JPH0692791A - Method for selectively form diamond - Google Patents

Abstract

PURPOSE:To provide a method for selectively forming diamond by which diamond suitable for use in a high performance semiconductor device, a field emitter array, an optical waveguide, etc., can easily be formed in an arbitrary size and shape by simple operation. CONSTITUTION:A pattern is formed on the surface of a substrate with a pattern forming material which is etched at a lower rate than the material of the substrate and has a higher m.p. than the temp. at which diamond is synthesized. Scribing and etching are carried out and then diamond is patternwise formed by vapor phase synthesis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for selectively forming diamond. More specifically, the present invention relates to a method for selectively forming diamond, which is suitable for high-performance semiconductor devices, field emitter arrays, optical waveguides, etc. The present invention relates to a method for selectively forming diamond, which can be formed into a shape easily and easily with a simple operation.

[0002]

2. Description of the Related Art In recent years, CVD using a mixed gas of a carbon-containing compound and hydrogen as a raw material
A technique for depositing and forming diamond on the surface of a substrate has been developed by using a vapor phase diamond synthesis technique such as a PVD method or a PVD method, and attention has been paid to its use in the fields of cutting tools, semiconductor devices, and the like. Recently, a technology for selectively forming a diamond film with a fine pattern on the surface of a substrate has been developed, and not only carbide tools such as cutting tools and polishing tools but also various sliding members and wear resistant members, and Is expected to be used in a wide range of applications for various materials in the field of electronic and electrical equipment such as high-performance semiconductor devices.

As a method for selectively forming diamond on the surface of a substrate by such a vapor phase method, there are methods described in JP-A-2-30697 and JP-A-3-278643, for example. . The former is a method of forming a pattern of a mask material on the surface of a substrate that has been scratched, then removing the pattern by etching, and forming diamond by a vapor phase method on the surface of the substrate. In the latter case, after forming a pattern by a mask material on the surface of the scratched substrate, the pattern is etched by obliquely irradiating the substrate with an argon beam, and subsequently diamond is formed by a vapor phase method. Is the way.

However, the former method has a problem that the process is complicated, for example, the pattern formed by the mask material must be removed. Further, in the latter method, since the argon beam is obliquely irradiated during etching, it is impossible in principle to form a pattern parallel to the incident direction, and it is impossible to form an arbitrary pattern. There is. Therefore, with these methods, it is not possible to selectively and easily produce diamond having any shape and size with good reproducibility.

The present invention solves the above problems and
Diamonds suitable for a wide range of fields including electronic devices such as high-performance semiconductor devices, field emitters, optical waveguides, etc. can be easily and easily selected in any size and shape with high selectivity by simple operation. It is to provide a selective formation method of diamond that can be formed with good reproducibility.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that
When a pattern is formed using a pattern forming material having a specific etching rate and a melting point, scratching is performed, etching is performed, and diamond synthesis is performed, diamond can be selectively and easily formed only on the surface of the pattern. It was found that they can be formed with good reproducibility.

The present invention is based on the knowledge of the present inventors. That is, the invention according to claim 1 for achieving the above object is to form a pattern on the surface of a substrate with a pattern forming material having an etching rate slower than that of the substrate material and having a melting point higher than the synthesis temperature of diamond. After that, a scratching treatment is performed, an etching treatment is performed, and then diamond synthesis is performed by a vapor phase method to form diamond in the above-mentioned pattern, which is a selective formation method of diamond.

The present invention will be described in detail below. According to the method of the present invention, 1) a step of forming a pattern on the surface of a substrate with the pattern forming material (hereinafter referred to as a pattern forming step), 2) a step of scratching the surface of the substrate using abrasive grains ( Hereinafter, it will be referred to as a scratch treatment step), 3) a step of etching the surface of the substrate (hereinafter referred to as an etching treatment step), and 4) a step of forming diamond by a vapor phase method on the surface of the substrate (hereinafter , Diamond forming step).

The above steps will be described in order below. —Pattern Forming Step— In the pattern forming step, a pattern having a desired shape and size is formed on the surface of the substrate with a specific pattern forming material. A lithographic technique can be used to form the pattern. Specifically, the following <Pattern formation 1> method can be given as an example.

