JPH0193120A - Reduced projection-exposure device - Google Patents

Abstract

PURPOSE:To conduct a reduced projection-exposure operation with which a pattern can be transferred in a highly precise manner by a method wherein the local inclination of the surface of a wafer is accurately detected without narrowing the width of a laser beam narrower than the width of a scribe line. CONSTITUTION:After a wafer 6 has been moved to the prescribed position by an ordinary positioning mechanism, the inclination of the exposing region such as the wafer surface of one-chip component is detected by a detecting part 8. Then, at least either of a reticle 4 and a wafer stage is inclined so that the above-mentioned inclination can be corrected. In this case, when the wafer stage only is inclined, the wafer stage is inclined by a stage fine adjust ment part 7 in the amount same as the detected inclination. Also, when the reticle only is inclined, the reticle 4 is inclined five times of the wafer surface detected by the reticle fine adjusting part 5 in the case of 1/5 contraction, for example. Accordingly, a transfer operation can be conducted on the wafer surface in a highly precise manner by performing the correction of inclination on the exposing region in advance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a reduction projection exposure apparatus that performs reduction exposure of a reticle image onto a semiconductor wafer in the process of manufacturing a semiconductor device.

(Prior Art) In this type of conventional reduction projection exposure apparatus, the inclination of the reticle surface and the stage for growing the wafer with respect to the main axis of the optical system is fixed during the period when at least one semiconductor wafer is exposed. It had been.

By the way, the wafer surface is locally uneven, and at present, one must be prepared for a height difference of 3 μm within a 10 mm square area. Furthermore, in consideration of field curvature and unevenness of the element surface when the wafer is in the middle of the process, the focus margin of the optical system is required to be 4 μm or more.

However, if the resolution is further increased in the future, the focus margin will decrease and it will no longer be possible to obtain a sufficient focus margin. For example, if an attempt is made to resolve 0.8 μm using a lens with an NA (numerical aperture) of 0.4, the focus margin will be 3 μm or less. In this case, there is a problem in that the current flatness of the wafer surface significantly reduces the accuracy of pattern transfer. Therefore, conventionally it has been difficult to increase the resolution.

In order to solve this problem, Japanese Patent Application No. 61-315367 discloses that a laser beam is irradiated onto the scribe line of the wafer, and the local tilt of the wafer surface is detected from the angle of the reflected light. Techniques are described for controlling the tilt of a wafer stage or reticle based on the results. In this way, even if an optical system with a narrow focus margin is used, highly accurate pattern transfer can be performed, and resolution can be improved.

However, in the tilt detection described in the above specification, in order to accurately detect the local tilt of the wafer surface, it is necessary to accurately irradiate a narrow aperture scribe line with laser light. This is because if the laser beam is projected onto the wafer surface without focusing, and if the wafer chip surface is uneven during the manufacturing process, a large amount of scattered light will be generated in addition to the reflected light. This is because the accuracy of detecting the inclination decreases. Therefore, in order to accurately detect the local tilt of the wafer surface, a very high-precision optical system is required, which leads to an increase in costs.

(Problems to be Solved by the Invention) This invention was made in view of the above-mentioned circumstances, and it is possible to eliminate the need to accurately project a laser beam only within the scribe line as in the past. It is an object of the present invention to provide a reduction projection exposure apparatus which is capable of accurately detecting the local inclination of a wafer surface without being affected by scattered light, is inexpensive, and has high precision in pattern transfer.

[Structure of the Invention] (Means for Solving the Problems) In the reduction projection exposure apparatus according to the present invention, a laser beam is irradiated onto a diffraction pattern formed in an exposure area on a semiconductor wafer surface, and the angle of the diffracted light is a wafer surface local tilt detection section that detects the tilt of the exposure area with respect to the main axis of the optical system; It is equipped with a fine movement part that tilts against the other hand.

