Disclosed in is an aligning and exposing method suitable for use in the production of LSIs. Coherent ray beams are applied from two directions to form an interference fringe through interference of the coherent rays. A diffraction grid is disposed in the optic paths of the ray beams substantially in parallel with the interference fringe. The ray beams reflected and or transmitted by the grid are converged by a lens system and the intensities of the ray beams are measured to detect the relative position between the interference fringe formed by two coherent ray beams and the diffraction grid, thereby to permit a highly accurate alignment of fine semiconductor element. The pitch of the grid on the substrate is selected to be n (n being an integer) times as large as the pitch of the interference fringe, so that the grid for alignment purpose is formed simultaneously with the formation of the LSI pattern by photolithographic technic. With this method, it is possible to attain a high degree of accuracy of alignment, and to conduct the subsequent exposure using the same ray beam source as that used for the alignment.
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20. An aligning method comprising: applying coherent ray beams from two directions to form an interference fringe by the mutual interference of the two ray beams; placing a grid in the optic paths of said two ray beams; leading the ray reflected or diffracted transmitted by said grid to a photo-detecting means through a slit to measure the intensity of said ray thereby to detect the relative position between said interference fringe and said grid; and aligning said interference fringe with said grid.
24. An aligning and exposing method comprising: applying coherent first radiant ray beams having a first wavelength from two directions; placing a grid disposed in the optic paths of said first radiant ray beams substantially in parallel with the interference fringe formed by mutual interference of two first radiant ray beams; allowing the ray beams either reflected and or transmitted by said grid to interfere again and leading the interfered ray beam to a photo-detecting means for the measurement of intensity of said the interfered ray beam; aligning said interference fringe of the two first radiant ray beams and said grid thereby to align a pattern formed on the same substrate as said grid; and effecting an exposure with a second radiant ray beam.
9. An aligning method comprising: applying coherent ray beams from two directions to form interferent an interference fringe through interference of said coherent ray beambeams, disposing a grid in the paths of said ray beams substantially in parallel with said interference fringe; allowing the ray beam either reflected and transmitted by said grid to interfere again through an optic system and leading the interfered ray beam to photodetecting means; changing the relative position between the interference fringe of two ray beams and said grid; detecting the amount of change of the relative position; and detecting the position by comparing the intensity of the interfered ray beam measured by said photodetecting means with the amount of change of the relative position.
1. An aligning method comprising: the steps of: applying coherent ray beams from two directions to form an interference fringe through interference of said coherent ray beams; disposing a grid in the paths of said ray beams substantially in parallel with said interference fringe; allowing the ray beams either reflected and or transmitted by said grid to interfere again through an optic system and leading the interfered ray beam to photodetecting means; detecting the relative position positions between said interference fringe of said two ray beams and said grid through measuring the intensity of said interfered ray beam by said photodetecting means; and aligning said interference fringe and said grid with each other in accordance with the result of the measurement.
11. An aligning method comprising: applying coherent ray beams from two directions to form an interference fringe through interference of said coherent rays ray beams, disposing a grid in the paths of said ray beams substantially in parallel with said interference fringe, said having a pitch which is n (n being an integer) times as large as the pitch of said interference fringe; leading the ray beams reflected or transmitted by said grid to photodetecting means; detecting the relative position between said interference fringe of said two ray beams and said grid through measuring the intensity of said ray beam reflected or transmitted by said grid by said photodetecting means; and aligning said grid with said interference fringe in accordance with the result of the measurement.
15. An aligning method comprising: applying a coherent first ray beam into a first one of two substrates to be aligned with each other, said first one of the substrates receiving said first coherent ray beam being provided on its surface with two first diffraction grids; applying second and third ray beams diffracted by the respective diffraction grids into the second one of the substrates; leading a fourth ray beam reflected or transmitted by a second diffraction grid on the surface of said second substrate to a photodetecting means and measuring the intensity of said fourth ray beam by said photodetecting means thereby to detect the relative position between the interference fringe of two ray beams applied to said second substrate and said second diffraction grid on said second substrate; and aligning said first substrate and said second substrate with each other using the detected relative position between said interference fringe and said second diffraction grid.
27. An exposure method comprising: disposing a light-receiving element in the vicinity of a coherent ray beam; preparing an optic system capable of effecting an amplitude splitting of said ray beam and superposing the split ray components to make them interfere with each other; forming an interference fringe in a space by allowing two ray beams formed by the amplitude-splitting to interfere with each other; placing a diffraction grid in the optic paths of said two ray beams substantially in parallel with said interference fringe; returning the ray beams diffracted by said diffraction grid through said optic system; measuring the intensities of the returned ray beams by said light-receiving element; making an adjustment to substantially equalize the pitch of said interference fringe to the pitch of said diffraction grid by making use of the result of the measurement, thereby to align said interference fringe and said grid with each other; and exposing said interference fringe.
18. An aligning method comprising: the steps of: applying a coherent first ray beam into a first one of two substrates to be aligned with each other, said first one of the substrates receiving said first coherent ray beam being provided on its surface with a first diffraction grid; applying a second ray beam diffracted by said first diffraction grid into the second one of the substrates; applying a reference third ray beam interferable with said second ray beam to the second substrate; leading a fourth ray beam, which is formed by reflecting or transmitting said second and third ray beams by a second diffraction grid on said second substrate, to a photodetecting means and measuring the intensity of said fourth ray beam by said photodetecting means thereby to detect the relative position between the interference fringe of said second and third ray beams applied to said second substrate and said second diffraction grid on said second substrate; and aligning said first substrate and said second substrate with each other using the detected relative position between said interference fringe and said second diffraction grid.
