CN115786874A - A high-efficiency doping HFCVD equipment based on dual gas flow - Google Patents

Abstract

A high-efficiency doping HFCVD equipment based on dual gas flow, including a reaction chamber and a gas introduction structure. The gas introduction structure includes four gas pipelines, two upper and lower gas inlets; the first gas pipeline enters the reaction gas, The second gas pipeline is fed with carrier gas. After the gas in the first and second gas pipelines is mixed, it is introduced into the reaction chamber from the first gas inlet through the upper gas inlet. The upper gas inlet is located at the top of the reaction chamber. The center position; a hot wire is set between the upper air inlet and the substrate table; the third gas pipeline is fed with dopant gas, the fourth gas pipeline is fed with carrier gas, and the two gases are mixed from the second The air inlet pipe is introduced into the reaction chamber through the lower air inlet. The lower air inlet is located at the center below the substrate table and is in the shape of a trumpet. The upper and lower air inlets and the orthographic projection surface of the substrate table are in a concentric structure. The invention effectively improves the utilization efficiency of the doping gas in the growth of the diamond film, and realizes high-efficiency doping in the diamond film sample.

Description

A high-efficiency doping HFCVD equipment based on dual gas flow

technical field

The invention relates to the field of hot wire chemical vapor deposition, and discloses a high-efficiency doping HFCVD device based on a double-flow technology, in particular, the device has a double-flow gas input structure.

Background technique

Diamond has many advantages such as high hardness, high melting point, high insulation, wide band gap, high thermal conductivity, good chemical stability, acid and alkali corrosion resistance, etc. Broad prospects. At present, the performance of artificial diamond film is close to that of natural diamond, and some properties can be improved by doping different element particles. It has many applications in high-tech fields, such as cutting tools and wear-resistant materials, p-n diodes and thermistors and other components. , high-power IGBT devices, high-voltage high-speed photoelectric switches, aerospace materials, etc., have attracted more and more attention. The diamond film prepared by chemical vapor deposition (CVD) has bandgap, high breakdown electric field, high resistivity, high electron mobility, high electron saturation rate, low dielectric constant, high thermal conductivity, strong hardness, and low coefficient of friction And many excellent properties such as low thermal expansion coefficient, it is the most promising semiconductor material and new coating material. Hot wire chemical vapor deposition (HFCVD) is a relatively mature method for synthesizing diamond coatings. It has many advantages such as low cost, simple operation, mature process, and fast film formation speed. It is easy to control the temperature and doping of the substrate, and it is easier to A diamond film with better quality is prepared.

At present, conventional HFCVD equipment is mainly used in the manufacture of drills, blades, grinding tools and other tools to increase the mechanical properties of tools without doping. The diamond coating is directly deposited on the surface of the tool by the HFCVD method, which can be deposited on any shape of the tool substrate and applied to the processing of high-hardness materials. The quasi-isotropy of the polycrystalline feature of the diamond film, when used as a wire drawing die, the die hole wears evenly, which is better than the performance of the diamond single crystal wire drawing die, and the current technology is relatively mature.

When diamond thin films are applied in semiconductor materials and devices, their electrical properties should be improved. For example, boron-doped diamond (BDD) has more excellent uses, and the conductivity can be improved by efficiently doping boron. In the laboratory, conventional HFCVD equipment has the following problems when making diamond films and BDD samples:

1. The HFCVD equipment adopts a single air inlet design. The air inlet of the HFCVD equipment is far away from the hot wire. The dopant gas introduced from the air inlet moves with the carrier gas to the reaction chamber and diffuses to the substrate position. The concentration is low, which leads to low doping efficiency and cannot achieve the effect of high-efficiency doping.

2. In order to meet the high-efficiency doping requirements of diamond films, especially the high-efficiency boron doping requirements of BDD (boronized diamond) films to increase conductivity, HFCVD equipment needs to be fed with a higher concentration of doping gas, which will greatly increase the cost of raw materials. In addition, diborane, a commonly used doping gas, is highly toxic and has high chemical activity. It is very easy to produce chemical reactions with various inorganic molecules and organic molecules. After mixing with air, it is very easy to spontaneously ignite and explode. The environment will be polluted and harmed, and the cost of pollution control will also increase greatly.

