JPH03241817A - Method and apparatus for detecting alignment mark - Google Patents

Abstract

PURPOSE:To obtain a small-sized alignment mark detecting device, having high degree of stability, with which an alignment mark can be detected accurately even when there are recesses and protrusions on a resist, at low cost by a method wherein the illumination light having different wavelengths are separated into the first and the second lights, the incidence angles to the alignment mark of those lights are differentiated, and a diffracted light is detected from the alignment mark. CONSTITUTION:In the device, with which the alignment mark 25 on a wafer 5 will be detected, of a projecting and exposing device with which an original pattern is exposed on the wafer 5, a means 15 with which at least two illumination lights having different wavelength are separated into the distinguishable first light 23 and the second light 24 for the light of each wavelength, a means 16 with which the incidence angle against the alignment mark 24 is differentiated for the above-mentioned first light 23 and the second light 24, and a means 201, with which the diffracted lights 26 and 27 coming from the alignment mark 25 are detected, are provided in the above-mentioned alignment mark detecting device. Consequently, four distinguishable lights can be obtained using two laser beams having two different wavelengths respectively, and as a result, the position of alignment mark can be detected in a highly precise manner similar to the case where the laser beams of four different wavelengths having four light sources are used.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an alignment mark detection method and detection device for determining the position of a layered pattern on a semiconductor wafer, etc. When the alignment mark detection waveform becomes asymmetric due to uneven layer thickness, asymmetry of the alignment mark step, etc., this method improves the symmetry and aligns the mask pattern and wafer pattern with high precision. Alignment mark detection method, and.

This is related to the device.

[Prior Art] A projection exposure apparatus that exposes an original pattern onto a wafer uses single-wavelength light to improve the resolution of exposure.

A projection lens dedicated to single wavelength light is used for this purpose.

Therefore, even when detecting alignment marks, the detection is performed by illuminating with single wavelength light.

Furthermore, since the reduction projection lens dedicated to a single wavelength used in this projection exposure apparatus is precisely manufactured, it is difficult to correct chromatic aberration.

In the conventional technology, the state of illumination and detection of alignment marks using single wavelength light will be explained with reference to FIG.

As shown in FIG. 8(A), single wavelength illumination light 102 is irradiated from above the reticle 1 and illuminates the alignment mark 25 on the wafer 5 through the reduction projection lens 4. As shown in FIG. The reflected light from here is reflected by a half mirror 106 and detected by a detector 107.

FIG. 8(B) is an enlarged view of the image detected by the detector 107, and the alignment mark 25 is visible in the window 108 on the mask.

This alignment mark 25 is matched with a mark drawn on the reticle 1, and the mask pattern and wafer pattern are matched.

On the other hand, a resist 109 is usually applied on the alignment mark because it is necessary for pattern formation.

Therefore, the cross-sectional view near the alignment mark is as follows.

As shown in FIG. 9, it can be considered separately into a mark portion 110 and a resist portion 111.

Therefore, in this case, the single wavelength light illuminated from above the reticle 1 causes interference in the resist portion, but if the resist thickness is uniform, the intensity of the interference light is constant.

However, in reality, the resist also has unevenness due to unevenness of the alignment mark and unevenness of the resist thickness. Therefore, the intensity of the interference light is not constant, resulting in a problem that the accuracy of detecting the alignment mark is reduced.

In order to solve this problem, the technique described in Japanese Unexamined Patent Publication No. 60-80223 uses illumination light.

Bright lines (particularly bright light) contained in mercury lamps, such as H-line (wavelength 405 nm) and 1G-line (wavelength 436 nm)
, e-line (wavelength 546nm), d-line (wavelength 577nm)
The influence of resist unevenness is reduced by selecting light of two or more wavelengths from m) for illumination and synthesizing the intensity signals of the detected light.

As an example, FIG. 10 shows a detection signal obtained when illuminating with e-line and d-line, and a signal obtained by combining these signals.

In the figure, the target low intensity portions indicate both ends 112 of the alignment mark 25 with respect to the center line of the diagram showing one combined signal. The intensity is low when the light enters from above.

This is because less light is scattered at the edges and returns upwards.

