JPH10284369A - Aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect at least a reticle mark position or a wafer mark position on a reticle without making an area lighted with exposure light larger than that in exposure. SOLUTION: During exposure, under exposure light IL which has passed through a capacitor lens 12, the pattern of a reticle R is transferred on a wafer W through a projection optical system PL. During alignment, deflection angle prisms 40A and 40B and a rhombic prism 43 are arranged between a capacitor lens 12 and the reticle R. Then, the reticle marks 33A and 34A are lighted with exposure light IL whose optical path is horizontally shifted by the rhombic prism 43, and a wafer mark 37A is lighted with exposure light which has passed a window between the reticle marks through the projection optical system PL. Reflected light from the marks are received by an alignment sensor 39 including a beam splitter 45, and the positions of the marks are detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used in a lithography process for manufacturing, for example, a semiconductor device, an imaging device (such as a CCD), a liquid crystal display device, or a thin-film magnetic head. The present invention relates to an exposure apparatus provided with a mark position detection system for detecting at least one of the position of the alignment mark of the mask and the position of the alignment mark on the photosensitive substrate from above.

[0002]

2. Description of the Related Art In an exposure apparatus such as a stepper or a proximity type exposure apparatus used in manufacturing a semiconductor element or the like, a wafer on which a photosensitive material as a photosensitive substrate is coated is used. It is necessary to perform high-precision alignment (alignment) between a circuit pattern already formed in each shot area and a reticle pattern as a mask to be transferred from now on. Therefore, these exposure apparatuses include an alignment sensor (mark position detection system) for detecting the amount of misalignment between the reticle and the wafer,
And an alignment mechanism including a stage mechanism for positioning the reticle and the wafer based on the detection result.

With such a conventional alignment sensor,
One of the methods capable of detecting the amount of positional deviation between the reticle and the wafer with high accuracy is to use an alignment mark (reticle mark) on the reticle from the reticle or via a projection optical system if the reticle has a projection optical system. This is a TTR (through-the-reticle) method for detecting a positional shift amount from an alignment mark (wafer mark) on a wafer. This T
TR type alignment sensors are classified into two types, (a) self-illumination type and (b) exposure light type, depending on what kind of illumination light is used.

[0004] The self-illumination type shown in (a) is a system in which an illumination light source that independently generates illumination light having the same wavelength as the exposure light is used, and the mark to be detected is illuminated by the illumination light from the illumination light source. On the other hand, the exposure light utilization type shown in (b) uses exposure light emitted from an illumination optical system for exposure to an illumination area on a reticle as illumination light. In this method, a half mirror is provided above the reticle. The exposure light reflected by the mark to be detected is received through the half mirror.

[0005]

The conventional TT as described above
Among the R-type alignment sensors, in the self-illumination type (a), illumination conditions are different between exposure light and illumination light for alignment. When the illumination conditions are different as described above, a deviation occurs between the amount of positional deviation between the reticle and the wafer under the illumination light for alignment and the amount of positional deviation under the exposure light. May cause an overlay error. In particular, when the coherence factor (so-called σ value) of the illumination optical system for exposure is changed, or when deformed illumination is used, the focus position, distortion, etc. of the projected image are compared with those under normal illumination conditions. May be slightly shifted, and a self-illumination type may cause an overlay error. In order to avoid this, the illumination conditions of the illumination optical system for the alignment sensor may be set as close as possible to the illumination optical system for exposure, but for that purpose, the illumination optical system for the alignment sensor becomes complicated and large. I will. Furthermore, even when the illumination optical system for exposure is switched to modified illumination or the like, it is difficult to make the illumination conditions of both illumination optical systems almost the same.

On the other hand, in the exposure light type shown in FIG. 1B, the illumination conditions are the same at the time of exposure and at the time of alignment. However, the conventional exposure light utilization type illuminates the mark to be detected with the exposure light as it is, and takes in the reflected light from the mark with a half mirror, so that the maximum illumination area of the illumination optical system for exposure is used. It is necessary to expand the area (effective illumination area).
That is, in general, the reticle mark is often outside the pattern region of the reticle, and the wafer mark is often in the region between the shot regions on the wafer. Need to be irradiated. If the illumination area of the exposure light is widened in this way, there is a disadvantage that the illumination optical system for exposure becomes large.

