JP3317960B2 - Method for producing diamond film for lithography - 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 for producing a diamond film for lithography such as X-ray or electron beam.

[0002]

2. Description of the Related Art With the recent increase in precision and integration of semiconductor devices, there is a demand for further miniaturization of patterns formed thereon. Attention has been paid to lithography using electron beams. 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 the material of the mask membrane to be mounted on this exposure apparatus,
Among these materials, the diamond film is excellent in Young's modulus, etching resistance, high energy ray irradiation resistance, etc.
It is considered to be the most suitable material for a mask membrane for X-ray or electron beam lithography.

By the way, in order to minimize the adverse effects due to X-ray or electron beam absorption, it is necessary that the membrane be a self-supporting film having a thickness of 0.1 to 5 μm. And the tensile stress of the film is 0.1 to 5.0.
It must be × 10 ⁹ dyn / cm ² .

In order to obtain a film having such a tensile stress, it is known that when a diamond film is formed by a microwave CVD method, the film may be formed by increasing the methane concentration as a source gas. However, under these conditions, although sufficient tensile stress of the film can be obtained, the crystallinity of the film is liable to decrease. Therefore, when the film is formed by lowering the methane concentration in the raw material gas, the crystallinity becomes better, but the tensile stress of the film is reduced and the film has a compressive stress and cannot be formed as a self-supporting film. I will. As described above, it is extremely difficult to manufacture a film that simultaneously satisfies the crystallinity and the film stress characteristics, which are the basic physical properties of a diamond film. That fits.

Further, after a diamond film is formed on a silicon substrate by the microwave CVD method, the substrate is removed by polishing or wet etching to produce a film. Etc. are often impaired.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and provides a diamond film having high crystallinity and a desired film stress on a substrate. An object of the present invention is to provide a method of manufacturing a diamond film for lithography, which can easily manufacture a film without impairing smoothness, film stress, and the like.

[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 the entire surface of a silicon substrate, after methane on one surface of the lower Chimaku, a mixed gas of hydrogen gas and oxygen gas were deposited diamond film as a material gas, a part of the back surface of the base film is removed by etching, etching of the silicon substrate This is a method of manufacturing a diamond film for lithography by removing the base film by etching.

As described above, a base film is formed on a silicon substrate, and a diamond film is formed on the base film using a mixed gas of methane gas, hydrogen gas and oxygen gas as a source gas, and then the silicon substrate is etched. If the diamond film for lithography is manufactured by removing the base film by etching and subsequently removing the base film, the film can be manufactured without impairing the smoothness and the film stress.
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 excellent in light transmittance and the like, and is preferable. The formation of these base films can be performed by a known method such as a sputtering method or a low pressure CVD method.

The present invention also provides a diamond film for lithography by forming a diamond film on a base substrate using a mixed gas of methane gas, hydrogen gas and oxygen gas as a source gas, and etching the substrate to remove it. It is a method of manufacturing.

As described above, a diamond film is formed on a base substrate by using a mixed gas of methane gas, hydrogen gas and oxygen gas as a raw material gas, and then the substrate is removed by etching. 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 the base substrate, one or more selected from silicon oxide, silicon nitride, silicon carbide, tungsten carbide, boron nitride, aluminum nitride, alumina, titanium oxide, zirconium oxide, Ta, Ru, Cr, W or Among them, two or more kinds are mentioned, and among them, silicon oxide, silicon nitride and silicon carbide are preferable.

[0013] In this case, as described in claim 3, with an aqueous alkaline solution etching of the silicon substrate, it was decided to produce a diamond film for lithography etching of the underlying film or base substrate performed in acidic aqueous solution.

As described above, if 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, the substrate and the base film can be reliably removed by etching, and the diamond film can be formed with the alkaline aqueous solution. Since there is no erosion, the diamond film can be easily manufactured without deteriorating the smoothness and the film stress.

As described above, as the base film and the base substrate, silicon oxide, silicon nitride, silicon carbide, tungsten carbide, boron nitride, aluminum nitride, alumina, titanium oxide, zirconium oxide, Ta, Ru, Cr,
If one or more materials selected from W are used, the underlying film and the underlying substrate can be easily removed by etching without damaging the diamond film. There is no loss.

