A projection exposure apparatus carries out scan exposure with illumination flux of slit(s) by moving a mask and a substrate in a direction of one-dimension at synchronized speeds with each other. The mask is inclined with a predetermined angle relative to the substrate in the direction of one-dimensional movement. The substrate is also moved in a direction of optical axis of projection optical system when moved in the direction of one-dimension, such that a central part of transfer area on the substrate is located on a best focal plane of projection optical system upon scan exposure.
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0. 1. A method for exposure in which a pattern formed in a transfer region on a mask is subject to projection exposure through a projection optical system to be led onto an area to be exposed on a photosensitive substrate, and said mask and photosensitive substrate are at least one-dimensionally, relatively scanned with respect to a projection field of said projection optical system: comprising,
limiting a width of said area of pattern image projected on said photosensitive substrate through the projection optical system to an approximately constant value in a direction of one-dimensional scan; and inclining a local surface on said photosensitive substrate on which said pattern image is formed, relative to a best focal plane of said projection optical system in the direction of one-dimensional scan.
0. 5. A projection exposure apparatus comprising:
a projection optical system for projecting a pattern formed in a transfer region on a mask, onto an area to be exposed on a photosensitive substrate; a mask stage for one-dimensionally moving said mask over a region beyond a width of said transfer region in a direction of movement; a substrate stage for one-dimensionally moving said photosensitive substrate in the direction of one-dimensional movement of said mask stage at a speed synchronized with a movement speed of said mask stage; illumination means for illuminating said mask with an illumination flux for exposure, having a shape between a rectangle and a slit within the projection field of said projection optical system and having an approximately constant width in the direction of one-dimensional movement; a substrate holder the holding said photosensitive substrate on said substrate stage with a predetermined inclination angle with respect to the direction of one-dimensional movement of illuminated area formed by said illumination flux on said photosensitive substrate through said mask and said projection optical system; holder drive means for moving said substrate holder in a direction of optical axis of said projection optical system such that a central part of said illuminated area on said photosensitive substrate is located near a best focal plane of said projection optical system; and control means for controlling said holder drive means to maintain an imaging condition of pattern image of said mask on said photosensitive substrate with correspondence to a position in said illuminated area in the direction of one-dimensional movement while scan exposure of pattern of said mask is effected on said area to be exposed.
0. 6. A scanning exposure method of exposing a substrate through a projection optical system with an energy beam irradiated on a mask, comprising:
distributing the energy beam within a field of view of the projection optical system within a plurality of regions extending in a second direction crossing a first direction in which the substrate is moved during scanning exposure of the substrate, and moving the substrate relative to the plurality of regions in the first direction in synchronization with movement of the mask during the scanning exposure.
0. 24. A scanning exposure method of exposing a substrate through a projection optical system with an energy beam irradiated on a mask, comprising:
moving the substrate relative to the energy beam projected by the projection optical system in synchronization with movement of the mask relative to the energy beam during scanning exposure of the substrate with the energy beam, and changing a position of a specified point on the substrate with respect to a direction along the optical axis of the projection optical system during the scanning exposure so that the energy beam is irradiated on the specified point at a plurality of different positions along the optical axis.
0. 36. A scanning exposure apparatus which moves a mask and a substrate relative to an energy beam during scanning exposure of the substrate with the energy beam through the mask, comprising:
a projection optical system disposed on an optical path along which the energy beam passes; and an illumination optical system disposed on an object plane side of the projection optical system, the illumination optical system distributing the energy beam within a plurality of regions being arranged in a first direction in which the substrate is moved during the scanning exposure and extending in a second direction crossing the first direction in a field of view of the projection optical system.
0. 27. A scanning exposure method comprising:
defining an irradiation region of illumination light on a substrate to a rectangular or slit shape for a scanning exposure of the substrate with the illumination light through a mask and a projection optical system; moving the substrate relative to the illumination light, which passes through the projection optical system, in synchronization with movement of the mask relative to the illumination light during the scanning exposure; detecting positional information of the substrate with respect to a direction along an optical axis of the projection optical system within the irradiation region of the illumination light; and irradiating the illumination light onto a specified point on the substrate at a plurality of positions in the direction within a depth of focus of the projection optical system, based upon the detection positional information during the scanning exposure.
