JPH09260251A - Manufacture of mask membrane for x-ray lithography use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make high the generation of diamond nuclei and the in-plane evenness of the stress distribution and the film thickness distribution of a diamond membrane by a method wherein a silicon substrate prior to a film formation is brought into contact with diamond particles fluidized with gas. SOLUTION: Diamond particles of a particle diameter of about 0.1 to 700μm are fluidized with inert gas, such as the air, nitrogen gas and argon gas, conforming to a synthetic condition and the gas is made to flow in a treating device in the reverse direction to the direction of the force of gravity as evenly as possible setting the velocity of the gas at a flow velocity of 5 times or quicker than the flow starting velocity of the diamond particles. The treating surface of a substrate 1 to be treated is installed in a fluidized layer 2 consisting of these diamond particles in such a way as to make to fix or float turning vertically to the direction of the flow of the gas fluid. By generating diamond nuclei of a prescribed density on the substrate 1, a diamond membrane, which has a high visible light transmittance and is very high in the in-plane evenness of its film thickness distribution and its stress distribution, can be obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method of manufacturing a mask membrane for X-ray lithography.

[0002]

2. Description of the Related Art With the miniaturization of pattern formation in the fabrication of semiconductor devices, as a future lithography technique,
X-ray lithography technology holds promise. The important performance required for the X-ray transparent film (hereinafter abbreviated as a membrane) of the mask used for X-ray lithography is shown below. Must have surface smoothness. High mechanical strength. High visible light transparency required for highly accurate alignment. It has good chemical resistance and moisture resistance, and is not easily damaged during etching and cleaning processes. High-energy electron beam and synchrotron radiation (hereinafter SR
Abbreviated). Conventionally, BN, boron-doped silicon, SiNx, SiC, diamond, etc. have been proposed as a mask membrane material for X-ray lithography. Among them, diamond is
Compared with other materials, Young's modulus, etching resistance, SR resistance
It is considered to be optimal as an X-ray mask membrane material because of its unique property in irradiation property. Normal,
As a method for forming a diamond film, DC arc discharge, DC glow discharge, combustion flame, high frequency (13.56MHz), microwave (2.45GHz), hot filament, etc. can be mounted. In particular, microwave CVD method is electrodeless. Since it is generated by electric discharge, it is most commonly used because it does not contain impurities and is capable of stable and long-term film formation with good reproducibility. By the way, although silicon, which is advantageous in semiconductor processes, is used for the X-ray mask substrate, even if the film is directly formed on this substrate by the various methods described above, diamond nuclei are scarcely generated and the diamond film Is hard to grow.
Therefore, there is also an example in which a diamond film is grown by applying a bias voltage to the substrate in microwave discharge to promote the generation of diamond nuclei. (S.Yugo; Appl.Phys.Lette
r, 58 , pp. 1036 (1991)).

[0003]

However, in order to use this diamond film as an X-ray mask membrane, the nucleation density is not yet sufficient, and the film is formed for a standard X-ray mask size of 3 inches. However, due to the non-uniformity of the processing state, it is not at a practical level. In addition, the surface of a silicon substrate is also scratched with diamond particles before film formation. Specifically, the method shown below is used. The surface of the silicon substrate is polished with diamond particles or a paste containing diamond particles. A silicon substrate is placed in a liquid in which diamond particles are dispersed in acetone, ethanol, etc., and ultrasonic scratching is performed. However, in the method, it is difficult to make the polishing direction and load uniform, and in the method, it is difficult to obtain a dispersed state of diamond particles and it is difficult to uniformly contribute energy of ultrasonic vibration to the substrate. Therefore, the film stress and film thickness distribution uniformity of the obtained film are low. In addition, in any of the methods, the diamond nucleus generation density was not sufficient, and there was a defect that it was difficult to obtain a smooth film having a thickness of 1 to 3 μm.

