JPH02105002A - Detecting method for pattern on semiconductor element and manufacture of semiconductor device using said method and projecting and exposing device used therefor - Google Patents

Abstract

PURPOSE:To exactly detect the end edge coordinate and to enhance the matching accuracy by changing arbitrarily a lighting irradiation angle to a pattern step difference against a vertical reference optical axis of an element plane. CONSTITUTION:When an illuminating light irradiates by giving a prescribed inclination angle theta on a vertical reference optical axis of a pattern, a position of one of both end edges of the pattern can be detected exactly. Accordingly, when the irradiation is repeated by varying an inclination angle, even if a distortion is generated in the pattern and the cross section becomes an asymmetrical shape, the pattern position can be detected exactly, and the matching accuracy can be enhanced. Also, by comparing a first coordinate value obtained by varying the inclination angle and a second coordinate value obtained by an illuminating light being in parallel to the vertical reference optical axis, the correction quantity to a second coordinate value is operated, and at the time detecting the succeeding position, a matching processing is executed efficiently by correcting the data of only a vertical illuminating light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to alignment technology, and in particular to semiconductor wafers (hereinafter simply referred to as "wafers") for masks used in reduction projection exposure processes used in the manufacture of semiconductor devices. Concerning techniques that are effective when applied to alignment.

[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 pattern formed by uneven step shapes on the surface of the wafer, and the reflected light from the alignment pattern is made to enter the TV left camera via a half mirror or the like. By converting this reflected light into an electrical signal based on the amount of reflected light, the position of the alignment pattern is grasped, and the target exposure area of the wafer is positioned with respect to the mask. Such a positioning technique is generally called a through-the-lens (TTL) method.

Regarding projection exposure technology using the TTL method, Japanese Patent Application Laid-Open No. 177625/1988 by the applicant, and documents pointing out future issues with the TTL method include Nikkei McGraw-Hill Publishing, December 1, 1988, "Nikkei Micro Devices" P80-P81.

Here, the TTL type alignment technology will be explained in more detail using the system diagram shown in FIG. 11.

In FIG. 11, 101 is a wafer that is an object to be exposed, 102 is a reduction projection lens for exposure, which is placed directly above the wafer, 103 is a reticle as an original, and 104 is a TV left as part 1. The camera 105 is a mercury lamp as an exposure light source. A reflecting mirror 106, a relay lens 107, and a half mirror 108 are arranged on the optical path between the reduction projection lens 102 and the TV left camera 04, respectively, and the reflected light transmitted through the half mirror 108 is
The structure is such that the light is incident on the V left camera 04. on the other hand,
A bandpass filter 110 and a condenser lens 111 are respectively arranged between the mercury lamp 105 and the half mirror 108 to allow only E-ray (546 nm) to pass among the wavelengths from the mercury lamp 105.

The illumination light emitted from the mercury lamp 105 is irradiated onto the wafer 101 from the half mirror 108 via the relay lens 107, the reflecting mirror 106, and the reduction projection lens 102, and the reflected light from the wafer 101 travels backward along the optical path. and entered the TV left camera 04, and waveform detection was performed based on the recognized image of the TV left camera 04.

FIG. 12(a) shows the structure formed on the wafer 101,
FIG. 2 is a partial cross-sectional view schematically showing an alignment pattern 112.

The alignment pattern 112 is formed on the wafer 101 in synchronization with the wiring pattern, etc., and has a concave cross-sectional structure with edge-shaped edges on both sides of the inner circumference. The wafer plane on which such an alignment pattern 112 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 1 is formed on the wafer 101 in an ideal state without causing distortion.
12 is formed, the resulting waveform shows a peak value at the edge of the - pair, as shown in the same figure, and the coordinates of both peak values are Xa,
The center position 'fl ((X@+xL)/2) of the alignment pattern 112 was calculated from XL, and alignment was performed using this as the reference value X0.

[Problem to be solved by the invention]

However, when forming the Al of the alignment pattern 112, if the film thickness at the bottom of the step varies and the cross-sectional shape of the alignment pattern 112 becomes asymmetrical, the reflection angle of light will be disturbed and the waveform of the detected edge will be distorted. ,
In some cases, it was 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 technology that can accurately detect edge coordinates and improve alignment accuracy without being affected by distortion of alignment patterns. There is a particular thing.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve the problem]

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

That is, when optically detecting a pattern on a semiconductor element formed in the shape of a step, the illumination irradiation angle for the step is given at an inclination angle with respect to the vertical reference optical axis of the plane of the semiconductor element. be.

