JPH0360495A - Method for selective growth of vapor synthesized diamond - Google Patents

Abstract

PURPOSE:To inexpensively obtain a diamond film having an arbitrary shape without requiring any specific means, such as coating with a mask material, at all by setting a temp. difference between the vapor deposition section and non-vapor deposition section of a substrate at the time of growing the diamond in the arbitrary section of the substrate by a vapor synthesis method. CONSTITUTION:The vapor deposition section of the substrate is maintained at the temp. suitable for vapor deposition and the temp. in the non-vapor deposition section of the substrate is maintained at a non-vapor deposition temp., then the diamond is deposited by evaporation only in the vapor deposition section at the time of the vapor synthesis of the diamond in the arbitrary section of the substrate by a physical vapor deposition method or chemical vapor deposition method. The above mentioned vapor deposition section is preferably heated to 500 to 1100 deg.C and the non-vapor deposition reaction is kept at <400 deg.C. For example, the constitution to positively heat the vapor deposition section 8 by electrically heating (electrodes 2, 2, a power source 10) only the vapor deposition section 8 of the substrate 1 and to keep the non-vapor deposition section 9 without being heated is adopted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for selectively growing diamond by vapor phase synthesis, which allows diamond crystals to grow in an arbitrary pattern on a substrate.

[Prior art] Diamond has excellent properties such as high hardness, wide band gap, high thermal conductivity, optical transparency, radiation resistance, and chemical resistance, so it is used as a cutting/abrasive material, insulation, etc. It is a useful industrial material that can be applied to bodies, heat sinks, space window materials, etc., and by adding appropriate doping materials, it can also be applied to light emitting devices, high temperature/high power semiconductors, etc.

Conventionally, diamonds have been obtained by mining natural products or by treating carbon such as graphite under high temperature and pressure, but these methods require large-scale and expensive equipment, which increases costs. Therefore, as an alternative to this, a technique for vapor phase synthesis using chemical vapor deposition or physical vapor deposition has been developed.

By using these vapor phase synthesis methods, not only granular diamonds but also film-like diamonds, which cannot be synthesized using high-temperature and high-pressure methods, can be produced over a wide range of substrates.

It can be synthesized in a short time. By taking advantage of this advantage, it has become possible for the first time to industrially apply diamond to semiconductor devices, semiconductor substrate heat sinks, semiconductor device insulators, coatings for long-life carbide tools, chemical-resistant coatings, etc.

By the way, in these applications, it is necessary to mold into any available shape. To solve this problem, JP-A-62-2
No. 97298 discloses a method in which a diamond forming portion on the surface of a substrate is covered with a mask member, the remaining portion is covered with an amorphous material, the mask portion is removed to expose the substrate, and then vapor phase synthesis is performed.

In addition, Japanese Patent Application Laid-Open No. 63-315598 discloses that after covering the diamond-forming portion of a substrate with an uneven surface with a mask member, energy ray irradiation is applied to eliminate the unevenness, and then the mask is first removed to expose the exposed unevenness. A method is disclosed in which vapor phase synthesis is selectively performed only in certain regions.

However, these methods require the preparation of a mask member, an amorphous material, an energy ray source, and the covering and removal of the mask material, which increases the number of steps and costs, resulting in problems in terms of productivity and cost.

[Problems to be Solved by the Invention] The present invention provides a synthesis method that does not require any special means such as coating with a mask material when obtaining a diamond film of any shape that is industrially applicable by diamond vapor phase synthesis. This is intended to solve the problems of the prior art, such as decreased productivity and increased costs.

[Means for Solving the Problem 1] In the vapor phase synthesis method of diamond, it is known that the presence or absence of precipitation and the precipitation rate are extremely dependent on the substrate temperature. FIG. 1 qualitatively shows the relationship between substrate temperature and vapor growth rate. In FIG. 1, no precipitation is observed in region 1 where the substrate temperature is low, the precipitation rate is extremely low in regions 2 and 3, and precipitation is observed in region 4 when the substrate temperature is maintained above a certain temperature. Therefore, if the substrate temperature distribution is non-uniform, the amount of precipitation will also be non-uniform.

