JPH05315214A - Adjusting method of alignment apparatus - Google Patents

Abstract

PURPOSE:To facilitate precise positioning of a member in which corrective optical elements used to compensate for a chromatic aberration are arranged. CONSTITUTION:A transparent member 5 in which corrective optical elements 1a to 1c are formed is arranged at the inside of a projection optical system 21. A reference mark 42 is formed near a wafer on a wafer stage 19; the reference mark 42 is irradiated with light fluxes 4a, 4b for alignment use via the projection optical system 21 from a microscope 43 for alignment use. The transparent member 5 is positioned in such a way that the intensity of an interference beam 4c returned from the reference mark 42 becomes largest.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for application to a method of adjusting an alignment system of a projection exposure apparatus having a projection optical system for transferring a pattern formed on a reticle (mask) onto a wafer. In particular, the present invention relates to a method for adjusting an alignment apparatus that performs relative alignment between a reticle and a wafer by using alignment light in a wavelength band different from exposure light for transferring a reticle pattern onto a wafer.

[0002]

2. Description of the Related Art A projection exposure apparatus for transferring a reticle pattern onto a wafer through a projection optical system is used when manufacturing a semiconductor element, a liquid crystal display element or the like by using a photolithography technique. In general, semiconductor devices are manufactured by forming a multi-layered circuit pattern on a wafer, so in the process of transferring a new reticle pattern to a wafer on which a pattern has already been formed, the pattern to be transferred this time has already been formed. It is necessary to accurately align the reticle and the wafer with each other.
Recently, as the fineness of a transferred pattern is further improved, it is most important to improve the alignment accuracy and the imaging performance of the projection optical system.

In order to improve the former alignment accuracy, a so-called TTL for performing alignment through a projection optical system.
The (through the lens) method is expected to achieve the highest accuracy in principle. Also, TTL
Although included in the system, the TTR (through the reticle) system in which the wafer is aligned through both the reticle and the projection optical system is also expected to achieve high accuracy. In the method of aligning the reticle and the wafer by detecting the alignment mark on the wafer through the projection optical system as described above, the alignment light in the wavelength band different from the exposure light is used to apply the light onto the wafer. Care is taken not to expose the resist.

However, when performing alignment based on alignment light in a wavelength band different from the exposure light, there is a problem that axial chromatic aberration and lateral chromatic aberration occur with respect to the alignment light by the projection optical system. Note that the chromatic aberration of magnification referred to in the present application means lateral chromatic aberration. This means off-axis light having the same wavelength as the exposure light that is imaged on the Gaussian image plane by passing through the projection optical system and the projection optics. Both the chief rays of the exposure light, which is imaged at the Gaussian image plane or before and after the Gaussian image plane by passing through the system, and the alignment light having a different wavelength, are between the intersecting positions when intersecting on the Gaussian image plane. It defines the deviation.

Then, the amount of lateral chromatic aberration (horizontal chromatic aberration amount) Δ
T is a value on the Gauss image plane from a crossing position where a chief ray in the off-axis light having the same wavelength as the exposure light imaged on the Gauss image plane by passing through the projection optical system intersects on the Gauss image plane. The distance to the optical axis position of the projection optical system is δ1, and the principal ray of the alignment light having a wavelength different from that of the Gaussian image plane or the exposure light imaged before and after passing through the projection optical system is the Gaussian image plane. When the distance from the crossing position intersecting with each other to the optical axis position of the projection optical system on the Gaussian image plane is δ2, it is defined by ΔT = | δ2-δ1 |.

[0006] The applicant of the present invention has proposed, in Japanese Patent Application No. 3-129563, an alignment apparatus which compensates for axial chromatic aberration and lateral chromatic aberration due to a projection optical system for alignment light. FIG. 7 shows the alignment apparatus disclosed in Japanese Patent Application No. 3-129563, in which the pattern surface of the reticle 6 and the exposure surface of the wafer 9 are telecentric on both sides or on one side under exposure light. It is arranged conjugate with the optical system 21. Projection optical system 21
Has excellent chromatic aberration corrected with respect to exposure light made of, for example, excimer laser light. A reticle mark RM in the form of a diffraction grating for alignment is formed on the reticle 6, and a wafer mark 10 in the form of a diffraction grating for alignment is also formed on the wafer 9. Wafer 9
It can be moved in the X and Y directions in the horizontal plane, can be rotated in the horizontal plane, and can be moved in the Z direction parallel to the optical axis of the projection optical system 21. An illumination optical system for exposure light (not shown) is arranged in the.