In the invention according to claim 4 of the present invention, the mixing ratio of the raw material gas is such that the methane gas amount is 0.1% by volume or more and 20% by volume or less, and the hydrogen gas amount is 70% by volume or more and 99.89%. The diamond film was formed using a raw material gas having a volume% or less and an oxygen gas amount of 0.01 to 10 volume%.

As described above, the mixing ratio of the source gases is such that the methane gas amount is 0.1% by volume to 20% by volume, the hydrogen gas amount is 70% by volume to 99.89% by volume, and the oxygen gas amount is 0.1% by volume. By using a raw material gas having a volume ratio of not less than 01% by volume and not more than 10% by volume, it is possible to produce a diamond film having a high crystallinity and a high tensile stress while reliably maintaining a high crystallinity under a dilute condition in which methane gas is diluted with hydrogen gas. can do.

[0018] In this case, as described in claim 5, the deposition of diamond films by microwave CVD method or a thermal filament CVD method is preferably carried out the surface temperature of the substrate as 700 ° C. to 1200 ° C..

As described above, the diamond film is formed by the microwave CVD method or the hot filament CVD method.
If the surface temperature of the substrate is set to 700 ° C. to 1200 ° C., the control of the tensile stress of the film becomes easy, so that the desired tensile stress can be reliably obtained without impairing the crystallinity. A diamond film suitable for lithography can be manufactured.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments. The inventors of the present invention can form a diamond film having high crystallinity and a desired film stress on a substrate, and in order to manufacture a diamond film without impairing smoothness or film stress after film formation, The present invention has been completed by forming a diamond film on a substrate using a mixed gas of methane gas, hydrogen gas and oxygen gas as a source gas, and then etching and removing the substrate. As the film forming method, a microwave CVD method, a hot filament C
VD method, DC arc discharge method, DC glow discharge method, high frequency heating method, etc.
And the hot filament CVD method are preferred.

FIG. 1 shows a microwave C used for forming a diamond film on a substrate in the present invention.
It is an example of a VD device. FIG. 2 shows an example of a manufacturing process of a diamond film for lithography according to the present invention.

According to the present invention, a base film is formed on a silicon substrate, a diamond film is formed on the base film using a mixed gas of methane gas, hydrogen gas and oxygen gas as a source gas, and then the silicon substrate is removed from the back surface. Etching away
This is a method of manufacturing a diamond film for lithography by removing the underlying film by etching.

First, a method of forming a diamond film by a microwave CVD method will be described with reference to FIG. In FIG. 1, a microwave CVD apparatus 10 has a substrate table 15 on which a heating element 14 such as a heater is mounted in a chamber 13 having a gas introduction pipe 11 and a gas exhaust pipe 12. The microwave power supply 17 is connected to a microwave introduction window by a waveguide 19 so that plasma can be generated in the chamber 13.

With such a device, microwave CV
The diamond film is formed by the method D as follows. After the substrate 16 to be subjected to the formation of the diamond film is placed on the substrate table 15, the inside of the chamber 13 is evacuated to 10 ⁻³ Torr or less by a rotary pump. Next, a mixed gas composed of methane gas, hydrogen gas and oxygen gas at a desired flow rate is supplied from the gas introduction pipe 11. Next, the inside of the chamber 13 was adjusted to 3 by adjusting the valve of the gas exhaust pipe 12.
After the pressure is reduced to 0 Torr, a microwave is applied to the introduced gas to generate plasma in the chamber 13 to form a diamond film on the substrate 16. Before forming the film, the surface of the substrate may be treated with diamond particles or the like in order to facilitate generation of diamond nuclei. The method may be, for example, according to Japanese Patent Application Laid-Open No. 9-260251.

