JP4949493B2 - N-type semiconductor diamond and method for producing the same - Google Patents

Description

  Diamond is a semiconductor having a band gap of 5.5 eV. If a diamond n-type semiconductor can be realized, a semiconductor element such as a MES field effect transistor (FET), a MIS field effect transistor, a PNP bipolar transistor, or an NPN bipolar transistor can be put into practical use. If FETs and bipolar transistors using diamond are realized, it is expected to be an electronic device that can operate in a high-frequency region and a high-power region far exceeding conventional semiconductors. (See Non-Patent Document 1)

Kaji et al., Applied Physics, Vol. 73, No. 3, 2004, pages 363-367

  However, it is technically difficult to dope a diamond with a group V element that serves as a donor, and a diamond n-type semiconductor that can be used practically has not yet been obtained. Conventionally, P (phosphorus) has been known as a donor impurity. However, even when a doping gas containing P was mixed into the source gas, P was hardly taken into the crystal. The doping efficiency is extremely low, and the diamond semiconductor produced by the prior art has not been put to practical use for electronic devices.

  The present invention has been made in view of such problems, and an object thereof is to realize a practical n-type semiconductor diamond having high doping efficiency.

The present invention has been made in order to achieve such a problem, and the invention according to claim 1 is provided.
Ming uses a source gas containing carbon and an As dopant gas so that the ratio of As to carbon C in the gas (As / (As + C)) is in the range of 2 ppm to 500,000 ppm (50%), and the microwave power is 350 W. Microwave plasma chemical vapor deposition (CVD) method in which the substrate surface temperature is in the range of 700 ° C. to 900 ° C. and the As flow rate is in the range of 1 micromole per minute to 750 micromole per minute. Thus, an n-type diamond is obtained by the invention.

Invention according to claim 2, The method of claim 1, as a dopant gas of the As, trimethyl arsenic _{((CH 3) 3 As,} TMAs), triethyl arsenic _{((C 2 H 5) 3} As, TEAs), tertiary butylarsine (tC ₄ H ₉ AsH ₂ ), arsine (AsH ₃ ), or a combination thereof is used.

The invention according to claim 3 uses the source gas containing carbon and the Sb dopant gas so that the ratio of Sb to carbon C in the gas (Sb / (Sb + C)) is in the range of 2 ppm to 500,000 ppm (50%). Microwave plasma chemistries in which the microwave power is in the range of 350 W to 750 W, the substrate surface temperature is in the range of 700 ° C. to 900 ° C., and the Sb flow rate is in the range of 1 micromole per minute to 750 micromole per minute. It is an invention of a method for producing semiconductor diamond characterized in that n-type diamond is obtained by a phase deposition (CVD) method.

Invention of claim 4, The method of claim 3, as a dopant gas of the Sb, trimethyl antimony _{((CH 3) 3 Sb,} TMSb), triethyl antimony _{((C 2 H 5) 3} Sb, TESb), dimethyl tertiary butyl antimony _{((CH 3) 2 (t} -C 4 H 9) Sb), one of tripropyl antimony _{(i-C 3 H 7)} 3 Sb) , or using a combination thereof Features.

  As described above, according to the present invention, by using As or Sb as an n-type dopant element of diamond, an n-type semiconductor of diamond that can be practically applied to an electronic device can be realized.

It is a figure which shows the microwave power dependence at the time of the growth of the room temperature electron mobility in the diamond thin film of Example 1. FIG. It is a figure which shows the substrate surface temperature dependence during the growth of the room temperature electron mobility in the diamond thin film of Example 1. FIG. It is a figure which shows the As flow rate dependence during the growth of the As atom density | concentration in the diamond grown in Example 1. FIG. It is a figure which shows the As concentration dependence in the gaseous phase at the time of the growth of As atom concentration in the diamond grown in Example 1. FIG. In Example 2, it is a figure which shows the Sb flow rate dependence during the growth of the Sb atom density | concentration in the grown diamond. In Example 2, it is a figure which shows the Sb density | concentration dependence in the gaseous phase at the time of the growth of the Sb atom density | concentration in the grown diamond. (A) is the table | surface which showed the electron mobility with respect to each dopant raw material in Example 1, and (b) showed the electron mobility with respect to each dopant raw material in Example 2. FIG.