That is, it can be seen that by combining the two signals, both ends 112 of the alignment mark 25 are detected symmetrically, and the influence of the unevenness of the resist is reduced.

Next, JP-A-60-136312 describes a method of illuminating and synthesizing detection signals by changing the apparent wavelength.

As shown in FIG. 11, this technique uses a laser 113 with high straightness as illumination light, and swings a reflection [114] in the middle of the optical path.

This is a technique in which illumination light is oscillated around the alignment mark 25. That is, as shown in FIG.
This takes advantage of the fact that the optical path length changes within 0.09.

As a result, the influence of unevenness of the resist is reduced, and the accuracy is improved.
Alignment marks can be detected.

In addition, the technology described in Japanese Patent Application Laid-open No. 01-8651111 uses four laser beams with wavelengths different by 27n+m as illumination light, thereby reducing interference within the resist and marking alignment marks with high precision. This shows that it is possible to detect In particular, wavelength 458.488,
It recommends 515,543 nm lasers.

[Problems to be Solved by the Invention] Among the above-mentioned conventional techniques, the one that has the best alignment mark detection accuracy is the so-called four-wavelength laser illumination method described in Japanese Patent Application Laid-Open No. 0F-86518, or , the so-called, described in Jikai F@60-136312 publication.
It is considered to be a laser oscillating illumination method.

However, since the four-wavelength laser illumination method requires four types of laser oscillators, there is a problem that the projection exposure apparatus becomes expensive.

In addition, the laser swing illumination method has a problem in that since there is a movable part for swinging the laser, the optical axis is likely to change, resulting in a decrease in alignment mark detection accuracy.

The purpose of the present invention is to solve the above-mentioned problems of the prior art,
It is an object of the present invention to provide a small, inexpensive, and highly stable alignment mark detection device, and to provide a method for correctly detecting one alignment mark even if unevenness occurs in the resist.

[Means for Solving the Problems] The above object is a means for separating at least two illumination lights having different wavelengths into distinguishable first light and second light for each wavelength.

This can be achieved by means of differentiating the incident angles of the first light and the second light onto one alignment mark, and by means of detecting diffracted light from the alignment mark.

Furthermore, two laser beams with different wavelengths may be used as the illumination light.

Further, the above object is to separate at least two emitted lights of different wavelengths into a first light and a second light that can be identified for each light of each wavelength, and to The angles of incidence of the first light and the second light on the alignment mark are made different.

This can be achieved by detecting the alignment mark by detecting the diffracted light from the alignment mark.

[Function] With the alignment mark detection device configured as described above, two or more illumination lights with different wavelengths can be distinguished into first light and second light for each wavelength. The first light and the second light are incident on the alignment mark at different angles of incidence.

Then, on the surface and bottom of the alignment mark,
These incident lights are diffracted.

By detecting the plurality of diffracted lights, the influence of interference can be reduced and the position of the alignment mark can be detected with high accuracy.

If two laser beams with different wavelengths are used as illumination light, it is possible to obtain four distinguishable lights with the two laser beams. As with using light, the position of one alignment mark can be detected with high accuracy.

Further, as in the laser swing illumination method, since there is no movable part for swinging the laser, the accuracy of detecting one alignment mark does not deteriorate.

Furthermore, compared to the case where light of two wavelengths is incident perpendicularly, fluctuations in detection accuracy due to interference due to unevenness of the resist caused by non-uniform resist film thickness and pattern step differences can be significantly reduced. As a result, the asymmetry of the detected waveform due to resist coating unevenness and pattern step unevenness of alignment marks is significantly reduced, alignment mark detection accuracy is significantly improved, and a desired pattern can be obtained.

In addition, in pattern detection systems in which it is difficult to construct a detection system using continuous spectral components or light having multiple spectra, the influence of the transparent film of the test object covering the pattern and the pattern step difference. This is effective in accurately detecting the position and two-dimensional (plane) shape of a pattern.

[Example] The first example of the present invention will be described below with reference to FIGS. 1 to 7 and 1.
This will be explained with reference to FIGS. 3 and 14.