In these exposure apparatuses, a fly-eye lens is usually used as an optical integrator for improving the uniformity of the illuminance distribution. Is conjugate, the effective illumination area on the reticle is an area such as a rectangle similar to the cross-sectional shape of each lens element of the fly-eye lens. Therefore, if the effective illumination area is enlarged by changing the cross-sectional shape of each lens element of the fly-eye lens for mark detection, the illuminance of exposure light is greatly reduced, and the throughput (productivity) of the exposure process is reduced. There was also the inconvenience of lowering.

In view of the above, the present invention provides an exposure apparatus having a detection system capable of detecting at least one position of a reticle mark or a wafer mark from a reticle without making an illumination area of exposure light wider than at the time of exposure. It is intended to provide a device.

[0009]

An exposure apparatus according to the present invention comprises an illumination optical system (1) for illuminating a predetermined illumination area (13) on a mask (R) on which a transfer pattern is formed with exposure light.
To 12) and an alignment mark (33) formed on the mask (R) using illumination light in the same wavelength range as the exposure light.
A) or a mark position detection system (45-47) for detecting at least one position of the alignment mark (37A) formed on the photosensitive substrate (W). An exposure apparatus that aligns the mask with the photosensitive substrate based on the detection result and transfers the pattern of the mask onto the photosensitive substrate under the exposure light. A light beam deflecting member (43) for deflecting a part of the exposure light applied to the mask to an area outside the illumination area (13) is provided, and the exposure light deflected by the light beam deflecting member is illuminated by a mark position detection system. It is used as light.

According to the present invention, for example, as shown in FIG. 1, if there is a mark (33A) to be detected outside the illumination area (13) at the time of exposure, the illumination area (13) A part of the incoming exposure light is a light beam deflecting member (43)
The mark (33A) is deflected upward through the mark (33A), and the exposure light deflected in this way is transmitted through the beam splitter (45) of a part of the mark detection system, for example.
A) Illuminate. Then, the exposure light reflected from the mark (33A) is guided to the observation system of the mark detection system via the beam splitter (45), so that the position of the mark (33A) can be increased without expanding the illumination area of the exposure light. Can be detected.

In this case, the optical path length adjusting members (40A, 40A) for bringing the optical path length of the light beam deflected by the light beam deflecting member (43) closer to the optical path length of the other exposure light.
It is desirable to provide B). Thereby, the optical path length of the exposure light irradiated on the mask (R) via the light beam deflecting member (43) is closer to the optical path length of the exposure light irradiated directly on the mask (R) from the illumination optical system. Therefore, the mark to be detected can be illuminated in an illumination state closer to the illumination state at the time of exposure.

It is desirable that the optical path length adjusting members (40A, 40B) adjust the telecentricity of the exposure light applied to the mark to be detected via the light beam deflecting member (43). In the present invention, the optical path of the exposure light is laterally shifted. For example, when the mark (37A) on the photosensitive substrate (W) is detected via a projection optical system, the telecentricity on the photosensitive substrate is detected. In order to satisfy the condition (1), it may be necessary to change the incident angle of the principal ray of the exposure light on the corresponding mask (R). Further, the incident angle of the exposure light to the mask (R) may change due to a manufacturing error of the light beam deflecting member (43) or the like. In such a case, the telecentricity of the exposure light is controlled by the optical path length adjusting members (40A, 40B) so that the chief ray of the exposure light is perpendicular to the alignment mark (37A) on the photosensitive substrate (W). , The position of the alignment mark (37A) is detected with high accuracy.

It is desirable that the light beam deflecting member (43) be retractable with respect to the optical path of the exposure light. By retracting the light beam deflecting member (43) during exposure, the light beam deflecting member (43) does not hinder the exposure.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of an exposure apparatus according to the present invention will be described with reference to FIGS.
In this example, the present invention is applied to a step-and-scan type projection exposure apparatus that sequentially transfers a reticle pattern image to each shot area on a wafer by synchronously scanning a reticle and a wafer with respect to a projection optical system. It was done.