In addition, the first coordinate value obtained by irradiating the step with the illumination irradiation angle given an inclination angle with respect to the vertical reference optical axis of the semiconductor element plane, and the irradiation of vertical illumination light parallel to the vertical reference optical axis The correction amount for the second coordinate value of the vertical illumination light is calculated by comparing it with the second coordinate value obtained from the irradiation of the vertical illumination light. The true coordinate values are calculated by adding the correction amount.

[Effect]

According to the above-mentioned means, by applying illumination light at a predetermined inclination angle with respect to the vertical reference optical axis of the pattern, it is possible to accurately detect the position of one of the edges at both ends of the pattern. Become.

Therefore, by repeatedly irradiating the pattern with illumination light while changing the inclination angle in this way, even if the formed pattern is distorted, that is, the pattern is formed with an asymmetrical cross-sectional shape, it is possible to accurately position the pattern. Detection becomes possible and alignment accuracy can be improved.

In addition, by comparing the first coordinate value and the second coordinate value and calculating the correction amount, the amount of deviation due to detection with vertical illumination light becomes clear, so in subsequent position detection, vertical illumination light Efficient alignment processing can be performed by correcting the data obtained only from the above.

[Embodiment 1] FIG. 1 is a perspective view of the main parts of a reduction projection exposure apparatus used in an embodiment of the present invention, FIG. 2 is a system diagram for explaining its optical system, and FIG. ) and (c) are explanatory diagrams showing the tilted state of the optical axis by the optical axis moving unit, respectively, and FIG.
) and (b) are explanatory diagrams regarding chromatic aberration in the examples,
5(a) and 0)) are a partial cross-sectional view and a plan view thereof showing the state of formation of an alignment pattern on a wafer,
6 to 8 are explanatory diagrams showing the pattern detection method of this embodiment, and FIGS. 9(a) and 9) are flowcharts showing the signal processing procedure in pattern detection of this embodiment.

In FIG. 1, the reduction projection lens W1 includes an exposure optical system consisting of an exposure light source 2 made of a mercury lamp, a condenser lens 3 that focuses the exposure light emitted from the exposure light source 2, and a reduction projection lens 4. have.

Between the condensing lens 3 and the reduction projection lens 4, a reticle 5 (original plate) is removably arranged, which has an integrated circuit pattern formed on a transparent quartz glass substrate with a light shielding film such as chromium (Cr). There is.

On the other hand, in the figure, a wafer 7 (object to be exposed) whose position can be adjusted in the horizontal direction is mounted below the reduction projection lens 4 on the top surface of the XY stage 6. The wafer 7 has a predetermined alignment pattern 8 formed in a stepped shape as shown in FIG. 5, and a photoresist film 10 is further deposited on the upper surface of the wafer 7 by a spin coating technique. In FIG. 1, exposure light emitted from an exposure light source 2 and transmitted through a reticle 5 is reduced by a reduction projection lens 4 to a predetermined magnification (for example, 115) and projected onto a wafer 7. An integrated circuit pattern is transferred onto the photoresist film 10, and a chemical change occurs in the photoresist film 10 in the portion irradiated with exposure light, thereby forming a resist pattern of the photoresist film IO.

An illumination light source 11 is provided near the exposure optical system, and the illumination light from this illumination light source 11 passes through a condenser lens 12, an optical axis moving section 13, etc., and then passes through a half mirror 1.
4 at a predetermined angle, and is further reflected by a relay lens 15.
, a chromatic aberration correcting lens group 16 and a reflecting mirror 17 before reaching a reduction projection lens 4, which further illuminates a predetermined portion of the wafer 7.

In this embodiment, the illumination light source 11 is guided from the exposure light source 2 by a light guiding means such as an optical fiber 18, and a bandpass filter 20 is disposed on the optical path. Of the emission wavelengths of the mercury lamp, only E-line (λ=546 nm) and D-line (λ=589 nm) are transmitted. Bandpass filter 2 above
The illumination light that has passed through 0 is incident on the half mirror 14 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.

