JPH0358529B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an alignment device that aligns a mask and a wafer by photoelectrically detecting alignment marks.

[Conventional technology]

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 trying to align the mask 1 and the wafer 2, the laser beam L emitted from the laser light source 11 is directed through the scanning polygon mirror 10, the half mirror 9, the objective lens 8, and the mirror 5 to the mask. 1. This light passes through the projection lens 3 and is reflected on the wafer 2.
Again mirror 5, objective lens 8, half mirror 9,
The light enters the light source detector 16 via a stopper 17 (shown in FIG. 5). On the optical path of the laser beam on the wafer 2 and mask 1, there are alignment marks M and M' as shown in FIG. Signals from the marks M and M' are detected by a photoelectric detector 16, amplified by a preamplifier 15, and an arithmetic unit 14 determines the amount of deviation between the wafer 1 and the mask 2. Based on the amount of deviation, the moving stage 12 is moved via the driver 13 to align the mask 1 and the wafer 2. Once the wafer 1 and mask 2 are aligned in this manner, the shutter (not shown) of the exposure illumination device 4 is opened and exposure is performed.

At this time, if mirror 5 is at position a, mirror 5
A shadow is formed on the mask 1, and unprinted areas or uneven illuminance occur on the mask 1. For this reason,
Prior to exposure, it is necessary to move the mirror 5 to a position b 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. This position a
Reproducibility is important, and even a slight deviation in the tilt of the mirror 5 will change the incident path of the laser beam.
This gives an error in measuring the amount of deviation between the mask 1 and the wafer 2.

Conventionally, such optical elements such as the mirror 5 are driven by position detection using a photo switch (not shown),
Alternatively, open loop control using a pulse motor 7 or the like has been used.

[Problem to be solved by the invention]

However, this type of control lacks mechanical and economical stability against vibrations, play, etc., and it is difficult to obtain a highly accurate photo switch.
Furthermore, there were other problems such as the need for very precise adjustment when assembling the device.

An object of the present invention is to provide an alignment apparatus that can solve the above-mentioned problems and improve the alignment accuracy of a mask and a wafer.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an alignment apparatus that aligns a mask and a wafer by photoelectrically detecting alignment marks.
a light source (laser light source 11) that generates a light beam for certifying a mark portion on which the alignment mark is provided; A mirror 5 that deflects and reflects the light beam from the mark and the light reflected from the mark portion, a drive source (pulse motor 7) for moving the mirror, and a first and second light receiving section at different positions. , and a part of the reflected light from the mark portion taken out from the optical path is transmitted to the first light receiving section (light receiving surface 2
A first signal corresponding to the positional relationship between the mask and the wafer is generated by photoelectric detection in step 8), and a first signal is generated by another part of the reflected light from the mark portion taken out from within the optical path. a photoelectric detector 19 that generates a second signal according to the position of the light spot on the second light receiving section by photoelectrically detecting the light spot on the second light receiving section (light receiving surfaces 29, 30); a stage (movement stage 12) for adjusting the positional relationship between the mask and the wafer based on a first signal from the photoelectric detector; and a stage (moving stage 12) for adjusting the positional relationship between the mask and the wafer, and the light beam reflected by the mirror is set in a predetermined relationship with the mark portion. It has a control circuit (arithmetic circuit 14) that controls the adjustment of the mirror position by the drive source based on a second signal from the photoelectric detector so that the mirror is irradiated with light.

More preferably, a stopper 17 having a first aperture at the periphery and a second aperture at the center is disposed between the mirror and the photoelectric detector, and the first light receiving section is provided with the first aperture. A part of the reflected light that has passed through the aperture is incident on the second light receiving section, and another part of the reflected light that has passed through the second aperture is incident on the second light receiving section.

According to the present invention, it is possible to detect the positions of the alignment mark and the mirror with one photoelectric detector.

〔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 shown in FIG. That is, a photoelectric detector 19 is disposed in an optical path P for detecting reflected light from alignment marks on the mask 1 and the wafer 2.

As shown in FIG. 7, the photoelectric detector 19 has two light-receiving surfaces 29 and 30 at the center and a circular light-receiving surface 28 at the periphery thereof. light receiving surface 28,
29 and 30 each have an independent configuration. Furthermore, the photoelectric detector 19 includes electrodes 31, 32, 33 for independently extracting electrical signals corresponding to the amount of light received by each of the light receiving surfaces 28, 29, 30, and a bias electrode 34.
and has.