FIG. 1(A) is an exploded view of the alignment mark detection device according to the present embodiment, FIG. The figure is an explanatory diagram for explaining the optical path in this example,
Fig. 3 is an explanatory diagram showing the detected image, Figs. 4 and 5 are explanatory diagrams showing the principle of this embodiment, Figs. 6 and 7 are explanatory diagrams showing the effects of the embodiment, and Figs. It is a table showing results obtained by substituting numerical values into the analytical formula of the first example.

As shown in FIG. 1, the configuration of this embodiment is roughly divided into a laser emission bag M2O0 that emits a laser beam that irradiates the alignment mark, and a laser emission bag M2O0 that emits a laser beam that irradiates the alignment mark, and an alignment detection signal that forms an image of the diffracted light from the alignment mark. Positioning optical device 12 that outputs
01, reticle 1, reduction projection lens 4, and wafer 5
It consists of

Configure each device according to the direction in which the laser beam travels.

explain.

First, the configuration of the laser emitting device 200 will be explained 6. The laser emitting device W2O0 has a laser light source 11 that emits a laser beam with a wavelength λ1, a laser light source 12 that emits a laser beam with a wavelength λ2, In front of the optical path of 11, there is a dichroic mirror 1 that combines two laser beams emitted from two laser light sources 11 and 12 onto one optical path.
Place 3. A reflecting mirror 39 is disposed in front of the laser light source 12 on the optical path to make the laser light of wavelength λ2 enter the dichroic mirror 13 .

A quarter wavelength plate 14 is arranged in front of the dichroic mirror 13, and a birefringent prism 15 is further arranged in front of it. In front of the birefringent prism 15, an S-polarized laser beam, which is the laser beam polarized by the birefringent prism 15, is refracted by a small angle θ.
A resist 6 is arranged for moving straight away from the optical axis,
A reflecting mirror 19 for guiding the laser beam to the alignment optical device is arranged behind it.

Next, the configuration of the 1-alignment optical device 201 will be described in accordance with the direction in which the laser beam travels, similarly to the above.

A half prism 21 for refracting the laser beam from the laser emitting device 200 is arranged in front of the reflecting mirror 19. In front of this half prism 21, a lens 2
Place 1. moreover.

In front of this lens 21, a reflecting mirror 22 is arranged to make the laser beam enter the reduction projection lens 4.

Next, since the laser light incident on the alignment mark on the wafer 5 is diffracted at the alignment mark on the wafer 5, the configuration of the alignment optical bag j[201 is determined according to the direction in which this diffracted light travels.

explain.

In front of the half prism 20, a dichroic mirror 30 is arranged to reflect a laser beam of wavelength λ□. A reflection lR41 is arranged above this dichroic mirror 30, and a photoelectric element 33 for detecting a real image 31 of the alignment mark by a laser beam of wavelength λ8 is arranged in front of it.

In front of the dichroic mirror 30, a photoelectric element 32 is arranged to detect a real image 29 of the alignment mark using a laser beam of wavelength λ.

Furthermore, it has a signal adder 34 for adding the electrical signals from the two photoelectric elements 32 and 33 to obtain one detection signal 35.

Note that the three elements, the half prism 20, the lens 21, and the reflecting mirror 22, are common elements to the laser emitting device 200 and the alignment optical device 201.

A circuit pattern is drawn on the lower surface of the reticle 1 in a portion surrounded by a broken line 2, and reticle position detection devices 7a and 7b are provided above the reticle alignment marks 3a and 3b, respectively. .

Below reticle 1, the reticle pattern is reduced,
A reduction projection lens 4 for forming an image on the wafer 5 is arranged.

Further, below the reduction projection lens 4, a wafer 5 is placed on a stage (not shown).

Next, the operation of this embodiment will be briefly explained using FIG. 1.

First, it will be described later. Wafer alignment mark detection is performed to detect the position of the wafer 5. Next, the reticle alignment marks 3a, 3b drawn on the reticle 1 and the reticle position detection systems 7a, 7b are moved slightly on the reticle.
By controlling the reticle position, the reticle 1 is aligned with the target position. As a result, the pattern drawn on the reticle 1 overlaps on the wafer 5 with the desired positional accuracy. Next, the exposure illumination system (
(not shown), the reticle 1 is irradiated with exposure illumination light. As a result, the circuit pattern drawn on the lower surface of the reticle 1 is reduced by the reduction projection lens 4 and printed onto the chip 6 on the wafer 5, completing the overlapping exposure.