<Pattern Formation 1> First, a pattern forming coating solution containing a resist agent such as photoresist is applied to the entire surface of the substrate and dried. Next, after irradiating light such as ultraviolet rays as shown in FIG. 5 through a photomask 5 having a mask pattern opposite to the target pattern as shown in FIG. A resist film 4 as shown in 1 is formed on the surface of the substrate 1. Then, as shown in FIG. 7, a molybdenum film 6 is formed on the entire surface of the substrate 1 by, for example, a vapor deposition method. After that, when the resist film 4 on the substrate 1 is dissolved and removed by a solvent, the molybdenum film 6 formed on the surface is also removed at the same time. As a result, as shown in FIG.
This is a method of forming a pattern 2 having the same size and shape as a target pattern.

As another example, the following <pattern formation 2> method can be cited. <Pattern formation 2> First, a molybdenum film, for example, is formed on the entire surface of the substrate by, for example, an evaporation method. A pattern forming coating solution containing a resist agent such as a photoresist is applied to the entire surface and dried. Next, FIG.
Light such as ultraviolet rays is irradiated as shown in FIG. 8 through the photomask 5 having a mask pattern opposite to the target pattern as shown in FIG. After that, the unexposed portion is removed, and then FIG.
A resist film 4 as shown in is formed. Subsequently, by etching the molybdenum film 6 by, for example, a sputtering process, as shown in FIG.
The molybdenum film 6 exposed above is removed. After that, when the resist film 4 on the substrate 1 is dissolved and removed, the molybdenum film 6 protected thereunder is exposed. As a result, as shown in FIG. 3, the pattern 2 having the same size and shape as the target pattern is formed on the substrate 1.

As the resist agent, a resist for electron beam or X-ray can be used in addition to photoresist. Examples of the photoresist include a negative type photoresist and a positive type photoresist. In addition to the commonly used resists, various known resin-based or rubber-based photoresists can be used.

Examples of commercially available negative photoresists include LMR-33 manufactured by Fuji Yakuhin Kogyo Co., Ltd. and OMR-83 and OMR-85 manufactured by Tokyo Ohka Kogyo Co., Ltd. Further, as the commercially available product of the positive photoresist, OFPR- manufactured by Tokyo Ohka Kogyo Co., Ltd. is used.
2 and OFPR-800. In the present invention, a positive photoresist can be preferably used when <Pattern formation 1> is adopted, and a negative photoresist can be suitably used when <Pattern formation 2> is adopted.

The method for preparing the coating solution for pattern formation is not particularly limited, and various known methods can be adopted. Examples of the method for applying the coating liquid for pattern formation include a method using a spray, a spinner, a dip, and the like. Among these, the method using a spinner is preferable.

After applying the coating solution for pattern formation, it is usually dried to obtain a resist layer. The thickness of the resist layer when dried is not particularly limited,
Usually, it is about 0.5 to 3 μm. The resist layer is
As shown in FIGS. 5 and 8, it can be formed by irradiating the resist layer 4 with light such as ultraviolet rays through the photomask 5, and developing and rinsing.

In order to remove the resist layer, an appropriate method can be selected. For example, a method using plasma, a method using acetone, alcohol, cellosolve, a mixed solution of sulfuric acid and hydrogen peroxide, a solvent such as dimethylformamide and the like can be mentioned. Examples of the method of exposure by irradiating with light such as the ultraviolet rays, for example,
A contact exposure method, a proximity exposure method, a projection exposure method and the like can be mentioned, and various methods can be appropriately selected and used according to the purpose.

The pattern forming material for forming the film is not particularly limited as long as it is a substance having an etching rate slower than that of the substrate material and a melting point higher than the synthesis temperature of diamond, and examples thereof include molybdenum, titanium and tungsten. Examples thereof include simple metals such as cobalt and nickel, metal compounds such as iron oxide, alumina and silicon carbide, and carbon.

Specifically, the substrate material is silicon,
When etching is performed using an argon ion beam to synthesize diamond at 900 ° C., the pattern forming material has a lower etching rate than the argon ion beam etching rate (370 Å / min) of silicon and a melting point of diamond. Is a substance having a synthesis temperature of 900 ° C. or higher.

As such a substance, for example, molybdenum (etching rate 230Å / min: melting point 2622) is used.
± 10 ℃, Tungsten (etching rate 340Å /
min: melting point 3382 ° C., titanium (etching rate 3
20Å / min: melting point 1725 ° C), silicon carbide (etching rate 320Å / min: melting point 2700 ° C or higher),
Alumina (etching rate 100Å / min: melting point 20
50 ℃, Vanadium (etching rate 340Å / mi
n: melting point 1890 ° C.) and the like. Of these, molybdenum and tungsten are preferable.

