polishing assembly between the polishing surface and the index table. At the index table, all wafer carriers of the polishing assembly are substantially simultaneously loaded with wafers. After loading the carriers, the polishing assembly is positioned in polishing engagement with the polishing surface. By incorporating an index table into the apparatus, unpolished wafers can be loaded onto the index table in preparation for loading them simultaneously onto the wafer carriers, providing throughput advantages.
The index table indexed in increments when being loaded with unpolished wafers so that the wafers can be placed thereon one at a time, as retrieved from a multi-wafer cassette. The movement of unpolished wafers to the load cups advantageously occurs while the polishing assembly is at a polish position polishing another plurality of wafers. Upon completion of polishing, the assembly returns to the index table to receive substantially simultaneously another set of wafers to be polished.
The index table may also comprise a plurality of unload cups which are used in a similar manner to the load cups to substantially simultaneously removed polished wafers from the wafer carriers after being polished. The removal of polished wafers from the unload cups can then be performed while other wafers are being polished by the polishing assembly.
The alignment of polish assembly, index table and polishing surface is maintained by providing a stable framework in the apparatus. To this end, a linear track for moving the polishing assembly extends between the polishing surface and the index table. The linear track provides a stable, rugged frame while permitting controlled movement of the polishing assembly between the index table and the polishing surface.
The apparatus may also include an automatic arrangement for washing each wafer as it is removed from the index table. Such washing assures that the polished wafers removed from the apparatus are suitable for a clean room environment.
The apparatus is controlled by a computer which processes many separate feedback loops to maintain the accuracy of operations. For example, polishing pressure is applied at each wafer carrier by an air cylinder and applied pressure is sensed by a pressure sensor of each wafer carrier. Oscillation and rotation of each wafer carrier is provided by separate servo motors, the position and rotation rate of which is also sensed. Ranges of values for desired pressure and wafer carrier motion are established based on operator input. The computer then reads actual operating parameters measured by the sensors and adjusts the air pressure and servo motor motion to keep the actual parameters within the desired ranges.
The operator enters data indicative of operating parameters for each of the wafer carriers being used. These parameters then form the basis of the desired ranges which are separately stored in the computer. Advantageously, the operator can establish the same or different parameters for each wafer carrier. Since each wafer carrier is controlled by the computer in accordance with variables stored for that wafer carrier, the apparatus can differently process wafers on separate wafer carriers.
Each wafer carrier of the preferred embodiment includes an upper force conveying member having a central axis for conveying pressure forces along the central axis and rotational forces about that central axis. A polishing member of the wafer carrier comprises a flat lower surface having a polishing axis. Pressure forces are coupled between the force conveying member and the polishing member by a force coupling member including a first race member symmetrically disposed about the central axis of the force conveying member, a second race member symmetrically disposed about the polishing axis of the wafer carrier, and ball bearings held between the first and second race members. The first race member, the ball bearings, and the second race member cooperate to focus pressure forces through the force coupling member to a point on the polishing axis. Further, rotational forces are conveyed by a plurality of cam followers disposed about the periphery of the force conveying member which abut bearing surfaces on the polishing member, to couple rotational forces. After the force conveying member is inserted into a cylindrical opening in the polishing member, it is held in place resiliently by a collar which includes a plurality of springs for holding the force conveying member in the cylindrical opening of the polishing member, to maintain pressure on the ball bearings.
A lower flat surface of the polishing member includes a plurality of holes therethrough which communicate with a central passage into the force conveying member. This hollow passage is sealed by flexible means to permit relative motion of the polishing member and the force conveying member, while providing a substantially fluid-tight communication channel.
The polishing member also includes a lip around its polishing surface to provide additional support for wafers carried thereby. In the preferred embodiment, the lip comprises a ring of material having threads on an inner surface thereof, which engage with threads around the outer surface of the polishing member. The height of the resulting lip can be carefully adjusted by controlling the depth to which the threads of the ring and the polishing member are engaged. Advantageously, a collar is applied over the ring, which collar frictionally engages the ring to keep it from rotating and becoming misadjusted.