Next, the operation of the wafer alignment mark detection device of this embodiment will be explained with reference to FIG. 1 according to the direction in which the laser beam travels.

Laser beams with wavelengths λ and λ2 are emitted from the light sources 11 and 12, respectively, and both are combined onto one optical path by a dichroic mirror 13. Since the laser beam is linearly polarized, it passes through the quarter-wave plate 14, becomes circularly polarized, and reaches the birefringent prism 15.

Therefore, the wavelength λ1. By passing through the birefringent prism 15, both of the laser beams of λ2 are branched into a P-polarized laser 17 and an S-polarized laser 18, respectively.

After that, the P-polarized laser 17 travels straight on the optical axis, but the S
By passing through the lens 16, the polarized laser 18
It is refracted by a small angle θ and moves straight away from the optical axis.

Next, focusing on the P-polarized laser 17 with wavelength λ1, further,
Continue explaining.

The P-polarized laser beam is reflected by a reflecting mirror 19 and formed into a half prism 20 (a semi-transparent prism is called a half prism).
, passes through the lens 21 and the reflecting mirror 22, and becomes light 1s23,
It reaches the reduction lens 4.

On the other hand, the S-polarized laser beam 8 does not pass along the optical axis, but follows roughly the same path as above to become light I/1It24 and reach the reduction lens 4.

The light rays 23 and 24 are, as shown in FIG. 1(B),
The alignment mark 25 on the wafer is illuminated.

The alignment mark is formed in a concave or convex pattern of 2 to 3 μm square, and when it is irradiated with a laser beam, diffracted lights like 26 and 27 shown by broken lines in the figure are generated.

This diffracted light passes through a reducing lens 4 and a reflecting mirror 2 in the opposite direction to the outward path.
2, the image is formed as an image 28 by − degrees. This statue 28
is further magnified by a lens 21, and a half prism 20
．． After the reflection fi41, the real image 29 becomes the real image 29. In other words, the position of the alignment mark 25 and the position of the real image 29 are in a conjugate relationship, and the real image 29 illuminated by the light beams 23 and 24 is at the same position. image is formed.

However, since the reduction lens 4 has chromatic aberration, the laser beams of wavelengths λ1 and λ2 form images at different positions.

Therefore, a dichroic mirror 30 is provided in the middle to reflect the light of wavelength λ2 and form a real image 31.

The two real images 29 and 31 are detected by separate photoelectric elements 32 and 33, converted into electrical signals, and then added together by a signal adder 34 to remove the influence of interference within the resist. Two detection signals 35 can be obtained.

This detection signal 35 is compared with a signal from a pre-stored reference mark (not shown) on the stage, and the position of the alignment mark 25 on the wafer is determined.

Wafer alignment is completed by matching the position of the reference mark on the stage.

Next, the optical path of the laser beam of wavelength λ or λ2 will be explained using FIG. 2.

FIG. 2(A) shows the optical path of the P-polarized laser beam 17, and FIG. 2(B) shows the optical path of the S-polarized laser beam 8.

As shown in FIG. 2(A), the parallel laser beam incident on the quarter wave plate 14 is split into a P-polarized laser beam 17 and an S-polarized laser beam 18 by passing through a birefringent prism 15. Ru.

The P-polarized laser beam 17 travels straight through the lens 16 and the lens 21.
The light is then focused on the entrance pupil 40 of the reduction lens 4.

Thereafter, the wafer 5 is irradiated with an incident angle of zero degrees.

On the other hand, the S-polarized laser 18 passes through the lens 16, is refracted by a small angle θ, and then travels, is further refracted by the lens 21, passes through the position of the copy 28, and is focused on the entrance pupil 4, and then It becomes parallel light, and at a predetermined angle of incidence on Ueno) 5,
Irradiate diagonally.