In the alignment system shown in FIG. 7, reference numeral 31 denotes an alignment light source for generating alignment light having a wavelength band different from that of the exposure light. As the alignment light, for example, He-Ne laser light having a wavelength of 633 nm is used. .. The light beam emitted from the light source 31 is split into a first light beam 4a and a second light beam 4b by a semi-transmissive mirror 32, and the first light beam 4a passes through a first acousto-optic modulator 34a to a semi-transmissive mirror 35. The second light beam 4b faces the bending mirror 33.
And the semi-transmissive mirror 35 via the second acousto-optic modulator 34b.
Head to. The acousto-optic modulators 34a and 34b are driven by high-frequency signals of frequencies f1 and f2 (f2 = f1-Δf), respectively, and the frequencies of the light beams 4a and 4b passing through the acousto-optic modulators 34a and 34b differ by Δf. .. In this case, it is desirable that f1 >> [Delta] f and f2 >> [Delta] f, and the upper limit of [Delta] f is determined by the responsiveness of the photoelectric detectors 41a to 41c for alignment described later.

Light fluxes 4a and 4 reflected by the semi-transmissive mirror 35
Reference numeral b is a reference reference diffraction grating 37 formed by a condenser lens 36 at a predetermined pitch in a direction parallel to the paper surface of FIG.
Focused on top. An interference fringe that flows on the diffraction grating 37 is formed by the two light beams 4 a and 4 b having a relative frequency difference Δf, and the diffracted light that has passed through the diffraction grating 37 enters the photoelectric detector 38. The reference signal output from the photoelectric detector 38 becomes a sinusoidal AC signal (optical beat signal) corresponding to the cycle of the change in brightness of the interference fringes formed on the diffraction grating 37.

On the other hand, the two light beams 4a and 4b transmitted through the semi-transmissive mirror 35 are focused on the reticle mark RM provided outside the exposure area of the reticle 6 via the objective lens 39 and the mirror 40 of the alignment system. .. At this time, on the reticle mark RM, the difference Δf in frequency between the light beams 4a and 4b.
An interference fringe that changes so as to flow is formed. The reticle mark RM is formed by a diffraction grating formed at a predetermined pitch in a direction parallel to the paper surface of FIG.
A reticle window RW for transmitting alignment light is formed at a position adjacent to M.

The light beams 4a and 4b focused on the reticle 6 by the objective lens 39 of the alignment system cover the reticle 6 at a predetermined crossing angle so as to cover not only the reticle mark RM but also the reticle window RW at the same time. Illuminate from the direction. Then, one of the light beams 4a is reticle mark R.
When M is obliquely irradiated, the 0th order light is reflected in the direction (regular reflection direction) of the other light beam 4b in the opposite direction, and the + 1st order diffracted light is generated in the direction of the other light beam 4a in the opposite direction. Similarly, when the other light beam 4b obliquely irradiates the reticle mark RM, the 0th order light is reflected in a direction that follows the optical path of the one light beam 4a in the opposite direction, and the −1st order diffracted light in the direction that follows the optical path of the light beam 4b in the opposite direction. Occurs.

In this case, the light beams 4a and 4b incident on the reticle mark exist in a plane parallel to the paper surface of FIG. 7, and the incident angles of the light beams 4a and 4b with respect to the reticle mark are set to θ _R and −θ _R , respectively. 7, the pitch in the direction parallel to the paper surface of FIG. 7 is P _R , and the wavelengths of the light beams 4a and 4b are λ (however, strictly speaking, they are slightly deviated from λ), s
The incident angle and pitch are set so as to satisfy the relationship of in2θ _R = λ / P _R.

Therefore, the + 1st-order light of one light beam 4a from the reticle mark RM and the 0th-order light of the other light beam 4b return to the semitransparent mirror 35 through the mirror 40 and the objective lens 39 in parallel with each other. A photoelectric detector 41a which is reflected by the transmission mirror 35 and is arranged at a position conjugate with the pupil of the objective lens 39.
Incident on. Similarly, the 0th-order light of one light beam 4a and the -1st-order light of the other light beam 4b from the reticle mark RM return to the semitransparent mirror 35 through the mirror 40 and the objective lens 39 in parallel with each other, and the semitransparent Photoelectric detector 41b reflected by the mirror 35 and arranged at a position conjugate with the pupil of the objective lens 39
Incident on. An optical beat signal corresponding to the position of the reticle mark RM is detected by these photoelectric detectors 41a and 41b.