Contents of the invention

The object of the present invention is to propose a method for realizing a high-efficiency doping HFCVD equipment based on dual-airflow technology in view of the problems existing in the existing HFCVD equipment. The inlet is upgraded to upper and lower double inlets, and the reaction gas and dopant gas are independently introduced into the growth area from the upper and lower inlets. The focus is to solve the problem of the inlet structure of the lower dopant gas and reduce its influence on the distribution of the reaction gas. At the same time, it can significantly increase the doping gas concentration above the substrate stage, realize efficient doping of diamond films, and meet the practical needs of high-efficiency doping in various diamond films, especially BDD film applications. The schematic diagram of the equipment structure is shown in Figure 1.

The technical solution of the present invention is: a high-efficiency doped HFCVD equipment based on dual-flow technology, including a reaction chamber and a gas introduction structure, the gas introduction structure includes four gas pipelines, two upper and lower gas inlets; The reaction gas is fed into the pipeline, and the carrier gas is fed into the second gas pipeline. After the gas in the first and second two gas pipelines is mixed, it is introduced into the reaction chamber from the first inlet pipe through the upper inlet. The gas inlet is located at the center of the top of the reaction chamber; a hot wire is provided between the upper gas inlet and the substrate table; the third gas pipeline is fed into the dopant gas, and the fourth gas pipeline is fed into the carrier gas. After the two-way gas is mixed, it is introduced into the reaction chamber from the second air inlet pipe through the lower air inlet 8, and the second air inlet pipe and the lower air inlet are connected at the lower part of the substrate table, and the lower air inlet is located at the center below the substrate table. It is trumpet-shaped, and the upper and lower air inlets and the orthographic projection plane of the substrate table are concentric structures;

Upper gas inlet The upper gas inlet is located at the center of the top of the reaction chamber, and the aperture of the upper gas inlet is controlled within the range of 1 cm to 2 cm, so as to control the flow rate of the reaction gas on the substrate table within an appropriate range.

A hot wire is provided at a height of 7 cm to 9 cm below the upper air inlet, and the reaction gas can be evenly radiated onto the hot wire.

The hot wire is located above the substrate stage, and the height between the hot wire and the substrate stage is controlled within a range of 0.4 cm to 1.5 cm, so as to control the temperature of the surface of the substrate stage within an appropriate range.

The lower air inlet is located at the center of the substrate table, and its shape is similar to that of a trumpet. The upper and lower air inlets and the substrate table are in a concentric structure. The level difference between the mouth of the lower air inlet and the substrate table is -0.5 cm to Between -1 cm, the flare angle of the lower air inlet (the angle between the inclined wall of the lower air inlet and the vertical line) is in the range of 0 degrees to 60 degrees, and the dopant gas radiates from the center to the surroundings to realize the substrate table The relatively uniform distribution of surface doping gas is shown in Figure 2.

The aperture of the lower gas inlet is controlled in the range of 0.2 cm to 1 cm to avoid gas divergence caused by excessively large apertures, realize uniform distribution of dopant gas on the substrate stage, and avoid affecting the growth gas.

The air inlet pipe and the lower air inlet are connected at the lower part of the substrate table, and the air inlet pipe can be made of stainless steel or metal molybdenum.

Beneficial effects: the present invention needs to feed a higher concentration of dopant gas for HFCVD in the preparation of diamond, especially boronized diamond film, and the concentration of BH3 groups in HFCVD equipment with dual gas flow technology is significantly higher than that in conventional HFCVD equipment. 5 to 10 times larger, compared with Figure 5a and Figure 5b, the concentration of the CH3 group in the dual-flow technology HFCVD equipment is not much different from that of the conventional HFCVD equipment; the present invention will greatly reduce the cost of raw materials and improve production efficiency High, overcome the deficiency of the prior art to produce BDD (boronized diamond) film, all have obvious unexpected effect than HFCVD to produce ordinary diamond film and boronized diamond film.

