JPH06151331A - Method and apparatus for formation of semiconductor diamond - Google Patents

Abstract

PURPOSE:To achieve that an impurity chemical element which forms a donor level and an acceptor level is introduced into a diamond with good controllability and to form a p-type semiconductor diamond and an n-type semiconductor diamond by a method wherein, while a diamond or a diamond thin film which has been deposited on a substrate blank is being irradiated with accelerated particles, it is exposed to an atmosphere containing hydrogen in a radical state or an ion state. CONSTITUTION:A diamond 1 is mounted on a substrate-holding stand 7, a vacuum is produced, boron ions (B<+>) which have been taken out from an ion source, as particles 2, are accelerated at 100keV, and, while the diamond 1 is being irradiated at 1X10<15>pieces/cm<2>, it is irradiated simultaneously with hydrogen ions at an ion current density of 0.01 to 0.1mA/cm<2> from a bucket-type ion source 14. Boron atoms are implanted into a region of about 0.3mum in the surface layer of the diamond 1, and a p-type semiconductor layer 4 which is not damaged and in which boron has been activated can be formed. When phosphorus ions are irradiated in the same manner, an n-type semiconductor diamond layer can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for forming semiconductor diamond used as a semiconductor material for environment-resistant elements in the electronic industry.

[0002]

2. Description of the Related Art In order to form diamond showing semiconductor characteristics, it is necessary to introduce an impurity element forming a donor or acceptor level into diamond. Generally, in the case of a group IV element semiconductor such as silicon or diamond, p-type or n-type conductivity control is performed by introducing a group III element such as boron or a group V element such as phosphorus or arsenic. It is considered possible. In natural diamond, the existence of p-type diamond containing boron is known. In addition, a CVD method (chemical vapor deposition method) for synthesizing diamond into a thin film by decomposing a raw material gas, which is a mixture of a carbon source gas such as methane or carbon monoxide, and hydrogen gas, with plasma, etc. A p-type film is obtained by adding boron.
However, neither natural diamonds nor those synthesized by the CVD method have sufficiently obtained n-type diamond.

[0003]

In order to form diamond showing semiconductor characteristics, it is necessary to dope an impurity element forming a donor or acceptor level. Up to now, boron-doped p-type natural and artificial synthetic diamonds have been obtained, but it has been difficult to control the impurity concentration thereof and to produce them with good reproducibility and uniformly. In addition, the n-type has not been obtained.

Further, although a method of introducing an impurity element by ion implantation has been attempted, the problem that diamond is damaged during the implantation and the damage is not removed by heat treatment but graphitized. There was a point.

As described above, the conventional method for forming a semiconductor diamond is insufficient in terms of controllability and the n-type has not been obtained. Therefore, a new forming method and an apparatus therefor are provided. Was needed.

In order to solve the above-mentioned conventional problems, the present invention provides a method and an apparatus for forming a p-type and an n-type semiconductor diamond by introducing an impurity element forming a donor or acceptor level into diamond with good controllability. The purpose is to provide.

[0007]

In order to achieve the above object, the method for forming a semiconductor diamond according to the first aspect of the present invention is to irradiate diamond or a diamond thin film deposited on a substrate material with accelerated particles. However, it is configured to be exposed to an atmosphere containing hydrogen in a radical state or an ionic state.

The semiconductor diamond forming method of the second invention of the present invention includes the step of irradiating a diamond or diamond thin film deposited on a substrate material with accelerated particles, and hydrogen in a radical state or an ionic state. It has a configuration in which the step of exposing to the atmosphere is alternately performed.

In the structure of the first or second invention, the particles to be irradiated are preferably particles containing at least a group III element or particles containing at least a group V element. Examples of the group III element include boron (B), aluminum (Al), gallium (Ga), indium (In), and the like, and examples of the group V element include phosphorus (P), arsenic (As), and antimony ( Sb) etc.

Further, in the structure of the first or second invention, it is preferable that the particles with which the substrate material is irradiated are in an ionic state. In the structure of the first or second invention, it is preferable that the diamond or the diamond thin film deposited on the substrate material is heated to a temperature of 500 ° C. or higher, or cooled to a temperature of −100 ° C. or lower.

