CN115896741A - Growth method of large-size diamond wafer - Google Patents

Abstract

The invention relates to the technical field of diamond processing, and discloses a growth method of a large-size diamond wafer, which comprises the following steps: step one, matrix pretreatment: coating diamond powder on a non-diamond material substrate and grinding; step two, constructing gas conditions: sequentially introducing carrier gas, carbon-containing precursor and etching gas, wherein the flow rate of the carrier gas is 500sccm-750sccm, the flow rate of the carbon-containing precursor is 5sccm-75sccm, and the flow rate of the etching gas is 0sccm-5sccm; and step three, increasing power through a microwave power supply to realize plasma discharge, so that carbon elements in the carbon-containing gas are gradually accumulated on the silicon substrate to form a diamond structure, wherein the plasma power is 5-25 kw, and the temperature is less than 800 ℃. By optimizing the gas conditions and the growth temperature, the growth rate of the inner ring and the outer ring of the diamond wafer can be controlled, the defect of uneven growth surface of the diamond is effectively overcome, and the prepared diamond has high purity.

Description

Growth method of large-size diamond wafer

Technical Field

The invention relates to the technical field of diamond processing, in particular to a growth method of a large-size diamond wafer.

Background

Diamond, commonly known as diamond, is an allotrope of graphite, which is one of the hardest substances in nature. It features super-hard, wear-resisting and quick heat-conduction. Polycrystalline diamond is a diamond with irregular lattice arrangement and grows in a heteroepitaxy mode, and has the characteristics of being super-hard, wear-resistant, fast in heat conduction and the like. Due to the excellent physical and chemical properties of polycrystalline diamond, the polycrystalline diamond is widely applied to the advanced fields of communication, semiconductors, energy sources, national defense, aerospace, military weapons and the like.

At present, the wafer of the polycrystalline diamond is often bonded with other semiconductor materials or is grown in an epitaxial mode all the time in the industry, and the wafer is grown by an MPCVD device with low power of 2.45GHz, so that the aim of generating the large-size optical-grade polycrystalline diamond wafer is achieved. However, the prior art processes typically grow only two inches of diamond, with certain limitations. Moreover, according to the characteristics of CVD equipment, in order to ensure that the power density is enough to deposit diamond and a certain growth rate, the growth temperature is generally controlled to be above 850 ℃, and the energy consumption is large. In addition, the method of the prior art can not realize comparatively even deposit, and the diamond growth later stage often can be because of power density's inequality to the angularity is high to appear, the thick both sides thin condition in the middle of the diamond piece is obvious, and thickness difference is great also can cause the later stage difficulty of polishing, easy fracture diamond piece. Meanwhile, the thermal conductivity of the diamond grown by the prior art is not ideal, and can only reach about 1000-1200W/(m.K).

Disclosure of Invention

The invention aims to provide a growth method of a large-size diamond wafer, and aims to solve the problems that large-size diamonds cannot be produced in the prior art, and the diamonds are high in warping degree and easy to crack due to uneven deposition.

In order to achieve the purpose, the invention adopts the following technical scheme: a growth method of large-size diamond wafer is formed by microwave plasma chemical deposition on a non-diamond material substrate, wherein the gas conditions of the microwave plasma chemical deposition are as follows: the flow rate of the carrier gas is 500-750 sccm, the flow rate of the carbon-containing precursor is 5-75 sccm, and the flow rate of the etching gas is 0-5 sccm.

Preferably, as a refinement, the volume ratio of the carrier gas, the carbon-containing precursor and the etching gas is (590-600): (6-40): (0-2).

In the technical scheme, when the gas conditions are optimized, the influence of different gas conditions on the deposition effect of the diamond film is explored, and the research shows that: when the volume ratio of the carrier gas to the carbon-containing precursor to the etching gas is 594; when the gas ratio is 600; when the gas ratio is 600; when the gas ratio is 600; when the gas ratio is 600; the high concentration of methane is beneficial to the formation of the nano-diamond film, but the secondary nucleation rate is increased along with the increase of the planting time, so that the grains are coarse.

