JPS60220348A - Position detector of optical element - Google Patents

Abstract

PURPOSE:To improve the positioning precision between a mask and a wafer by arranging a position detector on an optical path, where the optical signal from a matching mark is detected, to detect the extent of deviation of an optical element on the optical axis. CONSTITUTION:A photoelectric detector 19 has two light receiving faces 29 and 30 in the center part and has a circular light receiving face 28 in the peripheral part. If a mirror 5 is placed in a regular position, a light (h) reflected directly on a wafer 2 passes an aperture 20a and is made incident on two light receiving faces 29 and 30 equally. A mask 1 and the wafer 2 are positioned after positioning of the mirror 5 is terminated, and a matching mark M consisting of downward opening bar-shaped patterns 21-24 is formed on the wafer 2, and a matching mark M' consisting of similar patterns 25 and 26 is formed on the mask 2. Marks M and M' are scanned along a scan axis C by a laser beam to move a moving stage 12, thus matching the mask 1 and the wafer 2.

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a device for detecting the position of an optical element for detecting or observing alignment marks used in a device for relative alignment of a mask and a wafer. .

[Prior art]

FIG. 1 is an example of an optical system for observing masks and wafers used in a conventional mask and wafer alignment apparatus. In the same figure, when attempting to align the mask l and the wafer 12, the laser beam L emitted from the laser light source 11 is directed to the scanning polygon mirror 10. half mirror
9, enters the mask l via the objective lens 8 and mirror 5. This light passes through the projection lens 3, is reflected on the sea urchin/% j2, and is again reflected on the mirror 5. Objective lens8. The light enters a photodetector 16 via a nozzle mirror 9° stopper 17 (shown in FIG. 5). On the optical path of the laser beam on the wafer 2 and the mask l, there are alignment marks M as shown in FIG.
There is a forward. Signals from the marks M and M' are detected by a photoelectric detector 16, amplified by a preamplifier 15, and the amount of deviation between the mask 2 and the mask 2 is calculated by an arithmetic unit 14. Based on the amount of deviation, the moving stage 2 is moved via the dry rack 18 to align the mask 1 and the wafer 2. Once the wafer 1 and the mask 2 are aligned in this manner, the shutter (not shown) of the exposure illumination device 4 is opened to perform exposure.

At this time, if the mirror 5 is at position a, a shadow of the mirror 5 will be formed on the mask 1, causing unprinted areas or uneven illuminance on the mask 1. Therefore, prior to exposure, it is necessary to move the mirror 5 to a position where it is not exposed to the printing light. When the printing is completed, the mirror 5 is returned to position a for alignment for the next printing. The reproducibility of this position a is important; even a slight deviation in the tilt of the mirror 5 will change the incident path of the laser beam, causing the mask l
This gives an error to the measurement of the amount of deviation of the wafer 2.

Conventionally, such optical elements such as the mirror 5 have been driven by position detection using a photoswitch (not shown) or open loop control using a pulse motor 7 or the like.

However, this type of control suffers from poor mechanical and temporal stability against vibrations, backlash, etc., difficulty in obtaining highly accurate photoswitches, and the need for extremely precise adjustments when assembling the device. There were problems such as:

[Purpose of the invention]

An object of the present invention is to solve the above-mentioned problems, to obtain stable position reproducibility of the optical element, and to improve the accuracy of alignment between the mask and the sea urchin. An object of the present invention is to provide a position detection device.

In order to achieve the above object, a position detection device according to the present invention is used in an optical system for detecting or observing alignment marks used for relative alignment of a mask and a wafer. A detection device for detecting the position of an optical element such as a mirror, characterized in that it is disposed in an optical path for detecting an optical signal from the alignment mark, and is a single detection device. The position of both the alignment mark and the optical element can be detected.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic diagram of a mask and wafer alignment apparatus to which an embodiment of the present invention is applied.

Here, a photoelectric detector 19 according to this embodiment is installed in place of the photoelectric detector 16 in FIG.

That is, in the optical path P for detecting the reflected light from the alignment marks on the mask l and the wafer 2, the photoelectric detector 19
is arranged.

As shown in FIG. 7, the photoelectric detector 19 has two light-receiving surfaces 29 and 80 at the center and a circular light-receiving surface 28 at the periphery thereof. The light receiving surfaces 28°29.80 are each constructed independently. Furthermore, the photoelectric detector 19 has a light receiving surface 28 .
It has electrodes 81, 32, 33 for independently extracting electric signals corresponding to the amount of received light of each of 29, 30, and a bias electrode 34.