Next, the light beams 4a and 4b obtained by illuminating the reticle window RW adjacent to the reticle mark RM from two directions at a predetermined crossing angle (2θ _R ) pass through the reticle window RW as they are, and are projected onto the projection optical system 21. Incident from off-axis. The projection optical system 21 is sufficiently chromatic aberration-corrected for the exposure light, but is not chromatic-aberration-corrected for the alignment light in the wavelength band different from the exposure light. Therefore, the projection optical system 2
A transparent member 5 is arranged on the pupil plane of No. 1, and X is a measurement direction passing through the center of the optical axis of the projection optical system 21 on the transparent member 5.
Three correction optical elements 1a to 1c made of phase type diffraction gratings having mutually different pitches along the direction.
Are arranged. The correction optical element 1c is arranged on the optical axis of the projection optical system 21, and the correction optical elements 1a and 1b are arranged symmetrically with respect to the optical axis of the projection optical system 21. The correction optical elements 1a to 1c are arranged along the X direction so that the correction optical elements 1b, 1c, and 1a have a dense diffraction grating pitch.

In FIG. 7, light beams 4a and 4b which are incident on the projection optical system 21 from off-axis and are incident on the pupil (incident pupil) of the projection optical system 21 are respectively corrected by the correction optical elements 1b and 1a. The wafer mark 10 that is deflected (diffracted) so as to be corrected by the correction angles θ1 and θ2 is irradiated from two directions at a predetermined crossing angle. The frequency Δf of the difference between the two light fluxes is also displayed on the wafer mark 10.
An interference fringe that changes so as to flow is formed. The wafer mark 10 is composed of a diffraction grating formed at a predetermined pitch in the X direction, which is the measurement direction, on the street line outside each shot area.

By thus irradiating the wafer mark 10 with the light beams 4a and 4b at a predetermined intersection angle, the −1st-order light of one light beam 4a and the + 1st-order light of the other light beam 4b are exposed on the wafer 9. It occurs in the normal direction to the surface (direction parallel to the optical axis of the projection optical system 21). In this case, the wafer mark 1
The pitch of 0 is P _W , the wavelength of the alignment light is λ, and the luminous flux 4
When the crossing angle of a and 4b is 2θ _W , sin θ _W =
The pitch and the crossing angle are set so as to satisfy the relationship of λ / P _W.

The −1st-order light of the light beam 4a and the + 1st-order light of the light beam 4b generated in the normal direction of the wafer mark 10 travel in parallel with each other as beat interference light 4c on the optical path of the principal ray of the projection optical system 21, After being deflected (diffracted) by the correction angle θ3 by the correction optical element 1c provided at the center of the pupil of the projection optical system 21, the reticle window RW of the reticle 6 and the mirror 4 are again reflected.
0, the light passes through the objective lens 39 and the semi-transmissive mirror 35 and enters the photoelectric detector 41c arranged at a position conjugate with the pupil of the objective lens 39. In this photoelectric detector 41c, the wafer mark 1
The optical beat signal corresponding to the position of 0 is detected. A signal including position information of the reticle mark RM output from the above-mentioned photoelectric detectors 41a and 41b and the photoelectric detector 41c thereof.
It is possible to accurately detect the relative positional relationship between the reticle 6 and the wafer 9 based on the signal including the positional information of the wafer mark 10 output from.

This detection method is called a so-called optical heterodyne method, and if the positional deviation between the reticle 6 and the wafer 9 from the reference state is within 1 pitch of the reticle mark RM and within 1/2 pitch of the wafer mark 10. Even in the stationary state, the positional deviation amount can be accurately detected with high resolution. Therefore, it is suitable for use as a position signal when a position servo of the closed loop system is applied so as not to cause a minute position shift while the pattern of the reticle 6 is exposed on the resist of the wafer 9. In this detection method, after the reticle 6 or the wafer 9 is moved so that the phase of the optical beat signal from the reticle mark RM and the phase of the optical beat signal from the wafer mark 10 become predetermined values, alignment is completed. The servo lock can be continuously applied so that the reticle 6 and the wafer 9 do not move relative to each other at the alignment position.

As described above, in the alignment apparatus of FIG. 7, the irradiation light for alignment is corrected by the correction optical elements 1a, 1b, 1c arranged on the transparent member 5 provided at the pupil position of the projection optical system 21. On-axis chromatic aberration and lateral chromatic aberration of the (light fluxes 4a, 4b) and the detection light (beat interference light 4c) by the projection optical system 21 are corrected. The correction optical element 1a including a phase type diffraction grating
Corrective optics such as declination prisms can be used in place of ~ 1c.

