A method for improving the purity and uniformity of graphite products for semiconductors

Abstract

The present invention discloses a method for improving the purity and uniformity of semiconductor graphite products, belonging to the field of graphite production technology. The method comprises steps S1, furnace preparation; S2, furnace loading; S201, loading the lower product layer: loading the products to be processed at equal intervals along the length of the Acheson furnace, and then laying the lower layer resistor material within the group spacing and layer spacing of the lower product layer; S202, loading the upper product layer: the loading position corresponds one-to-one with the lower product layer, and then laying the upper layer resistor material with a resistivity lower than that of the lower layer resistor material within the group spacing and layer spacing of the upper product layer; S3, power supply; S4, air supply; and S5, cooling. The present invention improves each step of the process for producing isostatic graphite in the Acheson furnace and optimizes the corresponding process parameters, thereby effectively improving product purity, increasing uniformity, improving product performance, reducing costs, and reducing scrap rates, thereby meeting the production requirements of isostatic graphite for semiconductors.

Description

Technical Field

[0001] The invention belongs to the technical field of graphite production, and in particular relates to a method for improving the purity and uniformity of graphite products for semiconductors. Background Art

[0002] Isostatic graphite is a high-performance specialty graphite material with electrical conductivity, high strength, high thermal conductivity and high uniformity. These properties make isostatic graphite an important material in the semiconductor industry.

[0003] When graphite is processed into materials such as semiconductor heaters, crucibles, and various structural support components, the requirements for graphite's strength, purity, and uniformity are particularly high. Graphite with high impurities can contaminate the product during the heating phase, while low graphite uniformity can lead to significant performance fluctuations, potentially causing accidents or shortening the product's service life.

[0004] Based on this, graphite is often purified by graphitization during its preparation in the prior art. For example, the invention patent CN107265750A discloses a method for preparing fine-structured graphite, which mentions heating the temperature to 2800°C at 5°C / min and maintaining the temperature for 1 hour. The invention patent CN101823707 discloses a process for producing isostatically pressed graphite, which mentions heating the temperature to 2500°C at 150°C / h and maintaining the temperature for 1 hour. The invention patent CN108584940 discloses a method for rapid cooling of isostatically pressed graphite in an Acheson furnace, which mentions that after a power outage, the insulation material and resistor material in the furnace must be removed for rapid cooling to dissipate heat.

[0005] Although the above-mentioned prior art can achieve a certain purification effect, it has at least the following technical defects in actual implementation:

[0006] First, too fast a heating speed during power transmission can easily lead to a decrease in product crack yield, while increasing the temperature difference between the upper layer and the furnace, resulting in a lower compliance rate of product grades in the upper layer and greater fluctuations in overall uniformity.

[0007] Secondly, cooling the material can easily cause the upper layer temperature to drop rapidly, which further increases the temperature difference between the middle and upper layers and leads to obvious differences in the longitudinal performance of the same product.

[0008] Based on this, the present invention provides a method for improving the purity and uniformity of graphite products for semiconductors to solve the above-mentioned technical defects. Summary of the Invention

[0009] The purpose of the present invention is to provide a method for improving the purity and uniformity of semiconductor graphite products for the first time, so as to at least achieve the purpose of improving the purity and uniformity of the products.

[0010] The purpose of the present invention is achieved through the following technical solutions:

[0011] A method for improving the purity and uniformity of graphite products for semiconductors comprises the following steps:

[0012] S1 Furnace Preparation

[0013] Clean the debris at the bottom of the furnace, lay carbon black, insulation material and resistor material A in order from bottom to top, and alternately install ventilation pipes on both sides of the furnace wall according to the position of the ventilation holes at the bottom of the furnace;

[0014] S2 furnace loading

[0015] S201 Loading the lower layer products: Load the products to be processed at equal distances along the length of the Acheson furnace, and then lay the lower layer resistor material within the lower product group spacing and layer spacing;

[0016] S202: Load the upper layer product: The loading position corresponds to the lower layer product one by one, and then the upper layer resistor material with a resistivity lower than the lower layer resistor material is laid within the upper layer product group spacing and layer spacing;

[0017] S3 power transmission

[0018] After the furnace is loaded, power is supplied. The temperature is raised at a rate of 6-10°C / h within 1800°C. The temperature is raised at a rate of 12-18°C / h between 1800°C and the target temperature. After reaching the target temperature, the furnace is kept warm for 24 hours.