In the Figures of the drawing, like reference numerals identify like components, and in the drawing:
Processing module 102 includes an index table 117 which is used to receive wafers from, and provide wafers to, input/output unit 101. Index table 117 comprises a rotatable annular ring 118 including five wafer unload cups numbered 119 through 123 and five wafer load cups numbered 124 through 128. Unload cups 119 through 123 are disposed at 72°C increments about the vertical center axis of index table 117, and load cups 124 through 128 are similarly disposed at 72°C increments about the vertical axis in alternating positions with the unload cups. Thus, a wafer cup is present at 36°C increments about the rotatable member 118, and the load and unload cups are alternatingly disposed.
Index table 117 can be rotated through 360°C, and is primarily rotated in integer multiples of 36°C in the counterclockwise direction (
When a wafer has been aligned by aligner 113, and an empty load cup 124, is present at input position 129, input gripper 115 grips the aligned wafer and rotates it vertically 180°C to place the newly aligned wafer in input cup 124, as shown in FIG. 4. After cup 124 has received a wafer, the index table 117 is rotated by 72°C counterclockwise under the control of an index drive system 130 driven by AC servo motor 131 (
In the present embodiment, wafers are polished five at a time by a multi-head wafer polish assembly operating in conjunction with a rotating polishing table 134. The multi-head polish assembly 132 is shown in cut-away view in FIG. 1 and is represented in
When index table load cups 124 through 128 each contain a wafer to be polished, those wafers must be transferred to the wafer carriers 139 through 143 before polishing can begin. The loading of wafers into wafer carriers 139-143 begins with the movement of polish assembly 132 from a position over the polish table 134 to a position over the index tale 117. As shown in
In the present description, we will assume that wafer carriers 139 through 143 have just completed a polish operation and each contains a wafer to be unloaded.
The wafer carrier load operation with respect to an exemplary wafer carrier 139 is illustrated in
After polished wafers have been placed in unload cups 119-123 and unpolished wafers have been loaded into wafer carriers 139 through 143, the wafer polish assembly 132 is moved along rails 137 to a position over rotary polish table 134.
Wafer polishing is accomplished by the combined action of the wafer carriers 139-143 of polish assembly 132, and the motion of polishing table 134 operating in the presence of an abrasive and/or chemical slurry.
Table 134 comprises a disc-shaped upper surface 286, which is carried by a support frame 288, for supporting the upper surface 286 and defining at least one cooling fluid chamber 293. Shaft 282 has a hollow channel 291 along its central axis and includes a tube 290 disposed therein to define two fluid channels. One fluid channel is within tube 290 and the second is in the annular spacing between tube 290 and the inner surface of channel 291 during operation. Cooling fluid is pumped via central tube 290 and a fitting 297 into channel 293. Warmed water from channel 293 flows through the annular channel around tube 290 and is returned to a heat exchanger 295 (
The polishing assembly 132 shown in plan view of
An oscillating polish arm 180 is shown in detail in FIG. 10. Polish arm 180 comprises a vertical pivot column 181 to which is welded an upper horizontal support member 182 and a lower horizontal support I-beam 183. The free ends of member 182 and I-beam 183 are connected by an end member 184. The upper end of pivot column 181 is bolted to the rotating surface of a rotational speed reducer 186, which extends through an aperture in upper plate 170. In the present embodiment, speed reducer 186 is a Dojen speed reducer Series II, Model Number 04. The stationary portion of speed reducer 186 is bolted to the upper surface of plate 170. The lower end of pivot column 181 is supported by a bearing 187 and bearing support pin 188 attached to the lower plate 172 of housing 132. An AC servo motor 190 is connected to and drives speed reducer 186. By selectively energizing servo motor 190 to rotate clockwise or counterclockwise, the oscillation of the polish arm 180 about the vertical axis defined by column 181 is readily controlled.
