JPH02192113A - Manufacture of semiconductor integrated circuit, pattern detecting method and device for semiconductor alignment and stepping reduced exposure used thereon - Google Patents

Abstract

PURPOSE:To conduct the detection of pattern accurately, and to make it possible to conduct an alignment operation in a highly precise manner by a method wherein, when an observation operation is conducted, an observation beam picked out from the lower part of a reticle is passed through a color-observation correcting lens. CONSTITUTION:A light source 8 with which a continuous spectrum light, having a least two or more wavelengths, is made to irradiate on the objective substance of exposure 5 through a projection-contracting lens 3, a recognition part 20 with which position recognition is conducted by having a ray of light which comes from the objective substance of exposure 5, and a color aberration correcting lens mechanism 16, which is provided on the optical path of the reflected light located between the objective substance of exposure 5 and the recognition part 20, are provided. To be more precise, the color aberration correcting lens mechanism 16 is provided on the optical path of the illumination light 8, and focal distance is adjusted corresponding to each wavelength. Accordingly, a continuous spectrum light of two or more wavelengths can be used as a pattern illumination light. As a result, even when photoresist film thickness is non-uniform and asymmetrical against the alignment pattern on the part of detection, the impossibility of detection caused by the asymmetry of the interference fringe such as a single wavelength light can be prevented, and the positioning accuracy when an alignment operation is conducted can be enhanced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to alignment technology, and in particular to alignment of a semiconductor wafer (hereinafter simply referred to as "wafer") with respect to a mask in a reduction projection exposure process in the manufacture of semiconductor devices. Concerning techniques that are effective when applied to

[Conventional technology]

A common technique for transferring a circuit pattern formed with a light-shielding film on a mask such as a reticle onto a wafer is to use a reduction projection exposure system, but the alignment of the wafer and mask at this time is , for example, as follows.

That is, illumination light is irradiated through a reduction projection lens to an alignment mark formed by uneven steps on the surface of the sea urchin, and the reflected light from the alignment mark is made to enter a TV camera via a beam splitter or the like. , the position of the alignment mark is determined by detecting an electrical signal based on the amount of reflected light,
This is to position the target exposure area of the wafer relative to the mask. Such a positioning technique is called a general second-through-the-lens (TTL) method.

By the way, a document that points out future problems with the TTL method mentioned above is "Nikkei Micro Devices" published by Nikkei McGraw-Hill, December 1, 1986, P70-P72.
There is.

Here, - Intra-film TTL alignment technology is used as the fifth
This will be explained using the system diagram shown in the figure.

That is, in FIG. 5, 71 is a wafer that is a non-exposure object, 72 is a reduction projection lens for exposure located directly above the wafer, 73 is a reticle as an original, 74 is a TV camera as a recognition unit, and 75 is an exposure unit. It is a mercury lamp that serves as both a light source and an illumination light source.

A reflecting mirror 76, a relay lens 77, and a beam splitter 78 are arranged on the optical path between the reduction projection lens 72 and the TV camera 74, and the light transmitted by the beam splitter 78 is incident on the TV camera 74. It has a structure.

On the other hand, a bandpass filter 80 and a condenser lens 81 are respectively arranged between the mercury lamp 75 and the beam splitter 78 to allow only the E-ray (546 nm) to pass among the wavelengths from the mercury lamp 75.

As described above, monochromatic E-line light is used as illumination light for pattern detection, and G-line (4a6 nm) exposure light is used during exposure.

The illumination light is irradiated onto the wafer 71 from the beam splitter 78 via the relay lens 77, the reflecting mirror 76, and the reduction projection lens 72, and this reflected light travels backward along the above path to the TV camera 7.
4, the waveform is detected based on the recognized image of the TV camera 74, and the wafer 71 as shown in FIG.
The structure was such that the center position of the upper alignment mark 6 was calculated.

Furthermore, in FIG. 17(a), 201 is a wafer that is an object to be exposed, 202 is a reduction projection lens for exposure placed directly above this wafer, 203 is a reticle as an original, and 204 is a recognition unit. A TV camera 205 is a mercury lamp as an exposure light source. The above reduction projection lens 2
On the optical path between 02 and the TV camera 204, there is a reflecting mirror 206,
A relay lens 207 and a half mirror 208 are respectively arranged, and the reflected light transmitted through the half mirror 208 is incident on the TV camera 204. On the other hand, between the mercury lamp 205 and the half mirror 208, E-ray (546
A bandpass filter 210 and a condenser lens 211 are respectively arranged to allow only wavelengths (nm) to pass through.

The illumination light emitted from the mercury lamp 205 is irradiated onto the wafer 201 from the half mirror 208 through the relay lens 207, the reflecting mirror 206, and the reduction projection lens 202, and the reflected light from the wafer 201 travels backward along the optical path. and entered the TV camera 204, and waveform detection was performed based on the recognized image of the TV camera 204.

FIG. 17(b) is a partial cross-sectional view schematically showing the alignment pattern 212 formed on the wafer 201. As shown in FIG.

The alignment pattern 212 is formed on the wafer 201 in synchronization with the wiring pattern, etc., and has a concave cross-sectional structure in which both ends of the inner circumference are formed in an edge shape. The wafer plane on which such an alignment pattern 212 is formed is irradiated with illumination light from vertically above, and the reflected light reflected from the wafer plane travels back along the same optical path as the illumination light. there was.

As shown in the figure, the alignment pattern 2 is formed on the wafer 201 in an ideal state without any distortion.
12 is formed, the resulting waveform shows a peak value at the edge of the pair, as shown in FIG. 3(c), and the coordinates of both peak values are XR1
From L, the center position of the alignment pattern 212 ((
Calculate XR+XL)/2) and use this as the reference value X. alignment was performed.

Further, as prior art that may be related to the present invention, there are the following, which will be briefly introduced.

Japanese Patent Publication No. 622937 by Meiki (5uzuki) et al.
No. 18 (published on December 21, 1987) describes a correction lens system for correcting spherical aberration, astigmatism, coma, etc. in a stepper having an alignment optical system using single wavelength light. .

Komoriya et al. Japanese Patent Publication No. 60-17
No. 7625 (published on September 11, 1985) shows an example of inserting a chromatic aberration correction lens system outside the axis of the on-axis alignment optical system in a stepper or the like that has an alignment optical system based on a continuous spectrum. .

Sugiyama (8ugiyama)'s Japanese Tokukai No. 61-20
No. 3640 (published on September 9, 1986) discloses a structure in which light extracted through a reticle or mask is guided to a detection system via a chromatic aberration correction lens in a stepper alignment optical system similar to the above. There is.

Furthermore, Shiba et al.'s Japanese Patent Publication No. 61-251
No. 858 (published on November 8, 1986) discloses the use of a cylindrical inner mirror in the supply path of the exposure light source.

[Problem to be solved by the invention]

However, the inventors have discovered that the reduction projection exposure apparatus having the structure shown in FIG. 5 has the following problems.

That is, the wafer, which is the exposure target, is provided to the reduction projection exposure apparatus with the photoresist film 82 coated thereon, but the photoresist film 82 is coated by rotating the wafer 71 and dropping the resist solution. This is done by utilizing the spread of the resist solution due to centrifugal force.

Therefore, due to the centrifugal force during the rotation, the coating thickness of the photoresist film 82 becomes unbalanced around the step of the alignment mark, and in particular, the deposited shape of the photoresist film 82 becomes asymmetrical with respect to the center of the step pattern. Here, as the illumination light for the above alignment, it is common to use the G-line (436 nm) used for exposure with a single wavelength (monochromatic light), so the light reflected from the original step pattern and the photo The interference fringes generated by the reflected light from the resist film 82 become asymmetrical, and the signal voltage waveform obtained from the interference fringes, which is an image recognized by the TV camera, also becomes asymmetrical and complicated. As a result, the detection of the step pattern of the alignment mark becomes difficult. Sometimes it was difficult.

Regarding this point, although several solutions have been introduced in the above literature, none of them can be said to provide a sufficient solution.

Furthermore, in FIGS. 17(a) to (c1), when forming the Al of the alignment pattern 212, variations in the film thickness at the bottom of the step occur, and if the cross-sectional shape of the alignment pattern 212 becomes asymmetrical, the angle of light reflection changes. This may cause distortion in the waveform of the detected edge, making it difficult to accurately determine the coordinates of the edge position.

Furthermore, if the tip of an edge has a chip, etc., the chip may be caused by diffused reflection from the surface, making it difficult to grasp the coordinates of the edge position.

The present invention has been made in view of the above problems, and its purpose is to provide a technique that can reliably detect a pattern on a wafer coated with a photoresist film and realize highly accurate alignment.

An object of the present invention is to provide a technique that can accurately detect edge coordinates and improve alignment accuracy without being affected by distortion of an alignment pattern.

One object of the present invention is to enable stepper alignment with multicolored or "white" light.

One object of the present invention is to provide a reference optical system for a stepper that can accurately remove various aberrations.

One object of the present invention is to provide a stepper that allows easy time-series control of reduction magnification and the like.

One object of the present invention is to provide a position detection method that is compatible with a two-layer Al process.

The present invention provides a D
The object of the present invention is to provide an exposure process that is compatible with the wafer process of memory ICs such as RAM.

One object of the present invention is to provide a Köhler (
Koler) aims to provide a method for improving lighting.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

That is, a light source that illuminates an object to be exposed with continuous spectrum light of at least two wavelengths or more through a projection reduction lens, a recognition section that performs position recognition by receiving reflected light from the object, and a recognition section that performs position recognition by receiving reflected light from the object. The structure includes a chromatic aberration correction lens mechanism provided on the optical path of reflected light between the exposure target and the recognition section.

[Effect]

According to the above means, by providing a chromatic aberration correction lens mechanism in the optical path of the illumination light and adjusting the focal length corresponding to each wavelength, continuous spectrum light of two or more wavelengths or more is used as the pattern illumination light. becomes possible. Therefore, for example, even if the photoresist film thickness is uneven and asymmetrical with respect to the alignment pattern of the detection area, it is possible to prevent detection failure due to asymmetrical interference fringes such as single wavelength light, and it is possible to prevent Accuracy can be increased.