In the correction optical element such as the phase type diffraction grating (phase grating), the Japanese Patent Application No. 3-12596 is used.
As described in No. 3, the device is so devised that it does not affect the wavefront of the exposure light and consequently the imaging performance of the projection optical system 21. For example, in the case of a phase grating, the etching depth of the phase grating is an integral multiple of the wavelength of the exposure light, or a thin film having a wavelength selection function of reflecting the exposure light on the phase grating and transmitting the alignment light. Have been devised such as forming by vapor deposition.

[0020]

In the apparatus shown in FIG. 7,
Correction optical elements 1a to 1 placed on the pupil plane of the projection optical system 21
The element c is a phase grating and has a directivity in which the bending direction of the light flux changes depending on the direction of the incident light flux. Therefore, the accuracy of the mounting angle of the transparent member 5 in which these are arranged in a plane perpendicular to the optical axis of the projection optical system 21 is calculated from the accuracy required for the alignment itself and the size of the alignment mark. The value becomes a considerably small value. For example, the mounting angle needs to be aligned with the alignment optical system with an accuracy of several minutes. Also, regarding the positioning in the X direction and the Y direction in the same plane, since the alignment light is a thin beam such as a He-Ne laser, it is necessary to align it with the optical path with an accuracy of a fraction of a few millimeters. ..

However, the individual lenses constituting the projection optical system have a rotational symmetry with respect to the optical axis of the exposure light, and conventionally, in the projection optical system, in general, one of the lenses is assembled after the assembly. No mechanism is provided for rotating the lens or shifting it horizontally. Even if such a mechanism is provided, it is difficult to adjust the position of an originally transparent object such as a phase diffraction grating in the projection optical system while visually or observing with a television camera or the like. is there. Therefore, in order to accurately perform the positioning adjustment of the transparent member 5 on which the correction optical element is arranged as described above, it is necessary to use a special positioning device and a special adjustment method.

Furthermore, since the position accuracy of the transparent member 5 needs to be maintained not only at the time of initial adjustment of the projection optical system but also after that, the positioning device and the adjusting method thereof are easy even after the projection optical system is incorporated in the exposure device. Must be available at any time. In view of the above problems, the present invention is capable of easily and highly accurately positioning a member having a correction optical element formed therein with respect to an alignment apparatus using a member having a correction optical element formed therein for compensating for chromatic aberration. It aims at providing the adjustment method which can be.

[0023]

A method of adjusting an alignment apparatus according to the present invention is, for example, as shown in FIGS.
The alignment mark and the pattern on the mask (6) on which the pattern for transfer is formed are placed on the stage (19) through the projection optical system (21) under exposure light to form the alignment mark. Irradiation means provided in an exposure device for transferring onto a photosensitive substrate and irradiating alignment marks on the photosensitive substrate with alignment light (4a, 4b) having a wavelength band different from that of the exposure light via the projection optical system (21). (43), a detection means (43) for detecting the alignment light from this alignment mark via the projection optical system (21) and generating a light receiving signal, and the projection optical system (21) substantially in the pupil plane. The chromatic aberration (axial chromatic aberration and lateral chromatic aberration) generated by the projection optical system (21) for the alignment light formed on the holding substrate (5) arranged in A positive optical element (1) is provided, and the mask (6) and the alignment mark formed on the photosensitive substrate are illuminated with the alignment light to perform relative alignment between the mask and the photosensitive substrate. This is a method of adjusting the positioning state of the holding substrate (5) in the alignment apparatus.

In the present invention, the reference mark (42) is formed on the stage (19) on which the photosensitive substrate is placed,
With the reference mark (42) set at a predetermined position within the exposure area of the projection optical system (21), the reference mark (42) is irradiated by the irradiation means (43) with the alignment light (4a, 4b). And illuminates it through the projection optical system (21), and detects the alignment light (4c) from the reference mark (42) by the detection means (43) through the projection optical system (21). The holding substrate (5) is positioned so that the received light signal generated by the means (43) is in a predetermined state.

In this case, the alignment device is provided with a monitor means (16) for monitoring the light reception signal of the detecting means (43) and a positioning means (16) for positioning the holding substrate (5). Monitor means (16)
When it is detected that the detection signal of the detecting means (43) deviates from the predetermined state by the positioning means (1
6), the holding substrate (5) may be repositioned.

[0026]

In the present invention, the holding substrate (5) on which the correction optical element (1) is arranged is supported so that it can be positioned in the projection optical system (21). In the positioning, first, the holding substrate (5) is roughly positioned with the reference mark (42) on the stage (19) set at a predetermined position, and the alignment light from the irradiation means (43) is projected onto the projection optical system. The reference mark (42) is even partially applied via the system (21). After that, the holding substrate (5) is finally positioned so that the intensity of the received light signal obtained by detecting the alignment light from the reference mark (42) by the detection means (43) is maximized, for example. ..