Description of drawings

Fig. 1 is the schematic diagram of the reaction chamber and the gas introduction structure of the dual-flow technology HFCVD equipment of the present invention;

Fig. 2a is a schematic cross-sectional view of the lower air inlet of the double-flow technology HFCVD equipment of the present invention;

Fig. 2b is a top view schematic diagram of the lower air inlet of the HFCVD equipment with dual air flow technology of the present invention;

Fig. 3 a is the HFCVD equipment-BH3 group concentration profile of the present invention;

Fig. 3 b is the HFCVD equipment-CH3 group concentration distribution figure of the present invention;

Fig. 4 is comparative example-conventional HFCVD equipment reaction chamber and gas introduction structure schematic diagram;

Fig. 5a is a comparison diagram of the concentration distribution of BH3 groups between the embodiment-dual-flow technology HFCVD equipment and the conventional HFCVD equipment.

Fig. 5b is a comparison diagram of the concentration distribution of CH3 groups between the HFCVD equipment of the embodiment-dual gas flow technology and the conventional HFCVD equipment.

Detailed ways

In order to further illustrate the technical means of the present invention, the specific implementation manners of the present invention will be described in detail below in conjunction with the accompanying drawings and examples. The specific embodiments described here are only used to illustrate and explain the technical solution of the present invention, and are not used to limit the present invention.

In the present invention, the reaction chamber of the dual-airflow technology HFCVD equipment adopts a cylindrical structure. As shown in Figure 1, the reaction chamber adopts the dual-airflow technology, that is, the single upper air inlet in HFCVD is upgraded to the upper and lower double air inlets, and the reaction gas and doping The gas is independently introduced into the growth area from the upper and lower gas inlets. The key point is to solve the problem of the inlet structure of the dopant gas at the lower gas inlet, reduce its influence on the distribution of the reaction gas, and at the same time significantly improve the doping gas above the substrate stage. The high-efficiency doping of diamond thin films can be achieved by increasing the concentration of impurity gases.

Figure 1 shows: it includes a reaction chamber and a gas introduction structure. The gas introduction structure includes four gas pipes, two air inlets and a first air inlet pipe. The first gas pipe is fed with reaction gas, and the second gas pipe is passed through The carrier gas is fed in. After the gas in the first and second gas pipelines is mixed, it is introduced into the reaction chamber from the first inlet pipe through the upper gas inlet. The upper gas inlet is located at the top center of the reaction chamber; the upper gas inlet There is a hot wire between the mouth and the substrate table; the third gas pipeline is fed with dopant gas, and the fourth gas pipeline is fed with carrier gas. After the two gases are mixed, they are fed through the second inlet pipe The port 8 leads into the reaction chamber, the second air inlet is connected with the lower air inlet at the bottom of the substrate table, the lower air inlet is located at the center below the substrate table, and is shaped like a trumpet, and the upper and lower air inlets and the substrate table The orthographic projection surface is concentric structure; the upper gas inlet 4 is connected with the first gas pipeline 2 and the second gas pipeline 3, and the aperture of the upper gas inlet is controlled in the range of 1 cm to 2 cm, so as to realize the substrate table The flow rate of the reaction gas is controlled within an appropriate range.

The air inlet pipe 7 is connected with the third road gas pipeline 5 and the fourth road gas pipe 6, and the air inlet pipe is connected with the lower air inlet at the bottom of the substrate table. The air inlet pipe can be made of stainless steel or metal molybdenum. The total flow rate of the dopant mixture gas which is passed into the intake pipe is in the range of several SCCM to tens of SCCM. Substrate stage 9. 7 centimeters to 9 centimeters of height positions below the upper air inlet (mouth) are provided with hot wire 10.

After the gas in the first and second two-way gas pipelines is mixed, it is introduced into the reaction chamber from the first air inlet through the upper air inlet, and the upper air inlet is located at the top center of the reaction chamber; the first and second two-way gas pipelines The position perpendicular to the first air intake pipe, that is, the upper air intake port, according to experiments, the angle between the first and second gas pipes and the first air intake pipe should be about 90 degrees, especially 90 degrees ± 20 degrees, The mixing of methane and hydrogen in the second gas pipeline will be more uniform. The third gas pipeline is fed with dopant gas, and the fourth gas pipeline is fed with carrier gas. The air inlet pipe is introduced into the reaction chamber through the lower air inlet 8; the angle between the third and fourth two-way gas pipes and the second air inlet pipe is about 90 degrees (as shown in the figure). But the angle 90 degree ± 45 degree of the 3rd, the 4th two-way gas pipeline and the second air inlet pipe all can.