The illumination light irradiated onto the wafer 7 from the half mirror I4 via the chromatic aberration correction lens group 16, the reflecting mirror 17 and the reduction projection lens 4, after irradiating a predetermined alignment pattern 8 formed on the wafer 7, The reflected light is configured to travel backward along the optical path of the illumination light and enter the TV camera 21. Note that the optical path of this illumination light will be described in detail later.

The optical axis moving unit 13 includes a shutter 23 through which an illumination aperture hole 22 is formed, and a shutter support 25 that is slidable along a guide 24 together with the shutter 23. 25 is step motor 2
As shown in FIG. 3(a) right and FIG. 3(b), it is possible to make fine adjustments by ±l in the horizontal direction.

That is, when the shutter 23 is moved by a predetermined amount ±β in the horizontal direction due to the movement of the step motor 26, the illumination aperture hole 22 formed in the shutter 23 is also moved by ±l in the left-right direction in the figure. , the optical axis of the illumination light to the condenser lens 12 is tilted at a predetermined angle.

Due to the inclination of the optical axis, the reduction projection lens 4
The illumination light that is irradiated onto the alignment pattern 8 of the wafer 7 is also tilted at a predetermined angle. In this embodiment, the vertical reference optical axis, that is, the axis perpendicular to the plane of the shutter 23, is the center of the vertical reference optical axis.
By moving in steps, the illumination light can be incident on the alignment pattern 8 at an angle of ±θ.

Next, the chromatic aberration correction used in this example, the lens group 16
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. 4(a) and 4(b).

Note that a and b in the figure each indicate the distance from the lens 120 to the imaging position. Here, the above lens 1
If the focal length of 20 is f, then a.

As is generally known, the relational expression between b and f is as follows.

1/a+l/b=1/f...(1) At this time, if the focal length changes by Δf, the change Δb in the imaging position is Δb=(b2/f”)Δf...(2 ).On the other hand, as shown in FIG. 4(b), the relational expression between the focal length f and the refractive index n of the lens 120 is as follows.

f=R/(n-1) (3) In the above equation, R indicates the radial length of the spherical surface of the lens 120. From this equation, the change Δf in the focal length due to the change Δn in the refractive index is Δf=−RΔn/(n−1)”=−fΔn/(n−1) (4).

Substituting this equation (4) into the above equation (2), Δb=-b
” Δn/f (n-1) ...(5).Here, since the imaging magnification ¥-m is m = b / a, the above formula (5) becomes Δb = -f ( 1+m)2 Δn/(n-1)...
(6) becomes. 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 120 becomes longer, the imaging position also changes by Δb from the lens 120.
shift towards the direction of. This is chromatic aberration.

In general, the reduction projection lens 4 used in the reduction projection exposure apparatus 1 is designed to obtain optimal optical characteristics for G-line (λ = 436 nm), which is the exposure light, and therefore is used as illumination light. No consideration is given to the problem of chromatic aberration when using light of other wavelengths such as E-line or D-line.

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 2 of both wavelengths passes through the alignment optical system without performing chromatic aberration correction.
1, the difference in image formation position is on the order of several tens of millimeters.

The chromatic aberration correction lens group 16 of this embodiment has the above-mentioned chromatic aberration,
That is, it is used to correct a shift in the imaging position when continuous spectrum light is used as illumination light.

In other words, the chromatic aberration correcting lens group 16 of this embodiment has a function of maintaining the image formation position constant regardless of the magnitude of the incident wavelength, and 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 with a small incident wavelength, that is, a large refractive index.

The configuration of the chromatic aberration correction lens group 16 is as follows:
For example, it is a combination of a concave lens made of flint glass and a convex lens made of crown glass, and it is possible to correct chromatic aberration in a wavelength band including E-line and D-line of about λ=500 nm to 59 Q nm. The range in which chromatic aberration can be corrected can be easily adjusted by changing the distance between the lenses of the combination lens.

FIGS. 5(a) and 5(b) show in detail the cross-sectional structure and planar structure of the alignment pattern 8 formed on the wafer 7. FIG.