[0019] S4 air supply

[0020] In the high temperature stage, gas is sent for purification through the furnace bottom vent pipe, and different gases are used for purification according to the type of billet;

[0021] S5 Cooling

[0022] After power and gas are supplied, first grab the impurities on the top of the furnace, then use heavy objects to compact the surface material, and then take it out of the furnace after natural cooling.

[0023] As one possible embodiment of the present application, in step S1, the resistivity of the carbon black is higher than 3000 μΩm, and the thickness of the thermal insulation material is greater than 150 mm.

[0024] As one possible embodiment of the present application, in step S1 , the resistivity of the resistor material A is greater than 600 μΩm.

[0025] As one possible embodiment of the present application, in step S2, the resistivity of the lower layer resistor material is 300-500 μΩm, and the resistivity of the upper layer resistor material is 100-300 μΩm.

[0026] As one possible embodiment of the present application, in step S3, a step-by-step temperature increase method is used during power transmission, as follows:

[0027] In the range of RT-1000℃, the temperature is increased at a rate of 6℃ / h;

[0028] At 1000-1200℃, operate at a heating rate of 7℃ / h;

[0029] At 1200-1400℃, operate at a heating rate of 8℃ / h;

[0030] At 1400-1600℃, operate at a heating rate of 9℃ / h;

[0031] At 1600-1800℃, operate at a heating rate of 10℃ / h;

[0032] At 1800-2000℃, operate at a heating rate of 12℃ / h;

[0033] At 2000-2200℃, operate at a heating rate of 14℃ / h;

[0034] At 2200-2400℃, operate at a heating rate of 16℃ / h;

[0035] The temperature was set at 2400°C to the target temperature and the heating rate was 18°C / h.

[0036] As one possible embodiment of the present application, in step S4, the temperature range of the air supply is 2200-2400°C.

[0037] As one possible embodiment of the present application, in step S4, the purification gas is selected from chlorine halogen gas (such as chlorine), carbon tetrafluoride, and fluorocarbon gas (such as tetrafluoroethane).

[0038] As one possible embodiment of the present application, in step S5, the product is naturally cooled to below 600° C. and then taken out of the furnace.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1. Before the purification method of the present invention is adopted, the upper layer temperature is about 2000°C when the temperature in the furnace is 3000°C. After the purification process of the present invention, the temperature of the upper layer product is increased by about 300°C, which can make the two groups of upper layer head and tail products meet the brand requirements (if they do not meet the standards, they will be downgraded or reprocessed). 50 furnace products per year, 100 tons of products per furnace are analyzed. After the upper layer temperature is increased, the performance and purity of the head and tail products at the lowest temperature position meet the standards, and about 6 tons of qualified products are added. Even considering the fluctuation between furnaces, at least 200-300 tons of products entering the warehouse are added each year, which effectively enhances the product brand compliance rate and increases the overall product yield; at the same time, the purity of the upper layer products is improved.

[0041] 2. It can effectively reduce the performance difference between the top and bottom of a single product, thereby effectively improving the uniformity of individual products and the uniformity of the entire furnace. It can greatly reduce cutting waste caused by product performance fluctuations, reducing costs; at the same time, it can increase product yield and service life. If the performance difference between the upper and lower ends of a single product is large, the product must be cut and scrapped. By reducing the difference between the upper and lower ends, this invention can reduce the cutting waste of 100-200 tons of products annually.

[0042] 3. Shorten the product purification cycle, save costs, reduce product oxidation rate and increase yield.