FIG. 1 shows a schematic configuration of a projection exposure apparatus of this embodiment. In FIG. 1, light is emitted from an exposure light source 1 such as a KrF excimer laser light source (oscillation wavelength of 248 nm) or an ArF excimer laser light source (oscillation wavelength of 193 nm). The exposure light IL made of the laser light is incident on the fly-eye lens 4 for uniforming the illuminance distribution via the mirror 2 and the beam shaping optical system 3 and the like. The incident surfaces of a number of lens elements constituting the fly-eye lens 4 are conjugate with the pattern surface of the reticle to be transferred, and the cross-sectional shapes of these lens elements are similar to the effective illumination area on the reticle. Also, an aperture stop plate 5 is provided on the exit surface of the fly-eye lens 4.
Are rotatably arranged, a normal aperture stop having a circular aperture on the periphery of the aperture stop plate 5, an aperture stop having a small circular aperture for a small σ value (coherence factor), an annular aperture stop, and, for example, four aperture stops. Various aperture stops ([sigma] stops) such as an aperture stop for deformed illumination in which small circular apertures are arranged axially symmetrically are arranged, and rotated under a command of a main controller 14 for controlling the operation of the entire apparatus. By rotating the aperture stop plate 5 via the motor 6, a desired aperture stop can be set on the exit surface of the fly-eye lens 4.

Exposure light IL that has passed through the aperture stop on the exit surface of the fly-eye lens 4 is exposed to a first relay lens 7, a variable field stop (reticle blind) 8, a second relay lens 10, and a mirror 11 for bending the optical path. , And the condenser lens 12 illuminates the rectangular illumination area 13 on the pattern surface (lower surface) of the reticle R with a uniform illuminance distribution. The above-described exposure light source 1 to condenser lens 12 constitute an illumination optical system for exposure. The arrangement surface of the variable field stop 8 is conjugate with its pattern surface, and the shape of the illumination area 13 is defined by the main controller 14 controlling the shape of the opening of the variable field stop 8 via the driving device 9. . However, the largest possible area of the illumination area 13 (effective illumination area)
Is defined by the cross-sectional shape of each lens element of the fly-eye lens 4, and the variable field stop 8 further defines an illumination area within its effective illumination area. As the exposure light IL, a harmonic of a metal vapor laser or a YAG laser, a bright line of a mercury lamp (such as an i-line with a wavelength of 365 nm), or the like can be used in addition to the excimer laser light.

At the time of exposure, the image of the pattern in the illumination area 13 on the reticle R under the exposure light IL is projected through a telecentric projection optical system PL on both sides (or one side on the wafer side) to a projection magnification β (β is For example, 1/4, 1/5, etc.), a rectangular exposure area on the wafer W coated with the photoresist is projected and exposed. Hereinafter, the optical axis A of the projection optical system PL will be described.
The description will be made by taking the Z axis parallel to X, the X axis parallel to the plane of FIG. 1, and the Y axis perpendicular to the plane of FIG. 1 in a plane perpendicular to the Z axis.

In this embodiment, the reticle R is held on a reticle stage 15, and the reticle stage 15 two-dimensionally positions the reticle R on a reticle base 16 in a plane perpendicular to the optical axis AX. Direction (scanning direction)
The reticle R can be scanned at a predetermined speed. Reticle stage 1 measured by moving mirror 17 m on reticle stage 15 and laser interferometer 17
The two-dimensional coordinates 5 are supplied to the main controller 14, and the main controller 14 controls the position and speed of the reticle stage 15 via a driving unit such as a linear motor based on the supplied coordinates.

On the other hand, the wafer W is mounted on a wafer stage 19 via a wafer holder (not shown).
The wafer stage 19 is configured to position the wafer W in the X direction and the Y direction and to scan the wafer W in the Y direction at a constant speed. The wafer stage 19 controls the position (focus position) of the wafer W in the Z direction by an autofocus method. The two-dimensional coordinates of the moving mirror 20m on the wafer stage 19 and the wafer stage 19 measured by the external laser interferometer 20 are supplied to the main controller 14, and the main controller 14 is driven via a drive unit such as a drive motor. The operation of the wafer stage 19 is controlled. During scanning exposure, in synchronism with being scanned at a velocity V _R to the reticle R is + Y direction (or the -Y direction) via the reticle stage 15, one shot area on the wafer W via the wafer stage 19 speed β · V _R (β is the projection magnification) is scanned in the -Y direction (or + Y direction).