Next, in the semiconductor diamond forming apparatus of the present invention, a mechanism for accelerating and irradiating particles on a diamond thin film deposited on a diamond or a substrate material held in a container and hydrogen in a radical state or an ionic state are used. Is formed and has a mechanism for introducing it into the container.

In the structure of the invention of the above-mentioned semiconductor diamond forming apparatus, there is provided a heating means capable of heating the diamond held in the container or the diamond thin film deposited on the substrate material, or a cooling means capable of cooling. It is preferable.

[0013]

[Function] By accelerating and irradiating the diamond or the diamond thin film deposited on the substrate material with particles containing an impurity element which is considered to form a donor or an acceptor, these particles are forcibly injected into the diamond. . As a matter of course, if only such implantation is performed, the diamond will be damaged (lattice defect), so that the diamond does not show the intended semiconductor characteristics. In addition, diamond has a very high melting point,
Thermal annealing, which is usually done with silicon, cannot sufficiently recover the damage, and graphitization occurs on the basis of the damage. That is, in order to introduce the target particles into the diamond and minimize the damage, it is necessary to remove and restore the damaged region at the same time as the irradiation of the particles or when the degree of damage is slight.

Therefore, according to the structure of the first aspect of the present invention, the diamond or the diamond thin film deposited on the substrate material is exposed to the atmosphere containing hydrogen in the radical state or the ionic state at the same time as the particle irradiation, so that they are extremely exposed. In addition to being active and highly reactive, graphitization of diamond is prevented, so that damage caused by particle irradiation can be recovered. Then, the impurity particles introduced at the same time are also replaced at the lattice positions, so that they are activated and exhibit semiconductor characteristics. At that time, the conductivity of diamond can be controlled by controlling the type and amount of irradiation of particles, and the irradiation amount of hydrogen radicals and ions.

According to the structure of the second aspect of the invention, the accelerated particles are irradiated by an amount that does not damage the diamond excessively, and then exposed to an atmosphere containing active hydrogen radicals and ions to remove the damage. The semiconductor diamond can be similarly formed by repeating the step of performing recovery.

According to the preferable constitution of the present invention in which the particles for irradiating the diamond or the diamond thin film deposited on the substrate material are particles containing at least a group III element, a p-type semiconductor diamond can be easily formed. It becomes possible to do.

Further, according to the preferable constitution of the present invention in which the particles for irradiating the diamond or the diamond thin film deposited on the substrate material are particles containing at least a group V element, an n-type semiconductor diamond can be easily formed. Can be formed.

Further, according to the preferable construction of the present invention in which ions are used as the state of the particles to be irradiated, it becomes easy to control the irradiation amount and irradiation energy of the irradiated particles. In addition, according to the preferable configuration of the present invention in which the diamond or the diamond thin film deposited on the substrate material is heated to a temperature of 500 ° C. or higher, the substitution of the impurity element is performed more efficiently.

Further, according to the preferable constitution of the present invention in which the diamond or the diamond thin film deposited on the substrate material is cooled to a temperature of −100 ° C. or lower, graphitization at the time of injection is suppressed, and therefore damage is caused. It becomes easy to remove and recover.

According to the third aspect of the present invention, the mechanism for accelerating and irradiating the diamond or the diamond thin film deposited on the diamond or substrate material held in the container with the radical state or the ionic state By having a mechanism of forming hydrogen and introducing it into the container, while controlling the introduction amount and the introduction depth of the impurity element, hydrogen radicals or hydrogen ions that promote graphitization are independently controlled and simultaneously irradiated. Therefore, damage recovery can be performed efficiently and effectively.

Further, according to the preferable constitution of the present invention, the heating means for heating the diamond held in the container or the diamond thin film deposited on the substrate material or the cooling means for cooling the diamond thin film is provided efficiently. The above effects can be obtained.