That is, on the upper part of a semiconductor substrate 31 made of a silicon (Si) semiconductor, there is a first pattern 31a formed by aluminum (Aj etching, etc.) in synchronization with the formation of a wiring pattern (not shown). The edge shape (L, R) of the pattern 31a is reflected on the upper layer to form the second and third
Patterns 31b and 31c are formed. The steps for forming each of the patterns 31a-c will be described in more detail below.

First, a first pattern 31a is formed on a semiconductor substrate 31 in synchronization with a process of forming a first layer wiring (not shown), and then a first insulating film 32a is formed through a photoresist process. This first insulating film 32a is initially formed to cover the entire surface of the alignment pattern 8, and then
The first pattern 31a is formed through the photoresist process again.
The first insulating film 32a on the upper surface is etched away.

As a result, the surface of the first pattern 31a is exposed. In this state, the second pattern 31,b is formed in synchronization with the second layer wiring (not shown). As described above, in this embodiment, the first pattern 31a and the second pattern 31b are directly stacked without intervening the first insulating film 32a, so the interposition of the insulating film may be the cause. Pattern distortion and the like are relatively prevented.

After forming the second pattern 31b, a second insulating film 32b is formed again by a photoresist process, and this second insulating film 32b is further partially etched away to expose the second pattern 31b. Ru. Thereafter, a third pattern is formed on this second pattern 31b in the same manner as above.

As described above, according to this embodiment, since the first to third patterns 31a to 31c are directly stacked without an intervening insulating film, the lower first and third patterns 31C also overlap. The structure has relatively undistorted edges that reflect the shapes of patterns 31a and 31t of No. 2.

Next, an alignment procedure using alignment pattern 8 (third pattern) formed as described above will be explained. Although the alignment pattern 8 shown in FIGS. 6 to 8 is shown in a simplified manner for convenience of illustration, it has a cross-sectional structure that is almost the same as that shown in FIG. 5 above.

FIG. 6 shows a case where the alignment pattern 8 is formed in a symmetrical shape, that is, without distortion, and FIG. This is caused by unevenness in the film thickness of the first and second patterns 31b in the figure, and FIG. 6 shows a case where the edge portion of the alignment pattern 8 is chipped.

As shown in FIG. 6, when the alignment pattern 8 is formed in an ideal state with a substantially symmetrical shape, the alignment method in the prior art, that is, only the straight light from the vertical direction (vertical illumination light S) is sufficient. Alignment accuracy can be obtained.

However, in the actual manufacturing process of the wafer 7, it is difficult to always form the alignment pattern 8 with a symmetrical shape as described above, and the alignment pattern 8 with an asymmetric cross-section as shown in FIGS. 7 and 8 is difficult to form. This is often the case.

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. 6, and then a case where the alignment pattern 8 is formed in an asymmetrical shape as shown in FIGS. 7 and 8 TIA will be described.

First, by moving the XY stage 6, illumination light is emitted from the illumination light source 11 and reaches the shutter 23 via the condenser lens 12.

Here, the shutter 23 together with the shutter support section 25 is
The illumination diaphragm 2 is moved in the -1 direction by the operation of the step motor 26 (Fig. 3, etc.).
The illumination light that has passed through step 2 advances to the subsequent alignment optical system in a state where it is tilted by 10 with respect to the vertical reference optical axis.

The illumination light further passes through a relay lens 15 and a chromatic aberration correction lens group 16. At this stage, the illumination light whose chromatic aberration due to the continuous spectrum light has been corrected is further reflected by a reflected film.
! 17, the alignment pattern 8 is irradiated through the reduction projection lens 4.

At this time, the illumination light (R detection light) is irradiated onto the alignment pattern 8 while being deviated from the vertical reference optical axis due to the movement of the shutter 23 on the optical path. FIG. 6(a) shows this state. According to the figure, the R detection light is irradiated from diagonally above at an inclination angle of −0 with respect to the vertical reference optical axis in the alignment pattern 8 .

As described above, the reflected light from the alignment pattern 8 irradiated with the R detection light travels in the opposite direction along the optical path of the R detection light and enters the TV left camera 1. The photoelectrically converted waveform signal is as shown in FIG. 3(b).

In the same figure, the part where the signal waveform has a valley shape is the edge position of the alignment pattern 8, and by reading this coordinate, the L canvas (XL) of the alignment pattern 8 can be determined.
) and R side (X side) edge positions can be recognized.

