JPS63181424A - Aligner - Google Patents

Abstract

PURPOSE:To simultaneously execute the exposure and the alignment with high accuracy by a method wherein a dichroic mirror and an objective for alignment use are constituted so that specific conditions can be satisfied. CONSTITUTION:A dichroic mirror is inclined in such a way that the lower light coming form an illumination optical system for exposure use is not blocked at least by an edge in the effective region of a reticle and that, at the same time, the laser light illuminates the edge in the effective region of the reticle according to a condition as expressed by Equation I. The optimum distance, for increasing the N.A., between the reticle and an objective for alignment use is decided according to Equation II; at the same time, this distance indicates the optimum range where the objective for alignment use can be aligned. Accordingly, the objective for alignment use and the dichroic mirror are installed in such a way that the Equations I and II are satisfied simultaneously; the exposure and the alignment are then executed simultaneously; as a result, the highly accurate alignment can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the configuration of an exposure apparatus that transfers a reticle pattern onto a substrate (wafer).

[Conventional technology]

In the gluing process during the manufacturing process of semiconductor devices, resist coating - alignment - is applied to one wafer.
The exposure-chemical process steps are repeated multiple times. In recent years, as the integration density of semiconductor devices has increased, the alignment and exposure steps during the above-mentioned process have become more and more important.
Reduction projection type exposure apparatuses have come into widespread use. This reduction projection type exposure apparatus requires a projection lens with particularly high resolving power, and the image of the pattern on the reticle is projected onto an evaporator placed on a moving stage by the high resolving power projection lens. Movement and exposure are repeated. At that time, quick alignment,
In addition to exposure and stage movement, high alignment accuracy commensurate with resolution is required.

In addition, in the reduction projection device, the alignment mark formed on the wafer through a chemical process after being projected through the projection lens is made to match the alignment mark on the reticle in the next process for each exposure.・Dial alignment is performed. In this case, it is desirable that the overlapping of the alignment marks between the reticle and the wafer performed via the projection optical system can be recognized at the same time as the printing exposure.

However, as shown in FIG. 4, the alignment optical system in the conventional exposure apparatus includes an alignment objective lens 6L16R that performs relative positioning between the reticle 3 and the wafer 5 through the projection lens 4, and reflection mirrors 2L and 2R.
and a condenser lens 1 of an exposure illumination optical system that transfers and exposes a pattern on a reticle 3 onto a wafer 5 via a projection lens 4. In order to observe the alignment mark provided therein and perform relative positioning with the wafer 5, a reflection mirror 2L,
2R is located at a protruding position that blocks part of the illumination light flux from the condenser lens I, and its reflection mirrors 2L, 2 during exposure.
It is configured so that R is retracted from its protruding position in the direction of the arrow in the figure.

[Problems to be solved]

However, in the conventionally known TTL alignment optical system that performs alignment via a projection lens, a part of the alignment optical system is placed in the exposure optical path, so during exposure, the alignment optical system The structure is complicated, leading to an increase in the size of the exposure apparatus, and there is a problem in that alignment cannot be performed during exposure. In order to transfer a finer pattern with even higher density onto a wafer, there is a problem in that alignment accuracy must be improved.

Therefore, it is an object of the present invention to solve the above-mentioned problems and to provide an exposure apparatus having a compact alignment optical system that can perform alignment at the same time as exposure with higher precision.

[Means for solving problems]

an exposure illumination optical system for transferring an image of a pattern on a reticle onto a substrate via a projection lens using first wavelength light; and a second wavelength light having a longer wavelength than the first wavelength light to transfer the image of the pattern on the reticle through the projection lens. an alignment optical system having an alignment objective lens for mutually aligning the substrate and the substrate; and an alignment optical system for separating the first wavelength light and the second wavelength light and guiding each wavelength light to the reticle. The basic configuration is a dichroic mirror that is installed obliquely with respect to the optical axis of the exposure illumination optical system and the optical axis of the alignment optical system.

In this configuration, the dichroic mirror and the alignment objective lens are configured to both satisfy the following conditions.

1-NA・σ 2 (1-NA・σ) (1-NA) 1-NA
・σ However, the effective area diameter H of the D reticle: the distance i from the part closest to the reticle in the effective head of the dichroic mirror to the reticle: the distance from the vertex of the alignment objective lens to the reticle NA: on the reticle side of the projection lens Aperture coefficient σ: Ratio of the numerical aperture of the exposure illumination optical system to the numerical aperture of the projection lens.