Example:

An aperture is opened at the lower part of the substrate table 9 center, and the top is made into a trumpet shape, as the lower air inlet 8, the upper and lower air inlets of the lower air inlet and the substrate table are in a concentric structure, and the upper and lower air inlets do not need With special treatment, the bell mouth expansion angle of the lower air inlet (the angle between the inclined wall of the lower air inlet and the vertical line) is in the range of 0 degrees to 60 degrees, and the doping gas radiates from the center to the surroundings to realize the doping on the surface of the substrate table. Uniform distribution of impurities. as shown in picture 2.

The lower air inlet is located in the center of the substrate table, and its shape is similar to a trumpet. The upper and lower inlets of the lower air inlet and the substrate table are concentric structures. The horizontal height difference between the lower air inlet and the substrate table is between -0.5 cm and -1 centimeters (the minus sign means lower than the horizontal line with the substrate table), the bell mouth expansion angle of the lower air inlet (the angle between the inclined wall of the lower air inlet and the vertical line) is in the range of 0 degrees to 60 degrees, 30- It is better between 50 degrees, and the dopant gas radiates from the center to the surroundings, so as to achieve a relatively uniform distribution of the dopant gas on the surface of the substrate table.

The aperture of the lower inlet of the lower inlet is controlled within the range of 0.2 cm to 1 cm, so as to avoid gas divergence caused by an excessively large aperture, realize uniform distribution of the dopant gas on the substrate table, and avoid affecting the growth gas at the same time.

The upper gas inlet 4 is connected with the first gas pipeline 2 and the second gas pipeline 3, and the aperture of the upper gas inlet is controlled in the range of 1 cm to 2 cm, so that the flow rate of the reaction gas on the substrate table can be controlled at an appropriate scope.

The air inlet pipe 7 is connected with the third road gas pipeline 5 and the fourth road gas pipe 6, and the air inlet pipe is connected with the lower air inlet at the bottom of the substrate table. The air inlet pipe can be made of stainless steel or metal molybdenum. The total flow rate of the dopant mixture gas which is passed into the intake pipe is in the range of several SCCM to tens of SCCM. Substrate stage 9.

The heating wire 10 is arranged at a height of 7 cm to 9 cm below the upper air inlet to ensure that the reaction gas is evenly radiated to the heating wire.

The hot wire is above the substrate stage, and the height between the hot wire and the substrate stage is controlled within a range of 0.4 cm to 1.5 cm, so that the temperature of the surface of the substrate stage can be controlled within an appropriate range.

The first gas pipeline is fed with methane, and the second gas pipeline is fed with hydrogen gas. After the two gases are mixed, the reaction mixture gas is introduced into the reaction chamber 1 through the upper gas inlet, and the flow rate of hydrogen gas is generally controlled at several hundred sccm to several The methane flow rate is generally controlled between several sccm and tens of sccm, and the methane concentration ratio in the reaction mixture gas is controlled between 1% and 10%.

After the reaction mixed gas enters the reaction chamber, due to the action of gravity and air flow, it diffuses towards the substrate stage, and decomposes under the high temperature of the hot wire to form the carbon groups required for the growth of the diamond film.

The third gas pipeline is fed with diborane, and the fourth gas pipeline is fed with hydrogen gas. After the two gases are mixed, they are introduced into the reaction chamber through the inlet pipe and the lower gas inlet. The hydrogen flow rate is controlled at several sccm to several Ten sccm, while the diborane concentration ratio is controlled between tens of ppm to tens of thousands of ppm.

The total flow rate of the doping mixture gas is controlled within tens of sccm, so that the gas can diffuse to the surroundings at a sufficient flow rate, so that the doping uniformity is better, and at the same time, it has little influence on the reaction gas.