  According to the present invention, a practical diamond n-type semiconductor can be realized by using As or Sb as an n-type dopant element of diamond. As a result, semiconductor devices such as MES type FET, MIS type field effect FET, PNP type bipolar transistor, and NPN type bipolar transistor using n type diamond as a part of the structure can be put into practical use. With the realization of FETs and bipolar transistors using diamond, it is expected to realize electronic devices that operate in a high-frequency region and a high-power region that far exceed conventional semiconductors. Hereinafter, detailed examples of the present invention will be described.

In this embodiment, a diamond single crystal (111) is produced by a microwave plasma chemical vapor deposition method using a reaction gas consisting of a flow rate ratio of methane gas (CH ₄ ): 1%, a dopant gas, and the balance H ₂ with a total flow rate of 300 ccm. ) A diamond semiconductor film of the present invention having a thickness of 1.0 μm was grown on the plane orientation. Here, the pressure in the reaction tube was 50 Torr, and the microwave source had a frequency of 2.45 GHz.

As dopant gases, trimethylarsenic ((CH ₃ ) ₃ As, TMAs), triethylarsenic ((C ₂ H ₅ ) ₃ As, TEAs), tertiary butylarsine (t-C), which are organometallic raw materials containing As, are used. ₄ H ₉ AsH ₂ ) and arsine (AsH ₃ ).

  When the hole measurement of the obtained diamond semiconductor film was performed, it was confirmed by the determination of the Hall coefficient that all the obtained diamond semiconductor films were n-type semiconductors. Furthermore, the As atom concentration in the obtained diamond semiconductor film was measured by SIMS measurement.

FIG. 1 is a graph showing the dependence of room temperature electron mobility in the diamond thin film of Example 1 on the microwave power during growth. The horizontal axis represents microwave power (W), and the vertical axis represents room temperature electron mobility (cm ² / (Vs)). When the microwave power was in the range of 350 W to 750 W, the mobility was about 200 cm ² / (Vs), indicating that n-type conduction was realized.

FIG. 2 is a diagram showing the substrate surface temperature dependence of the room temperature electron mobility in the diamond thin film of Example 1 during growth. The horizontal axis represents the substrate surface temperature (° C.), and the vertical axis represents room temperature electron mobility (cm ² / (Vs)). The substrate surface temperature was measured with a pyrometer. In the temperature range from 700 ° C. to 900 ° C., the mobility was about 200 cm ² / (Vs), indicating that n-type conduction was realized.

FIG. 3 is a diagram showing the As flow rate dependence during growth of the As atom concentration in the grown diamond. The horizontal axis represents the As flow rate (μmol / min), and the vertical axis represents the As atom concentration (cm ⁻³ ). An As atom concentration of 1 × 10 ¹⁵ cm ⁻³ was obtained at a flow rate of 1 μmol / min, and an As atom concentration of 2 × 10 ²¹ cm ⁻³ was obtained at a flow rate of 750 μmol / min. It is shown that n-type conduction was obtained at any flow rate. Compared with the prior art, the doping efficiency is much higher, and a practical n-type semiconductor diamond can be realized.

FIG. 4 is a diagram showing the As concentration (As / (As + C)) dependence in the gas phase during the growth of the As atom concentration in the grown diamond. The horizontal axis represents the As concentration represented by the formula (As / (As + C)), and the vertical axis represents the As atom concentration (cm ⁻³ ). An As concentration of 10 ¹⁵ cm ⁻³ was obtained when As / (As + C) was 2 ppm, and an As concentration of 1 × 10 ²² cm ⁻³ was obtained when As / (As + C) was 500,000 ppm (50%). It is shown that n-type conduction was also obtained in the concentration.

The room temperature electron mobility in each case of the As dopant raw material used in Example 1 is shown in the table of FIG. Here, the value of the electron mobility is shown in comparison with each dopant raw material under the condition that the As atom concentration is 1 × 10 ¹⁹ cm ⁻³ . The room temperature electron mobility was highest in TMAs and lowest in AsH _3, but showed n-type conduction in any As dopant raw material shown in the table.