As a method of forming the film, for example, a method by sputtering, a vapor deposition method by an electron beam, a CV
D method, PVD method, etc. can be mentioned. The thickness of the film is usually 500 Å or more, preferably 1,0
It is more than 00Å. Thus, in this step, as shown in FIG. 3, for example, the pattern 2 made of the pattern forming material is formed on the surface of the substrate 1.

-Scratch Treatment Step-In the scratch treatment step, abrasive grains are used to form scratches which serve as nuclei for diamond precipitation on the entire surface of the substrate. The abrasive grains are not particularly limited as long as they are fine particles having a hardness higher than that of the substrate, and examples thereof include particles of SiC, CBN, diamond and the like. Among these, diamond grains are preferable.

The grain size of the abrasive grains is usually 0.5 to 500.
μm, and preferably 0.5 to 100 μm. If the particle size of the abrasive grains is not within the above range, the effect of scratching the substrate may not be sufficient, and a preferable nucleus for diamond precipitation may not be formed. In this case, the desired diamond cannot be obtained.

Although various methods can be selected to perform the scratching treatment using the abrasive grains, usually, the substrate is immersed in a liquid in which the abrasive grains are dispersed in a solvent, It can be performed by irradiating a sound wave. Examples of the solvent include alcohol and acetone. Further, as the amount of the abrasive grains dispersed in the solvent,
Usually, it is 0.05 to 10 g per 100 ml of solvent,
It is preferably 0.1 to 5 g.

The time for the scratching treatment is appropriately selected according to the purpose, but is usually 3 seconds to 1 hour. If the scratching time is too short, the proportion of nuclei for diamond generation is reduced, and even if diamond formation is subsequently performed, it may not be possible to obtain a diamond having a target shape and size. On the other hand, if it is too long, the subsequent etching process takes a long time, and diamond cannot be efficiently obtained.

When ultrasonic waves are applied in this scratching process, the abrasive grains violently contact the surface of the substrate. As a result, minute scratches can be made on the surface of the substrate. The minute scratches given to the surface of the pattern by this scratching process act as the generation points of initial diamond nuclei during diamond synthesis.

-Etching Treatment Step- In this etching treatment step, the substrate is etched by performing sputtering treatment or chemical treatment on the surface of the substrate. Various methods can be selected for performing the sputtering process on the substrate. For example, a method of applying a negative bias to the substrate side to RF discharge rare gas such as helium, neon, argon, xenon, or an ion beam method can be used.

Further, the chemical treatment of the substrate can be carried out under appropriate conditions by selecting chemicals for etching various substrates according to the purpose. The depth of the substrate to be etched is usually 100 to 5000Å, preferably 500 to 2000Å.

If this depth is less than 100 Å,
The scratches formed on the surface of the substrate may not be removed, and if it is deeper than 5000 Å, even the scratches formed on the surface of the pattern forming material may disappear.
In this etching process, when the substrate is etched, the exposed surface of the substrate is quickly etched,
The scratch formed on the surface disappears.

-Diamond forming step-In this diamond forming step, diamond is selectively formed on the surface of the pattern formed on the substrate. Diamond can be formed by various vapor phase synthesis methods such as the conventional vapor phase synthesis method, and among them, the CVD method is preferably adopted. Examples of the CVD method as the vapor phase synthesis method of the diamond film include, for example, microwave plasma CVD method, high frequency plasma CVD method, hot filament CVD method, DC arc plasma CVD method, and magnetic field plasma CVD method (including ECR method). A wide variety of methods are known.

Further, in such a gas phase synthesis method of diamond by the plasma CVD method, as a raw material gas,
It is known that various types and compositions of source gases containing at least a carbon source gas can be used. As the raw material gas, for example, a raw material gas containing a hydrocarbon as a carbon source gas such as a mixed gas of CH ₄ and H ₂ , a carbon compound other than a hydrocarbon such as a mixed gas of CO and H ₂ , is used. Various source gases such as a source gas contained as a source gas can be mentioned.

