Preparation method of high-purity gallium nitride powder

Abstract

The invention discloses a preparation method of high-purity gallium nitride powder. The preparation method of the high-purity gallium nitride powder comprises the following steps that a gallium source and a nitrogen-containing medium are subjected to a nitridation reaction in a plasma reaction system to obtain the gallium nitride powder, and the nitrogen-containing medium is mixed gas of nitrogen and water vapor. According to the preparation method provided by the invention, flammable or explosive and toxic raw materials such as hydrogen, ammonia gas and the like do not need to be used, and nitridation treatment is carried out only by using low-cost high-purity N2, so that the nitridation efficiency is greatly improved at the same temperature, the reaction temperature is reduced, and the nitridation time, the raw material consumption, the energy consumption, the process cost and the like are reduced.

Description

Technical field:

[0001] The present invention relates to the technical field of gallium nitride powder preparation, and in particular to a method for preparing high-purity gallium nitride powder. Background technology:

[0002] In recent decades, the semiconductor industry has become one of the most dynamic sectors of global industrial development. With increasing demands for device performance, silicon-based devices are no longer able to meet the needs of the market for applications requiring high voltage, high temperature, high power, and high energy conversion efficiency. Gallium nitride is a new type of semiconductor material (a third-generation semiconductor material) with high hardness, high carrier mobility, and excellent mechanical and thermal stability. It is an ideal material for high-frequency, high-efficiency power electronic equipment and high-power, high-speed optoelectronic components.

[0003] At present, the preparation methods of gallium nitride crystals mainly include the following methods: (1) MOCVD method, MOCVD (metal organic compound vapor deposition) is a commonly used method for preparing gallium nitride thin films. In this method, trimethyl gallium (TMGa) is usually used as a gallium source and ammonia (NH3) is used as a nitrogen source to generate gallium nitride thin films on a sapphire (Al2O3) substrate through a high-temperature reaction; (2) MBE method, MBE (molecular beam epitaxy) is also a method for preparing gallium nitride. Its characteristics are that it uses a molecular beam of Ga and NH3 as a nitrogen source to achieve the growth of gallium nitride at a relatively low temperature (about 700°C); (3) HVPE method, HVPE (hydride vapor phase epitaxy) uses gallium chloride (GaCl3) and NH3 as gallium and nitrogen sources to grow gallium nitride crystals at a high temperature (about 1000°C); (3) direct nitrogen (1) Chemical deposition method: Gallium nitride (GaN) can be prepared as a loose gray powder by heating metallic gallium in an ammonia stream at high temperature (1050-1100°C); (2) Sol-gel method: Gallium ions are complexed with certain gallium complexes (such as citric acid) to form a gel, which is then decomposed at high temperature and finally converted into GaN powder; (3) Chemical vapor deposition method: Gallium nitride nanowires can be prepared by using metallic gallium or gallium oxide as a gallium source and NH3 as a nitrogen source to deposit on a silicon substrate; (4) Solvothermal method: Gallium nitride powder is prepared by heating reaction in benzene as an organic solvent using GaCl3 as a gallium source and Li3N or NaN3 as a nitrogen source.

[0004] In summary, the preparation of powdered GaN requires gallium and nitrogen sources. Gallium oxide, gallium chloride, or organogallium are typically used as the gallium source, while NH3 or NH3 synthesized from N2 and H2 at high temperature are typically used as the nitrogen source. Current preparation methods still have certain shortcomings: 1. The nitridation efficiency of gallium is low, requiring subsequent processing to remove residual unreacted gallium sources such as gallium oxide; 2. High-quality GaN polycrystals with low impurities and a gallium-to-nitrogen ratio closer to the theoretical value are required as raw materials, which require cost-effective production; 3. Nitridation using NH3 and H2 requires strict safety measures and management, and raises environmental concerns such as high waste gas treatment costs. These issues urgently need to be addressed. Summary of the invention:

[0005] The present invention solves the technical problems existing in the prior art and provides a method for preparing high-purity gallium nitride powder. The present invention activates high-purity nitrogen gas with low-temperature plasma to generate a large amount of high-energy active nitrogen (N) as a nitrogen source, and uses gallium oxide or gallium chloride as a gallium source to produce high-purity single crystal gallium nitride powder.