(Function) In the reduction projection exposure apparatus having the above configuration, since the inclination of the exposure area is detected based on the angle of the diffracted light generated from the diffraction pattern, even if the chip body is irradiated with laser light, the chip surface The tilt can be detected without being affected by scattered light caused by the unevenness of the surface. Therefore, there is no need to narrow down the laser beam, the configuration of the optical system for detecting inclination can be simplified, and an inexpensive reduction projection exposure apparatus with high precision in pattern transfer can be obtained.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows, for example, an apparatus for performing a 5:1 reduction projection, where ■ is a light source system, 2 is a projection lens system, 3 is the main axis of the optical system, 4 is a reticle, and 5 supports the reticle and supports the A reticle fine movement part for finely adjusting the inclination with respect to the main axis 3; 6 a semiconductor wafer; 7 a stage fine movement part for finely adjusting the inclination of the wafer stage on which the wafer B is placed with respect to the main axis 3; 8 a local part of the wafer surface. This is a local area detection unit for one surface of the wafer for detecting the tilt (with respect to the main axis 3).

The wafer surface local tilt detection unit 8 is configured to irradiate a laser beam onto a diffraction pattern formed by unevenness formed in advance on an exposure area of the wafer surface, and to detect the local tilt of the wafer surface from the angle of the diffracted light. ing.

Next, with reference to FIG. 2, the principle of detection of the tilt detecting section 8 using diffracted light will be explained.

First, a laser beam 10 is irradiated onto the diffraction pattern 11 on the wafer from directly above the wafer 6 placed on the stage fine movement section 7.
Diffracted light 12.13 is generated. And its diffraction angle θ
Detects the local tilt of the wafer surface.

If the local tilt angle of the wafer surface is α, then the relationship between the tilt angle α and the diffraction angle θ is −S in (a) + S in (θ−a)−n
The relationship λ/d holds true.

Here, the tilt angle α and the diffraction angle θ are each in radian units, λ is the wavelength of the laser beam, d is the pitch of the diffraction pattern, and n is the order of diffraction.

Considering that the tilt angle α is small, the above formula % formula % (
)) It can be approximated as follows, and the inclination angle α is obtained as 5in(θ) −(n λ/d).

FIG. 3 shows an example of a diffraction pattern due to unevenness formed on the scribe line 11 of the wafer 6.

FIG. 3(A) shows a strip pattern arranged with a pitch of 2 μm and a width of 1 μm and an interval of 1 μm. In this case, for example, if a laser beam with a wavelength of λ-1 μm is used, the diffraction angle θ is about 30″.
becomes. Since this diffraction pattern has a very narrow pitch, a pattern similar to this is rarely formed within the chip body, so accurate tilt detection can be performed without narrowing down the laser beam as in the past. However, in some cases, similar patterns may be formed within the chip body, so in order to further improve the reliability of tilt detection, it is necessary to create an area around the chip that prohibits the formation of similar patterns, or It is better to narrow down the laser beam to approximately the width of the scribe line to prevent diffracted light from being generated from similar patterns formed within the main body.

Figure 3 (B) shows the band-shaped diffraction pattern at scribe line 11.
This angle β is tilted by an angle β with respect to the length direction of the body, and this angle β is an angle that is rarely used in the internal pattern (for example, 45″) or an angle that is not used (for example, 25°, 7
5°), there is no need to narrow down the laser beam and tilt detection can be performed more easily. If it is difficult to form a diffraction pattern at such an angle on the scribe line, the angle may be approximated by a step-like pattern as shown in FIG. 3(C).

Figure 3 (D) shows a diffraction pattern formed in the form of a dot matrix, and in this way, diffracted light is generated in both the X and Y directions of the wafer surface. Tilts in the X direction and Y direction can be detected simultaneously.

To detect the diffracted light generated from such a diffraction pattern, an optical sensor made of, for example, two-dimensionally arranged CODs can be used. In addition, when using the diffraction pattern shown in Figure 3(D), detection can be achieved by installing one-dimensional sensors in the X direction and Y direction, without using such a two-dimensional optical sensor. can be done.

Note that the diffraction pattern shown in Figure 3 does not necessarily have to be formed on the scribe line, and may be formed on a part of the chip body, but in this case, the area for the regular circuit formed inside the chip is limited. You need to be careful about limiting it.

In this way, the tilt detection section 8 in the reduction projection exposure apparatus of the present invention detects the tilt using the diffracted light generated from the diffraction pattern due to the unevenness, so that it is not affected by the scattered light due to the unevenness on the surface of the chip body. Therefore, accurate tilt detection can be performed without narrowing down the laser beam.

