JPS63229821A - Manufacture of mask for x-ray lithography - Google Patents

Abstract

PURPOSE:To prevent a mask from being cracked or the like, by a method wherein the mask whose metal pattern is buried into a silicon oxide film in the central part of the mask is constituted completely symmetrical in order to suppress the stress strain due to a difference in the coefficient of thermal expansion at a silicon substrate, the silicon oxide film and the metal pattern. CONSTITUTION:A recessed part 13 is made down to nearly half the depth of a silicon substrate 10 and one face of the substrate including the recessed part 13 is oxidized so as to form a silicon oxide film 14; after that, groove patterns corresponding to mask patterns are made at the film 14; a metal layer composed of gold, tantalum or the like having the big X-ray absorptivity is buried into the groove patterns so as to form metal patterns 16. In succession, a poly-crystalline silicon film 17 is deposited on the surface of the recessed part containing the metal patterns 16; it is oxidized and is united with the film 14. Then, another recessed part 19 which reaches the film 14 from the other face at the corresponding part is made in the mask pattern formation region of the substrate 10; a polycrystalline silicon film 20 is deposited on the surface of the recessed part under the same condition as the film 17. Lastly, the film 20 is transformed into a silicon oxide film which is united with a silicon oxide film 15 under the same condition as in the case of the film 14; at the same time, the surface of the metal patterns is covered with silicon oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an X! The present invention relates to a method of manufacturing an a-line graphic river mask.

([l) Prior Art In recent years, advances in 1'-conductor technology are on the verge of rapid progress, and even in integrated circuits, there is a demand for a higher degree of integration, that is, miniaturization of elements. Compared to the currently commonly used photolithography, high expectations are placed on x1it lithography. As a mask used for X-ray phosphorography, for example, IEEE ELECTORON
DEVICE LE'fTER5, VOL, ELD-6
NO, 7 JULY 19g 5 P, 353 ~ (see Figure 10). In the same figure, (1) is a silicon substrate that supports a mask, and on one side of it is a base layer (3) made of a silicon nitride film. ) is formed, and a metal pattern (2) made of heavy metal such as gold, tantalum, tungsten, etc., which absorbs X-rays, is formed thereon. <4) is a photoelectron absorption film for protecting the metal pattern (2) and absorbing photoelectrons emitted from the pattern (2),
It 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, with the mask having the above structure, stress strain increases due to differences in thermal expansion coefficients between the silicon substrate (1), the base layer (3), and the photoelectron absorption layer (4), resulting in transfer There is a risk that the pattern may become distorted or the mask may crack during repeated transfer operations.

(d) Means for Solving the Problems The present invention provides for drilling a first 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; After oxidizing one surface of the substrate including this recess to grow a silicon oxide film, a groove pattern corresponding to the mask pattern is bored in the silicon oxide film,
A metal layer having a high X-ray absorption rate is buried in the groove pattern to form a metal pattern, and then a polycrystalline silicon film is deposited on the surface of the recessed part having this metal pattern, and the polycrystalline silicon film is oxidized to form the oxidized At the same time as forming a silicon oxide film integrated with the silicon film, the surface of the metal pattern is covered with a silicon oxide film, and then the silicon oxide film is reached from the other surface of the silicon substrate corresponding to the mask pattern formation region. After drilling the second recess, a second polycrystalline silicon film is deposited on the surface of the second recess under the same conditions as in the previous polycrystalline silicon film deposition process, and finally this second polycrystalline silicon film is deposited. It is oxidized under the same conditions as in the previous oxidation process to form a silicon oxide film integrated with the above-mentioned fermented silicon film, and at the same time, the surface of the above-mentioned metal pattern is oxidized with silicon oxide>J.
It is located where it overlaps with j.

(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 about 4,000 silicon oxide films (11) and (12), and then a mask pattern forming area on one surface of the substrate (10) is grown. Silicon oxide film at the relevant location (11)
There is a way to remove it by patterning.

In the second step, the silicon oxide film (11) remaining on one surface of the silicon substrate (10) is used as a mask to coat the substrate (lO
) 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 (10) in KOH mixed with a surfactant for 60 to 100 minutes.

In the third step, the silicon oxide films (11) and (12) on both the front and back surfaces of the silicon substrate (10) are removed by etching using a hydrofluoric acid-based etchant, and then the silicon substrate (10) is etched again.
) is exposed to a thermal oxidation atmosphere to grow silicon oxide films (14) and (15) with a thickness of approximately 1 μm on both the front and back surfaces of the silicon substrate (10) including the recessed portion (13) (3rd step).
In general, when a silicon substrate is thermally oxidized, distortion is unlikely to occur at the interface between the thermal oxide film formed on the surface of the substrate and the substrate, and the adhesion between the two is said to be extremely high. There is.