[0022]

EXAMPLES The present invention will be described below with reference to examples in order to facilitate understanding of the present invention. FIG. 1 is a diagram showing a state where a diamond (or a diamond thin film deposited on a substrate material) 1 is irradiated with accelerated particles 2 and exposed to an atmosphere 3 containing hydrogen in a radical state or an ionic state. At that time, the acceleration energy and the irradiation amount of the particle 2 are
50 eV to 5 MeV, 1 × 10 ¹⁴ to 1 × 10 ¹⁷ pieces / cm ^{2 respectively}
The range of 30 to 200 keV and 5 × 10 ¹⁴ is particularly preferable.
A range of up to 5 × 10 ¹⁵ pieces / cm ² is often used. In order to remove the damage generated in the diamond 1 irradiated with the particles 2 under the conditions as described above, a hydrogen ion flow, a radical flow, hydrogen plasma or the like is often adopted as the atmosphere 3 to be exposed. The atmospheric pressure at this time is
A region of 1 × 10 ⁻⁷ to 1 × 10 ⁻⁵ Torr is preferably adopted. As a result, the semiconductor diamond layer 4 in which the impurity element is introduced is formed on the surface layer of the diamond 1.

FIG. 2 shows a state in which a step of irradiating diamond (or a diamond thin film deposited on a substrate material) 1 with accelerated particles 2 and a step of exposing it to an atmosphere 3 containing hydrogen in a radical state or an ionic state are alternately performed. It is the figure which showed. The method of irradiating the diamond 1 with the accelerated particles 2 is the same as that used in the explanation of FIG. 1, but there is damage in the implantation region 5 generated only by the particle irradiation. Therefore, in order to suppress the damage density in the implantation region 5 to a recoverable level, the particle irradiation amount per cycle is preferably 1 × 10 ¹⁵ particles / cm ² or less. As in the first embodiment, the diamond 1 having the implantation region 5 with a slight degree of damage is used in the atmosphere 3 containing hydrogen in the radical state or the ionic state.
The exposure recovers the damage and the semiconductor diamond layer 4 is formed. Then, in order to finally set the implantation amount of the impurity element to a predetermined amount, the process of irradiating such particles and the process of exposing to an atmosphere containing hydrogen in a radical state or an ionic state are repeated.

The above process is realized by the apparatus having the configuration shown in the schematic diagram of FIG. This apparatus is equipped with a substrate holder 7 having a heating mechanism or a cooling mechanism for holding a diamond (or a diamond thin film deposited on a substrate material) 1 in a vacuum container 6. Vacuum container 6
A vacuum pump system 8 for drawing a vacuum inside the tank is connected to the. As the vacuum pump for performing the treatment in the above preferable atmospheric pressure range, a rotary pump,
A system that combines a turbo pump, an oil diffusion pump, a cryopump, etc. can be considered. Also, the particles to be irradiated 2
Is emitted from the particle source 9 and guided to the diamond 1 through the mass separation mechanism 10 and the particle acceleration mechanism 11. Examples of the particle source 9 include a microwave type ion source. The mass separation mechanism 10 is for extracting only the target element and efficiently introducing the element into the diamond 1.

The bucket type ion source 14 to which the hydrogen cylinder 12 and the mass flow meter 13 are connected has a function of exposing the diamond 1 to an atmosphere containing hydrogen in a radical state or an ionic state. In this method, hydrogen gas is turned into plasma by arc discharge and ions are accelerated at an arbitrary extraction voltage, and an atmosphere containing a large amount of hydrogen in an ionic state can be easily formed.

As a function of exposing the diamond 1 to the atmosphere 3 containing hydrogen in the radical state or the ionic state, the electron cyclotron resonance (ECR) for converting hydrogen gas into plasma by the magnetic field and the microwave as shown in FIG. ) There is a gas cell in which a gas is heated and dissociated by an ion source or a filament as shown in FIG. The ECR ion source includes a microwave power source 15, a waveguide 16 for guiding the microwave to the discharge chamber, a quartz window 17, and
It is composed of an electromagnet 18 that gives a magnetic field. The gas cell is composed of an introduction portion for introducing hydrogen to the vicinity of the diamond 1 and a filament 19 (tungsten or tantalum is often used as the material). In any case, an atmosphere containing a large amount of hydrogen in a radical state or an ionic state can be easily formed.