28. An exposure method comprising: allowing a coherent ray beam to pass through a diffusion optic system for diffusing said coherent ray beam; disposing a pin hole in the vicinity of the point where said ray beam is constricted by said diffusion optic system; disposing a light-receiving element in the vicinity of the ray beam which has passed through said pin hole; placing an optic system capable of making an amplitude splitting of said ray beam and superposing the ray beams formed by the splitting to make them interfere with each other; forming the an interference fringe in a space by allowing the rays formed by splitting to interfere with each other; disposing a diffraction grid in the optic paths of said ray beams formed by splitting substantially in parallel with said interference fringe; returning the ray beams diffracted by said diffraction grid through said optic system; measuring the intensities of the returned ray beams by said light-receiving element; effecting an adjustment to substantially equalize the pitch of said interference fringe with the pitch of said diffraction grid, aligning said grid with said interference fringe; and effecting an exposure. 29. An aligning method, comprising the steps of applying coherent ray beams from two directions to form an interference fringe through interference of said coherent ray beams; disposing a grid in the paths of said ray beams substantially in parallel with said interference fringe; allowing the ray beams either reflected or transmitted by said grid to interfere again through an optic system and leading the interfered ray beam to photodetecting means; detecting the relative positions between said interference fringe of said two ray beams and said grid in accordance with a change in the output of said photo detecting means; and aligning said interference fringe and said grid with each other in accordance with the result of the measurement. 30. A method of aligning a reticle and a wafer provided with a grid, said grid being set on a wafer which is optically exposed through said reticle so as to be aligned with the latter, comprising the steps of applying coherent ray beams from two directions to form an interference fringe through interference of said coherent ray beams; disposing a grid in the paths of said ray beams substantially in parallel with said interference fringe; allowing the ray beams either reflected or transmitted by said grid to interfere again through an optic system and leading the interfered ray beam to photodetecting means; detecting the relative positions between said interference fringe of said two ray beams and said grid in accordance with a change in the output of said photodetecting means; and aligning said reticle and said wafer with each other in accordance with the result of the measurement.
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The present invention relates to an aligning method which ensures a high precision of alignment and which is suited to the aligning apparatus for producing asymmetryblock blocks on the specimen W. The reflected rays R3 and R4 diffracted by the grid G impinge upon the photodetectors D1 and D2 through the optic systems including lenses L1 and L2.
Representing the wavelength of the laser beam by λ and the pitch of the interference fringe formed by interference of the reflected rays R1 and R2 from the mirrors M1 and M2 by Λ the pitch of the interference fringe formed on the specimen W is expressed by the following formula. ##EQU2##
The grid G having a pitch substantially equal to the pitch λ of the interference fringe produces rays which are obtained through a diffraction of the ray formed by the interference between two ray beams R1 and R2, the diffraction being made by the grid which effects a wave-surface splitting of the ray beam formed by the interference. The rays produced by the wave-surface splitting are converged through the optic systems of the lenses L1 and L2 and are made to interfere with each other. By so doing, it is possible to obtain by photodetectors D1 and D2 a ray intensity which represents the positional relationship between the interference fringe formed by two ray beams and the grid G.
By making use of this ray intensity representing the positional relationship, it is possible to detect the positional relationship between the specimen W and the interference fringe of two ray beams and to correct the position of the specimen W, thereby to attain alignment between the interference fringe of two ray beams and the specimen W.
A z axis is assumed here as being the central axis z--z of optic paths of the reflected ray beam R1 and the transmitted ray R2. The specimen W is held by a fine adjusting mechanism A which can hold the specimen W such that its surface carrying the grid G is substantially perpendicular to the z axis and has functions to effect fine adjustment of position in the x and z axes, as well as in the rotational directions around the axes x, y and z, the rotational angles being represented by α, β and θ. The positional relationship between the interference fringe and the grid G on the specimen W is adjusted by means of the fine adjusting mechanism A.
A symbol B represents a mask having a form as shown in FIG. 35. The mask B is provided with a plurality of windows B1 at the portion thereof corresponding to the position of the grid G so as to pass two ray beams, and at its portion with a plurality of windows B2 at its portion corresponding to the exposure position of the specimen W.
A symbol C denotes an optic path partial intercepter having an intercepting mechanism which is adapted to partially intercept two ray beams such that two ray beams are applied only to the grid portion G when the positional relationship between the aforementioned interference fringe and the specimen W is adjusted, and to intercept two ray beams partially such that the ray beams impinge only upon the specimen W when the exposure is conducted after the alignment.
A symbol DA represents an optic path full intercepter disposed between the laser generator 310 and the reflecting mirror 311 and having an intercepting mechanism adapted to fully intercept the optic path.
The constituents 310, 311, 312, 313, 314, 315, 316, BS, M1, M2 and A are mounted on the same vibration damping base so that they are protected from external vibration. The optic path intercepters C and DA are mounted on a base (not shown) different from the vibration damping base E so that the vibration produced as a result of operation thereof is not transmitted to the vibration damping base E.
The detail of the fine adjustment mechanism A will be described hereinunder with specific reference to FIGS. 36 and 37.
A reference numeral 320 designates a specimen holder having a vacuum sucking hole a for sucking and holding the specimen W having the grid G and a vacuum hole b. The vacuum hole b is connected to a vacuum source which is not shown. The specimen base 320 is provided also with a vacuum sucking groove c for sucking and fixing the mask B and a vacuum port dd which is connected to a vacuum source (not shown). The height of the step between the surface portion of the specimen holder for sucking the specimen W and the surface portion of the same for sucking the mask B is selected to be slightly greater than the thickness t of the specimen W.
An explanation will be made hereinunder as to the adjusting mechanism A0 for adjusting the angle α. The specimen holder 320 is fixed through a belleville spring 322 to a θ rotation mechanism A1 by means of three bolts 321. In order to permit the specimen W to rotate around the x axis by a small angle α, bolts 321 are adapted to be fixed at both ends f and g or the x axis and on one end h on the y axis.