[0043] In summary, the present invention improves each step of the process for producing isostatic graphite in an Acheson furnace and optimizes the corresponding process parameters, thereby effectively improving product purity, increasing uniformity, improving product performance, reducing costs, and reducing scrap rates, and can meet the production requirements of isostatic graphite for semiconductors. Specifically, the ash content of the isostatic graphite for semiconductors purified by the present invention is less than 80 ppm, and the fluctuation of the product end properties (flexural strength, density, resistivity, etc.) is less than ±20%. The ash content is the remaining mass of the product after calcination in a muffle furnace, which can basically be determined as the impurity content. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 : Graphite production flow chart;

[0045] Figure 2 : Furnace preparation diagram;

[0046] Figure 3 : Lower furnace loading diagram;

[0047] Figure 4 : Upper furnace loading diagram;

[0048] Figure 5 : Figure 4 Schematic diagram of the cross-sectional structure in the front view direction;

[0049] In the figure: 1-ventilation pipe, 2-lower layer blank to be processed, 3-lower layer resistor material, 4-upper layer blank to be processed, 5-upper layer resistor material. DETAILED DESCRIPTION

[0050] In the prior art, the graphite purification process has at least the following technical defects when actually implemented:

[0051] First, too fast a heating speed during power transmission can easily lead to a decrease in product crack yield, while increasing the temperature difference between the upper layer and the furnace, resulting in a lower compliance rate of product grades in the upper layer and greater fluctuations in overall uniformity.

[0052] Secondly, cooling the material can easily cause the upper layer temperature to drop rapidly, which further increases the temperature difference between the middle and upper layers and leads to obvious differences in the longitudinal performance of the same product.

[0053] Based on this, the present invention provides a method for improving the purity and uniformity of semiconductor graphite products, comprising the following steps:

[0054] S1 Furnace Preparation

[0055] Clean the debris at the bottom of the furnace, lay carbon black, insulation material and resistor material A in order from bottom to top, and alternately install ventilation pipes on both sides of the furnace wall according to the position of the ventilation holes at the bottom of the furnace;

[0056] S2 furnace loading

[0057] S201 Loading the lower layer products: Load the products to be processed at equal distances along the length of the Acheson furnace, and then lay the lower layer resistor material within the lower product group spacing and layer spacing;

[0058] S202: Load the upper layer product: The loading position corresponds to the lower layer product one by one, and then the upper layer resistor material with a resistivity lower than the lower layer resistor material is laid within the upper layer product group spacing and layer spacing;

[0059] S3 power transmission

[0060] After the furnace is loaded, power is supplied. The temperature is raised at a rate of 6-10°C / h within 1800°C. The temperature is raised at a rate of 12-18°C / h between 1800°C and the target temperature. After reaching the target temperature, the furnace is kept warm for 24 hours.

[0061] S4 air supply

[0062] In the high temperature stage, gas is sent for purification through the furnace bottom vent pipe, and different gases are used for purification according to the type of billet;

[0063] S5 Cooling

[0064] After power and gas are supplied, first grab the impurities on the top of the furnace, then use heavy objects to compact the surface material, and then take it out of the furnace after natural cooling.

[0065] In the present application, compared with the prior art, steps S1 and S4 are optimized by loading the vent pipes on one side of the furnace wall into alternately loading the vent pipes on both sides of the furnace wall, which increases symmetry and is more conducive to the contact between the purified gas and the product. The difficulty in implementing the process lies in the high equipment requirements. The Acheson furnace needs to set symmetrical vent holes at the bottom of the furnace and build refractory bricks to fix the temperature measuring tubes at the corresponding positions. The purified gas is input into the gas distributor through the pipeline, and then the distributor is connected to the vent pipe with a hose for gas supply. The gas supply pipeline needs to be connected to the gas distributors on both sides of the furnace body at the same time for gas supply. If the gas flow meter on one side is obviously too high / low, the gas valve needs to be adjusted to ensure uniform gas supply on both sides. There are many factors that affect the amount of gas supply, such as obvious deviations in the perforation of the vent pipe, fluctuations in the gas supply flow of the pipeline, unevenness of the pipeline input to the distributors on both sides, etc. If the regulating valve still cannot balance the uniform gas supply of the distributors on both sides of the furnace wall, the purified gas cylinders can be used to supply gas separately on both sides.

