JP4828089B2 - Method for producing diamond film - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a diamond film and a diamond film.
[0002]
[Prior art]
A material in which a diamond film is formed on a substrate by utilizing the unique properties of diamond has been widely studied. For example, an exposure mask member, a surface acoustic wave (SAW) device substrate, and a grinding / polishing tool in lithography technology used in manufacturing semiconductor devices.
[0003]
In recent years, diamond films have been attracting attention as mask membranes in X-ray lithography and electron beam lithography that can form ultrafine patterns of 100 nm or less using properties such as high Young's modulus, etching resistance, and high energy beam irradiation resistance. Has been.
[0004]
As a method for producing a diamond film, a method of depositing on a substrate by a gas phase reaction using a DC arc discharge, a DC glow discharge, a combustion flame, a high frequency (RF), a microwave, a hot filament or the like as an energy source. Among these manufacturing methods, the microwave CVD method and the hot filament CVD method are generally used because a film having a large area and good crystallinity can be formed.
[0005]
By the way, the raw material gas used in the method of depositing on the substrate by the gas phase reaction is generally a mixed gas obtained by diluting a carbon-containing gas such as methane, ethylene, acetylene, carbon monoxide or the like with hydrogen gas. The electrical resistivity of a diamond film obtained by performing a gas phase reaction using this hydrogen-diluted carbon-containing gas as a source gas is in the range of 10 ⁹ to 10 ¹⁵ Ω · cm.
[0006]
When a diamond film exhibiting an electrical resistivity in such a range is used as a lithography mask, particularly an X-ray or electron beam lithography mask, it is necessary to perform defect inspection by irradiating an electron beam. In some cases, the resistance is too high, and charged particles are accumulated to easily cause a charge-up phenomenon, so that such defect inspection cannot be performed quickly and accurately.
[0007]
Also, when actually used as a mask for electron beam lithography, if the resistance is high, a problem arises in transfer due to charge-up.
[0008]
In order to avoid such a charge-up phenomenon, a dopant gas such as diborane (B ₂ H ₆ ) or phosphine (PH ₃ ) is used when the diamond film is formed in order to reduce the electrical resistivity of the diamond film. It has been proposed to perform a gas phase reaction by adding to the hydrogen-diluted carbon-containing gas.
[0009]
Specifically, when B ₂ H ₆ is added as a boron doping source to hydrogen-diluted methane gas that is a raw material gas, the raw material mixed gas is introduced into a chamber, and a gas phase reaction is performed to produce a P-type diamond film. It has been reported that the value of electrical resistivity of the diamond film can be reduced to 10 ⁻² Ω · cm (see Non-Patent Document 1).
[0010]
[Non-Patent Document 1]
K. Marumoto, Jpn. J. et al. Appl. Phys. , 31 (1992) 4205-4209)
[0011]
[Problems to be solved by the invention]
However, when B ₂ H ₆ is used as a boron doping source as described above, since the allowable concentration is 0.1 ppm, there is a concern about the influence on the human body. Also, when PH ₃ is used as a phosphorus doping source, the allowable concentration is 0.3 ppm, and there is a concern about the influence on the human body. That is, in the dope using these gases, slight leakage is not allowed. Furthermore, since it has not only an influence on the human body but also explosiveness, there is a problem in handling. Therefore, in the dope using these gases, it is necessary to provide a device having no explosion and an explosion-proof function, which greatly increases the equipment cost.
[0012]
For the purpose of avoiding such problems, a method of vaporizing a solution of B ₂ O ₃ dissolved in methanol, ethanol, acetone, etc., adding it to a hydrogen-diluted carbon-containing gas, and adding boron as a raw material mixed gas is also proposed. However, there are problems in that it is difficult to produce a uniform solution and to control the temperature of the solution, and it is difficult to obtain a uniform diamond film with good reproducibility.
[0013]
The present invention has been made in view of such problems, and has a low electrical resistivity, which is less likely to cause adverse effects on the human body and handling hazards such as explosion in the dope process, and is easily and reproducibly uniform. It aims at providing the method which can manufacture a film | membrane at low cost.