In this case, instead of visually observing the correction optical element such as the phase grating or using a television camera or the like, the light receiving signal obtained by the detecting means (43), that is, the signal for alignment is used to hold the holding substrate (5 Since it is determined whether the state (2) is good or bad, the holding substrate (5) can be positioned easily and with high accuracy.

When the monitor means (16) and the positioning means (16) are provided, the intensity of the received light signal obtained by the detecting means (43) when the holding substrate (5) moves due to aging or the like. And the like change, it is possible to know the position variation of the holding substrate (5). Then, by positioning the holding substrate (5) by the positioning means (16), repositioning can be automatically performed. Therefore, stable alignment can be performed over a long period of time.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an alignment apparatus adjusting method according to the present invention will be described below with reference to FIGS.
In the present embodiment, the present invention is applied to a projection exposure apparatus, and in FIGS. 1 to 4, parts corresponding to those in FIG. 7 are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 shows the inside of the projection optical system 21 of the present embodiment. In FIG. 1, 11 is a lens barrel. A holding ring 12 having four claws is fixed to the inner surface of the lens barrel 11 of the projection optical system 21 in the vicinity of the pupil plane.
The presser ring 13 is housed inside 2 in such a manner that it has a margin corresponding to the adjustment margin and does not fall off.
A transparent member 5 made of parallel flat plate glass or the like is held inside. The correction optical element 1 formed of a phase grating is formed on the transparent member 5. Further, the pressing ring 13 is attached to the lens barrel 11
It is connected to a drive device 16 provided outside the projection optical system 21 via a drive shaft 15 passing through the opening 14 on the side surface of the.

FIG. 2 is a sectional view of the projection optical system 21 shown in FIG. 1. As shown in FIG. 2, the transparent member 5 is pressed into the end of the pressing ring 13 by the retaining ring 18. In addition, ring-shaped spacers 17a and 17b are attached to the front and rear of the holding ring 12 inside the lens barrel 11. The spacers 17a and 17b are a part of spacers used for positioning and fixing the lens forming the projection optical system 21 inside the lens barrel 11 in the optical axis direction (Z direction).

Next, the arrangement of the correction optical element of this embodiment will be described with reference to FIG. FIG. 3 shows the arrangement of the correction optical elements formed on the transparent member 5 which is arranged substantially on the pupil plane of the projection optical system 21 of this example. In FIG. 3, the region 2 is substantially the pupil of the projection optical system 21. This is an area within the plane and limited by the aperture stop. Inside Region 2,
Four independent rectangular areas 3a to 3d surrounded by a two-dot chain line and shaded are areas where a direct image (Fourier transform image) of the illumination secondary light source is formed. The area where the direct image of the illumination secondary light source is formed can be moved to, for example, the area indicated by the broken line in accordance with the pattern of the reticle to be transferred, and the illumination secondary is provided in the area around the optical axis. No direct image of the light source is formed. In addition, reference numeral 1 denotes collectively 12 correction optical elements each composed of a phase type diffraction grating, and these 12 correction optical elements 1 are shown as 4 areas 3a to 3d in which a direct image of an illumination secondary light source is formed. Place it in the area outside.

In the present embodiment, these twelve correction optical elements 1 are arranged axially symmetrically along two orthogonal sides in the area surrounded by the areas 3a to 3d. The twelve correction optical elements 1 are three in number, one correction optical element near the intersection of the two orthogonal sides and two correction optical elements on both sides of one of the two sides. And the three correction optical elements shown in the same figure belong to the same group. For example, 3 shown by a black circle
The individual correction optical elements 1a to 1c belong to the same group.

Returning to FIG. 1, the drive unit 16 of this example has the drive shaft 15 in the Z direction parallel to the optical axis of the projection optical system 21, the X direction and the Y direction perpendicular to the optical axis of the projection optical system 21, and the projection optical system. System 2
It is possible to fix the drive shaft 15 in a state in which the drive shaft 15 is moved or rotated by a desired amount in the rotation direction (θ direction, see FIG. 3) and the tilt direction (φ direction) in the plane perpendicular to the optical axis of 1. It is configured to be able to. Therefore, the transparent member 5 inside the presser ring 13 connected to the drive shaft 15 also moves in the Z direction,
It can be positioned and fixed in the X, Y, θ and φ directions.

