Annular silicon rod growth method for silicon component

Abstract

The invention discloses a growth method of an annular silicon rod for a silicon component, which adopts an annular seed crystal and sequentially executes the following steps in a single crystal furnace: charging and melting a silicon material; fixing the annular seed crystal on a seed crystal rope and descending to be welded with the molten silicon liquid; directly performing equal-diameter growth to form an annular silicon rod; taking out through the auxiliary chamber after growth is completed; after replacing the annular seed crystal or supplementing the silicon material, circularly drawing a plurality of annular silicon rods in the same furnace; according to the method, the silicon rod with the annular structure is directly drawn by adopting the annular seed crystal, so that the near-net forming production of a silicon part is realized, and the subsequent processing link of a rod drawing machine required by a traditional directional solidification ingot casting method is omitted, so that the production process is simplified, the manufacturing period is shortened, the utilization rate of a silicon material is also improved, and the production cost is reduced. And a large amount of leftover materials and silicon chips which are difficult to recover are prevented from being generated in the rod drawing process, so that the raw material loss and the comprehensive production cost of silicon parts are reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor material preparation technology, and in particular to a method for growing a ring-shaped silicon rod for silicon components. Background Technology

[0002] With the rapid development of science and technology and the continuous progress of the semiconductor industry, semiconductor equipment technology is constantly iterating and updating, evolving from early basic etching processes to complex and precise advanced processes such as plasma etching. Each breakthrough in key technologies has expanded the application space of semiconductor silicon components, driving them towards higher performance and higher reliability. At the same time, process nodes continue to advance to finer scales, gradually transitioning from earlier larger processes to the current 7nm, 5nm, and even more advanced nodes, placing unprecedentedly stringent requirements on the performance, purity, and quality of semiconductor silicon components.

[0003] In this technological evolution, high-purity single-crystal silicon, with its unique physical and chemical properties, has gradually become a key material in advanced etching processes. Compared to other materials, high-purity single-crystal silicon components cause minimal contamination to integrated circuits during etching and exhibit high process stability. Therefore, it has been widely used in etching equipment for advanced processes such as 7nm and 5nm, becoming an indispensable part of high-end chip manufacturing. However, while Czochralski-grown single crystals offer high purity, they are extremely expensive and involve complex processes. Furthermore, larger diameters result in greater stress, increasing the risk of ingot breakage or cracking during processing. Additionally, larger diameters lead to radial resistivity deviations exceeding 10%, impacting the quality of subsequent chips.

[0004] In addition, in the low-to-mid-end market, to reduce costs, the industry commonly uses the relatively simple directional solidification ingot casting method. This method uses square or round crucibles to grow a single polycrystalline silicon ingot through a one-time feeding, and then uses equipment such as a debonding machine to process it into ring-shaped silicon components. However, this process has several limitations: First, the large feeding volume of square or round crucibles leads to a long production cycle per batch, affecting overall output efficiency; second, the energy consumption of crystal growth and processing is high, which is not conducive to green manufacturing and sustainable development; in addition, the large amount of scrap and silicon chips generated during the debonding process is difficult to recycle and reuse efficiently, which not only wastes raw materials but also further increases the overall cost of silicon materials; finally, with the directional solidification ingot casting method, it is difficult to avoid silicon nitride coating powder entering the silicon ingot, resulting in an increase in hard impurities, which will affect the quality of subsequent chips.

[0005] Therefore, in response to the problems mentioned above, this invention proposes a method for growing a ring-shaped silicon rod for silicon components. Summary of the Invention

[0006] To overcome the problems of existing technologies, such as large material input, long production cycle, high energy consumption, high cost, high carbon and nitrogen impurities, and easy occurrence of rod explosion or cracking during processing, this invention proposes a method for growing ring-shaped silicon rods for silicon components.