[0066] Compared with the prior art, step S2 improves the use of resistor materials. In the prior art, the middle and upper layers use resistors of the same resistivity. The present invention uses resistor materials of different resistivities in the middle and upper layers, which can balance the temperature drop of the upper product due to heat dissipation and effectively reduce the temperature difference between the middle and upper layers. The use of low-resistance materials in the upper layer can ensure that more current flows from the conductive electrode to the upper product, increase the temperature of the upper product, and reduce the temperature difference between the upper product and the lower product. The increase in the temperature of the upper layer can improve the purity and performance of the upper product, while reducing the standard deviation of the performance of the entire furnace product and improving the uniformity. This step can effectively solve the problem of low performance and overall unevenness of the upper layer, that is, increase the temperature of the upper layer during the graphitization purification process and reduce the production temperature difference between the products in the middle and upper positions.

[0067] Compared to the prior art, step S3 reduces the power supply heating rate, increases the final temperature holding time, raises the upper layer temperature, and improves the uniformity of the product within the furnace. Although reducing the heating rate and increasing the holding time will increase power consumption and pose the risk of excessive furnace bottom temperature (burn-through), improving the yield rate of upper layer products and reducing the rate of after-sales customer complaints ensures that the weight of products entering the warehouse for sale increases, and the average electricity consumption per unit of entry is lower than that of the prior art, while also accelerating the production cycle.

[0068] The type of gas supply in step S4 needs to be selected according to the type of impurities in the blank. Combined with step S3, extending the holding time in the high-temperature stage can also increase the gas supply and purification time, reduce the ash content of the product, and improve the product purity.

[0069] Compared with the prior art, step S5 reduces the operation of grabbing materials in the initial cooling stage, reduces the heat dissipation of the upper product in the initial cooling stage, ensures that the high-temperature purification time of the upper and lower products is approximately the same, and reduces the risk of oxygen entering the oxidized product. The high surface temperature of the initial grabbing furnace body may cause the grab bucket and the compacting weight to deform or melt, and it is necessary to use a high-temperature resistant alloy grab bucket (with a high-temperature resistant coating on the surface) for operation. After the surface weight is compacted, the temperature in the furnace is difficult to diffuse, which will increase the cooling time, extend the overall production cycle, and increase costs.

[0070] The present invention improves each step of the process for producing isostatic graphite in an Acheson furnace and optimizes corresponding process parameters, thereby effectively improving product purity, increasing uniformity, improving product performance, reducing costs, and lowering scrap rates, thereby meeting the production requirements of isostatic graphite for semiconductors.

[0071] In order to effectively protect the bottom of the Acheson furnace, as one of the possible embodiments of the present application, further limitations are made on the resistivity of the carbon black and the thickness of the insulation material, that is, in step S1, the resistivity of the carbon black is higher than 3000 μΩm, and the thickness of the insulation material is greater than 150 mm.

[0072] During the power supply process, a weak current flows through the bottom of the Acheson furnace, generating heat. Simultaneously, a large amount of heat is diffused downward from the furnace, causing the bottom temperature to overheat. By limiting the resistivity of the carbon black in the present invention, the heat generated by the furnace bottom itself can be minimized, and by limiting the thickness of the insulation material, the downward heat conduction process can be slowed. To effectively prevent cracks in the upper layer product due to overheating, as one possible embodiment of the present application, the resistivities of A and B in step S2 are further limited. Specifically, in step S2, the resistivity of the lower layer resistor material is 300-500 μΩm, and the resistivity of the upper layer resistor material is 100-300 μΩm.

