JP2004284924A - Method of processing diamond base surface and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of processing a diamond base surface capable of enlarging the range of application by enhancing the positive hole areal density of the diamond surface, and to provide a semiconductor device. <P>SOLUTION: In the method of processing the diamond base surface, by exposing the surface of the diamond base to a plasma comprised of a mixed gas of hydrogen and fluorine sulfide (SF<SB>6</SB>), the surface conductivity hole areal density of the diamond base is enhanced to 8×10<SP>13</SP>/cm<SP>2</SP>or more. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for treating the surface of a diamond substrate and a semiconductor device obtained by the method, and more particularly, to the field of manufacturing a wide band gap semiconductor having a large energy gap, the field of semiconductor surface treatment, and the field of semiconductor devices. It deals with high-temperature and high-power power devices, as well as radiation-resistant environment and space devices. In recent years, with the rise of bioelectrochemistry, expectations for environmental applications using the electrochemical catalyst mechanism on thin film surfaces are increasing. However, the present invention, which can effectively utilize surface electric conduction and surface electric field, is deeply involved in this field. Things.
[0002]
[Prior art]
There are almost no examples in which electrically conductive carriers naturally accumulate on the surface of a semiconductor. However, diamond exceptionally exhibits surface electrical conduction. When the surface of diamond is terminated by hydrogen, the adsorption of molecules such as carbonate in the air acts to cause an electrochemical reaction to proceed, and holes are generated as carriers on the surface.
[0003]
Originally, it was very interesting in practical use that although diamond is in an insulating state, electrical conduction occurs only near its surface. For example, when applied to a high-speed transistor, the effect was extremely high because the stray capacitance was drastically reduced. In addition, they also show features such as being advantageous for electrode insulation and element separation when used for ion sensors.
[0004]
As a technique related to a semiconductor device using such a diamond surface, there is a technique disclosed below.
[0005]
[Patent Document 1]
Japanese Patent No. 3313369 (page 2-3, FIG. 1)
[Non-patent document 1]
Yuji Ogawa and 4 others Symposium on Diamonds, 13th, 206-207, 1999
[Non-patent document 2]
Ken-ichi Chatan et al. Abstracts of Diamond Symposium, 12th, 82-83 1999
[Non-Patent Document 3]
H. Kawarada, et. Al. Phys. Status Solidi A185 (2001) 79
[Non-patent document 4]
T. Sakai, et. Al. Jpn, J .; Appl. Phys. 41 (2002) 2595-2597
[0006]
[Problems to be solved by the invention]
Attempts have been made repeatedly to increase the surface area density of the naturally occurring diamond surface to broaden the range of applications, but conventionally, the upper limit value is generally about 1-2 × 10 ¹³ / cm ^2. there were. If the diamond surface can be made more active electrically by raising the upper limit of the hole areal density, not only will its application as a semiconductor be expanded, but also new developments in electrochemically based environmental devices will be expected. Is done.
[0007]
The present invention has been made in view of the above circumstances, and has as its object to provide a method of treating a diamond substrate surface and a semiconductor device capable of increasing the hole surface density of the diamond surface and expanding the range of application.
[0008]
[Means for Solving the Problems]
The present invention, in order to achieve the above object,
[1] In the method for treating the surface of a diamond substrate, the surface of the diamond is exposed to a plasma comprising a mixed gas of hydrogen (H ₂ ) and fluorine sulfide (SF ₆ ) to reduce the surface conduction hole (hole) area density of the diamond to 8%. It is characterized by being increased to × 10 ¹³ / cm ² or more.
[0009]
[2] A semiconductor device characterized by using a diamond surface obtained by the substrate surface treatment method described in [1].
[0010]
[3] The semiconductor device according to the above [2], wherein the surface of the diamond is used for a high-speed transistor.
[0011]
[4] The semiconductor device according to the above [2], wherein the surface of the diamond is used for an ion sensor.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0013]
In the present invention, the surface of diamond is exposed to a plasma composed of a mixed gas of hydrogen (H ₂ ) and fluorine sulfide (SF ₆ ), and the upper limit of the surface conduction hole (hole) surface density of diamond is set to 8 × 10 ¹³ / cm. Try to increase to ^two or more.
[0014]
(Example)
FIG. 1 is a configuration diagram of a substrate reaction apparatus showing an embodiment of the present invention.
[0015]
In this figure, 1 is a reaction furnace, 2 is a mixed gas of hydrogen (H ₂ ) and fluorine sulfide (SF ₆ ), 3 is a heater heating unit, 4 is a substrate mounting table, and 5 is set on the substrate mounting table 4. Reference numeral 6 denotes a diamond substrate, 6 denotes a short-wavelength microwave (2.45 GHz) power supply, 7 denotes a waveguide, 8 denotes plasma, 9 exhaust, and 10 denotes water cooling.
[0016]
(1) First, a mixed gas 2 of hydrogen (H ₂ ) and fluorine sulfide (SF ₆ ) is supplied into the reaction furnace 1. The mixing ratio of the two gases can be freely set, but here, the ratio of SF ₆ / H ₂ was set in a range of 100 ppm or more. The mixed gas 2 was introduced into the reaction furnace 1, and the pressure was set to 20 Torr. The mixed gas 2 is irradiated with microwaves from a short wavelength microwave (2.45 GHz) power supply 6. Here, the microwave is 2.45 GHz, but the selection of the frequency is not particularly problematic. The mixed gas 2 in the reaction furnace 1 was brought into the state of plasma 8 by adjusting the introduced power of the microwave. At this time, the introduced microwave power is 400 W.
