JPH05326379A - Manufacture of thin film - Google Patents

Abstract

PURPOSE:To set the internal stress of a mask substrate for X-ray lithography within a proper range and to reduce an irregularity in the internal stress by a method wherein, when a thin film is formed on the substrate by sputtering, the electric power of reflected waves is kept at a definite value when the film is formed. CONSTITUTION:A target, 3cm in diameter and 5 mm in thickness, which is composer of SiC is set on the cathode side of, e.g. an RF magnetron sputtering apparatus, Model SDF-32H (made by Nichiden Anelva K.K.). A silicon wafer substrate, 3cm in diameter and 600mum in thickness, whose both faces have been polished is heated to 200 deg.C. In addition, while argon gas is being made to flow at a flow rate of 7cc/min, a sputtering operation is performed for 10 minutes under the following conditions: power supply: 10W/cm<2> (in this case, the electric power of incident waves is kept at 400W and the electric power of reflected waves is kept at 65W); and reaction pressure: 6.0X10<-2>Torr. A thin film, 1.0mum in film thickness, which is composed of SiC is former. Thereby, it is possible to reduce an irregularity in the internal stress of the film.

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 thin film, and more particularly to a method for producing a thin film which is useful as a mask substrate for X-ray lithography in which variation in internal stress of the film within and between batches is reduced. It is a thing.

[0002]

2. Description of the Related Art The X-ray transparent film of an X-ray lithography mask is (1) a material that can withstand irradiation of high energy beams such as high energy electron beams and synchrotron radiation. (2) It has a high visible light transmittance of 50% or more and can perform highly accurate alignment. (3) It has good chemical resistance and moisture resistance, and is not easily damaged in the etching process and cleaning process. (4) The surface of the membrane is smooth and free from scratches and pinholes. The performance of the mask substrate for X-ray lithography is tensile stress, and the internal stress of the thin film of the substrate is tensile stress, but when this tensile stress is 1 × 10 ⁸ dyne / cm ² or less Easy to generate wrinkles, 1 × 10 ¹⁰ dy
When ne / cm ² or more, the membrane is easily broken, so the preferred tensile stress is 5 × 10 ⁸ dyne / cm ^{2 to} 5 × 10 ⁹ dyne.
The range is / cm ² .

The material of the X-ray transparent film of the X-ray lithography mask is plasma CVD method, LPCV.
Materials such as BN, SiN, and SiC by the D method have been proposed, but each has advantages and disadvantages, and none satisfying all of the above-described performances has been obtained. For example, a BN or SiN film formed by the plasma CVD method has excellent visible light transmittance, but it has insufficient high energy beam resistance and chemical resistance, and SiN formed by the LPCVD method.
Although the film also has excellent visible light transmittance, it has been pointed out that the high energy beam resistance is insufficient.
The SiC film formed by the CVD method has a drawback that the surface smoothness is insufficient.

[0004]

For this reason, the inventors of the present invention first conducted the sputtering method using SiC and SiC / Si ₃ N.
₄ We have proposed a method for forming a composite film (Japanese Patent Laid-Open No. 2-1597).
No. 16, JP-A-3-56660). According to this, it is possible to obtain a thin film having excellent properties such as high energy beam resistance, visible light transmittance, chemical resistance, and surface smoothness. However, since the thin film formed by this sputtering method reacts extremely sensitively to changes in the conditions during film formation, it is difficult to control the internal stress, and the internal stress value often deviates from the above. It turned out that there is a disadvantage that the production yield is reduced.

[0005]

The present invention relates to a method of manufacturing a thin film which solves such disadvantages, and in forming a thin film on a substrate by a sputtering method, the reflected wave power during film formation is It is characterized by maintaining a constant value.