〔Example〕

Hereinafter, the improvements of the present invention will be explained in terms of each embodiment, but these are mutually replaceable components or parts of an integrated invention, and the embodiments are not independent of each other.

Therefore, if the last two digits of the reference numbers in the drawings are the same,
Unless otherwise stated, in principle, they shall perform the same or similar functions.

(1) Embodiment 1 FIG. 1(a) is a perspective view of the main parts of a reduction projection exposure apparatus which is Embodiment 1 of the present invention, and FIG. 1 (bl is a system diagram showing the optical system of this embodiment) , FIGS. 2(a) and (bl are explanatory diagrams showing the chromatic aberration correction lens, respectively, FIG. 2 (c1 is a perspective view showing the astigmatism correction lens used in this example, and FIGS. c) is an explanatory diagram conceptually showing the correction principle by the chromatic aberration correction lens in the example, and Fig. 4(a)
) and (b) are explanatory diagrams showing the relationship between alignment marks formed on the wafer and detected waveforms.

The reduction projection exposure apparatus of this embodiment includes an exposure light source 1 made of a mercury lamp, a condenser lens 2 that focuses exposure light (not shown) emitted from the exposure light source 1, and a reduction projection lens 3.
It has an exposure optical system consisting of.

Between the condenser lens 2 and the reduction projection lens 3, a reticle (original plate) 4, which has an integrated circuit pattern formed on a transparent quartz glass substrate or the like with a light-shielding film such as chromium (CR), is removably arranged. There is.

On the other hand, below the reduction projection lens 3 is a wafer (
An exposure target (object) 5 is placed.

The wafer 5 has a predetermined alignment mark 6, etc.
As shown in Figure (al), it is formed in a step-like shape, and a photoresist film 7 is further deposited on its upper surface by a spin coating technique.

That is, in FIG. 1 (al), the exposure light emitted from the exposure light source 1 and transmitted through the reticle 4 is reduced to a predetermined magnification (for example, 115) by the reduction projection lens 3 and projected onto the wafer 5. A photoresist film 7 coated on the surface of the photoresist film 7 is exposed in a predetermined pattern.

An illumination light source 8 (1!1) is provided near the exposure optical system, and the illumination light from this illumination light source 8 passes through a bandpass filter 10 and a condenser lens 11 provided on its optical path to a half mirror. - The structure is such that the light is incident on the beam splitter 12 of the structure.

In this embodiment, the illumination light source 8 is guided by the exposure light source 1 through a light guide means such as an optical fiber 13, and is constituted by a cylindrical mirror 14 attached to the tip thereof.

The bandpass filter 10 is configured to, for example, emit E-line (546 nm) among the emission wavelengths of a mercury lamp, which is the exposure light source 1.
The illumination light that has passed through the bandpass filter 10 is passed through the beam sinter 1 as continuous spectrum light in the visible light range.
2. On the optical axis of the beam splitter 120,
A relay lens 15, a chromatic aberration correction lens 16, and an astigmatism correction lens 17 are provided, respectively, and are structured to reach a reflecting mirror 18 provided on the body of the reduction projection lens 3.

(2tlJ On the other hand, on the optical axis of the beam splitter 120, at a position symmetrical to the relay lens 15, a TV right camera 0 serving as a recognition unit is arranged via the relay lens 15.

Next, the chromatic aberration correction lens 16, which is a characteristic component of this embodiment, will be explained in detail.

Prior to the explanation, we will explain the chromatic aberration in Figures 6(a) and (
To explain based on b), a and b in the figure each indicate the distance from the lens 21 to the imaging position. Here, if the focal length of the lens 21 is f, then a, b
, f is expressed as follows. Here, the change Δb in the imaging position when the focal length changes by Δf becomes Δb=□△f from the above equation (1). On the other hand, as shown in FIG. 8(b), the lens 21
The relational expression between the focal length f and the refractive index n is as follows.

In the above equation (3), R indicates the radial length of the spherical surface of the lens 210.

From this equation (3), the change Δf in the focal length due to the change Δn in the refractive index is as follows, and when this is substituted into the equation (2), it becomes. Here, since the imaging magnification m is m = b/a, the above equation (5) becomes as follows.

From this equation (6), it can be understood that the imaging position also changes by Δb due to the change Δn in the refractive index. Here, since the wavelength of light and the refractive index n are inversely proportional to each other, as the wavelength becomes longer, the imaging position shifts toward the bending lens 21. This is chromatic aberration. Generally, the reduction projection lens 3 used in a reduction projection exposure apparatus is designed to have optimal optical characteristics for the G-line, which is the exposure light. The focal length shift is not taken into account.

Therefore, when using continuous spectrum light consisting of E-rays and D-rays to prevent detection failure due to interference fringes, the short-wavelength E-rays are focused relatively close to the lens, and the long-wavelength rays are focused relatively close to the lens.
As a result, the line is imaged far from the lens, and according to the inventor's calculations, the ゛P of both wavelengths that passed through the alignment optical system
(2) The difference in image formation position in the camera 20 has reached several tens of millimeters.

In this embodiment, this problem is solved by the chromatic aberration correction lens 16.

In other words, the chromatic aberration correction lens 16 has the function of maintaining the imaging position constant regardless of the magnitude of the incident wavelength, and reduces the imaging distance for light with a small incident wavelength, that is, a small refractive index. On the other hand, for light with a small incident wavelength, that is, a large refractive index, the imaging distance is adjusted to be close.

This chromatic aberration correction lens 16 is, for example, shown in FIG. 2(a).
(As shown in bl, a concave lens 16a made of flint glass and a convex lens 16 made of crown glass.
In this embodiment, a pair of chromatic aberration correcting lenses 16 and 16 having the above configuration are used. Note that the combination shown in fbl in the figure may also be used. In this embodiment, the chromatic aberration correction lens 16 has a wavelength λ==500 nm to 500 nm as the chromatic aberration correction range.
It is sufficient that it can correct chromatic aberration in a wavelength band including E-line and D-line of about 9 Qnm, and the chromatic aberration correctable range can be adjusted by changing the distance between the pair of chromatic aberration correction lenses 16. .

The principle of the above-mentioned chromatic aberration correction lens 16 is conceptually illustrated in Figure 3 (al to (c1), where (al is the imaging distance when E-line monochromatic light is incident before chromatic aberration correction). fe, (bl is also the imaging distance fd, (c
1 indicates the imaging distance fs of the E-line and the D-line, respectively, when the chromatic aberration correction lens 16 is placed on the optical path to correct the chromatic aberration. In the figure, the imaging distance fs is (al and (b)
), that is, approximately fs=(fe+
fd)/2. therefore,
When continuous spectrum light of E-line and D-line is used as illumination light, chromatic aberration can be suppressed and the imaging position can be kept constant. Therefore, the inability to detect the position due to the asymmetry of the interference fringes that occurs when monochromatic light of only the E line or the D line is used can be prevented, and the alignment pattern can be detected with high precision by the TV left camera 0.

In this embodiment, an astigmatism correction lens 17 as shown in FIG. 2(c) is provided between a pair of chromatic aberration correction lenses 16 on the optical path. The astigmatism correction lens 17 is for correcting the shift in the XY direction of the detected image on the wafer 5 caused by the astigmatism ray bundle, that is, the astigmatism, and is a convex lens 17a made of a cylindrical lens.
and a concave lens 17b. Therefore, according to this embodiment, illumination light whose chromatic aberration and astigmatism have been corrected is incident on the 'rV camera 20, so that position detection based on highly accurate image g recognition is possible.

Next, the alignment method according to this embodiment will be explained.

First, by moving the XY stage, illumination light is emitted from the cylindrical mirror 14 at the tip of the optical fiber 13, which is the illumination light source 8. After passing through the bandpass filter 10 and the condenser lens 11, it is refracted by the beam splitter 12. The illumination light passes through the relay lens 15 , the chromatic aberration correction lens 16 , the astigmatism correction lens 17 , the reflecting mirror 18 , and the reduction projection lens 3 to illuminate a predetermined area of the wafer 5 . The reflected light from the wafer 5 travels backward along the above-mentioned path, passes through the reduction projection lens 3, the reflecting mirror 18, the chromatic aberration correction lens 16, and the astigmatism correction lens 17, and reaches the beam sinter 12. Here, the reflected light passes through the beam splitter 12 and reaches the TV camera 20 via the relay lens 15. A signal processing section (not shown) is connected to the TV camera 20, and a signal waveform is detected from the image recognized by the 'lf' V camera 20.

FIG. 4(b) shows this signal detection waveform.

According to this embodiment, the chromatic aberration correction lens 1 is placed on the optical path of the illumination light.
6, the chromatic aberration, that is, the shift in the imaging position, is corrected even when continuous spectrum light of E-line and D-line is used as illumination light. As a result, when monochromatic light is used as the illumination light source 8, the difficulty in detecting the alignment mark 6 due to the interference waveform caused by the non-uniformity of the photoresist film thickness can be avoided, and the alignment mark 6 can be easily detected as shown in FIG. The detection signal corresponding to the stepped portion of the mark 60 can be reliably grasped, and the position of the alignment mark 6 can be detected accurately.Based on the position of the alignment mark 6 obtained in this way, the position of the wafer 5 is determined. The target area is accurately positioned on the exposure optical system, and then the integrated circuit on the reticle 4 is exposed by exposure light (not shown) emitted from the exposure light source 1 and passed through the condenser lens 2, reticle 4, and reduction projection lens 3. The pattern is transferred onto the photoresist film 7 of the wafer 5.

In the above description, a case has been described in which a mercury lamp, which is an exposure light source, is used as an illumination light source, but an independent xenon lamp may be used as a detection light source.