Therefore, the main focus of conventional substrate temperature control has been to make the temperature distribution as uniform as possible and to obtain uniform precipitation.

For the reasons mentioned above, the inventors felt strongly that there was a need for a technology to easily and inexpensively manufacture diamond films of arbitrary shapes, and after various studies, they discovered a technology that could utilize the dependence of deposition on substrate temperature. As a result, we have found that this solution is possible.

That is, the present invention synthesizes a diamond film of arbitrary shape by chemical vapor deposition method or physical vapor deposition method (hereinafter abbreviated as CVD method and PVD method, respectively) without depositing it on the substrate region to be deposited (hereinafter referred to as evaporation region). This method creates a temperature distribution in the substrate area (hereinafter referred to as non-evaporation area), keeps the evaporation area at a temperature suitable for evaporation, and maintains the temperature of the non-evaporation area at the non-evaporation temperature to synthesize the film, and the purpose is to achieve uniformity. This is a revolutionary method with a completely different concept from conventional substrate temperature control technology.

As for the temperature, it is preferable that the temperature of the vapor deposition area is heated to 500 to 1100°C, and the temperature of the non-evaporation area is less than 400°C.

[Effect]

As mentioned above, the diamond precipitation rate is extremely dependent on the substrate temperature, and the structure of the present invention is to maintain the deposition area on the substrate at a temperature suitable for diamond precipitation and the non-evaporation area at a non-deposition temperature. The purpose is to perform vapor deposition.

Specifically, as can be seen from Fig. 1, in order to deposit only diamond in the evaporated area and not to precipitate diamond in the non-evaporated area, the temperature of the evaporated area must be adjusted to region 4 in Fig. 1 at the same time. The temperature of the non-evaporated area is determined by the area l in Figure 1.
need to be kept.

In order to simultaneously obtain these different temperatures of 2f+1 on the substrate, (1) active heating of the vapor deposition area, (2) active cooling of the non-evaporation area, (3) or a combination of the former two are performed.

In addition, by keeping the temperature of the evaporation area in region 4 in Figure 1 and the temperature of the non-evaporation area in area 2 or 5 in Figure 1, only diamond can be deposited in the evaporation area and non-diamond can be deposited in the non-evaporation area. can be done.

Examples of specific configurations for implementing the present invention are shown in FIGS. 2 to 6, and will be explained below.

FIG. 2 shows a configuration in which only the diamond evaporation area 8 is electrically heated to actively heat the evaporation area 8 and the non-evaporation area 9 is not heated. A power source 1 is placed on the surface of the vapor deposition substrate 1.
Electrodes 2.2 to which 0 is connected are placed so as to sandwich the vapor deposition site 8. The type of diamond raw material 11, such as a mixed gas of thermally or plasma-excited hydrocarbon gas and hydrogen gas in the case of the CVD method, or a carbon ion beam in the case of the PVD method, is For example, in the case of a hot filament method, the raw material gas is supplied from above through the raw material gas supply nozzle 12. 13 is a filament for heating raw material gas. When energized, Joule heat is generated only between the electrodes 2 and 2, and the temperature of the substrate 1 can be adjusted by adjusting the amount of energization.

FIG. 3 shows an electric heating method similar to that shown in FIG. 2, but has a configuration in which active heating is achieved by increasing the current density only at the diamond deposition region 8. The vapor deposition substrate 1 is energized from a power source IO through an electrode (not shown), and a notch 14 is provided in the substrate 2 only at the vapor deposition region 8 to increase the Joule heat generation amount. In this case, the substrate temperature can be freely set by adjusting the size of the notch 14 provided in advance and the amount of current applied.