In the method of the present invention, if it is possible to form a diamond, various kinds of raw material gases such as the above-mentioned raw material gases and other conventional raw material gases used in the conventional method are appropriately used. Can be formed. Among them, mixed gas of CO and H ₂ , or CH ₄ and H
A mixed gas with ₂ is preferred. In particular, when a mixed gas of CO and H ₂ is used as a raw material gas, the diamond film deposition rate is faster than in the case of using a hydrocarbon, and high-purity diamond can be efficiently formed. Is excellent at.

As a particularly preferable example of the diamond forming method, a method of using CO and H ₂ as raw material gases will be described below. That is, in the method of the present invention, the diamond is formed particularly preferably by a method using a mixed gas of carbon monoxide and hydrogen gas described below as a source gas (hereinafter, this method is referred to as method I). It can be carried out. That is,
This method I is characterized in that a plasma gas obtained by exciting a mixed gas containing carbon monoxide and hydrogen at a ratio of 1% by volume or more of carbon monoxide is brought into contact with a substrate. .

In this method I, the carbon monoxide to be used is not particularly limited, and for example, the generator gas or water gas obtained by reacting coal or coke with air or steam at the time of heat is sufficiently purified. What was done can be used. There is no particular limitation on the hydrogen to be used, for example, those obtained by gasification of petroleum, natural gas, transformation of water gas, electrolysis of water, reaction of iron and steam, complete gasification of coal, etc. A sufficiently purified product can be used.

In this method I, carbon monoxide and hydrogen are used as raw material gases, and the content of carbon monoxide gas is 1
A gas obtained by exciting a mixed gas contained therein at a ratio of not less than 3% by volume, preferably not less than 3% by volume is brought into contact with the base material to deposit diamond on a predetermined surface thereof. If the content of the carbon monoxide gas in the mixed gas is less than 1% by volume, diamond is not formed, or even if diamond is formed, the deposition rate thereof is extremely low.

As a means for exciting the source gas to obtain the source gas containing excited carbon, a conventionally known method such as a plasma CVD method or a hot filament method can be used. When the plasma CVD method is used, the hydrogen forms plasma by irradiation with high frequency or microwave, and when the CVD method such as the hot filament method is used, the hydrogen forms atomic hydrogen by the hot filament. To do.

In this method I, an inert gas may be used as a carrier for the raw material gas. Specific examples of the inert gas include argon gas, neon gas, helium gas, xenon gas, nitrogen gas and the like. These may be used alone or in combination of two or more.

In this method I, the reaction proceeds under the following conditions to deposit diamond on the surface of the substrate.
That is, the temperature of the surface of the substrate cannot be unconditionally determined because it depends on the excitation means of the source gas, but when using the plasma CVD method, for example, it is usually
Room temperature to 1,200 ° C, preferably 450 ° C to 1,100
℃. If this temperature is lower than room temperature, the deposition rate of diamond may be slow, or excited carbon may not be generated. On the other hand, if the temperature is higher than 1,200 ° C., the diamond deposited on the surface of the substrate may be scraped off by etching, and the deposition rate may not be improved.

The reaction pressure is usually 10 ^-3 to 10 ³ t.
orr, preferably 1 to 800 Torr. When the reaction pressure is lower than 10 ⁻³ Torr, the diamond deposition rate becomes slow, or diamond does not precipitate. On the other hand, even if it is higher than 10 ³ Torr, an effect equivalent to that cannot be obtained. As described above, in the present invention, diamond can be selectively formed on the surface of the pattern formed on the surface of the substrate. Thereby, for example, a diamond as shown in FIGS. 1 and 2 can be obtained.

In the method of the present invention, of course, the diamond may be formed by applying a method other than the above method I. The thickness of the formed diamond may be appropriately set according to the purpose of use and the like, and there is no particular limitation in this sense, but usually 1 to 100.
It is preferable to select in the range of μm.

If this thickness is too thin, it may not be obtained as a diamond. On the other hand, if it is too thick, when the obtained diamond is applied to, for example, a diamond-coated member, it may not be obtained as a diamond. Peeling may occur. When the obtained diamond is used under severe conditions such as a cutting tool, it is usually preferable to select this thickness within the range of 5 to 100 μm.

[0041]

EXAMPLES Examples of the present invention will be specifically described below. The present invention is not limited to the following embodiments. (Example 1) -Pattern forming step-As a substrate, a low-resistance p-type Si substrate (resistivity ρ = 0.0
01-0.02 Ωcm) was used. A resist layer having a dot pattern of 3 μm square was formed on this substrate by a photolithography process.