In this case, by using a xenon lamp that has relatively uniform light energy at each wavelength, continuous spectrum light can be selectively employed, and the correction rate of the chromatic aberration correction lens 16 can be adjusted to provide optimal correction. By setting the value, it is possible to prevent pattern detection from being impossible due to interference of reflected light, and it is possible to perform highly accurate position detection.

Although the invention made by the present inventor has been specifically explained based on the examples above, the present invention is not limited to the above-mentioned examples, and it is possible to make various changes without departing from the gist of the invention. Not even.

For example, although a cylindrical mirror attached to the tip of an optical fiber is shown as an example of the illumination light source, the illumination light source is not limited to this and may be of any shape such as a polygonal column body or a polygonal conical cylinder body.

In the above explanation, the invention made by the present inventor was mainly applied to the alignment technology in the so-called reduction projection exposure of wafers, which is the field of application of the invention, but the invention is not limited to this (but is not limited to this). It can be widely applied to alignment technology in reduction projection exposure.

A brief explanation of the effects obtained by typical examples among the above embodiments is as follows.

That is, according to the present invention, by providing a chromatic aberration correction lens mechanism in the optical path of the illumination light and adjusting the focal length in accordance with each wavelength, continuous spectrum light of two or more wavelengths or more is used as the pattern illumination light. becomes possible. Therefore, even if the photoresist film thickness is uneven and asymmetrical with respect to the alignment pattern of the detection area, for example, it is possible to prevent detection failure due to interference such as single wavelength light, and improve positioning accuracy during alignment. Can be done.

(2) Embodiment 2 (■) FIG. 7 is a perspective view of the main parts of a reduction projection exposure apparatus used in Embodiment 2 (I) of the present invention, and FIG. 8 is a system for explaining its optical system. 9(al) and (b) are explanatory diagrams showing the inclination state of the optical axis by the optical axis moving unit, and FIG.
Figure 0 (al and (b) is an explanatory diagram of chromatic aberration in the example, Figure 11 (al and (bl) is a partial cross-sectional view showing the formation state of the alignment pattern on the wafer and its plan view, Figures 11- FIG. 14 is an explanatory diagram showing the pattern detection method of this embodiment, and FIGS. 15(a) and (bl) are flow diagrams showing the signal processing procedure in pattern detection of this embodiment.

In FIG. 7, a reduction projection exposure apparatus 101 includes an exposure optical system consisting of an exposure light source 102 made of a mercury lamp, a condenser lens 103 that focuses exposure light emitted from the exposure light source 102, and a reduction projection lens 104. have.

Between the condenser lens 103 and the sardine small projection lens 104, there is a reticle 105 on which an integrated circuit pattern is formed on a transparent quartz glass substrate with a light-shielding film made of chromium (CR) or the like.
(Original version) is arranged in a removable manner.

On the other hand, in the figure, below the reduction projection lens 104 is an
On the upper surface of the Y stage 106, a wafer 107 (object to be exposed) whose position can be adjusted in the horizontal direction is placed. The wafer 107 has a predetermined alignment pattern 108 formed in a stepped shape as shown in FIG. 11, and a photoresist film 1 on the upper surface.
10 was applied by spin coating technique. That is, in FIG. 7, the exposure light emitted by the exposure light source 102 and transmitted through the reticle 105 is reduced to a predetermined magnification (for example, 115) by the reduction projection lens 104 and projected onto the wafer 107. As a result, the integrated circuit pattern of the reticle 105 is transferred onto the photoresist film 110, and the photoresist film 110 in the portion irradiated with the exposure light undergoes a chemical change, and the photoresist film 110 undergoes a chemical change.
A resist pattern according to No. 10 is formed.

An illumination light source 111 is provided near the exposure optical system, and the illumination light from this illumination light source 111 passes through a condenser lens 112, an optical axis moving section 113, etc., and is reflected by a half mirror 114 onto dust of a predetermined angle. The light then passes through a relay lens 115, a chromatic aberration correction lens group 116, and a reflecting mirror 117 to reach a reduction projection lens 104, and further illuminates a predetermined portion of the wafer 107 from this reduction projection lens 104.

In this embodiment, the illumination light source 111 is the exposure light source 1.
02, the light is guided by a light guiding means such as an optical fiber 118, and a bandpass filter 120 is placed on the optical path to select E (λ546 n m) and D line (λ-5
The structure is such that only light (89 nm) is transmitted. The illumination light transmitted through the band pass filter 120 is transmitted to the half mirror 114 as continuous spectrum light in the visible light range.
It will be injected into. The advantage of using such continuous spectrum light is that it prevents interference fringes caused by monochromatic light and improves detection accuracy.

Chromatic aberration correction lens group 116 from the half mirror 114
The illumination light irradiated onto the wafer 107 via the reflecting mirror 117 and the reduction projection lens 104 irradiates a predetermined alignment pattern 108 formed on the wafer 107, and then, as the reflected light, the optical path of the illumination light is The structure is such that the light travels backwards and enters the TV left camera 21. Note that the optical path of this illumination light will be described in detail later.

The optical axis moving section 113 includes a shutter 123 formed through an illumination aperture hole 1220, and a shutter support section 1 that is slidable along a guide 124 together with the shutter 123.
25, and this shutter support part 125 is moved by a step motor 126 or the like in FIGS.
As shown in , it is possible to make fine adjustments by 10 liters in the horizontal direction.

That is, when the shutter 123 is moved by a predetermined amount l in the horizontal direction due to the movement of the step motor 126, the illumination aperture hole 122 provided in the shutter 123 is also moved by 10 l in the left-right direction of the figure, which is the optical axis. The optical axis of the illumination light for the condenser lens 112 is inclined at a predetermined angle.

Due to the inclination of the optical axis, the reduction projection lens 1
Alignment pattern 108 of wafer 107 through 04
The illumination light irradiated upward is also tilted at a predetermined angle. In this embodiment, the vertical reference optical axis, that is, the shutter 12
The illumination light can be incident on the alignment pattern 108 at an angle of 10 by moving the illumination light a predetermined distance by ±4 to the left and right around an axis perpendicular to the plane of FIG.

Next, the chromatic aberration correction lens group 116 used in this embodiment
I will explain about it.

Prior to the explanation, the principle of chromatic aberration that occurs in the reduction projection exposure technique will be briefly explained using FIGS. 10 (al and (bl).

Note that a and b in the figure each indicate the distance from the lens 220 to the imaging position. Here, the above lens 2
If f is the focal length of 20, the relational expression of a, b, and f is
As is generally known, the process is as follows.

1/a+1/b=1/f, ・(t) At this time, if the focal length changes by △f, the change △b in the imaging position is △b-(b2/f2)△f... (2
). On the other hand, as shown in FIG. 10 (bl), the relational expression between the focal length f and the refractive index n of the lens 220 is as follows.

f=R/(n-1)°° (3) In the above equation, R indicates the radial length of the spherical surface of the lens 2200. From this formula, the change △f in the focal length due to the change △n in the refractive index is △f=-R△n/(n-1)" -f△n/(n-1) ... (4) By substituting this equation (4) into the above equation (2), △b
==-b2△n/f (n-1) ・”(5
). Here, since the imaging magnification m is m=b/a, the above equation (5) is as follows: △b,4-f(1+m)2△n/(n-1)-(6
). From this equation (6), it can be understood that as the refractive index n changes Δn, the imaging position also changes by Δb.

Here, since the refractive index n and the wavelength of light have a characteristic that is inversely proportional to the wavelength of light, as the wavelength incident on the lens 220 becomes longer, the imaging position also changes by Δb from the lens 220.
shift towards the direction of. This is chromatic aberration.

In general, the reduction projection lens 104 used in the reduction projection exposure apparatus 101 uses G-line (λ-436
Since it is designed to obtain optimal optical characteristics for wavelengths (nm), no consideration is given to the problem of chromatic aberration when using light of other wavelengths such as E-line or D-line as illumination light.

Therefore, as explained above, when continuous spectrum light consisting of E-line and D-line is used as illumination light, the E-line, which has a relatively short wavelength, is imaged near the lens, and the D-ray, which has a relatively long wavelength, forms an image near the lens. The line ends up being imaged far from the lens, and according to the inventor's calculations, the TV camera 1 of both wavelengths passes through the alignment optical system without performing chromatic aberration correction.
The difference in the imaging position due to 21 is about several tens of inches.

The chromatic aberration correction lens group 116 of this embodiment is used to correct the above-mentioned chromatic aberration, that is, the shift in the imaging position when continuous spectrum light is used as illumination light.

In other words, the chromatic aberration correcting lens group 116 of this embodiment has a function of maintaining the image formation position constant regardless of the magnitude of the incident wavelength, and is suitable for light having a large incident wavelength, that is, a small refractive index n. The imaging distance from the lens is adjusted to be small, and the imaging distance from the lens is adjusted to be large for light having a small incident wavelength, that is, a large refractive index.

The configuration of the chromatic aberration correction lens group 116 is, for example, a combination of a concave lens made of flint glass and a convex lens made of crown glass.
It is possible to correct chromatic aberration in a wavelength band that includes lines.

The range in which chromatic aberration can be corrected can be easily adjusted by changing the distance between the lenses of the combination lens.

11(al) and (b) show in detail the cross-sectional structure and planar structure of the alignment pattern 108 formed on the wafer 107. FIG.

That is, on the upper part of the semiconductor substrate 131 made of silicon (Si) semiconductor, there is a first pattern 131a formed of aluminum (Al) or the like in synchronization with the formation of a wiring pattern (not shown). pattern 13
The edge shape (L, R) of 1a is reflected on the upper layer to form second and third patterns 131b and 131C. The procedure for forming each pattern 1318rc will be described in more detail below.