Preferably, as a modification, the temperature of the microwave plasma chemical deposition is < 800 ℃.

Preferably, as a modification, the plasma power of the microwave plasma chemical deposition is 5kw to 25kw.

Preferably, as a refinement, the plasma power is 12kw.

Preferably, as a refinement, the carrier gas is hydrogen, helium or argon.

Preferably, as a refinement, the carbon-containing precursor is at least one of methane, carbon dioxide, acetylene.

Preferably, as a refinement, the etching gas is oxygen.

Preferably, as an improvement, the non-diamond material base body is a silicon wafer substrate, and the thickness of the silicon wafer substrate is more than or equal to 3mm.

Preferably, as an improvement, the method for growing the large-size diamond wafer comprises the following steps:

step one, matrix pretreatment: coating diamond powder on a non-diamond material substrate and grinding;

step two, gas conditions are established: sequentially introducing carrier gas, carbon-containing precursor and etching gas, wherein the flow rate of the carrier gas is 500sccm-750sccm, the flow rate of the carbon-containing precursor is 5sccm-75sccm, and the flow rate of the etching gas is 0sccm-5sccm;

and step three, increasing power through a microwave power supply to realize plasma discharge, so that carbon elements in the carbon-containing gas are gradually accumulated on the silicon substrate to form a diamond structure, wherein the plasma power is 5-25 kw, and the temperature is less than 800 ℃.

The principle and the beneficial effects of the technical scheme are as follows: one of the biggest technical difficulties in growing large-size diamond films is to be able to form crystals on top of the non-diamond material, and the other is to ensure that the film does not crack after growth is complete. The biggest difficulty in the current research and development is that the commercially available CVD equipment is purchased in the market, and the CVD equipment cannot deposit large sizes of 4 inches due to the limitation problem of microwave frequency, so that the CVD equipment is a realistic technical barrier. The technical scheme adopts different devices fundamentally, adopts 915MHz self-grinding device (see the Chinese patent CN111101113A in detail), adopts higher power, higher cooling efficiency and a larger cooling table, and realizes the possibility of 4-inch growth. The technical scheme is used for analyzing the reverse reason aiming at the problem that diamond is easy to crack in the prior art, and the key point of the technical scheme is the gas proportion and the reaction speed through a large number of experiments. Based on this, the technical scheme systematically and comprehensively optimizes the preparation process of the diamond, and firstly, non-diamond materials are used as base materials on raw materials. The gas proportion is optimized by taking hydrogen as carrier gas, methane as carbon-containing precursor and oxygen as etching gas, and the gas flow and proportion can ensure that the non-cracking dominant diamond is grown. In the aspect of growth temperature, the technical scheme breaks through the barriers in the prior art, firstly proposes that the growth and deposition of the diamond are carried out under the condition of relatively low temperature below 800 ℃, and the growth temperature of the diamond can be effectively controlled under the condition of ensuring high power by matching with the power and rapid heat dissipation of microwave plasma, thereby ensuring the quality of the diamond and avoiding the cracking problem. The inherent recognition in the field is: after the growth of the diamond is finished, the diamond needs to be slowly and gradually shut down, and the inside of the equipment cavity is maintained in a relatively stable state within 2-3h so as to stabilize the state of the diamond. However, due to one accidental equipment failure, the equipment is directly shut down, but the fact that the direct shutdown is rapidly and naturally cooled within ten minutes is found to play a positive role in controlling diamond cracking is unexpected, and the method has unexpected technical effects. The process of the technical scheme can grow 4-6 inches of diamond, the yield of the four-inch diamond is improved from 0% to about 50% under the technical processes of a monocrystalline silicon round substrate with the thickness of 3mm and above, low-temperature growth and rapid cooling, the gas proportion is combined subsequently, and the yield of the four-inch diamond is finally improved to over 80%, so that the process has very important significance in the field.

Drawings

FIG. 1 is a diagram showing the measurement of diamond material and its size.

Figure 2 is an optical magnification of diamond (magnification 100).

FIG. 3 is a graph of the results of Raman characteristic peaks and Raman peak plate height measurements.

Fig. 4 is a test chart of fundamental wave variation with frequency.