When assembling the projection optical system 21 of the present embodiment, first, the holding ring 12 which houses the transparent member 5 integrally with the holding ring 12 is incorporated into the inner surface of the lens barrel 11 of the projection optical system 21. Then, the drive shaft 15 extending from the drive device 16 is connected to the pressing ring 13 through the opening 14 formed in the side surface of the lens barrel 11. As a result, the transparent member 5 is supported so as to be movable and positionable.

An example of the configuration at the time of adjusting the alignment system in this embodiment will be described with reference to FIG. As shown in a simplified manner in FIG. 4, a transparent member 5 having 12 correction optical elements is arranged on the pupil plane of the projection optical system 21, and the transparent member 5 is driven by a drive device 16 via a drive shaft 15. Can be considered to be connected to. Alignment marks composed of a reticle mark and a window are formed adjacent to the four sides surrounding the exposure area of the reticle 6. Further, 19 denotes a wafer stage, a reference member 20 is provided in the vicinity of a wafer (not shown) on the wafer stage 19, and the reference mark 4 is provided on the surface of the reference member 20.
Form 2. The reference mark 42 is the same as a wafer mark made of a diffraction grating formed in the vicinity of each shot area on the wafer.

In FIG. 4, one alignment microscope (four in total) is provided for each of four alignment marks adjacent to each side surrounding the exposure area of the reticle 6.
3 is prepared. The reticle mark RM of the region adjacent to one of the four sides surrounding the exposure area of the reticle 6.
And the alignment system is adjusted using the window RW. For the reticle mark RM and the window portion RW, three correction optical elements 1a to 1c indicated by black circles on the transparent member 5 are used.

In this case, first, the reticle 6 is positioned. After that, the reference mark 42 on the reference member 20 on the wafer stage 19 side is previously reticle mark R on the reticle 6 by another alignment device (not shown) such as an off-axis alignment device (not shown) provided in the projection exposure apparatus.
Position with respect to M. When the alignment light beams 4a and 4b are emitted from the alignment microscope 43 in this state, when the correction optical element 1 is accurately positioned, the light beams 4a and 4b are deflected by the correction optical elements 1a and 1b, respectively. And illuminates the reference mark 42. Beat interference light 4 returned from the reference mark 42
c is deflected by the correction optical element 1c and returned to the alignment microscope 43 to obtain a good alignment signal.

However, the transparent member 5 on which the correction optical element 1 is formed is positioned within the tolerance range of mechanical design and assembly in a state of being connected to the driving device 16 via the driving shaft 15. The accuracy is insufficient as compared with the accuracy required by the alignment system. For example, if the correction optical element 1 is largely deviated in a plane perpendicular to the optical axis of the projection optical system 21, the alignment light beams 4a, 4 are originally generated.
b does not pass through the correction optical elements 1a and 1b. Therefore, the light flux for alignment reaching the image plane of the projection optical system 21 does not illuminate the reference mark 42, and an alignment signal cannot be obtained.

In such a case, the driving device 16 causes the transparent member 5 to be parallel-shifted or rotated substantially in the pupil plane of the projection optical system 21 to search for a state in which a good alignment signal can be obtained. At the time of this adjustment, if the diameter of the light flux for alignment is made large (thick), the search becomes easy. Since the position of the projection optical system 21 on the pupil plane corresponds to the angle on the image plane, a similar search is performed with the incident angle of the alignment light flux (the plane including the alignment light fluxes 4a and 4b incident on the reference mark 42). This can also be done by shaking the angle formed by this plane with respect to the plane perpendicular to the reference mark. Therefore, the correction optical element 1 may be first searched for by a method of tilting the light flux for alignment, and then the incident angle may be returned to the original setting value and the position of the transparent member 5 may be corrected based on the information.

Next, the transparent member 5 is moved to the X-axis through the drive shaft 15.
Direction, Y direction, Z direction, θ direction and φ direction (see FIG. 1)
The state of fluctuation of the light beams 4a and 4b for alignment with respect to the reference mark 42 when moved to the right will be described with reference to FIG. In this case, FIG. 5A shows the reference mark 42.
The same area 44 above is used for the alignment light beams 4a and 4
The state which b has irradiated is shown. The reference mark 42 is an alignment mark for the X direction and is formed of a diffraction grating having a predetermined pitch in the X direction. In this state,
When the transparent member 5 is moved in the X and Y directions, the light beam 4a
And 4b are coincident and illuminated area 44 is X
Direction and Y direction.