Further, in FIG. 2, a stopper 20 as shown in FIG. 8 is used instead of the stopper 17 shown in FIG. 5. The stopper 20 has one opening 20a in the center and a plurality of openings 20b in the periphery.

Each electrode 31 , 32 , 33 of the photoelectric detector 19 is connected to a preamplifier 18 . The preamplifier 18 independently converts the photocurrents of the light receiving surfaces 28, 29, and 30 of the photoelectric detector 19 into currents and voltages, and calculates an electric signal 8617° 38 corresponding to the amount of light received by the light receiving surfaces 28° 29, 30. It is transmitted to circuit 39.

Here, a signal detection system for positioning the mirror 5 will be explained. As shown in FIG. 8, an opening 20a is formed in the center of the stopper 20. Therefore, when the mirror 5 is in the correct position, the light directly reflected by the wafer 2 passes through the aperture 20a and hits the two central light receiving surfaces 29 and 30 of the photoelectric detector 19 as shown in FIG. incident evenly. In this state, equal photocurrents are generated in the electrodes 32, 33 of the photodetector 19.

Therefore, the output 37.88 of the preamplifier 18 (corresponding to the light receiving surface 29.80 in FIG. 7) also has the same value.

In this case, the arithmetic circuit 89 does not give any instructions to the driver 40, so the mirror 5 maintains its proper position.

On the other hand, suppose that the mirror 5 slightly deviates from the normal position a in FIG. 2 in the direction indicated by the arrow i. Then the photoelectric detector 19
The tip of the light-receiving surface 29.80 is shifted as shown in FIG. At this time, the light receiving surfaces 29 and 80 of the photoelectric detector 19
The amount of light detected by the photodetector 19 becomes uneven, and the photocurrent appearing at the electrodes 32, 38 of the photoelectric detector 19 also becomes uneven corresponding to the amount of light.

Therefore, the electrical signal output from the preamplifier 18 is 37°.
38 is also unequal. The arithmetic circuit 14 determines the direction in which the mirror 5 is displaced by comparing the magnitudes of the electric signals 3', 7, and 38 of the preamplifier. and electrical signal 37.38
The position of the mirror 5 is corrected by rotating the pulse motor 7 via the driver 40 until the values become equal.

Next, a signal detection system for aligning the mask l and the wafer 2 after the mirror 5 has been positioned will be described. In the apparatus shown in FIG. 2, V-shaped patterns 21, 22, . . . are formed on the wafer 2 as shown in FIG.
An alignment mark M consisting of 28.24 is formed.

Also, on the mask 2, alignment marks M' consisting of V-shaped patterns 25 and 26 as shown in FIG. 8 (11) are formed. These marks (M, M') with laser beam
2 along the scan axis C and 1 the above-mentioned mark M.

The movable stage 12 is moved so that M' is in the positional relationship as shown in Figure 8), thereby aligning the mask l and the wafer h2. Here, the laser beam hitting each mark M, M' on the mask l or the wafer 2 is scattered as shown in FIG. 4, and becomes scattered lights d to g. This scattered light dg passes through the opening 20b at the periphery of the stopper 20 and is detected in a dark field by the light receiving surface 28 of the photoelectric detector 16, as shown in FIG. (Regarding the dark field detection,
The conventional apparatus shown in FIG. 1 performs the same process, and the scattered lights d to g are detected in a dark field by the light receiving surface 16a of the photoelectric detector 16 via the stopper 17, as shown in FIG. )
The detected scattered light dg is amplified by a preamplifier 18,
The signal is guided to an arithmetic circuit 89 as an electrical signal 36. The arithmetic circuit 89 calculates the amount of deviation between the mask l and the wet cloth X2 from the electric signal 86. The driver 13 moves the moving stage 12 based on the amount of deviation to align the mask l and the wafer 12.

After the positioning of the mirror 5 and the alignment between the mask l and the wafer 2 are completed as described above, the mirror 5 is
is returned from position a to position bK, the shutter (not shown) of the exposure illumination device 4 is opened, and exposure is started.

In the above embodiment, the central light receiving surface 29 of the photoelectric detector 19
．． 30 is not limited to dividing into two.

FIG. 11 shows another embodiment. This further increases the light receiving surface by 2
It is divided into four light-receiving surfaces 50, 51, 52, and 53. In this way, it is possible to measure the amount of deviation of the mirror 5 in the 5-axis direction. Further, the light receiving surfaces 29, 80, etc. may be not only photoelectric detection elements such as photodiodes, but also elements that detect the incident position of light in at least one dimension, such as a photoelectric position sensor.

