JP2001203154A - Manufacturing method of mask membrane for lithography - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a mask membrane for lithography by which a diamond film can be manufactured easily without damaging smoothness and film stress, after the film is formed. SOLUTION: Fluidized diamonds particles are put into contact with a silicon substrate having underlying film formed thereon or an underlying substrate, before a diamond film is grown. Next, the diamond film is grown on the substrate or the underlying film and then the silicon substrate, and the underlying film or the underlying substrate are etched and removed to manufacture a mask membrane for lithography.

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 a mask membrane for lithography such as X-rays or electron beams.

[0002]

2. Description of the Related Art With the recent increase in accuracy and integration of semiconductor devices, there is a demand for further miniaturization of patterns formed thereon. Attention has been focused on lithography using lines. In order to form this fine pattern, an exposure apparatus is generally used in many cases. Diamond, boron nitride, silicon nitride, silicon carbide, etc. have been proposed as materials for the mask membrane to be mounted on this exposure apparatus. Among these materials, the diamond film has a Young's modulus, etching resistance, and high energy resistance. It is considered to be an excellent material as a mask membrane for X-ray or electron beam lithography because of its excellent radiation properties.

As a method for producing a film, there are known methods using a DC arc discharge, a DC glow discharge, a combustion flame, a high frequency wave, a microwave, a hot filament, and the like. Generally, the method is often performed by this method because the film can be formed with high reproducibility and high purity.

[0004] However, even if a diamond film is manufactured according to this manufacturing method, diamond nuclei are hardly generated, so that film growth may be difficult. In order to solve such a problem, a method of polishing the surface of a silicon substrate before film formation or performing ultrasonic scratching to promote generation of diamond nuclei is known, but it is flat and uniform with good reproducibility. There is a problem that surface processing cannot be performed. Furthermore, it has been proposed to apply a bias voltage to a substrate by microwave discharge to promote the generation of diamond nuclei and grow the film (S. Yugo, App.).
l. Phys. Letter, 58 (1991) 103
6), the nucleation density may not be sufficiently obtained, and a desired film thickness may not be obtained, or the film may lack uniformity.

[0005] The film is required to have excellent properties such as smoothness, mechanical strength, visible light transmittance, chemical resistance, electron beam resistance and radiation resistance.
After a diamond film is formed on a silicon substrate by a method, when the silicon substrate is removed by polishing or wet etching to produce a film, the smoothness and film stress of the film are often impaired. Not all properties have been satisfied.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is intended for a lithography method capable of easily manufacturing a film without impairing smoothness, film stress and the like after film formation. It is a main object to provide a method for manufacturing a mask membrane.

[0007]

Means for Solving the Problems The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 of the present invention comprises forming a base film on a silicon substrate, and forming the base film on the silicon substrate. By contacting the surface with diamond particles fluidized by a gas, and then growing a diamond film on the underlayer, etching away the silicon substrate and subsequently etching away the underlayer, This is a method for producing a mask membrane for lithography.

As described above, a base film is formed on a silicon substrate, diamond particles fluidized by a gas are brought into contact with the surface of the base film, and then a diamond film is grown on the base film. If a lithographic mask membrane is manufactured by etching and removing a silicon substrate and subsequently etching and removing a base film,
Since the film can be manufactured without impairing the smoothness, the film stress, and the like, an optimal diamond film can be manufactured as a mask membrane for lithography such as X-rays or electron beams.

[0009] As described in claim 2, as the underlayer film, silicon oxide, silicon nitride, silicon carbide, tungsten carbide, boron nitride, aluminum nitride, alumina, titanium oxide, zirconium oxide, tantalum (Ta),
One or more selected from ruthenium (Ru), chromium (Cr), and tungsten (W) can be mentioned. Among them, silicon oxide, silicon nitride, and silicon carbide are diamond film-forming properties, mechanical strength, and visible. It is preferable because of its excellent light transmittance. The formation of these underlayers is preferably performed on the surface of the silicon substrate by a known method such as a sputtering method or a low pressure CVD method.

According to a third aspect of the present invention, a diamond particle fluidized by a gas is brought into contact with an undersubstrate surface, and after a diamond film is grown, the substrate is etched and removed. This is a method for producing a lithographic mask membrane.

