A manufacturing process and system for a single crystal silicon growth hot zone graphite article

Abstract

The application relates to the technical field of single-crystal silicon heat field material preparation, and discloses a processing and manufacturing process and system of single-crystal silicon growth heat field graphite products. The process comprises the following steps: S1, preparation of a preform, S2, baking treatment, S3, index detection grading, S4, furnace loading zoning, S5, graphitization treatment, and S6, machining forming steps. Through accurate control of the preparation parameters of the preform, establishment of a multi-dimensional index detection grading standard and matching of the furnace loading zoning strategy of the Acheson furnace temperature field, the problems of poor performance uniformity and high impurity content of the graphite products in the traditional process are solved, and the purity, density and size stability of the single-crystal silicon growth heat field graphite are significantly improved. The system comprises a preform preparation unit, a grading detection unit, an intelligent furnace loading unit and a graphitization furnace body, automatic control is introduced, and the strict requirements of large-scale production of single-crystal silicon on heat field materials are met.

Description

Technical Field

[0001] This invention belongs to the field of hot field material preparation technology for monocrystalline silicon production, specifically relating to a processing and manufacturing process and system for monocrystalline silicon growth hot field graphite products. Background Technology

[0002] In the growth of single-crystal silicon, graphite products in the thermal field (such as crucibles, flow guides, heaters, and insulation covers) directly affect the temperature field distribution, purity, and defect rate of crystal growth. Current technologies for preparing graphite products suffer from the following problems: First, insufficient density and impurity control in the preforms lead to performance fluctuations in subsequent graphitized products; second, the calcined products are not precisely graded, and the furnace temperature field distribution is not matched during loading, resulting in significant performance differences within the same batch and insufficient room for improving the yield rate; third, the lack of systematic coordinated control of process parameters makes it difficult to meet the high purity and high density requirements of single-crystal silicon for thermal field materials. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a processing and manufacturing process and system for single-crystal silicon-grown thermal field graphite products.

[0004] The technical solution of the present invention is as follows:

[0005] A processing and manufacturing process for graphite products grown in a single-crystal silicon thermal field includes the following steps:

[0006] S1, Preform preparation: Calcined petroleum coke is mixed with coal tar pitch binder, kneaded, and then formed into a green billet by isostatic pressing.

[0007] S2, Firing process: The green blank is placed in a firing furnace, raised to the set firing temperature under a protective atmosphere and held at that temperature, then cooled to obtain the fired product;

[0008] S3, Index Testing and Grading: The roasted product is tested and classified into at least three levels according to the level of the test index: Grade A, Grade B, and Grade C. The test index shall at least cover surface cracks, bulk density, ash content, and resistivity.

[0009] S4, Furnace Loading Zones: At least Grade A and Grade B roasted products should be loaded into the Atcheson furnace, including:

[0010] Grade A roasted products are placed in the transition zone, which is located on both sides of the middle of the furnace body;

[0011] Grade B roasted products are placed in the core area, which is located at the center of the furnace.

[0012] S5, graphitization treatment: After the protective gas is introduced into the Atchison furnace, the temperature is raised to the target temperature, held at the temperature, cooled, and then taken out of the furnace;

[0013] S6, Machining: The graphitized blank is precision machined to obtain graphite products grown in a single crystal silicon thermal field.

[0014] Preferably, in the process described above, step S1, preform preparation: calcined petroleum coke and coal tar pitch binder are mixed at a mass ratio of 85:15-90:10, kneaded at 150-180℃ for 2-3 hours, and then isostatically pressed to form a green blank, with the green blank density controlled at 1.50-1.60 g / cm³.

[0015] Preferably, in the process described above, step S2, calcination treatment: the green blank is placed in a calcination furnace and heated to 1200-1300℃ at a heating rate of 5-10℃ / h under a nitrogen protective atmosphere, held at that temperature for 20-24 hours, and then naturally cooled to room temperature to obtain the calcined product.

