Cleaning method of iridium crucible for gallium oxide crystal growth

Abstract

The application belongs to the technical field of crystal growth, and relates to a cleaning method of an iridium gold crucible for gallium oxide crystal growth, which comprises the following steps: placing an iridium gold crucible containing beta-Ga2O3 crystal waste in an atmosphere furnace, vacuumizing, introducing hydrogen, heating the atmosphere furnace to 800-1000 DEG C, keeping constant temperature for 48-72 hours, and then slowly reducing to room temperature; placing the iridium gold crucible in an acid liquid with a volume ratio of water:sulfuric acid:phosphoric acid = 4-6:1-2:3-5, heating to boiling of the acid liquid, and then boiling for 3-4 hours; then reducing to room temperature, rinsing the iridium gold crucible, drying by nitrogen blowing, vacuum plastic packaging of the iridium gold crucible, and standby. The cleaning method of the application does not use any rough mechanical means such as knocking, chiseling, prying and grinding in the cleaning process of the whole iridium gold crucible, efficiently completes the cleaning operation, maximally protects the iridium gold crucible, reduces the loss of the iridium gold crucible, and thus reduces the crystal growth cost.

Description

Technical Field

[0001] This invention belongs to the field of crystal growth technology and relates to the cleaning of iridium crucibles, specifically to a cleaning method for iridium crucibles used in gallium oxide crystal growth. Background Technology

[0002] β-Ga₂O₃, as a representative of ultra-wide bandgap semiconductor materials, has important applications in high-voltage, high-current power devices and solar-blind detection due to its large bandgap, high breakdown field strength, high figure of merit, and short ultraviolet cutoff absorption edge. Given its excellent physicochemical properties, the growth of high-quality, large-size β-Ga₂O₃ crystals has become crucial for scientific research and industrial applications. Among the various melt methods for growing bulk β-Ga₂O₃ crystals, the mold-guided method and the Czochralski method stand out with significant advantages and a clear trend towards industrialization. However, both of these methods require the use of precious iridium crucibles. Currently, the international market price of iridium powder exceeds 1000 RMB / gram, and a set of iridium used for growing 2-inch bulk β-Ga₂O₃ crystals requires approximately 2-2.5 kg, which translates to at least 2-2.5 million RMB – a very expensive cost. Therefore, proper cleaning and maintenance of iridium crucibles to reduce iridium loss is particularly important.

[0003] Currently, iridium loss during crystal growth has been effectively controlled through dynamic oxygen atmosphere regulation; however, there are no relevant studies or reports on the cleaning and rinsing of the iridium crucible after crystal growth.

[0004] Due to the impurities introduced during the multiple growth processes of gallium oxide crystals, such as raw materials (Si, Sn, Fe, Mg, etc.), thermal fields (Al, Zr), and floating matter, the iridium crucible needs to be cleaned and purified regularly to remove all residual material and impurities. Since gallium oxide raw materials are very hard after cooling and solidifying from the molten state and adhere tightly to the crucible, they must be removed mechanically by hammering, chiseling, prying, and grinding. However, excessive force during mechanical removal often damages the crucible, causing cracks and deformation. Over-grinding is also common during grinding, leading to wear and tear on the iridium crucible. Therefore, a non-destructive and simple method for cleaning iridium crucibles is urgently needed. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems existing in the prior art, and to propose a cleaning method for iridium crucibles used for gallium oxide crystal growth. This method is based on high-temperature reducing atmosphere annealing and acidic solution boiling technology to clean the iridium crucible after gallium oxide crystal growth without mechanical damage, thereby reducing the wear and tear of the iridium crucible.

[0006] The technical solution of this invention is:

[0007] A method for cleaning an iridium crucible used for gallium oxide crystal growth includes the following steps:

[0008] (1) Place the iridium crucible containing the β-Ga2O3 crystal waste into an atmosphere furnace and evacuate the furnace until the vacuum level inside the furnace is ≤10. -1 After Pa, continue evacuation for 1-2 hours; continuous evacuation can further reduce the air content in the furnace.

[0009] (2) After hydrogen is introduced into the atmosphere furnace and reaches atmospheric pressure, the hydrogen flow rate is set to 120-180 sccm and continuously introduced for 1-1.5 hours. After reaching atmospheric pressure, a constant flow rate of hydrogen is continuously introduced, which can further improve the purity of hydrogen in the furnace.