The reaction gas introduced into the chamber 13 is a mixed gas composed of methane gas, hydrogen gas and oxygen gas.
0 volume% or less, hydrogen gas amount is 70 volume% or more and 99.89
Volume% or less, and the oxygen gas amount is preferably 0.01 volume% or more and 10 volume% or less.
No. 0494 may be followed. With such a volume ratio, a diamond film having sufficient crystallinity and tensile stress can be formed. The preferred ranges are a methane gas amount of 1 vol% to 10 vol%, a hydrogen gas amount of 85 vol% to 98.9 vol%, and an oxygen gas amount of 0.1 vol% to 5 vol%.
% By volume or less. Within this range, it is possible to manufacture a diamond film having a high tensile stress while reliably maintaining high crystallinity.

In this case, if it is desired to apply a required amount of tensile stress to the diamond film, the heating element 14
The substrate 16 on which the diamond film is to be formed is heated, and the temperature is controlled to manufacture the diamond film. In addition, as the heating element 14, a sintered SiC heater or a CVD-SiC heater is specifically mentioned.

Here, the tensile stress of the diamond film is
0.1-5.0 × 10⁹ dyn / cm ^Two The range of
Is more preferable, and a more preferable range is 0.3 to 3.0 × 1.
0⁹ dyn / cm^Two It is. And the film thickness at this time is
0.1 to 5.0 μm, especially 0.2 to 3.0 μm
Is desirable. Diamond film thickness and tensile stress
If it is within the range, it can be formed on a self-supporting film and X-ray or
Use as a lithography membrane for sagittal wires
Can be.

If the surface temperature of the substrate on which the diamond film is to be formed exceeds 1200.degree. C., the crystallinity of the film may be reduced, so that the temperature is preferably set to 700.degree. If the film is formed within this temperature range, the film stress can be easily adjusted without losing the crystallinity. Note that the temperature can be set in this range by controlling the power of the applied microwave. However, in this case, the physical properties of the diamond film to be deposited may become unstable. It is preferable to control the temperature together with the heating element 14 for performing the temperature control. By adjusting the substrate temperature at the time of film formation with the heater 14 within the above range, physical properties such as stress of the diamond film can be controlled to desired values.

Next, a method for obtaining a membrane by forming a diamond film on a substrate by the microwave CVD method and then removing the substrate by etching will be described with reference to FIG. First, a diamond film 23 is formed on the silicon substrate 21 on which the base film 22 is formed by the above-described method (FIG. 2).
(See (a) to (c)).

Next, a predetermined area from the back surface of the substrate (FIG. 2C) on which the diamond film 23 has been formed is partially etched away using an acidic aqueous solution such as a hydrofluoric acid aqueous solution (FIG. 2C). 2 (d)). Next, the silicon substrate 21 is removed by etching with an alkaline aqueous solution such as a 95 ° C. aqueous solution of potassium hydroxide until the silicon substrate 21 reaches the base film 22 (FIG. 2).
(E)). In this case, the silicon substrate 21 is etched with an aqueous solution of potassium hydroxide. However, since the base film 22 has a low etching rate, the etching process can be easily terminated when the etching reaches the base film. next,
Subsequently, the base film 2 is formed using an acidic aqueous solution such as a hydrofluoric acid aqueous solution.
2 is removed by etching (FIG. 2F) to obtain a diamond film for lithography. According to this method, since the diamond film is hardly affected by hydrofluoric acid, a membrane for X-ray or electron beam lithography can be easily manufactured without impairing the smoothness and the film stress.

Next, the case where a diamond film is formed on an underlying substrate and then the substrate is removed by etching will be specifically described. First, a diamond film is formed on an underlying substrate in the same manner as described above. Then, a predetermined region on the back surface of the formed base substrate is etched away using an acidic aqueous solution such as a hydrofluoric acid solution until the base substrate reaches the diamond film, thereby obtaining a diamond film for lithography. According to this method, a diamond film for lithography such as an X-ray or an electron beam can be easily manufactured without impairing smoothness and film stress without using an alkaline aqueous solution that is liable to attack the diamond film. .