In the vicinity of the wafer W on the wafer stage 19, a reference mark member 22 having a surface at the same height as the surface of the wafer W is fixed. A mark 23 is formed. Next, the alignment sensor of the projection exposure apparatus of this embodiment will be described in detail. In this example, an alignment sensor of a TTR method and an image processing method is used. In order to perform the alignment, alignment marks (reticle mark and wafer mark) are formed on reticle R and wafer W, respectively.

FIG. 2A shows an arrangement of reticle marks on the reticle R. In FIG.
Outside of the + X direction of the pattern region 31 of FIG.
Two Y-axis reticle marks 33A and 34A each formed of an AND space pattern are formed across a window 35A. In this case, the reticle marks 33A and 34A and the window 35A are formed in a region deviated in the + X direction from the effective illumination region including the illumination region 13 of the exposure light IL by the exposure illumination optical system. Further, the projection optical system P of FIG.
Assuming that the maximum area that can be projected onto the wafer W by L is a circular effective field of view 32, the reticle marks 33A and 34A
The window portion 35A is within the effective visual field 32.
However, at least only the window 35A has an effective visual field of 3
It only has to be within 2. Two Y-axis reticle marks 33B and 34B are formed symmetrically with respect to the reticle mark and a straight line parallel to the Y axis passing through the optical axis AX and outside the pattern region 31 in the −X direction with the window 35B interposed therebetween. Have been. Although not shown, an X-axis reticle mark formed of a line-and-space pattern arranged at a predetermined pitch in the X direction is also formed.

FIG. 2B shows an arrangement of wafer marks attached to one shot area 36 on the wafer W. In FIG. 2B, the shot mark 36 is adjacent to the shot area 36 in the -X direction. A Y-axis wafer mark 37A in which convex portions and concave portions are arranged at a predetermined pitch in the Y direction, and an X-axis wafer mark 38A in which convex portions and concave portions are arranged at a predetermined pitch in the X direction are formed. I have. Further, a Y-axis wafer mark 37B and an X-axis wafer mark 38B are formed symmetrically with the pair of wafer marks and adjacent to the shot area 36 in the + X direction. With the pattern region 31 of the reticle R and the shot region 36 on the wafer W aligned, the windows 35A, 3A on the reticle R are aligned.
The center of 5B and the centers of wafer marks 37A and 37B are substantially conjugate.

When performing alignment of the shot area 36 by the TTR method, the first reticle marks 33A, 34A and the second reticle mark 33 on the Y axis on the reticle R are used.
B, 34B and the amount of displacement in the Y direction between the corresponding wafer mark 37A and the wafer mark 37B of the shot area 36 on the wafer W are detected by the corresponding alignment sensor, and similarly, an X-axis (not shown) on the reticle R X-axis wafer mark 38 on wafer W corresponding to reticle mark
The amount of displacement in the X direction with respect to A and 38B is detected by the corresponding alignment sensor, and exposure is performed with the results of these detections falling within predetermined allowable ranges. Hereinafter, an alignment sensor for detecting the amount of displacement in the Y direction between reticle marks 33A and 34A and corresponding wafer mark 37A will be described.

In FIG. 1, a TTR type alignment sensor 39 is disposed above reticle marks 33A and 34A of reticle R. This alignment sensor 3
9 is an optical axis AX above the reticle marks 33A and 34A.
The beam splitter 45 is arranged so as to be inclined outward at 45 ° to face the outside, an objective optical system 46 for condensing a light beam from the beam splitter 45, and an image formed by the objective optical system 46. And an imaging element such as a two-dimensional CCD for imaging. Reticle mark 33 of this example
Since A and 34A are outside the effective illumination area, the beam splitter 45 is also located outside the optical path of the exposure light toward the effective illumination area.

In order to use a part of the exposure light IL as illumination light for the alignment sensor 39 at the time of alignment, the pair of wedge-shaped deflection prisms 40A and 40B is viewed above the alignment sensor 39 from the Y direction. A rhombic prism 43 having a rhombic shape is arranged. In this case, the deflection prisms 40A and 40B are fixed to a support arm 42 via a rotation device 41 that can individually rotate these prisms,
The rhombic prism 43 is also fixed to the support arm 42, and the support arm 42 is attached to the slider 44 so as to be able to move in and out in the Y direction. Then, at the time of exposure, the support arm 42 is pulled into the slider 44 so that the deflection prism 40
A and 40B and the rhombic prism 43 can be retracted from the optical path of the exposure light IL. At the time of alignment, the support arm 42 is pulled out from the slider 44 to thereby provide the deflection prisms 40A and 40A.
It is configured such that the incident surfaces of B and the rhombic prism 43 can be set in the optical path of the exposure light IL.