[0010] (3) Increase the temperature inside the atmosphere furnace to 800-1000℃ at a rate of 4-5℃ / min, maintain the temperature for 48-72h, and then slowly reduce the furnace temperature to room temperature at a rate of 1-2℃ / min, and take out the iridium crucible.

[0011] (4) Place the iridium crucible in an acidic liquid, wherein the acidic liquid is a mixture of sulfuric acid, phosphoric acid and water, and the volume ratio is water:sulfuric acid:phosphoric acid = 4-6:1-2:3-5, and the volume of water is equal to or greater than the sum of the volumes of sulfuric acid and phosphoric acid; for example, the volume ratio of water:sulfuric acid:phosphoric acid can be 4:1:3, 5:1:4, 5:1:3, 6:1:3, 6:2:4, 6:2:3 or 6:1:5, etc., but is not limited to the listed ratios. Other ratios within this range that meet the limiting conditions are also applicable.

[0012] (5) After heating the acidic liquid to boiling, continue boiling for 3-4 hours; then cool down to room temperature, rinse the iridium crucible, blow it dry with nitrogen, and vacuum seal the iridium crucible for later use.

[0013] Furthermore, in step (1), the atmosphere furnace is a zirconium oxide or alumina atmosphere furnace.

[0014] Furthermore, in step (2), the hydrogen flow rate is 150 sccm and the continuous flow time is 1 hour.

[0015] Furthermore, in step (3), the heating rate is 5℃ / min, and the temperature is raised to 900℃ and held for 72h; the cooling rate is 2℃ / min.

[0016] Furthermore, in step (4), the iridium crucible is placed in a quartz beaker, and an acidic liquid is added to the quartz beaker, the liquid level being 2 to 5 times the height of the iridium crucible.

[0017] Acidic liquids evaporate during boiling, causing the liquid volume to decrease and the liquid level to drop. To ensure that the acidic liquid always covers the iridium crucible during heating, the acidic liquid level needs to be at least twice the height of the iridium crucible. Therefore, the minimum height of the added acidic liquid is twice the height of the iridium crucible; however, to save costs, the maximum height of the acidic liquid is five times the height of the iridium crucible.

[0018] Furthermore, in step (4), the volume ratio of water: sulfuric acid: phosphoric acid is 4:1:3; the water is distilled water or high-purity water, the sulfuric acid is 30% dilute sulfuric acid, and the phosphoric acid is 85% analytical grade phosphoric acid.

[0019] Furthermore, in step (5), the iridium crucible is rinsed three times each with water and alcohol, dried with nitrogen after cleaning, and then vacuum-sealed with a vacuum degree of ≤70kPa for later use.

[0020] The beneficial effects of this invention are:

[0021] (1) Based on the material characteristics of β-Ga2O3 crystal, which has high vapor pressure and is easy to volatilize and decompose at high temperature, this invention uses high-temperature reducing atmosphere annealing technology to decompose all β-Ga2O3 crystal waste in iridium crucible into gaseous Ga and H2O vapor (Ga2O3(S)+3H2(g)=2Ga(g)+3H2O(g)), which is removed along with the carrier gas; at the same time, the reducing atmosphere can also remove the iridium oxide layer introduced during crystal growth (IrO2(S)+2H2(g)=Ir(g)+2H2O(g)); in addition, its reaction temperature is much lower than the melting point of iridium material (2400℃), so the iridium crucible will not be damaged during the high-temperature reducing atmosphere annealing process.

[0022] (2) The present invention removes the residual impurities after the volatilization of β-Ga2O3 crystal waste in the iridium crucible by acidic solution boiling technology, especially removing metallic impurities including Fe, Sn, Mn, Zr, etc., so as to reduce the impurities in the iridium crucible to a minimum for the next preparation of high-purity crystals.

[0023] (3) The cleaning method of the present invention does not use any rough mechanical means such as knocking, chiseling, prying, or grinding during the overall cleaning process of the iridium crucible. While efficiently completing the cleaning operation, it protects the iridium crucible to the greatest extent and reduces the wear and tear of the iridium crucible, thereby reducing the crystal growth cost.

[0024] (4) This invention is not limited to cleaning the iridium crucible after the growth of β-Ga2O3 crystals, but is also applicable to cleaning the iridium crucible after the growth of high vapor pressure oxide crystals using the mold-guided method and the Czochralski method. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the three-dimensional structure of the iridium crucible corresponding to each step of the cleaning method provided in Embodiment 1 of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] To further understand the present invention, it will be further described in conjunction with the accompanying drawings and embodiments.