[0016] Preferably, in the process described above, step S3 involves index detection and grading:

[0017] Grade A roasted products: surface cracks < 0.5 mm, bulk density > 1.75 g / cm³, ash content < 30 ppm, resistivity < 50 μΩ·m; Grade B roasted products: surface cracks < 0.5 mm, bulk density 1.65-1.75 g / cm³, ash content 30-80 ppm, resistivity 50-70 μΩ·m;

[0018] Products that do not meet the requirements of Grade A or Grade B are classified as Grade C roasted products.

[0019] Preferably, in the process described above, step S4, furnace loading partitioning:

[0020] It also includes an edge zone, where C-grade roasted materials that can be downgraded are placed, located on both sides of the furnace body.

[0021] Preferably, in the process described above, the criteria for downgrading the grade C roasted product are: crack length < 3mm, bulk density > 1.55g / cm³, ash content < 150ppm, and resistivity < 100μΩ·m.

[0022] Preferably, in the process described above, step S5, graphitization treatment: Argon gas is introduced into the Atchison furnace for protection, and the temperature is increased to the target temperature at a rate of 50-200℃ / h, held for 8-10 hours, and then cooled to below 500℃ in the furnace before being removed from the furnace.

[0023] A single-crystal silicon growth thermal field graphite product processing and manufacturing system for implementing the above process includes:

[0024] Preform preparation unit: includes a kneader, an isostatic press and a green billet storage rack connected in sequence;

[0025] Calcination unit: includes a calcination furnace, a protective gas supply system, and a temperature control module;

[0026] Graded testing unit: includes testing instruments corresponding to each testing indicator;

[0027] Intelligent furnace loading unit: includes a robotic arm;

[0028] Graphitization unit: an Atchison furnace, including furnace body, heating element, protective gas supply system and multi-point temperature sensors;

[0029] Machining unit: including at least one of CNC machining center, CNC lathe, and laser cutting machine.

[0030] Preferably, in the system described above, the grading detection unit is connected to a data processing module for comparing the detection results with preset thresholds and grading them.

[0031] Preferably, in the system described above, the multi-point temperature sensor includes no less than three detection points in both the core area and the transition area.

[0032] The beneficial effects of this invention are as follows:

[0033] Compared with the prior art, the advantages of the present invention are as follows:

[0034] The process of this invention solves the problems of poor uniformity of graphite products and high impurity content in traditional processes by precisely controlling the preform preparation parameters, establishing multi-dimensional index detection and grading standards, and matching the furnace loading zoning strategy with the temperature field of the Atchison furnace. It significantly improves the purity, density and dimensional stability of graphite in the hot zone of single crystal silicon growth.

[0035] This invention reduces the impurity content of preforms and improves density uniformity by purifying raw materials and optimizing process parameters. The established three-level testing standard is precisely matched with the temperature field of the Atchison furnace, which increases the product qualification rate after graphitization from about 90% to over 95%. It can also achieve the special effect of obtaining monocrystalline silicon growth thermal field graphite products of different quality grades by simultaneously graphitizing the same batch of roasted products in one furnace while maximizing the coordination and improvement of the yield, thus achieving efficient resource utilization.

[0036] The system of the present invention includes a preform preparation unit, a grading and detection unit, an intelligent furnace loading unit, and a graphitization furnace body. It introduces automated control to meet the stringent requirements of hot zone materials for large-scale production of monocrystalline silicon and ensure the consistency of product quality. Attached Figure Description

[0037] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0038] Exemplary embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings.

[0039] Example 1

[0040] This embodiment provides a processing and manufacturing process for graphite products grown in a single-crystal silicon thermal field, including the following steps:

[0041] S1, Preform Preparation: Calcined petroleum coke and coal tar pitch binder are mixed, kneaded, and then isostatically pressed to form a green compact. Specifically, in this step, calcined petroleum coke and coal tar pitch binder are mixed at a mass ratio of 85:15-90:10, kneaded at 150-180℃ for 2-3 hours, and then isostatically pressed to form a green compact. The density of the green compact is controlled to be 1.50-1.60 g / cm³.