In the present invention, as particles to be irradiated, particles containing a group III element include, for example, boron (B), aluminum (Al), gallium (Ga), indium (In), etc. Particles containing a Group III element can also be used. Moreover, as the particles to be irradiated, for example, particles containing a group V element, such as phosphorus (P),
Although there are arsenic (As), antimony (Sb), and the like, particles containing a group V element other than these can also be used.

Specific examples will be described below. (Embodiment 1) First, the result of carrying out the method of the first invention using the apparatus shown in FIG. 3 will be described. The diamond 1 is installed on the substrate holder 7, and the vacuum chamber 6 is sufficiently evacuated by the vacuum pump system 8 so that the pressure is 1 × 1.
It was set to ^0-7 Torr or less. Then, as particles 2, boron ions (B ⁺ ) extracted from the ion source are
Accelerate to 100 keV and 1 × 10 15 diamonds / cm ² per diamond
While only irradiating, hydrogen ions with an ion current density of 0.01 to 0.1 mA / cm ² were simultaneously irradiated from the bucket type ion source 14. The acceleration voltage of hydrogen ions at this time is 1 to 10
It is about kV. As a result, the surface layer of diamond 1 is about 0.3
Boron atoms were implanted in the μm region, and the p-type semiconductor diamond layer 4 in which boron was activated without damage was formed.

On the other hand, when only boron ions were irradiated without hydrogen ion irradiation, the semiconductor diamond layer was not formed due to damage and low activation. By exposing the diamond to the hydrogen ion flow while irradiating the diamond with accelerated boron ions in this manner, the implanted boron enters the lattice position of the diamond structure to form the undamaged semiconductor diamond layer 4 having p-type electrical characteristics. Obtainable. When the same method was used for other ions such as aluminum and phosphorus, those having p-type or n-type electrical characteristics were obtained. Similar results were also obtained when electrically neutral particles were irradiated without using ions as a method of irradiating the impurity particles.

(Embodiment 2) Next, the results obtained by using the apparatus shown in FIG. 4 will be described. The method and procedure for irradiating the accelerated particles 2 are the same as in Example 1 above. While the diamond 1 installed on the substrate holder 7 in the vacuum vessel 6 which was sufficiently evacuated to a vacuum was irradiated with B ⁺ to 100 keV and irradiating 1 × 10 ¹⁵ pieces / cm ² , an ECR type ion source was used. Irradiated with hydrogen ions at the same time. The condition of the ECR ion source at this time was that the pressure inside the discharge chamber in which hydrogen gas was introduced was 1 × 1.
A microwave power of 300 W to 1.5 kW was applied at 0 ^-4 Torr, and a magnetic field was applied so that the discharge chamber satisfied the ECR condition (when the microwave frequency is 2.45 GHz, the magnetic field strength satisfying the ECR condition is satisfied). Is 875 gauss). Under these conditions, the applied power is absorbed most efficiently, so that more active hydrogen radicals or ions can be generated. Then, these hydrogen ions / radicals are automatically extracted from the ion source by the magnetic field or the pressure gradient and reach the vicinity of the diamond 1. In this way, as a result of exposing the diamond 1 to the particle irradiation and the atmosphere containing hydrogen in the radical state or the ionic state, the semiconductor diamond having the p-type electrical characteristics in which boron is activated without damage, as in the above-mentioned embodiment. Layer 4 was formed on the surface.

(Embodiment 3) Next, the results obtained by using the apparatus shown in FIG. 5 will be described. The method and procedure for irradiating the accelerated particles 2 are the same as in Example 1 above. Diamond 1
Then, while accelerating B ⁺ to 100 keV and irradiating 1 × 10 ¹⁵ cells / cm ² , hydrogen dissociated by heat from the gas-cell was simultaneously irradiated. The conditions of the gas-cell at this time are as follows: the ejection port is installed a few mm above the diamond 1 so that the active hydrogen is efficiently irradiated to the diamond 1, and the filament temperature is 1500 to 2800 ° C. Area. The flow rate of the hydrogen gas was set so that the pressure inside the vacuum container 6 would not be increased more than necessary. In this way, as a result of exposing the diamond 1 to the atmosphere containing hydrogen in the radical state dissociated by particle irradiation and heat, as in the above-mentioned embodiment, the diamond 1 has p-type electrical characteristics with no damage and activated boron. Semiconductor diamond layer 4
Was formed on the surface layer.