As shown in FIG. 1, the deflection prisms 40A and 40B and the rhombic prism 43 are used for alignment.
Is set in the optical path of the exposure light IL, the exposure light IL traveling from the condenser lens 12 to the reticle R.
Is incident on the incident surface of the rhombic prism 43 via the deflection prisms 40A and 40B arranged in order along the optical axis AX. The exposure light that has entered the rhombic prism 43 as described above is totally reflected twice on opposing inclined surfaces inside the rhombic prism 43, then exits from the bottom surface of the rhombic prism 43 and travels toward the beam splitter 45. Then, a part of the exposure light transmitted through the beam splitter 45 illuminates the reticle marks 33A and 34A of the reticle R, and the remaining exposure light passes through the window 35A of the reticle R (see FIG. 2A).
Wafer mark 37 on wafer W via projection optical system PL
Illuminate A.

The exposure light reflected by the wafer mark 37A passes through the projection optical system PL again and passes through the window 35 of the reticle R.
An image of the wafer mark 37A is formed on A. The exposure light returned to the window 35A and the reticle marks 33A,
The exposure light reflected by 34A is directed to beam splitter 45, and the exposure light reflected by beam splitter 45 passes the image of wafer mark 37A and reticle marks 33A and 34A onto the imaging surface of image sensor 47 via objective optical system 46. Form. The image pickup signal of the image pickup device 47 is supplied to an image processing unit in the main control device 14, and the image processing unit processes the image pickup signal to move the center of the wafer mark 37A relative to the center of the reticle marks 33A, 34A in the Y direction. Find the amount of displacement. Similarly, the displacement amount between the other marks is also obtained,
The reticle R and the wafer W are aligned with each other based on the positional shift amounts.

As described above, in the present embodiment, when the displacement between the reticle R and the wafer W is detected using the alignment sensor 39, the deflection prism 4 is moved by the slider 44.
0A, 40B and a rhombic prism 43 are set in the optical path of the exposure light IL, and the reticle mark and the wafer mark to be detected are illuminated by a light beam obtained by deflecting a part of the exposure light IL. Therefore, for example, even when the aperture stop plate 5 is rotated to switch the aperture stop to an aperture stop for a small σ value, an annular stop, an aperture stop for a modified illumination, or the like, the gap between the corresponding marks is changed under the switched illumination condition. Since the amount of displacement can be detected, high overlay accuracy can be obtained even if the distortion or the like of the projection optical system PL changes depending on the illumination conditions. Further, since it is not necessary to extend the effective illumination area of the exposure light IL to outside the pattern area of the reticle R, the illumination optical system for exposure is downsized. Further, since the illuminance of the exposure light IL at the time of exposure is high, the exposure time for each shot area of the wafer W can be shortened, and the throughput of the exposure process can be improved.

When quantitatively estimating how much the illuminance increases, in FIG. 2A, the size of the illumination area 13 in the step-and-scan method is, for example, in the non-scanning direction (X direction). Is about 100 mm, and the width in the scanning direction (Y direction) is about 30 mm. On the other hand, reticle marks 33A and 34A correspond to pattern area 3 of reticle R.
For example, it is formed at a position about 5 mm away from 1 in the X direction. Therefore, if the reticle marks 33A, 34A (and the reticle marks 33B, 34B on the opposite side) are to be illuminated with the exposure light without using the optical path deflecting member, the width of the effective illumination area by the exposure light in the X direction is reduced to about 110 mm. There is a need to. On the other hand, in this example, since the rhombic prism 43 is used as an optical path deflecting member, the width of the effective illumination area in the X direction may be approximately 100 mm. Therefore, the area of the effective illumination area in this example is 10% as compared with the conventional example.
Since it can be made as narrow as possible, the illuminance of the exposure light can be increased by about 10%.