[0006] The present invention aims to provide a method for preparing high-purity gallium nitride powder, comprising the following steps: subjecting a gallium source to a nitridation reaction with a nitrogen-containing medium in a plasma reaction system to obtain gallium nitride powder, wherein the nitrogen-containing medium is a mixture of nitrogen and water vapor.

[0007] The preparation method proposed in the present invention is a method of nitriding gallium oxide or gallium chloride with a high conversion rate. By adding a nitrogen plasma generator to the gallium nitride preparation reactor, the concentration of high-energy active nitrogen atoms in the reaction system is increased, thereby significantly improving the reaction activity of the nitrogen source and the raw material gallium (such as gallium oxide) to generate gallium nitride, achieving nitridation efficiency in pure nitrogen.

[0008] Compared with the existing technology of obtaining gallium nitride by reacting ammonia with a gallium source, the present invention has the following advantages: 1. The raw materials used in the present invention do not involve flammable, explosive, or toxic gases such as hydrogen and ammonia, but only high-purity nitrogen. 2. The nitridation mechanism proposed in the present invention utilizes high-energy electrons generated by low-temperature plasma to collide with nitrogen, generating a large number of high-energy nitrogen atoms ·N, which react with a gallium source such as gallium oxide to obtain gallium nitride. To further improve the nitridation efficiency, the present invention innovatively proposes introducing a certain amount (5% to 10%) of water vapor to generate ·OH and ·H, accelerate the breakage of Ga-O, promote the formation process of Ga-N, and thus improve the nitridation efficiency of gallium nitride. 3. The nitridation process of the present invention can be carried out at room temperature and pressure. By adjusting the discharge voltage or current, the content of high-energy nitrogen atoms can be tested, and the nitrogen content of gallium nitride can be controlled to achieve purity control of gallium nitride. The reaction process is highly operable and has a high safety factor.

[0009] Preferably, the gallium source is gallium oxide or gallium chloride.

[0010] Preferably, the volume ratio of nitrogen to water vapor in the mixed gas is 9-19:1. The water molecules in the reaction system under the action of strong electric field will generate a large number of hydroxyl radicals (OH), which is beneficial to the breakage of Ga-O and the combination of Ga-N, and meanwhile, the active H can combine with the broken O atoms to generate H2O.

[0011] Preferably, the preparation method specifically comprises the following steps: adding high-purity gallium oxide or gallium chloride powder into a graphite boat, placing the graphite boat into a vacuum tube furnace of a dielectric barrier discharge plasma generator, vacuumizing the tube furnace to 5*10 -3 After the pressure is stabilized at 5*10 Pa, nitrogen with a purity higher than 99.9999% is filled in, and high-purity 5% water vapor is introduced, the nitrogen-water vapor pressure is controlled to be 100 kPa, the tube furnace is heated to 850-950 ℃ for nitriding, and meanwhile, the plasma generator is started, the gallium oxide or gallium chloride powder is intermittently nitrided in the plasma in the tube furnace for 10-30 h, and then the powder is grinded to 2-3 μm to obtain the gallium nitride powder.

[0012] In order to reduce impurities and obtain high-quality GaN, the present application selects a non-oxidizing material for the vessel, a stainless steel tube for the calcination tube, a graphite boat for containing high-purity gallium oxide, and the produced GaN is also deposited into the graphite boat for collection.

[0013] Further preferably, the parameters of the plasma generator are as follows: discharge voltage 10-50 kV, discharge current 1-2 mA / cm 2 , discharge treatment time 55-65 min, nitrogen plasma density 1*10 9 -1*10 10 cm -3 , injection dose 3*10 17 -4*10 17 ions / cm 2 .

[0014] Further preferably, the grinding conditions are as follows: a planetary ball mill, stainless steel beads, a ball-to-material ratio of 15:1, a rotation speed of 200 rpm, and a grinding time of 5 h.

[0015] Further preferably, the tube furnace is heated to 900 ℃ for nitriding, and the gallium oxide or gallium chloride powder is intermittently nitrided in the plasma for 20 h.