[Effect]

As shown in FIG. 1, the present invention is based on the structure of a projection exposure apparatus that can perform alignment at the same time as exposure, which was disclosed in a previous patent application (Japanese Patent Application No. 60-208396) by the same applicant as the present application. Here, the dichroic mirror 2 is arranged in the optical path between the objective lens 6 of the alignment optical system and the reticle 3, and also in the optical path with the condenser lens 1 of the exposure illumination optical system. A projection objective lens 4 for projecting a pattern on a wafer 3 and a wafer 5 are arranged. A light beam from an exposure light source (not shown) passes through a condenser lens 1, is reflected and turned by a dichroic mirror 2 by 45 degrees, uniformly illuminates a pattern on a reticle 3, and passes through a projection lens onto a wafer 5. Transfer the pattern to. On the other hand, the light flux that passes through the alignment objective lens 6 from the light source that supplies a light flux with a longer wavelength than the light source of the exposure illumination optical system is transmitted to the dichroic mirror 2.
Transparent. The alignment objective lens 6 is the reticle 3
It is movable parallel to the reticle 3 above the dichroic mirror 2 so that alignment can be performed over the entire range of the wafer 5 and the wafer 5. Then, the alignment mark on the reticle a and the image of the alignment mark on the wafer 5 are made to match, thereby performing relative positioning between the reticle and the wafer.

Since the first wavelength light, which is the exposure light beam, and the second wavelength light, which is the alignment light beam, have different wavelengths, alignment and printing can be performed at the same time.

In an exposure apparatus with such a configuration, in order to improve alignment accuracy, the NA must be increased.
In order to increase the NA, the alignment objective lens must be brought as close to the reticle as possible. Moreover, it is also an essential condition to maintain uniformity in illuminating the reticle via reflection from the dichroic mirror.

In order to satisfy the above conditions, the arrangement of the dichroic mirror and the alignment objective lens was determined as follows. As shown in FIG. 2, the lower ray A of the exposure illumination light from at least the horizontal direction can uniformly illuminate the reticle without vignetting at one end 3a of the reticle, and the lower ray A can also illuminate the end of the effective area of the reticle. Equation (1) indicates the minimum height at which a dichroic mirror must be installed obliquely so as to illuminate the area 3b.

H≧(D+HIA・σ 1−HA・σ However, as the H value increases, the area where the lower ray A of the exposure illumination light from the horizontal direction illuminates the dichroic mirror also increases, but the H value is relatively Since the value is small, only the principal ray of the exposure illumination light needs to be considered.

Next, equation (2) will be explained. 0 as shown in Figure 2
When considering this as a reference point, when increasing the NA to improve alignment accuracy, the alignment objective lens should be moved to a position where the optical axis of the alignment objective lens matches the optical axis of the projection lens from at least one end 3b of the reticle. That is, it must be arranged so that it can move in parallel to the reticle within a range that can cover up to half of the reticle and from one end 3b of the reticle to one end 3a of the reticle, that is, to cover the entire reticle.

H+D≧E≧H+−(D+φ) (2-1) Furthermore, the pantograph focus of the alignment objective lens can be expressed by equation (2-2).

φ J--, °, φ=2NA-β (2-2)2N^ Substituting equation (2-2) into equation (2-1), H+D≧i≧H
+ - (D + 2N^・l) Substituting equation (1) into equation (2-3) yields 2(1-NA・σ) (1-NA) 1-NA, and equation (2) can be obtained. .

Therefore, it is necessary to create a configuration that simultaneously satisfies equations (1) and (2). Here, equation (1) is a condition required by the optimal arrangement of the exposure illumination optical system, and equation (2) is a condition required by the optimal arrangement of the alignment optical system. Also, equations (1) and (2) are the NA of the projection lens.

The optimum arrangement of the exposure illumination optical system and the alignment optical system is defined based only on the illumination condition σ and the illumination area of the reticle.

That is, as shown in FIG. 2, the dichroic ink mirror 2 receives the lower light &9! from the exposure illumination optical system. This was obtained from the conditions that A must be installed obliquely so that at least the edge 3a of the effective area of the reticle 3 is not eclipsed, and the lower light MA illuminates the edge 3b of the effective area of the reticle. This is equation (1). Equation (2) indicates the optimum distance between the reticle and the alignment objective lens for increasing the NA, and at the same time indicates the optimum range in which the alignment objective lens can be aligned. Therefore, if the alignment objective lens 6 and the gicroic mirror 2 are provided so as to satisfy equations (1) and (2) at the same time, exposure and alignment can be performed at the same time, and even higher precision alignment is possible. An exposure device can be obtained.

If the upper limit of equation (1) is exceeded, the range to be aligned becomes larger, but the NA becomes equal to or greater than the conventional one, making it difficult to improve alignment accuracy. If the lower limit of equation (1) is exceeded, it is possible to increase the NA, but it becomes difficult to maintain alignment accuracy due to the physical constraint that the alignment range becomes smaller. If the lower limit of equation (2) is exceeded, it becomes impossible to uniformly illuminate the entire effective exposure area on the reticle with the light beam from the exposure illumination optical system.