[0028] Example 1

[0029] This embodiment provides a method for cleaning an iridium crucible used for gallium oxide crystal growth, the steps of which are as follows:

[0030] Will as Figure 1 The iridium crucible containing β-Ga2O3 crystal waste, shown in the upper left corner, was placed in a zirconia atmosphere furnace and evacuated until the vacuum level inside the furnace chamber dropped to 10. -2 After Pa, continue evacuation for 1 hour;

[0031] After high-purity hydrogen is introduced into the atmosphere furnace and reaches atmospheric pressure, a constant hydrogen flow rate of 150 sccm is set and continuously introduced for 1 hour.

[0032] The atmosphere furnace was heated to 800℃ at a rate of 5℃ / min and held at that temperature for 72 hours. After the holding time was completed, the furnace temperature was slowly reduced to room temperature at a rate of 2℃ / min. After the temperature was reduced to room temperature, the furnace door was opened and the iridium crucible was removed and placed in a quartz beaker with a capacity of 3000mL.

[0033] After the above-mentioned high-temperature reducing atmosphere annealing steps, as Figure 1 As shown in the structural diagram of the iridium crucible in the upper right corner, residual impurity particles still adhere to the inner wall of the obtained iridium crucible.

[0034] The operation was carried out in a fume hood. Distilled water, 30% dilute sulfuric acid and 85% analytical grade phosphoric acid were measured in a volume ratio of 4:1:3, mixed to obtain an acidic liquid, and added to a quartz beaker. The liquid level of the added acidic liquid was twice the height of the iridium crucible.

[0035] In a fume hood, gently place the quartz beaker containing the iridium crucible and acidic liquid onto a resistance wire heating furnace. After the acidic liquid boils, continue boiling for 4 hours. After boiling, turn off the power to the resistance wire heating furnace and allow the acidic liquid to cool to room temperature. Pour it into a waste container. Wearing two layers of clean rubber gloves, clean the iridium crucible, rinsing it three times each with water and alcohol. After the above acid boiling steps, as... Figure 1 The diagram of the iridium crucible in the lower right corner shows that the crucible has been thoroughly cleaned. After cleaning, under the condition of wearing a single layer of disposable transparent gloves, it was dried with nitrogen gas. Then, a vacuum of 70 kPa was set, and the iridium crucible was vacuum-sealed to obtain the desired result. Figure 1 The vacuum-sealed iridium crucible shown in the lower left corner is placed in a safe for use.

[0036] Example 2

[0037] This embodiment provides a method for cleaning an iridium crucible used for gallium oxide crystal growth, the steps of which are as follows:

[0038] (1) Place the iridium crucible containing β-Ga2O3 crystal waste into an alumina atmosphere furnace and perform vacuum treatment until the vacuum degree in the furnace cavity drops to 10. -1 After Pa, continue vacuuming for 2 hours;

[0039] (2) After high-purity hydrogen is introduced into the atmosphere furnace and reaches atmospheric pressure, a constant hydrogen flow rate of 120 sccm is set and continuously introduced for 1.5 hours.

[0040] (3) Heat the atmosphere furnace to 900℃ at a rate of 4℃ / min and keep it at that temperature for 60h. After the temperature is kept at that temperature, slowly lower the furnace temperature to room temperature at a rate of 2℃ / min. After the temperature is lowered to room temperature, open the furnace door and take out the iridium crucible and place it in a quartz beaker with a capacity of 5000mL.

[0041] (6) In a fume hood, measure distilled water or high-purity water, 30% dilute sulfuric acid and 85% analytical grade phosphoric acid in a volume ratio of 6:1:5, mix them to obtain an acidic liquid, add it to a quartz beaker, and the liquid level of the added acidic liquid is 5 times the height of the iridium crucible.

[0042] (7) In a fume hood, gently place the quartz beaker containing the iridium crucible and acidic liquid onto a resistance wire heating furnace and heat it. After the acidic liquid boils, continue boiling for 3.5 hours. After boiling, turn off the power to the resistance wire heating furnace and wait for the acidic liquid to cool to room temperature before pouring it into a waste liquid bucket. Wearing two layers of dust-free rubber gloves, clean the iridium crucible by rinsing it three times each with water and alcohol. After cleaning, dry it with nitrogen gas while wearing a single layer of disposable transparent gloves. Then, set the vacuum degree to 50 kPa, vacuum seal the iridium crucible, and place it in a safe for use.