Further, when the transparent member 5 is rotated by a small angle in the θ direction around the optical axis of the projection optical system 21, as shown in FIG. 5A, the areas where the light beams 4a and 4b are coincidently illuminated. Reference numeral 44 moves in the X direction so as to cross the reference mark 42. Even if the transparent member 5 is slightly rotated in the φ direction which is the tilt direction, the region 44 hardly changes. Next, when the transparent member 5 is translated in the Z direction parallel to the optical axis of the projection optical system 21, the alignment light beams 4a and 4b irradiate the reference mark 42, as shown in FIG. 5B. The regions 45a and 45b are gradually separated in the X direction. In this case, the areas 45a and 45b
Beat interference light 4c effective only in the area 45c where and overlap
Occurs. If the wavelength of the light flux for alignment is changed significantly (for example, 100 nm or more), the position of the transparent member 5 in the Z direction may need to be changed significantly.

As shown in FIG. 5, the strongest beat interference light 4c is obtained when the region where the light beams 4a and 4b for alignment overlap on the reference mark 42 is the widest.
Alignment microscope 43 has the strongest strength and SN
It can be seen that a good alignment signal with a high ratio can be obtained. Therefore, by monitoring the intensity of the alignment signal while slightly displacing the transparent member 5 by parallel shift or rotation, and detecting the state when the intensity of the alignment signal becomes maximum, the two alignment It can be seen that the amount of overlapping of the light fluxes on the reference mark 42 is maximum, and that the correction optical element 1 of the transparent member 5 is accurately positioned. In order to maximize the overlapping amount of the two light beams, not only the positioning of the correction optical element 1 but also the
It is also necessary to perform optical adjustment such as focusing of the alignment microscope 43. However, since the position of the correction optical element 1 has already been optimized, these adjustments may be performed thereafter independently of the adjustment.

In the above description, the positioning adjustment of the correction optical element 1 is shown by a method using one alignment microscope 43. Since there are two incident light beams for alignment, it is possible in principle to determine the position and rotation angle of the plane of the transparent member 5, and the inclination of the surface can also be confirmed because the light beam shifts. However, it goes without saying that the positioning accuracy of the transparent member 5 can be further improved by using the alignment signals of a plurality of different alignment microscopes together.

The above-described positioning of the transparent member 5 on which the correction optical element 1 is arranged is performed when the projection optical system 21 is assembled and adjusted or when the correction optical element 1 is replaced, and thereafter fixed so as not to move. To be done. In order to keep the transparent member 5 as it is for a long period of time, the reference mark 42 of the reference member 20 is periodically moved into the exposure area of the projection optical system 21, and the alignment with respect to the reference mark 42 is performed. It is desirable that the driving device 16 automatically checks the signal strength and the like to confirm whether or not the correction optical element 1 is held in the correct position. The method is the same as the positioning method at the time of initial adjustment described above.

The work for such confirmation and readjustment may be performed periodically, or when the signal intensity of the alignment signal for the reference mark 42 falls below a certain level with respect to the initial value. You may do it.
In any case, it can be automatically performed by a program prepared in the control system of the projection exposure apparatus, and needless to say, it is preferable.

Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, the illumination 2 including a single area is used.
The present invention is applied to a projection exposure apparatus that can switch and use a secondary light source and a plurality of divided illumination secondary light sources. FIG. 6 shows the projection exposure apparatus of this example. In FIG. 6, the light source 22 to the illumination secondary light source system 23a or 2 are used.
Exposure light is supplied to 3b. These illumination secondary light source system 23
Each of a and 23b is composed of one fly-eye lens and a plurality of decentered fly-eye lenses, and the two illumination secondary light source systems 23a and 23b are switched by the drive system 25 by, for example, a turret system. Further, variable aperture stops 50 and 27 are arranged on the exit side of the illumination secondary light source systems 23a and 23b, and the openings of these variable aperture stops 50 and 27 serve as the illumination secondary light source. Variable aperture stop 50
And 27 are provided in the vicinity of positions where they are optically Fourier-transformed with the circuit pattern provided on the reticle 6.

The illumination secondary light source system 23a or 23b
The exposure light from the illumination secondary light source is appropriately condensed by the condenser lens system 24 to illuminate the reticle 6, and the pattern of the reticle 6 is transferred onto the wafer 9 via the projection optical system 21. Further, on the pupil plane of the projection optical system 21, any one transparent member among a large number of transparent members 5a, 5b, ..., 5x can be arranged by the driving system 46. In this case, twelve correction optical elements 1 are arranged on the first transparent member 5a in the same arrangement as in the example of FIG. 3, and a predetermined number of correction optical elements are arranged on the second transparent member 5b in different arrangements. The correction optical elements are arranged in different arrangements on the other transparent members as well.

