JPS60177625A - Projection exposure device - Google Patents

Abstract

PURPOSE:To contrive to enhance stabilization and precision of positioning of a wafer and a mask at a projection exposure device by a method wherein a beam splitter, a continuous spectrum light source, a chromatic aberration compensating lens, and a pattern detection unit are provided to an exposure optical system using monochromatic light. CONSTITUTION:White light emitted from a pattern detecting light source 20 for positioning is projected to a wafer 12 through a half mirror 19, a dichroic mirror 17, and a projective lens 16, passed through the reverse travel, chromatic aberration is corrected according to lenses 18, and a pattern on the wafer is recognized according to a detection unit 21. The transferring mechanism 14 of a table 13 is controlled 22 conforming to recognition, and the wafer and a mask 11 are positioned. Then the mask 11 is illuminated according to a monochromatic exposure light source 15, and a mask pattern is projected on the wafer according to the lenses 16 utilizing reflection of a mirror 17. Because white light is used when positioning is performed, unstability of detection according to the interference of a resist thin film on the wafer is checked, pattern detection attaching importance to an optic axis (attaching importance to a chip) can be also attained, and precision of positioning is enhanced. Moreover, because the lenses 16, 18 are arranged on the optical axis, precision of pattern detection is elevated.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a projection exposure apparatus, and more particularly to a projection exposure apparatus equipped with an aligner function that performs relative positioning of a projection pattern such as a mask and an exposed object such as a wafer with high precision. It is something.

[Background technology]

Photolithography technology, which is one of the steps in the manufacturing process of semiconductor devices, requires a step in which a mask pattern formed on a mask is scaled down to the same size or scale and projected onto a semiconductor wafer for patterning, thereby patterning a thin film on the wafer. During this projection exposure, all the mask patterns that are sequentially projected onto the same wafer must be projected at the same position on the wafer, and therefore, the relative positioning of the mask and the wafer must be determined during the projection exposure of each mask. It will definitely be done.

Conventionally, this type of positioning has been performed by matching the alignment mark formed on a part of the pattern in the previous process formed on the wafer with the alignment mark formed in part of the pattern of the mask in all processes. There is. For example, Fig. 1 shows an example of a conventional projection exposure apparatus (published by Kogyo Kenkyukai, electronic materials, 1981 special edition, pp. 103-109, date of publication: 10, 1981). A wafer 1 is placed on the moving stage 2, and a projection lens 5 is placed on the moving stage 2. A mask 3 is placed on the projection lens, and the mask is exposed to light from a light source 4 (g-line) irradiated from above the mask 3. While illuminating, a mask pattern is projected and imaged onto the wafer 1 using a projection lens 5. On the other hand, above the side of the mask 3 is a g-line light source 6. Half mirror 7, lens 8. An aligner section consisting of a mirror 9 and a pattern detection unit 10 is provided, and the light from the g-line light source 6 is transmitted through the mask 3.
The pattern detection unit 10 detects the reflected light. The g-line passes through the corner of the mask 3 and is projected onto the alignment mark forming area of the wafer 1, and this alignment mark is detected and the relative position, that is, the relative positioning of the mask 3 and the wafer 1, is determined. can be done.

However, since this conventional configuration uses monochromatic g-ray light for pattern detection, interference occurs in the thin film on the surface of the wafer 1, and this interference changes with changes in film thickness, resulting in a signal waveform in the pattern detection unit. This causes fluctuations and the alignment accuracy becomes unstable. Also,
Since the same g-line as the exposure light is used to detect the alignment mark, alignment must be performed at the periphery of the chip on the wafer, which is not affected by the exposure of the wafer, and the detection light is not affected by the wafer or mask. There is also the problem that alignment accuracy is degraded due to deviation from the central axis.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a projection exposure apparatus that enables stable alignment, improves alignment accuracy, and improves the throughput of projection exposure.

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

[Summary of the invention]

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

In other words, a beam splitter is disposed within a projection exposure optical system using monochromatic light, and a pattern detection system consisting of a continuous spectrum pattern detection light source, a chromatic aberration correction lens system, and a pattern detection unit faces the beam splitter. The pattern detection section detects alignment marks formed on the wafer and performs alignment with the mask, thereby making it possible to align at the center of the chip while preventing light interference.

This makes it possible to stabilize alignment and improve accuracy.

