Guide cylinder and single crystal furnace

Abstract

The invention provides a guide cylinder and a single crystal furnace. The guide cylinder is arranged above a crucible of the single crystal furnace and surrounds a crystal bar lifting area, the guide cylinder is in an upward opening shape, the inner surface of a shell adopts a SiC coating as a protective material, the upper part of the shell is filled with a carbon felt composite material, and the bottom of the shell is of a hollow structure. According to the technical scheme, the design of the guide cylinder is accurately controlled, the crystal growth process is optimized, the longitudinal temperature gradient of a crystal ingot is increased, rapid growth of single crystals is promoted, the radial temperature gradient is reduced, and the radial uniformity of the crystals is improved, so that the defect-free area width of the crystals can be increased; and the high-quality requirement of the silicon single crystal in the advanced process and the stability and repeatability of crystal growth are met.

Description

Technical Field

[0001] The invention relates to the field of semiconductor material manufacturing, and in particular to a guide tube and a single crystal furnace. Background Art

[0002] The first-level silicon wafer (Prime Wafer) used in production is a key material for manufacturing high-performance integrated circuits and semiconductor devices. It is widely used in smart phones, computers, automotive electronics, industrial automation, medical equipment, consumer electronics, Internet of Things, aerospace and storage devices. With the development of technology, the application field of Prime Wafer continues to expand and is crucial to the modern electronics industry. Therefore, improving the quality of Prime Wafer crystals is crucial to the development of the semiconductor industry.

[0003] As the core component of the single crystal silicon growth furnace, the guide tube plays a vital role in the single crystal silicon growth process. It not only affects the crystal growth rate and quality, but also directly affects the production efficiency and cost. Optimizing the design of the guide tube to improve the radial uniformity and growth rate of the crystal is the key to improving the quality of Prime Wafer crystals.

[0004] At present, the existing crystal growth guide tubes and processes have certain limitations in improving crystal quality. For example, the structural design of the traditional guide tube can easily lead to uneven temperature distribution during crystal growth, and it needs to be frequently disassembled and assembled, thus affecting the crystallization quality and stability of the crystal; it is possible that the unreasonable setting of the traditional growth process parameters can easily lead to defects in the crystal, reducing the electrical and mechanical properties of the crystal. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a guide tube and a single crystal furnace, which can improve the effect of the guide tube.

[0006] In order to solve the above problems, the present invention provides a guide tube, which is placed above the crucible of the single crystal furnace and arranged around the crystal rod pulling area. The guide tube is open upward, and the inner surface of the shell adopts SiC coating as a protective material. The upper part is filled with carbon felt composite material, and the bottom is a hollow structure.

[0007] Optionally, a water cooling jacket is embedded in the inner wall of the guide tube. The water cooling jacket is made of high temperature resistant stainless steel. The inner wall of the water cooling jacket is a roughened surface with a roughness between Ra0.1 and Ra4.5. Or the inner part of the water cooling jacket is a roughened surface and the other part is a mirror surface, and the proportion of the roughened surface is less than 75%.

[0008] Optionally, a transverse flow guide hole is further provided at the bottom of the flow guide tube.

[0009] Optionally, the guide holes are evenly distributed along the side wall of the bottom, and the total opening area accounts for less than 50% of the entire wall surface.

[0010] In order to solve the above problems, the present invention provides a single crystal furnace, characterized in that it includes a crucible, and a guide tube is arranged above the crucible and around the crystal rod pulling area. The guide tube is open upward, and the inner surface of the shell adopts SiC coating as protective material, the upper part is filled with carbon felt composite material, and the bottom is a hollow structure.

[0011] Optionally, the guide tube remains in a fixed position during the process of pulling and growing the single crystal.

[0012] The above technical solution increases the longitudinal temperature gradient of the ingot and promotes the rapid growth of single crystals by precisely controlling the design of the guide tube and optimizing the crystal growth process. At the same time, it reduces the radial temperature gradient and improves the radial uniformity of the crystal, thereby increasing the width of the defect-free area of ​​the crystal to meet the high quality requirements of advanced process silicon single crystals and the stability and repeatability of crystal growth. Silicon single crystals used in advanced processes require COP (Crystal Originated Pit) <15nm and L-pits (Large-etching pits) to be 0. The requirements for oxygen content are determined according to the specific application scenario and process technology. The oxygen content that meets the advanced process (such as 7nm and below) needs to be controlled within 1×10 17 atoms / cm 3 to 1×10 18 atoms / cm 3 the following. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Attached Figure 1 Shown is a schematic structural diagram of a guide tube according to a specific embodiment of the present invention.

