HK1108174A - Method of manufacturing a substrate for growth of single crystal diamond - Google Patents

Description

Method for producing substrate for single crystal diamond growth

Technical Field

The present invention relates to a method for manufacturing a substrate for single crystal diamond growth.

Background

Diamond has a wide band gap (wide band gap) of 5.47eV, and the dielectric breakdown field strength is 10MV/cm, which is extremely high. Further, diamond has the highest thermal conductivity among substances, and is very advantageous as a high-output power device when used in an electronic device.

On the other hand, diamond has a high drift (drift) mobility, and compared with Johnson performance index, it is also the semiconductor most advantageous as a high-speed power device.

Therefore, diamond is the most suitable semiconductor for high-frequency and high-output electronic devices.

Therefore, a laminated substrate formed by laminating diamond or the like on a substrate is attracting attention.

Currently, most of single crystal diamonds for diamond semiconductors are diamond type Ib synthesized by a high pressure method. The type Ib diamond contains a large amount of nitrogen impurities, and only has a size of about 5mm square, and thus has low practicability.

On the other hand, the Vapor phase synthesis (CVD) method has an advantage that diamond having a high purity and a large area can be obtained.

Before the diamond film is grown by the vapor phase synthesis method, a so-called bias treatment is performed in advance, in which a dc discharge is applied to the substrate before diamond growth, using the substrate-side electrode as a cathode, to form diamond nuclei.

For example, in non-patent documents 1 and 2, a bias treatment is performed at an Ir base material temperature of 900 ℃ before diamond growth, thereby producing a base material for single crystal diamond growth. It is reported that diamond particles having the same orientation can be grown on the substrate by diamond growth by the DC plasma CVD method.

Further, it is reported in non-patent document 3 that the same results as those in non-patent documents 1 and 2 can be obtained by performing bias treatment while setting the temperature of the Ir base material before diamond growth to 920 ℃.

However, in view of the above non-patent documents 1 to 3, the details of the method for measuring the temperature of the substrate, the conditions thereof, the measurement location, and the like are not described at all. Furthermore, in the experiments of the present inventors, even if the conditions described in the above non-patent documents 1 to 3 are satisfied under any other conditions, it is impossible to grow single crystal diamond on a substrate subjected to bias treatment at about 900 ℃.

[ non-patent document 1] Jpn.J.appl.Phys.Vol.35(1996) pp.L1072-L1074

[ non-patent document 2] NEW DIAMOND, Vol.18 No.4, (2002), pp.6-12

[ non-patent document 3] 65 th-application physical society academic lecture presentation pre-manuscript set No.2(2004), pp.508

Disclosure of Invention

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for producing a single crystal diamond growth substrate capable of more reliably growing single crystal diamond.

In order to solve the above problems, the present invention provides a method for manufacturing a single crystal diamond growth substrate, in which a bias treatment is performed in advance on at least a substrate before diamond growth, and a dc discharge is performed using a substrate-side electrode as a cathode to form diamond nuclei, the method comprising: in this treatment, the substrate temperature was maintained at 800 ℃. + -. 60 ℃ for at least 40 seconds from the start of the bias treatment to the end of the bias treatment.

In this way, in the bias treatment, the substrate temperature is maintained at 800 ℃. + -. 60 ℃ at least 40 seconds after the start of the bias treatment until the end of the bias treatment, whereby single crystal diamond can be grown more reliably.

In the method for producing a single crystal diamond growth substrate of the present invention, it is preferable that the bias treatment is performed so that the current density is set to 120 to 230mA/cm²。

In the method for producing a single crystal diamond growth substrate of the present invention, it is preferable that the bias treatment is performed for 45 seconds to 180 seconds.

In the method for producing a single crystal diamond growth substrate of the present invention, it is preferable that the bias treatment is performed by diluting methane with hydrogen in an atmosphere of CH concentration₄/(CH₄+H₂) 0.5 to 5.0 vol%.

In the method for producing a single crystal diamond growth substrate of the present invention, it is preferable that the ambient gas is a mixed gas containing carbon and hydrogen atoms and the pressure is 105 to 150 torr in the bias treatment.

In the method for manufacturing a single crystal diamond growth substrate according to the present invention, single crystal iridium (Ir) may be used as the diamond growth substrate before the bias treatment.

Alternatively, an Ir film grown by heteroepitaxy (heteroepitaxy) on a single-crystal MgO substrate may be used as the diamond growth substrate before the bias treatment.

Further, the present invention provides a method for manufacturing a laminated substrate, comprising: the substrate subjected to the bias treatment is grown at a substrate temperature of 700 to 1400 ℃ by a microwave CVD method or a DC plasma CVD method to produce a laminated substrate containing single crystal diamond.

Further, the present invention provides a laminated substrate comprising the single crystal diamond manufactured by the above method.

Further, the present invention provides an independent single crystal diamond substrate, comprising: from the laminated substrate manufactured by the above method, only diamond was taken out.

The present invention also provides a device manufactured by using the laminated substrate including the single crystal diamond or the independent single crystal diamond substrate.

