JPS63136518A - Manufacture of x-ray mask - Google Patents

Abstract

PURPOSE:To realize a high flatness and improve patterning accuracy of an X-ray mask by preparing a high X-ray transmissivity and a wafer of high melting point, forming a trench in the wafer, and forming an X-ray absorber pattern by casting a heavy metal of low melting point having a high X-ray absorptance into the trench. CONSTITUTION:A boron nitride wafer 40 of a high flatness is formed by baking and polishing ultrafine powder boron nitride. With an EB resist pattern 41 as a mask the wafer 40 is trench-etched by a CF gas. An Au film 43 is formed by a vacuum deposition method on the whole surface. This is heat treated at Au melting point temperature or higher, the film 43 is filled in a trench 42, and the deposited film 43 is flattened. Only the Au film on the surface of the wafer 40 except the trench is removed by sputter-etching with Ar gas. A polyimide film 44 is formed on the wafer formed with the Au pattern. The wafer 40 is back etched to be reduced in thickness. Thus, a high flatness X-ray mask is obtained.

Description

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

(Prior Art) X-rays with short wavelengths have come to be used for exposure. This principle involves exposing and developing an X-ray resist with X-rays of a different wavelength, and its features include no diffraction or interference (and excellent formation of fine patterns).

Conventionally, technologies in this field include (1) monthly publications;
Semiconductor World, 1986. IVol, 5
．． No, 1. P, 74-81 (2) JPN, J, AP
PL, PllYS, VOL, 19 (1980), No.
11. P2321-2312 f lligh-! ? e
Solution Th1ck Mask Patte
rnFabrication for X-Ray L
ithography J(3) 5PIE Vol.
471+Electron-Beam, X-Ray, a
nd Ion-Beam Techniques for
r Submicrometer Lithograph
ies III (1984) P, 96-102.

Hereinafter, the method of manufacturing an X-ray mask shown in these documents will be explained with reference to FIGS. 2 to 4.

[1] Plating method First, as shown in FIG. 2(a), silicon (St
) Sequential sandwich on wafer 1 (Si*N*/5I
o2/s+zN4) structure mask substrate 2, Au film as base metal for plating (100-layer evaporation) 3,
A polyimide film 4, a Ti film, and an εB (electron beam) resist 8 are formed.

Next, as shown in FIG. 2(b), the EB resist 8
is exposed and developed to form an EB resist pattern, and then a Ti pattern 5' is formed based on the EB resist pattern.

Next, as shown in FIG. 2(c), the Ti pattern 5
' Based on oxygen reactive ion etching (0□RI
A polyimide film pattern 4' is formed by E).

Next, as shown in FIG. 2(d), Au metal coating is applied.

Next, as shown in FIG. 2(e), the polyimide film pattern 4' is removed.

Next, as shown in FIG. 2(r), the base metal ^UUC2 is etched.

Finally, as shown in FIG. 2(g), the St wafer l
Back etching is performed to form a Si support frame 1'.

[2] Lift-off method First, as shown in FIG. 3(a), a resist 12 is coated on the X-ray mask support film ll. Next, see Figure 3 (
b), then exposed as shown in Fig. 3(C).
As shown in FIG. 2, the resist is developed to form a resist pattern 12'. Next, as shown in FIG. 3(d), after depositing Au, as shown in FIG. 3(e), the resist pattern 12' is removed together with the unnecessary Au deposited thereon. An Au pattern 13 as an XyA absorber is formed.

[3] Etching method First, as shown in FIG. 4(a), a Si wafer 20
A boron nitride (BN) film 21 with high X-ray transmittance is placed on top.
4 to 5 μm is deposited by PCVD, and 2 μm of polyimide resin 22 is applied on top of it, and Ta (300 people) 23 / Au (6000 people) 2 as an
4/Ta (800 people) 25 films are formed, and an EB resist 26 is further provided thereon.

Next, the EB resist 26 is exposed and developed, as shown in FIG.
Pattern the IER resist 26 as shown in b).

Next, the Ta (800 people) film 25 is plasma etched, and the Ta film 2 is etched with Au (6000 people) I! in an argon air plasma atmosphere. The Au pattern 24' acts as a mask for the sputter etching of 124 and serves as an X-ray absorber, as shown in FIG. 4(c).
is formed.

In addition, as a method for producing a membrane film with high X-ray transmittance, a thin film of BN, Si*Na, etc. is usually formed in a thickness of 2 to 11 μm by CVD, sputtering, etc. on a convex Si wafer plate.
A widely used method is to form a thick film and then remove this St wafer substrate using KOI+, etc., but CVD
Due to the conditions of
As shown in No. 74, a method has been adopted in which a thick boron nitride is made and a membrane film is formed by performing a bank etching process.

(Problems to be Solved by the Invention) However, the above conventional method has the following drawbacks.

(1) Disadvantages of the etching method-a, as shown in Figure 5, the etched A
A formed on the membrane film 31 due to the re-deposition of u.
The u pattern 32 becomes mesa-shaped, resulting in poor contrast accuracy.

(2) Disadvantages of plating method If there is dust, only that part will not be plated and pinholes will occur. Furthermore, the film thickness is different between the center of the wafer and the periphery of the wafer. Furthermore, as shown in FIG. 6, the film thickness 11 of the large pattern 33 and the thickness β2 of the small pattern 34 are
The pattern film thickness is different.

- There is a relationship of fi, > 1.2.

(3) Disadvantages of the lift-off method When a fine pattern is formed, as shown in FIG. 7, it is difficult for the Au 37 to enter the grooves between the transparent film patterns 36 formed on the membrane film 35.