0. 2. A method for exposure according to
0. 3. A method for exposure according to
0. 4. A method for exposure according to
0. 7. A method according to
0. 8. A method according to
0. 9. A method according to
0. 10. A method according to
0. 11. A method according to
0. 12. A method according to
0. 13. A method according to
0. 14. A method according to
0. 15. A method according to
0. 16. A method according to
0. 17. A method according to
0. 18. A method according to
adjusting a relative inclination and position between an image plane of the projection optical system and the substrate so that the image plane and the substrate are substantially coincided within the range of a focal depth of the projection optical system during the scanning exposure.
0. 19. A method according to
controlling a focus operation with respect to the substrate so that the substrate is maintained within the range of a focal depth of the projection optical system within at least one region among the plurality of regions during the scanning exposure.
0. 20. A method according to
0. 21. A method according to
changing a position of a specified point on the substrate with respect to a direction along an optical axis of the projection optical system in each of the plurality of regions when the specified point crosses each of the plurality of regions during the scanning exposure.
0. 22. A method according to
causing an exposure amount to be seamless by performing overlapping exposure within a shot area on the substrate to which a pattern of the mask is transferred when the shot area is larger than the plurality of regions with respect to the second direction.
0. 23. A method of fabricating a device, the method comprising transferring, utilizing the scanning exposure method of
0. 25. A method according to
0. 26. A method of fabricating a device, the method comprising transferring, utilizing the scanning exposure method of
0. 28. A method according to
0. 29. A method according to
0. 30. A method according to
0. 31. A method according to
0. 32. A method according to
0. 33. A method according to
0. 34. A method according to
0. 35. A method of fabricating a device, the method comprising transferring, utilizing the scanning exposure method of
0. 37. An apparatus according to
0. 38. An apparatus according to
0. 39. An apparatus according to
0. 40. An apparatus according to
0. 41. An apparatus according to
0. 42. An apparatus according to
the projection optical system is a telecentric reduction system; and further comprising a scanning system having a mask stage disposed on the object plane side of the projection optical system and a substrate stage disposed on an image plane side of the projection optical system, wherein the scanning system moves the mask and the substrate at different speeds during the scanning exposure, and, respectively, at substantially a constant speed.
0. 43. An apparatus according to
an adjusting system connected to the scanning system, the adjusting system adjusting a relative inclination and position between the image plane of the projection optical system and the substrate so that the image plane and the substrate are substantially coincided within the range of a focal depth of the projection optical system during the scanning exposure.
0. 44. An apparatus according to
0. 45. An apparatus according to
a controller connected to the scanning system, wherein the controller causes the exposure amount to be seamless by performing overlapping exposure within a shot area on the substrate to which a mask pattern is transferred, when the shot area is larger than the plurality of regions with respect to the second direction.
0. 46. An apparatus according to
0. 47. An apparatus according to
0. 48. A method of fabricating a device, the method comprising transferring, utilizing the scanning exposure apparatus of
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Illumination light for exposure from a mercury vapor lamp 1 is condensed at a secondary focus point by an ellipsoidal mirror 2. A rotary shutter 3 is disposed at the secondary focus point to switch the illumination light between interception and transmission of light by a motor 4. The illumination light passed through the shutter 3 is reflected by a mirror 5, and enters an optical integrator or fly eye lens 7 through an input lens 6. There are numerous secondary light source images formed at the output side of the fly eye lens 7, and the illumination light from the secondary light source images is led through a beam splitter 8 into a lens system or condenser lens 9.
Movable blades BL1, BL2, BL3, BL4 of a reticle blind mechanism 10 as shown in
The illumination light takes a uniform distribution of illumination at the position of the blind mechanism 10. The illumination light passed through the aperture AP of the blind mechanism 10 is guided through a lens system 11, a mirror 12, and a main condenser lens 13 to a reticle R to be illuminated. Then an image of the aperture AP defined by the four blades BL1-BL4 of the blind mechanism 10 is focussed on a pattern plane on a lower surface of the reticle R.