[0004]

The present invention has been made by various studies in order to solve the above problems in view of the above problems, and the present invention forms a membrane composed of vapor phase synthetic diamond on a silicon substrate. A method for producing a mask membrane for X-ray lithography, comprising: bringing a silicon substrate before film formation into contact with diamond particles fluidized by a gas. is there.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In order to obtain a high visible light transmittance in a vapor phase synthesized polycrystalline diamond membrane, it is effective to make the crystal particles small and reduce the irregular reflection on the membrane surface. It is required to cause diamond particles to collide with the surface of a silicon substrate to scratch the surface of the silicon substrate, and to leave diamond particles to increase diamond nucleus generation during film formation. On the other hand, in order to increase the uniformity of membrane stress and film thickness in-plane distribution on diamond,
A uniform distribution of scratches and diamond residues in the above-mentioned diamond particle collision is required. As a substrate pretreatment method satisfying these requirements, a so-called fluidization pretreatment method, which is carried out by putting diamond particles into a layer fluidized by a gas fluid having a flow initiation speed or more, was considered.

FIG. 1 shows an apparatus for carrying out the flow pretreatment method according to the present invention. The flow pretreatment method will be described below with reference to FIG. First, the processing layer container 5 has a size sufficiently large with respect to the substrate that the fluidized state can be obtained even if the silicon substrate 1 enters the fluidized bed 2. Normal 3 "
In the case of a silicon substrate with a diameter, a tubular shape with an inner diameter of 8 ″ is preferable. As the diamond particles, commercially available synthetic diamond and natural diamond having a particle diameter of 0.1 to 700 μm can be used.
Use m according to the synthesis conditions. As the fluid gas, air and an inert gas such as nitrogen or argon may be used in order to facilitate handling and prevent a chemical reaction on the surface of the silicon substrate.

The fluidizing gas velocity of diamond particles is preferably as uniform as possible in the direction opposite to the direction of gravity in the processing container at a flow velocity value of 5 times or more the flow initiation velocity.
The flow start velocity Umf is, for example, Archimedes number 1.
When 9 × 10 ⁴ or less, it is calculated by the formula (1). ^{Umf = dp 2 (ρp -ρf)} G / 1650μ ... (1) Equation (1) symbols, dp; diamond particle size, .rho.p;
Diamond particle density, ρf; gas fluid density, G; gravitational acceleration, μ; viscosity, and the unit is CGS unit.
If the fluidization gas velocity of diamond particles is less than 5 times the fluidization initiation velocity, a sufficient fluidized layer cannot be obtained, and if it exceeds 100 times, the fluidized layer will be destroyed.
The substrate 1 to be treated is placed in the fluidized layer 2 of diamond particles, but the installation method may be fixed or floating. However, the treated surface is preferably perpendicular to the flow direction of the gas fluid in order to obtain a large treatment effect. Figure 1
It is fixed by the fixing jig 4 shown in.

The diamond nucleus generation density on the silicon substrate during film formation is preferably 1 × 10 ⁶ mm ⁻² or more and 1 × 10 ⁶
If it is less than mm ^-2 , a high visible light transmittance cannot be obtained in a vapor-phase synthesized polycrystalline diamond membrane, and the in-plane uniformity of film thickness cannot be increased.

The diamond film forming method may be a known method. For example, DC arc discharge, DC glow discharge, combustion flame, high frequency (13.56MHz), microwave (2.45GHz), hot filament, etc. can be mounted. Is preferable, and it is possible to form a film for a long time stably with good reproducibility.

[0010]

EXAMPLES Examples and comparative examples will be shown below, but the present invention is not limited thereto. Example As a substrate, a double-side polished silicon substrate (100) having a diameter of 3 inches and a thickness of 600 μm was used, and a pre-flow treatment was performed by the apparatus shown in FIG. The processing layer container of the apparatus was an acrylic tube having an inner diameter of 8 inches and a height of 1 m. As the diamond particles, 700 g of synthetic diamond having a particle size of 400 μm was put into 700 g, and nitrogen gas as a gas fluid was made to flow vertically in the opposite direction from below through a wire mesh of a stainless mesh of 40 μm in size. The flow velocity is 20 times 36 times that of Umf 18.3 cm / sec.
It was 6.0 cm / sec. The treated surface of the silicon substrate was fixed in the direction perpendicular to the gas flow and near the center of the fluidized layer of diamond particles and treated for 3 hours.