[0007] The technical solution of this invention is: a method for growing a ring-shaped silicon rod for silicon components. This method uses a pre-sized ring-shaped bulk seed crystal to directly grow a ring-shaped silicon rod in a single crystal furnace using the Czochralski method, thereby eliminating the traditional Czochralski process of crystal pulling, shoulder formation, and shoulder rotation. The method includes the following steps: S1, a preset weight of silicon raw material and dopant is loaded into the quartz crucible of the single crystal furnace, the furnace is evacuated and heated until the silicon raw material is completely melted to form molten silicon liquid; S2, the annular seed crystal is fixedly installed on the seed crystal rope below the lifting head by a fixing device, and then the annular seed crystal is lowered so that its lower end face contacts the surface of molten silicon to perform temperature stabilization and welding to form a stable crystal connection. The material of the annular seed crystal is monocrystalline silicon or polycrystalline silicon. S3. After the annular seed crystal and molten silicon are firmly fused together, reduce the power of the heater from 3kW to 20kW and control the pulling speed from 0.5cm to 10cm per hour to grow the annular silicon rod with constant diameter. S4, after the annular silicon rod has grown to a preset length with equal diameter, it is removed from the molten silicon, isolated and taken out through the sub-chamber; S5. In a single furnace cycle, replace a new annular seed crystal and repeat steps S2 to S4 to pull the second annular silicon rod. Alternatively, first add silicon material to the quartz crucible through the feeder, wait for it to melt, and then replace the new annular seed crystal and repeat steps S2 to S4. This cycle can be repeated to pull the 2nd to Nth annular silicon rods until the quartz crucible reaches the end of its service life and the furnace is shut down.

[0008] Preferably, the annular seed crystal has an outer diameter of 400-600 mm, an inner diameter of 100-400 mm, and a thickness of 5 mm to 60 mm. The annular seed crystal is processed with four through holes with a diameter of 5-20 mm. The through holes are connected in pairs to form a cross shape. This specific ratio of inner and outer diameters constitutes an annular structure with sufficient mechanical strength and heat dissipation area, which is the key to achieving stable growth and avoiding stress concentration.

[0009] Preferably, in step S1, the loading process involves loading all the silicon material at once, or a step-by-step loading method where a portion of the silicon material is initially loaded, and after it melts, the remaining silicon material is re-loaded through a feeder.

[0010] Preferably, the step-by-step loading method includes: initially loading 300-400 kg of silicon material into a 32-inch quartz crucible, and then adding 200-350 kg of silicon material after it melts; or initially loading 400-500 kg of silicon material into a 36-inch quartz crucible, and then adding 400-500 kg of silicon material after it melts.

[0011] Preferably, in step S2, the annular seed crystal is fixed to the seed crystal rope by a fixing device. This fixing device can ensure the stability of the annular seed crystal during the lifting and growth process. The fixing device is a special clamp or connecting mechanism used to reliably clamp or connect the rigid annular seed crystal to the flexible seed crystal rope. It ensures the posture stability and concentricity of the annular seed crystal and the subsequently grown annular silicon rod during the lifting, rotation and growth process. The fixing method is to connect a molybdenum weight to the bottom of the seed crystal rope. The weight has 4 through holes with a diameter of 5-20mm. The through holes are connected in pairs to form a cross shape. Four molybdenum rods are passed through the 4 through holes of the annular seed crystal to fix and connect the seed crystal.

[0012] Preferably, the annular silicon rod has a hollow annular structure similar to that of an annular seed crystal, and is used to directly process silicon components required for semiconductor etching processes.

[0013] The beneficial effects of this invention are: 1. This invention achieves near-net-shape production of silicon components by directly pulling a ring-shaped silicon rod from a ring-shaped seed crystal. This eliminates the need for the subsequent rod-removing machining step required by the traditional directional solidification ingot casting method. This not only simplifies the production process and shortens the manufacturing cycle, but also improves the utilization rate of silicon materials and avoids the generation of a large amount of difficult-to-recycle scrap and silicon chips during the rod removal process, thereby reducing raw material loss and the overall production cost of silicon components.

[0014] 2. This invention combines high-purity Czochralski growth with direct ring seed crystal forming technology, resulting in ring silicon rods with a purity far superior to polycrystalline silicon materials produced by directional solidification casting (which is difficult to avoid silicon nitride coating powder entering the silicon ingot and introducing hard impurity points), while also being significantly cheaper than traditional Czochralski growth of large-size solid monocrystalline silicon rods.

