JPS60176235A - Masking original plate for x-ray exposure - Google Patents

Abstract

PURPOSE:To produce the titled plate with sufficient contrast making patterning of X-ray absorbing layer feasible utilizing a conventional dryetching device. CONSTITUTION:After cleaning both side polished disc-type silicon single crystal wafer W, nitride silicon layers 1, 1' are respectively formed on the surface and backside by vacuumized CVD process to constitute a substrate. Next an X-ray absorbing layer 2 made of platinum silicide is immediately formed by means of sputtering process utilizing separated targets of platinum silicon. After the forming process of layer 2, a making original plate is produced by insufficient heat annealing process in N2 atmosphere. Resist 4 formed on the X-ray absorbing layer 2 is exposed and developed to produce stripe patterned resist 4. Finally the layer 2 is dry-etched by means of a reactive sputter etching device as one kind of conventional dry-etching devices.

Description

Detailed Description of the Invention (Technical Field of the Invention) A mask original plate used when printing a fine pattern on a wafer by X-ray exposure during the manufacture of a corporate-scale integrated circuit (LSI) according to the present invention, particularly an X-ray absorption The present invention relates to an original plate whose layers can be easily patterned.

(Background of the Invention) A mask for X-ray exposure basically consists of a substrate (1) that can transmit X-rays and a predetermined fine pattern of X-rays formed on the substrate (1) as shown in FIG. Line absorption 1! (2), a thin film of silicon nitride, boron nitride polyimide resin, or the like is used as the substrate (1), and gold, platinum, or the like is used as the X-ray absorbing layer (2). However, if the thin film of silicon nitride or polyimide resin used as the substrate (1) has a large area, it will not be possible to maintain its flatness, so it is actually supported by a frame (3) as shown in FIG.

In any case, the mask original plate consists of a substrate that can transmit X-rays and an X-ray absorption layer formed on it, and the mask is manufactured by patterning this X-ray absorption layer into a predetermined fine pattern. However, the gold, platinum, etc. that have been used so far are extremely difficult to pattern with high precision.
In particular, when processing wires to a wire width of 2 mm or less, a patterning method using a normal dry etching device cannot be used. For this reason, complicated buttering methods have been developed as disclosed in Japanese Patent Application Laid-Open No. 53-17075.

The reason why high-precision patterning is difficult is: ■ In order to increase the absorption of X-rays and increase the contrast of the mask, the thickness of the X-ray absorption layer to be patterned must be 0.4 to 1 pm. However, when etching is performed, the cross section of the absorption layer is not vertical as shown in Figure 2, and ■RI B (IJ active ion etching)
When patterning is carried out using a conventional dry etching device such as ion beam etching or ion beam etching, the gold particles move, making it impossible to form a pattern with a line width of 1 μm or less at a predetermined position with high precision.

(Object of the Invention) Therefore, the object of the present invention is to provide a mask original plate for X-ray exposure, which allows the X-ray absorbing layer to be buttered by buttering using a conventional dry etching device, and which provides sufficient contrast. There is a particular thing.

(Summary of the Invention) As a result of intensive research, the present inventor has found that by using silicide of an X-ray absorbing metal instead of gold or platinum as an X-ray absorbing layer, even buttering using a normal dry etching device can be achieved. The inventors have discovered that it is possible to obtain a highly accurate fine pattern and also obtain a mask with sufficient contrast, leading to the completion of the present invention. Therefore, the present invention
In a mask original plate for X-ray exposure consisting of a substrate capable of transmitting X-rays and an X-ray absorption layer formed on the substrate, the X-ray absorption layer is made of silicide of an X-ray absorbing metal. Some of the silicides used in the present invention, which provide the characteristic original plate for X-ray exposure, are known and have the general formula Mx
It is indicated by S i y. M is an X-ray absorbing metal, such as Pt, Pd, W, Ta.

Examples include Mo, Ho, Er, Os, and Ir. However, even if the metal is X-ray absorbing, metals such as gold that do not form silicide with Si or are difficult to form are excluded.

Such silicide is CV D (chemical
It may also be formed in situ by vapor deposition. In any case, after forming the X-ray absorbing layer, it is preferable not to perform thermal annealing or to perform controlled thermal annealing to maintain the grain size at 1000λ or less.

In addition to the method of forming an X-ray absorption layer while forming silicide on the substrate on the spot, silicide is prepared in advance and vacuum thin film formation is performed using the silicide as a target or evaporation source by sputtering, vacuum evaporation, ion plating, etc. The X-ray absorbing layer may be formed on the substrate by a method.

In order to obtain the necessary contrast, such an X-ray absorption layer generally has a film thickness of 0.2 to 2 μm, preferably 0.3 μm, depending on the X-ray absorption coefficient depending on the resist value and the X-ray wavelength.
The film thickness should be ~1.0 μm! As the underlying substrate for forming the absorption layer, the above-mentioned boron nitride, silicon nitride, polyimide, polyethylene, polyester,
Resins such as polyvaraxylene are used. Silicon nitride is commonly used as a chemical vapor (CVD) material on a silicon plate used as a semiconductor wafer.
Polyimide and other resins are formed by coating a silicon plate in the form of a solvent solution and drying it.