(Embodiment 4) The result of conducting the same experiment by heating the diamond 1 using the apparatus shown in FIG. First, the diamond 1 set on the substrate holder 7 was heated to 600 ° C. by the heating mechanism. Irradiation of accelerated particles and hydrogen ion treatment were performed in the same procedure as in Example 1 above. Diamond 1
By heating, the ratio of the irradiated particles 2 being replaced with the lattice positions at the same time as the injection is increased. However, on the other hand, graphitization is accelerated. Therefore, this graphitization was suppressed by irradiating more active hydrogen. That is, hydrogen ions were irradiated at a hydrogen ion current density (0.05 to 0.25 mA / cm ² ) higher than that of the conditions of Example 1. As a result, as before, 500 ℃
It was observed that by heating to the above temperature, the p-type semiconductor diamond layer 4 was formed on the surface layer of the diamond 1, and the activation rate of the introduced boron was improved.

(Embodiment 5) As in Embodiment 1, using the apparatus shown in FIG. 3, the diamond 1 is cooled and the result of a similar experiment will be described. First, the diamond 1 set on the substrate holder 7 was cooled to near liquid nitrogen temperature (-190C) by a cooling mechanism. Irradiation of accelerated particles and hydrogen ion treatment were performed in the same procedure as in Example 1 above. By cooling the diamond 1, the defects formed during particle irradiation do not diffuse, and graphitization is suppressed. Therefore, hydrogen ions were irradiated at a hydrogen ion current density (0.001 to 0.02 mA / cm ² ) smaller than that of the conditions of Example 1. As a result, -100 ℃ as before
It was observed that the p-type semiconductor diamond layer 4 was formed on the surface layer of the diamond 1 with a smaller amount of active hydrogen by cooling to the temperature below.

(Embodiment 6) The result of carrying out the second invention using the apparatus shown in FIG. 3 as in Embodiment 1 will be described. B ⁺ was irradiated with energy of 100 keV to the diamond 1 installed in the vacuum vessel 6 which was sufficiently evacuated. The dose amount per cycle is 2 in order to suppress the damage formation of the diamond 1 due to the boron ion irradiation as much as possible.
× 10 ¹⁴ pieces / cm ^2, and boron ion irradiation and hydrogen ion treatment were performed for a total of 5 cycles. The hydrogen ion irradiation conditions are the same as in Example 1. Further, the time of irradiation with hydrogen ions was 5 to 15 minutes per cycle. As a result, the introduction of the impurity element by the accelerated particles 2 and the damage recovery of the implantation region 5 by the hydrogen ion treatment are performed in one cycle, and even if these treatments are repeated for several cycles, the p-type conductivity similar to that in the first embodiment is obtained. It was confirmed that the semiconductor diamond layer 4 having the electric characteristics of and having no damage was formed on the surface layer of the diamond 1. Also, with respect to other ions, those having p-type or n-type electrical characteristics were obtained. According to this method, even when the mechanism for accelerating and irradiating particles in the same vacuum container 6 and the mechanism for forming hydrogen in a radical state or an ionic state are not provided as in FIG. 3, particle irradiation and hydrogen ion treatment are sequentially performed. It is shown that it becomes possible to form a good quality semiconductor diamond layer 4 by performing the above.

(Embodiment 7) The method carried out in the above embodiment was carried out on the polycrystalline diamond thin film 1 deposited on the silicon substrate by 10 μm by the microwave plasma CVD method. As a result, it was confirmed that the semiconductor diamond layer 4 was similarly formed on the surface layer of the diamond thin film 1.