[0014] Attached Figure 2 The figure shows a schematic diagram of the side structure of the guide tube according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0015] The specific implementation manner of the guide tube and the single crystal furnace provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0016] Attached Figure 1The figure is a schematic diagram of the structure of the guide tube of a specific embodiment of the present invention. The guide tube 11 is placed above the crucible 12 of the single crystal furnace 10, and is arranged around the pulling area of ​​the crystal rod 13. In order to clearly illustrate the above structure, the crystal rod 13 is specifically given in this specific embodiment. In the actual device, the crystal rod 13 is a product rather than a part of the device. The guide tube 11 is open upward, and the inner surface of the shell 111 adopts SiC coating as a protective material. The upper part 112 of the guide tube is filled with soft or hard carbon felt composite material, and the bottom 113 of the guide tube is a hollow structure.

[0017] The shape and size of the guide tube 11 will affect the flow path and distribution of the heat flow. The upward open conical design is conducive to guiding the flow of the protective gas and reducing turbulence. The guide tube 11 is upward open, the shell 111 uses SiC coating as the coating material, the upper part 112 of the guide tube is filled with carbon felt composite material, and the bottom 113 of the guide tube is a hollow structure. Figure 1 As shown. During the crystal growth process, if a material with high emissivity is used as the guide tube 11, the efficiency of radiation heat transfer can be increased, thereby affecting the temperature distribution. On the contrary, a material with low emissivity will reduce the impact of radiation heat transfer. In order to ensure the structural stability of the guide tube and the uniformity of the temperature distribution, it is necessary to select a material with a thermal expansion coefficient that is compatible with the crystal growth process. Carbon felt composite material refers to a pure carbon multiphase structure composed of carbon fiber or its fabric as a reinforcing phase, chemical vapor infiltration pyrolytic carbon or liquid phase impregnation-carbonized resin carbon, asphalt carbon as a matrix. The use of this material to make a guide tube can effectively reduce the damage to the guide tube caused by factors such as thermal stress and external forces due to its excellent properties, such as high strength, high thermal conductivity, low thermal expansion coefficient, and thermal shock resistance, thereby extending the service life of the guide tube and reducing the maintenance cost of the equipment. At the same time, its good thermal conductivity helps to quickly transfer and evenly distribute heat, provides a stable thermal field environment for the growth of single crystal silicon, and improves the production efficiency and yield of single crystal silicon.

[0018] The coating of the guide tube 11 is a key factor in its design, which not only affects the service life of the guide tube 11, but also affects the quality and efficiency of crystal growth. Silicon carbide coating has become the first choice for surface coating of carbon / carbon thermal field materials due to its excellent thermal shock resistance, wear resistance and high temperature resistance. SiC coating can be generated on the surface of the guide tube through a chemical vapor deposition (CVD) process to improve its oxidation resistance and thermal shock resistance; the application of coating technology can significantly improve the performance of the guide tube, thereby improving the efficiency and quality of single crystal silicon growth. By optimizing the coating of the guide tube 11, heat loss can be reduced, the stability and repeatability of crystal growth can be improved, and the high quality requirements of advanced process silicon single crystals can be met.

[0019] In this specific embodiment, the bottom 113 of the guide tube 11 is further provided with transverse guide holes 114. Preferably, the guide holes 114 are arranged along the side wall of the bottom. The outer side wall of the bottom 113 of the guide tube 11 (viewed from the AA direction) is provided with two layers of guide holes evenly distributed along the circumference, and preferably are circular holes. The circumferential positions of the two layers of circular holes are staggered, such as Figure 2 As shown. The circular hole is conducive to the heat radiation of the side heater to the cavity of the guide tube 11. The cavity transfers the radiated heat to the inside after homogenizing. The heat is collected on the lower inner wall of the guide tube 11 and homogenized, and then radiated to the surface of the crystal rod 13, so that the axial temperature of the surface of the crystal rod 13 is more uniform. The uniform distribution of the guide holes on the guide tube 11 can ensure that the airflow can be uniformly guided at all positions on the surface of the crystal rod 13. This uniform distribution can effectively reduce the radial temperature gradient and improve the radial uniformity of the crystal rod 13. The total area of ​​the openings accounts for less than 50% of the entire wall surface. If the number of guide holes 114 is too small, it may not be possible to effectively guide the airflow to flow evenly through the surface of the crystal rod 13, resulting in uneven temperature distribution and affecting the quality and speed of crystal growth. Excessive number may reduce the structural strength of the guide tube 11 and may cause confusion of the airflow, which is also not conducive to the stable growth of the crystal. Therefore, the most suitable number of guide holes should be determined according to the above principles through precise calculation and experimental verification to achieve the best airflow guiding effect.