When the illumination secondary light source system 23a for generating a single illumination secondary light source is arranged between the light source 22 and the condenser lens system 24, the main control system 26 drives the drive system 46. A predetermined transparent member is arranged on the pupil plane of the projection optical system 21 via the above. On the other hand, when the illumination secondary light source system 23b that generates the illumination secondary light source divided into a plurality of regions is arranged between the light source 22 and the condenser lens system 24, the main control system 26 causes the drive system 46 to operate. The first transparent member 5a having the arrangement shown in FIG. 3 is arranged on the pupil plane of the projection optical system 21 through the. With this mechanism, the alignment device can maintain the optimum arrangement of the correction optical element for the projection optical system 21 regardless of which type of secondary illumination light source is used.

Further, the drive system 46 of the present embodiment stores in advance the positioning state in which the best alignment signal is obtained for each of the transparent members 5a to 5x, and the selected transparent members are stored in the stored state. Position.
In this case, the positioning state in which the best alignment signal is obtained can be obtained by the adjusting method of the embodiment shown in FIG. Thereby, highly accurate alignment can always be performed.

The present invention is not limited to the above-described embodiments, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0052]

According to the present invention, the reference mark formed on the stage is used to generate a light reception signal which is actually used during alignment, and the state of this light reception signal can be observed for positioning, so that the correction optical element can be used. There is an advantage that the holding substrate on which is formed can be positioned easily and with high accuracy. Further, when the monitor means and the positioning means are provided, for example, by periodically inspecting and adjusting the positioning state of the holding substrate, misalignment due to the positional deviation of the holding substrate due to aging etc. There is also an advantage that can be prevented.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing a projection optical system of a projection exposure apparatus to which an embodiment of an alignment apparatus adjusting method according to the present invention is applied.

FIG. 2 is a cross-sectional view in the vicinity of a pupil plane of the projection optical system of FIG.

FIG. 3 is a plan view showing the arrangement of correction optical elements on the transparent member of FIG.

4 is a perspective view of a main part showing an arrangement when adjusting an alignment system using the projection optical system of FIG. 1. FIG.

FIG. 5 is a diagram for explaining a change in an irradiation position of a light flux for alignment on the reference mark 42 when the transparent member 5 is moved.

FIG. 6 is a configuration diagram showing a projection exposure apparatus according to a second embodiment of the present invention.

FIG. 7 is a configuration diagram showing a main part of a projection exposure apparatus provided with an alignment apparatus according to the applicant's prior application.

[Explanation of symbols]

 1 12 Correction Optical Elements 1a to FIG. 1c Correction Optical Elements 4a, 4b Alignment Luminous Beam 4c Interference Beam 5 Transparent Member 6 Reticle 11 Lens Barrel 12 Holding Ring 13 Holding Ring 15 Drive Shaft 16 Drive Device 19 Wafer Stage 20 Reference Member 21 Projection Optical System 42 Reference Mark 43 Alignment Microscope

Claims (2)

[Claims] 1. A photosensitive substrate on which an alignment mark is formed by placing the pattern on a mask on which an alignment mark and a transfer pattern are formed on a stage under exposure light via a projection optical system. An irradiation device provided in an exposure device for transferring, irradiating alignment light having a wavelength band different from that of the exposure light to the alignment mark of the photosensitive substrate via the projection optical system, and the alignment light from the alignment mark to the projection device. Detecting means for generating a received light signal by detecting through an optical system, and chromatic aberration generated by the projection optical system with respect to the alignment light, which is formed on a holding substrate arranged substantially in the pupil plane of the projection optical system. And an alignment mark formed on the mask and the photosensitive substrate with the alignment light. A method of adjusting the positioning state of the holding substrate in an alignment device that performs relative alignment between the mask and the photosensitive substrate by forming a reference mark on a stage on which the photosensitive substrate is mounted, In a state where the reference mark is set at a predetermined position in the exposure area of the projection optical system, the reference mark is illuminated by the irradiation means with the alignment light through the projection optical system, and alignment from the reference mark is performed. A method for adjusting an alignment apparatus, wherein light is detected by the detection means via the projection optical system, and the holding substrate is positioned so that a light reception signal generated by the detection means is in a predetermined state. .. 2. The alignment device is provided with monitor means for monitoring a light receiving signal of the detecting means and positioning means for positioning the holding substrate, and the monitor means detects the detection signal of the detecting means in a predetermined state. 2. The alignment apparatus adjusting method according to claim 1, wherein the holding substrate is repositioned by the positioning means when it is detected that the holding substrate is out of position.