[0043] Example 3

[0044] This embodiment provides a method for cleaning an iridium crucible used for gallium oxide crystal growth, the steps of which are as follows:

[0045] (1) Place the iridium crucible containing β-Ga2O3 crystal waste into a zirconium oxide atmosphere furnace and perform vacuum treatment until the vacuum degree in the furnace cavity drops to 10. -2 After Pa, continue evacuation for 1 hour;

[0046] (2) After high-purity hydrogen is introduced into the atmosphere furnace and reaches atmospheric pressure, a constant hydrogen flow rate of 180 sccm is set and continuously introduced for 1.2 hours.

[0047] (3) Heat the atmosphere furnace to 1000℃ at a rate of 5℃ / min and keep it at that temperature for 48h. After the temperature is kept at that temperature, slowly lower the furnace temperature to room temperature at a rate of 1℃ / min. After the temperature is lowered to room temperature, open the furnace door and take out the iridium crucible and place it in a quartz beaker with a capacity of 4000mL.

[0048] (6) In a fume hood, measure distilled water or high-purity water, 30% dilute sulfuric acid and 85% analytical grade phosphoric acid in a volume ratio of 5:1:3, mix them to obtain an acidic liquid, add it to a quartz beaker, and the liquid level of the added acidic liquid is 3 times the height of the iridium crucible.

[0049] (7) In a fume hood, gently place the quartz beaker containing the iridium crucible and acidic liquid onto a resistance wire heating furnace and heat it. After the acidic liquid boils, continue boiling for 3 hours. After boiling, turn off the power to the resistance wire heating furnace and wait for the acidic liquid to cool to room temperature before pouring it into a waste liquid bucket. Wearing two layers of dust-free rubber gloves, clean the iridium crucible by rinsing it three times each with water and alcohol. After cleaning, dry it with nitrogen gas while wearing a single layer of disposable transparent gloves. Then, set the vacuum degree to 60 kPa, vacuum seal the iridium crucible, and place it in a safe for use.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, alterations, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for cleaning an iridium crucible used for gallium oxide crystal growth, characterized in that, Includes the following steps: (1) Place the iridium crucible containing the β-Ga2O3 crystal waste into an atmosphere furnace and evacuate the furnace until the vacuum level inside the furnace is ≤10. -1 After Pa, continue evacuation for 1-2 hours; (2) After hydrogen is introduced into the atmosphere furnace and reaches atmospheric pressure, the hydrogen flow rate is set to 120-180 sccm and continuously introduced for 1-1.5 hours. (3) Increase the temperature inside the atmosphere furnace to 800-1000℃ at a rate of 4-5℃ / min, maintain the temperature for 48-72h, and then slowly reduce the furnace temperature to room temperature at a rate of 1-2℃ / min, and take out the iridium crucible. (4) Place the iridium crucible in an acidic liquid, wherein the acidic liquid is a mixture of sulfuric acid, phosphoric acid and water, and the volume ratio is water:sulfuric acid:phosphoric acid = 4~6:1~2:3~5, and the volume of water is equal to or greater than the sum of the volumes of sulfuric acid and phosphoric acid. (5) After heating the acidic liquid to boiling, continue boiling for 3-4 hours; then cool down to room temperature, rinse the iridium crucible, blow it dry with nitrogen, and vacuum seal the iridium crucible for later use.

2. The cleaning method according to claim 1, characterized in that, In step (1), the atmosphere furnace is a zirconium oxide or alumina atmosphere furnace.

3. The cleaning method according to claim 1, characterized in that, In step (2), the hydrogen flow rate is 150 sccm and the continuous flow time is 1 hour.

4. The cleaning method according to claim 1, characterized in that, In step (3), the heating rate is 5℃ / min, and the temperature is raised to 900℃ and held for 72h; the cooling rate is 2℃ / min.

5. The cleaning method according to claim 1, characterized in that, In step (4), the iridium crucible is placed in a quartz beaker, and an acidic liquid is added to the quartz beaker, with the liquid level being 2 to 5 times the height of the iridium crucible.

6. The cleaning method according to claim 1, characterized in that, In step (4), the volume ratio of water: sulfuric acid: phosphoric acid is 4:1:3; the water is distilled water or high-purity water, the sulfuric acid is 30% dilute sulfuric acid, and the phosphoric acid is 85% analytical grade phosphoric acid.

7. The cleaning method according to claim 1, characterized in that, In step (5), the iridium crucible is rinsed three times each with water and alcohol. After cleaning, it is dried with nitrogen and then vacuum-sealed. The vacuum degree of the vacuum seal is ≤70kPa and it is placed for later use.

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