FIG. 12 shows still another embodiment. This does not have a light-receiving surface in the center for directly detecting reflected light.

Instead, the light-receiving surface for dark-field detection of the scattered light from the alignment mark as described above is divided into four to form four light-receiving surfaces 60.61° and 62.63°.

Electrodes (not shown) are provided so that signals corresponding to the amount of light received by each of the light receiving surfaces 60 to 63 can be independently extracted. Further, here, a stopper having an opening only at the periphery as shown in FIG. 5 is used. Therefore, in this embodiment, each light receiving surface 6
By adjusting the light quantity balance between 0 and 63, the position of the mirror 5 shown in FIG. 2 can be detected in the same manner as in the previous embodiment. However, in this case, all the light incident on the light receiving surfaces 60 to 68 is scattered light from the alignment marks, so
When trying to control the position of the mirror 5, this scattered light must be completely within the light-receiving surface, that is, the alignment mark must be within the field of view of the objective lens 8 in FIG. is necessary.

In this regard, in the embodiments shown in FIGS. 9 to 11 above, a photoelectric detector is used that can detect the scattered light from the alignment mark and the directly reflected light from the wafer or mask on the same optical axis. Therefore, when detecting the position of the mirror 5, there is no need for the alignment mark to be within the field of view of the objective lens, and as long as the direct reflected light from the wafer or mask surface can be detected, the mirror 5 can be detected at any time. 5 precision position control is possible.

In each of the above-described embodiments, a mirror is particularly used as an optical element whose position should be detected, but the present invention is not limited to this, and the present invention can also be applied to detecting the position of a lens or the like.

〔Effect of the invention〕

As explained above, the position detection device according to the present invention detects the amount of deviation of an optical element on the optical axis by being disposed on the optical path for detecting the optical signal from the alignment mark. This made it possible. Therefore, no error occurs between the optical path for detecting the position of the optical element and the optical path for actually detecting the alignment mark after positioning the optical element based on the position detection. Therefore, it is possible to obtain extremely stable positional reproducibility of the optical element, and at the same time, it is possible to greatly improve the alignment accuracy between the mask and the wafer. Furthermore, when assembling and adjusting or maintaining the positioning device, extremely precise adjustments that were conventionally required are no longer necessary, and it is also necessary to specifically provide a new optical path and optical element for detecting the position of the optical element. This has the very excellent effect of realizing a stable positioning device with a simple structure and without any problems.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a conventional alignment device for masks and wafers, FIG. 2 is a schematic configuration diagram showing an alignment device to which an embodiment of the present invention is applied, and FIGS. is a schematic diagram of the alignment marks on the wafer and mask, Figure 4 is an explanatory diagram showing the scattering of laser light by the alignment marks, Figure 5 is a plan view of a conventional stopper, and Figure 6 is a conventional photodetector. FIG. 7 is a perspective view showing an embodiment of a photoelectric detector according to the present invention, and FIG. 8 is a plan view showing an embodiment of a stopper according to the present invention. Figures 9 and 10 show the photoelectric detector in Figure 7 being hit by scattered light and directly reflected light, Figure 9 is a schematic diagram when the optical element is in the proper position, and Figure 10 is a schematic diagram of the photoelectric detector in Figure 7. A schematic diagram when the optical element is in a shifted position. Figures 11 and 12 are schematic diagrams showing states in which scattered light and directly reflected light are applied to other embodiments of the photoelectric detector. '・・・・・・・・・・・・Conformity mark. Patent applicant: Canon Co., Ltd.

Claims (1)

[Claims] ill A detection device for detecting the position of an optical element used in an optical system for detecting or observing alignment marks used to perform relative alignment between a mask and a wafer. A position detection device, characterized in that it is disposed on an optical path for detecting an optical signal from the alignment mark. (2) The position detecting device according to claim 1, wherein the position detecting device can read the incident position of light in at least one dimension. (3) The position detection device has at least two independent light-receiving surfaces in the center and at least one in the periphery, and is configured to be able to independently extract photocurrent from each of the light-receiving surfaces. The light-receiving surface at the periphery is used for dark-field detection of scattered light from the alignment mark, and the light-receiving surface at the center is used for detecting light directly reflected from the wafer or mask. A position detection device according to claim 1 or 2. (4) The position detection device includes a stopper having a peripheral opening for passing the scattered light from the alignment mark and a central opening for passing the direct reflected light from the wafer or mask. The position detection device according to claim 3, characterized in that it has: (5) The position detection device according to any one of claims 1 to 4, wherein the optical element is a mirror.