The polish arm 180 supports the apparatus which controls the function of one wafer carrier, e.g. 139. The raising, lowering and downward forces on the wafer carrier are controlled by a double acting air cylinder 192 which is attached to the upper surface of polish arm upper member 182. Air cylinder 192, which may, for example, be a SMC Series NCA1 extends through an arcuate slot 195 formed in upper plate 170 so that free oscillation of arm 180 is not prevented. An output shaft 194 of air cylinder 192 is attached to a circular flange 196, which is connected to a cup-shaped member 197. Cup-shaped member 197 receives a bearing collar 198 through a circular aperture 199 in the cup-shaped member. The union of flange 196 and cup-shaped member 197 form a cylindrical chamber having larger dimensions than the flanged top portion of bearing collar 198, so that no transverse forces are conveyed from beneath the bearing collar 198 to the air cylinder 192. A bottom surface of bearing collar 198 is attached to a top surface of a force sensor 202 such as a Sensetel Model 41 loadcell, the bottom surface of which is attached to a hollow cylindrical force-conveying member 204. Force conveying member 204, which is connected at a bottom surface thereof to the periphery of a hollow carrier driving shaft 206 by a thrust bearing 208. Internal to hollow force-carrying member 204 is a fluid coupling 210 which, via an aperture 209 in force-conveying member 204, communicates fluids and vacuum to the hollow center of carrier driving shaft 206 via a fluid connection 211.
Carrier driving shaft 206 is supported at I-beam 183 by a ball spline and bearing assembly at 212, which holds shaft 206 from lateral movement but which permits upward and downward movement as well as rotation of the shaft. Assembly 212 comprises a ball spline collar 214, such as THK LBST50, which is held in place by a bearing 216, such as Torrington 9120K. The bottom end of driving shaft 206 is attached to a circular flange 218, which extends through an arcuate slot 219 in the bottom of plate 172 of assembly 132. Arcuate slot 219 is substantially identical to arcuate slot 195 and is present to permit oscillation of shaft 206 and carrier 139. The top of ball spline 214 is connected to a gear 224, which is rotationally driven by a gear 226 attached to an output shaft 227 of a speed reducer 222. An AC servo motor 220 provides rotational forces to speed reducer 222 and thus to shaft 206 under the control of computer 103.
Downward pressure forces are conveyed by a ball bearing assembly including a plurality of ball bearings 258, supported by a lower race 255 and retained by a retainer 257. As shown in
Rotational forces are coupled from upper member 251 to lower member 253 by four cam followers 263, which are attached to 90°C spacing around the cylindrical periphery of upper member 251. The outer rings of cam followers 263 are disposed in slots 265 (
Lower member 253 is produced in two sections so that fluid and vacuum can be communicated therethrough to surface 261. An upper section 271 of the lower member 253 has a plurality of channels 273 milled therein which communicate with a central aperture 272. The surface-defining lower section 274 of lower member 253 includes a plurality of holes 275 drilled therethrough for communication of fluids and vacuum between surface 261 and the milled channels 273. A cavity 274 is formed between the upper member 251 and flange 218, which cavity is sealed at its lower surface by a flexible gasket 276. Any fluid or vacuum which is communicated in the hollow center of drive member 206 is passed via cavity 274 to the holes in surface 261 by a channel 277, aperture 272, milled channels 273 and the holes 275 through surface member 274. The wafer carrier 139 also includes a hollow cylindrical ring 268 of plastic material, such as Delrin, which is disposed over surface member 274 to form an outer lip 270 for surface 261. The lip 270 is used to hold an attached wafer from sliding on surface 261, and the optimum height of lip 270 varies depending on the wafer thickness and other process variables. As shown in