As described above, the diamond particles fluidized by the gas are brought into contact with the surface of the underlying substrate, and after the diamond film is grown, the substrate is etched and removed. Since a film can be produced without impairing the properties and film stress, a diamond film optimal as a lithographic mask membrane for X-rays or electron beams can be produced.

Further, as described in claim 4, as the base substrate, silicon oxide, silicon nitride, silicon carbide, tungsten carbide, boron nitride, aluminum nitride, alumina, titanium oxide, zirconium oxide, T
One, two or more selected from a, Ru, Cr, and W are mentioned, and among them, silicon oxide, silicon nitride, and silicon carbide are preferable.

In this case, it is preferable that the silicon substrate is etched with an alkaline aqueous solution and the underlying film or the underlying substrate is etched with an acidic aqueous solution to manufacture a lithographic mask membrane.

As described above, if the silicon substrate is etched with an alkaline aqueous solution and the underlying film or the underlying substrate is etched with an acidic aqueous solution, the film is not eroded by the alkaline aqueous solution. The film can be manufactured easily without impairing the film stress and the like.

As described above, as the base film and the base substrate, an insulating film or an insulating substrate such as silicon oxide, silicon nitride, silicon carbide, tungsten carbide, boron nitride, aluminum nitride, alumina, titanium oxide, and zirconium oxide; When one or two or more conductive films or conductive substrates such as Ru, Cr, and W are used, the underlying film and the underlying substrate can be easily removed by etching without damaging the surface of the diamond film. Therefore, the smoothness and the film stress of the obtained diamond film are not impaired.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

In the present invention, a diamond film is formed after a base film is formed on a silicon substrate, and a process for promoting generation of diamond nuclei during film formation is performed on the base film. Thereafter, the silicon substrate is removed by etching, and then the underlying film is removed by etching, thereby manufacturing a lithographic mask membrane.

Further, according to the present invention, when a diamond film is formed on a substrate and then the substrate is removed by etching to produce a mask membrane for lithography, the difference in etching rate between the diamond film and the substrate in the etching step. Utilizing lithography makes it possible to easily manufacture a lithographic mask membrane without impairing the smoothness and film stress of the diamond film.

A method of manufacturing a lithographic mask membrane by removing a substrate on which a diamond film is formed by etching will be described below with reference to FIG. First, the case where the diamond film 13 is formed on the silicon substrate 11 on which the base film 12 is formed and then the substrate is etched away will be specifically described. Diamond film 1
Base film 12 on the back surface of the substrate (FIG. 1C) on which film 3 is formed.
Is removed by etching using an acidic aqueous solution such as a hydrofluoric acid aqueous solution (FIG. 1D). Next, the silicon substrate 11 is removed by etching using an alkaline aqueous solution such as an aqueous potassium hydroxide solution at 95 ° C. until the silicon substrate 11 reaches the base film 12 (FIG. 1E).

In this case, silicon is etched with an aqueous solution of potassium hydroxide. However, since the underlying film has a low etching rate, the etching process can be easily terminated when the etching reaches the underlying film. Next, the underlying film 12 is etched away using an acidic aqueous solution such as a hydrofluoric acid aqueous solution (FIG. 1F) to obtain a membrane made of a diamond film. According to this method, the diamond film is hardly affected by hydrofluoric acid, so that the lithographic membrane can be easily manufactured without deteriorating the smoothness and the film stress.

Next, a case where a diamond film is formed on an underlying substrate and then the substrate is removed by etching will be specifically described. A predetermined region is etched away from the formed base substrate using an acidic aqueous solution such as a hydrofluoric acid aqueous solution until reaching the diamond film, whereby a membrane made of the diamond film is obtained. According to this method, an alkaline aqueous solution that is liable to attack the diamond film is not used, so that the lithographic membrane can be easily manufactured without impairing the smoothness and the film stress.

The removal by etching may be performed by a conventionally known method, for example, by immersing the substrate on which the diamond film has been formed by the above method in a bath containing an etching solution.