First, a first pattern 131a is formed on a semiconductor substrate 131 in synchronization with a first layer wiring (not shown) forming process, and then a first insulating film 13 is formed through a photoresist process.
2a is formed. The first insulating film 132a is initially formed to cover the entire surface of the alignment pattern 108, and then the first insulating film 132a on the upper surface of the first pattern 131a is etched away through a photoresist process again. As a result, the above first pattern 1
The surface of 31a is exposed. In this state, the second pattern 131b is formed in synchronization with the second layer wiring. As described above, in this embodiment, the first pattern 71318 and the second pattern 131b are directly stacked without intervening the first insulating film 132a, so the interposition of the insulating film may be the cause. Pattern distortion and the like are relatively prevented.

After forming the second pattern 131b, a second insulating film 132b is formed again by a photoresist process, and this second insulating film 132b is further partially etched away to expose the second pattern 131b. Ru. Thereafter, a third pattern is formed on this second pattern 131b in the same procedure as above.

As shown in the margins below, according to this embodiment, the first to third patterns 131a to 131C are stacked directly without an intervening insulating film, so even in the third pattern 131C, Lower layer first and second patterns 13]a, 131b
The shape is reflected in the structure with relatively undistorted edges.

Next, an alignment procedure using the alignment pattern 108 (third pattern) formed in 17 as described above will be described. Note that the alignment pattern 108 shown in FIGS. 12 to 14 is shown as a dark line [, , t] for convenience of illustration, but the alignment pattern 108 shown in FIG. It has a 4A- structure, which is almost the same as the Kasumicho-men structure.

FIG. 12 shows a case where the alignment pattern 108 is formed in a symmetrical shape, that is, without distortion, and FIG. Processing shimmer, for example the first and second patterns in silk 11 Figure 13]b
This is caused by uneven film thickness, and the 12th
The figure shows a case where the edge portion of the alignment pattern 108 is chipped.

As shown in FIG. 12, when the alignment pattern 108 is formed in an ideal state with a substantially symmetrical shape, the alignment method in the prior art, that is, only straight light from the vertical direction (vertical 11 illumination light S) is sufficient. Sufficient alignment accuracy can be achieved. However, [7] In the actual manufacturing process of the wafer 7, it is impossible to always form the alignment pattern 8 in a symmetrical shape as described above.
I L, < , the alignment pattern 8 often has an H-valve symmetric shape as shown in FIGS. 13 and 14.

In the following explanation of the alignment procedure, first, a case where the alignment pattern 8 is formed in a symmetrical shape as shown in FIG. 12, and a case where the alignment pattern 8 is formed in a sharply asymmetrical shape as shown in FIGS. 13 and 14 will be explained.

When illumination light is emitted from the illumination light source [1] by moving the XY stage 106, it reaches the shutter 123 through the condenser lens 112.
The illumination diaphragm of -4 is set by the operation of the step motor 126.
The illumination light passing through the illumination diaphragm 122 is moved in the direction of -θ from the vertical reference optical axis (Fig. 9 (bl)).
The light travels to the subsequent alignment optical system in a tilted state.

The illumination further passes through the relay lens II5 and the chromatic aberration correction once group 116. At this stage, the chromatic aberration due to the continuous spectrum source has been corrected, and the illumination light is further reflected by the reflected ml
17. At this time, the illumination light (ii. detection light) fd is deviated from the vertical reference optical axis by the movement of the shutter 123 on the optical path. In this state, the alignment pattern 108 is irradiated. Show this condition! , Tanoga 941
Figure 2(a) shows this. In the same figure (with respect to the vertical reference optical axis in the alignment pattern 108, the inclination angle -
It is irradiated as R detection light from diagonally above θ.

As described above, the alignment butter irradiated with light from the R
Although the detection light travels backward through the optical path and enters the 1'v camera 121, the waveform signal photoelectrically converted through the TV camera 121 continues as shown in FIG. In the figure, the part where the signal waveform has a valley shape is the edge position of the alignment pattern 108, and by reading this coordinate, one canvas (XL) of the alignment pattern 108 can be determined.
It is also possible to recognize the edge position on the L side (XR).

Here, as is clear from the figure, the R detection light having such an inclination angle of -0 is influenced by the left edge L of the alignment pattern 108 shown in figure (a). Towa affects the waveform signal, and the left side (L
) is no longer possible to accurately detect the edge position XL. (7 or 17, right side (H)) Since the edge detection waveform does not include any noise components such as the influence of illumination due to edge H, the R edge position XR is accurately detected.

[7. Therefore, when the edge position is detected using the R detection light, flj% only the edge position data XR on the R side is used] 1. The position data XL containing noise components on the L side is not used.

Next, the step motor 126 is further operated and the shutter 123 is at the 10 l position (FIG. 9(d)).
The illumination light E7 having an inclination angle of 10 with respect to the vertical reference optical axis passes through the optical path and is irradiated onto the alignment pattern 108. The illumination light at this time is tilted by +θ with respect to the reference axis in the alignment pattern 108 to become iL detection light, as shown in FIG. 12(e).

Figure (1) shows the detected waveform at this time, and R
Detection of the edge position Reliably detected.

In addition, at this time, only the edge position data iL side (XL) obtained by the L detection light is used, and the position data XR of RIJ that includes noise components is not adopted.

In this way, in this embodiment, each edge position t(X
t, , Xa), the R edge position and the L edge position are detected using detection lights (R detection light and L detection light) each having an appropriate inclination angle (±θ). .

It should be noted that although the explanation has been repeated, when the shutter 123 is at the 10 position due to the operation of the step motor 126, that is, when the illumination aperture hole is located on the vertical reference optical axis, the illumination light is vertically illuminated. The light S and (2) are the same as those of the prior art. Such vertical illumination light S is
As shown in figures (a), (c) and (e),
As long as the alignment pattern 108 is in an ideal state, that is, the cross-sectional shape is symmetrical and formed with high precision, the edge positions (Xt,

XR) both allow accurate position detection.

However, if the cross-sectional shape of the alignment pattern 108 is asymmetrical, the reflected light may contain noise components due to effects such as diffused reflection! ), it is often difficult to accurately detect the position depending on the waveform of the detection signal from the TV camera 121.

Next, a case in which the cross-sectional shape of the alignment pattern 108 is asymmetrical, that is, a case in which the alignment technique of this embodiment is most effective will be described.

As shown in FIG. 13, the alignment pattern 108 is
If the bottom surface of the step is inclined at an angle of, for example, 2 to 5 degrees, the vertical illumination light S as shown in FIG. contains noise.

Regarding this point, in this embodiment, as described above and using the R detection light, it is possible to accurately detect the H edge position (Xa) as shown in Figure 1). [2] However, with the vertical illumination light S of the prior art, as shown in Fig. 13(c) K, when detecting edges on the l( side, the reflected light due to the inclination of the bottom surface is added as a noise component, so It is difficult to detect the R edge position ((d) in the same figure).

[7] (For this reason, when detecting edges on the L side, as shown in (e) and (f) in the same figure, by using the L detection light having an inclination angle of 10, it is possible to accurately detect the edges on the L side.) Similarly, when detecting an edge on the R side, by using the R detection light having an inclination angle of 1θ, as shown in the same figure) and (c), it is possible to detect an edge on the R side. Accurate edge detection is possible.

By the way, the cause of the noise component when only the vertical illumination light S is used is that in addition to the case where the bottom surface of the step is inclined as shown in FIG. In some cases, sag 133 is generated at the corner.

That is, as shown in FIG. 14(c), the sagging surface 133
When the vertical illumination light S is irradiated onto the alignment pattern 108 that is causing the sag, the L with the sagging surface 133 is caused by diffuse reflection from the sagging surface 133, as shown in FIG.
Noise is generated in the detection waveform of the edge on the side, making it difficult to accurately detect the edge position on the L side.

Even in such a case, according to this embodiment, (4)
By using the R detection light shown in FIG. 1, it is possible to accurately detect the R edge position XR, and on the other hand, by using the L detection light, it is possible to accurately detect the pL edge position tXt. (By using the R air 9 position data xR obtained by the R detection light and the L error position data XL obtained by the L detection light, the R Accurate detection of both side and L side edge positions is possible.

The edge detection explained above can be applied to the 15th level of signal processing.
The process will be explained below using the flowchart shown in FIG.

First, the R edge position is detected using the R detection light, and the coordinates of this detected position are set to XR (step 251 in FIG. 15(a)). Note that the L Eso 9 position data at this time is not adopted.

Next, the L edge position is detected using the L detection light, and the coordinates of this detected position are set as XL (step 252). At this time, R Eso 9 position data is similarly adopted (7 is not available).

The average coordinate of XR and XL thus obtained is calculated and recognized as the pattern reference position coordinate Xo (step 253).

Next, a case will be described in which the asymmetry of the alignment pattern 108 is detected by using the R detection light, the vertical illumination light S, and the L detection light described above (7).

First, X is generated by the signal processing shown in FIG. 15(a).

After determining (step), the above alignment pattern 1
Vertical illumination light S was applied to 08 (7) as shown in each (c) of Figs. 12 to 13, and the R detection position coordinate (ZR) and L detection position coordinate (ZL) at this time were After getting and
Zo, which is the average value of these, is calculated (255). Of course, either of the coordinates ZR, ZL (R Eso 9 position data, L Eso 9 position data) obtained at this time contains a noise component as explained above, so the Zo obtained from this also has a true value. isn't it.

Next, ΔZ is calculated by subtracting Xo obtained in step 253 from Zo (256).

This △Z is Z for the true pattern reference position leader @xoo
The amount of deviation of o will be calculated. Therefore, in the subsequent alignment process, by adding ΔZ, which is the zOK correction amount obtained from the vertical illumination light S, it is possible to obtain the true pattern reference position coordinates XO without using the R detection light and the L detection light. Can be done.

In this way, in this embodiment, the pattern reference position coordinates X are determined using the R detection light and the L detection light.

After determining , in the subsequent alignment work, it is possible to accurately recognize the pattern position for each alignment pattern 8 by simply performing arithmetic processing that adds the correction amount ΔZ to the detected value by the vertical illumination light S. .