In this example, a microwave plasma chemical vapor deposition method is used, and a flow rate ratio of methane gas (CH ₄ ): 1%, a dopant gas, and a residual gas of H _{2 is} used as a raw material with a total flow rate of 300 ccm as a (111) plane orientation. A diamond semiconductor film of the present invention having a thickness of 1.0 μm was grown on the diamond single crystal substrate. Here, the pressure in the reaction tube was 50 Torr, and the microwave source had a frequency of 2.45 GHz.

As dopant gases, trimethylantimony ((CH ₃ ) ₃ Sb, TMSb) containing Sb, triethylantimony ((C ₂ H ₅ ) ₃ Sb, TESb), dimethyl tertiary butyl antimony ((CH ₃ ) ₂ (t- C ₄ H ₉₎ Sb), tripropyl antimony _{(i-C 3 H 7)} 3 Sb) was used.

  When the hole measurement of the obtained diamond semiconductor film was performed, it was confirmed by the determination of the Hall coefficient that all the obtained diamond semiconductor films were n-type semiconductors. Further, the Sb atom concentration in the obtained diamond semiconductor film was measured by SIMS measurement.

Also in the present Example 2, the microwave power dependence at the time of growth of the room temperature electron mobility was the same result as that of Example 1 shown in FIG. In the microwave power range from 350 W to 750 W, the mobility increased to about 200 cm ² / (Vs), indicating that n-type conduction was realized.

The dependence of the room temperature electron mobility on the substrate surface temperature during growth was similar to the result of Example 1 shown in FIG. That is, in the temperature range from 700 ° C. to 900 ° C., the mobility increased to about 200 cm ² / (Vs), indicating that n-type conduction was realized.

FIG. 5 is a diagram showing the dependence of the Sb atom concentration in the grown diamond on the Sb flow rate during growth. The horizontal axis represents the Sb flow rate (μmol / min), and the vertical axis represents the Sb atom concentration (cm ⁻³ ). An Sb atom concentration of 1 × 10 ¹⁵ cm ⁻³ was obtained at a flow rate of 1 μmol / min, and an Sb atom concentration of 2 × 10 ²¹ cm ⁻³ was obtained at a flow rate of 750 μmol / min. It was shown that n-type conduction was realized at any flow rate. Compared with the prior art, the doping efficiency is much higher, and a practical n-type semiconductor diamond can be realized.

FIG. 6 is a graph showing the dependence of the Sb atom concentration in the grown diamond on the Sb concentration (Sb / (Sb + C)) in the gas phase during growth. The horizontal axis represents the Sb concentration represented by the formula Sb / (Sb + C), and the vertical axis represents the Sb atom concentration (cm ⁻³ ). When Sb / (Sb + C) was 2 ppm, an Sb concentration of 10 ¹⁵ cm ⁻³ was obtained, and when Sb / (Sb + C) was 500,000 ppm (50%), an Sb concentration of 1 × 10 ²² cm ⁻³ was obtained. It was shown that n-type conduction was realized at any Sb concentration.

FIG. 7B is a table showing a comparison result of room temperature mobility of the obtained n-type semiconductor film in each case of the Sb dopant gas used in Example 2. Here, the values of electron mobility are shown in comparison with each dopant raw material under the condition that the Sb atom concentration is 1 × 10 ¹⁹ cm ⁻³ . The electron mobility was highest for TMSb and lowest for tripropylantimony, but showed n-type conduction in any of the Sb dopant raw materials shown in the table.

In this example, a diamond thin film was produced by ion implantation using As as the dopant. Ion implantation was performed under the conditions of an acceleration voltage of 150 kV and an ion implantation amount of 10 ¹⁵ ion / cm ^2. As dopant was implanted into the diamond single crystal to produce As impurity-doped diamond. Thereafter, the obtained diamond thin film was annealed.