[0015] 3. Since the silicon rod being grown is a ring-shaped hollow structure, the heat generated during the growth process can be dissipated more effectively through the hollow part in the middle. This structural advantage makes the temperature gradient inside the crystal more uniform, which can reduce the huge thermal stress caused by heat accumulation during the growth and cooling of traditional large-size solid silicon rods, thereby effectively avoiding the risk of the crystal rod "exploding" or cracking during subsequent processing.

[0016] 4. By optimizing the process flow, this invention enables the continuous pulling of multiple annular silicon rods within a single furnace by replacing the annular seed crystal after a single loading (or reloading after initial loading). This "one-pulling-multiple-rods" mode significantly improves the single-furnace capacity of the single crystal furnace and the utilization efficiency of core components such as quartz crucibles, shortens the average production cycle of a unit product, and reduces the energy consumption and equipment wear per unit product.

[0017] 5. The growth method of the present invention eliminates the complex stages of crystal pulling, shoulder formation and shoulder rotation in the traditional Czochralski method, and directly enters the constant diameter growth, which simplifies the difficulty of process control. At the same time, the use of ring seed crystals allows the shape and size of the grown silicon rod to be predetermined, resulting in good consistency. Attached Figure Description

[0018] Figure 1 The diagram shown is a schematic representation of the process preparation flow of the present invention. Figure 2 The diagram shown is a schematic representation of the ring-shaped large seed crystal of the present invention. Figure 3 The diagram shown is a schematic representation of the annular silicon rod of the present invention. Figure 4 The diagram shown is a top view of the annular silicon rod of the present invention.

[0019] Explanation of reference numerals in the attached diagram: 1. Lifting rope; 2. Ring-shaped large seed crystal; 3. Ring-shaped silicon rod; 4. Molybdenum weight; 5. Molybdenum rod. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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 some embodiments of the present invention, but 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.

[0021] Please see Figures 1-4 The present invention provides an embodiment of a method for growing a ring-shaped silicon rod for silicon components: This invention eliminates the complex process of growing solid silicon rods using the traditional Czochralski method and then machining them into rings, and also avoids the material waste and impurity problems associated with casting rods using directional solidification. This method uses a large, pre-sized ring-shaped silicon ring as a seed crystal. In a single-crystal furnace, this ring is fused with molten silicon and then directly grown at the same diameter, thus producing a silicon rod with the desired ring structure in a single operation. This method combines the high purity of the Czochralski method with the low cost and high efficiency of near-net-shape ring forming.

[0022] In this embodiment, the preparation is carried out using a single crystal furnace. The main furnace chamber provides a vacuum or inert gas environment and contains a quartz crucible as a melting container. A heater is used to heat the quartz crucible to melt the silicon material and maintain the temperature. Its power needs to be precisely adjustable. The lifting head and the seed crystal rope connected below it are responsible for clamping and lifting the crystal, and the lifting speed needs to be controlled within the range of 0.5 to 10 cm per hour. The auxiliary chamber is connected to the main furnace chamber but can be isolated. It is specifically used to install, fix and replace the ring-shaped bulk seed crystal through special devices inside, and to remove the grown ring-shaped silicon rod without disturbing the atmosphere of the main furnace chamber. It also includes a quartz feeding bucket for replenishing silicon material during the growth process.

[0023] In this embodiment, the annular seed crystal has an outer diameter of 560 mm, an inner diameter of 355 mm, and a thickness of 5-60 mm. Its material can be monocrystalline silicon or polycrystalline silicon, depending on the crystal structure requirements of the final product. This seed crystal can be obtained from high-purity silicon ingots through methods such as wire cutting. Its annular structure is the fundamental reason why this method can directly grow annular silicon rods.

[0024] Furthermore, the process flow of the present invention will be described in detail below: S1. A preset weight of high-purity polycrystalline silicon raw material and necessary dopants (such as boron, phosphorus, etc.) are loaded into the quartz crucible of the single crystal furnace. The loading method can be a one-time input or a step-by-step strategy of initial loading followed by reloading, depending on the production plan. Then, the furnace chamber is closed and a vacuum operation is performed. High-purity argon gas is then introduced to form a protective atmosphere. The heater is then started and the temperature is slowly raised to above the melting point of silicon material (approximately 1420°C). This process needs to be precisely controlled to avoid thermal shock to the quartz crucible until all the silicon material in the crucible is completely melted to form a uniform and stable molten silicon liquid.