That is, the inventors of the present invention have made various investigations on methods for solving the above-mentioned disadvantages in the method of producing a thin film on a substrate by a sputtering method, and as a result, various sputtering conditions controllable during sputtering and in batch and batch The relationship between the internal stress of the film and the internal stress of the film is investigated.
It has been found that the variation in the internal stress of the film can be reduced by making it as small as possible and keeping it at a constant value, and according to this, it is most important as a mask substrate for X-ray lithography. It is easy to finish the internal stress of the film, which is one of the characteristics, within an appropriate range, the yield can be improved, and the variation in internal stress can be reduced. The present invention has been completed by confirming that the pattern can be made uniform and the pattern distortion correction process at the time of forming the absorber becomes easy. This will be described in more detail below.

[0007]

The present invention relates to a method for producing a thin film,
This is characterized in that when forming a thin film on a substrate by a sputtering method, the reflected wave power during film formation is maintained at a constant value. According to this, the inside of the mask substrate for X-ray lithography is There is an advantage that the stress can be set within an appropriate range and the variation of the internal stress can be reduced.

The thin film according to the present invention is manufactured by a method of forming a thin film on a substrate by a sputtering method. This sputtering method may be a known method, which is a commonly used high frequency (hereinafter referred to as RF). The sputter method may be used. In the film formation by the RF sputtering method, electric power (hereinafter, abbreviated as incident wave power) is input for the target arranged in the apparatus, and the reflected wave power generated due to the mismatch of the incident wave power is always the minimum. However, if there is a large deviation between the output impedance of the RF oscillator and the load impedance, the life of the RF oscillator tube and the RF cable will be shortened, and the input power will be used for efficient target sputtering. In terms of use, it is necessary to reduce such deviation.

However, as a result of various studies on this,
If the reflected wave power is adjusted to be the minimum, the power is supplied most efficiently to perform the sputtering, but even if the operation to minimize the reflected wave power changes the state of the target, it contributes to the sputtering. Since the amount of electric power changes, constant sputtering is not performed, and this causes variations in the physical properties of the thin film after film formation, especially internal stress.

Then, when the film formed by the sputtering method was examined, when the sputtering pressure was constant,
There is a correlation between the magnitude of the reflected wave power and the internal stress, and the internal stress changes depending on the magnitude of the reflected wave power, and it is clear that the reflected wave power contributes to the variation in the internal stress. It was

Therefore, the inventors of the present invention formed a thin film by the sputtering method with the film forming pressure and the reflected wave power at constant values in order to reduce the variation in the internal stress. It was confirmed that it would decrease.

It is possible by adjusting the deviation of matching,
The value of the minimum reflected wave power changes depending on the type of film to be formed and the usage of the target, so the value of the reflected wave power to be kept constant must be selected according to the situation. If the power value is too small, it will have to be changed during a series of sputtering film formation, and if it is too large, the difference between the output impedance and the load impedance of the RF oscillator will become large, and the RF oscillation tube or RF cable Since it shortens the life of the laser, it is the minimum reflected wave power that can be corrected by adjusting the matching shift that changes over time, and the value does not change during a series of sputter deposition. Is good.

Since the production of the thin film according to the present invention is carried out on the substrate by the sputtering method, the target is set in the apparatus and the film is formed from this target. The target material for the sputter film formation is particularly limited. However, ceramics, metals, etc. can be used for this. Further, since this thin film obtained by is the X-ray lithography mask substrate, this compound SiC, Si ₃ N
₄ , composite material of SiC and Si ₃ N ₄ , Si, SiO ₂ ,
The material is not limited to this, although it may be made of BN, diamond, or the like.

This thin film is formed on a substrate by a sputtering method. A silicon wafer is usually used as this substrate, and the temperature of this silicon substrate is 100 to 1,000.
When the temperature is set to ° C, the formed film has few defects and pinholes, which is preferable. Further, if the power applied to this target is 5 w / cm ² or more, the stress of the obtained film becomes a tensile stress, which is preferable, but the higher the applied voltage, the more the film formation rate increases, which is advantageous.