As described above, if a diamond film is formed on the silicon substrate on which the base film is formed or on the base substrate, the surface of the diamond film is damaged while the substrate is removed in the step of etching and removing the silicon substrate with an alkaline aqueous solution. As a result, the surface condition of the film is good, the occurrence of defective products having an uneven film thickness and insufficient film stress can be prevented, and the yield can be improved.

Next, before forming a diamond film,
The method for bringing the fluidized diamond particles into contact with the silicon substrate or the base substrate on which the base film is formed may be, for example, according to Japanese Patent Application Laid-Open No. 9-260251.

The diamond particle fluidizing apparatus 20 comprises:
A stainless steel wire mesh 23 fixed by a fixing jig 22 and a silicon substrate or a base substrate 24 on which a base film is formed are placed in a treatment layer container 21 as shown in FIG. And an inert carrier gas such as nitrogen can be introduced from below through the vial to fluidize the diamond particles 25. The fluidized diamond particles 25 are brought into contact with the substrate surface 24 so as to damage the substrate surface 24 or leave diamond particles to promote generation of diamond nuclei during film formation. .

When the diamond particles collide with the substrate in this manner, scratches and diamond particles can be uniformly and efficiently adhered to the substrate as compared with conventional polishing or ultrasonic scratching. The scratches and diamond particles promote the generation of diamond nuclei, and if a diamond film is formed on the treated substrate, the film can be easily and uniformly grown in a stacked state, so that the film thickness and the film stress are reduced. Can be made uniform.

In order to uniformly apply scratches and diamond particles on the substrate, it is desirable to keep the fluidized state constant, and it is preferable that the treatment layer container 21 be sufficiently large with respect to the substrate. For example, when processing a substrate having a diameter of 4 inches, the processing layer container is desirably formed in a cylindrical shape having an inner diameter of about 8 inches. The size of diamond particles is
It is desirable to use a diamond having a diameter of 0.1 μm to 700 μm according to the size of the substrate or the like, and the type of diamond may be either synthetic or natural.

Preferably, the fluidizing gas velocity of the diamond particles is at least five times the gas flow starting velocity, and the diamond particles are allowed to flow in the processing vessel at a constant rate opposite to the direction of gravity. Here, the gas flow start speed Umf can be calculated by equation (1) if the Archimedes number is 1.9 × 10 ⁴ or less. Umf = dp ² (ρp−ρf) G / 1650μ (1) In equation (1), dp is the diamond particle diameter, ρp is the diamond particle density, ρf is the gas fluid density, G is the gravitational acceleration, and μ is the viscosity. And the unit is a CGS unit.

If the fluidizing gas velocity of the diamond particles is less than 5 times the gas flow starting velocity, a sufficient fluidized bed may not be obtained, while if it exceeds 100 times, the fluidized bed may be destroyed. Therefore, it is preferable to set the upper limit to 100 times at least 5 times the gas flow start speed. The fluidizing gas used is preferably a gas that is easy to handle and does not cause a chemical reaction on the substrate surface, that is, an inert gas, and specific examples thereof include nitrogen and argon.

The substrate 24 placed on the stainless steel wire mesh 23 may be fixed on the wire mesh or floated. It is desirable to be installed vertically with respect to.

The density of diamond nuclei is 1 × 1
It is desirable that 0 ⁶ · mm ^-2 or more. 1 × 10 ⁶
If the number is less than the number of pieces · mm ⁻² , the thickness of the obtained membrane becomes non-uniform.

The method of forming a diamond film on the substrate may be performed by a conventionally known method. Specifically, a method using a DC arc discharge, a DC glow discharge, a combustion flame, a high frequency wave, a microwave, a hot filament, or the like is exemplified. However, the method is performed by a microwave CVD method because reproducibility is high and impurities are not mixed. It is desirable to do.

[0033]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples. A method for forming a diamond film and a method for etching and removing the formed substrate and the like with reference to FIG. 1 will be specifically described with reference to FIG. 2 for a method for generating diamond nuclei.