When the polish assembly 132 is at the polish table 134, the wafer output process of moving polished wafers from unload cups 119-123 of index table 117 into an output wafer cassette, e.g. 108, can take place. The wafer output process begins by placing index table 117 in a position in which unload cup 120 is in the output position 131. The output process begins when the wafer cup 117 at the output position is raised by an air cylinder 160 and unload gripper 116 edge grips the wafer 235 in unload cup 120, rotates it vertically and places it in water cleaning apparatus 230. Water cleaning apparatus 230 is shown in detail in side view FIG. 11 and top view FIG. 12. The unloaded wafer 235 is placed by gripper 116 on four spindles 232, each having a ball bearing mounted cap 233. The spindles 232 and caps 233 are positioned to support the perimeter of output wafer 235 on a ledge 236 of all four caps. A wash assembly 237 including six revolving brushes 238 is then driven to the right toward wafer 235 along guide shafts 240 to a position above and below the wafer. Upon such positioning, a bottom brush-carrying portion 241 of wash assembly 237 is moved upwardly by an air cylinder 239 to engage wafer 235 between the upper and lower sets of brushes 238. The brushes are then rotated by stepper motors 247 and 246 and belts (not shown), while deionized water is applied by a plurality of nozzles 243 in upper member 244 of wash assembly 237 and by a plurality of nozzles 245 mounted under the wafer 235. The asymmetrical placement of brushes 238 rotates the wafer 235 in the water, thereby cleaning its surface. After a preset time for completion of cleaning, washer assembly 237 is returned to its leftmost position and wafer 235 is raised by an elevator/arm apparatus 249 to a position above the water cleaning assembly 230. Elevator/arm assembly 249 is then moved along guide member 248 to a water slide 250 (FIG. 1), where the wafer 235 is released to slide by water flow into output wafer cassette 108. Advantageously, the wafer cassette 108 is kept submerged in water until being removed by an operator.
The method and apparatus described herein is controlled by the computer 103, which includes an INTEL 486 main processor, memory, and suitable input/output interfaces for controlling and sensing production processes. The computer assembly, which may be a VME Bus System, and its interface to production processes, are well known in the art and are not described in detail herein. Also, each of the servo and stepper motors described includes an associated position and/or rate sensor which is used by the computer 103 in closed loop feedback control of the rotation and position of the motor. Such position and rate sensors are also well known in the art. Further, although the computer 103 is capable of communicating with a process control master computer (not shown) which may be in control of an entire wafer production process, such master computer or communication is not needed for the present method and apparatus and is therefore not described herein.
The process begins with the start-up routine (
In the present embodiment, a video monitor 105 (
After the process variables have been established and stored, step 305 is performed in which all five carriers 139 through 143 are raised, oscillated to the home position, and moved to the polish position. Step 305 is performed by transmitting commands via air pressure control 401, to control all five air cylinders 192 to raise their connected wafer carrier 139 through 143. Completion of raising is checked by reading five Hall effect limit detectors 407 via an interface 408. Oscillation to the home position is achieved by oscillation commands sent to oscillator servo interface 403, which applies power to the servo motors 190 to rotate the carriers to the home position. Proper oscillation is then checked by reading servo position sensors 409 of motors 190 (one associated with each servo motor 190) via interface 410. Next, a step 306 is performed in which polish table motor 280 is sent a command via interface 442 to achieve the rotation speed set in the process variables. Computer 103 periodically reads the output of a rate sensor 440 of motor 280 via an interface 441 to adjust the actual rotation speed of polish table 134. Finally, the position of polish assembly 132 is read from a position sensor 415 associated with servo motor 165 and, if the assembly is not in polish position, commands are sent to the servo motor 165 via an interface 417 to so move the assembly.
After placing the system 100 in a known condition, a step 307 is performed to determine if an input cassette 108 has been loaded into an input/output unit 101. Such a check may comprise reading by computer 103 a photoelectric cell sensor 119 in input/output unit 101. When no cassette is present, an alarm or other notice may be provided to stimulate action by the operator. Alternatively, when such cassette is present, the process enters the input routine (
Upon proper alignment, a step 313 is performed in which the load cup 124, at the input position 129 is raised, and the input gripper 115 is commanded in step 315 to place the aligned wafer in the load cup. The load cup 124 is then lowered in a step 317 and servo motor 131 is commanded in step 318 to index by 72°C. After indexing, a check 319 is performed to determine if a computer 103-maintained count of wafers shows that five have been placed on index table 117. When fewer than five have been so placed, and the wafer input routine begins again at step 311.