In order to verify the effect of the dual-air flow technology HFCVD equipment of the present invention, through simulation modeling, the height of the reaction chamber is set to 22cm, the diameter of the reaction chamber is 22cm, the diameter of the substrate table is 20cm, the aperture of the upper air inlet is 2cm, and the lower inlet of the lower air inlet is 2cm. The horizontal height difference from the substrate table is -0.5 cm, the flare angle of the lower air inlet is 30 degrees, the lower aperture of the lower air inlet is 0.6 cm, and the hot wire is located 8 cm below the lower air inlet, which is in line with the base The vertical height of the film stage is 1.5cm, the temperature of the hot wire is 2773K, the temperature of the substrate stage is 1173K, the pressure in the reaction chamber is 4kPa, the methane flow rate of the upper air inlet is 20sccm, the hydrogen flow rate is 500sccm, and the ethyl boron in the lower air inlet The alkane flow rate was 0.1 sccm, and the hydrogen flow rate was 9.9 sccm.

In the simulation, the specific indicators for measuring the growth rate and doping rate are the concentrations of -CH3 groups and -BH3 groups on the substrate stage. It is generally believed that the higher the concentration of -CH3 groups, the faster the growth rate of the diamond film. The higher the concentration of BH3 groups, the higher the doping concentration of the diamond film.

The simulation results are shown in Figure 3a and Figure 3b, the concentration distribution of -CH3 groups and -BH3 groups is relatively uniform in the range of 2.5 cm to 9.5 cm from the center of the substrate table surface.

Comparative example:

The comparative example is a conventional single-inlet HFCVD equipment, and its reaction chamber 1 and gas introduction structure are shown in FIG. 4 .

The single gas inlet 4 is connected with the first gas pipeline 2, the second gas pipeline 3, and the third gas pipeline 5, and the aperture of the upper gas inlet is controlled in the range of 1 cm to 2 cm, so that the substrate table 9 The flow rate of the upper reaction gas is controlled in an appropriate range.

One (or more) heating wires 10 are arranged at a height of 7 cm to 9 cm below the single air inlet to ensure that the reaction gas is evenly radiated to the heating wires.

The hot wire is above the substrate stage, and the height between the hot wire and the substrate stage is controlled within a range of 0.4 cm to 1.5 cm, so that the temperature of the surface of the substrate stage can be controlled within an appropriate range.

The first gas pipeline feeds methane, the second gas pipeline feeds hydrogen, and the third gas pipeline feeds diborane. The three gases are mixed and then introduced into the reaction chamber through a single gas inlet.

The flow rate of hydrogen in the mixed gas is generally controlled between hundreds of sccm and thousands of sccm, while the flow rate of methane is generally controlled between several sccm and tens of sccm, and the concentration ratio of diborane is controlled between tens of ppm and tens of thousands of ppm , the concentration ratio of methane in the reaction mixture gas is controlled between 1% and 10%.

After the mixed gas enters the reaction chamber, due to the action of gravity and air flow, it diffuses towards the substrate table, and decomposes under the high temperature of the hot wire to form carbon groups required for diamond film growth and boron groups required for doping.

In order to verify the improvement effect of the double-flow technology HFCVD equipment of the present invention on high-efficiency boron doping, through simulation modeling and several implementation benchmarks, the -CH3 group and -BH3 group of the double-flow technology HFCVD equipment and conventional HFCVD equipment are compared .

Set the height of the reaction chamber to be 22cm, the diameter of the reaction chamber to be 22cm, the diameter of the substrate table to be 20cm, the diameter of the single air inlet to be 2cm, the hot wire to be located 8cm below the lower air inlet, and the vertical height to the substrate table to be 1.5cm. The temperature of the hot wire is 2773K, the temperature of the hot wire on the substrate stage is 1173K, the pressure of the reaction chamber is 4kPa, the flow rate of methane at the single gas inlet is 20 sccm, the flow rate of hydrogen is 500 sccm, and the flow rate of diborane is 0.1 sccm.