Next, the deflection prisms 40A and 40B shown in FIG.
Will be described with reference to FIG. FIG. 3 is an enlarged view showing the periphery of the rhombic prism 43 of FIG.
In FIG. 7, the two deflection prisms 40A and 40B are replaced by one optical member 40 made of a parallel plate glass having a thickness d2 in the optical axis direction (Z direction). In addition, the rhombic prism 4
Assuming that the thickness in the optical axis direction between the top surface and the bottom surface of 3 is d1 and the interval in the X direction perpendicular to the optical axis of the opposed inclined surface of the rhombic prism 43 (ie, the lateral shift amount of the exposure light) is H, Member 4
Let n be the refractive index of the 0 and rhombic prism 43 with respect to the exposure light.

In FIG. 3, when the center of the incident surface of the optical member 40 is point A and the optical member 40 and the rhombic prism 43 are not provided, the exposure light 48 incident on the point A in parallel to the Z axis.
Enters the point B on the pattern surface of the reticle R as it is. At this time, the optical path length S1 from the point A to the point B of the exposure light 48 can be expressed as follows, where δ is a length other than d1 and d2.

S1 = d1 + d2 + δ (1) On the other hand, if only the rhombic prism 43 is set in the optical path of the exposure light 48, the exposure light 48 passing through the point A will be reflected at the point on one inclined surface of the rhombic prism 43. After passing through D and a point E on the other inclined surface, the light passes through the beam splitter 45 in parallel with the Z axis and is incident on a point C on the reticle mark 33A. Point B
The distance between the reticle mark 33A and the point C is H,
4A is located outside the effective illumination area 13A. In this state, since the difference between the optical path length of the exposure light 48 from the point A to the point C and the optical path length of the equation (1) may be large, the optical member 40 is further moved between the point A and the point D. When arranged, the air-converted length S2 obtained by converting the length of the optical path when the exposure light 48 reaches the point C through the optical member 40 and the rhombic prism 43 into the length in the air is as follows. .

S2 = (d1 + d2 + H) / n + δ (2) Accordingly, the condition for making this equal to the optical path length S1 of the equation (1) is as follows. d1 + d2 = H / (n-1) (3) Therefore, in this example, the optical member 40 (deflection prism 40A,
The thickness d1 of 40B), the thickness d2 of the rhombic prism 43, and the lateral shift amount H of the exposure light by the rhombic prism 43 are set so as to satisfy the condition of Expression (3). As a result, the optical path length of the exposure light illuminating the reticle marks 33A and 34A becomes equal to the optical path length at the time of exposure. Can be detected.

Returning to FIG. 1, the total thickness of the deflection prisms 40A and 40B above the rhombic prism 43 is adjusted so as to satisfy the equation (3). Furthermore, the deflection prism 40
Since A and 40B are wedge-shaped, respectively, by rotating each, it is possible to deflect the incident exposure light by an arbitrary angle in an arbitrary two-dimensional direction within a predetermined angle range. In this example, the rotation angles of the deflection prisms 40A and 40B are controlled via a rotation device 41, so that the reticle marks 33A and 33A pass through a rhombic prism 43.
The incident angle (telecentricity) of the principal ray of the exposure light for illuminating the window 4A and the window 35A is adjusted.

In order to illuminate the wafer mark 37A on the wafer W with the exposure light in a telecentric condition even when there is an aberration of the projection optical system PL, a corresponding position (the window 35A) on the reticle R is required. This is because it is necessary to illuminate slightly out of telecentric conditions. That is, the condition of the incident angle of the exposure light at the window 35A on the reticle R for performing telecentric illumination on the wafer W, and the exposure light at the incident position on the reticle R without the rhombic prism 43 Is slightly different from the condition of the incident angle of the exposure light, and the deviation of the incident angle of the exposure light may occur due to a manufacturing error of the rhombic prism 43 and the beam splitter 45 for laterally shifting the exposure light. Square prism 4
The wafer mark 37A on the wafer W is always illuminated under telecentric conditions by adjusting the incident angle of the exposure light at 0A and 40B. Therefore, even if the height of the wafer W changes, the position of the wafer mark 37A can be detected with high accuracy.

A device for moving the alignment sensor 39 shown in FIG. 1 may be provided so that the alignment sensor 39 detects a reticle mark at another position on the reticle R and a corresponding wafer mark. In this case, the slider 44 may be configured to be further movable in the Y direction, and the exposure light may be supplied onto the beam splitter 45 of the alignment sensor 39 after the movement. Further, when the position of the reticle mark to be detected changes, the condition of the inclination angle of the principal ray of the exposure light for performing telecentric illumination on the wafer W may change. When it changes, the rotation angle of the deflection prisms 40A and 40B may be controlled via the rotation device 41 to correct the inclination angle of the principal ray of the exposure light. This is particularly effective when the illumination optical system for exposure is not telecentric.