[0014]
[Means for Solving the Problems]
The present invention has been made to solve the above-described problems. At least, in a method for producing a diamond film on a substrate by a gas phase reaction by introducing a raw material gas, B (OC ₂ H) is used as a boron doping source. ₅ ) Provided is a method for producing a diamond film characterized by including ₃ gases in the raw material gas and depositing a boron-doped diamond film on a substrate by a gas phase reaction using the raw material mixed gas. .
[0015]
Thus, if B (OC ₂ H ₅ ) ₃ gas is used as a boron doping source, boron can be easily and uniformly doped, and the electrical resistivity of the obtained diamond film can be reduced. That is, B (OC ₂ H ₅ ) ₃ gas has little risk of handling such as adverse effects on the human body or explosion, and can easily and uniformly dope boron into the diamond film. Is possible. Therefore, when this diamond film is used as a mask for lithography, for example, it is possible to avoid the charge-up phenomenon by defect inspection using an electron beam, and it is inexpensive because a special device for safety measures is unnecessary. Can be.
[0016]
In this case, the volume concentration of B (OC ₂ H ₅ ) ₃ gas contained in the source gas with respect to the total source gas is set to 0 vol. % And 10 vol. The concentration is preferably in the range of% or less .
[0017]
Thus, the volume concentration of B (OC ₂ H ₅ ) ₃ gas contained in the source gas with respect to the total source gas is set to 0 vol. % And 10 vol. By setting the concentration within the range of% or less, the electrical resistivity can be set to a desired value while maintaining high crystallinity of diamond.
[0018]
In this case, the doping of the boron is preferably adjusted so that the electric resistivity of the diamond film is 10 ⁷ Ω · cm or less in the range 20 ° C..
[0019]
Thus, if the boron doping is adjusted so that the electrical resistivity of the diamond film is in the range of 10 ⁷ Ω · cm or less at 20 ° C., the diamond film is made into a lithography mask, particularly X-ray or electron beam lithography. When used for a mask, the charge-up phenomenon can be reliably avoided in the defect inspection using the electron beam of the mask, so that the defect inspection can be performed quickly and accurately. Therefore, a high quality diamond mask for lithography can be easily produced using this diamond film.
Further, when this mask is actually used as an electron beam lithography mask, the charge-up phenomenon can be avoided, so that highly accurate transfer can be performed with high efficiency.
[0020]
In this case, when a diamond film is produced on the base material, only a part of the layer is formed while adding B (OC ₂ H ₅ ) ₃ gas to the source gas, and the other layers are source gas It can be formed without adding B (OC ₂ H ₅ ) ₃ gas .
[0021]
In this way, only a part of the layer is formed while adding the B (OC ₂ H ₅ ) ₃ gas to the source gas, and the other layer uses B (OC ₂ H ₅ ) ₃ gas in the source gas. By forming without addition, the amount of B (OC ₂ H ₅ ) ₃ gas used can be reduced, so that a diamond film having desired characteristics can be obtained while minimizing the decrease in crystallinity of diamond, Cost reduction can also be achieved.
[0022]
In particular, a part of the layer formed while adding the B (OC ₂ H ₅ ) ₃ gas is formed on the whole surface or a part of the surface of the diamond film, and is formed in a thickness range of 20 μm or less. Is preferable .
[0023]
In this way, the problem of the charge-up phenomenon can be sufficiently solved by the low electrical resistivity diamond formed on the entire surface or a part of the surface of the diamond film. That is, when the diamond film is used as a mask for lithography, for example, the problem is a charge-up phenomenon in which charges are accumulated on the surface of the diamond film irradiated with the electron beam. This problem can be solved by reducing the resistivity within the range of the surface thickness of 20 μm or less. Also, the bulk part can maintain good crystallinity, and the diamond film as a whole can be of very high quality.
[0024]
Furthermore, according to the present invention, there is provided a diamond film manufactured by the above manufacturing method and uniformly doped with boron . Further, this diamond film has a low electrical resistivity, and can be used as a mask substrate that is unlikely to cause a charge-up phenomenon during defect inspection or when actually used .