According to the simulation results, the concentration distribution of -CH3 groups and -BH3 groups in the range of 2.5 cm to 9.5 cm from the center of the surface of the substrate table in HFCVD equipment with dual-flow technology and conventional HFCVD equipment is relatively uniform, as shown in Figure 5a, the double Airflow technology HFCVD equipment-BH3 group concentration is significantly higher than conventional HFCVD equipment-BH3 group, reaching 5 to 10 times, as shown in Figure 5b, dual-airflow technology HFCVD equipment-CH3 group concentration is the same as conventional HFCVD The equipment -CH3 group is not much different.

The simulation analysis of the examples and comparative examples shows that the present invention can be applied to the sample preparation of high-efficiency doping of diamond films, and the utilization efficiency of doping gas is increased by 5 times to 10 times compared with the single gas flow technology, which can realize the Efficient doping. The present inventor carried out dual-airflow technical transformation on the existing HFCVD equipment in the laboratory, and proved through many experiments that the HFCVD equipment with dual-airflow technology can increase the boron-doped concentration of the diamond film to more than 5 times.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also possible. It should be regarded as the protection scope of the present invention.

Claims (7)

1. A high-efficiency doping HFCVD device based on double gas flows is characterized by comprising a reaction cavity and a gas introduction structure, wherein the gas introduction structure comprises four gas pipelines, an upper gas inlet and a lower gas inlet; the reaction gas is introduced into the first path of gas pipeline, the carrier gas is introduced into the second path of gas pipeline, the gases of the first path of gas pipeline and the second path of gas pipeline are mixed and then are introduced into the reaction cavity from the first gas inlet pipe through the upper gas inlet, and the upper gas inlet is positioned at the center of the top of the reaction cavity; a hot wire is arranged between the upper air inlet and the substrate table; doping gas is introduced through a third gas pipeline, carrier gas is introduced through a fourth gas pipeline, the two gases are mixed and then introduced into the reaction cavity from a second gas inlet pipe through a lower gas inlet, the second gas inlet pipe and the lower gas inlet are connected with the lower portion of the substrate table, the lower gas inlet is located in the center of the lower portion of the substrate table and is horn-shaped, and the upper gas inlet, the lower gas inlet and the orthographic projection surface of the substrate table are of a concentric structure.

2. The double-gas-flow-based high-efficiency doping HFCVD apparatus according to claim 1, wherein the upper gas inlet is located at a central position of a top of the reaction chamber, and the aperture of the upper gas inlet is controlled to be in a range of 1 cm to 2cm, so that the flow rate of the reaction gas on the substrate stage is controlled to be in a proper range.

3. The double-gas-flow-based high-efficiency doping HFCVD apparatus according to claim 1, wherein a hot wire is provided at a height of 7 cm to 9 cm below the upper gas inlet, and the reaction gas is uniformly radiated onto the hot wire.

4. The double-gas-flow-based high-efficiency doping HFCVD apparatus according to claim 1, wherein the hot wire is located above the substrate table, and the height of the hot wire and the substrate table is controlled within a range from 0.4 cm to 1.5cm, so that the temperature of the surface of the substrate table is controlled within a proper range.

5. The double-gas-flow-based high-efficiency doping HFCVD device according to claim 1, wherein the lower gas inlet is located at the center of the substrate stage and is shaped like a horn, the upper and lower gas inlets and the substrate stage are concentric, the horizontal height difference between the lower gas inlet and the substrate stage is between-0.5 cm and-1 cm, the flare angle of the lower gas inlet, namely the included angle between the inclined wall of the lower gas inlet and the vertical line, is between 0 and 60 degrees, and the doping gas is radiated from the center to the periphery, so that the more uniform distribution of the doping gas on the surface of the substrate stage is realized.

6. The double-gas-flow-based high-efficiency doping HFCVD apparatus according to claim 1, wherein the aperture of the lower gas inlet is controlled to be in a range of 0.2 cm to 1 cm, so that the gas is prevented from being diffused due to an excessively large aperture, the uniform distribution of the doping gas on the substrate stage is realized, and the influence on the growth gas is avoided.

7. The double-gas-flow-based high-efficiency doping HFCVD apparatus according to claim 1, wherein the gas inlet pipe is connected with the lower gas inlet at a lower part of the substrate table, and is made of stainless steel or molybdenum.

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