JPH0612754B2 - Projection exposure device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a projection exposure apparatus, and in particular, it has an aligner function for performing relative positioning with respect to a projection pattern of a mask (including a reticle) and an object to be exposed such as a wafer with high accuracy. The present invention relates to a projection exposure apparatus.

[Background technology]

The photolithography technique, which is one of the manufacturing steps of semiconductor devices, requires a step of patterning a thin film on a wafer by projecting and exposing a mask pattern formed on a mask to a normal size or a reduced size. In this projection exposure, all the mask patterns sequentially projected on the same wafer must be projected and exposed at the same position on the wafer. Therefore, the relative positioning of the mask and the wafer during projection exposure of each mask is required. Must be done.

Conventionally, this kind of positioning is performed by aligning the alignment mark formed on the pattern part of the previous process formed on the wafer with the alignment mark formed on the pattern part of the mask of the current process. There is.
For example, FIG. 1 is an example of a conventional projection exposure apparatus (electronic materials published by the Industrial Research Group, 1981, Supplement, pages 103 to 109, date of issue, October 10, 1981).
A wafer 1 placed on top is placed, on the other hand, a projection lens 5 is arranged on this moving stage 2, a mask 3 is set on this projection lens, and a light source 4 is irradiated from above the mask 3.
While illuminating the mask with light (g line), the projection lens 5 projects and images the mask pattern on the wafer 1. on the other hand,
An aligner section including a g-ray light source 6, a half mirror 7, a lens 8, a mirror 9 and a pattern detection unit 10 is provided above the mask 3 side, and the light of the g-ray light source 6 is projected onto the wafer 1 through the mask 3. Then, the reflected light is detected by the pattern detection unit 10. The g-line is projected on the alignment mark forming portion of the wafer 1 after passing through the corner of the mask 3, whereby the alignment mark is detected and the relative position, that is, the relative alignment between the mask 3 and the wafer 1 is detected. Can be done.

However, in this conventional configuration, since the g-line of monochromatic light is used for pattern detection, interference occurs in the thin film on the surface of the wafer 1, and this interference changes due to fluctuations in film thickness, so that the signal waveform of the pattern detection unit is changed. This causes fluctuations and makes the alignment accuracy unstable. Also,
Since the same g-line as the light for exposure is used to detect the alignment mark, it is necessary to perform alignment in the peripheral area of the chip on the wafer that is not affected by the exposure of the wafer. There is also a problem that the alignment accuracy is lowered due to deviation from the central axis.

[Object of the Invention]

An object of the present invention is to provide a projection exposure apparatus that enables stable alignment, improves alignment accuracy, and achieves improvement in projection exposure throughput.

The above and other objects and novel characteristics of the present invention are
It will be apparent from the description of the present specification and the accompanying drawings.

[Outline of Invention]

The outline of a typical one of the inventions disclosed in the present application will be briefly described as follows.

That is, a beam splitter is arranged in a projection exposure optical system using monochromatic light, and a pattern detection light source that faces the beam splitter and has a continuous spectrum, a chromatic aberration correction lens system, and a pattern detection unit. By providing a system and aligning it with the mask by detecting the alignment mark formed on the wafer by this pattern detection system, it is possible to prevent light interference and to perform alignment in the central part of the chip. This makes it possible to stabilize the alignment and improve the accuracy.

[Embodiment 1] FIG. 2 is a block diagram of an embodiment of the projection exposure apparatus of the present invention, in which reference numeral 11 is a mask as a projection pattern in which a light-impermeable film is formed in a required pattern on a glass substrate, 12
Is a wafer as an exposed body on which the pattern of the mask 11 is projected and exposed. A predetermined pattern is formed on the surface of the wafer 12 in the previous step, and an alignment mark is formed on a part of the pattern.
In the present embodiment, the alignment mark does not necessarily have to be provided as described later. The wafer 12 is placed on the moving stage 13 and moved in the X, Y, Z, and θ directions by the stage moving mechanism 14.