That is, a positive type photoresist (OFPR-800 manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied by a spinner at 3 × 10 ³ rpm so that the thickness was 1 μm, and the surface of the substrate was coated. A resist layer was formed on. After coating, the resist layer was heated at 100 ° C. for 90 seconds and dried. Then, using a mask aligner (PLA-501FA) manufactured by Canon Inc., an ultraviolet ray of 13 mW is emitted.
The resist layer was exposed through a photomask having a dot pattern of 3 μm square for 90 seconds at an intensity of / cm ² . Subsequently, this substrate was immersed in NMD-3 manufactured by the same company for 60 seconds for development to remove the exposed portion of the resist layer, and then rinsed with pure water to form a resist layer.

Next, the surface of the substrate on which the resist layer was formed was processed by electron beam evaporation at room temperature to form a molybdenum film having a thickness of 3,000Å on the surface of the substrate. Subsequently, this substrate was immersed in acetone to dissolve the resist layer, and ultrasonic treatment was performed to remove the molybdenum film formed on the surface of the resist layer. Thus, a lattice-stripe-shaped pattern having a line width of 3 μm and an interval of 3 μm was formed on the substrate.

-Scratching treatment step-In an ultrasonic cleaning apparatus, 0.5 g of diamond particles having a particle diameter of 5 to 12 μm was dispersed in 100 ml of acetone, and a substrate on which a pattern was formed was dipped in this solution to perform a scratching treatment. Was carried out for 5 minutes. This caused fine scratches on the entire surface of the substrate.

-Etching treatment step-For the substrate subjected to the scratch treatment, a negative bias is applied to the substrate side, and argon gas is used for 15 minutes under the conditions of a pressure of 10 ^-2 Torr and an RF output of 300W. , RF
Discharged and sputtered. As a result, the scratches formed directly on the substrate surface by the scratching process were etched and eliminated.

-Diamond forming step-Diamond was formed under the following conditions. Type and flow rate of raw material gas: mixed gas of CO and H ₂ (10
/ 90 sccm) Synthesis conditions: reaction pressure 40 Torr, substrate temperature 900 ° C.,
Synthesis time 60 minutes Synthesis method (source gas excitation method): Microwave plasma CVD
Method (2.45 GHz). As a result, diamond was selectively formed only on the lattice-striped pattern of molybdenum on the substrate.

[0047]

According to the present invention, diamond suitable for a wide range of fields including high-performance semiconductor devices, field emitters, optical waveguides and other electronic equipment fields can be formed into a desired size and shape with high selectivity. It is possible to provide a selective formation method of diamond, which can be formed easily and easily with a simple operation.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing a state in which a substrate on which diamond is selectively formed is viewed from above.

FIG. 2 is a schematic explanatory view showing a state of a cross section of a substrate on which diamond is selectively formed.

FIG. 3 is a schematic explanatory view showing a state of a cross section of a substrate on which a pattern is formed.

FIG. 4 is a schematic explanatory view showing an example of a photomask.

FIG. 5 is a schematic explanatory diagram showing a state in which a resist layer coated on a substrate using a photomask is irradiated with ultraviolet rays.

FIG. 6 is a schematic explanatory view showing a state of a cross section of a substrate on which a resist layer is formed.

FIG. 7 is a schematic explanatory view showing a cross-sectional state of a substrate having a film formed on the surface of a resist layer.

FIG. 8 is a schematic explanatory view showing a state in which a resist layer applied on a film formed on the surface of a substrate is exposed to ultraviolet rays through a photomask.

FIG. 9 is a schematic explanatory view showing a cross-sectional state of a substrate having a resist layer formed on the film.

FIG. 10 is a schematic explanatory diagram showing a cross-sectional state of a substrate in which a resist layer is formed on a patterned matrix film.

[Explanation of sign]

 1 substrate 2 pattern 3 diamond 4 resist layer 5 photomask 6 film

Claims (1)

[Claims] 1. A pattern is formed on the surface of a substrate with a pattern forming material having an etching rate slower than that of the substrate material and having a melting point higher than the synthesis temperature of diamond, followed by scratching and etching. Selective formation method of diamond characterized by performing diamond synthesis by vapor phase method.