JPS63232426A - Manufacture of mask for x-ray lithography - Google Patents

Abstract

PURPOSE:To remove the generation of stress-strain due to the difference of the thermal expansion coefficients of an silicon substrate and base layers by boring recessed sections from both the surface and rear of the silicon substrate, depositing silicon nitride films from each recessed section and using the silicon nitride films as the base layers. CONSTITUTION:A recessed section 13 corresponding to a mask-pattern forming region is bored to one surface of an silicon substrate 10, silicon oxide films 11, 12 on both the surface and rear of the substrate 10 are removed, and an silicon nitride film 14 is deposited on one surface side of the substrate 10 with the recessed section 13. Silicon oxide films 15, 16 are deposited on both the surface and rear of the silicon substrate 10, and approximately half the thickness of the silicon substrate 10 is etched, using the silicon oxide film 16 as a mask and a recessed section 17 reaching the silicon nitride film 14 is bored. The silicon oxide films 15, 16 on both surfaces of the substrate 10 are gotten rid of, and silicon nitride is deposited on another surface of the silicon substrate 10 to which the recessed section 17 is shaped, and unified with the silicon nitride film 14, thus forming a base layer 18. The mask acquired has surface-rear symmetric structure, and the strain of a pattern and the cracking of the mask are taken off.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for manufacturing an X-ray lithography mask used in the semiconductor industry.

(B) Prior art In recent years, semiconductor technology has made remarkable progress, and even in integrated circuits, higher integration density, that is, miniaturization of elements, is required. Among the currently commonly used photolithography methods, expectations are placed on xi lithography. Examples of masks used in X-ray lithography include IEEE ELECTORON DEVICE LET
TER5゜VOL, ELD-6NO, 7JULY 19
85 P, 353~ (see Figure 8), in the figure, (1) is a silicon substrate that supports the mask;
A base layer (3) made of a silicon nitride film is formed on one side, and on top of that a base layer (3) of a heavy metal such as Au%
A metal pattern (2) made of a line-absorbing material is formed. (4) protects this metal pattern (2) and
This is a photoelectron absorption film for absorbing photoelectrons emitted from the pattern (2), and is made of a silicon oxide film, a silicon nitride film, a polyimide resin film, or the like.

(c) Problems to be solved by the invention However, in a mask with such a structure, stress strain increases due to the difference in thermal expansion coefficient between the silicon substrate (1) and the base layer (3), causing distortion in the transferred pattern. , there is a risk that mask cracking may occur during repeated transfer operations.

(D) Means for Solving the Problems The present invention involves drilling a recess from one surface of a silicon substrate corresponding to a mask pattern forming area to a depth of approximately 1/2 of the thickness of the substrate, and After depositing a silicon nitride film on one surface of the silicon substrate, a recess extending to the silicon nitride film from the other surface of the silicon substrate corresponding to the mask pattern formation area is bored, and a silicon nitride film including the recess is deposited. Silicon nitride is deposited on the back surface of the substrate and integrated with the silicon nitride film obtained in the previous step to form a base layer, and finally a metal pattern made of a metal with high X-ray absorption rate is formed on the base layer. be.

(E) Function Since the mask obtained according to the present invention has a symmetrical structure on the front and back sides, pattern distortion and mask cracking are eliminated.

(f) Example In the first step of the present invention, as shown in FIG.
Both the front and back surfaces of a 0μ silicon substrate (10) are oxidized to grow silicon oxide films (11) and (12) with a thickness of about 4000 μm, and then a mask pattern forming area is formed on the -surface of the substrate (10). Silicon oxide film at locations corresponding to (11)
There is a part where buttering is removed.

In the second step, the silicon oxide film (11) remaining on the -surface of the silicon substrate (10) is used as a mask.
) is selectively removed to approximately half its thickness and a recess (13) corresponding to the mask pattern forming area is bored (
(FIG. 2), this etching step is carried out by dipping the substrate (IO) in KOH containing a surfactant for 60-100 minutes.

In the third step, as shown in FIG. 3, the silicon oxide films (11) and (12) on both the front and back surfaces of the substrate (IO) are etched away using a hydrofluoric acid-based etchant, and then the recesses (13) are etched away.
substrate (lO) with silicon nitride film (14
) is deposited.

In the fourth step, about 30% of the silicon substrate (10) is coated with
A silicon oxide film (15) (16) with a thickness of 1 μm is deposited by plasma CVD for 0 minutes, and then a silicon oxide film (16) is deposited on the other surface of the substrate (10) at a location corresponding to the mask pattern formation region. This is where the buttering is removed (Figure 4).

In the fifth step, the silicon oxide film (16) remaining from this patterning process is used as a mask to form a silicon substrate (
10) is selectively removed under the same etching conditions as in the second step to form a recess (17) that reaches the silicon nitride film (14) (FIG. 5).

In the sixth step, the silicon oxide films (15) (16) present on both surfaces of the silicon substrate (1O) are removed by etching using a hydrofluoric acid-based etchant, and then the four parts (11) and (11) of the full IFA (1) are etched. P-F No. 11 "Con Black" 110) After depositing silicon nitride on the back side of the rice cake under the same conditions as the third process, annealing treatment was performed at 600 to 800°C for 30 minutes, followed by the previous process. Silicon nitride film (14
) to form the base layer (18) of the mask pattern (Fig. 6).

In the final step of the present invention, as shown in FIG. 7, the surface of the base layer (18) obtained in the sixth step is
Metal pattern made of heavy metal with high linear absorption rate (19)
is formed using lift-off technology.

When performing X-ray exposure using the mask thus obtained, in order to avoid the influence of photoelectrons from the metal pattern (19), the X-rays are irradiated from the metal pattern (19) side.
It is necessary to consider that the substrate to be exposed is always placed on the side where the metal pattern (19) is not present.

(G) Effects of the Invention As is clear from the above description, the present invention provides a base layer by drilling four parts of a silicon substrate from both the front and back sides, depositing a silicon nitride film from each of the four parts, and forming a metal pattern on the base layer. As a result, the structure of the mask becomes symmetrical between the front and back, eliminating the stress and distortion caused by the difference in thermal expansion coefficient between the silicon substrate and the base layer, and distortion of the transferred pattern.
Unwanted accidents such as mask cracking can be prevented.

[Brief explanation of the drawing]

FIGS. 1 to 7 are cross-sectional views showing the method of the present invention in the order of steps;
FIG. 8 is a sectional view showing the structure of a conventional mask. (10)... Silicon substrate, (11) (12) (15) (16)... Silicon oxide film, (13) (17)... Concavity, (14)...
・Silicon nitride film, (18)...Base layer, (1
9)...Metal pattern.

Claims (1)

[Claims] (1) A method for manufacturing an X-ray lithography mask comprising the following steps: - Step of drilling a recess from one surface of a silicon substrate corresponding to the mask pattern formation area to a depth of approximately 1/2 of the thickness of the substrate. - Depositing a silicon nitride film on one surface of the silicon substrate, including the recess; - Drilling a recess reaching the silicon nitride film from the other surface of the silicon substrate corresponding to the mask pattern formation region;・A step of depositing silicon nitride on the back surface of the silicon substrate, including the recessed portion, and integrating it with the silicon nitride film obtained in the previous step to form a base layer. ・A metal with high X-ray absorption rate is placed on the base layer. The process of forming a metal pattern consisting of