[0016] Generally speaking, a higher reaction temperature will lead to a shorter reaction time. The present invention prefers 900°C as the reaction temperature for the following two reasons: First, according to the commonly used process for preparing GaN at this stage, setting the reaction temperature at 850°C to 1000°C is conducive to the formation of GaN, indicating that this temperature range is conducive to the breaking of Ga-O bonds and the replacement of O atoms with active nitrogen atoms to form Ga~N. 900°C is just in the high reaction activity range; second, under high temperature conditions, the nitrogen in the reaction body moves faster and collides more violently. Under the action of the electric field, single molecules are more easily ionized to form high-energy active nitrogen atoms. At the same time, using Bosig+ calculations, it can be seen that the highest concentration of active nitrogen atoms can be produced at a lower electric field of around 1100K, such as Figure 1 shown.

[0017] Preferably, the above preparation method specifically comprises the following steps: firstly evacuate the RF plasma system to 5*10 -3 After Pa, nitrogen with a purity higher than 99.9999% is filled in, and high-purity 5% water vapor is introduced, and the nitrogen-water vapor pressure is controlled at 100kPa. High-purity gallium oxide or gallium chloride powder is evenly sprayed into the radio frequency plasma system. At the same time, the plasma generator is turned on, and the reactor is heated to 850°C to 950°C for nitriding for 10 to 30 hours, and then ground to 2 to 3 μm to obtain the gallium nitride powder.

[0018] More preferably, the parameters of the plasma generator are: discharge voltage 1.0-1.5 kV, power 100-200 W, discharge treatment time 8-12 min, nitrogen plasma density 1×10 10 ~1×10 11 cm -3 , injection dose 1×10 18 ~2×10 18 ions / cm 2 .

[0019] More preferably, the grinding conditions are: planetary ball mill, stainless steel beads, a ball-to-material ratio of 15:1, a rotation speed of 200 rpm, and a grinding time of 5 h.

[0020] More preferably, the reaction furnace is heated to 900° C. for nitriding for 20 hours.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. The present invention does not require the use of flammable, explosive or toxic raw materials such as hydrogen and ammonia. Only low-cost high-purity N2 is used for nitriding treatment, which greatly improves the nitriding efficiency at the same temperature, reduces the reaction temperature, and reduces the nitriding time, raw materials, energy consumption and process costs.

[0023] 2. The reaction system proposed in the present invention has strong operability and a high safety factor, while reducing the influence of other elements on the reaction system. By changing the discharge voltage, the concentration of active nitrogen atoms can be adjusted, thereby conveniently adjusting the nitrogen content, so that gallium nitride has an optimal nitrogen content and reduces the impurity content, which is very helpful to improve the quality controllability and stability of the product. Description of the drawings:

[0024] Figure 1 is the reaction rate of nitrogen ionization reaction under different reaction temperature conditions;

[0025] Figure 2 This is a schematic diagram of a nitriding furnace equipped with a dielectric barrier discharge device in Example 1;

[0026] Figure 3 for Figure 2 Schematic diagram of the structure of electrodes in a dielectric barrier discharge device;

[0027] Figure 4 A schematic diagram of a nitriding furnace equipped with a radio frequency plasma device;

[0028] Explanation of the accompanying symbols: 1. stainless steel mesh; 2. tungsten rod; 3. quartz glass; 4. graphite boat; 5. plasma power supply; 6. filter; 7. vacuum pump; 8. compressor; 9. flow meter; 10. powder feeder; 11. radio frequency plasma; 12. powder collector. Specific implementation method:

[0029] The following examples are provided to further illustrate the present invention, but are not intended to limit the present invention.

[0030] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the experimental materials and reagents herein are conventional commercial products in the art.

[0031] like Figure 1 As shown, a lower electric field at around 1100K can produce the highest concentration of active nitrogen atoms. The preferred nitridation reaction temperature in the following embodiments is 850°C to 950°C.