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, although embodiment of this invention is described, this invention is not limited to these.
The present inventor can be a diamond film having a reduced electrical resistivity, and there are few problems of handling danger such as a huge adverse effect on the human body and explosion in the dope process, and it is easily and uniformly reproducible, In order to produce a diamond film having a low electrical resistivity, it was conceived that B (OC ₂ H ₅ ) ₃ may be used as a boron doping source when forming vapor-phase synthetic diamond, and the present invention was completed. It has been made.
[0026]
Here, FIG. 1 is a schematic diagram showing a microwave CVD apparatus in which a vaporization supply apparatus for B (OC ₂ H ₅ ) ₃ is installed in a microwave CVD apparatus which is a typical diamond film manufacturing apparatus.
[0027]
In this microwave CVD apparatus 1, a base plate 5 on which a heating body such as a heater is mounted is disposed in a chamber 4 having a gas introduction pipe 2 and a gas discharge pipe 3. A microwave power source 6 is connected to the microwave introduction window 8 via the waveguide 7 so that plasma can be generated in the chamber 4. Further, each gas supply device is connected upstream of the gas introduction pipe 2, and includes a hydrogen gas supply tank 14, a carbon-containing gas supply tank 15, and B (OC ₂ H ₅ ) ₃ used particularly in the present invention. A gas supply device 9 is installed. The feed device 9, the liquid _{B (OC 2} H _{5) 3} of the tank 10, which is liquid at room temperature _{B (OC 2} H _{5) 3} Heater 11 for vaporizing and precisely B _(OC 2 _{H 5,} ) A mass flow controller 12 for controlling the flow rate of ₃ is provided.
[0028]
Hereinafter, when a raw material gas is introduced and a diamond film is produced on a substrate by a gas phase reaction, a diamond film is produced by adding B (OC ₂ H ₅ ) ₃ gas to the raw material gas as a boron doping source. The method will be described with reference to FIG.
[0029]
First, when the diamond film is formed on the base material 13, the presence of diamond particles on the surface of the base material can increase the nucleation density of diamond and facilitate the formation of a gas phase synthetic diamond film. . Therefore, in order to obtain a thin but uniform continuous film, the diamond particles are applied to the substrate surface by applying a diamond suspension to the substrate surface, ultrasonic treatment with the diamond suspension, scratch treatment with the diamond particles, and the like. It is effective to perform pre-treatment for seeding.
[0030]
For example, diamond is formed on the pretreated substrate by a gas phase reaction using, for example, a DC arc discharge, a DC glow discharge, a combustion flame, a high frequency (RF), a microwave, a hot filament as an energy source. Although a film can be manufactured, the microwave CVD method and the hot filament CVD method are particularly preferable because a film having a large area and good crystallinity can be formed on a substrate for forming a diamond film.
[0031]
In FIG. 1, the microwave CVD method is used as an example of these vapor phase synthesis methods.
First, the base material 13 pretreated as described above is placed on the base plate 5, and then the inside of the chamber 4 is evacuated by a rotary pump (not shown) and depressurized to 10 ⁻³ Torr or less.
[0032]
Next, a main constituent raw material gas having a desired flow rate, for example, a carbon-containing gas such as methane, ethylene, acetylene, or carbon monoxide is supplied from the carbon-containing gas supply tank 15 and diluted with hydrogen gas supplied from the hydrogen gas supply tank 14. A raw material mixed gas obtained by adding a predetermined concentration of B (OC ₂ H ₅ ) ₃ gas defined in the present invention to the raw material gas is introduced into the chamber 4 from the introduction pipe 2.