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

Here, the substrate on which the diamond film is formed is a substrate in which a base film is formed on silicon or a base substrate. The base film and the base substrate are made of silicon oxide, silicon nitride, silicon carbide, tungsten carbide, boron nitride. An insulating film or an insulating substrate of aluminum nitride, alumina, titanium oxide, zirconium oxide or the like; a conductive film of Ta, Ru, Cr, W or the like; Among these, silicon oxide, silicon nitride, and silicon carbide are particularly preferable. The material for the base film or the like may be selected from the above materials so that the etching rates of the diamond film, the silicon substrate, and the base film are different. With this configuration, the diamond film can be easily formed on the substrate, and the substrate can be easily removed by etching. Therefore, the smoothness and the film stress of the obtained diamond film are not impaired.

When a diamond film is formed on a silicon substrate on which a base film has been formed or on a base substrate as in the present invention, the surface of the diamond film is removed together with the removal of the substrate in the step of etching and removing the silicon substrate with an alkaline aqueous solution. Since the film is not damaged, the surface condition of the film is good, and the occurrence of defective products having uneven film thickness and film stress can be prevented, and the yield can be improved.

[0035]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples. In addition, a diamond film is formed on a substrate based on the method as shown in FIG. 1 and the substrate or the like on which the diamond film is formed is removed by etching according to the method as shown in FIG. 2 to produce a diamond film for lithography. did.

Example 1 First, as shown in FIG. 2A, a double-side polished silicon wafer (100) 21 having a diameter of 3 inches and a thickness of 2 mm was prepared, and the surface thereof was decompressed by CV.
A silicon nitride film 22 having a thickness of 0.5 μm was formed by Method D (FIG. 2B). Before the diamond film 23 was formed on the silicon substrate 21 on which the silicon nitride film 22 was formed, the surface of the silicon nitride film 22 was treated with fluidized diamond particles to facilitate generation of diamond nuclei.

After the above processing, a diamond film 23 was formed on the silicon substrate 21 on which the silicon nitride film 22 was formed (FIG. 2C). The diamond film 23 was formed using the microwave CVD device shown in FIG. 1 as follows. The silicon substrate 21 on which the surface-treated silicon nitride film (insulating film) 22 is formed is placed on the heating body 14 and evacuated to 10 ⁻³ Torr or less with a rotary pump, and then methane gas, hydrogen gas and oxygen A mixed gas composed of gas was supplied from a gas introduction pipe 11. The supply of each gas is as follows: methane gas is 45.0 sccm, hydrogen gas is 945.0 sccm, oxygen gas is 10.0 sccm, and the volume ratio is methane gas / hydrogen gas / oxygen gas =
It was 4.5 / 94.5 / 1.0. Next, the gas discharge pipe 1
Adjust the valve of No. 2 to 30 Torr inside the chamber 13
Then, a microwave of 3000 W power is applied to generate plasma, and a diamond film is formed on the substrate by 3 μm.
It went for 7 hours. Note that the substrate was not heated during film formation, but the substrate surface temperature at this time was 860 ° C.

The obtained diamond film 23 was a polycrystalline diamond having a thickness of 3.0 μm. The film stress of this diamond film was 0.4 × 10 ⁹ dyn / cm ² as a tensile stress as calculated from the warpage of the substrate.

Next, after masking the area other than the 30 mm square center of the back surface of the substrate (FIG. 2C) on which the diamond film has been formed by the above-described method, the silicon nitride film 22 is treated with a hydrofluoric acid aqueous solution. The part was removed by etching (FIG. 2
(D)). Next, the silicon substrate 21 was removed by etching with a 95 ° C. aqueous solution of potassium hydroxide until the silicon substrate 21 reached the silicon nitride film 22 (FIG. 2E). In this case, the silicon 21 is etched with an aqueous solution of potassium hydroxide, but since the silicon nitride film 22 has a low etching rate, the etching process can be easily terminated when the etching reaches the silicon nitride film 22. Next, the silicon nitride film 22 was removed by etching with a hydrofluoric acid aqueous solution (FIG. 2F) to obtain a diamond film for lithography. The etched surface of the obtained film had no corrosion and was excellent in smoothness.