By creating a configuration that satisfies each of the above conditions, alignment is possible even during exposure, improving throughput, maintaining uniformity of reticle illumination, and increasing the NA of the alignment objective lens. For the sake of
Furthermore, it can meet the demand for exposure equipment that can transfer fine patterns with high density onto wafers. Furthermore, since the alignment objective lens can be made more compact, it is expected that the alignment optical system and exposure apparatus will be made more compact.

〔Example〕

To explain the present invention according to the embodiment shown in the third diagram, a light beam from a light source that supplies first wavelength light (not shown) passes through a condenser lens 1 and is reflected and turned by a dichroic ink mirror 2 to uniformly form a pattern on a reticle a. The pattern on the reticle 3 is transferred onto the wafer 5 by the projection lens 4. On the other hand, a light beam from a light source that supplies light with a second wavelength longer than the light source of the exposure illumination optical system passes through the alignment objective lens 6 and passes through the guichroic mirror 5 to illuminate the alignment mark on the reticle 3. The illumination light beam that has illuminated the alignment mark passes through the center of the aperture 4a of the projection lens and epi-illuminates the wafer 5. The reflected light from the seven alignment marks on the epi-illuminated wafer 5 follows the opposite optical path and forms an image of the alignment mark on the reticle a. Therefore, the image of the alignment mark on the wafer is superimposed on the alignment mark 2 on the reticle 3. The superimposed images of the alignment mark on the reticle 3 and the alignment mark on the wafer 5 are transmitted through the guichroic mirror 2, enlarged and formed by an alignment objective lens, and sent to the final image via a relay system (not shown). image is formed on the light-receiving surface of the sensor of the TV image sensor. Then, relative positioning between the reticle 3 and the wafer 5 is performed using the image taken by the image sensor. In this way, since the distance between the alignment objective lens and the reticle can be shortened, the NA can be reduced, and even more precise alignment can be achieved.

〔Effect of the invention〕

As described above, the present invention makes it possible to carry out alignment at the same time as exposure by arranging the alignment objective lens and the gicroic mirror within the range of each of the above conditions, thereby contributing to an improvement in throughput. In addition, it is possible to reduce the distance between the reticle and the alignment objective lens while maintaining uniformity of reticle illumination, increasing the NA, allowing exposure to transfer even higher density and finer patterns onto the wafer. Can respond to equipment requirements. Furthermore, since the alignment objective lens can be made more compact than the conventional one, it is expected that the alignment optical system and the exposure apparatus as a whole can be made more compact.

In the embodiments of the present invention, a projection type exposure apparatus has been described, but it goes without saying that the present invention is applicable not only to an exposure apparatus using a projection optical system but also to an exposure apparatus using a proximity system or the like.

[Brief explanation of the drawing]

FIG. 1 is an optical sectional view showing an embodiment of the earlier application by the same applicant, FIG. 2 is a sectional view of an optical system showing the principle of the present invention,
FIG. 3 is a sectional view of an optical system showing an embodiment of the present invention, and FIG. 4 is a sectional view of an optical system showing a conventional technique. (Explanation of symbols of main parts) 1... Condenser lens, 2... Guicroic mirror, 3... Reticle, 4... Projection lens 1.
4a...Aperture, 5...Wafer, 6...Objective lens for alignment, Fig. 1

Claims (1)

[Scope of Claims] An exposure illumination optical system for transferring an image of a pattern on a reticle onto a substrate via a projection lens using first wavelength light, and second wavelength light having a longer wavelength than the first wavelength light. an alignment optical system having an alignment objective lens for mutually aligning the reticle and the substrate through a projection lens, and separating the first wavelength light and the second wavelength light; A dichroic mirror is provided obliquely with respect to the optical axis of the illumination optical system for exposure and the optical axis of the alignment optical system in order to guide the light to the reticle, and the dichroic mirror and the objective lens for alignment are configured as follows. An exposure apparatus characterized in that it is configured to satisfy both conditions. (1) H≧(D・NA・σ/1−NA・σ) (2) {D
(1+NA・σ)/2(1−NA・σ)(1−NA)}
≦l≦(D/1-NA・σ) However, D: Diameter of the effective area of the reticle H: Distance from the part of the effective area of the dichroic mirror closest to the reticle to the reticle l: From the vertex of the alignment objective lens to the reticle Distance NA: Aperture coefficient of the projection lens on the reticle side σ: Ratio of the numerical aperture of the exposure illumination optical system to the numerical aperture of the projection lens.