Example 1 First, as shown in FIG. 1A, a double-side polished silicon wafer (100) 11 having a diameter of 4 inches and a thickness of 600 μm was prepared, and the surface thereof was subjected to a low pressure CVD method. 0.5 μm thick silicon nitride film (insulating film)
12 was formed (FIG. 1B). Next, the substrate was treated with diamond particles by a diamond particle fluidizing apparatus shown in FIG. An acrylic tube having an inner diameter of 8 inches and a height of 1 m was used as a treatment layer container, and 700 g of synthetic diamond having an average particle diameter of 400 μm was used as diamond particles. A stainless steel wire mesh having a size of 40 μm was used, and nitrogen as a fluidizing gas was introduced from below through the wire mesh. The flow rate is Umf
366 cm / sec, 20 times larger than 18.3 cm / sec
c. The silicon substrate 11 on which the silicon nitride film 12 was formed was subjected to processing for 3 hours with the processing surface fixed near the center of the processing layer container so as to be perpendicular to the gas flow.

After the above treatment, a diamond film 13 was formed on the silicon substrate 11 on which the silicon nitride film 12 was formed (FIG. 1C). The diamond film was formed by the microwave CVD method described below. First, the processing substrate is placed in a chamber, and 1
Under reduced pressure conditions of 0 ^-3 Torr or less, hydrogen and methane as raw material gases were introduced at a rate of 997 cc / min and 3 cc / min, respectively. Next, after making the chamber 30 Torr, 3
A microwave of 000 W was applied to form a film for 30 hours. The substrate surface temperature at this time was 890 ° C.

The obtained diamond film 13 was a polycrystalline diamond having a thickness of 1.1 μm. The nucleation density of the diamond film 13 is 7 m from the edge of the substrate.
1.2 × 10 ⁸ · mm ^-2 , 1.5 × 10 ⁸ · mm ^-2 , 1.6 × 10 ⁸ at the positions of m, 23 mm and 39 mm, respectively
Pieces · mm ⁻² . From this, it was found that this film was extremely dense and uniform.

After masking the area other than the area of 30 mm square at the center of the back surface of the substrate (FIG. 1C) on which the diamond film has been formed, a base film 12 is formed with a hydrofluoric acid aqueous solution.
Was partially removed by etching (FIG. 1D). Next, 9
The silicon substrate 11 was removed by etching with a 5 ° C. aqueous solution of potassium hydroxide until the silicon substrate 11 reached the base film 12 (FIG. 1).
(E)). In this case, silicon is etched with an aqueous solution of potassium hydroxide, but since silicon nitride has a low etching rate, the etching process can be easily terminated when the etching reaches the silicon nitride film. next,
Subsequently, the underlying film 12 was removed by etching with a hydrofluoric acid aqueous solution (FIG. 1F) to obtain a membrane made of a diamond film. In this case, the diamond film is hardly affected by the hydrofluoric acid aqueous solution. Therefore, the membrane was not corroded by the alkaline aqueous solution and was excellent in uniformity.

Example 2 An undersubstrate made of silicon nitride having a diameter of 4 inches and a thickness of 600 μm (insulating substrate)
After subjecting the diamond particles to a fluidization treatment under the same conditions as in Example 1 except that the thickness was changed to 1, a diamond film was formed on the substrate by microwave CVD to obtain a polycrystalline film having a thickness of 1.2 μm. I got a diamond. This diamond film has a nucleation density of 7 mm
1.6 × 10 ⁸ pieces · mm at 3 mm and 39 mm positions
^-2 , 2.0 × 10 ⁸ pieces ・ mm ^-2 , 2.0 × 10 ⁸ pieces ・ m
m ^-2 . From this, it was found that this film was extremely dense and uniform.

After a masking treatment was performed on the area other than the area of 30 mm square at the center of the back surface of the formed substrate with a resin film, the base substrate was etched and removed with a hydrofluoric acid aqueous solution until reaching the diamond film, thereby obtaining a membrane made of a diamond film. .
The obtained membrane did not show corrosion by the etching solution, and was excellent in uniformity.

COMPARATIVE EXAMPLE 1 A double-side polished silicon wafer (100) having a diameter of 4 inches and a thickness of 600 μm was prepared in the same manner as in Example 1 except that a silicon nitride film was not formed. The diamond particles were fluidized and a diamond film was formed. The obtained diamond film was a polycrystalline diamond having a thickness of 1.5 μm. The nucleation density of this diamond film was 2.5 × at 7 mm, 23 mm, and 39 mm from the edge of the substrate.
10 ⁸ · mm ^-2 , 3.1 × 10 ⁸ / mm ^-2 , 3.4
× 10 ⁸ · mm ^-2 . From this, it was found that this film was extremely dense and uniform.