[Embodiment 1] FIG. 2 is a block diagram of an embodiment of the projection exposure apparatus of the present invention, in which 11 is a mask as a projection pattern in which a light-opaque film is formed in a desired pattern on a glass substrate;
is a wafer as an exposed object onto which the pattern of this mask 11 is projected and exposed. A predetermined pattern is formed on the surface of this wafer 12 in a previous process, and an alignment mark is formed on a part of the pattern.
In this embodiment, alignment marks may not necessarily be provided as described later. The wafer 12 is placed on a moving stage 13 and moved by a stage moving mechanism 14 in x, y, z, and θ directions.

An exposure light source 15 that emits monochromatic light (g-line, etc.) is installed above the mask 11 to irradiate the mask 11, while a plurality of lenses is installed below the mask 11. A projection lens system 16 is provided to project the pattern of the mask 11 onto the surface of the wafer 12 at a required magnification (1
/10°115.1/1). This projection lens system 16 preferably has a high N with respect to the exposure light source light.
It is designed to have the following characteristics: A (numerical aperture), low optical distortion, and wide exposure area. These exposure light source 15 and projection lens system 16 constitute a projection exposure optical system.

On the other hand, a beam splitter 17 such as a prism or a half mirror is interposed at the optical axis center position of the projection exposure optical system 16 to form an optical axis of the pattern detection system in a direction of 90 degrees with respect to the optical axis. . On the optical axis of this pattern detection system, a chromatic aberration correction lens system 18, a half mirror 19, and a pattern detection light source 20 are arranged.
A pattern detection unit 21 is provided opposite to the pattern detection unit 9 to constitute a pattern detection section. The pattern detection light source 20
can emit continuous spectrum light such as white light, and this light does not expose the photoresist (not shown) provided on the wafer 12. On the other hand, the chromatic aberration correction lens system 18 is configured to correct and eliminate chromatic aberration occurring in the projection lens system 16 by using white light. Further, the pattern detection unit 21 detects the reflected light from the surface of the wafer 12 (reflected light from the pattern detection light source 20) and detects the pattern formed on the wafer 12 in the previous process or the alignment mark of a part thereof. It is possible to output a pattern detection signal and perform pattern recognition by electrically processing this signal. The output of this pattern detection unit 21 is sent to a control section 22, which controls the stage moving mechanism 14 and two circuits of various mechanisms not shown.

According to the above configuration, before projecting the mask 11, the white light from the pattern detection light source 20 is projected onto the alignment mark of the wafer 12 through the beam splitter 17, and the reflected light is transmitted to the beam splitter 16 and the half mirror 19.
and input the reflected light to the pattern detection unit 21.

As a result, the pattern detection unit 21 performs pattern recognition of alignment marks and other patterns through electrical signal processing, detects the absolute position of the wafer 12, and compares this with the mask position in the control unit 22. As a result, the relative positional deviation between the mask 11 and the wafer 12 can be detected, and by controlling the stage movement mechanism 14 based on this deviation, the wafer 12 can be moved by the movement stage 13 and aligned with the mask 11. can. At this time, since continuous spectrum light is used for pattern detection, there is no optical interference in the photoresist thin film on the surface of the wafer 12, and therefore the film thickness of the photoresist thin film can be reduced as in the conventional method. Stable detection (
Stable pattern detection or positioning can be performed by obtaining electrical) signals.

By using white light, the chromatic aberration that occurs in the projection lens system 16 can be corrected by the chromatic aberration correction lens system 18, thereby preventing the occurrence of detection errors. In addition, by using white light, it is possible to prevent the photoresist from being exposed to light during alignment, so it is possible to detect the wafer position by detecting a pattern on the optical axis, in other words, at the center of the chip. Improved accuracy can be achieved. As a result, it is possible to automate positioning, and it is also possible to improve throughput.

It goes without saying that after alignment, the pattern of the mask 11 can be projected and imaged onto the wafer 12 by the projection optical system 16 using monochromatic light (g-line) from the exposure light source 15.

[Embodiment 2] FIG. 3 is a block diagram of another embodiment of the present invention, in which the configurations of the projection exposure optical system and the pattern detection section are different from those of the previous embodiment. In the figure, the same or equivalent parts as in FIG. 2 are given the same reference numerals.

In this embodiment, a wafer 1 placed on a moving stage 13 is used.
2, and a dichroic mirror as a beam splitter is placed on the front axis of the projection lens system 16.
17A Bichromatic aberration correction lens system 18. A half mirror 19 and a pattern detection unit 21 are arranged. A pattern detection light source 2 is provided facing the upper half mirror 19.
On the other hand, a mask 11 and an exposure light source 15 are arranged opposite to the dichroic mirror 23.