When all five load cups 124 through 128 contain wafers for polishing, the wafer load routine (
After the carriers 139 through 143 are positioned over the index table 117, they are scrubbed in step 325 by being lowered and rotated against brush 146, while being sprayed with wafer from nozzles 147. The control of water spraying is represented in
The position of the load cups 124 through 128 is checked in a step 328 to establish that load cup 124 is present in the input position 129, and if an unload cup is in that position, the table is indexed by 36°C. When the load cups 124 through 128 are properly positioned, the load cups are raised in a step 329 by commands from computer 103 to an air cylinder controller 431 via an interface 430. A plurality of Hall effect sensors 432 are read by computer 103 to establish that proper air cylinder operation has occurred. The cups self-align with the carriers upon being raised, and computer 103 commands a vacuum control interface 434 to control five fluid valves 435, to apply vacuum from source 438 to the surfaces 261 of the carriers 139 through 143 via hoses to the fluid coupling input 211 (FIG. 10). The applied vacuum secures the wafers to the carriers 139 through 143 and the load cups are lowered to index table 117 in a step 333. Advantageously, vacuum level checks are performed by vacuum sensors 436 to assure that a wafer is present on each carrier 139 through 143 before the process continues. The state of sensors 436 is read by computer 103 via an interface 437. The wafer carriers 139 through 143 are then oscillated to the home position in step 335, and the servo motor 165 is commanded to move the polish assembly 132 to the polish position in a step 337.
Upon arrival at the polish position, the polish assembly is locked into position by a command to clamp control unit 425 and the polish routine (
In step 341, the polish table rotation speed is checked by reading rate sensor 440 via an interface 441 and the rotation rate is adjusted by commands to polish table motor 280 via interface 442. At this point, commands are sent via interface 405 (step 343) to servo motors 220 to begin their rotation at the rate specified by the operator in the input variables. Also, the carriers 139 through 143 are lowered and pressed against the revolving polish table 134 at the specified pressure, and the oscillation distance and speed of carriers 139 through 143 are maintained. Advantageously, pressure sensors 202, position sensors 409, and the rotation sensors 412 are frequently read by computer 103 during polishing, and appropriate adjustment commands are transmitted to carefully maintain all movements and forces within the ranges established for the levels specified by the operator in the input variables. Also, the slurry amount pumped onto polish table 134 is communicated to a slurry interface and the temperature of the polish table is controlled by computer 103 communication with heat exchanger 295 to maintain accurate polishing.
A timing step 349 begins to run when polishing begins and the wafer carriers 139 through 143 are raised (step 351) and their motion stopped when the time variable specified by the operator is achieved. If unload cups are then available, as is determined in step 353, the process flow proceeds to the unload routine (
In step 355, the polish assembly 132 is moved to the index table position, the carriers are lowered and scrubbed in a step 357, and are raised and oscillated to their maximum outward position in a step 359. In step 361, the position of index table 117 is sensed by computer 103 and, if necessary, the table is rotated so that unload cup 120 is in the input position 129. When the unload cups are in proper position, they are raised in step 363 to align with carriers 139 through 143 and vacuum control 434 is commanded to stop the vacuum at surfaces 261 to allow the wafers to drop into their respective unload cups. In actuality, it may be found necessary to also apply a fluid, such as water, at pressure, to the vacuum system to force the wafers from their respective surfaces 261. Such fluid introduction to the system is performed by computer 103 control of fluid valves 435, which are shown connected to a vacuum source 434 and to a pressurized water source 439 in FIG. 15.
When the wafers have dropped into unload cups 119 through 123, they are lowered to the surface of the index table 117 in step 367. Carriers 139 through 143 are then oscillated to the home position (step 369), lowered and scrubbed (step 371), and raised (step 373). A step 375 is then performed to determine if unpolished wafers are present in the load cups 124-128. When wafers are present in the load cups, load routine (FIG. 19), beginning at step 327 is performed.