[0042] S2, Firing Treatment: The green blank is placed in a firing furnace, heated to the set firing temperature under a protective atmosphere and held at that temperature, then cooled to obtain the fired product. Specifically, in this step, the green blank is placed in a firing furnace, heated to 1200-1300℃ at a heating rate of 5-10℃ / h under a nitrogen protective atmosphere, held at that temperature for 20-24 hours, and then naturally cooled to room temperature to obtain the fired product.

[0043] S3, Index Testing and Grading: The roasted product is tested and classified into at least three levels according to the level of the test index: Grade A, Grade B, and Grade C. The test index shall at least cover surface cracks, bulk density, ash content, and resistivity.

[0044] Specifically, in this step, the indicator detection is graded as follows:

[0045] Grade A roasted products: surface cracks < 0.5 mm, bulk density > 1.75 g / cm³, ash content < 30 ppm, resistivity < 50 μΩ·m; Grade B roasted products: surface cracks < 0.5 mm, bulk density 1.65-1.75 g / cm³, ash content 30-80 ppm, resistivity 50-70 μΩ·m;

[0046] Products that do not meet the requirements of Grade A or Grade B are classified as Grade C roasted products.

[0047] S4, Furnace Loading Zones: At least Grade A and Grade B roasted products should be loaded into the Atcheson furnace, including:

[0048] Grade A roasted products are placed in the transition zone, which is located on both sides of the middle of the furnace body;

[0049] The core area, where Grade B calcined products are placed, is located in the center of the furnace. This area can compensate for the performance gap between Grade B calcined products and Grade A calcined products, ultimately making the graphitized products more consistent in terms of performance.

[0050] The core area is the region with the highest temperature inside the furnace, and the transition area is the region with the second highest temperature inside the furnace and a relatively gentle temperature gradient.

[0051] S5, Graphitization treatment: After introducing protective gas into the Atcheson furnace, the temperature is raised to the target temperature, held, cooled, and then removed from the furnace. Specifically, in this step, argon gas is introduced into the Atcheson furnace for protection, the temperature is raised to the target temperature at a rate of 50-200℃ / h, held for 8-10 hours, and then cooled with the furnace to below 500℃ before being removed from the furnace.

[0052] S6, Machining: The graphitized blank is precision machined to obtain graphite products grown in a single crystal silicon thermal field.

[0053] Specifically, in step S4 above, the furnace loading area is further divided into three zones: in addition to the core zone and the transition zone, there is also an edge zone. The edge zone is where C-grade roasted products that can be downgraded are placed. This area is located on both sides of the furnace body and is a relatively low temperature area inside the furnace.

[0054] In this case, the criteria for downgrading C-grade roasted products are: crack length < 3mm, bulk density > 1.55g / cm³, ash content < 150ppm, and resistivity < 100μΩ·m.

[0055] This embodiment describes a single-crystal silicon growth thermal field graphite product processing and manufacturing system that implements the above process, including:

[0056] Preform preparation unit: includes a kneader, an isostatic press and a green billet storage rack connected in sequence.

[0057] Calcination unit: includes a calcination furnace, a protective gas supply system, and a temperature control module.

[0058] The graded detection unit includes a detection instrument corresponding to each detection indicator. Furthermore, the graded detection unit is connected to a data processing module for comparing the detection results with preset thresholds and grading them.

[0059] Intelligent loading unit: including robotic arm.

[0060] Graphitization unit: is an Atchison furnace, including furnace body, heating element, protective gas supply system and multi-point temperature sensor, especially the multi-point temperature sensor includes no less than 3 detection points in the core area and transition area.

[0061] Machining unit: including at least one of CNC machining center, CNC lathe, and laser cutting machine.

[0062] Example 2

[0063] This embodiment, based on embodiment 1, includes the following steps:

[0064] S1, Preform Preparation: Purified calcined petroleum coke (fixed carbon ≥99.5%, particle size 5-20μm) and coal tar pitch binder (softening point 80-100℃) are mixed at a mass ratio of 85:15-90:10 and kneaded at 150-180℃ for 2-3 hours. The green billet is then formed by isostatic pressing (pressure 150-200MPa, holding time 3-5 minutes). The density of the green billet is controlled to be 1.50-1.60g / cm³. The purification treatment of the calcined petroleum coke is to introduce chlorine gas at 800-900℃ and react for 2-3 hours to remove metallic impurities.