[0033]
At this time, the volume concentration of B (OC ₂ H ₅ ) ₃ gas contained in the source gas with respect to the total source gas is set to 0 vol. % And 10 vol. The concentration is preferably in the range of% or less. For example, a diamond film obtained by performing a gas phase reaction using only a raw material gas obtained by diluting a carbon-containing gas such as methane, ethylene, acetylene, or carbon monoxide with hydrogen gas has an electric resistivity of 10 ⁹ to 10 ¹⁵ Ω · cm. In the range of 0 vol. If the gas phase reaction is performed using a raw material mixed gas to which B (OC ₂ H ₅ ) ₃ gas is added in excess of%, the electric resistivity value of the obtained diamond film can be drastically reduced. It can be set to 10 ⁷ Ω · cm or less at ° C. In addition, 10 vol. By controlling the concentration of B (OC ₂ H ₅ ) ₃ gas in the range of% or less, it is possible to ensure that the electrical resistivity is set to a desired value while maintaining high crystallinity. On the other hand, the concentration of B (OC ₂ H ₅ ) ₃ gas is 10 vol. If it exceeds 50%, the boron concentration in the diamond film becomes saturated, and doping with a boron concentration exceeding that is difficult, and even if possible, the crystallinity is greatly lowered, and the occurrence of defects may increase.
[0034]
Next, after adjusting the valve of the gas exhaust pipe 3 to set the inside of the chamber 4 to 20 Torr, a microwave is applied from the microwave power source 6 and the waveguide 7 to generate plasma in the chamber 4, thereby generating a plasma on the substrate 13. A diamond film is formed.
At this time, in order to adjust the film stress of the diamond film may be heated by a heater of a sintered SiC heater or the like is a built-in substrate 13, for example the substrate stage 5.
[0035]
Depending on the use conditions of the diamond film, it may not be necessary to use all the diamonds in the diamond film as boron-doped diamond. In this case, when producing the diamond film on the substrate, only a part of the layer is formed while adding B (OC ₂ H ₅ ) ₃ gas to the source gas, and the other layers are in the source gas. Can be formed without adding B (OC ₂ H ₅ ) ₃ gas. As a result, the amount of B (OC ₂ H ₅ ) ₃ gas used can be reduced, crystallinity deterioration can be minimized, and costs can be reduced.
[0036]
In particular, when a diamond film is inspected by a defect inspection that irradiates an electron beam, or when it is actually used as an electron beam mask, the surface of the diamond film that is irradiated with an electron beam (the interface side with the substrate) Since a charge-up phenomenon in which electric charges are accumulated is a problem, some layers formed while adding B (OC ₂ H ₅ ) ₃ gas are deposited on the entire surface of the diamond film by the initial deposition of the CVD reaction. Alternatively, it is preferably formed on a part of the surface and formed in a thickness range of 20 μm or less, for example, 1 μm. In this way, charge accumulation can be prevented more effectively. In addition, other parts of the diamond film (deposition by subsequent CVD reaction), especially the bulk part, can be made of high-purity diamond, so the diamond has excellent high Young's modulus, etching resistance, high energy beam irradiation resistance, etc. The characteristics can be used as they are. Even at the end of the CVD reaction, B (OC ₂ H ₅ ) ₃ gas may be introduced to lower the resistivity of the surface on the opposite side of the diamond film.
[0037]
In this way, by using B (OC ₂ H ₅ ) ₃ instead of B ₂ H ₆ and PH ₃ that are generally used in the past, the dope source has a huge adverse effect on the human body or explosion in the dope process. The problem of handling danger is reduced, and no special equipment for safety measures is required. In addition, it is easier, more reproducible, and uniformly doped than a solution obtained by evaporating B ₂ O ₃ used in terms of safety with methanol, ethanol, acetone or the like and evaporating a solution. It becomes possible.
[0038]
Further, by adjusting the concentration of B (OC ₂ H ₅ ) ₃ gas added to the source gas, the value of the electrical resistivity of the diamond film to be generated can be controlled. In particular, if the diamond film is adjusted to have an electric resistivity value of 10 ⁷ Ω · cm or less, it is necessary to use the diamond film as a lithography mask, particularly an X-ray or electron beam lithography mask. In the defect inspection, the charge-up phenomenon can be surely avoided. Therefore, a high quality diamond mask for lithography can be manufactured. In addition, even when actually used as a diamond mask for electron beam lithography, the charge-up phenomenon can be avoided, so that high-precision transfer can be performed with high efficiency, further increasing the precision and integration of semiconductor devices. Can be achieved.