The pattern detection light source 20 uses white light that is continuous spectrum light, and the chromatic aberration correction lens 18 can correct and eliminate chromatic aberration. Further, the dichroic mirror 17A is configured to be able to reflect only the g-line, and can reflect the g-line light from the exposure light source 15 that has passed through the mask 11 toward the wafer 12.

According to the above configuration, the white light from the pattern detection light source 20 is projected onto the surface of the wafer 12 through the half mirror 19, the dichroic mirror 17A, the projection lens system 16, etc., and then passes through the chromatic aberration correction lens system 18 through the reverse process. The chromatic aberration is corrected and the light enters the pattern detection unit 21, where the pattern on the wafer 12 is recognized. By recognizing the pattern, the control unit 22 corrects the misalignment with the mask 11 and operates the stage moving mechanism 14 to move the movable stage 13 and the wafer 12 to align with the mask 11. After alignment, the mask 11 is illuminated with light from the exposure light source 15, and the pattern of the mask 11 is projected onto the wafer 12 by the projection lens system 16 using reflection from the dichroic mirror 17A.

In this embodiment as well, since white light is used to detect the alignment pattern of the wafer 12, the wafer 12
Detection instability due to interference in the photoresist thin film on the photoresist film 2 can be prevented and stability can be improved. Further, since white light is used, it is possible to detect a pattern centered on the optical axis, that is, the center of the chip, and it is possible to improve alignment accuracy. Furthermore, in this embodiment, since the projection lens system 16 and the chromatic aberration correction lens system 18 can be arranged on the straight optical axis, pattern detection accuracy can be further improved.

〔effect〕

(1) Since white light is used to detect the pattern when detecting the position of the wafer, it is possible to prevent light interference caused by thin films such as photoresist on the wafer surface, and to reduce the amount of light reflected from the wafer surface due to variations in the thickness of the thin film. Fluctuations can be prevented, stable pattern detection can be performed, and stable wafer and mask alignment can be performed.

(2) A beam splitter is provided in the projection optical system, and the pattern detection light is projected onto the wafer through this beam splitter, and white light is used for the pattern detection light, so the chip is located at the center of the optical axis. This makes it possible to detect patterns in the center of the image, improve pattern detection accuracy, and improve alignment accuracy.

(3) Since the chromatic aberration correction lens system is disposed within the pattern detection section, chromatic aberration caused in the projection lens system due to the use of white light can be eliminated, and pattern detection can be performed suitably.

(4) Along with the above-mentioned stabilization of pattern detection, the signal processing method is simplified, and alignment is automated, time is shortened, and throughput is improved.

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, a general half mirror may be used as the beam splitter, and its placement position may be slightly different depending on the configuration with the projection lens system. Moreover, the light for pattern detection does not need to be white light as long as it is continuous spectrum light in a wavelength range that can prevent interference.

[Application field]

In the above explanation, the invention made by the present inventor is mainly applied to the field of application which is the background of the invention, which is the projection exposure technology of a mask pattern onto a semiconductor wafer, but is not limited thereto. Alternatively, the present invention can be applied to mask manufacturing techniques and other photographic techniques in general.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a conventional device, FIG. 2 is a diagram of an embodiment of the present invention, and FIG. 3 is a diagram of another embodiment of the present invention. DESCRIPTION OF SYMBOLS 11... Mask, 12... Wafer, 13... Moving stage, 15... Exposure light source, 16... Projection lens system, 17... Beam splitter, 17A... Dichroic mirror, 18...・・Chromatic aberration correction lens system, 2
o...Light source for pattern detection, 21...Pattern detection unit, 22...Control unit. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. In an apparatus for projecting and exposing a projected pattern such as a reticle onto an exposed object such as a wafer, a beam splitter is disposed within the projection optical system of this apparatus, and the pattern is projected opposite to this beam splitter. 1. A projection exposure apparatus, comprising: a detection section; and a continuous spectrum light is used for pattern detection by the pattern detection section to detect a pattern on the object to be exposed. 2. The pattern detection section includes a light source for pattern detection that emits continuous spectrum light, a chromatic aberration correction lens system that eliminates chromatic aberration generated in the projection optical system, and a pattern detection unit that performs pattern recognition based on the pattern detection signal. A projection exposure apparatus according to claim 1, comprising: a projection exposure apparatus according to claim 1; 3. The beam splitter is provided at the center position of the optical axis of the projection optical system, and the pattern detection light is projected to a position corresponding to the center of the projection pattern to perform pattern detection at the position corresponding to the center. 2. Projection exposure apparatus according to item 2.