The alignment sensor 39 shown in FIG.
In addition to the wafer mark 37A, the position of the reference mark 23 on the reference mark member 22 can be detected. The detection of the position of the reference mark 23 is performed, for example, when measuring a baseline amount, which is an interval between the detection center of the alignment sensor 39 and the center of the pattern image of the reticle R. In addition, the alignment sensor 39 of the present example includes a projection optical system PL
, The image of the wafer mark 37A on the wafer W is captured, and by calculating the contrast of the image captured in this manner, the projection optical system P on the surface of the wafer W is calculated.
It is also possible to detect the amount of defocus from the image plane of L. Further, instead of simply taking an image of the wafer mark 37A with the alignment sensor 39, for example, near the optical Fourier transform plane (pupil plane) of the test surface, the light beam is divided into two by a straight line passing through the optical axis in different directions. Then, the amount of defocus on the surface of the wafer W may be detected by detecting the amount of lateral shift between the image forming positions of these two light beams. Since the detection of the defocus amount is also sensitive to a change in the imaging characteristics of the projection optical system PL due to the illumination state of the illumination optical system, the exposure condition can be used as it is to detect the defocus amount. There is an advantage that a corresponding accurate defocus amount can be detected.

As the light beam deflecting member, two mirrors 49A and 49B arranged in a parallelogram may be used as shown in FIG. 4 instead of the rhombic prism 43 of FIG. That is, in FIG. 4, the optical member 40 having a thickness d2
The exposure light 48 that has passed through the optical axis in parallel to the optical axis
The light is reflected by the mirror 49A inclined at 5 °, and travels toward the mirror 49B parallel to the mirror 49A.
Exposure light 48 reflected by is directed to reticle R in FIG.
Also in this case, the distance between the mirrors 49A and 49B in the direction perpendicular to the optical axis (the lateral shift amount of the exposure light) is H. FIG.
In the case of (2), assuming that the optical path length of the exposure light 48 without the optical member 40 and the mirrors 49A and 49B is (d2 + δ ′), the air path length when the optical member 40 and the mirrors 49A and 49B are present is converted into air. Since the length is (d2 / n + H + δ ′), the optical member 4 for equalizing the optical path length of the exposure light 48 between the case where the mirrors 49A and 49B are not provided and the case where the mirrors 49B are provided.
The condition of the thickness d2 of 0 is as follows.

D2 = nH / (n-1) (4) By satisfying this condition, the illumination condition at the time of alignment becomes closer to the illumination condition at the time of exposure. Next, a second embodiment of the present invention will be described with reference to FIG. In the present embodiment, the present invention is applied to a so-called proximity type exposure apparatus that performs exposure by bringing a reticle and a wafer close to each other without using a projection optical system. In FIG. 5, portions corresponding to those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 5 shows a main part of the exposure apparatus of this embodiment. In FIG. 5, a wafer W is held on a wafer stage 51, and the wafer stage 51 performs two-dimensional positioning of the wafer W. The height of the wafer W is also adjusted. A reticle R is arranged above the wafer W at a predetermined interval via a reticle stage (not shown). At the time of exposure, the reticle R is illuminated by exposure light IL from the condenser lens 12 of the illumination optical system. Originally, the pattern of reticle R is transferred onto wafer W.

A reticle mark 52 is formed outside the effective illumination area on the pattern surface (lower surface) of reticle R,
Wafer marks 53 are formed at opposing positions on the wafer W, and reticle marks and wafer marks are formed at other positions (not shown). The beam splitter 45, the objective optical system 46, and the
And an alignment sensor 39 including an image sensor 47. Further, from the condenser lens 12 toward the reticle R, the deflection prisms 40A and 40B and the rhombic prism 43 are disposed so as to be retractable with respect to the optical path of the exposure light IL by the slider 44, and these are arranged on the optical path of the exposure light IL. When arranged, a part of the exposure light is guided to the beam splitter 45 via the rhombic prism 43.

Also in this example, using an illumination optical system for exposure,
In addition, the reticle mark 52 and the wafer mark 53 are illuminated with exposure light without widening the effective illumination area, and the amount of displacement between the two can be detected via the alignment sensor 39.
Therefore, even if the illumination condition changes, the amount of displacement can be accurately detected, so that a high overlay accuracy can always be obtained.