[0039]
Hereinafter, specific examples of the present invention will be described in detail.
( Specific example )
A double-side polished single crystal silicon wafer having a diameter of 100 mm, a thickness of 2 mm, and an orientation <100> is prepared as a base material, and pretreatment is performed in order to improve the nucleation density of diamond. First, the substrate was vacuum-adsorbed on a spin coater, and 50 ml of a suspension of diamond particles (average particle size 50 nm cluster diamond) was dropped on the surface. The wafer is 3000 r. p. m. For 30 seconds to make a uniform suspension of diamond particles on the surface. Thereafter, it was naturally dried to form a diamond seeding layer on the surface of the substrate. After the above pretreatment, the substrate was set on the substrate table in the chamber of the microwave CVD apparatus shown in FIG.
[0040]
Next, after exhausting to a reduced pressure of 10 ⁻³ Torr or less with a rotary pump, a raw material mixed gas composed of methane gas, hydrogen gas, and B (OC ₂ H ₅ ) ₃ gas was supplied from a gas introduction pipe. Each gas was introduced into the chamber at 40.0 sccm for methane gas, 930.0 sccm for hydrogen gas, and 30.0 sccm for B (OC ₂ H ₅ ) ₃ gas, and the volume ratio was methane gas / hydrogen gas / B (OC ₂ H ₅ ) ₃ gas = 4.0 / 93.0 / 3.0. After that, the valve of the gas discharge pipe was adjusted to set the inside of the chamber to 20 Torr, a 3000 W microwave was applied to generate plasma, and a boron-doped diamond film was formed on the substrate for 7 hours.
At the time of film formation, the substrate generated heat by microwave absorption, and the surface temperature reached 860 ° C.
[0041]
The boron-doped diamond film thus obtained was finished by polishing. In the 35 mm square area of the center of the base material, the film thickness was 2.0 μm ± 0.1 μm, the stress was 90 MPa ± 13 MPa, the surface roughness was 2 nm in Ra, and it was at a high practical level. Moreover, there is almost no variation between the film forming batches, which is extremely advantageous in practice.
[0042]
Further, this diamond film-formed substrate was processed into an electron beam lithography mask substrate, and a stencil-type electron beam lithography mask was produced using the mask substrate. Next, when the value of the electrical resistivity of the diamond film was measured, it was 0.8 Ω · cm, and no charge-up phenomenon occurred even when the mask was inspected for defects. Further, even when actually used as a mask for electron beam lithography, there was no charge-up phenomenon and stable and highly accurate transfer was possible.
[0043]
(Comparative Example 1)
Other added to dope source as B (OC ₂ H _{5) 3} solution of B ₂ O ₃ with ethanol without a gas by vaporizing the raw material gas, manufacturing a diamond film in the same manner as in Example 1 Filmed. That is, the same level of crystallinity (confirmed by Raman spectroscopic analysis) and electrical resistivity (by four-terminal method) as in Example 1 were applied to the surface of the base material that had been pretreated by spin-coating a diamond suspension on a silicon wafer. Gas mixture conditions (methane gas / hydrogen gas / B ₂ O ₃ = 1.0 / 97.0 / 2.0 vol.%) Of a gas composition for obtaining a diamond of (confirmation) were introduced into a chamber and a microwave of 3000 W at 20 Torr. Was applied to generate plasma, and a boron-doped diamond film was formed on the substrate for 13 hours. After that, the diamond film obtained by polishing was reduced in electrical resistivity to 30 Ω · cm, but the film thickness in the 35 mm square region of the center of the substrate was 2.0 μm ± 0.5 μm, and the stress was 187 MPa ± 77 MPa. It was bad.
[0044]
In addition, a change in the concentration of the B ₂ O ₃ solution is observed as the ethanol solution of B ₂ O ₃ is used, and temperature control during the process is strictly required. A diamond film that is uniformly doped in-plane and between batches is formed. It was extremely difficult to obtain. Furthermore, a large amount of B ₂ O ₃ produced particles adheres, which is disadvantageous from the viewpoint of suppressing the occurrence of defects.