When the polish assembly 132 has returned to the polish table, either with or without wafers for polishing, and polished wafers are present in the unload cups 119-123, the wafer output routine (
While preferred embodiments of the invention have been illustrated, it will be obvious to those skilled in the art that various modifications and changes may be made thereto without departing from the scope of the invention as set forth in the attached claims.
For example, in the described embodiment five wafers are loaded, unloaded and polished at a time, in accordance with the same operator-entered process variables. The process variables for each polish arm may be different when they are entered. Also, for certain small batch processes or for testing purposes, fewer than five wafers may be a polished at a time. During the data entry phase some, e.g. 2, polish arms may be identified as idle and only three wafers rather than five will be placed on the index table, loaded, polished and unloaded.
Nagahashi, Isao, Karlsrud, Chris E., Van Woerkom, Anthony G., Odagiri, Shigeru
Patent | Priority | Assignee | Title |
12119246, | Oct 30 2020 | Ebara Corporation | Method, device, and non-transitory computer readable medium for determining timing of removing substrate from cassette in substrate processing device, and substrate processing device |
6634930, | Aug 09 2000 | Taiwan Semiconductor Manufacturing Co. LTD | Method and apparatus for preventing metal corrosion during chemical mechanical polishing |
6846224, | Jul 16 2002 | Samsung Electronics Co., Ltd. | Surface planarization equipment for use in the manufacturing of semiconductor devices |
6875076, | Jun 17 2002 | Accretech USA, Inc. | Polishing machine and method |
8657648, | Oct 12 2010 | Disco Corporation | Processing apparatus having four processing units |
Patent | Priority | Assignee | Title |
3128580, | |||
4141180, | Sep 21 1977 | SpeedFam-IPEC Corporation | Polishing apparatus |
4194324, | Jan 16 1978 | CYBEQ NANO TECHNOLOGIES, INC | Semiconductor wafer polishing machine and wafer carrier therefor |
4502252, | Mar 29 1982 | Tokyo Shibaura Denki Kabushiki Kaisha | Lapping machine |
4680893, | Sep 23 1985 | Freescale Semiconductor, Inc | Apparatus for polishing semiconductor wafers |
4873792, | Jun 01 1988 | Illinois Tool Works, Inc | Polishing apparatus |
4887221, | Sep 25 1987 | Sunnen Products Company | Computer controlled honing machine using look up table data for automatic programming |
4918870, | May 16 1986 | Ebara Corporation | Floating subcarriers for wafer polishing apparatus |
4956944, | Mar 19 1987 | Canon Kabushiki Kaisha | Polishing apparatus |
4962616, | May 28 1988 | Peter Wolters AG | Method and device for controlling the operation of honing machines |
5035087, | Dec 08 1986 | Sumitomo Electric Industries, Ltd.; Asahi Diamond Industrial Co. Ltd.; NISSEI INDUSTRY CORPORATION | Surface grinding machine |
5081795, | Oct 06 1988 | Shin-Etsu Handotai Company, Ltd. | Polishing apparatus |
5113622, | Mar 24 1989 | Sumitomo Electric Industries, Ltd. | Apparatus for grinding semiconductor wafer |
5136817, | Feb 28 1990 | Nihon Dempa Kogyo Co., Ltd. | Automatic lapping apparatus for piezoelectric materials |
5140774, | Oct 31 1991 | System Seiko Co., Ltd. | Apparatus for polishing hard disk substrates |
5197230, | Jul 31 1989 | Diskus Werke Frankfurt am Main Aktiengesellschaft | Finish-machining machine |
JP42738, | |||
JP136365, | |||
JP223561, | |||
JP227361, | |||
JP241060, | |||
JP5542738, | |||
JP58223561, | |||
JP59227361, | |||
JP610244460, | |||
JP61241060, | |||
JP62162464, | |||
JP62218062, | |||
JP63295165, |
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Sep 14 2007 | SpeedFam-IPEC Corporation | Novellus Systems, Inc | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 019892 | /0207 |
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