In addition, in FIG. 2, the stopper 1 shown in FIG.
7, a stopper 2 as shown in FIG.
0 is used. The stopper 20 has one opening 20a in the center and a plurality of openings 2 in the periphery.
It has 0b.

Each electrode 31, 32, 33 of the photoelectric detector 19
is connected to the preamplifier 18. Preamplifier 18
are the respective light receiving surfaces 28, 29, 30 of the photoelectric detector 19.
The photocurrents are each independently converted into current and voltage, and
Electrical signal 3 corresponding to the amount of received light of 8, 29, 30
6, 37, and 38 are transmitted to the arithmetic 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. As shown in FIG. Therefore, when the mirror 5 is in the normal position, the light h directly reflected by the wafer 2 passes through the aperture 20a, and as shown in FIG. 30 evenly. In this state, equal photocurrents are generated in the electrodes 32 and 33 of the photoelectric detector 19.
Therefore, the outputs 37 and 38 (corresponding to the light receiving surfaces 29 and 30 in FIG. 7) of the preamplifier 18 also have the same value.
In this case, the arithmetic circuit 39 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 is slightly shifted in the direction indicated by the arrow i from the normal position a in FIG. Then, the area h that hits the light receiving surfaces 29 and 30 of the photoelectric detector 19
is shifted as shown in FIG. At this time, the amount of light detected on the light receiving surfaces 29 and 30 of the photoelectric detector 19 becomes uneven, and the electrodes 32 and 3 of the photoelectric detector 19
The photocurrent appearing in 3 also becomes non-uniform in accordance with the amount of light. Therefore, the electric signals 37 and 38 output by the preamplifier 18 also become uneven. The arithmetic circuit 14 determines the direction in which the mirror 5 is displaced by comparing the magnitudes of the electric signals 37 and 38 from the preamplifier. Then, the position of the mirror 5 is corrected by rotating the pulse motor 7 via the driver 40 until the electric signals 37 and 38 become equal.

Next, a signal detection system for aligning the mask 1 and the wafer 2 after the mirror 5 has been positioned will be described. In the apparatus shown in FIG. 2, alignment marks M consisting of V-shaped patterns 21, 22, 23, and 24 as shown in FIG. 3 are formed on the wafer 2. As shown in FIG. Also, on the mask 2 there are V-shaped patterns 25, 2 as shown in FIG.
6 alignment marks M' are formed.
Scan L along the scan axis C over these marks (M, M') with a laser beam, move the moving stage 12 so that the marks M, M' are in the positional relationship as shown in FIG. The mask 1 and the wafer 2 are aligned. Here, mask 1
Alternatively, the laser beam hitting each mark M, M' on the wafer 2 is scattered as shown in FIG.
The scattered lights become scattered lights d to g. The scattered lights d to g pass through the opening 20b at the periphery of the stopper 20, and as shown in FIG.
Detected in dark field. (Regarding the dark field detection,
This is done in the same way in the conventional device shown in FIG.
The scattered lights d to g pass through a stopper 17 and are detected in a dark field on a light receiving surface 16a of a photoelectric detector 16, as shown in FIG. ) The detected scattered lights d to g are amplified by the preamplifier 18 and guided to the arithmetic circuit 39 as an electric signal 36. The encyclopedia circuit 39 determines the amount of deviation between the mask 1 and the wafer 2 from the electric circuit 36. The driver 13 moves the moving stage 12 based on the amount of deviation to align the mask 1 and the wafer 2.

After completing the positioning of the mirror 5 and the alignment between the mask 1 and the wafer 2 as described above, the mirror 5 is returned from position a to position b, and the shutter (not shown) of the exposure illumination device 4 is opened. ,
Exposure will begin.

In the above embodiment, the light receiving surfaces 29 and 30 at the center of the light exposure detector 19 are not limited to being divided into two.
FIG. 11 shows another embodiment. This means that the light receiving surface is further divided into two, resulting in four light receiving surfaces 50, 51, 52,
53 was formed. If you do this,
Furthermore, the amount of deviation of the mirror 5 can be measured in one more axial direction. Furthermore, the light receiving surfaces 29, 30, etc. are not only equipped with photoelectric detection elements such as photodiodes, but also at least one photoelectric detection element such as a photoelectric position sensor.
It may be an element that detects the incident position of light in the dimensional direction.

