JPS63200530A - Manufacture of x-ray mask - Google Patents

Abstract

PURPOSE:To equip an X-ray absorber layer with a pattern having vertical side walls without destroying an X-ray transmission layer by laminating a non-etching thin film and the X-ray absorber layer on the X-ray transmission layer. CONSTITUTION:An Si3N4 film 2 (tensile stress of its film is around 5X10<8> dyne) is prepared on a silicon wafer 1 with a plasma CVD technique and an SiO2 film 3 (tensile stress of its film is 0), a W-film 4 (tensile stress of its film is 0), and a dry-etching resistance electron beam resist 5 are laminated with a high frequency spatter technique and then a mask 5 is produced by performing electron beam lithography and development of the above films after carrying out pre-bake. An RIE is performed by using SF6/CCl4. When a slight etching is continued after exposing the SiO2 film 3, a W-pattern 4 having vertical walls is obtained and the Si3N4 film 2 does not change at all. As a result, Si 1 is etched from the rear of the wafer 1 and a patterned mask is completed after leaving a frame part.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for manufacturing an X-ray mask.

BACKGROUND OF THE INVENTION With the increasing density of semiconductor integrated circuits, patterns are becoming increasingly finer, and it is desired to establish a technique for exposing fine patterns with dimensions of 1 μm or less, that is, so-called submicron patterns.

X-ray exposure is expected to be a submicron pattern transfer technology because it has advantages such as high resolution and increased productivity due to batch transfer, and is used as a high-contrast, high-precision X-ray mask. development is underway.

A conventional method for manufacturing an X-ray mask will be described with reference to FIG. As shown in FIG. 2a, an X-ray transmitting body 7, for example, a silicon nitride layer, is formed on a silicon (Si) wafer 1 serving as an X-ray mask support, and an X-ray absorbing body 8, For example, a tungsten film is formed. Next, as shown in FIG. 2, a resist pattern 9 of a predetermined shape is formed.
is formed, and the X-ray absorber 8 located directly below the opening of this resist pattern is dry etched. By going through the above process, an X-ray absorber pattern as shown in FIG. 2C is obtained. Finally, the silicon wafer 1 is etched from the back side, leaving the support frame, to obtain an X-ray mask as shown in FIG. 2d.

Problems to be Solved by the Invention In X-ray exposure, the X-ray mask has a large effect on the transferred pattern. The cross-sectional shape of the X-ray absorber pattern needs to have vertical side walls. however,
When the X-ray absorber is processed by dry etching as in the conventional example, the cross-sectional shape of the X-ray absorber pattern is such that the opening of the X-ray absorber extends along the base, as shown in the enlarged cross-sectional view of Fig. 3. It becomes a drawn shape. If etching is continued even after the X-ray absorber is opened, the skirt of the opening will disappear, but
When the X-ray absorber 8 is made of a metal such as tungsten or tantalum that can be etched with a fluorine-based gas, the silicon nitride or boron nitride of the xis transmitter 7 has a very high etching speed with respect to the etching gas. She gets etched deeply. For this reason, X
There was a problem in that the stress in the radiation transmitting body 7 changed and the mechanical strength deteriorated.

Means for Solving the Problem In order to solve this problem, the present invention forms a non-etchable thin film on the X-ray transmitting layer, forms an X-ray absorbing layer on this, selectively etching the X-ray absorber layer without affecting the underlying X-ray transmitter layer;
An X-ray absorber pattern with vertical sidewalls is obtained.

Function: By using the present invention, it is possible to manufacture an X-ray mask having an X-ray absorber pattern with vertical side walls and no skirting.

Embodiment FIGS. 1a to 1g are cross-sectional views in the order of manufacturing steps of an X-ray mask shown for explaining an embodiment of the method of manufacturing an X-ray mask according to the present invention. Explain the invention in detail.

First, as shown in FIG. 1a, on an X-ray mask support, for example, a silicon wafer 1 with a diameter of 4 inches, an X, III transmitting body, for example, a silicon nitride film (Sj3N+ film) 2 is formed by plasma CVD. Deposit to a thickness of 1.5 pm. Note that in this plasma CVD method, 95%N215%Si
Using H4 gas as the reaction gas, gas flow rate 250cc/min,
2 under the conditions of substrate temperature 300'C and high frequency power 200W.
Deposited for 5 minutes. The stress of this film is 5X1 in terms of tensile stress.
The size is controlled to 0.08 dyne/cut.