Here, as is clear from the figure, the R detection light having such an inclination angle -〇 has a shape portion formed by the left edge L of the alignment pattern 8 shown in figure (a). , which affects the waveform signal, making it impossible to accurately detect the left (L) edge position X. However, the edge detection waveform on the right (R)
Since no noise components such as the shape of the illumination are included, the R edge position X is accurately detected. Therefore, when the edge position is detected using the R detection light, only the edge position data xl on the R side is employed, and the position data XL containing the noise component on the L side is not used.

Next, when the step motor 26 is further operated and the shutter 23 is at the +1 position (FIG. 3 (6)), illumination light 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 8. As shown in FIG. 6(e), the illumination light at this time is L detection light that is tilted by 10 degrees from the reference axis in the alignment pattern 8.

Figure (f) shows the detected waveform at this time, and R
Detection of the edge position Detected accurately and reliably.

At this time, if the edge position data obtained by the detection light is only for the L side (XL), the R side position data X11 containing noise components is not adopted.

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

It should be noted that although the explanation has been repeated, when the shutter 23 is at the +0 position due to the operation of the step motor 26, that is, when the illumination aperture hole is located on the vertical reference optical axis, the illumination light is vertical illumination light. S is the same as that of the prior art. Such vertical illumination light S is shown in FIG. 6(a).
, (C) and (e), as long as the alignment pattern 8 is in an ideal state, that is, the cross-sectional shape is symmetrical and formed with high precision, only the irradiation with this vertical illumination light S is required to form the R side and L side. Etsuji rank of both sides! t (XL
, Xa) both allow accurate position detection.

However, if the cross-sectional shape of the alignment pattern 8 is asymmetrical, noise components are included in the reflected light due to the influence of diffused reflection, etc., so accurate position detection may be difficult depending on the detection signal waveform from the TV camera 21. many.

Next, a case will be described in which the cross-sectional shape of the alignment pattern 8 is asymmetrical, that is, a case in which the alignment technique of this embodiment is most effective.

As shown in FIG.
In the vertical illumination light S as shown in Figure (C), the edge detection waveform on the R side includes noise, as shown in Figure (A).

Regarding this point, in this embodiment, by using the R detection light described above, it is possible to accurately detect the R edge position (X,) as shown in FIG. However, with the conventional vertical illumination light S, as shown in FIG. 7(C), when detecting the edge on the R side, reflected light due to the inclination of the bottom surface is added as a noise component, making it difficult to accurately detect the R edge position. It has become difficult ((6) in the same figure).

However, when detecting the edge on the L side,
) and (f), by using the detection light having an inclination angle of +θ, it is possible to accurately detect the edge on the L side. Similarly, when detecting edges on the R side, as shown in Figures (a) and (C), by using the R detection light having an inclination angle of -0, accurate edge detection on the R side becomes possible. ing.

By the way, the causes of the noise component when only the vertical illumination light S is used include the case where the bottom surface of the step is inclined as shown in FIG. In some cases, sagging 33 may occur.

That is, as shown in FIG. 8(C), the vertical illumination light S is applied to the alignment pattern 8 causing the blurring surface 33.
, the diffused reflection from the blurred surface 33 causes noise in the detection waveform of the edge on the L side where the blurred surface 33 is located, as shown in (6) in the same figure, making it difficult to detect the accurate edge position on the L side. It becomes.

Even in such a case, according to this embodiment, the R edge position X can be accurately detected by using the R detection light shown in FIG. Accurate detection of edge position X becomes possible. Therefore, the R edge position data Xi obtained by the R detection light
and the edge position data xL obtained by the L detection light
By using this, it is possible to accurately detect both the R side and L side edge positions without being affected by diffused reflection from the blurring surface 33.

The edge detection described above will be explained at the level of signal processing using the flow diagram of FIG. 9(a) as follows.

First, the R edge position is detected by the R detection light, and the coordinates of this detection position are set to X (Step 9 in FIG. 9(a)
01). Note that the edge position data at this time is not employed.

Next, the L edge position is detected using the L detection light, and the coordinates of this detected position are set to X (step 902). At this time as well, R edge position data is not employed.