FIG. 12 shows still another embodiment. This does not include a light receiving section 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, and four light-receiving surfaces 60, 61,
62 and 63 are formed. Each light receiving surface 6
Electrodes (not shown) are provided so that signals corresponding to the light receiving surfaces of 0 and 63 can be taken out independently. Further, here, a stopper having an opening only at the periphery as shown in FIG. 5 is used. Therefore, in this embodiment, the position of the mirror 5 shown in FIG. 2 can be detected in the same manner as in the previous embodiment by determining the light quantity balance of each light receiving surface 60, 63. However, in this case, all the light that enters the light receiving surfaces 60 and 63 is scattered light from the alignment marks, so when trying to control the position of the mirror 5, this scattered light completely enters the light receiving surface. That is, it is necessary that the alignment mark be within the field of view of the objective lens 8 shown in FIG.

In this regard, the embodiments shown in FIGS. 9 to 11 above use a photoelectric detector 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, it is no longer necessary for the alignment mark to be within the field of view of the objective lens.
As long as the direct reflected light from the wafer or mask surface can be detected, precise position control of the mirror 5 can be performed at any time.

〔Effect of the invention〕

As explained above, according to the present invention, in an alignment apparatus that aligns a mask and a wafer by photoelectrically detecting alignment marks, light for illuminating a mark portion where the alignment mark is provided is provided. detecting the position of a mirror that is arranged in relation to the optical path between a light source that generates a beam and the mark portion and that reflects the light beam from the light source and the reflected light from the mark portion so as to deflect each of them; between the optical path for detecting the alignment mark and the optical path for actually detecting the alignment mark after positioning the mirror based on the position detection of the mirror.
No errors occur at all.

Therefore, it is possible to obtain very stable positional reproducibility of the mirror, and at the same time, it is possible to greatly improve the alignment accuracy between the mask and the wafer. Furthermore, in assembling or maintaining the alignment device, extremely precise adjustment, which was conventionally required, can be eliminated. Further, there is no need to provide a new optical element or the like for detecting the position of the mirror, and a very excellent effect is achieved in that a stable positioning device with a simple configuration can be realized.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a conventional alignment device for a mask and a wafer, FIG. 2 is a schematic configuration diagram showing an alignment device to which an embodiment of the present invention is applied, and FIGS. Fig. 4 is an explanatory diagram showing the scattering of laser light by the alignment mark, Fig. 5 is a plan view of a conventional stopper, and Fig. 6 is a diagram showing how scattered light hits a conventional photoelectric detector. FIG. 7 is a perspective view showing an embodiment of the photoelectric detector according to the present invention; FIG. 8 is a plan view showing an embodiment of the 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;
FIG. 0 is a schematic diagram in which the optical element is in a shifted position, and FIGS. 11 and 12 are schematic diagrams in which other embodiments of the photoelectric detector are irradiated with scattered light and directly reflected light. 1...Mask, 2...Wafer, 5...Mirror,
7... Pulse motor, 19... Photoelectric detector, 20
...Stopper, 20a, 20b...Opening, 2
8, 29, 30... Light receiving surface, 31, 32, 33,
34... Electrode, 50, 51, 52, 53... Light receiving surface, 60, 61, 62, 63... Light receiving surface, M,
M'...Matching mark.

Claims (1)

[Claims] 1. In an alignment device that aligns a mask and a wafer by photoelectrically detecting an alignment mark, a light beam is generated to illuminate a mark portion where the alignment mark is provided. a light source; a mirror disposed in relation to an optical path between the mark portion and the light source and reflecting the light beam from the light source and the reflected light from the mark portion so as to deflect each; A drive source for movement and first and second light receiving sections are provided at different positions, and a part of the reflected light from the mark portion taken out from within the optical path is photoelectrically detected by the first light receiving section. A first signal corresponding to the positional relationship between the mask and the wafer is generated, and a light spot formed by another part of the reflected light from the mark portion taken out from within the optical path is directed to the second light spot. a photoelectric detector that generates a second signal according to the position of the light spot on the second light receiving section by photoelectrically detecting the spot on the second light receiving section; a stage for adjusting the positional relationship of the wafer; and the driving based on a second signal from the photoelectric detector so that the light beam reflected by the mirror is irradiated onto the mark portion in a predetermined relationship. An alignment device comprising a control circuit for controlling position adjustment of the mirror by a source. 2 A stopper having a first aperture at the periphery and a second aperture at the center is disposed between the mirror and the photoelectric detector, and the first light receiving section receives the reflected light that has passed through the first aperture. The alignment device according to claim 1, wherein a part of the light is incident on the second light receiving section, and another part of the reflected light that has passed through the second aperture is incident on the second light receiving section. .