The gas used for sputtering is preferably an inert gas having a purity of 99% or more, preferably 99.9% or more, and examples thereof include Ar, Ne, He and Xe. The sputter pressure is not particularly limited, however, since the sputter pressure has a great influence on the stress value of the film after film formation, it is necessary to obtain a predetermined tensile stress under the sputter conditions including the composition of the target. Must be set, so this is ^{1x10 -2} to ^{1x10 -1} To
It should be rr.

[0016]

EXAMPLES Next, examples and comparative examples of the present invention will be described. Example 1 A target made of SiC having a diameter of 3 inches and a thickness of 5 mm was set on the cathode side of an RF magnetron sputtering apparatus SPF-332 H type (trade name, manufactured by Nichiden Anelva Co., Ltd.), and then a diameter of 3 inches and a thickness of 600 μm. Double-sided polished silicon wafer substrate is heated to 200 ℃, and argon gas is 7cc.
Sputtering was performed for 10 minutes under the conditions of a power density of 10w / cm ² (incident wave power was kept at 400w, reflected wave power was kept at 65w) and reaction pressure was 6.0 × 10 ^-2 Torr while flowing at a flow rate of / min. , A thin film of SiC having a thickness of 1.0 μm was formed.

When 10 batches of film formation were repeated under the same conditions, the stress values at this time were 2.5 × 10 ⁹ ± 0.5 × 10 ⁹ dyne with an average and 3σ (σ is standard deviation).
It was / cm ² .

Comparative Example 1 A thin film of SiC was manufactured by the same method as in Example 1, but the reflected wave power was not kept constant, but was varied from 60w to 65w and was constantly minimized for 10 batches. When a film is formed, the stress value at this time is the average and 3σ
It was 2.5 × 10 ⁹ ± 1.5 × 10 ⁹ dyne / cm ² .

Example 2 Si having a diameter of 3 inches and a thickness of 5 mm on the cathode side of the RF magnetron sputtering apparatus SPF-332 H type (described above).
After setting a target in which C and Si ₃ N ₄ were mixed at a molar ratio of 95: 5, a double-side polished silicon wafer substrate having a diameter of 3 inches and a thickness of 600 μm was heated to 200 ° C., and argon gas was supplied at 7 cc / min. While flowing at a flow rate, power density 10w /
cm ² (In this case, the incident wave power is 400w, the reflected wave power is 65w
Under a reaction pressure of 6.0 × 10 ^-2 Torr for 15 minutes to form a thin film of SiC and Si ₃ N ₄ with a thickness of 1.0 μm. When the film was repeatedly formed, the average stress value and the 3σ value at this time were 1.5 × 10 ⁹ ± 0.5 × 10 ⁹ dyne / cm ² .

Comparative Example 2 Further, a thin film of SiC and Si ₃ N ₄ was manufactured by the same method as in Example 2, but the reflected wave power was not made constant but was varied from 60w to 65w and was constantly minimized. As a result of repeatedly depositing 10 batches of the film, the average stress value and 3σ were 1.5 × 10 ⁹ ± 1.0 × 10 ⁹ dyne / cm ²
Met.

[0021]

The present invention relates to a method of manufacturing a thin film, and as described above, when the thin film is formed on the substrate by the sputtering method, the reflected wave power during film formation is kept constant. According to this, since the variation in the internal stress of the film is reduced in the film formation obtained by repeating the sputtering method, the mask substrate for X-ray lithography made from this thin film has a high manufacturing yield. And the distortion correction of the mask substrate in the absorber forming step is facilitated.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiro Kubota 2-13-1, Isobe, Annaka-shi, Gunma Shin-Etsu Chemical Co., Ltd. Precision Materials Research Laboratory

Claims (3)

[Claims] 1. A method of manufacturing a thin film, characterized in that when a thin film is formed on a substrate by a sputtering method, the reflected wave power during film formation is maintained at a constant value. 2. The method for producing a thin film according to claim 1, wherein the thin film is ceramics or metal. 3. The method for producing a thin film according to claim 2, wherein the thin film is used as a mask substrate for X-ray lithography.