Further, the reticle fine movement section 5 is configured to support a support base that supports the reticle 4 by a piezoelectric element, and to apply a control voltage given by the wafer surface local tilt detection section 8 to this piezoelectric element. . Similarly, the stage fine movement section 7 is configured to support the stage support base with a piezoelectric element and apply a control voltage given by the detection section 8 to this piezoelectric element.

Next, the usage and operation of the reduction projection exposure apparatus configured as described above will be explained. First, the normal alignment mechanism (
After the wafer 6 is moved to a predetermined position by a wafer (not shown), a tilt detector 8 detects the tilt of the wafer surface for an exposure area, for example, one chip. Next, at least one of the reticle 4 and the wafer stage is tilted so as to correct the tilt detected in this manner. That is, when only the wafer stage is to be tilted, the wafer stage is tilted by the stage fine movement section 7 by the same amount as the detected tilt. On the other hand, when only the reticle 4 is tilted, this example performs 115 reduction projections, which is 5 times the detected wafer surface inclination (10 times in the case of 1/10 reduction projection). It is necessary to tilt the reticle 4 by the reticle fine movement section 5 by the amount shown in FIG. Incidentally, the tilt may be corrected by a combination of the fine movement of the reticle 4 and the fine movement of the wafer stage 6 Therefore, by correcting the tilt of the exposure area as described above before exposing the exposure area of the wafer surface. With this correction made, it is possible to transfer the pattern onto the wafer surface with high precision.

After adjusting the inclination in this manner, the pattern is transferred from the light source system 1 to the corresponding chip via the reticle 4.

In the above embodiment, the fine movement section 5.7 is provided for each of the reticle and the wafer stage, but as long as the fine movement section is provided for at least one, there is no need to provide a tilt correction mechanism for the other. There is no problem.

Also, here we have explained the case where detection and pattern transfer are repeatedly performed for each chip, but first the tilt of each chip is detected over the entire wafer, and then the tilt is determined for each chip based on the detection results. The pattern transfer may be performed by adjusting the .

Furthermore, the diffraction pattern does not necessarily have to be formed by concavities and convexities; for example, after forming concavities and convexities, a material different from that of the wafer is filled in the concavities to form a diffraction pattern with a flat surface, which allows the diffraction light to be It is also possible to obtain

[Effects of the Invention] As described above, according to the present invention, the local tilt of the wafer surface can be accurately detected without narrowing the laser beam to a narrower width than the width of the scribe line. can be easily done. Therefore, a reduction projection exposure apparatus capable of highly accurate pattern transfer can be manufactured at a relatively low cost.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the overall configuration of a reduction projection exposure apparatus according to an embodiment of the present invention, and FIG. 2 is for explaining the principle of tilt detection of a wafer surface local tilt detecting section provided in the apparatus of FIG. and FIG. 3 are diagrams showing examples of diffraction patterns used for tilt detection. 3... Main axis of optical system, 4... Reticle, 5... Reticle fine movement section, 6... Wafer, 7... Stage fine movement section, 8... Wafer surface local tilt detection section. Figure 1] 1 Figure 2 (A) (C) 3 CB) CD) Figure

Claims (5)

[Claims] (1) A wafer surface local tilt detection unit that irradiates a laser beam onto a diffraction pattern formed in the exposure area of the semiconductor wafer surface and detects the tilt of the exposure area with respect to the main axis of the optical system from the angle of the diffracted light, and this detection unit 1. A reduction projection exposure apparatus comprising: a fine movement section that tilts at least one of a wafer stage and a reticle with respect to a main axis of an optical system so as to correct a detected tilt. (2) The reduction projection exposure apparatus according to claim 1, wherein the diffraction pattern is formed on a scribe line. (3) The reduction projection exposure apparatus according to claim 1, wherein the diffraction pattern consists of a strip pattern arranged at equal intervals. (4) The reduction projection exposure apparatus according to claim 3, wherein the strip patterns arranged at equal intervals are formed obliquely with respect to the scribe line. (5) The reduction projection exposure apparatus according to claim 1, wherein the diffraction pattern is comprised of a dot pattern arranged in a matrix.