The reticle R receiving the illumination light defined by the aperture AP is held by a retircle stage 14, which is movable at a uniform rate at least in the X-direction on a column 15. The column 15 is incorporated with an unrepresented column holding a lens barrel of the projection optical system PL. The reticle stage 14 may be one-dimensionally moved in the X-direction and rotated by a small amount to correct its yawing by a drive system 51. A movable mirror 31 is fixed at an end of the reticle stage 14 to reflect a measurement beam from a laser interferometer 30, so that the laser interferometer 30 may measure a position of the reticle R in the X-direction and the amount of yawing in a real time manner. A fixed mirror or reference mirror 32 for the laser interferometer 30 is fixed at the upper end of the lens barrel of projection optical system PL.
An image of pattern formed in a transfer region, for example a rectangular region, of reticle R is imaged on a wafer W after reduced to one-fifth thereof by the projection optical system PL. The wafer W is held together with a reference mark plate FM by a wafer holder 16 which is rotatable by a small amount and inclinable at an arbitrary angle. The wafer holder 16 is disposed on a Z-stage, which is movable by a small amount in a direction of the optical axis AX or the Z-direction of the projection optical system PL. The Z-stage 17 is mounted on an X,Y-stage 18 which is two-dimensionally movable in the X- and the Y-directions in the step and repeat method, and the X,Y-stage 18 is driven by a drive system 52. Further, a laser interferometer 33 measures a coordinate position and a yawing amount of the X,Y-stage 18. A fixed mirror or reference mirror 34 for the laser interferometer 33 is fixed at the lower end of the lens barrel of the projection optical system, and a movable mirror 35 is fixed at one edge of the Z-stage 17. Since the projection magnification is one fifth in this embodiment, a moving velocity Vws of the X,Y-stage is set at one fifth of a velocity Vrs of the reticle stage in the X-direction 14 upon scan exposure.
Also in the present embodiment, there are provided an alignment system 40, which employs a TTR (Through-The-Reticle) method to detect an alignment mark or reference mark FM on the wafer W through the reticle R and the projection optical system PL, and an alignment system 41, which employs a TTL (Through-The-Lens) method to detect an alignment mark or reference mark on the wafer W through the projection optical system at a position below the reticle R. These alignment systems 40, 41 perform relative alignment of the reticle R and the wafer W before start of S and S exposure or during the scan exposure. If the reference mark FM is a light emitting type, a photoelectric sensor 42 as shown in
As the length of the aperture AP of the blind mechanism 10 is made longer in the Y-direction perpendicular to the scan direction or X-direction, the number of scannings in the X-direction or the number of steppings in the Y-direction on the wafer W may be reduced. However, the length of the aperture AP in the Y-direction might better be changed by the edges of the blades BL3, BL4 depending on size, shape, and arrangement of chip pattern on the reticle R. A preferred example is that the facing edges of the blades BL3, BL4 coincide with street lines dividing the shot area on the wafer W. It is easy for this arrangement to adjust the length of aperture in correspondence with a size change in the Y-direction of shot area. If a length in the Y-direction of one shot area is over the maximum length of the aperture AP in the Y-direction, overlay exposure should be effected in the shot area to obtain seamless exposure as disclosed in U.S. Pat. No. 4,924,257. Since the method itself is not always essential to the present invention, detailed explanation thereof is omitted.
Below explained with reference to
A focus and leveling sensor is provided to control the inclination angle of the wafer W, which is constructed by a light projector 19A emitting an optical flux BPL of a wave length different from that of the exposure light and a light receiver 19B receiving an optical flux BRL, which is the optical flux BPL reflected by the wafer surface. A focus point, of the optical flux BPL from the focus and leveling sensor is coincident with a line including a point through which the optical axis of the projection optical system PL passes on the wafer W. An example of the focus and leveling sensor is disclosed in U.S. Pat. No. 4,558,949. Thus detailed explanation is omitted.
The leveling drive sections 20A, 20B are driven by a command from a leveling control system 53 to determine an inclination amount of wafer holder 16, based on leveling information from the light receiver 19B and information from the main control section 100. With constant feed back of leveling information from the light receiver 19B, a proper inclination angle of the wafer W may be maintained. Further, focus information could be obtained to always locate an intersection with the optical axis AX on the wafer W on the best imaging plane of the projection optical system, with the information from the focus and leveling sensor. In this case, the motor 21 is driven by a command from the Z-stage control system 54 based on position information obtained by the light receiver 19B, to drive the Z-stage 17 in the direction of the optical axis AX.