An explanation will be made hereinunder as to the θ rotation mechanism A1. A reference numeral 323 designates a rocker plate connected to the specimen base 320 through the belleville spring 322 by means of bolts 321. The rocker plate 323 is rotatably held by a rotary guide ring 324 so as to be able to rotate smoothly around the z axis. A reference numeral 325 denotes a θ rotation mechanism base for fixing the rotary guide ring 324, while a reference numeral 326 denotes an arm which is fixed at its one end to the rocker plate 323. The other end of the arm 326 is pressed by a pressurizing unit 328 having a compressing coiled spring 327 so as to rock the rocker plate 323 in the direction of rotation. A reference numeral 329 designates a differential micrometer head contacting the arm 326 in the direction for compressing the compression coiled spring 327. The point of action 329a of the differential micrometer head 329 and the point of action 328a of the pressuring unit 328 are disposed at opposite sides of the arm 326. A reference numeral 330 designates a fixing base for fixing the differential micrometer head 329 and the pressurizing unit 328. The fixing base 330 is secured to the θ rotation mechanism base 325. A θ rotation drive motor 331 having a reduction gear is fixed to a motor mounting base 332 which in turn is fixed to the θ rotation mechanism base 325. The θ rotation drive motor 331 is connected through a coupling 333 to a rotary drum 334 so as to drive the latter. A reference numeral 335 designates a slide ring which is pressfitted into a simble 329b annexed to the differential micromotor head 329. The slide ring 335 is fitted in the rotary drum 334. A guide pin 336 is received by the elongated hole 334a in the rotary drum 334 and is fixed to the slide ring 335. As the θ rotation drive motor 331 cperates, the rotary drum 334 is rotated through the coupling 333 so that the guide pin 336, slide ring 335 and the simble 329b make spiral motion and move straight in the direction of operation of the differential micrometer head 329. As a result, the arm 326 is pushed so that the rocker plate 323 for fixing the arm 326 is guided by the rotary guide ring 324 to rotate slightly around the z axis. The slight rotation of the rocker plate 323 causes a slight rotation of the specimen holder 320 fixed to the rocker plate 323, specimen W held by the specimen holder 320 had the mask B which also is fixed to the specimen holder 320.
As the θ rotation drive motor 331 is reversed, the differential micrometer head 329 moves straight in the reverse direction. Consequently, the arm 326 is pressed by the spring force of the pressurizing unit 328 so that the rocker plate 323 is rotated around the z axis while being guided by the rotary guide ring 324. Consequently, the specimen holder 320, specimen W and the mask B are rotated slightly in the counter direction.
Consequently, by the change of the θ rotation drive motor 331, the rocker plate 323 rocks by the power of the θ rotation drive motor 331 and the spring force of the pressurizing unit 328.
The operation of the θ rotation drive motor 330 by angle θ1 causes a rotation of the rocker plate 323 by an angle Δθ which is given as follows. ##EQU3## where, S represents the travel or feed per one rotation of the differential micrometer 329, while ll shows the distance between the axis of rocking of the rocker plate 323 and the point 329a of action of the micrometer head 329. When the travel is 50 m and ll is 100 mm, the angle Δθ of rotation of the rocker plate 323 is calculated to be 3" (seconds) when the angle θ1 of operation of the motor is 1°.
The θ rotation drive motor 331 operates under the control of the control section (not shown) for an α rotation drive motor. The θ rotary drive mechanism base 325 is fixed to a β rotation mechanism A2 which has a substantially identical construction to the θ rotation mechanism A1, although it is driven not by motor but manually. A reference numeral 337 designates a β rocker plate to which fixed is the θ rotation mechanism base 325. The β rocker plate 337 is rotatably held by the β rotation guide ring 338 so as to be rotated smoothly around the y axis. A reference numeral 339 designates an arm which is fixed at its one end to the β rocker plate 337, while the other end of the same is pressed by a pressurizing unit 341 having a compression coiled spring 340 which biases the β rocker plate 337 in the rocking direction. A differential micrometer head 342 contacts the arm 339 in the direction for compressing the compression coiled spring 340. The pressurizing unit 341 and the differential micrometer head 342 are fixed to a base 343 which in turn is fixed to the β rotation guide ring 338. The β rotation guide ring 338 is fixed to the z-direction drive mechanism A3.
To explain in more detail about the z-direction drive mechanism A3, a reference numeral 344 designates a z-axis moving member to which the β rotation guide ring 338 is fixed. The z-axis moving member 344 is slidably held by a z-axis base 346 through two pairs of cross roller guides 345 so as to be able to slide in the direction of z axis. A differential micrometer head 347 is disposed to allow the moving member 344 to move in the direction of z axis. The differential micrometer head 347 is fixed to a base 348 which in turn in fixed to the z-axis base 346. Tension springs 349-1 and 349-2 are fixed to the moving body 344 and the z-axis base 346 so as to press the moving body 344 against the differential micrometer head 347. The z-axis moving base 346 is fixed to an x-axis drive mechanism A4.
The x-axis drive mechanism A4 has the following construction. A reference numeral 350 designates an x-direction moving member which is slidably carried by an x-axis base 352 through two pairs of cross roller guides 351 for sliding movement in the direction of the x axis. An x-axis drive motor 353 is fixed to a reduction gear 354 secured to a bracket 355 fixed to the x-axis base 352.