FIG. 16 is a partial system diagram showing the arrangement of illumination light sources in a reduction projection exposure apparatus which is Embodiment 2 of the present invention.

In Example 2 (2), the illumination light sources are arranged at two locations (7
The same effect as I of Example 2 is obtained (5).

That is, the first illumination light source 141a is arranged so that the detection light R and the detection light R are incident on the alignment pattern 108 at an angle of +θ relative to the vertical reference optical axis, while the second illumination light source 141b is −θ relative to the vertical reference optical axis.
It is arranged so that it is incident on the alignment pattern 108 as a detection light at an angle of .

Such first and second illumination light sources 141a1141
As b, the optical fiber 1 is used as in 1 of Example 2 above.
18 may lead from the exposure light source 102. Alternatively, an independent light source may be provided.

In this embodiment, the first illumination light source 14
By switching the illumination between 1a and the second illumination light source 141b, it is possible to obtain the R detection light and L detection light similar to I in Example 2, and it is possible to accurately detect the edge position. Become.

Above, the invention made by the present inventor is explained in detail based on examples (7k, but since the present invention is limited to the above-mentioned examples, it is possible to make substantial changes without departing from the gist of the book). Being that is not a good thing.

For example, in the embodiment, (as the illumination light source 111,
The mercury rank light from the exposure light source 102 is transferred to the original fiber 11.
8 Regarding the case of guiding with glue, Pilgrimage, Light,
Independent as 1111. A xenon lamp or the like may also be used. By using a xenon rung that emits a relatively uniform energy key at each wavelength, it is possible to selectively employ continuous spectrosim light, resulting in more accurate pattern detection without interference fringes. I can do one thing.

The above explanation mainly describes the case where the invention made by the present inventor is applied to the field of application, which is alignment technology in so-called reduction projection exposure.
However, this is limited to h <, even if l−
It can also be applied to alignment technology between a photomask and a wafer in 1:1 exposure.

A brief explanation of the effects obtained by a representative (5 seconds) invention disclosed in this example is as follows.

That is, by irradiating the illumination light with a predetermined inclination angle relative to the vertical reference light of the pattern, it becomes possible to accurately detect the position of one of the edges at both ends of the pattern. Therefore, if the pattern being formed is distorted by changing the bevel angle by one angle in this way and irradiating the pattern with illumination light, the pattern may have an asymmetrical cross-sectional shape. Accurate position detection is also possible, and alignment accuracy can be improved.

Vertical illumination is calculated by comparing the first coordinate value obtained by irradiating the detected light from the bent direction with the second coordinate value obtained from the vertical illumination light. Since the amount of deviation due to light detection is clearly large, efficient alignment processing can be performed in subsequent position detection by correcting data obtained only from vertical illumination light.

(3) Embodiment 18 FIG. 1 is a perspective view showing the main parts of a reduction projection exposure apparatus equipped with an alignment device according to embodiments 1 and 3 of the present invention, and FIGS. 19 and 20 show its light source. It is an explanatory diagram showing a portion taken out (7).

The reduction projection exposure apparatus in this embodiment includes exposure light 'yp, 301 slipping from, for example, a mercury lamp, and a condenser lens 3 that converges the exposure light emitted from this exposure light source 301.
02 and a reduction projection rank 302.

For information on mercury lamps and other snap-pin, reduced grosgeection, and aligners, please contact Ichiro Hau.
Author [Semiconductor link graphing technology] 2nd edition May 3, 1986
0 (published by Sangyo Zuho Co., Ltd.), pages 81 to 102, it is not explained, so the description of the present application will be changed therefrom.

Between the condenser lens 302 and the reduction projection rank 303,
A target integrated circuit pattern is enlarged to a predetermined magnification (for example, 5 times) on a transparent glass substrate, etc., and a light-shielding film with a shape of 7 is coated on it. It is arranged.

Further, below the reduction projection lens 303, it is placed on an X-Y stage, and is movable in a horizontal plane, and a photoresist film 305a is coated on the surface by spin coating or the like in the previous coating process. A semiconductor wafer 305 (object to be exposed) attached thereto is positioned.

Then, the exposure light emitted from the exposure light source 301 and transmitted through the original plate 304 is reduced to a predetermined magnification (for example, 115) by the reduction projection lens 303.
By projecting the photoresist film 305a onto the surface of the semiconductor wafer 305, the photoresist film 305a is exposed to form an integrated circuit pattern of the original size.

An illumination light source 306 is provided near the exposure optical system, and illumination light 307u from this illumination light source 306 passes through a condenser lens 308 and is reflected at a predetermined angle by a half mirror 309. The chromatic aberration correction lens group 316 and the reflection lens 311f reach the reduction projection lens 303, and the reduction projection lens 303 illuminates a predetermined portion of the Eva 305.

In this embodiment, the illumination light source 306 is guided from the exposure light source lamp by a light guiding means such as an optical fiber 3068, and a bandpass filter 317 is placed on the optical path. Among the emission wavelengths of a certain mercury lamp, E-line (λ=5461 m) and D-line (λ=
589 n rn ) (7). The illumination light that has passed through the band-pass filter 317 is incident on the half mirror 309 as continuous spectrum light in the visible light range. The advantage of using such continuous spectrum light is that it prevents interference fringes caused by monochromatic light and improves detection accuracy.

Chromatic aberration correction lens group 316 from the above half mirror 309
Illumination light -°, irradiated onto the wafer 305 via the reflecting mirror 311 and the reduction projection lens 303
Irradiate the pheasant alignment pattern formed on top [7
After that, the reflected light travels backward along the optical path of the illumination light 307a and enters the TV left camera 56) 312.

The 'l'V camera 312 is connected to the signal cable 312 a'i
The alignment mark 305b is connected to the signal processing unit via the iTV camera 312, and the alignment mark 305b is connected to the signal processing unit through the iTV camera 312.
The configuration is such that the position of b is calculated.

In this case, as shown in FIG. 19, the illumination light source 306 is an optical fiber 306a (multipoint light source) that derives light of a desired wavelength from a light source such as a mercury lamp as illumination light 307.
and coaxially attached to the end of this optical fiber 306a,
It is composed of a cylindrical mirror 306b (reflecting means) whose inner periphery exhibits a burnt surface 306C consisting of a cylindrical surface or a conical surface. The structure is such that the light is reflected toward the optical axis at the inner periphery and then emitted to the outside.

The cylindrical mirror used here is applied to the illumination system of the exposure optical system.1. + An example is Japanese Patent Publication No. 1986-251858 by Shiba et al.
Published on January 8th, application number 6092302, filing date 19
May 1, 1985), which is hereby incorporated into the present application.

That is, as shown in FIG. 21, in the case of this embodiment, the illumination light 307 emitted from the optical fiber 306a
is reflected by the inner periphery of the cylindrical mirror 306b, so that
Reduction projection lens 303 Entrance pupil 3 at K (+38
It becomes a link-shaped light beam at the position of , and the semiconductor wafer 3
Non-cooler illumination is performed in which the target area of 05 is illuminated in a spot-like manner with incoherent illumination light 7 consisting of a bundle of non-parallel light rays.

The operation of this embodiment will be explained below.

First, by moving the X-Y stage, radiation is emitted from the optical fiber 306a of the illumination light source 306, and is emitted from the cylindrical mirror 306b and the condensing lens 308. Beam splitter 30
9. Relay lens 310. The illumination light 307 that enters the semiconductor wafer 305 through the reflecting mirror 311 and the reduction projection lens 303f is made to irradiate the alignment mark 305b formed at a predetermined portion of the semiconductor wafer 305.

At this time, in this embodiment, El-t, reduction projection lens 30
As shown in FIG. 22, at the position of the entrance pupil 303a of No. 3, a "virtual image" of the illumination light source 306 consisting of a cross-sectional image of the optical fiber 306a of the illumination light source 306 and a ring-shaped light flux surrounding this cross-sectional image is formed. The illumination light 307 that illuminates the alignment mark 305b on the surface of the semiconductor wafer 305 becomes a non-parallel beam bundle and has non-coherence.

Therefore, the illumination light 307 on the transparent photoresist film 305a deposited on the surface of the semiconductor wafer 305
The intensity of the interference fringes is reduced, and the alignment mark 30 formed with unevenness 7 on the surface of the semiconductor wafer 305
5b, the alignment mark 30
The reflected light 307a reflecting the shape of 5b is the TV right camera 1.
It will be incident on 2.

As a result, the detection signal A shown as a solid line in the diagram of FIG.
The shape of the alignment mark 305b is clearly reflected as shown in 1. A detection signal is obtained, and the position of the alignment mark 305b is accurately determined by finding the minimum point of the detection signal A corresponding to the step part (c) of the alignment mark 305b and calculating the midpoint. can be grasped.

Thereby, the alignment of the target portion of the semiconductor wafer 305 with respect to the original 304 can be performed with high precision based on the position of the alignment mark 305b, and the alignment accuracy can be improved.

On the other hand, the illumination light 307 is applied to the semiconductor wafer 3 as a parallel beam bundle.
In the case of conventional cooler illumination applied to the photoresist film 305a, strong interference fringes are generated in the photoresist film 305a.
The shape of the alignment mark 305b is reflected (an unclear detection signal C with two waveforms is detected. Therefore, the position of the alignment mark 305b is It is difficult to accurately grasp this, and it is inevitable that the alignment sheath layer of the semiconductor wafer 305 with respect to the original 304 deteriorates.

In this way, the alignment mark 305 is accurately grasped.
Based on the position of the semiconductor wafer 305, the target part of the semiconductor wafer 305 is accurately positioned on the optical axis of the exposure optical system, and then the exposure light source 301 emits light, and the condenser lens 302. Original version 304. By the exposure light that has passed through the reduction projection lens 303,
The integrated circuit pattern formed on the original plate 304 is transferred to the photoresist film 305a of the semi-integrated wafer 305.