As described above, by using the method for producing a single crystal diamond growth substrate of the present invention, single crystal diamond can be grown more reliably.

Drawings

FIGS. 1(a), (b), and (c) are graphs showing the temperature change of the substrate before and during the bias treatment (example 1).

FIGS. 2(a), (b), and (c) are graphs showing the temperature change of the substrate before and during the bias treatment (comparative example 1).

FIG. 3 is a graph showing the temperature change of the substrate before and during the bias treatment (comparative example 2).

Detailed Description

The following describes embodiments of the present invention, but the present invention is not limited thereto.

As described above, even if the bias treatment is performed in advance to form the nuclei of diamond, there is a problem that it is not possible to reliably grow single crystal diamond on the substrate subjected to the bias treatment. Therefore, the present inventors have made an effort to study conditions of the bias process again and again.

As a result, the present inventors have found that if the substrate temperature is set within a selected range and bias treatment is performed, single crystal diamond can be grown more reliably on the substrate subjected to the bias treatment, and thus the present invention has been completed.

That is, the method for producing a single crystal diamond growth substrate according to the present invention comprises subjecting a substrate before diamond growth to bias treatment in advance, and forming diamond nuclei by dc discharge using a substrate-side electrode as a cathode, characterized in that: in the treatment, the substrate temperature was maintained at 800 ℃. + -. 60 ℃ for at least 40 seconds from the start of the bias treatment to the end of the bias treatment.

In order to grow the single crystal diamond more reliably, as described above, the substrate temperature in the bias treatment must be maintained at 800 ℃. + -. 60 ℃ at least 40 seconds after the start of the bias treatment until the end of the bias treatment.

At a temperature lower than the optimum temperature range (lower than 740 ℃), amorphous carbon is formed on the surface of the substrate, but diamond nuclei cannot be formed, and the diamond growth treatment thereafter cannot grow single crystal diamond. On the other hand, at a temperature higher than the optimum temperature range (higher than 860 ℃), the surface etching proceeds, and diamond nuclei cannot be formed, and diamond cannot be grown by the subsequent diamond growth treatment.

Here, the measurement of the substrate temperature can be performed, for example, as follows.

The temperature of the surface of the substrate was measured by an IR-CAI2CS radiation thermometer manufactured by CHINO.

The measuring element of the radiation thermometer is InGaAs, the measuring wavelength is 1.55 μm, and the measurement can be carried out at a temperature of 300 ℃ to 1600 ℃. In the measurement, the surface of the substrate to be measured is Ir, and it is necessary to set the emissivity determined by crystallinity, surface shape, measurement temperature, measurement wavelength, and the like, but since precise setting is difficult, it is generally sufficient to set the emissivity of solid Ir at a known wavelength of 0.65 μm to 0.30. (see page 15 of the instruction manual: CHINO INST No. IR-274-P5 CE).

For example, a radiation thermometer is mounted on the outside of the chamber using a tripod, and the surface of the substrate in the chamber is aligned through a quartz window provided in the chamber.

Next, other conditions in the bias process are described below.

In the bias treatment, the current density is preferably 120 to 230mA/cm²。

In the bias treatment, the treatment time is preferably 45 seconds to 180 seconds.

Further, the atmosphere gas in the bias treatment is preferably hydrogen-diluted methane, and the concentration thereof is preferably CH₄/(CH₄+H₂) 0.5 to 5.0 vol%.

The atmosphere gas in the bias treatment is preferably a mixed gas containing carbon and hydrogen atoms, and the pressure is preferably 105 to 150 torr.

Next, as the diamond growth substrate used for the bias treatment, the following substrates can be used.

That is, single crystal iridium (Ir) can be used as the diamond growth substrate before the bias treatment.

Alternatively, the diamond growth substrate before the bias treatment may be an Ir film heteroepitaxially grown on a single-crystal MgO substrate.

Further, the present invention provides a method for manufacturing a laminated substrate, comprising: the substrate subjected to the bias treatment is grown at a substrate temperature of 700 to 1400 ℃ by a microwave CVD method or a DC plasma CVD method to produce a laminated substrate containing single crystal diamond.

Further, the present invention provides a laminated substrate comprising the single crystal diamond manufactured by the above method.

Further, the present invention provides an independent single crystal diamond substrate, comprising: from the laminated substrate manufactured by the above method, only diamond was taken out.

Further, the present invention provides a device manufactured by using the laminated substrate including the single crystal diamond or the independent single crystal diamond substrate.

[ examples ]

The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited thereto.

Example 1

A single crystal MgO substrate was prepared by polishing both sides of the substrate in a 10.0mm square, 0.5mm thick and in an orientation (100).

Then, on the side of the MgO substrate on which diamond deposition is performed, an Ir film is heteroepitaxially grown. An Ir film was also grown on the back surface for electrical conduction.

Next, a bias process for forming diamond nuclei is performed on the Ir film surface of the substrate.