FIG. 4(a) is a perspective view showing a configuration that combines the principles of FIGS. 2 and 3, and enables patterning vapor deposition by creating a notch 3 on the back surface of the substrate by machining, chemical treatment, or other means. That is. That is, as shown in FIG. 4(b), cutouts 3 in a desired pattern are made on the back surface of the vapor deposition substrate l, and as shown in FIG. An electrode 2.2 is placed on top and heated by electricity from a power source 10. The part of the notch 3 becomes a vapor deposition part 8, and the current density and temperature thereof are higher than those of the non-notch part (non-deposition part 9). Therefore, vapor deposition according to the pattern is realized. Although the entire substrate 1 may be energized, it is more economical to energize only the portion where the pattern is formed, as shown in FIG. 4(a), with less power loss. The substrate temperature can be set by adjusting the amount of notches and the amount of current applied. Furthermore, if the amount of heat generated in the non-notched portion (non-vapor deposition portion 9) is excessive, temperature rise in the portion can be prevented by cooling the back surface of the substrate. At this time, it is effective to prevent the notch from coming into contact with the cooling surface.

The principle of this method is to increase the current density at the vapor deposition site 8, and the notch 3 in the substrate 1 itself is not necessarily required. For example, as shown in FIG. 4(C), a conductive auxiliary substrate 7 of a different type or the same type as the substrate 1 is closely attached to the back surface of the substrate 1, and the auxiliary substrate 7 has a notch 3 on the back or front surface for obtaining a vapor deposition pattern. Alternatively, as shown in FIG. 4(d), a pattern cutout 6 may be provided on the auxiliary board 7, and conductive paste or the like may be applied to both contact surfaces to ensure good continuity, and current may be applied to both boards at the same time. The same objective can also be achieved by the method of heating.

FIG. 5 is based on the configuration shown in FIG.
The configuration is such that a water cooling device 4 cools the back surface of the holder. Water cooling device 4
As shown in FIG. 5(b), a concave pattern 17 is provided, and a highly thermally conductive solvent 18 is sandwiched between the contact surface between the substrate l and the water cooling device 4. Although the substrate 1 is heated by electricity, the substrate 1 is not cooled in the concave pattern 17 of the water cooling device 4, and the substrate surface temperature is high. The vapor is not deposited on the non-evaporation area 9 which has been vapor-deposited and cooled.

The basic principle of FIG. 6 is the same as that of FIG. 5, in which the substrate 1 is partially cooled by a cooling device 4 to form a vapor deposition area 8 and a non-evaporation area 9, but the substrate 1 is heated by an electric furnace 5. The difference is that they do this. Further, even when the entire substrate is inevitably heated, a method similar to that shown in FIG. 6 can be used, such as a hot filament CVD method or a plasma CVD method.

The configuration of the present invention has been described above using FIGS. 2 to 6 as examples. The gist of the present invention is to perform vapor deposition while keeping the diamond vapor deposition area 8 on the substrate at a temperature suitable for deposition and the non-evaporation area 9 at a non-deposition temperature, and heating methods include substrate current heating, electric furnace heating. The cooling method is not limited to water cooling, and any suitable refrigerant and cooling means may be used. It goes without saying that the structures of the heating device and the cooling device are not limited to those shown in FIGS. 2 to 6. Further, the present invention provides various C
Any vapor deposition method such as VD method or PVD method can be applied.

Here, the required heating temperature of the diamond deposition area is 500°C.
~1100°C. When the temperature exceeds 1100°C, no diamond is formed and only non-diamond carbon is precipitated.

If the temperature is less than 500°C, no diamond will be formed and only non-diamond carbon will precipitate.

On the other hand, the temperature of the non-evaporated area needs to be lower than 400°C. If the temperature is below 400°C, neither diamond nor non-diamond carbon will precipitate at all.

Further, as the substrate, metals and semiconductors that do not contain a large amount of C as a solid solution, such as Si, Mo, W, Ta, etc., and various ceramics can be used.

As the raw material gas for the CVD method, a mixed gas of a carbon-containing compound and hydrogen, or an additive gas such as oxygen gas, inert gas, or water vapor is used as necessary.