(4) Explanation of the light source that can be used in the valley embodiments Figures 27 and 27 (b) are schematic wavelength distributions of reference light sources suitable for each embodiment of the present invention. Figure (a) shows Hg; 7-amp dichroic light (E&D lines 545 nm and 578 nm respectively), Figure (b) shows xe-clamp continuous light or "white light", e.g. visible light ranging from green to orange ( 56 onm
A continuous spectrum with a width of 10 Qnm centered at These can be appropriately selected as necessary.

On the other hand, the exposure light is G-line (
λ = 436 nm) K will be explained, but other light sources [7] Hg lamp 11 line (405 nm) and i
(365” ”) s and 308 nm of XeC1 or K r F (7) 248n by excimer laser
For m1'IK, each line of 1g2nm of A r l+'' can be applied.

(5) Description of alignment process, exposure, and manufacturing process common to each embodiment The following explanations are given using embodiment 3 as an example, but the explanations also apply to other examples (7). It is.

A specific semiconductor integrated circuit manufacturing process and the structure and operation of an exposure apparatus using the technology of the present invention will be described below.

FIG. 28 shows a projection lens barrel 303 (consisting of a group of ten or more lenses) and a pair of optical barrels 326a for black-pal alignment or pre-alignment.

Shows the interrelationship with b.

FIG. 29 shows the path of the chief ray of the exposure optical system in the Sudeching reduction projection exposure apparatus shown in FIG. As can be seen from this figure, the wafer, that is, the image side, is telecentric.

FIG. 35 shows the position t of a pre-alignment mark (for coarse positioning and θ orientation alignment) on a wafer, which is an object to be processed.

FIG. 36 shows the arrangement of alignment marks for chip alignment or fine alignment.

Figure 37 shows the scribe lines on the device surface of the wafer, that is, streets (X direction) and avenues (X direction).
direction).

FIG. 38 shows the shape of alignment marks on the scribe line used for fine alignment and clear alignment.

In the above figures 28 and 29 and figures 35 to 38,
303 is a 10:1 or 5:1 reduction projection path optical lens barrel, which consists of more than ten lenses (for monochromatic light such as G-line or 1-line), and covers an area of about 20 mm x 20 W on a wafer in one area.
Can be exposed in one shot. 326a and b are optical tubes for global alignment, die-pie-die, sight-pie-sight alignment, etc. (coarse alignment and θ azimuth alignment), and are positions that do not share the axis with the projection tube. It is set in. This clear alignment is performed using a visible white light source such as a Haloken lamp by removing the ultraviolet region with a filter so that the resist is not exposed to light.

301 is line light song and 1. 302 is a condenser lens, 303 is a projection lens group (projection lens barrel)
, 303a is an entrance pupil plane, and 303b is an example of a projection lens. 304 is reticle or Hamask, 305fd
Wafer, 305a+d resist film, 3211 An XY stage for stepping exposure is controlled by a laser interferometer.

328 indicates the chief ray passing through the center of the entrance pupil.

341a and 341b are pre-alignment marks on the device surface of a semiconductor wafer, and 342a-ja are also chip alignment marks.
These are registration marks for alignment (fine alignment), and they all have the same shape (6Φ, the details of which are shown in Figure 38.These marks are for every 12 one-shot surfaces) over the entire wafer. It is set up on the scribe line (343 is street, 344 is avenue), and 7 is selected from among them as appropriate.
used.

In the silk diagram 38, 344 is a scribe line (avenue) with a width of about 150 μm 1345 a and b are chip areas, 346 a and b are alignment pattern elements in the X direction with a width of 2 μm and a length of 50 μm 1347 a and b (dy direction alignment pattern) The element size is the same as above.348
a-d are other diagonal pattern elements.

In FIGS. 30 to 34, 305 is a wafer, 330 is an L
OCO8 oxide film, 331 is cate oxide film, 332FiP
8G film (first passivation or PSG-1),
333 is the first layer aluminum wiring (Al・■), 333
a is an aluminum wiring in the same layer as the above 333 forming the alignment mark opening 350, and the alignment mark opening 350 corresponds to the alignment pattern element 347a in FIG. 38, for example. 334 is an interlayer PSG film (PSG・■), 335 is a positive photoresist film, which is applied to the spinner by approximately 1
It was coated to a thickness of μm. 336 is PSG・
The opening in the resist film for opening a through hole in H and the through hole 337 are the second layer aluminum wiring (A[.■).

The exposure process will be explained below by taking as an example the drilling of the A1 interlayer through-hole contact hole in the 21mAA memory process. For details on the clobular alignment or buri alignment method, please refer to Nakazawa et al.
zawa) in Japanese Patent Publication No. 102823 (1981) (published on August 17, 1981).
Regarding the 2-layer A/process of DRAM, etc.
Japanese Patent Application No. 1986-235906 (
(Application filed on September 19, 1987), these documents constitute a part of the description of the present application.

1. First, a wafer with a resist film formed on the entire surface as shown in Fig. 30 is placed on the XY stage 327 (as shown in Fig. 29) so that the wafer orientation and flat plate are in a substantially constant position. .

Next, the global alignment optical system 3 in Figure 28
26a and b make a pair of alignment marks 3 as shown in Fig. 35.
By aligning the front tubes with 41a and 41b, the θ direction and the XY position are firstly aligned. This will be referred to as off-axis bridge alignment. (543,5n
(by the He-Nev-boo light of m) Following this, move the XY table and use the E-gan by the T'll'L method to
Each alignment mark 342a-j (8 to 10 are selected from a larger number of alignment marks) in FIG. 6 is sequentially detected. Each detection is performed at 346a (X direction), 347a (Y direction) shown in FIG.
direction) by looking in bright field. Stepping exposure is sequentially performed by moving the stage so that the misalignment of all chips is optimized based on the amount of misalignment of these multiple points. Exposure is performed as shown in FIG.

By this exposure, only the resist film in the contact hole portion is easily removed, and an opening 336 is formed, which is used to selectively etch the PSG-II, that is, 334, at a predetermined position on the PSG-II as shown in FIG. A through hole is formed in. Subsequently, the photoresist film 335 is completely removed, and a second layer aluminum film 337 is formed over the entire surface by sputtering on the PSG.

The structure of the illumination light source 306 is not limited to that shown in FIG. 19, but for example, as shown in FIG.
06d and 306e. In this case as well, the K'J song-shaped light beam is imaged on the entrance pupil of the reduction projection lens 303, and the illumination of the semiconductor wafer 305 by the illumination light 307 (is incoherent. This provides cooler illumination, and the same effect as in the case of the cylindrical mirror 306b described above can be obtained.

In this way, the following effects can be obtained in this embodiment.

(1) The illumination light source 306 is arranged around the optical axis of a multi-point light source such as an optical fiber 306a and the illumination light 307 emitted from this original fiber 306a, and the inner periphery is a bell surface 306C.
It consists of a cylinder @306b exhibiting
The illumination light 307 emitted after being reflected by b becomes a ring-shaped light beam at the entrance pupil position of the reduction projection lens 303, and irradiates the surface of the semiconductor wafer 305 as non-Kohler illumination with low coherence of non-parallel light beams. Therefore, the transparent photoresist film 305aK deposited on the surface of the semiconductor wafer 305 does not cause strong interference fringes.
Based on the reflected light 307a from the alignment mark 305b, a detection signal A that clearly reflects the shape of the alignment mark 307b can be obtained, making it possible to accurately grasp the position t of the alignment mark 305b.

Thereby, the alignment of the target portion of the semiconductor wafer 305 with respect to the original 304 can be performed with high precision based on the position of the alignment mark 305b, and the degree of alignment a can be improved.

(2) As a result of (1) above, it is possible to improve the overlay accuracy of the integrated circuit patterns formed by stacking them on the semiconductor wafer 305, and it is possible to improve the yield of semiconductor devices.

(3) As a result of the above (11, t21), productivity in the wafer processing step in manufacturing semiconductor devices can be improved.

The invention made by the present inventor has been specifically explained based on Examples (7). However, the present invention is not limited to the above-mentioned Examples, and it is understood that various changes can be made without departing from the gist of the invention. Needless to say.

For example, reflective flat films (2) are not limited to cylindrical mirrors, etc.
It may be of any shape such as a polygonal cylinder or a polygonal pyramidal cylinder.

Alternatively, the optical fiber of the illumination light source may be connected to the illumination light source, and a part of the exposure light may be used as the illumination light.

The above explanation mainly describes the case in which the invention made by the present inventor is applied to alignment technology in reduction projection exposure of semiconductor wafers, which is the field of application in which the invention was made by the present inventor (7), but is not limited to this. rather than something that
It can be widely applied to alignment techniques in general reduction projection exposure.

A brief explanation of the effects obtained by the examples is as follows.

That is, an alignment apparatus for reduction projection exposure, comprising a light source and a reflecting means disposed around the optical axis of illumination light emitted from the light source and reflecting the illumination light toward the optical axis side, Since the structure is such that the position of the alignment mark is detected by non-Kohler illumination, which irradiates the illumination light consisting of a non-parallel beam onto the alignment mark formed on the exposed object in a concave and convex manner, the position of the alignment mark is detected. If the illumination light irradiated onto the alignment mark is incoherent, for example, in a transparent photoresist layer formed to an uneven thickness on the surface of the exposed object, the shape of the alignment mark will not be reflected. , the occurrence of complex and strong interference fringes is avoided.

As a result, the detection signal based on the strength of the reflected light that reflects the shape of the alignment mark is not mixed with signals due to random interference fringes, and the position of the alignment mark can be clearly detected. It is possible to improve the alignment accuracy of the object to be exposed with respect to the original.

Margin below (6) Details of chromatic aberration correction system and high-order correction of chromatic aberration The following example is for g-line monochromatic exposure using an Hg lamp (NA of projection lens group 3 = 0.38), as in Example 1. , we will mainly explain the case where "white light" (continuous spectrum) as shown in Fig. 27(b) is used in the alignment optical system, but it can also be applied to other light sources and embodiments, so we will explain them here. Explanation will be omitted.