A reference numeral 356 designates a coupling through which the reduction gear 354 is connected to the ball screw 357 so that the torque of the x-axis drive motor 353 is transmitted to the ball screw 357 through the coupling 356. Numerals 358 and 359 denote brackets which accomodate ball bearings 360, 361, respectively. The brackets are fixed to the x-axis base 352. The ball screw 357 is supported by ball bearings 360, 361. A reference numeral 362 designates a nut engaging with the ball screw 357 and fixed to the x-axis moving member 350. The torque of the x-axis drive motor 353 is transmitted through the reduction gear 354 and the coupling 356 to the ball screw 357 so that the x-axis moving member 350 is moved in the direction of the x-axis through the nut 362. Operation of the x-axis drive motor 353 by an angle θ2 causes a movement Δx of the x-axis moving member expressed by the following equation. ##EQU4##
LL: lead of ball screw 357
Q reduction ratio of reduction gear 354
The amount of movement Δx is calculated to be 0.0025 μm on the condition of LL=2 mm, Q=1/100 and θ2 =0.045°.
The x-axis drive motor 353 is under the control of the x-axis drive motor control section (not shown). The x-axis base 352 is mounted on the vibration damping base E.
An explanation will be made hereinunder as to the optic path partial intercepter C with reference to FIGS. 37 and 38. A reference numeral 363 denotes a mask having windows C1, C2 formed, as shown in FIG. 39, in the portions corresponding to the windows B1, B2 in the mask B mentioned before. The windows C1 and C2 have lengths and breadths which are Δδ greater than those of the windows B1 and B2. A reference numeral 364 designates a rotary plate for bonding and fixing the mask 363, while 365 designates an intercepting plate for intercepting two ray beams from the window C2 in the mask 363. The intercepting plate 365 is bonded and fixed to an arm 366. A reference numeral 367 designates a fulcrum pin fixed to the rotary plate 364. The arm 366 is so mounted as to be able to rotate around the fulcrum pin 367. An arm regulating plate 368 is adapted to regulate the movement of the arm 366 such that the latter rotates along the rotary plate 364. A reference numeral 369 denotes a leaf spring which presses the arm 366 against the rotary plate 364. Another leaf spring 370 is arranged to press the arm 366 to the rotary plate when the arm 366 has been rotated to the position shown by one-dot-and-dash line. A reference numeral 371 designates a yarn retained at its one end by the arm 366 while the other end is fixed to a bobbin 372. As the yarn is wound up by the bobbin 372, the arm 366, which has been pressed by the leaf spring 369, is rotated around the fulcrum pin 368 to the position shown by one-dot-and-dash line while winding up the yarn. Then, the arm 366 is resiliently held by the leaf spring 370. Namely, during the alignment, two ray beams are intercepted by the intercepting plate 365 during aligning so that the window C2 in the mask 363 is not exposed to two ray beams. For conducting the exposure after the completion of aligning operation, the arm 366 to which the intercepting plate 365 is fixed is rotated by means of the bobbin 372 so that the window C2 in the mask 363 is exposed to two ray beams. After the exposure, the arm 366 is rotated manually and is resiliently pressed and held by the leaf spring 369.
A reference numeral 373 denotes a rotary ring to which the rotary plate 364 is fixed, 374 denotes a rod for guiding the rotary ring, 375 denotes a rod support for supporting the rod 374 and 375 denotes a base to which the rod support is fixed. In order to prevent vibration from being transmitted to the vibration-free base E, the base 376 is fixed to a bed (not shown) different from the vibration-free base E. A reference numeral 377 denotes a compression coiled spring disposed between the rod support 375 and the rotary ring 373 and adapted to act along the guide constituted by the rod 370. A reference numeral 378 designates a nut screwed to the threaded portion of the rod 370, while a numeral 379 designates a guide pin fixed to the rod 374 and received by a groove 373a formed in the rotary ring 373.
When the rotary ring 373 is within the range of between (a) and (b) of the groove 373a shown in FIG. 40, the rotary ring 373 is moved straight back and forth in the direction of z-axis while being guided by the guide pin 379, as the nut 378 is tightened or loosened. The straight movement of the rotary ring 373 causes a straight movement of the rotary plate 364 in the direction of the z-axis. The distance between the mask 363 and the mask B is adjusted by the straight movement of the rotary plate 364.
As the nut 378 is loosened to bring the rotary ring 373 relatively to the guide pin 379 to the position (b) in the groove 373a, the rotary ring 373 can be rotated manually around the axis of the rod 374 in the direction of the angle θ until the portion (c) of the groove 373 of the rotary ring 373 contacts the guide pin 379. Then, as the nut 378 is further loosened, when the guide pin 379 is within the region of between (c) and (d) in the groove 373a in the rotary ring 373, the rotary ring 373 moves in the direction of z-axis while being guided by the guide pin 379.
In order to mount and demount the specimen W and the mask B on and from the specimen holder 320, the nut 374 is losened to the position (b) in the groove 373a in the rotary ring 373 so that the rotary plate 364 do not hinder the mounting and demounting of the specimen W and the mask B. When the groove 373a of the rotary ring 373 is moved to the position (b), the rotary ring 373 is rotated manually until the portion (c) of the groove 373a is contacted by the guide pin 379 and, then, as the nut 373 is further loosened, the rotary plate 364 connected to the rotary ring 372 is held at the position shown by one-dot-and-dash line (e).
After the mounting of the specimen W and the mask B, the nut 378 is tightened until the position (c) in the groove 373a in the rotary ring 373 is reached, and the rotary ring 373 is rotated until the portion (b) of the groove 373a in the rotary ring 373 is contacted by the guide pin 379. Then, the nut 378 is tightened to move the rotary ring 373 straight to adjust the distance between the mask 363 and the mask B.
An explanation will be made hereinunder as to the optic path full intercepting mechanism DA, with specific reference to FIGS 41 and 42.
A rotary lever 380 is fixed to a rotary solenoid 381 which in turn is fixed to a fixing plate 382. A rod 383 guided by a rod support 384 is connected to the fixing plate 382. A reference numeral 385 designates an adjusting screw for effecting height adjustment of the rod 383 with respect to the optic axis. The rod support 384 is fixed to a base 386 which in turn is mounted on a base (not shown) different from the vibration-free base E. For passing the ray RA to the specimen W, the rotary solenoid 381 is operated to bring the rotary lever 380 to the position shown by one-dot-and-dash line (f1).