[0065] The preform preparation unit includes a kneader (twin-screw kneader, temperature control range 100-200℃, stirring speed 50-100rpm), an isostatic press (pressure range 0-300MPa), and a green billet storage rack connected in sequence.

[0066] S2, Calcination: The green blank is placed in a calcining furnace and heated to 1200-1300℃ at a heating rate of 5-10℃ / h under a nitrogen protective atmosphere. It is held at this temperature for 20-24 hours and then naturally cooled to room temperature to obtain the calcined product.

[0067] The roasting unit includes a roasting furnace (maximum temperature 1500℃, temperature control accuracy ±5℃), a nitrogen generator, and a temperature control module.

[0068] The roasting unit adopts a box-type roasting furnace, equipped with nitrogen with a purity of ≥99.999%.

[0069] S3, Index Testing and Grading: Roasted products are tested and classified into three levels based on the following indicators:

[0070] Grade A roasted products: surface cracks < 0.5 mm, bulk density > 1.75 g / cm³, ash content < 30 ppm, resistivity < 50 μΩ·m; Grade B roasted products: surface cracks < 0.5 mm, bulk density 1.65-1.75 g / cm³, ash content 30-80 ppm, resistivity 50-70 μΩ·m;

[0071] Products that do not meet the requirements of Grade A or Grade B are classified as Grade C roasted products.

[0072] The grading and inspection unit includes a visual inspection component, a laser densitometer, an ash analyzer, and a resistivity meter. The visual inspection component is used to identify surface defects and crack lengths in the roasted product. The laser densitometer has an accuracy of up to 0.001 g / cm³ and can accurately measure bulk density. The ash analyzer uses a LIBS analyzer for non-destructive testing, and the resistivity meter uses a four-probe resistivity meter to directly obtain the required resistivity data. All of these inspection units are connected to a data processing module for comparing the inspection results with preset thresholds and grading them.

[0073] S4, Furnace Loading Zones: Grade A and Grade B roasted products are loaded into the Atchison furnace, where:

[0074] Grade A roasted products are placed in the transition zone (temperature 2500-2800℃). This zone is located on both sides of the middle of the furnace body, 80-130cm away from the heating element.

[0075] Grade B roasted products are placed in the core area (temperature 2800-3000℃). This area is located in the center of the furnace body, 0-80cm away from the heating element.

[0076] It should be noted that the distance from the heating element here is just an example. The zone division of different furnace models is different, and the temperature gradient is the main consideration.

[0077] The intelligent loading unit employs a multi-axis robotic arm, and its intelligence is further reflected in its coordination with furnace temperature field simulation software and loading planning module for control. The loading planning module generates a loading plan based on the grading results and temperature field distribution. Grade A and Grade B roasted products are separated by a graphite felt with a thickness of 5-10cm, and the gap between roasted products of the same grade is ≤5cm.

[0078] S5, graphitization treatment: Argon gas is introduced into the Atchison furnace for protection, and the temperature is increased to the target temperature at a rate of 50-200℃ / h. The temperature is held for 8-10 hours, and the furnace is cooled to below 500℃ before being removed from the furnace.

[0079] The graphitization unit is a 500kW Atchison furnace, including the furnace body, heating element, argon supply system and multi-point temperature sensor (accuracy ±10℃). The multi-point temperature sensor includes at least 3 detection points in the core area and 4 detection points in the transition area, and feeds back temperature data to the temperature control module in real time. The furnace body side wall of the Atchison furnace is marked with partition marks, which allows the multi-axis robotic arm of the intelligent loading unit to accurately position and load the furnace by recognizing the marks.

[0080] S6, Machining: The graphitized blank is machined to obtain graphite products grown in a single crystal silicon thermal field.

[0081] Based on the processing requirements of target hot zone graphite products (crucibles, guide tubes, heaters, etc.), we are equipped with 2 FV-4224 CNC machining centers, 4 GSK980TD CNC lathes, 1 DJ-FCTL403010 laser cutting machine, and corresponding dimensional measuring instruments, which will be selected according to processing needs.