[0045]
(B ₂ H ₆ dope)
In the case where a diamond film having the same level of characteristics is formed using B ₂ H ₆ gas without using B (OC ₂ H ₅ ) ₃ gas as a doping source, first, safety measures for the apparatus to be prepared are the first embodiment. It is completely different from the case of. That is, the allowable concentration of B ₂ H _{6 in} the human body is 0.1 ppm, and the explosion limit is 0.9 to 98.0 vol. %, And it has an extremely high explosive property, and therefore, the B ₂ H ₆ leakage countermeasure equipment is enormously expensive. Further, in order to actually obtain the same level of conductivity as in Example 1, B ₂ H ₆ was set to several vol. %, Which is a very dangerous concentration.
After all, considering economics, safety, and the characteristics of the resulting diamond, it was not so practical, so we abandoned the comparative experiment.
[0046]
The present invention is not limited to the above embodiment. The above-described 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 any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.
[0047]
For example, the application of the diamond film of the present invention has been described mainly for use in a mask member for X-ray or electron beam lithography, but the present invention is not limited to this application.
[0048]
【The invention's effect】
As described above, according to the present invention, B (OC ₂ H ₅ ) ₃ is used as a doping source instead of B ₂ H ₆ and PH ₃ that are generally used in the past. Handling hazards such as adverse effects on human bodies and explosions are reduced, and special equipment for safety measures is not required. In addition, it is easier, more reproducible, and uniformly doped than a solution obtained by evaporating B ₂ O ₃ used in terms of safety with methanol, ethanol, acetone or the like and evaporating a solution. It becomes possible.
[0049]
In this way, if B (OC ₂ H ₅ ) ₃ is used and the boron doping amount is adjusted so that the electrical resistivity of the diamond film is 10 ⁷ Ω · cm or less, the diamond film can be used as a lithography mask. The charge-up phenomenon can be reliably avoided in the defect inspection of the mask that is required when using the mask for X-ray or electron beam lithography. Therefore, a high quality diamond mask for lithography can be manufactured. Further, even when actually used as a diamond mask for electron beam lithography, the charge-up phenomenon can be avoided, so that highly accurate transfer can be performed with high efficiency.
[Brief description of the drawings]
FIG. 1 is a schematic view of a microwave CVD apparatus used in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Microwave CVD apparatus, 2 ... Gas introduction pipe, 3 ... Gas discharge pipe,
4 ... Chamber, 5 ... Base plate, 6 ... Microwave power source, 7 ... Waveguide,
8 ... microwave introduction _{window, 9 ... B (OC 2 H} 5) 3 supply system,
_{10 ... B (OC 2 H 5} ) 3 tank, 11 ... heater,
12 ... Mass flow controller, 13 ... Base material,
14 ... Hydrogen gas supply tank, 15 ... Carbon-containing gas supply tank.

Claims (5)

In a method for producing a diamond film on a substrate by introducing a source gas at least by vapor phase reaction, B (OC ₂ H ₅ ) ₃ gas is contained in the source gas as a boron doping source, and the source mixture is mixed When depositing a boron-doped diamond film on a base material by a gas phase reaction using a gas and producing the diamond film on the base material, B (OC ₂ H ₅ ) ₃ gas is contained in the source gas. Only a part of the layer is formed while the other layer is formed without adding B (OC ₂ H ₅ ) ₃ gas into the source gas, and the part of the layer is formed on the entire surface of the diamond film. Alternatively, a method for producing a diamond film , which is formed on a part of the surface and having a thickness of 20 μm or less . The volume concentration of B (OC ₂ H ₅ ) ₃ gas contained in the source gas with respect to the total source gas is 0 vol. % And 10 vol. The method for producing a diamond film according to claim 1, wherein the concentration is in a range of not more than%. 3. The method for producing a diamond film according to claim 1, wherein the boron doping is adjusted so that the electrical resistivity of the diamond film is in a range of 10 ⁷ Ω · cm or less at 20 ° C. 3. A diamond film produced by the method according to any one of claims 1 to 3 . A mask substrate using the diamond film according to claim 4 .

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