JP3122162B2 - Method of manufacturing X-ray mask and X-ray mask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an X-ray mask used for transferring a fine pattern such as a super LSI with high precision in an X-ray exposure apparatus and an X-ray mask manufactured by the method.

[0002]

2. Description of the Related Art The X-ray exposure method is known as a technique capable of transferring a fine pattern of sub-micron or less by using soft X-rays having a wavelength of 0.4 to 5 nm. Conventionally,
As a method for manufacturing an X-ray mask using a carbon film as an X-ray transparent thin film, for example, Windishman [He
nry Windishmann, "A75mm d
iameter diamond x-ray mem
brain ”, Proceedings of SPI
E 1263, 241 (1990)], a carbon film is formed on a silicon substrate, and a mixed solution of hydrofluoric acid, nitric acid and acetic acid (H
F: HNO ₃ : CH ₃ COOH = 2: 2: 1) isotropic wet etching to remove a part of the silicon substrate to form an opening to form an X-ray transmission window including an X-ray exposure region. I was

In the anisotropic wet etching of a silicon substrate with an alkaline solution, the above-mentioned hydrofluoric acid, which is capable of high-accuracy processing, has less liquid fatigue during etching, and requires liquid exchange during etching. , Compared to isotropic wet etching with a mixed solution of nitric acid and acetic acid,
Although having the advantage of simplicity, the carbon film has poor alkali resistance, and thus, conventionally, anisotropic wet etching of the silicon substrate with an alkaline solution has not been adopted.

[0004]

However, in the isotropic wet etching described above, the etching proceeds not only in the depth direction of the silicon substrate but also in the lateral direction thereof, and the dimensional processing accuracy of the opening is poor. In addition to the fact that the X-ray transmission window having the size and shape described above cannot be formed with high accuracy, the above-mentioned etching solution deteriorates quickly, so that it is necessary to exchange the solution several times during the etching, which is inconvenient.

The present invention has been made in view of such a situation, and an object of the present invention is to improve the processing accuracy of an X-ray transmission window shape and to exchange an etching solution by a two-stage etching process using a different type of etching solution. An object of the present invention is to provide an X-ray mask manufacturing method capable of simplifying the process by reducing the number of times to one, and an X-ray mask manufactured by the method.

[0006]

In order to achieve the above object, an X-ray mask manufacturing method according to the present invention comprises an anisotropic etching using an alkali solution in a wet etching process for forming an X-ray transmission window. Is performed as a first step, and then a two-step etching is performed in which isotropic etching using a mixed solution of hydrofluoric acid, nitric acid, and acetic acid is performed as a second step.

That is, according to the method of manufacturing an X-ray mask of the present invention, an X-ray transparent thin film is formed on one surface of a silicon substrate,
An X-ray absorbing pattern is formed on the surface of the X-ray transmitting thin film opposite to the silicon substrate, and the X-ray absorbing pattern is formed.
In a method of manufacturing an X-ray mask for forming an X-ray transmission window including an X-ray exposure region by etching away a silicon substrate in a portion including the X-ray exposure region, a surface of the silicon substrate opposite to the X-ray transparent thin film After forming a protective film that almost covers the portion other than the X-ray exposure region on the upper portion, and removing the silicon substrate portion not covered by the protective film to an intermediate depth by anisotropic etching, the remaining portion is removed by isotropic etching. The method is characterized in that a depth portion is removed to form an X-ray transmission window including an X-ray exposure region.

In this case, it is desirable to use a carbon film as the X-ray transparent thin film. The present invention includes an X-ray mask manufactured by such a manufacturing method.

[0009]

According to the method of manufacturing an X-ray mask of the present invention,
In the step of forming the line transmission window, first, most of the silicon substrate thickness is subjected to anisotropic etching removal using an alkali solution or the like, and then the remaining silicon substrate thickness is subjected to hydrofluoric acid, nitric acid, and acetic acid. Since the isotropic etching is removed using a mixed solution or the like, the X-ray transmission window formed on the silicon substrate is mostly formed by anisotropic etching, and the size and shape thereof become highly accurate. Further, the etching solution needs to be exchanged only once from an anisotropic etching solution such as an alkaline solution to an isotropic etching solution such as a mixed solution of hydrofluoric acid, and the number of steps can be reduced. .

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing an X-ray mask according to the present invention will be described below with reference to the drawings. FIG. 1 (a)-
(G) is a schematic sectional view showing a manufacturing process of an example of a method for manufacturing an X-ray mask according to the present invention.

First, a mirror-polished thickness of 0.3 to 6.4
mm for the protective film having a thickness of 0.4 to 4 μm on the entire surface of one side of the silicon substrate 1 by a CVD method or a sputtering method.
An iN film is formed. Then, dry the over SiN film is coated with a photoresist, was formed by conventional photolithography using the resist pattern to leave a protective film on a portion other than the X-ray transmission window, using a gas such as CF ₄ The protective film 2 is formed by removing the SiN film portion corresponding to the X-ray transmission window by etching and removing the remaining resist pattern by plasma etching using oxygen gas. Needless to say, this protective film 2 may be formed after the formation of the X-ray transparent thin film 3 in the next step.