Therefore, when the resist is removed, all of the Au37 is also removed. Also, if you melt Au37, will it also resist? It will be contained.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing an X-ray mask that eliminates the above-mentioned problems, has high flatness, and can improve patterning accuracy.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a method for manufacturing an X-ray mask in which a wafer with high X-ray transmittance and a high melting point is prepared, and the wafer is trench
: A narrow but deep trench) is formed, and a high
An X-ray absorber pattern is formed by pouring a heavy metal with a high radiation absorption rate and a low melting point.

(Function) According to the present invention, boron nitride, which has a low thermal expansion, is used as a wafer, a trench is formed in the boron nitride wafer by reactive ion etching (RIE), and a heavy metal serving as an X-ray absorber is formed in the trench. For example, Au, Pb
Since it is embedded, a high-flatness X-ray mask can be obtained and its manufacture is easy. In addition, heat flow into the trenches of high melting point wafers, such as boron nitride wafers, can cause Aul! Since it is filled with J, Au
There is almost no pattern stress. Furthermore, by arbitrarily controlling the shape of the trench, it is possible to form an X-cotton collection pattern with an arbitrary cross-sectional shape.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of the manufacturing process showing the method of manufacturing the X'bA mask of the present invention.

First, as shown in FIG. 1(a), a boron nitride wafer 40 having a high flatness is prepared by baking and polishing ultrafine boron nitride (BN) powder.

Next, as shown in FIG. 1(b), an EB resist pattern 41 having a thickness of 0.5 to 1.0 μm is formed on this boron nitride wafer 40.

Next, as shown in FIG. 1(c), using this EB resist pattern 41 as a mask, trench etching is performed on the boron nitride wafer 40 using a CF-based gas. form 42. In this etching, anisotropic etching is performed, the cross-sectional shape is rectangular, and the depth is required to be 0.5 μm or more. In this case, it is desirable to perform etching at a high power of 200 to 400 W and under a high vacuum of 5 to 10 mL, for example.

Next, as shown in FIG. 1(d), an Au film 3 is formed to a thickness of 1.0 μm over the entire surface by vacuum evaporation.

Next, as shown in FIG. 1(e), this is heat-treated at a temperature higher than the melting point temperature of Au (1064° C.) to fill the trench 42 with the vapor-deposited Au film 3 and remove the vapor-deposited Au film 3. The film 3 is planarized. At this time, since boron nitride has a melting point temperature of 3000° C. or higher, the shape of the trench does not deteriorate due to heating.

Next, as shown in FIG. 1(f), only the Au film on the surface of the boron nitride wafer 40 other than the trench portion is removed by sputter etching using Ar gas. This Au
In the sputter etching of the film using Ar, since the ^U on the surface of the boron nitride wafer 40 is more easily sputtered than the Au film in the trench 42, a good Au pattern can be formed.

Next, as shown in FIG. 1(g), polyimide for reinforcing the boron nitride wafer was spin-coated on the boron nitride wafer on which the Au pattern was formed, and a beta test was performed for 2 to 3 seconds.
A polyimide film 44 having a thickness of μm is formed.

Next, as shown in FIG. 1(h), back etching of the boron nitride wafer 40 is performed using a CF-based gas from the back side of the boron nitride wafer 40 where there is no Au pattern.
An X-ray mask is obtained by thinning the boron nitride wafer 40.

Above, we have explained the case where a trench is formed on a boron nitride wafer and the Au film is thermally melted. However, even if the wafer is not a boron nitride wafer, it can be made of a material with a high melting point and high X-ray transparency, such as graphite. , a wafer of silicon or the like. Further, as the X-ray absorber, a heavy metal such as PB, which has a low X-ray transmittance and a low melting point, may be used both outside and outside the Au film.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

(Effects of the Invention) As described above in detail, according to the present invention, the following effects can be achieved.

(1) High flatness XN, 4% mask can be obtained,
Moreover, its manufacture is easy.

(2) Since the trench of a high melting point wafer, for example a boron nitride wafer, is filled with an Au film by thermal flow, there is almost no stress on the Au pattern.

(3) By arbitrarily controlling the trench shape, an X-ray absorber pattern with an arbitrary cross-sectional shape can be formed.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the manufacturing process showing the method for manufacturing an X-ray mask according to the present invention, Figure 2 is a cross-sectional view of the manufacturing process showing the method of manufacturing an X-ray mask using a conventional plating method, and Figure 3 is a cross-sectional view of the manufacturing process showing the method of manufacturing an X-ray mask using a conventional plating method. FIG. 4 is a cross-sectional view of the manufacturing process showing a method of manufacturing an X-ray mask using the conventional etching method, and FIGS. 5 to 7 are cross-sectional views of the manufacturing process of the conventional etching method. It is a problem explanatory diagram. 40... Boron nitride wafer, 41... EB resist pine, 42... Trench, 43... Au film, 4
4...Polyimide film.

Claims (3)

[Claims] (1) (a) Prepare a wafer with high X-ray transmittance and high melting point, (b) Form a trench in the wafer, (c) Form a trench in the trench with high X-ray absorption rate and low melting point. A method for manufacturing an X-ray mask, which comprises forming an X-ray absorber pattern by pouring a heavy metal at a melting point. (2) The method for manufacturing an X-ray mask according to claim 1, wherein the wafer is made of boron nitride, graphite, or silicon. (3) The method for manufacturing an X-ray mask according to claim 1, wherein Au or Pb is used as the heavy metal.