An exposure light source 15 for emitting monochromatic light (g-line or the like) is installed above the mask 11 to irradiate the mask 11, while a lower position of the mask 11 includes a plurality of lenses. A projection lens system 16 is provided to project and image the pattern of the mask 11 on the surface of the wafer 12 at a required magnification (1/10, 1/5, 1/1). The projection lens system 16 is preferably designed to have characteristics of high NA (numerical aperture), low optical distortion, and wide exposure area with respect to the exposure light source light. 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 provided at the center position of the optical axis of the projection exposure optical system to form an optical axis of the pattern detection system in the direction of 90 ° 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, and further the half mirror 19 is provided.
The pattern detection unit 21 is provided so as to face the above, and the pattern detection unit is configured. The pattern detecting light source 20 can emit a continuous spectrum light such as white light, and the light is a photoresist (not shown) provided on the wafer 12.
Is not exposed to light. On the other hand, the chromatic aberration correction lens system 18 is configured to correct and cancel the chromatic aberration generated 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 (the reflected light of the light from the pattern detection light source 20) to detect the pattern formed on the wafer 12 up to the previous step and the alignment mark of a part thereof. It is possible to recognize the pattern by outputting the pattern detection signal of, and electrically processing this. The output of the pattern detection unit 21 is sent to the control unit 22 to control the stage moving mechanism 14 and various mechanisms and circuits not shown.

According to the above configuration, the white light of the pattern detection light source 20 is projected onto the alignment mark of the wafer 12 through the beam splitter 17 before the mask 11 is projected, and the reflected light is reflected by the beam splitter 17 and the half mirror 19.
It is reflected by and input to the pattern detection unit 21.
As a result, the pattern detection unit 21 detects the absolute position of the wafer 12 after pattern recognition of the alignment mark and other patterns by electric signal processing, and the controller 22 compares this with the mask position. As a result, a relative positional deviation between the mask 11 and the wafer 12 can be detected, and if the stage moving mechanism 14 is controlled based on this deviation, the wafer 12 can be moved by the moving stage 13 and can be aligned with the mask 11. it can. At this time, since the continuous spectrum light is used for the pattern detection, optical interference does not occur in the photoresist thin film on the surface of the wafer 12, and accordingly, the film thickness variation of the photoresist thin film is caused as in the conventional case. It is possible to obtain a stable detection (electrical) signal and perform stable pattern detection or alignment without causing a phenomenon such as fluctuation of reflected light. The chromatic aberration generated in the projection lens system 16 by using the white light can be corrected by the chromatic aberration correction lens system 18, and the occurrence of a detection error is prevented. Also,
By using white light, it is possible to prevent exposure to the photoresist during alignment, so it is also possible to detect the wafer position by performing pattern detection on the optical axis, in other words, in the center of the chip. Improvement can be realized. As a result, alignment can be automated and throughput can be improved.

Needless to say, the pattern of the mask 11 can be projected and imaged on the wafer 12 by the projection optical system 16 by using the monochromatic light (g line) of the exposure light source 15 after the alignment.

[Embodiment 2] FIG. 3 is a constitutional view of another embodiment of the present invention, in which the constitutions of the projection exposure optical system and the pattern detection unit are different from those of the above-mentioned embodiment. In the figure, the same or equivalent parts as in FIG. 2 are designated by the same reference numerals.

In this embodiment, the wafer 1 placed on the moving stage 13 is
2, the projection lens system 16 is arranged, and a dichroic mirror 17A as a beam splitter, a chromatic aberration correction lens system 18, a half mirror 19 and a pattern detection unit 21 are arranged on the optical axis thereof. The light source 2 for pattern detection faces the half mirror 19 on the upper side.
While 0 is arranged, the mask 11 and the exposure light source 15 are arranged so as to face the dichroic mirror 17A. The pattern detection light source 20 uses white light that is continuous spectrum light, and the chromatic aberration correction lens 18 can correct and cancel chromatic aberration. Also, the dichroic mirror 17A is g
It is configured so that only the line can be reflected, and the g-line light of the exposure light source 15 that has passed through the mask 11 can be reflected toward the wafer 12.

According to the above configuration, the white light of 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 and the like, and the chromatic aberration correction lens system 18 goes through the reverse process. The chromatic aberration is corrected and is incident on the pattern detection unit 21, where the pattern on the wafer 12 is recognized. Based on the recognition of the pattern, the control unit 22 obtains the positional deviation with respect to the mask 11, operates the stage moving mechanism 14 to move the moving stage 13 and the wafer 12, and aligns with the mask 11. After alignment, the mask 11 is illuminated by the exposure light source 15 and the dichroic mirror 17A is illuminated.
The pattern of the mask 11 is projected and exposed on the wafer 12 by the projection lens system 16 by utilizing the reflection of the light.