[0073] To prevent the Acheson furnace's bottom temperature from overheating, one possible embodiment of this application further limits the resistivity of resistivity A. Specifically, in step S1, the resistivity of resistor material A must be greater than 600 μΩm. In this solution, resistivity A must be greater than the resistivity of the product layer in the furnace to ensure that as much current as possible flows into the furnace and prevent self-heating of the bottom layer from causing excessive bottom temperature. Furthermore, the particle size of resistor material A must be greater than 20 mm and laid between the vent pipe and the product to ensure that the gas from the vent pipe reaches the product smoothly and evenly.

[0074] In this invention, using resistor materials with different resistivities in two layers of furnace can easily cause the upper layer's product to heat up too quickly, leading to cracks. Therefore, the resistivities of the upper and lower layers of resistor materials must be strictly controlled. The resistor material should be selected based on the type of product being processed, typically using 300-500μΩm resistor material for the lower layer and 100-300μΩm resistor material for the upper layer. Furthermore, using large-particle resistor material (particle size greater than 20mm) can increase the flow space for purified gas within the furnace, while ensuring uniform contact between the purified gas and the product through the ventilation pipes on both sides, further improving product purity and uniformity.

[0075] In order to further improve the purity and uniformity of the product, as one of the embodiments of the present application, the temperature rise method during power transmission is further limited. That is, in step S3, a step-by-step temperature rise method is used during power transmission, as follows:

[0076] In the range of RT-1000℃, the temperature is increased at a rate of 6℃ / h;

[0077] At 1000-1200℃, operate at a heating rate of 7℃ / h;

[0078] At 1200-1400℃, operate at a heating rate of 8℃ / h;

[0079] At 1400-1600℃, operate at a heating rate of 9℃ / h;

[0080] At 1600-1800℃, operate at a heating rate of 10℃ / h;

[0081] At 1800-2000℃, operate at a heating rate of 12℃ / h;

[0082] At 2000-2200℃, operate at a heating rate of 14℃ / h;

[0083] At 2200-2400℃, operate at a heating rate of 16℃ / h;

[0084] The temperature was set at 2400°C to the target temperature and the heating rate was 18°C / h.

[0085] In the present invention, the power transmission temperature rise rate is low in the initial stage, the temperature rise rate is increased in a step-by-step manner in the middle stage, and the insulation time is extended in the high-temperature stage to balance the temperature difference between the upper layer and the middle layer. Compared with the existing technology, the power transmission temperature rise rate is reduced, the final temperature insulation time is increased, the upper layer temperature is increased, and the uniformity of the products in the furnace is increased.

[0086] In order to further improve the purity and uniformity of the product, as one of the possible embodiments of the present application, the temperature of the air supply is further limited, that is, in step S4, the temperature range of the air supply is 2200-2400°C.

[0087] Acheson furnace purification typically begins with gas delivery at high temperatures. The present invention begins with gas delivery at 2200-2400°C and continues until the end of the power-supply operation. Specifically, the gas delivery start temperature is determined by the product type, impurities to be purified, and purification time. The temperature specified in the present invention increases the proportion of activated molecules in the furnace, promotes the forward progress of the purification reaction, and improves the purification effect. Furthermore, the ambient temperature reaches the boiling point of the reactants, ensuring their effective release.

[0088] In order to further improve the purity and uniformity of the product, as one of the possible embodiments of the present application, the purification gas is further limited, that is, in step S4, the purification gas is selected from halogen gases (such as chlorine), carbon tetrafluoride, and fluorocarbon gases (such as tetrafluoroethane).

[0089] In order to reduce the scrap rate of products, as one of the embodiments of the present application, the temperature of the furnace is further limited, that is, in step S5, the product is naturally cooled to below 600° C. before being taken out of the furnace.

[0090] In the prior art, the product often needs to be cooled to room temperature before being taken out of the furnace. However, the present invention can take the product out of the furnace when it is cooled to 600°C, which shortens the overall cooling time and improves production efficiency.