Using the system as described hereinbefore, the exposure method of the invention is carried out in the following steps (1) to (27).
(1) The laser source 310 is started to emit a coherent ray.
(2) The ray is intercepted by the optic path full intercepter DA.
(3) The specimen W is mounted on the specimen holder 320 and is held by vacuum sucking.
(4) The mask B is mounted on the specimen holder 320 so that the window B1 of the mask B is arranged to the position of the grid G on the specimen W and is held by vacuum sucking.
(5) The optic path partial intercepter C is operated to bring the window C1 in the mask 363 thereof to the position corresponding to the window B1 in the mask B. Namely, the nut 378 is tightened until the rotary ring 373 comes to the position (c1) in the groove 373a, and the rotary ring 369 is rotated until the portion (b1) of the groove 373a is contacted by the guide pin 379. Subsequently, the nut 378 is further loosened and the rotary ring 373 is further moved straight until a predetermined distance between the mask 363 and the mask B is obtained. Then, the arm 366 is rotated to bring the intercepting plate 365 to the position corresponding to the window C2 in the mask 363, so as to prevent the window C2 from being exposed to the two ray beams. The arm 366 is then held in this position by the leaf spring 369.
(6) To dismiss the interception of the light by the optic path fullintercepter DA to permit the ray beams to pass through.
(7) The coherent ray beam RA from the laser source 310 is applied to the beam splitter BS through the reflecting mirrors 311, 312, lens 313, pin hole 314, collimeter lens 315 and reflecting mirror 316, and is amplitudesplitted by the beam splitter BS into a reflected ray beam R1 and transmitted ray beam R2 which impinge upon the specimen W through the reflecting mirrors M1, M2 and the window C1 in the mask 363 and the window B1 in the mask B.
(8) The position of the specimen W is adjusted in the α direction and β direction to minimize the number of the interference fringes formed by two ray beams impinging upon the specimen W. The correction of position in the α direction is conducted by rotating the specimen holder 320 by a small angle α around the x axis by the balance of tightening force of the bolt by which the specimen holder 320 is fixed to the rotary mechanism A1 and the resilient force produced by the belleville spring 322. The position correction in the β direction is conducted by operating the β rotation mechanism A2.
(9) An adjustment in the direction of z axis is conducted by the z-axis drive mechanism A3 so as to make the pitch of the grid G on the specimen W equal to the pitch of the interference fringe of two ray beams.
(10) Two ray beams impinging upon the grid G are diffracted by the grid G into rays R3 and R4 which are applied to the photodetectors D1 and D2 through the optic systems including lenses L1 and L2, and the light intensities, as positional information concerning the relative position between the interference fringe of two ray beams and the grid G are detected.
(11) The position of the specimen W is adjusted by the rotary adjusting mechanism A1 and x-axis drive mechanism A4 of the fine adjusting mechanism A so as to maximize the intensity of the detected ray beams. Namely, the rotary drive mechanism A1 is operated to rotate the specimen W so as to maximize the ray intensity. Subsequently, the x-axis drive mechanism A4 is controlled to drive the specimen W in the direction of x axis to maximize the ray intensity. This two kinds of operation are conducted repeatedly to set the specimen W at the position where the ray intensity is maximized.
(12) The rays are intercepted again by the optic path full intercepter DA.
(13) The intercepting plate 365 and the arm 366 are rotated such that the window C2 of the mask 363 in the optic path partial intercepter C is exposed to two ray beams.
(14) The interception of the rays by the optic path full intercepter DA is dismissed to permit the ray R to pass therethrough.
(15) The operation in the step (13) above permits two ray beams, i.e. the reflected beam R1 and the transmitted ray beam R2, to pass through the window C2 in the mask 363 and the window B2 in the mask B, respectively, so that these ray beams impinge upon the exposure position on the specimen W thereby to effect the exposure.
(16) After the exposure, the ray beam is intercepted again by the optic path full intercepter DA.
(17) The specimen W is moved by the x-axis drive mechanism A4 to change the exposure position of the specimen W, i.e. such that the window B1 of the mask B corresponds to the position which corresponds to the window C1 of the mask 363.
(18) Two rays are intercepted so that the window C2 of the mask 363 on the optic path partial intercepter is not exposed to two ray beams.
(19) Steps (6) to (18) are repeated.
(20) The exposure is accomplished after exposing all portions of the specimen W.
(21) Ray beams are intercepted by the optic path full intercepter DA.
(22) In order to prevent the optic path partial intercepter C from hindering the mounting and demounting of the mask B and the specimen W, the following operation is conducted. Namely, the nut 378 is loosened to the position (b) in the groove 373a in the rotary ring 373. When the rotary ring 373a had reached the position (b), it is rotated until the portion (c) of the groove 373a contacts the guide pin 379. Then, the nut 378 is further loosened so that the rotary plate 364 connected to the rotary ring 373 is held at the position shown by one-dot-and-dash line (e).
(23) Holding of the mask B by vacuum sucking is dismissed so that the mask B is mounted or demounted on or from the specimen holder 320.
(24) Holding of the specimen W by vacuum sucking is dismissed and the specimen W is mounted on or demounted from the specimen holder 320.
(25) The next specimen W is mounted.
(26) Steps (4) to (20) are repeated.
(27) The exposure process is completed as all pieces of specimen are exposed through the steps explained hereinabove.