Next, as disclosed in Windishman's document mentioned in the description of the prior art, an X-ray transparent thin film is formed by a microwave plasma CVD method using a mixed gas of methane and hydrogen. 0.8 ~ 40μ thick
m, tensile stress 5 × 10 ^{8 to} 2.2 × 10 ⁹ dyn /
As shown in FIG. 1A, a carbon film 3 having a cm ² is formed on the entire surface of the silicon substrate 1 opposite to the surface on which the protective film 2 is adhered.

Next, as shown in FIG. 1 (b), an X-ray having a thickness of 0.2 to 1 μm made of tantalum, tungsten or an alloy mainly containing them is formed on the carbon film 3 by sputtering or CVD. The line absorbing material layer 4 is formed.

Next, as shown in FIG. 1C, a desired resist pattern 5 is formed by an ordinary electron beam exposure method or the like. Next, using the resist pattern 5 as a mask, C
The X-ray absorbing material layer 4 is etched by a reactive ion etching method using a gas such as F ₄ , Cl ₂ + O _2, and X
After the formation of the X-ray absorbing pattern 6, the remaining resist pattern 5 is removed by plasma etching using oxygen gas, and the X-ray absorbing pattern 6 as shown in FIG.
To form

Next, a portion of the silicon substrate 1 which is not protected by the protective film 2 is removed from the back surface by anisotropic wet etching using an alkaline solution to remove most of the entire thickness of the silicon substrate. As shown in (), a silicon substrate 7 having a desired high-precision window with a trapezoidal cross section can be formed. At the time of this etching, a jig made of an O-ring or the like is used to protect the carbon film 3 and the X-ray absorbing pattern 6.
By using an aqueous solution of 0 to 40% KOH, NaOH, or the like, good high-precision etching can be performed.

Next, a mixed solution of hydrofluoric acid, nitric acid and acetic acid (HF: HNO ₃ : CH ₃ COOH = 1: 2-3:
By performing isotropic wet etching using 1) as an etchant, the remaining silicon substrate thickness is removed, and a final X-ray including an X-ray exposure region as shown in FIG.
A line transmission window and a silicon frame 8 are formed. Since the thickness removed by this etching is very small, the shape of the high-precision window formed by the first-stage anisotropic etching is hardly deformed and is maintained at the high precision.

Finally, as shown in FIG. 1 (g), a reinforcing frame 10 made of borosilicate glass having a thickness of 2 to 10 mm and the protective film 2 are bonded via an epoxy-based adhesive layer 9, The X-ray mask is completed.

[0018]

As is clear from the above description, according to the method for manufacturing an X-ray mask of the present invention, in the step of forming an X-ray transmission window, first, most of the thickness of the silicon substrate is reduced with an alkaline solution or the like. X-ray transmission window formed in the silicon substrate to remove the remaining silicon substrate thickness isotropically with a mixed solution of hydrofluoric acid, nitric acid and acetic acid, etc. Is to be formed mostly by anisotropic etching, its dimensions,
The shape becomes highly accurate. Further, the etching solution needs to be exchanged only once from an anisotropic etching solution such as an alkaline solution to an isotropic etching solution such as a mixed solution of hydrofluoric acid, and the number of steps can be reduced. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the steps of one embodiment of a method for manufacturing an X-ray mask according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 silicon substrate 2 protective film 3 X-ray transparent thin film (carbon film) 4 X-ray absorbing material layer 5 resist pattern 6 X-ray absorbing pattern 7 silicon substrate with window 8 silicon frame 9 Adhesive layer 10 ... reinforcement frame

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-276223 (JP, A) JP-A-63-175422 (JP, A) JP-A-58-215028 (JP, A) JP-A 55- 127559 (JP, A) JP-A-64-15923 (JP, A) JP-A-4-269832 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027 G03F 1 / 16

Claims (3)

(57) [Claims] An X-ray transmissive thin film is formed on one surface of a silicon substrate, and an X-ray absorptive pattern is formed on an X-ray transmissive thin film opposite to the silicon substrate. A method of manufacturing an X-ray mask for forming an X-ray transmission window including an X-ray exposure region by etching away a portion of the silicon substrate including the X-ray exposure region. A protective film that covers almost the portion other than the X-ray exposure region is formed on the surface of the substrate, and the silicon substrate portion that is not covered by the protective film is removed to an intermediate depth by anisotropic etching, and then isotropically etched. The remaining depth is removed to remove the X-ray including the X-ray exposure area.
A method for manufacturing an X-ray mask, wherein a X-ray mask is formed. 2. The method for manufacturing an X-ray mask according to claim 1, wherein said X-ray transparent thin film is a carbon film. 3. An X-ray mask manufactured by the manufacturing method according to claim 1.