In the above-described embodiment, FIGS.
As shown in FIG. 7, the deflection prisms 40A and 40B are arranged to correct the optical path length when the exposure light is shifted laterally, but if the amount of the shift is small, it is practical to omit them. No problem. In particular, when the exposure light source is at infinity on the reticle R, that is, when the illumination optical system for exposure is telecentric, there is almost no problem. By omitting the deflection prisms 40A and 40B in such a manner, the device configuration can be simplified.

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted without departing from the gist of the present invention.

[0045]

According to the present invention, the light beam deflecting member for deflecting the exposure light so that it can be used as the illumination light for the mark position detection system is provided. There is an advantage that the position of at least one of the alignment mark on the mask or the alignment mark on the photosensitive substrate can be detected from above the mask without performing. Therefore, highly accurate position detection corresponding to a change in a transferred image due to a difference in the illumination condition of the exposure light becomes possible. Also,
Since a unique illumination system is not required for the mark position detection system, there is an advantage that the configuration of the apparatus is simplified.

In the case where an optical path length adjusting member is provided for bringing the optical path length of the light beam deflected by the light beam deflecting member closer to the other optical path length of the exposure light, the illumination conditions for detecting the mark position are provided. Can be brought closer to the illumination conditions at the time of exposure, so that the position of the mark can be detected with higher accuracy. Further, when adjusting the telecentricity of the illuminating light applied to the mark to be detected through the light beam deflecting member by the optical path length adjusting member, for example, when a projection optical system is used, the photosensitive substrate may be placed on the photosensitive substrate. By satisfying the condition of telecentricity in the above, the detection accuracy of the alignment mark on the photosensitive substrate can be improved.

When the light beam deflecting member is retractable with respect to the optical path of the exposure light, the light beam deflecting member is retracted at the time of exposure so that the light beam deflecting member does not hinder the exposure. .

[Brief description of the drawings]

FIG. 1 is a partially cut-away configuration view showing a first embodiment of an exposure apparatus according to the present invention.

2A is a plan view showing an arrangement of reticle marks on a reticle R in FIG. 1, and FIG. 2B is a plan view showing an arrangement of wafer marks on a wafer W in FIG.

FIG. 3 is a partially enlarged view showing a configuration around a rhombic prism 43 in FIG. 1;

FIG. 4 is a configuration diagram showing an optical member that can be used instead of the rhombic prism 43 of FIG. 1;

FIG. 5 is a configuration diagram illustrating a main part of a second embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 exposure light source 4 fly-eye lens 5 aperture stop plate 12 condenser lens R reticle PL projection optical system W wafer 14 main controller 19 wafer stage 33A, 34A reticle mark 35A window 37A wafer mark 39 alignment sensor 40A, 40B deflection prism 43 Diamond prism 44 Slider 45 Beam splitter 46 Objective optical system 47 Image sensor

Claims (4)

[Claims] 1. An illumination optical system for illuminating a predetermined illumination area on a mask on which a transfer pattern is formed with exposure light, and an illumination optical system formed on the mask using illumination light in the same wavelength range as the exposure light. A mark position detection system that detects at least one position of the alignment mark or the alignment mark formed on the photosensitive substrate, wherein the mask and the mark are formed based on a detection result of the mark position detection system. In an exposure apparatus that performs alignment with a photosensitive substrate and transfers the pattern of the mask onto the photosensitive substrate under the exposure light, the exposure light applied to the mask from the illumination optical system An exposure apparatus, comprising: a light beam deflecting member for deflecting a part of the light beam to an area outside the illumination area; and using exposure light deflected by the light beam deflecting member as illumination light of the mark position detection system. 2. The exposure apparatus according to claim 1, wherein an optical path length of the light beam deflected by the light beam deflecting member is:
An exposure apparatus, further comprising an optical path length adjusting member for approaching the optical path length of the exposure light. 3. The exposure apparatus according to claim 2, wherein the optical path length adjusting member adjusts telecentricity of illumination light applied to the mark to be detected via the light beam deflecting member. Exposure equipment. 4. The exposure apparatus according to claim 1, wherein the light beam deflecting member is retractable with respect to an optical path of the exposure light.