[0036]

According to the first aspect of the present invention, it is possible to efficiently control the addition of impurities for imparting p-type or n-type semiconductor characteristics to diamond, which has been difficult in the past. Can be provided. This opens the possibility of manufacturing various devices using semiconductor diamond, and the industrial value of the present invention is extremely high, such as application to environment-resistant semiconductor elements.

Next, according to the second aspect of the present invention, after activating the diamond or the diamond thin film deposited on the substrate material with an amount of accelerated particles that does not cause excessive damage, the active hydrogen radicals are added. -Semiconductor diamond can be similarly formed by repeating the process of removing and recovering damage by exposing to an atmosphere containing ions, and at the same time, a mechanism for accelerating and irradiating particles in the same vacuum container and radical state Alternatively, the same effect can be obtained even when there is no mechanism for forming ionic hydrogen.

Next, according to the third aspect of the present invention, a mechanism for accelerating and irradiating particles on a diamond thin film deposited on a diamond or a substrate material held in a container and hydrogen in a radical state or an ionic state By having a mechanism for forming and introducing into the container, it is possible to simultaneously and independently irradiate hydrogen radicals or hydrogen ions that promote graphitization while controlling the introduction amount and the introduction depth of the impurity element. Therefore, damage recovery can be performed efficiently and effectively.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a state in which a particle is exposed to an atmosphere containing hydrogen in a radical state or an ionic state while irradiating accelerated particles according to an embodiment of the first aspect of the present invention.

FIG. 2 is a conceptual diagram showing a state in which the step of irradiating accelerated particles and the step of exposing to an atmosphere containing hydrogen in a radical state or an ionic state are alternately performed according to the second embodiment of the present invention.

FIG. 3 is a schematic view of an apparatus according to an embodiment of the third invention of the present invention.

FIG. 4 is a schematic view of an apparatus according to another embodiment.

FIG. 5 is a schematic view of an apparatus according to another embodiment.

[Explanation of symbols]

1 Diamond thin film deposited on diamond or substrate material 2 Particles 3 Atmosphere containing hydrogen in radical or ionic state 4 Semiconductor diamond layer 5 Injection region 6 Vacuum container 7 Substrate holder 8 Vacuum pump system 9 Particle source 10 Mass separation mechanism 11 Particle acceleration mechanism 12 Hydrogen cylinder 13 Mass flow meter 14 Bucket type ion source 15 Microwave power source 16 Waveguide 17 Quartz window 18 Electromagnet 19 Filament

Claims (10)

[Claims] 1. While irradiating accelerated particles to a diamond or diamond thin film deposited on a substrate material,
A method for forming a semiconductor diamond, which comprises exposing to an atmosphere containing hydrogen in a radical state or an ionic state. 2. A semiconductor diamond comprising the steps of irradiating a diamond or diamond thin film deposited on a substrate material with accelerated particles and exposing the diamond thin film to an atmosphere containing hydrogen in a radical state or an ionic state alternately. Forming method. 3. The method for forming a semiconductor diamond according to claim 1, wherein the particles to be irradiated are particles containing at least a group III element. 4. The method for forming a semiconductor diamond according to claim 1, wherein the particles to be irradiated are particles containing at least a Group V element. 5. The method for forming a semiconductor diamond according to claim 1, wherein the particles to be irradiated are in an ionic state. 6. The method for forming a semiconductor diamond according to claim 1, wherein the diamond or the diamond thin film deposited on the substrate material is heated to a temperature of 500 ° C. or higher. 7. The method for forming a semiconductor diamond according to claim 1, wherein the diamond or diamond thin film deposited on the substrate material is cooled to a temperature of −100 ° C. or lower. 8. A mechanism for accelerating and irradiating particles and hydrogen in a radical state or an ionic state are formed on a diamond thin film held in a container or a diamond thin film deposited on a substrate material and introduced into the container. A semiconductor diamond forming apparatus including at least a mechanism. 9. The semiconductor diamond forming apparatus according to claim 8, further comprising heating means for heating the diamond held in the container or the diamond thin film deposited on the substrate material. 10. The semiconductor diamond forming apparatus according to claim 8, further comprising cooling means for cooling the diamond held in the container or the diamond thin film deposited on the substrate material.