Fig. 5 is a test chart of triple harmonic variation with frequency.

Figure 6 is a thermal conductivity fit.

Detailed Description

The following is a detailed description of the embodiments, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art; the experimental methods used are all conventional methods; the materials, reagents and the like used are all commercially available.

The scheme is summarized as follows:

a growth method of a large-size diamond wafer comprises the following steps:

step one, coating a layer of diamond powder on a silicon wafer substrate, and slightly grinding the diamond powder to ensure that the diamond powder can be uniformly coated and distributed on the surface of the silicon wafer.

And step two, placing the silicon wafer substrate/metal growth table in the equipment reaction cavity, so that the bottom of the silicon wafer substrate/metal growth table can be in full and uniform contact with the bottom of the reaction cavity.

Introducing reaction gas, namely introducing hydrogen at a flow rate of 500-750 sccm, preferably 594-600 sccm; then introducing methane with the flow rate of 25sccm-75sccm, preferably 6sccm-40sccm; the flow rate of oxygen is 0sccm to 5sccm, preferably 0sccm to 2sccm. During the growth, the growth temperature is controlled below 800 ℃, meanwhile, the concentration of oxygen is controlled to be 0.1-0.3%, and the oxygen is taken as etching gas, and the deposition uniformity of the diamond surface can be ensured by properly increasing the oxygen.

And step four, increasing power through a microwave power supply to realize plasma discharge, so that carbon elements in the carbon-containing gas are gradually accumulated on the silicon substrate to form a diamond structure. The plasma power is 5-25 kw. In order to ensure that the growth temperature is not too high, the power can be properly stabilized at 12kw.

And step five, after the diamond deposition, rapidly cooling within 10-20 min.

The invention utilizes MPCVD equipment (associated patent application number: 201811252049.0) with high power and frequency of 915MHz, controls power density and deposition uniformity by adjusting the shape of a plasma group of the equipment, controls the growth rate of inner and outer rings of a diamond wafer through lower growth temperature, adopts the etching action of oxygen, ensures that the growth surface of the diamond is uniform and transparent, can prepare 4-6 inches of large-size diamond, and avoids the cracking problem.

The examples and comparative examples are designed as shown in table 1, and the differences between the examples and comparative examples are only in the arrangement of partial hot conditions and gas conditions, which are detailed in the following table.

TABLE 1

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Experimental example one-product rate detection

The diamonds prepared in the above examples and comparative examples were subjected to dimensional measurement and yield test, wherein the dimensional measurement was measured with a vernier caliper, the finished products were qualified as being 4 inches or more and the diamonds did not crack, the yield was calculated, and 10 repeated experiments were performed for each group, and the results are shown in the following table.

TABLE 2

Treatment group	Size of diamond	Yield (%)
			Example 1	4 inch	30％
Example 2	4 inch	100％
			Comparative example 1	4 inch	0％
Comparative example 2	4 inch	0％
			Comparative example 3	4 inch	0％
Comparative example 4	4 inch	0％
			Comparative example 5	4 inch	0％
Comparative example 6	4 inch	0％
			Comparative example 7	4 inch	50％
Comparative example 8	4 inch	40％
			Comparative example 9	4 inch	40％

From the data in table 2, it can be seen that: the ratio of methane is improved, the yield is greatly reduced, and the granularity of the growing surface is very large. It is preliminarily presumed that the growth rate is too high due to the increase in the amount of methane, and the non-diamond phase content in the diamond film increases, resulting in higher internal stress and thus the cracking is liable to occur. If the methane ratio is too low, the growth rate is extremely slow, and diamond nucleation is very difficult. Reduction of the hydrogen flow rate leads to faster growth and also cracking, and is not successful at present. The hydrogen flow rate may be appropriately increased, which has little effect on cracking, but may decrease the growth rate. The oxygen flow rate increases and the cracking rate increases, but there is also a success rate of around 10%. The higher power density is beneficial to the deposition of the diamond film, the etching effect on the non-diamond phase can be increased while the growth rate is improved, and the quality of the diamond film is improved. The power density is low, the growth rate is slow, the hydrogen atom etching effect is low, the quality of the diamond film is poor, and the thermal conductivity is low. Higher growth temperature favors the attraction of methyl groups in the plasma and the nucleation phase favors rapid deposition, but higher deposition temperature has a greater likelihood of cracking. The nucleation phase is slower at the lower growth temperature, but the cracking phenomenon is not easy to occur.

