JPH05121297A - Manufacture of mask for x-ray lithography - Google Patents

Abstract

PURPOSE:To obtain an X-ray mask having a highly precise pattern arrangement in a technique of X-ray lithography which is necessary for the manufacture of LSI. CONSTITUTION:An SiN film 2 is formed on an Si wafer 1 and an X-ray absorber metal film 3 is formed thereon. Moreover, a resist film 4 is formed by coating and an LSI pattern 8 on a reticle 6 is transferred onto this film by using a reduction projection anligner. By using a resist pattern 4a thus obtained as a mask, the metal film 3 is etched selectively. Lastly, Si in an X-ray transmitting area is removed by etching and thereby an X-ray mask whereon the LSI pattern is transferred is obtained. By this method, the precision in a pattern position of the X-ray mask is improved and also the precision in a pattern arrangement is improved sharply.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray lithography mask for forming a fine circuit pattern of microelectronics such as a semiconductor device, and more particularly to the manufacture of an X-ray lithography mask having a high precision pattern arrangement accuracy. Regarding the method.

[0002]

2. Description of the Related Art Conventionally, an electron beam drawing method has been adopted for forming an LSI circuit pattern of an X-ray lithography mask (hereinafter abbreviated as an X-ray mask) because of the necessity of fine processing. In this case, the alignment accuracy of the mask is determined by the positional accuracy of the pattern drawn by the electron beam, but at present, the accuracy of the drawing position of the electron beam is insufficient, which has been a major problem in producing a mask with high array accuracy.

As for the mask manufacturing technique by this kind of electron beam drawing, for example, "Proc. Of 1", Journal of Japan Society of Applied Physics, Series 3 (JJAP Series 3).
989 Alternative. Sympo. On MicroProcess Conference
pp.93-98 ”.

[0004]

The alignment accuracy of the X-ray mask determines the alignment accuracy of the aligner and the overlay accuracy between the LSI patterns. Therefore, in order to improve the overlay accuracy, it is necessary to minimize the deviation of the pattern position coordinates between the masks used for LSI fabrication (called the inter-mask array accuracy). L
Since several tens of these masks are usually used for SI manufacturing, overlay accuracy becomes a very important issue.

Therefore, an object of the present invention is to provide a method of manufacturing an X-ray mask which can solve the problems of the prior art and can remarkably improve the alignment accuracy between masks.

[0006]

The object of the present invention is to use a reticle, on which a predetermined LSI pattern is formed by electron beam drawing, as an original image mask, and perform exposure using a reduction projection optical system using this original image mask. This is achieved by a method of manufacturing an X-ray mask, which comprises a pattern forming step of developing, and transfers and forms the LSI pattern of the reticle onto a mask base material.

As the light source of the reduction projection optical system, either ultraviolet light, far ultraviolet light, vacuum ultraviolet light, or X-ray can be used. Further, it is desirable to perform a phase shift process between the patterns so that an optical image of an adjacent pattern of the reticle has a phase difference so as to enhance the contrast of the adjacent optical image after passing through the reticle. As this phase shift process, for example, a light transmitting film made of glass or resin may be formed between the patterns of the reticle to reduce mutual interference of optical images from adjacent patterns, or the base of the reticle may be used. Concavities and convexities may be provided in the constituent optical material.

[0008]

The reticle used in the reduction projection optical exposure method is created by electron beam drawing. In this case, the deviation of the pattern position coordinates on the reticle depends on the reduction ratio of the exposure apparatus.
For example, the value is extremely small because the exposure is performed on the X-ray mask substrate by reducing the size to 1/5 to 1/10. Moreover, a slight deviation of the pattern position from the reference position due to the elephant distortion of the lens of the reduction optical system may be considered, but this occurs extremely reproducibly in the same optical system. The accuracy is very high.