The positions of the alignment mark 25 and the image 28 are in a conjugate relationship, and since the laser beam passes the position of the copy 28, the alignment mark 25 on the wafer 5 can be illuminated.

In this case, the two laser beams illuminating the wafer 5 are 1
Since the two laser beams are branched, interference generally occurs on the wafer 5, resulting in severe illumination unevenness.

In order to avoid this phenomenon, this embodiment utilizes the property of the birefringent prism 15 to split circularly polarized light into S-polarized light and P-polarized light.

That is, in FIG. 2(A), the P-polarized laser is applied to the wafer 5.
Above, in FIG. 2(B), the wafer 5 is irradiated with an S-polarized laser. This is because the P-polarized laser and the S-polarized laser have different vibration planes, so even if they are illuminated at the same time, they do not interfere with each other.

Therefore, one laser beam can be split and used as two apparently laser beams.

(Hereinafter referred to as margin) Next, the principle of the alignment mark detection method of this embodiment,
The theoretical background will be explained using FIG.

According to the description in Japanese Unexamined Patent Application Publication No. 01-86518, it is shown that it is desirable to use four laser beams having different wavelengths of about 27 nm as the illumination light.

According to this prior art, the incident light in FIG. 1(B) has a wavelength λ0. λ1'
λ2. It would be possible to combine and detect the diffracted light of each wavelength using a λ2' laser, but since four laser light sources are required, the apparatus becomes expensive.

Therefore, as the vertically incident light 23 to the alignment mark, λ1. Using a laser with a wavelength of λ2, the diffracted light 26 is detected, and the incident light 24 which is inclined is also detected with a wavelength of λ1. λ
The diffracted light 27 is detected using a laser having a wavelength of 2.

Due to this inclined incident light 24, the apparent λ1 λ
The same effect as that obtained by irradiating light with a wavelength of 2' as vertically incident light 23 and detecting diffracted light 26 can be obtained.

The above is the principle of the alignment mark detection method of this embodiment.

The above principle will be explained by focusing on the influence of the step of the alignment mark and the resist thickness.

First, the above principle will be explained, focusing on the influence of pattern steps.

FIG. 4 shows a cross section of a resist 52 coated on the alignment mark 25 of FIG. 1(A).

Ray 53 is diffracted on the top surface of the alignment mark, and ray 54 is diffracted on the bottom surface of one alignment mark. The phase difference δ1 between the two light beams is expressed by the following equation.

However, sin θ,' = sin θ2 + □zP where h is the pattern step, p is the pattern pitch, n
2 is the refractive index of the resist.

When θ=O, the phase difference when illuminating with wavelengths λ1 and λ1' is δ1° and δ□. Then, the following equation is obtained.

zP zP On the other hand, when the wavelength λ1, the incident angle θ21, and the phase difference when illuminated are 61□, the following equation is obtained.

However, sinθ2□' = sinθ2□+-～-・・
・(5)zP Here, if δ11=δ1゜', then 1 2 sinθ□□' =-sinθ21
...(8) L Using equations (5) to (8), θ when illuminated with wavelength λ
, 1. θ2□, θ21. θ1□ can be found.

In other words, at an incident angle of θ, □ from the top of the resist, the wavelength λ
1 and detecting the diffracted light with a diffraction angle of θ1□', it can be seen that the same effect as that of vertically irradiating light with wavelength λ1 and detecting the diffracted light at that time can be obtained.

Similarly, the value when illuminated with wavelength λ2 can also be determined.

λ1 = 0.488μ, λ, = 0.543μ,
FIG. 13 shows the results obtained from the above equation when P,=5 μLn1=1, and n,=1.64.

Note that an Ar laser was used as the laser with a wavelength of 0.488 μm, and a He laser was used as the laser with a wavelength of 0.543 μm.
-Ne laser is used.

As shown in Fig. 3, the above two laser beams of wavelengths λ1 and λ2 are tilted vertically and 27.51 degrees to irradiate the alignment mark, and the diffracted light 26.27 shown in Fig. 1(B) is
By detecting the wavelength 0.4B8.

It can be seen that the same effect as illuminating with four laser beams of 0.515, 0.543, and 0.570μ can be obtained.