After a masking process was performed on a portion of the substrate on which the film was formed, except for a region 30 mm square at the center of the back surface of the substrate, at 95 ° C.
The silicon substrate was removed by etching with an aqueous potassium hydroxide solution to obtain a membrane composed of a diamond film. On the etched surface of the obtained membrane, many point corrosions occurred, and it was seemingly non-uniform at first glance.

(Comparative Example 2) 4 inches in diameter and 600 in thickness
A double-sided polished silicon wafer (100) of μm was subjected to ultrasonic vibration for 40 minutes in hexane in which synthetic diamond particles having an average particle size of 1 μm were dispersed.

A diamond film was formed on the surface-treated substrate in the same manner as in Example 1. The obtained diamond film was a polycrystalline diamond having a thickness of 1.0 μm. The nucleation density of the diamond film was 6.2 × 1 at 7 mm, 23 mm, and 39 mm from the edge of the substrate.
0 ³ · mm ^-2, 9.2 × 10 ³ cells · mm ^-2, 8.5 ×
The density was extremely low at 10 ³ · mm ^-2 and non-uniform. After masking the area other than the area of 30 mm square at the center of the back surface of the formed substrate, the silicon substrate was removed by etching with a 95 ° C. aqueous solution of potassium hydroxide to obtain a membrane made of a diamond film. The etched surface of the obtained membrane had many spot corrosions, and was seemingly non-uniform at first glance.

The present invention is not limited to the above embodiment. The above embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the claims of the present invention. Within the technical scope of

[0045]

According to the present invention, it is possible to manufacture a mask membrane for X-ray or electron beam lithography without impairing the smoothness and film stress after film formation.

[Brief description of the drawings]

1 (a) to 1 (f) show a manufacturing process of a lithographic mask membrane according to the present invention.

FIG. 2 is a schematic diagram of a diamond particle fluidizing treatment apparatus according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Silicon substrate, 12 ... Base film (silicon nitride film), 13 ... Diamond film, 20 ... Diamond particle fluidization processing apparatus, 21 ... Processing layer container, 22 ... Fixed Jig, 23 ...
Stainless steel wire mesh, 24 ... substrate, 25 ... diamond particles.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/205 H01L 21/30 531M 21/306 541S 21/306 B (72) Inventor Yoshihiro Kubota Yasu Gunma 2-13-1 Nakabe Isobe Shin-Etsu Chemical Industry Co., Ltd. Precision Functional Materials Research Laboratory (72) Inventor Ikuo Okada 2-1-1 Nishishinjuku, Shinjuku-ku, Tokyo NTT Advanced Technology Corporation In company

Claims (5)

[Claims] An underlying film is formed on a silicon substrate, diamond particles fluidized by a gas are brought into contact with the surface of the underlying film, and a diamond film is grown on the underlying film. A mask membrane for lithography by etching and removing the underlying film. 2. The method according to claim 1, wherein the base film is made of silicon oxide, silicon nitride, silicon carbide, tungsten carbide, boron nitride, aluminum nitride, alumina, titanium oxide, zirconium oxide, tantalum (Ta), ruthenium (Ru), chromium (Cr). 2. The method according to claim 1, comprising one or more of tungsten, tungsten (W). 3. A method for producing a mask membrane for lithography by bringing diamond particles fluidized by a gas into contact with an undersubstrate surface, growing a diamond film, and then etching and removing the substrate. . 4. The undersubstrate is one selected from silicon oxide, silicon nitride, silicon carbide, tungsten carbide, boron nitride, aluminum nitride, alumina, titanium oxide, zirconium oxide, Ta, Ru, Cr, W or The method according to claim 3, wherein the method comprises two or more types. 5. The method according to claim 1, wherein the etching of the silicon substrate is performed with an alkaline aqueous solution, and the etching of the base film or the base substrate is performed with an acidic aqueous solution. .