[0091] When the product is exposed to air during the high-temperature stage, there may be an oxidation risk, resulting in a decrease in product yield. If the graphite blank is exposed to air for a long time during the high-temperature stage, it will inevitably cause an oxidation reaction, resulting in a decrease in the product inventory. The product of the present invention undergoes a rapid cooling process when it is unloaded from the high-temperature stage of 600°C. During this process, an extremely thin and dense oxide layer will be formed on the surface of the product. This oxide layer can slow down the process of oxygen contacting the blank. When air contacts the interior, the product temperature is already lower than the temperature required for the oxidation reaction, so a large number of products will not be oxidized and scrapped.

[0092] Next, the specific production process of the graphite of the present invention is described. The specific process flow is as follows: Figure 1 shown.

[0093] Example 1 (taking a square blank to be processed as an example)

[0094] S1 furnace preparation, first lay carbon black (resistivity about 3100μΩm) on the bottom of the furnace, then place insulation material (thickness greater than 150mm) to the height of the vent pipe 1. Then install the vent pipe 1 to the specific vent hole position on both sides of the furnace wall, such as Figure 2 As shown, the ventilation pipes 1 on both sides of the furnace wall are loaded from the furnace head to the furnace tail in sequence, and the ventilation pipes 1 on both sides of the furnace wall are installed alternately. After the ventilation pipes 1 are loaded, resistor material A (particle size 20-40mm) with a resistivity of about 650μΩm is placed to cover the ventilation pipes 1.

[0095] S2 furnace loading, the lower layer of the blank to be processed 2 is placed at a distance of 50-300mm from the furnace head, the center line of the lower layer of the blank to be processed 2 is consistent with the center line of the furnace, that is, the ends of the lower layer of the blank to be processed 2 are at the same distance from the furnace walls on both sides. Load the blanks 2 in the same spacing along the furnace head to the furnace tail. After loading, the lower layer of resistor material 3 (particle size 20-40mm) with a resistivity of about 400μΩm is laid in the group spacing and layer spacing. Figure 3 As shown. Figure 4 As shown, the upper layer of the blank to be processed 4 is loaded in the same manner as the lower layer of the blank to be processed 2, and the blank is aligned with the lower layer of the blank to be processed 2 and then the upper layer of the resistor material 5 (particle size 20-40mm) with a resistivity of about 200μΩm is laid in the group spacing. After loading is completed, the top is covered. The type and loading method of the upper layer of the resistor material 5 between the product layer spacing are the same as those of the lower layer of the resistor material 3, as shown in FIG. Figure 5 shown.

[0096] S3 power transmission, the specific power transmission temperature rise rate is related to the product specifications, formula and pre-process technology, refer to the process table 1:.

[0097] Table 1:

[0098]

[0099]

[0100] S4 gas supply, gas supply starts at power supply stage 9 and ends at the end of power supply operation, and uses carbon tetrafluoride gas for purification, and the gas supply unit consumption is 50kg / h.

[0101] During S5 cooling, after a power outage, remove impurities from the furnace roof with a grab bucket. After natural cooling, use heavy objects to compact the powder at the furnace head, tail, and surface of the furnace. After surface compaction, allow the powder to cool naturally; no further manipulation is required during the cooling process. When the furnace temperature drops below 800°C, begin thinning the surface powder within the furnace. Once below 600°C, begin removing the surface powder from the product and unloading it. The specific cooling cycle is shown in Table 2. If the furnace temperature does not meet cooling requirements, allow natural cooling, and then proceed when the temperature is appropriate.