Experimental example two Diamond optical magnifier image

The physical image of the diamond prepared in example 2 is shown in fig. 1, and the image under 100 times optical magnification is shown in fig. 2.

Experimental example quality testing of Tridiamond

The quality of the diamond prepared in example 2 was measured, and the measurement indexes and the measurement results are as follows:

1. testing the Raman characteristic peak and the Raman peak plate height: two samples were taken for testing and the results are shown in figure 3 and table 3. The result shows that the Raman spectrum characteristic peak of the diamond semiconductor wafer obtained in the example 2 is obvious, and no other impurity peak exists.

TABLE 3

2. And (3) conductivity testing: the test is carried out by a 3w electrical method, and the test environment temperature is 24-25 ℃, the humidity is 55-56% RH. The results are shown in Table 4. Wherein:

thermal conductivity

Where ω is the frequency, l is the heater effective length, l =1500 μm;

TABLE 4

The above description is only an example of the present invention, and the general knowledge of the known specific technical solutions and/or characteristics and the like in the solutions is not described herein too much. It should be noted that, for those skilled in the art, without departing from the technical solution of the present invention, several variations and modifications can be made, and these should also be considered as the protection scope of the present invention, which will not affect the effect of the implementation of the present invention and the practicability of the patent. The scope of the claims of the present application shall be determined by the contents of the claims, and the description of the embodiments and the like in the specification shall be used to explain the contents of the claims.

Claims (10)

1. A growth method of a large-size diamond wafer is characterized by comprising the following steps: the non-diamond material is formed by microwave plasma chemical deposition on a non-diamond material substrate, wherein the gas conditions of the microwave plasma chemical deposition are as follows: the flow rate of the carrier gas is 500-750 sccm, the flow rate of the carbon-containing precursor is 5-75 sccm, and the flow rate of the etching gas is 0-5 sccm.

2. A method for growing large-size diamond wafers as recited in claim 1, wherein: the volume ratio of the carrier gas, the carbon-containing precursor and the etching gas is (590-600): (6-40): (0-2).

3. A method for growing large-size diamond wafers as recited in claim 2, wherein: the temperature of the microwave plasma chemical deposition is less than 800 ℃.

4. A method for growing large-size diamond wafers as recited in claim 3, wherein: the plasma power of the microwave plasma chemical deposition is 5-25 kw.

5. A method for growing large-size diamond wafers as recited in claim 4, wherein: the plasma power was 12kw.

6. A method for growing large-size diamond wafers as recited in claim 5, wherein: the carrier gas is hydrogen, helium or argon.

7. A method for growing large-size diamond wafers as recited in claim 6, wherein: the carbon-containing precursor is at least one of methane, carbon dioxide and acetylene.

8. A method for growing large-size diamond wafers as recited in claim 7 wherein: the etching gas is oxygen.

9. A method of growing large-size diamond wafers as recited in claim 8, wherein: the non-diamond material base body is a silicon wafer substrate, and the thickness of the silicon wafer substrate is more than or equal to 3mm.

10. A method for growing large-size diamond wafers as recited in claim 9, comprising the steps of:

step one, matrix pretreatment: coating diamond powder on a non-diamond material substrate and grinding;

step two, constructing gas conditions: sequentially introducing carrier gas, carbon-containing precursor and etching gas, wherein the flow rate of the carrier gas is 500sccm-750sccm, the flow rate of the carbon-containing precursor is 5sccm-75sccm, and the flow rate of the etching gas is 0sccm-5sccm;

and step three, increasing power through a microwave power supply to realize plasma discharge, so that carbon elements in the carbon-containing gas are gradually accumulated on the silicon substrate to form a diamond structure, wherein the plasma power is 5-25 kw, and the temperature is less than 800 ℃.

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