Next, a 5i02 film 3 of 0.0
Deposit to a thickness of 2 μm. The sputtering conditions were: argon (Ar) was used as the discharge gas, the discharge gas pressure was 5 millitorr, and the high frequency cuff was 00W. :did. The stress of this membrane is
It is zero.

Thereafter, as shown in FIG. 1, a tungsten film 4 is deposited to a thickness of 0.6 ttm. The sputtering conditions at this time were that argon (Ar) was used as the discharge gas, and the discharge gas pressure was 30 mTorr with a high frequency electric cuff of 00 W, and the stress of the film produced under these conditions was zero.

Next, as shown in FIG. After pre-baking at ℃ for 25 minutes,
A pattern is drawn using an electron beam 6 and developed for 1 minute with a developer of isoamyl acetate:ethyl cellosolve-1:4 to form a desired resist per 5 = turn as shown in FIG. 1d.

Next, using the resist pattern as a mask, the tungsten film 4 is etched for 10 minutes by reactive ion etching to form the underlying 5i02 film 3, as shown in FIG. 1e.
Open until exposed.

At this time, the cross-sectional shape of the tungsten pattern is such that the opening of the X-ray absorber has a tail, as shown in FIG.

After that, by continuing etching for 2 minutes, Figure 1 f
It is possible to obtain a tungsten pattern with a cross-sectional shape having vertical sidewalls as shown in FIG.

The etching conditions at this time were to use sulfur hexafluoride (SFs)/carbon tetrachloride (CCe4) as the reaction gas, supply the gas at a gas flow rate of 5 cm/min, and set the gas pressure at 5 mTorr.
The high frequency power density is 0.18w/cnr.

According to the etching process under these conditions, the above electron beam resist 5. Tungsten film 4. The etching speed of the 5i02 film 3 is 300 A/min, 2600 A/min, and 2600 A/min, respectively.
, 50A/min. Furthermore, under these conditions, the etching rate of the Si3N4 film 2 of the X-ray transmitter is 1500 A/min, but in the present invention, since no etching is performed at all, the stress in the film is the same as the stress deposited. It hasn't changed.

Finally, etching the silicon wafer 1 from the back side,
The X-ray mask is completed by leaving the part that will become the support frame.

In the above description, the Si3N4 film 2 was used as the X-ray transmitter, the 5i02 film 3 was used as the etching prevention layer, and the tungsten film 4 was used as the X-ray absorber. In addition, tantalum (Ta), which is etched using fluorine gas as an X-ray absorber,
Boron nitride (BN) or the like can be used as the X-ray transmitting material, and as the etching prevention layer, the etching speed for fluorine gas is one-tenth that of the X-ray transmitting material.
Any thin film made of the following very slow (and high X-ray transmittance) materials is sufficient; for example, alumina (Al2O2) can also be used.

Effects of the Invention As detailed above, when etching an X-ray absorber, the etching rate of the etching gas is very slow, and the etching rate of the X-ray transmissive body is very slow. By forming an etching prevention layer that transmits the It is possible to form a body pattern and produce a high-contrast, high-precision X-ray mask.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of an X-ray mask manufactured by the manufacturing method of the present invention, Fig. 2 is a cross-sectional view of an X-ray mask manufactured by a conventional manufacturing method, and Fig. 3 is a conventional X-ray absorber. FIG. 3 is a cross-sectional view illustrating a cross-sectional shape of a pattern. 1...Silicon wafer, 2...Silicon nitride film, 3...S i O2 film, 4...
...Tungsten film, 5...Electron beam resist,
6...Electron beam. Name of agent Patent attorney Toshio Nakao No. 18 Figure 13 - 1110 - - - - - - - - -4

Claims (1)

[Claims] A step of forming an X-ray transmitting layer on the X-ray mask support, then forming a non-etchable and X-ray transparent thin film thereon, then forming an X-ray absorbing layer, A method for manufacturing an X-ray mask, comprising a step of selectively etching a ray absorber layer to form a predetermined X-ray absorber pattern.