As has been described, in the exposure system of the described embodiment, a ray beam RA emitted from a laser source 310 is made to impinge through optic systems from two directions. The specimen W having a grid G substantially parallel to the interference fringe of two ray beams is disposed in the optic paths of two ray beams. The rays reflected by the grid G are converged through the optic system and are led to photodetectors D1 and D2 which produce outputs representing the positional relationship between the interference fringe of two rays and the grid G. Then, the correction of position of the specimen W in the θ and x directions is conducted by operating the θ rotary mechanism A1 and the x-axis drive mechanism A4, thereby to permit an alignment with a sub-micron order of precision. After aligning the grid G of the specimen W and the interference fringe of two ray beams with a high degree of accuracy, the intercepting plate 363 of the optic path partial intercepter C is rotated to expose the window C2 of the mask 363 to two ray beams, so that two ray beams impinge upon the portion of the specimen W to be exposed. It is, therefore, possible to form a minute pattern of sub-micron order within the atmospheric air. In addition, a larger through-put becomes obtainable because the patterns are transferred at once by means of two ray beams.
The formation of the uniform fine pattern by two ray beams with the ray intensity distribution of the ray beam produced by the laser source 310 is possible only within the range of between 20 Φ and 40 Φ mm. Due to the presence of error such as those due to distortion of the semiconductor substrate, superposing error and so forth, it is not possible to expose a large specimen at once. Therefore, as shown in FIG. 34, a plurality of blocks of grid G are formed at the portions, to be exposed, of the specimen W. With this arrangement, it is possible to expose the specimen W for each block of the grid G, by employing a mask 363 which is provided at it portion corresponding to one of the blocks with a window C1 and a window C2 at its portion corresponding to any one of the portions, to be exposed, of the specimen W. It is thus possible to effectively form fine patterns even on a large-size specimen W.
Since the lengths of the sizes of the windows B1, B2 in the mask B are smaller than those of the windows C1, C2 or the mask 363 of the optic path partial intercepter C, the diffraction of rays around the edges of the windows C1, C2 is prevented to avoid any noise which may, otherwise, be contained by the ray intensities detected by the photodetectors D1 and D2 and, hence, to attain an alignment with a high degree of precision.
Usually, 0.5 to 1 hour is required until the coherent ray beam from the laser source 310 is stabilized after the start up of the laser source 310. In order to prevent accidental exposure to light which may impinge at the time of, for example, mounting or demounting of the specimen W, the optic path for the ray beam directed to the specimen is selectively intercepted fully by the optic path full intercepter DA. With this arrangement, it is possible to obtain stable coherent ray beam continuously.
Furthermore, by providing the z-axis drive mechanism and the rotary α and β rotation mechanisms, it is possible to obtain greater difference between the maximum value and minimum value of the ray intensity detected by the photodetectors D1 and D2, so that it becomes possible to obtain an alignment with a high degree of accuracy.
In order to realize the alignment as described hereinbefore, it is esential that the optic system itself is well aligned. An explanation will be made hereinunder as to an example of the apparatus for attaining this alignment.
As shown in FIG. 43, a diffraction grid G having a pitch P of, for example, 1 μm is formed on the surface of the area of the specimen W where the pattern is not to be formed, e.g. on the scribe line, such that the grid extend in parallel with the interference fringe formed as a result of mutual interference between two ray beams R1, R2. The diffracted rays R3 and R4 from the diffraction grid G impinge upon the photodetectors D1 and D2. The light of the reflected ray beam R is diffracted by the diffraction grid G so that a plurality of diffracted ray beams are formed. The area counter-clockwise from the direction of movement of the diffracted ray beam is considered as being of plus (+). As will be seen from FIG. 44, among the diffracted ray beams, the diffracted ray R10 of 0 (zero) order and the diffracted ray R11 of -1 order are reflected by reflecting mirrors M2 and M1 and come back to the laser source through a two rays split optic system 417, reflecting mirror 416 and the parallel optic system 425, as will be best seen from FIG. 49. Similarly, the light of the transmitted ray R2 is diffracted by the diffraction grid G on the specimen into a plurality of diffracted rays. Among the plurality of diffracted rays, the diffracted ray beam R20 of 0 (zero) order and the diffracted ray beam R21 of +1 order are reflected by reflecting mirrors M1 and M2 and return to the laser source through the two ray beam splitting optic system 417, reflecting mirror 416 and the parallel optic system 415.
A reference numeral 418 denotes a light-receiving element for detecting the positions of returning lights of respective diffracted ray beams R10, R11, R20, R21. The light-receiving element 418 is disposed in the vicinity of the pin hole 414 and is composed of four separate light-receiving portions a, b, c and d, and the received lights in the form of electric signals are derived through respective lead lines a', b', c' and d'. A hole e for passing the ray beam R which has passed through the pin hole 414 is formed in the center of the light receiving element 418. The hole e is located on the optic axis.
In order to permit adjustment of angles Φ1 and Φ2 of the reflecting mirrors M1 and M2, these mirrors M1 and M2 are provided with means for rotating these mirrors in the α and β directions around the x axis and y axis, respectively, by representing the optic axis by z as shown in FIGS. 47 and 48. More specifically, a reference numeral 419 designates a movable frame for fixing the reflecting mirror 420 denotes a support plate having a projection 420-α and 421, 422 denote micrometer heads fixed to the movable frame 419. The arrangement is such that, as the micrometer heads 421, 422 are operated, the ends 421-a, 422-a of these micrometer heads push the support plate 420 so that the reflecting mirror is rotated in the α and β directions around the pivot constituted by the projection 420-a of the supporting plate 420, against the tensile forces produced by the tensile springs 423, 424.
Representing the wavelength of the laser beam by λ and the pitch of the diffraction grid G on the wafer W by P, the diffraction angle Φd1 at which the reflected ray R1 is diffracted by the diffraction grid G is represented as follows by the Bragg condition.
P(sin Φd1 -sin Φ1)=mλ (4)
where, m being 0, 1, 2, 3 and other positive integers.
In the case of m=0, i.e. the diffracted ray beam R10 of 0 order, the diffraction angle Φd10 is given by the following equation (5).