[0020] In this specific embodiment, a water cooling jacket 14 is embedded in the inner wall of the guide tube 11. The water cooling jacket 14 is made of high temperature resistant stainless steel, and the inner wall of the water cooling jacket 14 is a roughened surface, and the roughness is preferably between Ra0.1-Ra4.5; or part of the surface is a roughened surface, and part of it is a mirror surface, and the proportion of the roughened surface is preferably less than 75%. Water cooling jacket 14 embedded in the guide tube 11: The conventional guide tube 11 and the water cooling jacket 14 are independent, and the position of the water cooling jacket 14 will also affect the stability of temperature control. If the water cooling jacket 14 is placed in a position that is easily disturbed by the outside world, such as near a heat source or an area with unstable airflow, it may cause large temperature fluctuations. This will affect the stability and repeatability of crystal growth and reduce the quality of the product. Embedded in the guide tube 11 can reduce the impact of external factors on the water cooling jacket 14 and improve the stability of temperature control. The water cooling jacket 14 is evenly distributed around the guide tube 11, such as Figure 2 As shown. The water cooling jacket 14 is made of high temperature resistant stainless steel (such as SS310), and the inner wall is roughened by sandblasting as a whole, or partially roughened and the rest is polished mirror structure as required, which can more effectively adjust the axial temperature distribution and reduce the radial temperature gradient. In this way, the temperature of the crystal in the radial direction can be more uniform, and the quality and performance of the crystal can be improved.

[0021] Furthermore, a specific embodiment of a single crystal furnace is provided, including the above-mentioned crucible, wherein a guide tube is arranged above the crucible in the region surrounding the crystal rod pulling area, the guide tube is upwardly open, the inner surface of the shell adopts SiC coating as coating material, the upper part is filled with carbon felt composite material, and the bottom is a hollow structure. Preferably, the guide tube is fixed in position during the process of pulling and growing the single crystal, and does not move with the movement of the crucible.

[0022] The optimized crystal growth process has higher stability and repeatability. By precisely controlling parameters such as temperature, growth rate and atmosphere, it can be ensured that each crystal growth process is carried out under similar conditions, thereby improving the consistency and reliability of the product. This is crucial for the large-scale production of high-quality crystals, helping to reduce production costs and improve production efficiency.

[0023] The above device is used to perform the MCZ method to pull a silicon single crystal with a diameter greater than or equal to 300 mm. The specific steps are as follows:

[0024] 1) Chemicals

[0025] Start the heating system of the crystal growth furnace, increase the temperature at a slow and steady rate, adjust the heating power and the temperature rise curve, and when the temperature reaches above the melting point of silicon, the silicon raw material begins to melt gradually to form a uniform liquid silicon melt.

[0026] 2) Open magnetic field

[0027] Apply a transverse magnetic field with a magnetic field strength of 0.2-0.4T;

[0028] 3) Seeding

[0029] The pre-prepared seed crystal is lowered to the surface of the liquid silicon melt at a rate of 0.3-2mm / min. By precisely controlling the descending speed (0.05-0.2mm / min) and temperature of the seed crystal, it is brought into contact with the liquid silicon melt and the seeding process begins.

[0030] 4) Neck reduction

[0031] After the seeding is successful, the crystal growth rate is gradually reduced, so that the diameter of the crystal gradually decreases, forming a slender neck. The purpose of necking is to remove dislocations and other defects in the seed crystal and provide a good start for subsequent crystal growth. By precisely controlling parameters such as temperature, growth rate and pulling speed, the necking process is ensured to be stable and uniform.