Next, focusing on the influence of resist thickness, explanation will be given using FIG. 5.

FIG. 5 shows a resist 52 on top of the first alignment mark 25.
This figure shows the state in which it has been applied.

When light ray 55 is incident at angle θ, it reaches point A and produces diffracted light 56. On the other hand, the 0th order diffracted light (regularly reflected light) at one point A passes from A to B and irradiates C, producing diffracted light 57,
As a result, beams 56 and 57 interfere.

The phase difference E1 between the two is expressed by a linear equation.

2π t□=n2d(AB+BC-AH)λ However, sin θ2'=sin θ2+nsp Here, d is the resist thickness, and n2 is the refractive index of the resist.

When θ,=O, the phase difference when illuminated with wavelengths λ and λ1' is ε1° and E□. ′, these are expressed by the following equation.

On the other hand, if the phase difference when illuminated with a wavelength λ8 and an incident angle θ21 is ε, 1, the following equation is obtained.

...(12) λma However, sinθ2□’ = sinθ2□+□zP ...(13) Here, ε□,=ε,. ′ λ.

1 z sinθz1'= sinθ21 ・
...(16)1 Using equations (13) to (16), θ when illuminated with wavelength λ1, 1. θ21. θ21 θ□, can be obtained.

Similarly, the value when illuminated with wavelength λ2 can also be determined.

λ, = 0.488 μL λ,, = 0.543μ
m, p = 5 μya, n engineering = 1. n,=1.6
FIG. 14 shows the results obtained from the above equation when the value is set to 4.

As shown in FIG. 14, by irradiating the registered alignment mark vertically and at an angle of 24.81 degrees with a laser of the above wavelength, and detecting the diffracted light 26°27 in FIG. 1(B), Wavelength 0.48g, 0.515°0.543
．． It can be seen that the same effect as illumination with a 0.570 μm laser beam can be obtained.

Putting all the above together, the wavelength is 0.488μ and 0.54μ
It can be seen that if the structure is such that the alignment mark is irradiated with a 3 μm laser beam vertically and at an angle of about 26 degrees, it is not necessary to use four laser light sources.

A laser with a wavelength of 0.488 .mu.m can be easily obtained by an Ar laser, and a laser with a wavelength of 0.543 .mu.m can be easily obtained by a He-Ne laser, so that they are easy to realize.

Next, FIG. 3 shows a display state of a detection signal when an alignment mark is detected using the detection device of this embodiment.

FIG. 3(A) shows the detection signal 35 in FIG. 1(A) at T
It is displayed on the V monitor 50, as shown in Figure 1 (
The alignment mark 25 in B) appears as a bright signal 51.

FIG. 3(B) shows the signal of the scanning line, where the horizontal axis is the X coordinate and the vertical axis is the voltage ■. The median value of this signal is determined and taken as the position 1fXO of the alignment mark on the wafer.

The position x0 of the alignment mark on this wafer.

The wafer alignment is completed by comparing the positions of the reference marks (not shown) on the stage stored in advance and matching the positions of the two marks.

Next, using FIG. 6, we will show the relationship between the pattern step of the alignment mark on the wafer and the interference intensity of the diffracted light 53 and 54 shown in FIG. 4 when the above laser beam is irradiated. .

Figure 6 (A) is different from the wavelength 0.48 in Figure 1 (B).
A laser beam of 8μ is incident as incident light 23, and diffracted light 2
The case where only 6 is detected is shown.

The horizontal axis 60 is the value of the pattern step of the alignment mark on the wafer, and the vertical axis 61 is the detected value of the diffracted light.

As shown in the figure, the first diffracted light detection value 61 is greatly influenced by the pattern step value 60 and fluctuates between 0.0 and 1.0. The fact that the diffracted light detection value 61 is 0.0 means that
Since this means that the pattern diffraction light signal becomes O, it becomes impossible to detect the alignment mark on the wafer.

On the other hand, in FIG. 6(B), irradiating with a two-wavelength laser,
The case where two diffracted lights 26 and 27 are detected is shown.