[0025] S2. After the silicon material has completely melted and reached thermal stability, the auxiliary chamber of the single crystal furnace is opened. A pre-processed annular seed crystal with specific dimensions (such as an outer diameter of 560 mm, an inner diameter of 355 mm, and a thickness of 5-60 mm) is securely installed onto the seed crystal rope below the lifting head using a special fixing device (such as a special clamp with a self-locking mechanism). Then, the lifting head is lowered so that the lower end face of the annular seed crystal is slowly immersed into and contacts the surface of the molten silicon. During this process, the temperature must be strictly maintained (i.e., "temperature stabilization") so that the lower end face of the seed crystal can be moderately remelted and achieve a firm lattice connection with the molten silicon (i.e., "fusion bonding").

[0026] S3. After the annular seed crystal and the molten silicon have been successfully fused and stabilized, the growth process directly enters the constant diameter growth stage, eliminating the crystal pulling, shoulder formation and shoulder turning stages in the traditional Czochralski method. In this stage, by reducing the heater power by 3 to 20 kW and simultaneously controlling the pulling speed precisely within the range of 0.5 to 10 cm per hour, the molten silicon is encouraged to continuously and stably crystallize at the solid-liquid interface of the annular seed crystal, thereby growing an annular silicon rod with a cross-sectional shape consistent with the seed crystal and a uniform diameter. The hollow channel formed by this annular structure effectively promotes heat dissipation, optimizes the temperature distribution at the reaction interface, and reduces the thermal stress inside the crystal.

[0027] S4. When the annular silicon rod reaches the preset target length (such as the length required to process a silicon component in the subsequent process) during the constant diameter growth stage, it is slowly lifted out of the molten silicon by the lifting mechanism. The grown annular silicon rod is transferred to the secondary chamber through the isolation valve device of the secondary chamber. Then the secondary chamber is emptied and the rod is taken out. Because the main furnace chamber is always kept isolated, the temperature, pressure and atmosphere inside are maintained, which creates conditions for continuous production.

[0028] S5. After removing the previous silicon rod, immediately install the second annular seed crystal through the auxiliary chamber. Repeat steps S2 to S4 to pull the second annular silicon rod. If the amount of remaining molten silicon in the quartz crucible is insufficient to support the growth of the next silicon rod, the feeder will be activated before replacing the seed crystal to add a preset weight of silicon material to the crucible. After it is completely melted, growth continues. This cycle of "removing the rod - adding material (if needed) - replacing the seed crystal - growth" can be repeated multiple times, so that up to N annular silicon rods can be continuously pulled in one furnace cycle until the quartz crucible reaches its service life limit before the furnace is stopped, which greatly improves the efficiency of single production and equipment utilization.

[0029] This invention provides Embodiment 1: This embodiment uses high-purity polycrystalline silicon ingots as the initial raw material.

[0030] First, load the material. Initially, 400 kg of high-purity polycrystalline silicon raw material and an appropriate amount of boron dopant are loaded into a 32-inch quartz crucible. After the heater has completely melted it, another 200 kg of silicon material is added into the crucible through the quartz feeding bucket. After all the silicon material has melted completely, open the sub-chamber of the single crystal furnace, take a ring-shaped seed crystal with an outer diameter of 560mm and an inner diameter of 355mm. The seed crystal can be single crystal or polycrystalline, with a thickness of 30mm. Fix the large ring-shaped seed crystal to the seed crystal rope of the lifting head using a special device. Then, the fusion and growth are carried out. After stabilizing the temperature and successfully fusing the seed crystal with the molten silicon surface, the heater power is reduced by 8KW, and the pulling speed is controlled to be stabilized at 2.5 cm per hour. The process then proceeds directly to the constant diameter growth stage to grow a ring-shaped monocrystalline silicon rod. Finally, the toroidal silicon rod is pulled in a cycle. Once each toroidal silicon rod has grown to a preset length of 1.2 meters, it is removed through the auxiliary chamber and replaced with a new toroidal seed crystal. This process is repeated continuously in this furnace. After a total of 3 toroidal single crystal silicon rods that meet the requirements are successfully pulled, the furnace is shut down.