P(sin Φd10 -sin Φ1)=0 (5)
Thus, in this case, a condition of Φ10 =Φ1 is obtained. Namely, the diffraction angle of the diffracted ray R10 of 0 degree equals to the angle Φ1 of incidence of the reflected ray R1, so that the diffracted light ray beam is returned to the laser source through the reflecting mirror M2, two ray splitting optic system 417, reflecting mirror 416 and the parallel optic system 415.
When m=1, i.e. in the case of the diffracted ray R11 of the 1st order, the diffraction angle Φd11 is given as follows.
P(sin Φd11 -sin Φ1)=λ (6)
If the condition of Φ1 =-Φd11 is met, the following condition is obtained. ##EQU5##
The diffraction angle Φd2 at which the transmitted ray beam R2 is diffracted by the diffraction grid G is derived from the Bragg condition as follows.
P(sin Φd2 -sin Φ2)=mλ (8)
where, m is 0, 1, 2, 3 . . . and other positive integers.
In the case of m=0, i.e. the diffracted ray R20 of 0 order, the diffraction angle Φd20 is given by the following equation.
P(sin Φd20 -sin Φ2)=0 (9)
Thus, the condition of Φd20 =Φ1 is met. Thus, the diffraction angle Φd20 of the diffracted ray R20 of 0 (zero) order equals to the angle Φ2 of incidence of the transmitted ray R2 so that the diffracted ray R20 is returned to the laser source through the reflecting mirrors M1, two ray beam splitting optic system 417, reflecting mirror 416 and parallel optic system 415.
In the case of m=1, i.e. in the case of the diffracted ray R21 of the 1st order, the diffraction angle Φd21 is given by the following formula.
P(sin Φd21 -sin Φ2)=λ (10)
If the condition of Φd21 =-Φ2 is met, the following relationship is established. ##EQU6##
If the conditions of Φ1 ≠(-Φ2), Φ1 ≠(-Φd1) and Φ2 ≠(-Φd21) are met as shown in FIG. 49, the diffracted rays R10, R11, R20 and R21 after passing through the parallel optic system 415 do not pass through the hole e of the light receiving element 418 but impinge upon any one of the light-receiving portions a, b, c and d of the light receiving element 418. The intensities of ray beams received by respective light-receiving portions are converted into electric signals and are taken out as position information. Then, by suitably operating the rotary drive mechanisms for the reflecting mirrors M1 and M2, it is possible to realize the state in which none of the light-receiving portions a, b, c and d receive the diffracted ray, i.e. the state in which all of the diffracted rays pass through the hole e in the light-receiving element 417. This state is expressed by the following equation (12).
Φ1 ≈(-Φ2)≈(-Φd1)≈(+Φd21) (12)
Representing the pitch of the interference fringe formed by interference between the reflected ray R1 and the transmitted ray R2 by Λ, this pitch is determined as follows. ##EQU7##
The equation (13) is transformed as follows by a substitution of the equation (12). ##EQU8##
The equation (14) is further transformed as follows, using the equation (7). ##EQU9##
It is thus possible to obtain the pitch Λ of the interference fringe of two ray beams R1 and R2 substantially equal to the pitch P of the diffraction grid G on the specimen W.
As the pitch Λ of the interference fringe of two rays is made substantially equal to the pitch P of the diffraction grid G of the specimen, the diffraction grid G emits the ray beams R3, R4 which are formed as a result of the wave-surface splitting of the interference light of two ray beams R1 and R2, the splitting being made by the diffraction grid G. As a result, ray intensities which represent the positional relationship between the interference fringe of two ray beams and the grid at a high resolution can be obtained by photodetectors D1 and D2. Using these light intensities representing the positional relationships, it is possible to detect the positional relationship between the interference fringe of two ray beams and the specimen W, and the position of the specimen W, i.e. position of the same in the direction perpendicular to the interference fringe and rotation of the same around optic axis is corrected in accordance with the thus detected positional relationship, thereby to align the interference fringe of two ray beams R1 and R2 with the specimen W.
More specifically, by using an He-Cd laser beam of a wavelength of 4416 Å, it is possible to form interference fringe of a small pitch of 1 μm. Using this interference fringe in combination with a diffraction grid G of 1 μm pitch, it is possible to align the specimen such as a semiconductor wafer with the interference fringe at a high degree of accuracy of not greater than several hundreds of Å.
Thereafter, an exposure is made by exposing the portion of the specimen W, i.e. the semiconductor wafer, on which the pattern is to be formed. This pattern exposure can be conducted accurately by using, in combination with the aligning system of the invention explained hereinbefore, an exposure system having an exposing function which carries out the exposure method of the invention making use of interference of two laser beams. The exposure for forming fine patterns after the alignment may be conducted by a known exposure system such as a projection exposure system.
Although the light receiving system 418 used in the described embodiment has four separate light-receiving portions, the same effect can be produced by the use of a light-receiving element unit having four light-receiving elements fixed to a substrate made of a material which permits an easy formation of the central hole for passing ray beams.
In another modification, a light-receiving element, disposed in the vicinity of the pin hole 44, has light-receiving surfaces for receiving diffracted rays R10, R11, R20 and R21 arranged in a matrix-like form and provided at the center with a fine aperture for passing the ray beams. According to this arrangement, it is possible to obtain the positions to which the diffracted ray beams are returned as the position information of second order and, hence, to facilitate the coincidence of the pitch of the interference fringe with the pitch P of the diffraction grid G.
In a further modification, the light-receiving element 418 is disposed in the vicinity of the focal point of the diffraction optic system 413, so that the diffracted rays R10, R11, R20, R21 are returned to the light-receiving surface of the light-receiving element 418 in the most constricted state. With this arrangement, therefore, it is possible to make the pitch of the interference fringe coincide with the pitch P of the diffraction grid G accurately. By disposing the pin hole 414 and the light-receiving element 418 in the vicinity of the focal point of the diffusion optic system 413, it is possible to align the pitch of the interference fringe with the pitch P of the diffraction grid G highly accurately, while intercepting unnecessary diffracted ray portions.