From the figure, it can be seen that according to this example, even if the pattern step changes, the variation in the detected diffraction light value 61 is small, and it is possible to detect the alignment mark on the wafer.

The above is a case where the pattern step difference is changed, but the same applies when the resist thickness d is changed.

FIG. 7 shows the five diffraction light detection values when a pattern with uneven resist coating is detected.

The horizontal axis corresponds to the direction of arrow When illuminated with light,
Detection signals of two diffracted lights, (C) and (D)
are the respective detection signals of two diffracted lights when illuminated with a laser beam having a wavelength of 0.543 p rrr, and (E) is the average value of (A) to (D).

From these figures, it can be seen that the respective detection signals are asymmetrical, but the averaged signals are symmetrical, and it can be seen that the effect of this embodiment is manifested.

In the above embodiment, the birefringent prism 15 was used as a means for tilting the irradiated light in FIG. 1(A), but a galvanic mirror may be provided instead of the birefringent prism.

In this case, first, by a ray of light traveling on the optical axis.

The alignment mark is illuminated and detected, and the detected image is recorded in memory. Next, the galvanic mirror is tilted, laser light is irradiated from an angle, the diffracted light is detected, the detected image is recorded in memory, and the image is detected by superimposing it with the image previously recorded in memory. do.

Furthermore, as means for tilting the irradiated light, an AO deflector, an EO
A deflector or thin film device may also be used.

In addition, although all of the above explained the method of detecting the diffracted light from the alignment mark, a birefringent prism is used as a means to tilt the irradiated light, and the specularly reflected light from the alignment mark is detected. An image may be determined and the position of its alignment mark may be determined.

The above has described the optical system for detecting one alignment mark, but in actual use, an optical system for detecting another alignment mark 36 (see Fig. 1) placed perpendicular to this is used. A system is necessary. This is simply the optical system described so far.

This can be achieved by installing it in a right angle direction.

Next, as a second embodiment, an alignment apparatus and a projection exposure apparatus using the alignment mark detection apparatus according to the first embodiment are shown in FIG.

In the figure, a reticle 1 on which an original image pattern is drawn and a reduction lens 4 are arranged below an exposure illumination light source 73 with the exposure axis 72 coincident with each other, and a reduction lens 4 is arranged below the reduction projection lens 4. XY with rotating stage 70 placed on top
The stage is placed.

The wafer 5 is placed on the rotation stage 70.

Further, in order to detect alignment marks, a laser emitting device and an alignment optical device are arranged in the same configuration as in the first embodiment.

The operation of this embodiment will be described below.

A predetermined position of the reticle 1 is aligned with the exposure axis 72 by the reticle position detection systems 7a, 7b. Next, the reference marks of the rotation stage 70 and the XY stage 71 are aligned to predetermined positions, and these positions are stored in the alignment correction device. Thereafter, the alignment mark on the wafer 5 is detected by the method described in Example 1, and this detection signal is sent to the alignment correction device. The rotation stage 7 stores this detection signal in advance.
0 and the reference mark position of the XY stage 71 by a drive device (not shown).
Slightly move the above two stages.

The circuit pattern drawn on the reticle L is illuminated by the exposure illumination light, so that the circuit pattern drawn on the reticle L is illuminated by the reduction projection lens 4.
is reduced in size and printed onto a predetermined position of the chip on the wafer 5.

As a result, in the conventional method, a detection deviation of about 0.1 to 0.3 μm may occur, but by using the device according to this embodiment, the detection deviation can be suppressed to about 0.03 μm.

Next, as a third embodiment, a semiconductor manufacturing plant using the second embodiment is shown in FIG.

As shown in the figure, in the semiconductor manufacturing plant of this embodiment, the entire process begins with one circuit design and ends with a sealing operation.

The feature of this embodiment is an apparatus that exposes a resist coated on a wafer with a pattern drawn on a reticle, and the other apparatuses used are those conventionally used.

Generally, semiconductors are manufactured by repeating the above exposure process many times, and in this example, a reduced image of an enlarged pattern drawn on a reticle is projected onto a wafer and formed. Expose.

In this reduction projection exposure step, the alignment mark detection device described in the first embodiment is used.