The average coordinate between X and XL obtained in this way is calculated, and this is set as the pattern reference position coordinate Xo (step 903).

Next, the R detection light, vertical illumination light S and L described above are
By using the detection light, the alignment pattern 8
The case of detecting asymmetry will be explained.

First, after determining Xo by the signal processing shown in FIG. 9(a) above (step 904), the vertical illumination light S shown in each (C) of FIGS. 6 to 7 is applied to the alignment pattern 8. , and the R detection position coordinates (2
m) and the L detection position coordinate (ZL), the average value of these Z. is calculated (905). Of course, each coordinate Z1 obtained at this time. Since either ZL (R edge position data or L edge position data) contains a noise component as explained above, Zo obtained thereby is also not a true value.

Next, Xa obtained in step 903 from Z0 above
ΔZ is calculated by subtracting ΔZ (906).

This ΔZ is Z with respect to the true pattern reference position coordinate xO0
The amount of deviation of o will be calculated. Therefore, in the subsequent alignment process, by adding the correction amount ΔZ to Zo obtained from the vertical illumination light S,
True pattern reference position coordinates X without using R detection light and L detection light. can be obtained.

In this way, in this embodiment, after determining the pattern reference position coordinate X0 using the R detection light and the L detection light,
In the subsequent alignment work, accurate pattern position recognition for each alignment pattern 8 becomes possible by simply performing arithmetic processing of adding the correction amount ΔZ to the value detected by the vertical illumination light S.

[Embodiment 2] FIG. 1O is a partial system diagram showing the arrangement of illumination light sources in a reduction projection exposure apparatus which is another embodiment of the present invention.

In the present Example 2, the illumination light sources are arranged in two places without providing the optical axis moving part explained in the above Example 1.
I'm trying to get the same effect.

That is, the first illumination light source 41a is arranged so as to be incident on the alignment pattern 8 as the detection light R at an angle of 10 with respect to the vertical reference optical axis, and the illumination light source 41b of the second method is arranged at an angle of 100 with respect to the vertical reference optical axis. It is arranged so that it is incident on the alignment pattern 8 as a detection light at an angle of 10 with respect to the reference optical axis.

Such first and second illumination light sources 41a.

As 41b, the optical fiber 18 is used as in the first embodiment.
The light may be guided from the exposure light source 2, or an independent light source may be provided.

In this way, in this embodiment, the first illumination light source 41a
By switching the illumination between the second illumination light source 41b and the second illumination light source 41b, it is possible to obtain the same R detection light and L detection light as in the first embodiment, making it possible to accurately detect the edge position.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, in the embodiment, a case has been described in which light from a mercury lamp, which is the exposure light source 2, is guided as the illumination light source 11 through the optical fiber 18 or the like, but the illumination light #! An independent xenon lamp or the like may be used as the lamp 11. By using a xenon lamp that emits relatively uniform light energy at each wavelength, it is possible to selectively employ continuous spectrum light, allowing for more accurate pattern detection without interference fringes. .

The above explanation has mainly been about 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.
The present invention is not limited to this, and can also be applied to, for example, an alignment technique between a photomask and a wafer in 1:1 equal-magnification exposure.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

That is, by irradiating the illumination light at a predetermined inclination angle with respect to the vertical reference optical axis 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 formed pattern is distorted by repeatedly irradiating the pattern with illumination light while changing the inclination angle,
That is, accurate position detection is possible even in a pattern formed with an asymmetric cross-sectional shape, and alignment accuracy can be improved.

In addition, by calculating the correction amount by comparing the first coordinate value obtained by irradiating the detection light from the oblique direction with the second coordinate value obtained from the vertical illumination light, Since the amount of deviation detected by the detection becomes clear, efficient alignment processing can be performed in subsequent position detection by correcting data obtained only from the vertical illumination light.