Further, if the phase shift processing is performed between the patterns so that the optical images of the patterns adjacent to each other on the reticle have a phase difference, the interference of the adjacent optical images is reduced, so that the resolution is improved. Shows its power in exposing fine patterns.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

<Embodiment 1> FIG. 1 shows a manufacturing process diagram of an X-ray mask according to an embodiment of the present invention. First, as shown in FIG. 3A, the diameter is 4 inches and the thickness is 1
mm as a mask membrane material for Si wafer
An N film (thickness 2 μm) 2 is deposited by the CVD method. CV
SiCl ₂ H ₂ / NH ₃ was used as the D reaction gas.
A tungsten film (film thickness 0.6 μm) 3 is similarly deposited on the SiN film as a metal thin film for an X-ray absorber by the CVD method to form a mask substrate. WF ₆ / H ₂ was used as the CVD reaction gas in this case. Further, as the photoresist 4, SAL601 (negative type) manufactured by Shipley Co., Ltd. is used and is applied to a thickness of 1 μm.

Next, the LSI pattern 8 on the reticle 6 is transferred to the photoresist 4 by using a 5: 1 reduction projection exposure apparatus using a KrF excimer laser (not shown) as the light source 5. On the reticle 6, an LSI pattern 8 made of a chrome light-shielding film is formed on an optical glass substrate 9 by a pattern forming method by an electron beam direct drawing method as shown in the drawing, and a fluid silica is provided between adjacent patterns. Is subjected to a phase shift process using the Si oxide 7 formed by coating.

Next, as shown in FIG. 3B, W is dry-etched using the photoresist pattern 4a formed by development as an etching mask. The etching was performed by reactive ion etching, and SF ₆ was used as the reaction gas.

Finally, as shown in FIG. 3C, the underlying Si in the X-ray transparent region was removed by etching to form an X-ray mask. In addition, as an etching solution for the underlying Si,
A mixed solution of hydrofluoric acid, nitric acid, hydrochloric acid and acetic acid was used.

Thus, an X-ray mask including an LSI pattern having a minimum dimension of 0.15 μm was obtained. The value of the arrangement accuracy between masks of different masks is 0.03 μm or less, which is significantly reduced as compared with the case of 0.12 μm by the conventional electron beam drawing method.

<Example 2> As in Example 1, an X-ray resist 4 of SAL601 manufactured by Shipley Co., Ltd. was used as the X-ray resist 4 and applied to a thickness of 1 μm. Next, a soft X-ray having a wavelength of 100 to 120 Å was used for the light source 2
The LSI pattern 8 on the reticle 6 is transferred to the X-ray resist 4 using a 0: 1 reduction exposure apparatus. The steps after the resist development process were the same as in Example 1, and the intended X-ray mask was prepared.

According to this embodiment, an X-ray mask including an LSI pattern having a minimum dimension of 0.05 μm was obtained, and the mask alignment accuracy was 0.02 μm or less. This was superior to that of Example 1 in that the exposure light source had a shorter wavelength.

[0018]

As described above, according to the present invention, an X-ray mask having a fine pattern with high alignment accuracy can be realized.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram of an X-ray mask according to an embodiment of the present invention.

[Explanation of symbols]

1 ... Si (silicon wafer), 2 ... SiN (silicon nitride), 3 ... W, 4 ... Photoresist (or X-ray resist), 4a ... Resist pattern, 5 ... Exposure light (laser or soft X-ray), 6 ... Reticle, 7 ... Phase shift film, 8 ... LSI pattern made of chromium light-shielding film, 9 ... Optical glass substrate.

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[Procedure amendment]

[Submission date] October 15, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Taro Ogawa 1-280, Higashi Koikekubo, Kokubunji, Tokyo Metropolitan Research Center, Hitachi, Ltd.

Claims (4)

[Claims] 1. A pattern forming step of exposing a reticle, on which a predetermined LSI pattern is formed by electron beam drawing, as an original image mask, exposing it using a reduction projection optical system using this original image mask, and developing it. A method for manufacturing an X-ray lithography mask, which comprises transferring and forming the LSI pattern of the reticle onto a mask substrate. 2. The method for manufacturing an X-ray lithography mask according to claim 1, wherein the light source of the reduction projection optical system is constituted by any one of ultraviolet light, far ultraviolet light, vacuum ultraviolet light, or X-ray. 3. A phase shift process is performed between the patterns so that an optical image of an adjacent pattern of the reticle has a phase difference so as to enhance the contrast of the adjacent optical image after passing through the reticle. The method for manufacturing an X-ray lithography mask according to claim 1. 4. The method of manufacturing an X-ray lithography mask according to claim 3, wherein a light transmitting film made of glass or resin is formed as the phase shift process.