Furthermore, the exposure light is not limited to the g-line, but can also be applied to the h-line, i-line, and excimer laser light.

The stepper used here is 5=1 manufactured by GCA (USA).
It is based on the Steppa 6400DSW, and the projection lens 3 is a G-line projection lens model number 10-78-46 (NAO, 38) manufactured by Zeiss (West Germany). Generally, this type of lens system consists of several to several dozen lenses in order to eliminate various aberrations.

FIG. 39 is a sectional view in the Y direction (vertical) showing the overall layout of the chromatic aberration correction and astigmatism correction lens systems in the alignment optical system. In the figure, 618 is an end mirror for extracting alignment light off the axis of the projection lens 3 below the mask or reticle 4, and 602 is a through-the-lens (
605 is an imaging point; 605 is an imaging point;
603 and 607 are achromatic lens groups arranged almost symmetrically with respect to the image forming point, and 604 and 606 are a pair of cylindrical lenses (crown glass lenses) for astigmatism correction.
Similarly to the above, they are arranged almost symmetrically with respect to the imaging point 605. 615 is an achromatic relay lens (focal length 36+m), and 608 is an alignment light beam directed toward the beam splitter 12 (FIG. 1).

FIG. 40 is a cross-sectional view in the X direction (horizontal) of the correction lens group. In the figure, the thickness of the lens, the distance between the surfaces, and the radius of curvature of the spherical lens surface are shown in units (the following figures are similar). Here, the thickness of the lens refers to the distance between the centers of both end surfaces of the unit laminated lens (optical axis 609, that is, the intersection with the Z axis), and
The surface spacing is the distance between the centers of adjacent surfaces between adjacent lenses. A and C indicate the types of laminated achromatic lenses.

FIG. 41 is a sectional view in the Y direction as well.

FIG. 42 shows details of the A-tie single achromatic lens. In the same figure, 621 is a crown glass lens, 622
is a flint glass lens. Similarly, FIG. 43 shows details of a C-type achromatic lens, in which 623 is a flint glass lens and 624 is a crown glass lens. The glass material is manufactured by Schott.
) is 604.606.621. and 62
4 is crown glass (BK7), 622 and 6
23 is flint glass (SFII).

With this layout, the Hg lamp's D line and E#!
Most of the chromatic aberration in the XY plane disappears, but some lateral deviation in the XY plane remains unless fine adjustment is made. In order to remove these, the chromatic aberration correction lens groups 603 and 607 must be
It is sufficient to fix the color shift at a point where the color shift completely disappears by shifting them in mutually opposite directions in the XY plane in the direction of the remaining color shift.

44 to 46 show details of fine adjustment of the correction lens system.

In FIG. 44, 609R is the optical axis of the reference optical system that corresponds to 609 in the previous figure, and 605 is the optical axis of the first optical system.
The imaging points, 604 and 606, are a pair of astigmatism correcting lenses.

In FIGS. 45 and 46, 603 and 607 are
The chromatic aberration correcting lens groups 609A and 609B are rotational symmetry axes of the lenses of the chromatic aberration correcting lens groups 603 and 607, respectively.

Adjustment of the reference system is performed as follows. From the reference optical system in Fig. 39, the correction lens group 603°604.606,
Remove 607 and install achromat relay lens 61
5, and confirm the position of the entrance pupil of the projection lens 3 (FIG. 1) using only the E-ray.

Next, adjust the tip mirror 618 to make the light source fiber 13
(Fig. 1) so that the image of the end (effective light source point) is located at the center of the entrance pupil.

Next, the astigmatism correction lenses 604 and 606 are placed at the imaging point 60.
5, and adjust ΔZA as shown in FIG. 44 to minimize astigmatism.

Next, using the mixed light of the E line and the D line, ΔZ and ΔY are obtained in the state shown in FIG. 39 as shown in FIGS. 45 and 46.

ΔX is successively adjusted to minimize the focal position shift due to color and the image formation shift in the image height direction while looking at the pattern on the wafer.

Now, regarding the E and D lines of the Hg lamp, the so-called "
In the sense of ``achromat'', focal chromatic aberration and lateral chromatic aberration are removed. Note that spherical aberration is removed by appropriately designing the curvature of the lens surface of the correction lens group. Other aberrations are reduced to non-problematic values by arranging the correction lens group symmetrically with respect to the imaging point 605 and by designing other correction lenses, as described above.

(7) Explanation of documents for correcting the embodiments Regarding DRAM wafer process and device structure such as two-layer aluminum wiring, see Japanese Patent Application No. 62-235906 (1987) by Mu-rata et al. No. 246,514 (filed September 19, 2013), corresponding U.S. Patent Application No. 246,514 (No. 198
(Application filed on September 19, 1988) and its corresponding Korean application No. 11906/1988, which are hereby incorporated as part of the description of the present application.

Regarding the pressure compensation system for reduction magnification, please refer to Komoriya (Ko
Japanese Patent Application Publication No. 60-262421 (Japanese Patent Application No. 59-118315; June 1, 1984)
1 day filing) and its corresponding U.S. Pat. No. 4,699,505 (
Registered on October 13, 1987) and Shimiz
u) et al. (registered on May 19, 1987) and U.S. Patent No. 4,690,528 (registered on September 1, 1987) by Ta-nimoto et al. shall be made a part of the description of the present application.

For information on light sources for exposure, photoresists (positive type), alignment, and reduction projection exposure in general, please contact Ichi Hiroshi.
``Semiconductor phosphorography technology J'' edited by Ro Hoko)
19B6.5.30; published by Sangyo Tosho ■, pages 20 to 26 and pages 81 to 102, which are hereby incorporated as part of the description of the present application.

Furthermore, regarding the cylindrical inner mirror used as the illumination (alignment) light source, Shiba et al., Japanese Patent Publication No. 61-2
No. 51858 (published on November 8, 1986), this is hereby incorporated into the description of the present application.

Furthermore, I apologize for the inconvenience regarding the stepper alignment technology (
Japanese Patent Publication No. 10282/1982 by Nakazawa et al.
No. 3 (published August 17, 1981), this is hereby incorporated as part of the description of the present application.

Furthermore, Koehler illumination, aperture or entrance pupil, aberration correction,
Regarding filters and geometric optics in general, please refer to Hiroshi Kubota (H.
Iroshi Kubota), “Optics J1968
41-276, published by Iwanami Shoten on October 30, 2015, [Wave Optics J] published by Iwanami Shoten in 1971, 199-23 by the same author.
Page 6, Jenkins et al. [Fundamentals Op.
"Optics" published by McGraw-Hill Book Company CF, A. Jenkins & H.E., Whit
e, “Fundamentals of 0pti
Chapters 1 to 10 of “Principles Op Optics” by Horn et al., Pergamon Press 1983.
Published in (M., Born & E., Wolf, “P.
r1nciplesof 0ptics, Perg
amon Press) 133~255.418~4
28, pp. 522-526 and Klein, "Optics", published by John Wiley & Sons, 1970 (M, V.

Klein, “0ptics,” John Wil
ey & 5ons.

Inc., pages 106-118, which are hereby incorporated into the description of this application.

Furthermore, regarding optical materials such as lenses, Kubota (Kub.
ota) et al., "Optical Technology Handbook", 1987, 3
It is shown on pages 551 to 674, published by Asakura Shoten on May 1st, and is hereby incorporated as part of the description of the present application.

〔Effect of the invention〕

According to the present invention, H
T T L (Through
gh the Lens) method to extract light from a predetermined pattern on the wafer off-axis [7] During observation, the observation light extracted from below the reticle is passed through a chromatic aberration correction lens to produce polychromatic or continuous spectrum light. can be made available.

Furthermore, since the reference light is taken out off-axis before being reflected by or passing through a mask or reticle, it is not affected by various aberrations caused by a flat plate such as a mask.

Furthermore, since the reference light is taken out below the reticle,
There is enough room to insert the correction optical system, so in addition to chromatic aberration,
Spherical aberration, astigmatism, coma aberration.

A symmetrical arrangement is possible so that field curvature, distortion, etc. can be sufficiently removed.

In addition, since the projection optical system from the reticle to the wafer is spatially in a straight line, various aberrations (
) of the projection system can be removed.

Furthermore, since the principal optical axis of the projection system and the axis of gravity almost coincide,
It has a structure that is resistant to environmental influences, and it is easy to control changes over time.

In the above description of the present invention, the exposure light is monochromatic and the reference optical system is bright field. However, the present invention is not limited to this, and the present invention is not limited to this. Needless to say, the present invention can also be applied to reference optical systems that use dark field (diffraction or interference) exposure. Further, in this application, a projection system in which only the image side (wafer, etc.) is telecentric has been described, but the present invention is also applicable to a system in which the material (reticle, etc.) is also telecentric.