As will be understood from the foregoing description, the present invention offers the following advantages.
According to the invention, interference fringe is formed by allowing two mutually conjugate ray beams to interfere with each other, and aligned with a grid formed on a wafer. The rays formed as a result of wave-surface splitting by the grid, i.e. the ray beam reflected by the grid and the ray beam transmitted by the grid are made to interfere with each other through a lens and the intensity of the interfered ray beam is measured. It is possible to know the positional relationship between the interference fringe and the grid by the measurement of the ray intensity, so that a highly accurate alignment can be attainable through this measurement. A high degree of accuracy of alignment is attainable by measuring the intensities of the sum and difference of diffracted ray beams from conjugate grids. By applying this technic to an exposure process employing laser holography, it is possible to effect the alignment and exposure, simultaneously without using any mask.
According to another feature of the invention, the interference fringe is made to align with a grid having a pitch which is n (n being an integer) times as large as the pitch of the interference fringe, and the ray beams formed by wave-surface splitting, i.e. reflection and transmission by the grid, are made to interfere again with each other and the intensity of the interferred ray beam is measured. Through this measurement of the ray intensity, it is possible to know the relative position between the interference fringe of two ray beams and the grid, so that a highly accurate alignment becomes attainable. By applying this technique to the exposure process employing laser holography, it is possible to effect the alignment and the exposure simultaneously without using any mask. The accuracy of the alignment in this case is on the order of several hundreds of Å when the pitch of the grid on the wafer is 1 μm.
In a practical form of the aligning method of the invention, the ray beams diffracted from the grid formed on a reticle is applied to a grid formed on a wafer, and the intensities of ray beam diffracted by the grid on the wafer are measured. By so doing, it is possible to align the pattern on the wafer with the reticle with a high degree of accuracy. Furthermore, it is possible to effect the alignment in a short period of time by making use of a figure pattern provided on the reticle or the wafer. A high degree of accuracy of alignment on the order of several hundreds of Å can be obtained when the pitch of the grid on the wafer is 1 μm. Although in the description of the embodiments the reticle and the wafer are assumed to be a first substrate and a second substrate, this embodiment can equally be applied to alignment of ordinary photo mask other than the reticle, with the wafer or even to alignment of ordinary two objects which are to aligned with each other. Although in the described embodiment the rays transmitted through the reticle is used, the invention can equally be carried out by making use of the rays reflected by the reticle.
According to an embodiment of the invention, the accuracy of detection by the photodetector can be enhanced by the following arrangement. Using the interference fringe formed as a result of interference between two ray beams and a grid, the rays reflected and transmitted by the grid are led to the photodetectors through slits which are disposed with their longer sides extending in parallel with the interference fringe, and the intensities of these ray beams are measured by the photodetectors. By so doing, it is possible to detect the degree of parallelness between the interference fringe of two ray beams and the grid, as well as relative position therebetween in the direction of the pitch, so that the alignment can be achieved at a specifically high accuracy on the order of less than 0.05 μm.
Furthermore, according to a further feature of the invention, interference fringe formed as a result of interference between mutually conjugate ray beams is aligned with a grid formed on a wafer, the grid having a pitch equal to or n (n being an integer) times as large as the pitch of the interference fringe. After completing this aligning operation, an exposure is conducted using the same system as that used for the alignment. This arrangement simplifies the system advantageously because the exposure is conducted by the same ray beam source as that used in the alignment, while ensuring the high degree of accuracy of the alignment inherent to the invention.
The invention permits a high degree of accuracy of alignment for forming fine pattern, even when the exposure is made by X-ray ion beams, ultraviolet rays and so forth.
In a further form of the invention, a diffraction grid on a specimen is positioned substantially in parallel with an interference fringe, and a plurality of diffracted ray beam diffracted by the diffraction grid are received by light-receiving elements which produce as their outputs the positional information. Then, by rotating, for example, two reflecting mirrors, the incidence angles of two ray beams to the diffraction grid are adjusted until the pitch of the interference fringe of two ray beams become substantially equal to the pitch of the diffraction grid. With this arrangement, it is possible to detect the relative position between the interference fringe of two ray beams and the specimen at a high accuracy of an order of less than several hundreds of Å. It is, therefore, possible to obtain an exposure system which can permits, in spite of the simplified construction, the formation of fine patterns of sub-micron order and at a large through-put, with a simple construction.
Nomura, Noboru, Kugimiya, Koichi, Matsumura, Takayoshi, Yonezawa, Taketoshi
| Patent | Priority | Assignee | Title |
| 5486923, | May 05 1992 | GSI Group Corporation | Apparatus for detecting relative movement wherein a detecting means is positioned in the region of natural interference |
| 5559600, | May 05 1992 | GSI Group Corporation | Apparatus for detecting relative movement |
| 5646730, | May 05 1992 | GSI Group Corporation | Relative movement detecting apparatus using a detector positioned in a region of natural interference |
| 6861331, | Oct 16 2002 | Polaris Innovations Limited | Method for aligning and exposing a semiconductor wafer |
| 7006227, | Apr 15 1999 | CONVERSANT INTELLECTUAL PROPERTY MANAGEMENT INC | Apparatus for the in situ alignment of a mask and a semiconductor wafer |
| Patent | Priority | Assignee | Title |
| 4390279, | Jul 12 1979 | Nippon Kogaku K. K. | Alignment device in an IC projection exposure apparatus |
| 4423959, | Jul 10 1980 | Nippon Kogaku K.K. | Positioning apparatus |
| 4459026, | Aug 21 1981 | National Research Council of Canada | Viewing and measuring apparatus |
| JP207805, |
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