The optical flux BPL is radiated on the wafer W as a slit light SLI inclined by 45°C with respect to the rectangular illumination area AP' defined by the aperture AP of the blind as shown in FIG. 3B. By this, the position and the inclination of the wafer W in the Z-direction may be controlled without influence from the directionality of circuit pattern in the chip area CP1-CP4 already formed on the wafer W. Although there is shown only two points of the leveling drive section for explanation, it is no doubt that drive on three points is better.
In the focus and leveling sensor as disclosed in the above-mentioned U.S. Pat. No. 4,558,949, parallel optical fluxes occupying a determined ara are impinged on the wafer surface, and reflection optical flux from the wafer surface is photoelectrically detected, for example using a quartered photodetector, to detect the inclination or the leveling information of the wafer surface. Then, a variable field stop may be disposed inside the light projector 19A as disclosed for example in U.S. Pat. No. 4,902,900, to adjust the size and the shape of illumination area of parallel optical fluxes on the wafer surface, so that the size and the shape of the illumination area or detection area of the parallel optical fluxes on the wafer surface is desirably made almost coincident with the rectangular illumination area AP' defined by the aperture AP of the blind. By this, an average inclination of a local area in the shot region on the wafer W corresponding to the rectangular illumination area AP' may be effectively detected, the inclination amount of the wafer surface or wafer holder 16 may be controlled with a higher precision.
An operation of the preferred embodiment of the projection exposure apparatus will be below explained. The main control section 100 totally dominates the sequence and control of the operation as shown in
The scan exposure is controlled such that the X,Y-stage 18 is driven in the X-direction and the Z-stage 17 is simultaneously driven in the direction of the optical axis AX, to always locate the approximate center in the illumination area of the wafer W (corresponding to the approximate center of illumination range of exposure flux) on the best imaging plane BF of the projection optical system PL. If the width of illumination area AP' on the wafer W is defined as Dap, the inclination angle between the illumination area AP' on the wafer W and the best imaging plane BF as θ1, and a width in the optical axis of the depth of focus of the projection optical system PL (DOF) as ΔZf, at least one of the depth Dap of the illumination area and inclination angle θ1 is adjusted to satisfy the following relation: Dap·sin θ1≧ΔZf. A theoretical depth of focus is normally given by an equation ΔZf=λ/NA2, where λ is an exposure wave length, and NA is a numerical aperture of projection optical system.
A positional relation of wafer W and pattern IR to the exposure flux just after the scan exposure start is shown in FIG. 4A. Noting the position 2 in the circuit pattern IR, it is just entered within the illumination range of exposure flux. However, an image at the position 2 on the wafer W is in a condition of defocusing and the distribution of intensity of projection image has a gentle peak.
In order to narrow the width W, there may be provided at least two peaks in the one-dimensional scan direction of scan exposure in the distribution of intensity of rectangular illumination flux. For example, as shown in
Furthermore, three peaks may be employed in the one-dimensional scan direction of scan exposure in a distribution of intensity of rectangular illumination flux. For this purpose, a reticle blind mechanism is provided with blades with three slits in the aperture.
Comparing two slits and three slits in the one-dimensional direction of scan exposure in the intensity distribution of rectangular illumination flux if the optical intensity of illumination flux is almost identical, exposure with three slits allows faster moving speed of the X,Y-stage and gives a higher throughput. This is opposite to the successive focussing exposure method conventionally known in U.S. Pat. No. 4,869,999.
In the above examples, the blades of the blind mechanism have a light intercepting portion. In another arrangement, the same effect may be obtained by an interception member such as ND filter having dimensions and shape corresponding to a region to be intercepted at a position conjugate to the circuit pattern IR in the optical path. Furthermore, although the wafer surface is inclined before the scan exposure in the above examples, the inclination of the wafer holder 16 may be controlled together with the Z-directional position of the wafer surface by using detection information of the focus and leveling sensor at the time of scan exposure start.
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