[0031] This invention provides Embodiment 2: First, load the material. Initially, 500 kg of high-purity polycrystalline silicon raw material and an appropriate amount of boron dopant are loaded into a 36-inch quartz crucible. After the heater has completely melted it, another 200 kg of silicon material is added into the crucible through the quartz feeding bucket. After all the silicon material has melted completely, open the sub-chamber of the single crystal furnace, take a ring-shaped seed crystal with an outer diameter of 560mm and an inner diameter of 355mm. The seed crystal can be single crystal or polycrystalline, with a thickness of 50mm. Fix the large ring-shaped seed crystal to the seed crystal rope of the lifting head using a special device. Then, the fusion and growth are carried out. After stabilizing the temperature and successfully fusing the seed crystal with the molten silicon surface, the heater power is reduced by 15KW, and the pulling speed is controlled to be stabilized at 4 cm per hour. The process then proceeds directly to the constant diameter growth stage to grow a ring-shaped monocrystalline silicon rod. Finally, the toroidal silicon rod is pulled in a cycle. Once each toroidal silicon rod has grown to a preset length of 1.5 meters, it is removed through the auxiliary chamber and replaced with a new toroidal seed crystal. This process is repeated continuously in this furnace. After a total of 4 toroidal single crystal silicon rods that meet the requirements are successfully pulled, the furnace is shut down.

[0032] Comparative Example 1 provided by the present invention: This comparative example employs the exact same process as traditional Czochralski single crystal growth: crystal pulling, shoulder formation, shoulder rotation, and constant-diameter growth. The goal is to grow a solid silicon rod with a diameter equivalent to the outer diameter (560 mm) of the toroidal silicon rod of this invention. Using a 36-inch crucible, 900 kg of material is loaded at once. After growth, the solid silicon rod needs to be machined into a toroidal silicon component with the same shape as the product of this invention through machining methods such as outer diameter cutting and internal rod hollowing.

[0033] This comparative example uses a four-probe method to measure multiple points radially along the silicon rod, calculating the relative deviation between the maximum and minimum values, a key indicator of crystal uniformity and quality. Fourier transform infrared spectroscopy (FTIR) was used for measurement. Excessive oxygen content can affect the electrical performance of the device. Secondary ion mass spectrometry (SIMS) was also used for measurement. Directional solidification easily introduces silicon nitride impurities. A polarized stress meter was used to observe and assess the stress distribution inside the crystal rod, determining the risk of "rod explosion." Specific results are as follows.

[0034]

[0035] As shown in the table above, the product produced by this invention exhibits better radial resistivity uniformity than the conventional Czochralski large-diameter solid rod of Comparative Example 1. This is because the annular structure improves the thermal field, resulting in a more uniform temperature gradient at the solid-liquid interface, thus growing crystals with a more consistent structure. Observations using a polarizing stress meter reveal that the annular silicon rods of Examples 1 and 2 have uniform internal stress distribution, with no stress concentration areas that could lead to cracking, while the solid rod of Comparative Example 1 exhibits high-stress areas at its edges. In terms of material utilization, this invention achieves >83%, significantly higher than the 45% achieved by the machining method in Comparative Example 1.

[0036] Comparative Example 2 is provided in this invention: This comparative example uses the industry-standard directional solidification ingot casting method. A square crucible is used to add 1200 kg of silicon material at once to grow a large polycrystalline silicon ingot. Then, a large rod-removing machine is used to remove the ring-shaped silicon material (outer diameter 560 mm, inner diameter 355 mm) from the silicon ingot. The rod-removing process generates a large amount of scrap and silicon chips.