[Brief explanation of the drawing]

FIG. 1(a) is a perspective view of a reduction projection exposure apparatus according to an embodiment of the present invention, and FIG. 1(b) is a system diagram showing an optical system for pattern detection in embodiment 1. , Fig. 2(a) and (b) respectively show the chromatic aberration correction lens used in this embodiment 1;
) is a perspective view showing the astigmatism correction lens used in Example 1, and FIGS. 3(a) to 3(c) are explanatory diagrams conceptually showing the principle of correction by the chromatic aberration correction lens in Example 1. , FIGS. 4(a) and 4(b) are explanatory diagrams showing the relationship between the alignment mark formed on the wafer and the detected waveform in Example 1, and FIG. 5 shows the optical system for pattern detection in the prior art. Systematic diagrams FIGS. 6(a) and 6(b) are diagrams for explaining chromatic aberration. FIG. 7 is a perspective view of the main parts of a reduction projection exposure apparatus used in Embodiment 2 I of the present invention, FIG. 8 is a system diagram for explaining its optical system, and FIG. 9 (
a) to (d) are explanatory diagrams each showing the state of inclination of the optical axis due to the optical axis moving unit, FIGS. 10(a) and (b) are explanatory diagrams regarding chromatic aberration in the example, and FIG. 11(a) 12(a) to 14(f) to 14(a) to 14(f) show pattern detection in the above embodiment. An explanatory diagram showing the method, FIGS. 15(a) and 15(b) are flowcharts showing the signal processing procedure in pattern detection of the above embodiment, and FIG. 16 is a reduction projection exposure which is Embodiment 2 of the present invention. FIG. 17(a) is a partial system diagram showing the arrangement of illumination light sources in the device; FIG.
) and (c) are partial cross-sectional views and signal waveform diagrams obtained thereby for explaining the formation state of alignment patterns in the prior art. FIG. 18 is a perspective view showing the main parts of a reduction projection exposure apparatus equipped with an alignment device, which is Embodiment 3 of the present invention. FIG. 19 is an explanatory diagram showing the illumination light source section extracted. FIG. Fig. 21 is an explanatory drawing showing a modification of the light source, Fig. 21 is an explanatory drawing explaining the principle of non-Kohler illumination, Fig. 22 is a drawing showing a virtual image at the entrance pupil position of the reduction projection lens, Fig. 23 is an alignment mark. 24 is a diagram showing the change in interference intensity in the photoresist film in Koehler illumination and critical illumination. Figure 26 is a diagram of the principle of critical illumination. FIGS. 27(a) and (b) are schematic wavelength and light intensity distribution diagrams showing the wavelength configuration of the reference light used in the chip alignment of the present invention, and FIG.
Axis Global Alignment (Off-Axi)
Fig. 29 is a schematic ray tracing diagram showing the path of the chief ray in the exposure state of the present invention, and Figs. 35 is a cross-sectional flow diagram showing a part of the manufacturing process flow of the semiconductor integrated circuit device of the invention; FIG. 35 is a top view of a wafer showing the position of a pair of alignment patterns for global alignment of the invention; FIG. 37 is a schematic wafer top view showing the positions of the main alignment patterns for chip alignment of the present invention, FIG. 37 is a wafer top view showing the state of the scribe lines on the wafer of the present invention, and FIG. FIG. 2 is a top view of a wafer showing the shape and planar layout of alignment marks used for both global and chip alignment of the invention. FIG. 39 is a cross-sectional view in the -1" Y direction showing the overall layout of the chromatic aberration and astigmatism correction system (alignment optical system) of the present invention. FIGS. 40 and 41 are X and Y directions of the same correction lens system, respectively.
It is a directional cross-sectional view. FIGS. 42 and 43 are cross-sectional views showing detailed structures of same-color detented combination lenses (He type and C type), respectively. (
Since these are spherical lenses, any cross section including the optical axis is possible. 44 to 46 are schematic cross-sectional views showing fine adjustment of chromatic aberration and astigmatism. DESCRIPTION OF SYMBOLS 1... Exposure light source, 2... Condenser lens, 3... Reduction projection lens, 4... Reticle (original plate), 5... Wafer (exposure object), 6... Alignment mark, 7.
...Photoresist film, 8...Illumination light source, 10...
Bandpass filter, 11... Condenser lens, 1
2... Beam splitter, 13... Optical fiber, 1
4... Cylindrical mirror, 15... Relay lens, 16... Chromatic aberration correction lens, 16a... Concave lens, 16b...
Convex lens, 17... Astigmatism correction lens, 17a...
・Convex lens, 17b...Concave lens, 18...Reflector, 20...TV right camera 21...Lens, 22...
・Illumination light source (xen lamp), 71... wafer, 72
... Reduction projection lens, 73... Reticle (original version),
74...TV right camera recognition unit), 75...Mercury lamp (exposure light source, illumination light source), 76...Reflector, 77...
... Relay lens, 78... Beam splitter, 80.
...Band pass filter, 81... Condenser lens, 82... Photoresist film. Kura Tenmi Ward Kura Ward Imoutenha Tenho

Claims (1)

[Claims] 1. A photosensitive thin film formed on the first main surface of a semiconductor wafer, an integrated circuit wafer, or a plate-like object for manufacturing a semiconductor device or an integrated circuit device, having the following configuration: A projection exposure apparatus for performing reduction projection exposure of a pattern on the main surface of a reticle or mask by step-and-repeat and image-forming the pattern on the photosensitive thin film: (a) the reticle or Exposure light source means for supplying a short-wavelength monochromatic exposure light beam from the first main surface side of the mask; (b) directing the main surface of the reticle or mask to the first main surface of the wafer or plate-like object; Reticle or mask holding means for holding the reticle or mask so that they face each other and are parallel to each other; (c) A pattern on the main surface of the reticle or mask is formed by the exposure light on the first (d) a projection lens group whose image side is substantially telecentric, consisting of a large number of lens groups from which various aberrations have been removed for the exposure light in order to form a reduced image on the photosensitive film on the main surface by a refractive optical system; its first position on the main surface of the reticle or mask
The wafer or plate-shaped object is held so that the main surfaces of the wafer or plate-shaped object are substantially parallel and facing each other, and the single straight optical axis of the projection lens group, the center of the portion of the wafer or plate-shaped object to be exposed, and the reticle or mask for performing step-and-repeat exposure by relatively moving the wafer or plate-like object in a plane orthogonal to the exposure optical axis so that the centers of the projected portions of wafer or plate-shaped object holding means; (e) multi-color light having a longer wavelength than the exposure light from outside the optical axis of the projection lens group by a reflection means placed between the reticle or mask and the projection lens group; Alternatively, a reference light consisting of continuous light having a predetermined width is supplied to the first main surface of the wafer or plate-like object, and the reflected light is extracted out of the optical axis through substantially the same path as the wafer or plate-like object. (f) a bright-field epi-illumination and observation alignment optical system that horizontally aligns the wafer or plate-like object by observing a predetermined alignment pattern on the first main surface of the substrate; A correction lens group for correcting chromatic aberration of the projection lens group with respect to a reference light reflected from the first principal surface of the wafer or plate-shaped object, which is placed in an optical path in an optical system. 2. The correction lens group is a first lens in the alignment optical system.
2. The exposure apparatus according to claim 1, comprising a pair of substantially identical chromatic aberration correcting lens groups arranged substantially symmetrically with respect to the imaging point of . 3. The illumination angle of the entire illumination light beam of the alignment optical system to the first main surface of the wafer or plate-shaped object is set to 90°.
3. The exposure apparatus according to claim 2, wherein the exposure apparatus can be changed to a desired angle smaller than . 4. The exposure apparatus according to claim 3, wherein the correction lens group includes a pair of astigmatism correction lenses for correcting astigmatism. 5. The exposure apparatus according to claim 4, wherein the pair of astigmatism correction lenses are arranged at substantially symmetrical positions with respect to the first imaging point. 6. The exposure apparatus according to claim 5, wherein the reference light comprises a continuous spectrum having a predetermined width. 7. The exposure apparatus according to claim 6, wherein the continuous spectrum is included in the visible light range. 8. The exposure apparatus according to claim 7, wherein the light source of the reference light is a halogen lamp. 9. The exposure apparatus according to claim 5, wherein the reference light is light having a plurality of wavelengths. 10. The exposure apparatus according to claim 9, wherein the reference light is included in the range of visible light. 11. The exposure apparatus according to claim 10, wherein the light source of the reference light is a mercury lamp. 12. The epi-illumination system using the reference light is a Koler (Kol) system that forms an image of the effective light source on the entrance pupil of the projection lens group.
12. The exposure apparatus according to claim 11, which is er) illumination. 13. In the optical vicinity of the effective light source, the optical axis of the part of the reference light and its axis of rotational symmetry coincide so that the part of the reference light is imaged in a wider part on the entrance pupil. 13. The exposure apparatus according to claim 12, wherein the cylindrical inner mirror is arranged as shown in FIG. 14. When optically detecting a pattern on a semiconductor element formed in the shape of a step, the semiconductor element is irradiated with illumination at an angle of inclination to the vertical reference optical axis of the plane of the semiconductor element. In the above pattern detection method, the first coordinate value obtained by irradiating the step with the illumination irradiated at an angle of inclination with respect to the vertical reference optical axis of the plane of the semiconductor element, and the first coordinate value parallel to the vertical reference optical axis of the semiconductor element plane. A correction amount for the second coordinate value of the vertical illumination light is calculated by comparing it with the second coordinate value obtained by the irradiation of the vertical illumination light, and in subsequent pattern detection, A pattern detection method characterized in that a true coordinate value is calculated by adding the above correction amount to the calculated coordinate value. 15. When laminating a plurality of characteristic layers on the surface of a semiconductor wafer, a stepped pattern having first and second edges at both ends is formed around the vertical axis of the wafer plane, and When irradiating illumination light and recognizing the coordinate positions of both edges by the reflected light, the illumination light irradiated to the first edge and the illumination light irradiated to the second edge have different optical paths. A method for detecting patterns on a semiconductor device, characterized in that: 16. When sequentially stacking a plurality of characteristic layers on the surface of a semiconductor wafer using a mask, a step-like pattern with an asymmetric cross section having first and second edges at both ends centered on the vertical axis of the wafer plane is formed. When detecting the first edge position, the first edge is incident obliquely from the second edge direction.
When detecting the second edge position, the second illumination light incident obliquely from the first edge direction is used to detect the second edge position obtained by irradiation with the first illumination light. The center coordinates of both edges are calculated from the coordinates of the first edge position and the coordinates of the second edge position obtained by irradiation with the second illumination light, and the characteristic layer formed on this upper layer is formed at the center calculated above. A method for manufacturing a semiconductor device, characterized in that positioning with a mask is performed based on coordinates. 17. A method for manufacturing a semiconductor integrated circuit device having two or more Al wiring layers using the exposure apparatus according to claim 1. 18. Two or more layers of Al by the method of claim 16
A method for manufacturing a semiconductor device including a memory cell mat using a wiring layer.