The diamond film was formed on the surface of the silicon substrate by the microwave CVD method shown below. First, set the treated silicon substrate in the chamber and evacuate it with a rotary pump to a base pressure of 10 ^-3 Torr or less, and then pass the source gases hydrogen and methane at 997 cc / min and 3 cc / min, respectively. did. Adjust the opening of the valve leading to the exhaust system to
After setting to Torr, input microwave of power 3000W,
Time film formation was performed. At this time, the surface temperature of the silicon substrate was 900 ° C due to the microwave power. The obtained diamond was a polycrystalline diamond having a film thickness of 1.2 μm. The nucleation density is 7 mm from the substrate edge,
1.6 x 10 ⁸ pieces at 23 mm and 39 mm positions mm ^-2 , 2.0 x
10 ⁸ mm ^-2 , 2.0 x 10 ⁸ mm ^-2 with extremely high density and high uniformity, with a film thickness distribution of 3 "center film thickness 1.2"
± 3% was achieved for μm. Furthermore, the smoothness of the surface was about 50 nm in the centerline average roughness Ra at any position, which was a good value. Next, 30 mm of silicon on this substrate
Removed by wet etching in the range of 30 mm × 30 mm, 30 mm × 30
mm membrane was completed. This membrane had little scattering of incident light due to surface irregularities, and the transmittance of incident light at 633.1 nm was 59%.

Comparative Example An ultrasonic vibration method was used as a pretreatment method for forming a film on a silicon substrate. That is, 100 g of artificial diamond having a particle size of 10 μm is dispersed in 3000 cc of hexane to obtain a solution of 3 inch diameter and thickness of 600 μ.
An m 2 silicon substrate (100) double-side polished product was put in, and ultrasonic vibration was applied for 40 minutes. After that, ultrasonic cleaning was performed for 15 minutes in a cleaning tank containing only hexane to perform film formation pretreatment of the silicon substrate.

A film was formed on this substrate by the microwave CVD method under the following conditions. Incident power 3000W, source gas hydrogen / methane = 997CCM / 30CM, atmospheric pressure 40Torr, substrate temperature 9
The film formation time was set to 00 ° C. for 30 hours. The nucleation densities of the obtained polycrystalline diamond were 9.2 × 10 ⁴ pieces mm ^-2 , 3.6 × 10 ⁵ pieces mm ^-2 , 8.2 at the positions of 7 mm, 23 mm, and 39 mm from the substrate edge, respectively.
The density was as low as × 10 ⁴ mm ^-2 and was non-uniform. 3
The film thickness at the measurement points was 1.0 μm ± 40%, and many discontinuous film states were also confirmed due to the low nucleation density. The surface smoothness was poor and the center line average roughness was 250 μm. Therefore, there was a lot of scattering of alignment light on the surface of the obtained membrane, and the transmittance of incident light with an average thickness of 1 μm of 633.1 nm was 39%, which was an insufficient value for highly accurate alignment.

[0014]

According to the present invention, since the initial nucleation density of diamond is extremely high, the surface smoothness is excellent even in the thin film state of 1 to 3 μm, and the irregular reflection of alignment incident light on the surface is reduced. It has a high visible light transmittance and is pre-treated for the substrate in the gas fluidized bed.
It is possible to obtain a diamond membrane in which the in-plane uniformity of the effect of diamond seeding is good and the in-plane uniformity of film thickness distribution and stress distribution is extremely high.

[Brief description of drawings]

FIG. 1 is a perspective view of an apparatus for performing a flow pretreatment according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Silicon substrate 2 ... Fluidized bed 3 ... Stainless wire mesh 4 ... Fixing jig 5 ... Processing layer container

Claims (3)

[Claims] 1. A method of manufacturing a mask membrane for X-ray lithography, which comprises forming a membrane made of vapor-phase synthetic diamond on a silicon substrate, wherein the silicon substrate before film formation is brought into contact with diamond particles fluidized by gas. A method of manufacturing a mask membrane for X-ray lithography, comprising: 2. The method for producing a mask membrane for X-ray lithography according to claim 1, wherein the fluidizing gas velocity of the diamond particles is 5 times or more the flow initiation velocity. 3. The method for producing a mask membrane for X-ray lithography according to claim 1, wherein the diamond nucleus generation density on the silicon substrate in the film formation is 1 × 10 ⁶ pieces mm ⁻² or more.