[0102] Table 2:

[0103] Serial number Cooling operation Cooling days 1 Grab the top layer 1 2 Heavy objects compact the furnace head and tail materials 4 3 Heavy objects compact the furnace charge 5 4 Natural cooling for 35 days 6 5 Grabbing materials on both sides of the furnace wall 41 6 Grabbing materials at the head and tail of the furnace 42 7 Grabbing in the furnace 43 8 The upper product is taken out of the oven 44 9 Grabbing materials on both sides of the furnace wall 45 10 The lower layer products are taken out of the oven 46

[0104] The ash content of the isostatic graphite for semiconductors purified by Example 1 is less than 80 ppm, and the fluctuation of the end performance of the product (flexural strength, density, resistivity, etc.) is less than ±20%. The ash content is the remaining mass of the product after calcination in a muffle furnace, which can basically be determined as the impurity content.

[0105] The foregoing description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Rather, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the concept described herein through the above teachings or techniques or knowledge in the relevant field. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention are intended to be protected by the appended claims.

Claims

1. A method for improving the purity and uniformity of graphite products for semiconductors, characterized in that: The steps include: S1 Furnace Preparation Clean the debris at the bottom of the furnace, lay carbon black, insulation material and resistor material A in order from bottom to top, and alternately install ventilation pipes on both sides of the furnace wall according to the position of the ventilation holes at the bottom of the furnace; S2 furnace loading S201 Loading the lower layer products: Load the products to be processed at equal distances along the length of the Acheson furnace, and then lay the lower layer resistor material within the lower product group spacing and layer spacing; S202: Load the upper layer product: The loading position corresponds to the lower layer product one by one, and then the upper layer resistor material with a resistivity lower than the lower layer resistor material is laid within the upper layer product group spacing and layer spacing; S3 power transmission After the furnace is loaded, power is supplied. The temperature is raised at a rate of 6-10°C / h within 1800°C. The temperature is raised at a rate of 12-18°C / h between 1800°C and the target temperature. After reaching the target temperature, the furnace is kept warm for 24 hours. S4 air supply In the high temperature stage, gas is sent for purification through the furnace bottom vent pipe, and different gases are used for purification according to the type of billet; S5 Cooling After power and gas are supplied, first grab the impurities on the top of the furnace, then use heavy objects to compact the surface material, and then take it out of the furnace after natural cooling.

2. The method for improving the purity and uniformity of semiconductor graphite products according to claim 1, wherein: In step S1, the resistivity of the carbon black is higher than 3000 μΩm, and the thickness of the thermal insulation material is greater than 150 mm.

3. The method for improving the purity and uniformity of semiconductor graphite products according to claim 1, wherein: In step S1 , the resistivity of the resistor material A is greater than 600 μΩm.

4. The method for improving the purity and uniformity of semiconductor graphite products according to claim 1, wherein: In step S2 , the resistivity of the lower layer resistor material is 300-500 μΩm, and the resistivity of the upper layer resistor material is 100-300 μΩm.

5. The method for improving the purity and uniformity of semiconductor graphite products according to claim 1, wherein: In step S3, a step-by-step heating method is used during power transmission, as follows: In the range of RT-1000℃, the temperature is increased at a rate of 6℃ / h; At 1000-1200℃, operate at a heating rate of 7℃ / h; At 1200-1400℃, operate at a heating rate of 8℃ / h; At 1400-1600℃, operate at a heating rate of 9℃ / h; At 1600-1800℃, operate at a heating rate of 10℃ / h; At 1800-2000℃, operate at a heating rate of 12℃ / h; At 2000-2200℃, operate at a heating rate of 14℃ / h; At 2200-2400℃, operate at a heating rate of 16℃ / h; The temperature was set at 2400°C to the target temperature and the heating rate was 18°C / h.

6. A method for improving the purity and uniformity of semiconductor graphite products according to claim 5, characterized in that: In step S4, the temperature range of the air supply is 2200-2400°C.

7. The method for improving the purity and uniformity of semiconductor graphite products according to claim 6, characterized in that: In step S4, the purification gas is selected from halogen gas.

8. The method for improving the purity and uniformity of semiconductor graphite products according to claim 1, wherein: In step S5, the product is naturally cooled to below 600° C. and then taken out of the furnace.

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