[Brief explanation of drawings]

Fig. 1 is a perspective view of the main parts of a reduction projection exposure apparatus used in an embodiment of the present invention, Fig. 2 is a system diagram for explaining its optical system, and Fig. 3 (
a) to (6) are explanatory diagrams each showing the state of inclination of the optical axis by the optical axis moving unit, FIGS. 4(a) and (b) are explanatory diagrams regarding chromatic aberration in the example, and FIG. 5(a) and (b) is a partial cross-sectional view and a plan view showing the formation state of the alignment pattern on the wafer.
Figures (a) to (f) to Figure 8 (a) to (f) are explanatory diagrams showing the pattern detection method of the above embodiment, and Figures 9 (a) and (5) are diagrams showing the pattern detection method of the above embodiment. FIG. 10 is a flow diagram showing the signal processing procedure, and FIG. 10 is a partial system diagram showing the arrangement of illumination light sources in a reduction projection exposure apparatus that is another embodiment of the present invention. FIG. FIGS. 12(a) and 12(a), 12(a), 12(a) and 12(a) are partial sectional views for explaining the formation state of alignment patterns in the prior art, and signal waveform diagrams obtained thereby. 1... Reduction projection exposure device, 2... Exposure light source, 3...
・Condensing lens, 4... Reduction projection lens, 5... Reticle, 6... XY stage, 7... Wafer, 8...
- Alignment pattern, lO... Photoresist film, 11... Illumination light source, 12... Condenser lens,
13... Optical axis moving unit, 14... Half mirror 115
...Relay lens, 16...Chromatic aberration correction lens group,
17...Reflector, 18...Optical fiber, 20...
Bandpass filter, 21...TV camera, 22...
- Illumination aperture hole, 23... Shutter, 24... Guide, 25... Shutter support part, 26... Step motor, 31... Semiconductor substrate, 31a... First pattern, 31b. ... second pattern, 31C... third pattern, 32a... first insulating film, 32b... second insulating film, 33... sag, 41a... first illumination Light source, 41b... Second illumination light source, 101... Wafer, 102... Reduction projection lens, 103... Reticle (original plate), 104... TV camera (recognition unit), 10
5...Mercury lamp (illumination light source), 106...Reflector, 107...Relay lens, 108...Half mirror 1110...Band pass filter, 111...Condenser lens, 112... alignment pattern,
120...lens. Agent Patent Attorney Daiwa Tsutsui Figure 2 R detection light L detection light 3 Figure 5 Figure 6 R detection light Figure 7 R detection light Vertical illumination light S Figure 8 R detection light X 9th (a) Figure (b)

Claims (1)

[Claims] 1. When optically detecting a pattern on a semiconductor element formed in the shape of a step, the illumination irradiation angle for the step is set at an inclination angle with respect to the vertical reference optical axis of the plane of the semiconductor element. A method for detecting a pattern on a semiconductor device, characterized in that irradiation is performed in an arbitrary manner. 2. The first coordinate value obtained by irradiating the step with the illumination irradiation angle given an inclination angle with respect to the vertical reference optical axis of the semiconductor element plane, and the irradiation of vertical illumination light parallel to the vertical reference optical axis. The correction amount for the second coordinate value of the vertical illumination light is calculated by comparing it with the second coordinate value obtained from the irradiation of the vertical illumination light. 2. The pattern detection method according to claim 1, wherein the true coordinate values are calculated by adding a correction amount. 3. When forming 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 angle of the illumination light irradiated to the first edge and the illumination light irradiated to the second edge are different. A method for detecting patterns on a semiconductor device, characterized in that: 4. 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 illumination light incident obliquely from the second edge direction is used, and when the second edge position is detected, the first illumination light is used.
The coordinates of the first edge position obtained by irradiation with the first illumination light and the coordinates of the first edge position obtained by irradiation with the second illumination light are The center coordinates of both edges are calculated from the coordinates of the edge position in step 2, and the characteristic layer formed on the upper layer is positioned with respect to the mask based on the calculated center coordinates. Production method. 5. A projection exposure apparatus that irradiates illumination light onto a stepped pattern formed on a semiconductor wafer in an exposure process and uses the reflected light to position the pattern with a mask,
A projection exposure apparatus comprising an optical path control means capable of irradiating illumination light onto a semiconductor wafer from different irradiation angles. 6. The optical path control means is an illumination diaphragm that is provided so as to block the reference optical axis from the illumination light source, has an aperture hole in its main surface, and is movable in a direction orthogonal to the reference optical axis. 6. A projection exposure apparatus according to claim 5. 7. The projection exposure apparatus according to claim 5, wherein the irradiation light source for the illumination light is a light source dedicated to pattern detection independent of the exposure light source.