[0032] Example 1:

[0033] In this embodiment, the nitriding reaction is carried out by installing a nitriding furnace equipped with a dielectric barrier discharge. Figure 2 and Figure 3As shown, the tungsten rod 2 serves as the high-voltage electrode, the stainless steel mesh 1 serves as the ground electrode, and the quartz glass 3 tube wall serves as the dielectric. A plasma power supply 5 applies high voltage to generate a large number of high-energy electrons that collide with high-purity nitrogen and water vapor, producing a large number of high-energy nitrogen atoms, nitrogen free radicals, hydroxyl free radicals, and other active substances. These active substances react with the gallium oxide laid on the graphite boat 4 in a series of reactions to produce gallium nitride. The specific steps are as follows: high-purity gallium oxide powder is added to the graphite boat, evenly laid with a thickness of no more than 2mm, and then placed in a vacuum nitriding furnace with a dielectric barrier discharge plasma generator. Evacuate to 5*10 -3 After the nitriding process, nitrogen with a purity higher than 99.9999% was filled in, and high-purity 5% water vapor was introduced. The nitrogen-water vapor pressure was controlled at 100 kPa. The tube furnace was heated to 900 °C for nitriding. At the same time, the plasma generator was turned on. The parameters of the plasma generator were: discharge voltage 30 kV, discharge current 1.5 mA / cm 2 , discharge treatment time is 60min, nitrogen plasma density is 5×10 9 cm -3 , the injection dose is 3.5×10 17 ions / cm 2 In a plasma nitriding furnace, high-purity gallium oxide powder was discontinuously nitrided in a nitrogen plasma at 900°C for 20 hours. After nitridation, the powder was further ground to 2-3 μm using a planetary ball mill with stainless steel beads at a ball-to-powder ratio of 15:1 and a speed of 200 rpm for 5 hours, yielding gallium nitride powder with a particle size of 5N or higher.

[0034] Example 2:

[0035] The same as Example 1, except that: high-purity 10% water vapor was introduced, the nitrogen-water vapor pressure was controlled to 100 kPa, the tube furnace was heated to 850 ° C for nitriding, and the plasma generator was turned on at the same time. The parameters of the plasma generator were: discharge voltage 10 kV, discharge current 1 mA / cm 2 , discharge treatment time 55min, nitrogen plasma density 1×10 9 cm -3 , the injection dose is 3×10 17 ions / cm 2 In a plasma nitriding furnace, high-purity gallium oxide powder is discontinuously nitrided in nitrogen plasma at 850°C for 30 hours to obtain gallium nitride powder with a purity of more than 5N.

[0036] Example 3:

[0037] The same as Example 1, except that: high-purity 8% water vapor was introduced, the nitrogen-water vapor pressure was controlled to 100 kPa, the tube furnace was heated to 950 ° C for nitriding, and the plasma generator was turned on at the same time. The parameters of the plasma generator were: discharge voltage 50 kV, discharge current 2 mA / cm 2 , discharge treatment time is 65min, nitrogen plasma density is 1×10 10 cm -3 , the injection dose is 4×10 17 ions / cm 2 In a plasma nitriding furnace, high-purity gallium oxide powder is discontinuously nitrided in a nitrogen plasma at 950°C for 10 hours to obtain gallium nitride powder with a purity of more than 5N.

[0038] Example 4:

[0039] In this embodiment, a nitriding furnace equipped with radio frequency plasma is used to carry out the nitriding reaction. Figure 4 As shown, when vacuuming begins, the filter 6, vacuum pump 7 and compressor 8 are turned on to make the vacuum degree of the nitriding furnace reach 5*10 -3 Pa, nitrogen with a purity higher than 99.9999% is simultaneously introduced, and high-purity 5% water vapor is introduced. The nitrogen-water vapor pressure is controlled at 100 kPa by a flow meter 9. High-purity gallium oxide powder is evenly sprayed into the radio frequency plasma 11 system through a powder feeder 10. At the same time, the plasma generator is turned on and the reactor is heated to 900°C for nitriding for 20 hours. The parameters of the plasma generator are: discharge voltage 1.2 kV, power 150 W, discharge treatment time 10 minutes, nitrogen plasma density 5×10 10 cm -3 , the injection dose is 1.5×10 18 ions / cm 2 After the nitridation is completed, the nitrided powder is collected by a powder collector 12 and further ground to 2-3 μm using a planetary ball mill with stainless steel beads, a ball-to-material ratio of 15:1, a planetary ball mill speed of 200 rpm, and a grinding time of 5 h to obtain gallium nitride powder with a particle size of 5N or more.