(Example 2) A substrate having a diameter of 3 inches and a thickness of 2
Microwave CVD under the same conditions as in Example 1 except that the base substrate (insulating substrate) made of silicon nitride of
A polycrystalline diamond film having a thickness of 3.0 μm was obtained by forming a diamond film on the substrate by the method. The film stress was 2.5 × 10 ⁹ dyn / cm ² in tensile stress. After masking with a resin film the area other than the 30 mm square in the center of the back surface of the formed substrate, the underlying substrate was removed by etching with a hydrofluoric acid aqueous solution to obtain a diamond film for lithography. The etched surface of the obtained film had no corrosion and was excellent in smoothness.

Comparative Examples 1 to 3 In Comparative Examples 1 and 2, a diamond film for lithography was prepared under the same conditions as in Example 1 except that the mixed gas was changed to the volume ratio and the film forming time shown in Table 1. Produced. In Comparative Example 3, lithography was performed under the same conditions as in Example 1 except that the silicon wafer (100) was used alone as the substrate, the film formation time was set to 35 hours, and the substrate was removed by etching using only a potassium hydroxide aqueous solution. Diamond film was prepared. The test results are shown in Table 1.

[0042]

[Table 1]

As is evident from the results in Table 1, in the comparative example, a membrane consisting of a satisfactory diamond film was not obtained under any conditions. In particular, when silicon was used for the substrate and only the alkaline aqueous solution was used for the etching solution as in Comparative Example 3, the surface of the diamond film formed on the silicon substrate was eroded by the alkaline aqueous solution in the etching step. As a result, the smoothness and film stress of the diamond film were impaired.

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

[0045]

According to the present invention, it is possible to form a diamond film having high crystallinity and a desired film stress on a substrate, and to perform X-ray or electron beam irradiation without impairing the smoothness and film stress after film formation. A diamond film for lithography can be manufactured.

[Brief description of the drawings]

FIG. 1 shows a microwave CV used in the manufacturing method of the present invention.
It is the schematic of the D apparatus.

FIGS. 2A to 2F show an example of a process for producing a diamond film for lithography according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Microwave CVD apparatus, 11 ... Gas introduction pipe, 12 ... Gas exhaust pipe, 13 ... Chamber, 14 ...
-Heating body, 15 ... Substrate stand, 16 ... Substrate, 17 ... Microwave power supply, 18 ... Heater power supply, 19 ... Waveguide, 21
... silicon substrate, 22 ... base film, 23 ... diamond film.

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI H01L 21/205 H01L 21/30 531M 21/306 541S 21/306 B (72) Inventor Yoshihiro Kubota 2-3-13-1 Isobe, Annaka-shi, Gunma Prefecture No. Shin-Etsu Chemical Co., Ltd.Precision Functional Materials Research Laboratories (72) Inventor Ikuo Okada 2-1-1 Nishi-Shinjuku, Shinjuku-ku, Tokyo NTT Advanced Technology Co., Ltd. (56) References JP JP-A-2-158121 (JP, A) JP-A-4-338628 (JP, A) JP-A-11-40494 (JP, A) JP-A-64-73720 (JP, A) JP-A-61-32425 (JP) , A) JP-A-2000-182947 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027 G03F 1/16

Claims (5)

(57) [Claims] 1. A causes the entire surface of the silicon substrate to form a base film, after methane on one surface of the lower Chimaku, a mixed gas of hydrogen gas and oxygen gas were deposited diamond film as a raw material gas, A method for producing a diamond film for lithography by etching and removing a part of a base film on a back surface, etching and removing a silicon substrate, and subsequently etching and removing the base 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. 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. 4. The mixing ratio of the source gas is such that the methane gas amount is 0.1% by volume or more and 20% by volume or less and the hydrogen gas amount is 70% by volume or less.
Volume% or more and 99.89 volume% or less.
The method according to any one of claims 1 to 3, wherein a source gas having a volume of 1% by volume or more and 10% by volume or less is used. 5. The method according to claim 5, wherein the film is formed by a microwave CVD method or a hot filament CVD method so that the surface temperature of the substrate is 700 ° C.
The method according to any one of claims 1 to 4, wherein the method is performed at a temperature of from 1 to 1200 ° C.