By using the above-described alignment mark detection device, only two laser light sources are required instead of four laser light sources as in the conventional method, and the structure is simplified and the size of the semiconductor manufacturing plant can be reduced.

[Effects of the Invention] According to the alignment mark detection device according to the present invention, when one illumination light is incident, it is separated into two distinguishable illumination lights, so the number of light sources is smaller than that of the conventional alignment mark. Only half the number of light sources in the detection device is required, the structure is simplified, and miniaturization and cost reduction can be achieved.

[Brief explanation of drawings]

Fig. 1 is an enlarged perspective view of the main part showing the first embodiment of the present invention, Fig. 2 is an explanatory diagram for explaining the optical path in the first embodiment, and Fig. 3 shows a detected image. Explanatory diagram, 4th
, 5 are explanatory diagrams showing the principle of the first embodiment, Figures 6 and 7 are explanatory diagrams showing the effects of the first embodiment, Figures 8 to 12 are diagrams explaining the prior art, and Figures 13 and 14. 15 is a process chart showing the third embodiment, and FIG. I6 is a perspective view showing the second embodiment. 1... Reticle, 2... Area showing a circuit pattern,
3a, 3b...Reticle alignment mark, 4...
Reduction projection lens, 5... Wafer, 11.12... Laser light source, 13.30-... Dichroic mirror, 1
4... Quarter wavelength plate, 5... Birefringent prism, 1
7...P polarized laser light, 18...S polarized laser light,
20...Half prism, 23...Vertical incident light, 24
... Inclined incident light, 25... Wafer alignment mark, 26.27, 53, 54, 56, 57... Diffracted light, 29.31... Real image, 32, 33... Photoelectric element , 50... TV monitor, 60... Pattern step difference of alignment mark on wafer, 61... Diffraction light detection value,
200... Laser emission device, 201... Positioning optical device, 102... Single wavelength illumination light, 106... Half mirror - 109... Resist, 110... Mark portion, 111... Resist part

Claims (1)

[Claims] 1. In a device for detecting alignment marks on a wafer in a projection exposure apparatus that exposes an original image pattern onto a wafer, at least two illumination lights of different wavelengths are emitted, one for each wavelength, means for separating the first light and second light into distinguishable light; means for causing the first light and the second light to have different incident angles to the alignment mark; An alignment mark detection device comprising: means for detecting diffracted light. 2. In a device for detecting alignment marks on a wafer in a projection exposure apparatus that exposes an original image pattern onto a wafer, means for converting at least two illumination lights of different wavelengths into circularly polarized light; and the illumination light made into circularly polarized light. means for splitting the light into S-polarized light and P-polarized light; means for making the incident angles of the S-polarized light and P-polarized light different on the alignment mark; and means for detecting reflected light from the alignment mark. An alignment mark detection device comprising: 3. A birefringent prism is used as a means for separating at least two illumination lights of different wavelengths into distinguishable first light and second light for each wavelength, and the optical paths are different from each other. 2. The alignment mark detection device according to claim 1, wherein the alignment mark detection device uses S-polarized light and P-polarized light. 4. An apparatus for aligning a reticle and a wafer, comprising the alignment mark detection apparatus according to claim 1, 2 or 3. 5. A projection exposure apparatus comprising the positioning apparatus according to claim 4. 6. In a method for detecting alignment marks on a wafer in a projection exposure apparatus that exposes an original pattern onto a wafer, at least two emitted lights of different wavelengths are separated into a first distinguishable light beam of each wavelength. Separate the light and second light, make the first light and second light have different incident angles to the alignment mark, detect the diffracted light from the alignment mark, and mark the alignment mark. An alignment mark detection method characterized by detecting an alignment mark. 7. When detecting alignment marks on a wafer, two laser beams with different wavelengths are split into S-polarized light and P-polarized light with different optical paths using a birefringent prism, and the S-polarized light and P-polarized light are An alignment mark detection method characterized by detecting the alignment mark by varying the incident angle of the light onto the alignment mark and detecting the reflected light from the alignment mark. 8. A semiconductor manufacturing plant comprising the alignment mark detection device according to claim 1, 2, 3, 4, 5 or 6.