[0040] Example 5:

[0041] The same as Example 4, except that: high-purity 8% water vapor was introduced, the reactor was heated to 850°C for nitriding for 30 hours, and the parameters of the plasma generator were: discharge voltage 1.0 kV, power 100 W, discharge treatment time 8 minutes, nitrogen plasma density 1×10 10 cm -3 , the injection dose is 1×10 18 ions / cm 2, and obtain gallium nitride powder above 5N.

[0042] Example 6:

[0043] The same as Example 4, except that: high-purity 10% water vapor was introduced, the reactor was heated to 950°C for nitriding for 10 hours, and the parameters of the plasma generator were: discharge voltage 1.5 kV, power 200 W, discharge treatment time 12 minutes, nitrogen plasma density 1×10 11 cm -3 , the injection dose is 2×10 18 ions / cm 2 , and obtain gallium nitride powder above 5N.

[0044] The description of the above embodiments is only used to help understand the technical solution and core ideas of the present invention. It should be pointed out that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention. These improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing high-purity gallium nitride powder, characterized in that: The method comprises the following steps: subjecting a gallium source and a nitrogen-containing medium to a nitridation reaction in a plasma reaction system to obtain gallium nitride powder, wherein the nitrogen-containing medium is a mixed gas of nitrogen and water vapor.

2. The preparation method according to claim 1, characterized in that The gallium source is gallium oxide or gallium chloride.

3. The preparation method according to claim 1, characterized in that The volume ratio of nitrogen to water vapor in the mixed gas is 9 to 19:

1.

4. The preparation method according to any one of claims 1 to 3, characterized in that The specific steps include: adding high-purity gallium oxide or gallium chloride powder into a graphite boat, placing it in a vacuum tube furnace with a dielectric barrier discharge plasma generator, and evacuating to 5*10 -3 After the temperature reaches 100 kPa, nitrogen with a purity higher than 99.9999% is filled in, and high-purity 5% water vapor is introduced. The nitrogen-water vapor pressure is controlled at 100 kPa, and the tube furnace is heated to 850°C to 950°C for nitridation. At the same time, a plasma generator is turned on. In the tube furnace, gallium oxide or gallium chloride powder is discontinuously nitrided in the plasma for 10 to 30 hours and ground to 2 to 3 μm to obtain the gallium nitride powder.

5. The preparation method according to claim 4, characterized in that The parameters of the plasma generator are: discharge voltage 10-50kV, discharge current 1-2mA / cm 2 , discharge treatment time 55~65min, nitrogen plasma density 1×10 9 ~1×10 10 cm -3 , injection dose 3×10 17 ~4×10 17 ions / cm 2 The grinding conditions were as follows: planetary ball mill, stainless steel beads, a ball-to-material ratio of 15:1, a rotation speed of 200 rpm, and a grinding time of 5 h.

6. The preparation method according to claim 4, characterized in that The tube furnace was heated to 900°C for nitridation, and the gallium oxide or gallium chloride powder was discontinuously nitrided in the plasma for 20 hours.

7. The preparation method according to any one of claims 1 to 3, characterized in that The specific steps include: first, evacuate the RF plasma system to 5*10 -3 After Pa, nitrogen with a purity higher than 99.9999% is filled in, and high-purity 5% water vapor is introduced, and the nitrogen-water vapor pressure is controlled at 100kPa. High-purity gallium oxide or gallium chloride powder is evenly sprayed into the radio frequency plasma system. At the same time, the plasma generator is turned on, and the reactor is heated to 850°C to 950°C for nitriding for 10 to 30 hours, and then ground to 2 to 3 μm to obtain the gallium nitride powder.

8. The preparation method according to claim 7, characterized in that The parameters of the plasma generator are: discharge voltage 1.0-1.5 kV, power 100-200 W, discharge treatment time 8-12 min, nitrogen plasma density 1×10 10 ~1×10 11 cm -3 , injection dose 1×10 18 ~2×10 18 ions / cm 2 .

9. The preparation method according to claim 7, characterized in that The grinding conditions were as follows: planetary ball mill, stainless steel beads, a ball-to-material ratio of 15:1, a rotation speed of 200 rpm, and a grinding time of 5 h.

10. The preparation method according to claim 7, characterized in that Heat the reactor to 900°C for nitriding for 20 hours.

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