When the hole measurement of the obtained As-doped diamond semiconductor film of this example was performed, it was confirmed by determination of the Hall coefficient that the obtained As-doped diamond semiconductor film was an n-type semiconductor. Furthermore, the As dopant atom concentration in the diamond semiconductor film was measured by SIMS measurement. Also in this semiconductor thin film produced by the ion implantation method, each As dopant atom concentration of 1 × 10 ¹⁵ cm ⁻³ to 1 × 10 ²² cm ⁻³ was obtained. N-type conduction was exhibited at any As atom concentration. Compared with the prior art, the doping efficiency was much higher, and a practical n-type semiconductor diamond could be realized.

  Even in the case of forming a thin film by an ion implantation method using Sb as a dopant, the same results as those of As in Example 3 were obtained.

  In this example, a diamond semiconductor film was prepared by dissolving diamond powder mixed with As as a dopant in an Fe—Ni solvent.

  In this example, n-type diamond was obtained by the ultra-high temperature and high pressure method by placing the above-mentioned material under conditions of 5 GPa and about 1400 ° C. for 7 hours. When the hole measurement of the obtained n-type diamond semiconductor film was performed, it was confirmed by determination of the Hall coefficient that all the obtained diamond semiconductor films were n-type semiconductors.

Further, the dopant atom concentration in the diamond semiconductor film was measured by SIMS measurement. The room temperature hole concentration of As when the atomic concentration ratio (dopant atom / C) is kept constant at 0.01% is the case where P, which is a conventional technique, is used as a dopant (6.2 × 10 ¹² cm ^−3). ) Is 700 to 108000 times higher. Compared to the case of using P as a dopant in the prior art, when As is a dopant, incorporation of the dopant is very excellent.

Further, the room temperature hole mobility of As is 4.7 to 5.7 times as compared with the case of using B as a dopant in the conventional technique (200 cm ² / (Vs)). Regarding room temperature hole mobility, it was found that incorporation of dopant was very excellent when As was used as a dopant, compared to the case where B in the prior art was used as a dopant. Even when the dopant was Sb, the same result as that of As was obtained.

  As described above in detail, according to the present invention, by using As or Sb as an n-type dopant element of diamond, an n-type semiconductor of diamond that has a very high doping efficiency and is practically applicable to an electronic device can be obtained. Can be realized.

  The present invention relates to a semiconductor material. Specifically, the present invention can be used for electronic devices that operate in higher frequency regions and higher power regions.

Claims (4)

  Using a source gas containing carbon and an As dopant gas so that the ratio of As to carbon C in the gas (As / (As + C)) is in the range of 2 ppm to 500,000 ppm, the microwave power is in the range of 350 W to 750 W, Obtaining n-type diamond by microwave plasma chemical vapor deposition (CVD) method in which the substrate surface temperature is in the range of 700 ° C. to 900 ° C. and the As flow rate is in the range of 1 micromole per minute to 750 micromole per minute. A method for producing a semiconductor diamond. Examples of the dopant gas for As include trimethyl arsenic ((CH ₃ ) ₃ As, TMAs), triethyl arsenic ((C ₂ H ₅ ) ₃ As, TEAs), tertiary butylarsine (tC ₄ H ₉ AsH ₂ ), The method for producing n-type diamond according to claim 1 , wherein any one of arsine (AsH ₃ ) or a combination thereof is used.   Using a source gas containing carbon and an Sb dopant gas so that the ratio of Sb to carbon C in the gas (Sb / (Sb + C)) is in the range of 2 ppm to 500,000 ppm, the microwave power is in the range of 350 W to 750 W, Obtaining n-type diamond by microwave plasma chemical vapor deposition (CVD) method in which the substrate surface temperature is in the range of 700 ° C. to 900 ° C. and the Sb flow rate is in the range of 1 micromole per minute to 750 micromole per minute. A method for producing a semiconductor diamond. As the dopant gas of Sb, trimethylantimony ((CH ₃ ) ₃ Sb, TMSb), triethylantimony ((C ₂ H ₅ ) ₃ Sb, TESb), dimethyl tertiary butyl antimony ((CH ₃ ) ₂ (t-C) _{4. The} method for producing n-type diamond according to claim 3 , wherein any one of ₄ H ₉ ) Sb), tripropylantimony (i-C ₃ H ₇ ) ₃ Sb), or a combination thereof is used.

Images