〔Example〕

Example 1 Using the method of FIG. 2 according to the present invention, a hot filament CV
Diamond was selectively grown on the substrate 1 using the D method.

The substrate 1 is made of 5
100 polished with diamond abrasive grains of grain size ILLm
It is silicon with dimensions of mm×100m and m×0.5mm.

Stainless steel electrodes 2 each having a width of 10 mm were placed substantially in the center of the substrate 1, facing each other so that the distance between the electrodes was 20 mm. A tungsten filament 13 is placed at a position 10 mm away from the surface of the vapor deposition site 8 between the electrodes 2 and 2, and a supply nozzle for supplying raw material gas 11 (a mixed gas of methane and hydrogen) is placed at a position further 10 mm away from the surface of the tungsten filament 13. 12 were installed. Note that the center of the filament 13, the nozzle i2
The center of the vapor deposition surface 8 and the center of the vapor deposition surface 8 were both arranged on the same axis perpendicular to the substrate 1.

These are the same CVD connected to a vacuum pump (not shown).
installed inside the container. Filament 13 and electrode 2
．． 2 are each connected to a variable output power source equipped with a current-voltage meter via the inlet terminal of the container.

The filament temperature during deposition was measured with an optical pyrometer, and also by contacting the tip of a thermal lightning pair with the deposition site 8, and the temperature was maintained at a constant target temperature by adjusting the output power of the power source. The conditions during vapor deposition are as follows.

Methane flow rate: 5 sec Hydrogen flow rate + 500 sec Atmospheric pressure 30 Torr Filament temperature: 2100°C Substrate temperature (evaporation area) + 900°C (non-evaporation area): 300°C or less Evaporation time 11 hours The reason why the substrate temperature was set to the above conditions is generally In the CVD method, the substrate temperature suitable for diamond deposition is 500 to 1100.
This is because no precipitation is observed at temperatures below 400°C. After vapor deposition.

A film grew only on the vapor deposition site 8, which is the current-carrying part. When this film thickness was measured using a contact type surface roughness meter, the distribution shown in FIG. 7A was obtained. FIG. 7(a) shows the film thickness distribution in the electrode direction, and FIG. 7(b) shows the film thickness distribution in the direction perpendicular to this. When a part of the deposited area was cut out and observed under a scanning electron microscope, it was found that the film had a structure in which many crystals with euhedral surfaces were densely accumulated. Furthermore, Raman spectroscopy confirmed that this film was high-quality diamond containing almost no amorphous carbon or graphite. Furthermore, when the non-evaporated area 9 was observed using a scanning electron microscope, no crystals as described above were observed, and not only diamond but also no amorphous carbon or graphite was detected in Raman spectroscopy.

Example 2 The six substrates on which diamond was selectively grown on the substrate 1 by the hot filament CVD method using the method shown in FIG. 4(a) according to the present invention were the same silicon substrates as in Example 1. A recess with a length of 20 mm and a width of 10 mm and a depth of 0.25 mm was formed on the back surface of the vapor deposition site 8 at the center of the substrate by etching with hydrofluoric acid. Other conditions were the same as in Example 1.

After the deposition, the film grew only on the deposition site 8 on the opposite side of the substrate from where the depression was formed. When this film thickness was measured using a contact type surface roughness meter, the distribution shown in FIG. 7B was obtained.

As a result of identifying the film using the same method as in Example 1, we found that this film was high-quality diamond containing almost no amorphous carbon or graphite, and that there was no diamond, amorphous carbon, or graphite in the other parts. It was confirmed that there was no such thing.

Example 3 Using the method shown in FIG. 5(a) according to the present invention, diamond was selectively grown on a substrate 1 by microwave plasma CVD. The deposition conditions are as follows.