In the fourth step, as shown in FIG.
A groove pattern corresponding to the mask pattern is bored in the silicon oxide film (14) in the recess (13), and then a heavy metal such as gold, tantalum, or tungsten, which has a high X-ray absorption rate, is embedded in the groove pattern to form a metal pattern ( 16). The groove pattern in this process is 1
A hole is formed using a conventional photoresist technique using a photoresist film with a thickness of less than μ, and a heavy metal with a high xi absorption rate is deposited on the surface of this photoresist film, and then the photoresist film is etched. A metal pattern (16) is formed using an ablation technique.

In the fifth step, as shown in FIG.
Polycrystalline silicon (17) with a thickness of 500 to 1000 is coated on the surface of the silicon oxide film (14) on the side having the recess (13).
) at the place where you deposit. Due to this process, the metal pattern (16) within the recess (13) is naturally also covered with polycrystalline silicon (17).

In the sixth step, all of this polycrystalline silicon (17) is
in an oxidizing atmosphere at 80-1100°C for 10-20 minutes,
As a result of this fermentation process, the polycrystalline silicon (17) becomes a silicon oxide film of 800~tsoo thick (Fig. 6), but the silicon oxide film is similar to the silicon oxide film (14). to form an integrated silicon oxide (18), and the metal pattern (1) in the recess (13)
6) is buried in this integrated silicon oxide (18).

The seventh step is to remove the patterning from the silicon substrate corresponding to the mask pattern forming area in the first step.
The silicon oxide film (15) on the back surface of the silicon substrate (10) at a position symmetrical to the surface of the silicon substrate (10) is removed by patterning, and the silicon substrate (10) is selectively etched using the remaining silicon oxide film (15) as a mask to form recesses. (19) to expose the silicon oxide film (14) and the metal pattern (16) buried in the oxide film (14) from the back side (FIG. 7).

The eighth step is the silicon oxide film (10) used as a mask during the selective etching step from the back surface of the substrate (10).
5) was etched away, and then the integrated silicon oxide (1g
) Polycrystalline silicon (2
0) (Fig. 8).

Finally, in the same manner as in the sixth step, this polycrystalline silicon (20) is thermally oxidized in an oxidizing atmosphere of 980~tioo''''C, and the silicon oxide film formed as a result of this oxidation treatment is integrated with the above. It is integrated with the silicon oxide film (18), and the back surface of the metal pattern (16) is covered with this integrated graded silicon film (
18) to complete the method of the present invention (FIG. 9).

The surface of the metal pattern (16) is covered with a silicon oxide film of 800 to 1,500 layers, so photoelectrons from the surface of the metal pattern (16) are absorbed by the silicon oxide film during X-ray exposure. However, when a large number of photoelectrons are generated, it is desirable to provide a photoelectron absorption layer such as a silicon nitride film several thousand thick on both the front and back surfaces of the integrated silicon oxide film (18).

(G) Effects of the Invention The X-ray phosphorography mask obtained according to the present invention has a completely symmetrical metal pattern embedded in the integrated silicon oxide film at the center of the mask. This eliminates stress and strain caused by the difference in thermal expansion coefficient between the silicon film and metal pattern, resulting in distortion of the transferred pattern.
Unwanted accidents such as mask cracking can be prevented. Furthermore, since the surface of the metal pattern is covered with silicon oxide produced by thermal oxidation, which is extremely stable in terms of physical properties, a highly reliable mask structure can be obtained.

[Brief explanation of the drawing]

1 to 9 are cross-sectional views showing the method of the present invention in the order of steps;
FIG. 10 is a sectional view showing a conventional mask structure. (lO)...Silicon substrate, (11)(12)(14)(15)...Silicon oxide film, (13)(19)...Concavity, (16)...Metal Patterned film, (17) (20)...polycrystalline silicon, (18)...
...Integrated silicon oxide film.

Claims (2)

[Claims] (1) A method for manufacturing an X-ray lithography mask comprising the following steps: - A first recess from one surface of a silicon substrate corresponding to a mask pattern formation area to a depth of approximately 1/2 of the thickness of the substrate. - A step of oxidizing one surface of the substrate including the recess to grow a silicon oxide film. - A step of drilling a groove pattern corresponding to the mask pattern in the silicon oxide film. - Adding an X-ray absorption rate to the groove pattern. a step of embedding a large metal layer to form a metal pattern, a step of depositing a polycrystalline silicon film on at least the surface of the concave portion having the metal pattern, and a step of oxidizing the polycrystalline silicon film to integrate it with the silicon oxide film. forming a silicon oxide film, and at the same time covering the surface of the metal pattern with a silicon oxide film; - drilling a second recess that reaches the silicon oxide film from another surface of the silicon substrate at a location corresponding to the mask pattern formation region; a step of depositing a second polycrystalline silicon film on at least the surface of the second recess under the same conditions as in the previous polycrystalline silicon film deposition step; - depositing this second polycrystalline silicon film in the previous oxidation step a step of oxidizing under the same conditions as to form a silicon oxide film integrated with the silicon oxide film, and simultaneously covering the surface of the metal pattern with a silicon oxide film; The method for manufacturing an X-ray lithography mask according to claim 1, further comprising the step of: (2) providing a photoelectron absorption layer on the surface of the silicon oxide film.