Also in this embodiment, since white light is used for detecting the alignment pattern of the wafer 12, the wafer 1
Instability of detection due to interference in the photoresist thin film on 2 can be prevented, and stabilization can be improved. Further, since white light is used, it is possible to detect the pattern at the center of the optical axis, that is, the center of the chip, and improve the alignment accuracy. Further, in this embodiment, the projection lens system 16 and the chromatic aberration correction lens system 18 can be arranged on the linear optical axis, so that the pattern detection accuracy can be further improved.

〔effect〕

(1) Since continuous spectrum light is used for pattern detection when detecting the position of the object to be exposed, it is possible to prevent optical interference due to thin films such as photoresist on the surface of the object to be exposed, and to accompany changes in the thickness of the thin film. It is possible to prevent the fluctuation of the reflected light on the surface of the exposed object, to perform stable pattern detection, and to perform stable alignment between the exposed object and the mask.

(2) A beam splitter is arranged in the projection exposure optical system, a pattern detection system is provided facing the beam splitter, and pattern detection light having a continuous spectrum is used for pattern detection in the pattern detection system. Since it is configured to detect the pattern on the exposed body, it is possible to detect the pattern at the center of the semiconductor chip, which is the center of the optical axis, and improve the pattern detection accuracy and the alignment accuracy.

(3) Since the chromatic aberration correction lens system is arranged in the pattern detection system, the chromatic aberration generated in the projection lens system is eliminated by using the pattern detection light composed of continuous spectrum light, and the pattern detection is suitably performed. be able to.

(4) With the stabilization of the above-described pattern detection, the signal processing method is simplified, the alignment is automated, and the time is shortened to improve the throughput.

(5) By using white light as the continuous spectrum light as the pattern detection light, it is possible to prevent the photoresist from being exposed to light at the time of alignment when projecting and exposing a semiconductor wafer, for example, on the optical axis. It is also possible to detect the position of the semiconductor wafer by performing pattern detection in the central portion of the semiconductor chip, and it is possible to improve the alignment accuracy, and thus to automate the alignment and improve the throughput.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments and can be variously modified without departing from the scope of the invention. Nor. For example, a general half mirror may be used for the beam splitter, and the arrangement position thereof may be slightly different from the configuration of the projection lens system. Further, the light for pattern detection may be continuous spectrum light in a wavelength range capable of preventing interference.

[Field of application]

In the above description, the case where the invention made by the present inventor is mainly applied to the projection exposure technique of the mask pattern on the semiconductor wafer which is the field of application which is the background has been described, but the invention is not limited thereto. Alternatively, it can be applied to photomask manufacturing technology and other photographic technology in general.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a conventional device, FIG. 2 is a configuration diagram of an embodiment device of the present invention, and FIG. 3 is a configuration diagram of another embodiment device of the present invention. 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, 20 ... Pattern detection light source, 21 ... Pattern detection unit, 22 ... Control section.

Front Page Continuation (72) Inventor Nobuyuki Iriki 1450, Kamisuihonmachi, Kodaira-shi, Tokyo Inside Musashi Factory, Hitachi, Ltd. (56) Reference JP-A-52-52579 (JP, A) US Patent 4358892 (US, A)

Claims (3)

[Claims] 1. An apparatus comprising a projection exposure optical system for projecting and exposing a projection pattern of a mask, a reticle, etc. onto an object to be exposed, such as a semiconductor wafer, by using monochromatic light, on the wafer through the projection exposure optical system. Is provided with a pattern detection system for observing the target pattern, and pattern detection light composed of continuous spectrum light is used for pattern detection in the pattern detection system to detect the pattern on the exposed object. The detection system includes a pattern detection light source for emitting continuous spectrum light, a chromatic aberration correction lens system for eliminating chromatic aberration generated in the projection exposure optical system, and the continuous spectrum light as pattern detection light from the chromatic aberration correction lens system. Is input as a pattern detection signal and pattern recognition is performed based on this pattern detection signal. A detection unit and a control unit that compares the position of the wafer detected by the pattern detection unit with the mask position to detect a shift in the relative position between the mask and the wafer, and controls the stage moving mechanism based on the shift. A projection exposure apparatus provided. 2. The projection exposure apparatus according to claim 1, wherein the projection exposure optical system has a beam splitter arranged to face the pattern detection system. 3. The beam splitter is provided at a center position of an optical axis of the projection exposure optical system, projects the continuous spectrum light as pattern detection light to a position corresponding to the center of a projection pattern, and patterns at the position corresponding to the center. The projection exposure apparatus according to claim 2, wherein the projection exposure apparatus is configured to perform detection.