Carbon tetrachloride flow fi: 1 sec Hydrogen flow rate: 101005e Atmospheric pressure 30 Torr Substrate temperature (evaporation area): 900°C (non-evaporation area): 100°C or less Microwave frequency: 2.45 GHz Microwave output + 400 W Evaporation time = 1 hour Substrate is a silicon substrate of 40 mm x 40 mm x 0.5 mm, and the pretreatment method is the same as in Example 1. The cooling device is made of copper and has a surface length of 20 mm, width of 10 mm, and depth of 0-5 m.
There is a dent of m. After applying an insulating paste with high thermal conductivity to the surface on the concave side, contact was made from the back surface of the substrate 1 so that the concave portion was approximately at the center of the substrate 1. Further, a stainless steel electrode 2 was placed on the surface of the substrate 1 so as to sandwich this portion, and electricity was applied. By applying electricity, only the vapor deposition area 8 corresponding to the recessed area became red hot. The substrate surface temperature was kept constant by adjusting the amount of current and water supplied.

After vapor deposition, a film grew only on the vapor deposition site 8 corresponding to the opposite side of the recessed portion of the substrate. When this film thickness was measured using a contact type surface roughness meter, almost the same distribution as that shown in FIG. 7A was obtained.

As a result of identifying the film using the same method as in Example 1, we found that this film was high-quality diamond containing almost no amorphous carbon or graphite, and that there was no diamond, amorphous carbon, or graphite in the non-deposited area 9. It was confirmed that there was no.

Example 4 Using the method shown in FIG. 6 according to the present invention, thermal filament CV
Selective growth of diamond on substrate 1 was performed using the D method.

The substrate is the same silicon substrate as in Example 1, and the cooling device is the same as in Example 3.

Atmosphere heating was performed using Fe-Cr-Aβ installed in the CVD container.
This was done using a system heating element. Other conditions were the same as in Example 1, but the substrate temperature in the non-evaporation area 9 did not exceed 100°C.

After vapor deposition, a film grew only on the vapor deposition site 8 corresponding to the opposite side of the recess. This film thickness distribution was almost the same as that shown in FIG. 7A.

The film was identified using the same method as in Example 1, and it was found that this film was high-quality diamond containing almost no amorphous carbon or graphite, and that diamond, amorphous carbon, and graphite were present in the non-evaporated portion 9. It was confirmed that there were none.

As seen in the examples above, the present invention made it possible to obtain a diamond film in the desired shape without requiring any special means such as covering with a mask material. The gist of the present invention is to perform i17 on the substrate while keeping the diamond evaporation area at a temperature suitable for deposition and the non-evaporation area at a non-deposition temperature, and the heating/cooling method is limited to the above embodiment. It is a highly versatile method that can be applied to various CVD methods and PVD methods.

[Effect of the invention 1] By applying the present invention, a diamond film of any shape that can be applied industrially can be vapor-deposited by a vapor phase synthesis method without requiring any special means such as covering with a mask material. This has made it possible to easily and inexpensively manufacture diamond-based semiconductor elements, semiconductor substrate heat sinks, insulators between semiconductor elements, coatings for long-life carbide tools, chemical-resistant coatings, etc.

[Brief explanation of drawings]

Figure 2 is a graph showing the relationship between substrate temperature and growth rate.
6 to 6 are explanatory diagrams of specific device configurations when implementing the present invention,
FIG. 7 is a graph of the diamond film thickness distribution when the present invention is implemented. l...Substrate 2-...Electrode 3...Notch
4... Cooler 5... Heating element 6
- Cutout 7... Auxiliary substrate 8... Evaporation area 9... Non-evaporation area

Claims (1)

[Scope of Claims] 1. When vapor phase synthesis of diamond is performed on any part of a substrate by physical vapor deposition or chemical vapor deposition, the vapor deposition part of the substrate is maintained at a temperature suitable for vapor deposition, and the temperature of the non-evaporation part of the substrate is maintained at a temperature suitable for vapor deposition. A selective growth method for vapor-phase synthetic diamond, which is characterized by keeping diamond at a non-evaporation temperature and depositing diamond only on the deposition site. 2. The method for selectively growing vapor-phase synthetic diamond according to claim 1, characterized in that the temperature of the vapor deposition area is heated to 500 to 1100°C, and the temperature of the non-evaporation area is less than 400°C.