[0082] The central control system prioritizes the use of Siemens PLC systems, which are connected to the preform preparation unit, calcination unit, grading and detection unit, intelligent furnace loading unit, graphitization unit and processing unit for full-process parameter monitoring and adjustment.

[0083] Example 3

[0084] The difference between this embodiment and embodiment 2 is that in step S4 above, the furnace loading area is further divided into three zones: in addition to the core zone and the transition zone, there is also an edge zone (temperature 2200-2500℃). The edge zone is where C-grade roasted products that can be downgraded are placed. This area is located on both sides of the furnace body, 130-180cm away from the heating element.

[0085] In this case, the criteria for downgrading C-grade roasted products are: crack length < 3mm, bulk density > 1.55g / cm³, ash content < 150ppm, and resistivity < 100μΩ·m.

[0086] Example 4

[0087] This embodiment, based on embodiment 3, includes the following steps:

[0088] S1, Preform Preparation: Calcinated petroleum coke (99.6% fixed carbon, particle size 10μm) was purified by chlorine (850℃, 2.5 hours) and mixed with coal tar pitch (softening point 90℃) at a mass ratio of 88:12 in a kneader. The mixture was kneaded at 160℃ for 2.5 hours. The kneaded material was then loaded into a mold and pressed under 180MPa pressure for 4 minutes using an isostatic press to produce a green billet with a density of 1.55g / cm³.

[0089] S2, Firing treatment: The green blank is placed in a firing furnace and heated to 1250℃ at 8℃ / h under a nitrogen atmosphere, held for 22 hours, and then cooled to obtain the fired product.

[0090] S3, Index Testing and Grading: The roasted product with surface cracks <0.5mm, bulk density >1.75g / cm³, ash content <30ppm, and resistivity <50μΩ·m is classified as Grade A. Another batch of roasted products with surface cracks <0.5mm, bulk density 1.65-1.75g / cm³, ash content 30-80ppm, and resistivity 50-70μΩ·m is classified as Grade B. Among the remaining Grade C roasted products, those with crack length <3mm, bulk density >1.55g / cm³, ash content <150ppm, and resistivity <100μΩ·m are selected as products that can be downgraded for use.

[0091] S4, Furnace loading zones: Grade A roasted products are placed in the transition zone (100cm from the heating element) of the Atchison furnace, Grade B roasted products are placed in the core zone (40cm from the heating element), and Grade C roasted products that can be downgraded are placed in the edge zone (150cm from the heating element). Different grades are separated by 8cm thick graphite felt, and the gap between products of the same grade is 3cm. Grade C roasted products that can be downgraded are covered with 2cm thick graphite paper.

[0092] S5, graphitization treatment: Argon gas is introduced, and the temperature is increased to 2900℃ in the core area and 2600℃ in the transition area at 120℃ / h. The temperature is held for 9 hours, and then cooled to 400℃ in the furnace before being taken out.

[0093] S6, Machining: After CNC machining, the transition zone and core zone products meet more than 95% of the technical specifications of the hot zone crucible / insulation cover for monocrystalline silicon growth (certification standards: bulk density > 1.80 g / cm³, compressive strength > 45 MPa, flexural strength > 25 MPa, ash content < 20 ppm, resistivity < 35 μΩ·m, dimensional tolerance ± 0.1 mm). After machining, the edge zone products meet the requirements of bulk density > 1.65 g / cm³, ash content < 100 ppm, resistivity < 60 μΩ·m, and thermal conductivity (1000℃) < 10 W / (m·K), which can meet the usage requirements of the peripheral support structure for monocrystalline silicon growth.

[0094] As can be seen, the embodiments of the present invention also realize the processing and manufacturing process and system for obtaining graphite products (crucibles / insulation covers, peripheral support structures) of different quality grades of single crystal silicon growth hot zone by simultaneously graphitizing the same batch of roasted products in one furnace, based on maximizing coordination and improving the yield, thus achieving efficient utilization of resources.