The mask original plate of the present invention, which has the above-mentioned X-ray absorbing layer formed on such a substrate, is etched using a normal dry etching device after forming a resist in a predetermined pattern on the X-ray absorbing layer. When this is carried out, an X#J exposure mask having a predetermined fine pattern is obtained. When looking at the cross section of the X-ray absorbing layer of the obtained mask, it has a vertical cross section as shown in FIG. 3, and is located at an accurate predetermined position.

Hereinafter, the present invention will be specifically explained with reference to Examples with reference to FIG. 4, but the present invention is not limited thereto.

(Example 1) (1) After cleaning a disc-shaped silicon single crystal wafer (W) with a thickness of 0.38 mm and a diameter of 50 mm, which was polished on both sides, a silicon nitride layer (1) with a thickness of 21 rn on both the front and back surfaces by low pressure CVD,
(1') is formed and used as a substrate.

Next, on the silicon nitride layer (1) on the surface, sputtering is performed using a split target of platinum and silicon to form an X-ray absorbing layer (2) made of platinum silicide with a thickness of 1 um on the spot. Let it form. After formation, N.J.
Insufficient thermal annealing is performed at 350° C. for 60 minutes in an ambient atmosphere to obtain a mask original plate of the present invention.

(2) After forming a resist (4) with a thickness of 1 μm on the X-ray absorption layer (2) (see Figure 4 (1)),
9. Stripe pattern resist (
4) Wo4ru (see Figure 4 (2)).

Next, C1 containing 5% 02 was etched using a reactive sputter etching device, which is a type of normal dry etching device.
'4F, gas pressure: 0.05 'J'orr,! The exposed X-ray absorption layer (2) is dry etched under the condition of frequency power: 100W. As a result, the X-ray absorbing layer (2) is patterned. Thereafter, the resist pattern (4) is peeled off and removed using oxygen plasma.

(3) After spin-coding the polyimide face solution on the buttered X-ray absorption 1fI (2'),
A polyimide resin protective film (5) having a thickness of about 2 μm is formed (see FIG. 4 (3)).

(4) Next, apply a layer of 1 thick on the silicon nitride layer (1') on the back side.
After forming a resist (6) of .mu.m, a predetermined 7-frame pattern resist (6) is formed by exposing and developing a predetermined 7-frame pattern.

After that, the exposed portion of the silicon nitride layer (1') is removed by CF plasma etching, and the silicon nitride layer (1') is buttered (see Figure 4).
.

(5) After removing the remaining resist (6), the exposed portion of the wafer l) is removed by etching using a 30% KOH aqueous solution to produce a frame (3).

In this way, a mask for Xa exposure as shown in FIG. 4(5) is obtained. The obtained mask has a line width of 1 of the X-ray absorption layer (2).
.mu.m were formed in an orderly and well-shaped predetermined position, and the cross-sectional shape was approximately as shown in FIG.

(Example 2) A mask having a highly accurate pattern was obtained by processing in exactly the same manner as in Example 1, except that palladium silicide was used as the X-ray absorbing layer (2) and the film thickness was 0.8 μm.

The masks of Examples 1 and 2 were exposed to an X-ray exposure device (the X-rays had wavelengths of 8.
When a PMMA resist with a thickness of 1μ"n formed on a silicon wafer was exposed to light using the 34A l'J-Kα line), there was no film thinning of the X-ray absorbing layer (2). We were able to obtain a resist image with very high precision.

As a result, it was confirmed that the mask of this example had sufficient contrast.

(Effects of the Invention) As described above, according to the present invention, it is possible to obtain a mask original plate for X-ray exposure that can be patterned with high precision using a normal dry etching device and has an X-ray absorption layer with sufficient contrast.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a row of conventional X-ray exposure masks. FIG. 2 is a partially enlarged view of FIG. 1. FIG. 3 is a partially enlarged sectional view showing an example of a mask manufactured from the mask original plate of the present invention. FIG. 4 is a cross-sectional view of the mask original plate at each step of manufacturing a mask from the mask original plate of this embodiment. (Explanation of symbols of main parts) 1...Substrate that can transmit X-rays 2...X-ray absorption layer 3...Frame 4...Resist 5...Polyimide (retaining layer) 6... Regime, tW...Silicon plate used for wafer iI'l? F
Applicant Nippon Kogaku Kogyo Co., Ltd. Agent Takashi Watanabe Figure 1 Figure 2 Figure N3

Claims (1)

[Scope of Claims] I. In an X-ray exposure mask original plate comprising a substrate capable of transmitting X-rays and an X-ray absorbing layer formed on the substrate, the X-ray absorbing layer has an X-ray absorbing property. An original plate for X-ray exposure characterized by being made of metal silicide. 2 The X-ray absorbing metal is Pt, Pd, W, T
a. The original plate for X-ray exposure according to claim 1, characterized in that it is Mo, Ho, Br, Os, or Ir. 3. The original plate for X-ray exposure according to claim 1, wherein the silicide has a crystal grain size of 1000A or less.