[0032] 5) Release your shoulders

[0033] After the necking is completed, the crystal growth rate is gradually increased to gradually increase the diameter of the crystal and form a shoulder. The shouldering process should be slow and steady to avoid defects or cracks in the crystal due to excessive growth. By observing the growth of the crystal and temperature changes, the growth rate and temperature gradient are adjusted in time to ensure the smooth progress of the shouldering process.

[0034] 6) Equal diameter

[0035] When the diameter of the crystal reaches the required size, it enters the equal diameter growth stage. In this stage, the crystal growth rate, temperature and pulling speed must be kept stable to ensure that the diameter and quality of the crystal are uniform. Through precise temperature control and gas supply, a stable environment in the crystal growth furnace is maintained. At the same time, the growth of the crystal must be closely observed and the process parameters must be adjusted in time to deal with possible problems.

[0036] Crystal rotation speed: <20rpm; (optimal 8-14rpm)

[0037] Crucible rotation speed: <3rpm (optimal 0.01-1rpm)

[0038] Drawing speed: 0.35-0.65mm / min (the specific drawing speed is determined by the combination of thermal field and other parameters)

[0039] Furnace pressure: 2-7kpa (optimal 2-5kpa)

[0040] Argon gas flow rate: 80-220slm (optimal: 100-160slm)

[0041] 7) Closing

[0042] When the crystal grows to the required length, it enters the finishing stage. The growth rate is gradually reduced to gradually reduce the diameter of the crystal, forming a tapered tail. The purpose of the finishing is to prevent the crystal from breaking due to thermal stress during the cooling process. By controlling the growth rate and temperature, the stability and uniformity of the finishing process are ensured.

[0043] 8) Cooling

[0044] The grown single crystal silicon crystal is slowly cooled in an atmosphere of protective gas. The cooling process should be uniform to avoid stress and defects inside the crystal due to too fast cooling speed. The temperature in the furnace is slowly lowered at a rate of 5°C to 10°C per minute. During the cooling process, protective gas, such as argon, is continuously introduced at a flow rate of 5 to 10 liters per minute. The cooling time is determined according to the crystal size and temperature change, generally between 4 and 8 hours.

[0045] In the above process, by precisely controlling the design of the guide tube and optimizing the crystal growth process, the longitudinal temperature gradient of the ingot is increased to promote the rapid growth of the single crystal, while reducing the radial temperature gradient and improving the radial uniformity of the crystal, thereby increasing the width of the defect-free area of ​​the crystal to meet the high quality requirements of advanced process silicon single crystals and the stability and repeatability of crystal growth. Silicon single crystals used in advanced processes require COP (Crystal Originated Pit) <15nm and L-pits (Large-etching pits) to be 0. The requirements for oxygen content are determined according to the specific application scenario and process technology. The oxygen content that meets the advanced process (such as 7nm and below) needs to be controlled at 1×10 17 atoms / cm 3 to 1×10 18 atoms / cm 3 the following.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A guide tube is placed above the crucible of a single crystal furnace and is arranged around the crystal rod pulling area, characterized in that: The guide tube is open upward, the inner surface of the shell adopts SiC coating as a protective material, the upper part is filled with carbon felt composite material, and the bottom is a hollow structure.

2. The guide tube according to claim 1, characterized in that: A water cooling jacket is embedded in the inner wall of the guide tube.

3. The guide tube according to claim 2, characterized in that: The water cooling jacket is made of high temperature resistant stainless steel.

4. The guide tube according to claim 2, characterized in that: The inner wall of the water cooling jacket is a roughened surface with a roughness ranging from Ra0.1 to Ra4.

5.

5. The guide tube according to claim 2, characterized in that: The inner part of the water cooling jacket is partially roughened and partially mirrored, and the proportion of the roughened surface is less than 75%.

6. The guide tube according to claim 1, characterized in that: A transverse flow guide hole is further arranged at the bottom of the flow guide tube.

7. The guide tube according to claim 6, characterized in that: The guide holes are evenly distributed along the side wall of the bottom, and the total area of ​​the openings accounts for less than 50% of the entire wall surface.

8. A single crystal furnace, characterized in that: It includes a crucible, and a guide tube is arranged above the crucible around the crystal rod pulling area. The guide tube is open upward, the inner surface of the shell adopts SiC coating as protective material, the upper part is filled with carbon felt composite material, and the bottom is a hollow structure.

9. The single crystal furnace according to claim 8, characterized in that: The guide tube remains in a fixed position during the process of pulling and growing the single crystal.

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