First, in preparation before the bias treatment, the substrate is mounted on a negative voltage application electrode (cathode) and vacuum-exhausted. Next, the substrate was heated (1 st heating) to raise the substrate temperature to 648 ℃ in 5 minutes (fig. 1 (a)). Then, CH is introduced₄/H₂Gas, base pressure was set at 115 torr. Then, the substrate was heated again (2 nd heating) to raise the substrate temperature to 461 ℃ within 5 minutes (fig. 1 (b)).

Then, a bias process is performed. Namely, a DC voltage (345mA) was applied. At this time, the substrate temperature was raised to 800 ℃ in 40 seconds, and then to 810 ℃ in 90 seconds (fig. 1 (c)).

Finally, diamond was grown on the substrate by microwave (2.45GHz) CVD.

As a result, it was confirmed that single crystal diamond could be grown on the obtained laminated substrate.

Comparative example 1

In the same manner as in example 1, an Ir film was heteroepitaxially grown on the side of the MgO substrate on which diamond deposition was performed. An Ir film was also grown on the back surface for electrical conduction.

Next, bias treatment is performed to form diamond nuclei on the Ir film surface of the substrate.

First, in preparation before the bias treatment, the substrate is placed on a negative voltage application electrode (cathode) and vacuum-exhausted. Next, the substrate was heated (1 st heating) to raise the substrate temperature to 538 ℃ within 5 minutes (fig. 2 (a)). Then, CH is introduced₄/H₂Gas, and base pressure was 115 torr. Then, the substrate was heated again (2 nd heating) to raise the substrate temperature to 423 ℃ within 5 minutes (fig. 2 (b)).

Then, a bias process is performed. Namely, a DC voltage (280mA) was applied. At this time, the substrate temperature was raised to 720 ℃ in 40 seconds, and then to 799 ℃ in 90 seconds (fig. 2 (c)).

Finally, diamond was grown on the substrate by microwave (2.45GHz) CVD.

However, when the obtained laminated substrate was confirmed, it was confirmed that single crystal diamond could not be grown.

Comparative example 2

In the same manner as in example 1, an Ir film was heteroepitaxially grown on the side of the MgO substrate on which diamond deposition was performed. An Ir film is grown on the back side for electrical conduction.

Next, a bias process for forming diamond nuclei is performed on the Ir film surface of the substrate.

That is, after the selected preparation is performed before the treatment, a DC voltage (400mA) is applied. In this case, the substrate temperature can be raised to 852 ℃ within 40 seconds and then to 887 ℃ within 90 seconds (FIG. 3).

Finally, diamond was grown on the substrate by microwave (2.45GHz) CVD.

However, when the obtained laminated substrate was confirmed, it was confirmed that single crystal diamond could not be grown.

The present invention is not limited to the above embodiments. The above-described embodiments are merely exemplary, and any embodiments that have substantially the same configuration as the technical idea described in the claims of the present invention and can exhibit the same effects are included in the technical scope of the present invention.

Claims (11)

1. A method for manufacturing a substrate for single crystal diamond growth, in which a bias treatment is performed in advance on at least a substrate before diamond growth, and a direct current discharge is performed using a substrate-side electrode as a cathode to form diamond nuclei, characterized in that:

in the bias treatment, the substrate temperature was maintained at 800 ℃. + -. 60 ℃ for at least 40 seconds from the start of the bias treatment to the end of the bias treatment.

2. The method for producing a single-crystal diamond growth substrate according to claim 1,wherein the current density of the bias treatment is 120-230 mA/cm²。

3. The method of manufacturing a single crystal diamond growth substrate according to claim 1 or 2, wherein the bias treatment is performed for a period of time of 45 seconds to 180 seconds.

4. The method of manufacturing a single crystal diamond growth substrate according to claim 1 or 2, wherein the atmosphere gas in the bias treatment is hydrogen-diluted methane having a CH concentration₄/(CH₄+H₂) 0.5 to 5.0 vol%.

5. The method of manufacturing a single crystal diamond growth substrate according to claim 1 or 2, wherein the ambient gas in the bias treatment is a mixed gas containing carbon and hydrogen atoms, and the pressure is 105 to 150 Torr.

6. The method of manufacturing a single crystal diamond growth substrate according to claim 1 or 2, wherein single crystal iridium (Ir) is used as the diamond growth substrate before the bias treatment.

7. The method for producing a single-crystal diamond growth substrate according to claim 1 or 2, wherein an Ir film heteroepitaxially grown on a single-crystal MgO substrate is used as the diamond growth substrate before the bias treatment.

8. A method for manufacturing a laminated substrate, comprising:

a single crystal diamond-containing laminated substrate produced by growing a substrate subjected to bias treatment according to any one of claims 1 to 7 at a substrate temperature of 700 to 1400 ℃ by a microwave CVD method or a DC plasma CVD method.

9. A laminated substrate comprising the single crystal diamond produced by the method of claim 8.

10. A freestanding single crystal diamond substrate, comprising: from the laminated substrate produced by the method of claim 8, only diamonds were extracted.

11. An apparatus fabricated using a laminated substrate comprising the single crystal diamond of claim 9 or the isolated single crystal diamond substrate of claim 10.