Claims

1. A processing and manufacturing process for graphite products grown in a single-crystal silicon thermal field, characterized in that, Includes the following steps: S1, Preform preparation: Calcined petroleum coke is mixed with coal tar pitch binder, kneaded, and then formed into a green billet by isostatic pressing. S2, Firing process: The green blank is placed in a firing furnace, raised to the set firing temperature under a protective atmosphere and held at that temperature, then cooled to obtain the fired product; S3, Index Testing and Grading: The roasted product is tested and classified into at least three levels according to the level of the test index: Grade A, Grade B, and Grade C. The test index shall at least cover surface cracks, bulk density, ash content, and resistivity. S4, Furnace Loading Zones: At least Grade A and Grade B roasted products should be loaded into the Atcheson furnace, including: Grade A roasted products are placed in the transition zone, which is located on both sides of the middle of the furnace body; Grade B roasted products are placed in the core area, which is located at the center of the furnace. S5, graphitization treatment: After the protective gas is introduced into the Atchison furnace, the temperature is raised to the target temperature, held at the temperature, cooled, and then taken out of the furnace; S6, Machining: The graphitized blank is precision machined to obtain graphite products grown in a single crystal silicon thermal field.

2. The process according to claim 1, characterized in that, Step S1, Preform preparation: Calcinated petroleum coke and coal tar pitch binder are mixed at a mass ratio of 85:15-90:10 and kneaded at 150-180℃ for 2-3 hours. The green blank is then formed by isostatic pressing, and the density of the green blank is controlled to be 1.50-1.60 g / cm³.

3. The process according to claim 1, characterized in that, Step S2, Firing treatment: Place the green blank in a firing furnace, raise the temperature to 1200-1300℃ at a heating rate of 5-10℃ / h under a nitrogen protective atmosphere, hold for 20-24 hours, and allow it to cool naturally to room temperature to obtain the fired product.

4. The process according to claim 1, characterized in that, Step S3, Index Detection and Grading: Grade A roasted products: surface cracks < 0.5 mm, bulk density > 1.75 g / cm³, ash content < 30 ppm, resistivity < 50 μΩ·m; Grade B roasted products: surface cracks < 0.5 mm, bulk density 1.65-1.75 g / cm³, ash content 30-80 ppm, resistivity 50-70 μΩ·m; Products that do not meet the requirements of Grade A or Grade B are classified as Grade C roasted products.

5. The process according to claim 1, characterized in that, Step S4, Furnace loading zone: It also includes an edge zone, where C-grade roasted materials that can be downgraded are placed, located on both sides of the furnace body.

6. The process according to claim 5, characterized in that, For Grade C roasted products, the criteria for downgrading to Grade C are: crack length < 3mm, bulk density > 1.55g / cm³, ash content < 150ppm, and resistivity < 100μΩ·m.

7. The process according to claim 1, characterized in that, Step S5, graphitization treatment: Argon gas is introduced into the Atchison furnace for protection, and the temperature is increased to the target temperature at a rate of 50-200℃ / h. The temperature is held for 8-10 hours, and the furnace is cooled to below 500℃ before being removed from the furnace.

8. A system for processing and manufacturing single-crystal silicon-grown thermal field graphite products according to any one of claims 1-7, characterized in that, include: Preform preparation unit: includes a kneader, an isostatic press and a green billet storage rack connected in sequence; Calcination unit: includes a calcination furnace, a protective gas supply system, and a temperature control module; Graded testing unit: includes testing instruments corresponding to each testing indicator; Intelligent furnace loading unit: includes a robotic arm; Graphitization unit: an Atchison furnace, including furnace body, heating element, protective gas supply system and multi-point temperature sensors; Machining unit: including at least one of CNC machining center, CNC lathe, and laser cutting machine.

9. The system according to claim 8, characterized in that, The graded detection unit is connected to a data processing module, which is used to compare the detection results with preset thresholds and grade them.

10. The system according to claim 8, characterized in that, The multi-point temperature sensor contains no less than 3 detection points in both the core area and the transition area.

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