[0037]

[0038] As shown in the table above, in terms of impurity control, this invention inherits the advantages of the Czochralski method, with low oxygen and carbon content and a nitrogen content far lower than that of the directional solidification method in Comparative Example 2. This is because the entire process of this invention is completed in a closed single-crystal furnace, avoiding the silicon nitride coating used in the directional solidification method for easy demolding, thus eliminating the pathway for nitrogen impurities to be introduced. Observations using a polarizing stress meter show that the annular silicon rods of Examples 1 and 2 have uniform internal stress distribution, with no stress concentration areas that could lead to cracking, while Comparative Example 2 shows stress at the grain boundaries. In terms of material utilization, this invention achieves >83%, far exceeding the 65% of the rod-shaping method in Comparative Example 2.

[0039] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments that can be applied to other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for growing a ring-shaped silicon rod for silicon components, characterized in that, It includes the following steps: S1, a preset weight of silicon raw material and dopant is loaded into a quartz crucible of a single crystal furnace and heated until the silicon raw material is completely melted, wherein the dopant is one or more of boron, gallium, phosphorus and antimony. S2, fix the pre-sized annular seed crystal on the seed crystal rope below the lifting head, lower the annular seed crystal so that it contacts the surface of the molten silicon, and perform stable temperature welding; S3. After the annular seed crystal and molten silicon are firmly fused together, reduce the heater power and control the pulling speed to grow the annular silicon rod with constant diameter. S4. After the annular silicon rod grows to the preset length, it is lifted out of the molten silicon and taken out through the secondary chamber of the single crystal furnace. S5, replace with a new ring seed crystal, repeat steps S2 to S4, or replenish silicon material through a feeder, wait for it to melt, replace with a new ring seed crystal, and repeat steps S2 to S4 to pull multiple ring silicon rods in a single furnace cycle.

2. The method for growing a ring-shaped silicon rod for silicon components according to claim 1, characterized in that: The annular seed crystal has an outer diameter of 400-600mm, an inner diameter of 100-400mm, and a thickness of 5mm to 60mm. The annular seed crystal is machined with four through holes, each with a diameter of 5-20mm. The through holes are connected in pairs to form a cross shape.

3. The method for growing a ring-shaped silicon rod for silicon components according to claim 2, characterized in that: The annular seed crystal is made of monocrystalline silicon or polycrystalline silicon.

4. The method for growing a ring-shaped silicon rod for silicon components according to claim 1, characterized in that: In step S1, the loading can be done by loading all the silicon material at once, or by loading a portion of the silicon material initially, letting it melt, and then reloading the remaining silicon material through a feeder in stages.

5. The method for growing a ring-shaped silicon rod for silicon components according to claim 4, characterized in that, The step-by-step loading method includes: initially loading 300-400 kg of silicon material into a 32-inch quartz crucible, and then adding 200-350 kg of silicon material after it melts; or initially loading 400-500 kg of silicon material into a 36-inch quartz crucible, and then adding 400-500 kg of silicon material after it melts.

6. The method for growing a ring-shaped silicon rod for silicon components according to claim 1, characterized in that: In step S3, the heater power is reduced by 3kW to 20kW.

7. The method for growing a ring-shaped silicon rod for silicon components according to claim 1, characterized in that: In step S3, the lifting speed is controlled within the range of 0.5cm to 10cm per hour.

8. The method for growing a ring-shaped silicon rod for silicon components according to claim 1, characterized in that: In step S2, the annular seed crystal is fixed to the seed crystal rope by a fixing device. The fixing method involves connecting a molybdenum weight to the bottom of the seed crystal rope. The weight has four through holes with a diameter of 5-20mm. The through holes are connected in pairs to form a cross shape. Four molybdenum rods are passed through the four through holes of the annular seed crystal to fix and connect the seed crystal. This fixing device can ensure the stability of the annular seed crystal during the lifting and growth process.

9. The method for growing a ring-shaped silicon rod for silicon components according to claim 1, characterized in that: In step S5, multiple annular silicon rods are drawn in a single furnace cycle until the quartz crucible reaches its service life and the furnace is shut down.

10. A method for growing a ring-shaped silicon rod for silicon components according to any one of claims 1-9, characterized in that: The ring-shaped silicon rod has a hollow ring structure similar to that of a ring-shaped seed crystal, and is used to directly process silicon components required for semiconductor etching processes.

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