[0017]
(2) The surface of the diamond substrate 5 was exposed to the microwave plasma 8 generated in the reaction furnace 1, and a surface chemical reaction was progressed with time to perform a surface treatment. At this time, it was found that the (H ₂ + SF ₆ ) mixed gas 2 used in the present invention exhibited an extremely large effect. That is, a large amount of carrier holes is generated on the surface of the diamond substrate 5. As a result, it has become possible to realize a surface density of a carrier hole area density of 1 × 10 ¹⁴ / cm ² or more.
[0018]
FIG. 2 shows the processing time dependence of the electrical resistance change that occurs when the surface of the diamond thin film of the example of the present invention is exposed to the plasma of the (H ₂ + SF ₆ ) mixed gas.
[0019]
In this figure, the horizontal axis represents the processing time (minutes), and the vertical axis represents the sample electrical resistance (MΩ). The processing conditions at this time were a microwave power of 400 W, a total gas pressure of 30 Torr, and a substrate temperature of 600 ° C.
[0020]
As can be seen from this figure, when the gas mixture ratio (SF ₆ / H ₂ ) was 600 ppm (indicated by ●), the surface electrical resistance was reduced to 1/400 of the initial value in 4 minutes of the processing time. This is due to an increase in surface carrier hole areal density and an increase in carrier mobility μ. In addition, □ shows the characteristics when the gas mixture ratio (SF ₆ / H ₂ ) is 300 ppm.
[0021]
The manner in which the carrier hole area density increases can be seen in FIG.
[0022]
In FIG. 3, the horizontal axis represents the processing time (minutes), and the vertical axis represents the surface hole area density (10 ¹⁴ / cm ² ). The measurement is based on the Hall effect experiment.
[0023]
As is clear from FIG. 3, the surface hole area density becomes 8 × 10 ¹³ / cm ^{2 when the} processing time is about 3 minutes, and when it exceeds this value, it can be said that the surface hole area density is sufficiently high. The range can be expanded.
[0024]
That is, when the gas mixture ratio (SF ₆ / H ₂ ) is 600 ppm, by exposing the diamond surface to the microwave plasma of the (H ₂ + SF ₆ ) mixed gas, the hole surface density can be surely increased. Proven. In particular, it can be seen that the wall of 1 × 10 ¹⁴ / cm ² was broken at the time of the 4-minute treatment.
[0025]
In addition, a semiconductor device can be formed on the surface of the diamond substrate obtained as described above. For example, it can be expected to be used for a wide band gap semiconductor device having a large energy gap, and also for a bio-related device such as a surface catalysis and a surface immunity.
[0026]
That is, an ultra-high electric field is generated on the diamond surface, and the value is set to a high value of 1 × 10 ⁷ / cm ² . If this electric field is partially leaked from the diamond surface to the outside, this electric field is strongly involved in the electrochemical action of the surface, so that its application to bio-related devices such as surface catalysis and surface immunity can be expected.
[0027]
Further, the Stark effect, that is, a commercial device incorporating a built-in effect of an electric field due to nearby electrons or ions in a gas, a liquid, or a solid, or an effect of an externally applied electric field on spectral lines can be used.
[0028]
In the above embodiment, the surface treatment is performed on the diamond substrate. However, the present invention can be applied to a case where a thin diamond semiconductor film is interposed on the diamond substrate.
[0029]
It should be noted that the present invention is not limited to the above embodiments, and various modifications are possible based on the spirit of the present invention, and they are not excluded from the scope of the present invention.
[0030]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained.
[0031]
(A) A hole surface density of 1 × 10 ¹⁴ / cm ² or more can be realized on the diamond substrate surface.
[0032]
(B) By the surface treatment of the diamond substrate, the surface electric resistance can be reduced by two digits or more. If this effect is utilized, it is extremely convenient for power application of the diamond semiconductor device, and a high-power operation type semiconductor device with reduced loss can be realized.
[0033]
(C) Use in bio-related devices such as surface catalysis and surface immunity can be expected.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a reaction device of a semiconductor device according to an embodiment of the present invention.
FIG. 2 is a diagram showing the processing time dependency of a change in electrical resistance that occurs when a diamond thin film surface according to an example of the present invention is exposed to a plasma of a (H ₂ + SF ₆ ) mixed gas.
FIG. 3 is a diagram showing how the carrier hole area density on the diamond surface of the present invention increases.
[Explanation of symbols]
Reference Signs List 1 reaction furnace 2 mixed gas of hydrogen (H ₂ ) and fluorine sulfide (SF ₆ ) 3 heater heating unit 4 substrate mounting table 5 diamond substrate 6 short-wavelength microwave (2.45 GHz) power supply 7 waveguide 8 plasma 9 exhaust 10 Water cooling

Claims (4)

Exposing the surface of diamond to plasma comprising a mixed gas of hydrogen and fluorine sulfide, thereby increasing the surface conduction hole (hole) surface density of diamond to 8 × 10 ¹³ / cm ² or more. Method. A semiconductor device comprising a diamond surface obtained by the method of claim 1 as a substrate. 3. The semiconductor device according to claim 2, wherein the surface of the diamond is used for a high-speed transistor. 3. The semiconductor device according to claim 2, wherein the surface of the diamond is used as a sensor.

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