Single crystal furnaces belong to high-temperature, vacuum, water-cooled, and inert atmosphere equipment, with core risks including silicon leakage, high-temperature burns, vacuum explosions, water cooling failure, abnormal argon gas, thermal field damage, and crystal rod quality defects. They are divided into five modules: pre startup, operation, emergency response, furnace disassembly and maintenance, and safety control.
1、 Key points for inspection before starting the furnace
1. Cooling water cooling system
Water must be supplied first, followed by heating, to confirm that the water pressure, flow rate, and inlet and outlet water temperature differences are within the process range; Check that the filter is unobstructed and there is no leakage in the water circuit; Confirm that the water pressure and flow alarm interlock functions are effective.
It is recommended to use deionized water for cooling water to prevent scaling and blockage of the water cooling jacket; Check the reliability of emergency water supply and respond to water outage accidents.
2. Vacuum and gas path (argon gas)
Argon purity ≥ 99.999%, check the pressure reducing valve, pipeline, and flow meter; The inlet pressure is stable and there is no leakage in the pipeline.
Cold furnace leak detection, testing the leakage rate to meet the standard; The O-ring and flange seals are intact; The oil level of the vacuum pump is normal, and there is no abnormal noise from the pump; The observation window is clean, making it convenient to observe the state of molten silicon and liquid level.
3. Thermal field and loading
Inspection of graphite heater, insulation felt, graphite crucible, and guide tube: no cracks, erosion, chipping, or contamination; Graphite parts are strictly prohibited from being bumped, and contaminated parts are prohibited from being reused.
Carefully inspect the quartz crucible and ensure that there are no cracks or scratches; Handle the silicon material with care and prohibit large pieces of material from directly hitting the crucible; Reserve a safe height on the material surface to prevent material collapse and silicon jumping; Silicon material should not contain metal impurities.
Seed crystal and tungsten wire rope inspection: The steel wire rope has no burrs, dead bends, or broken wires, and must be replaced when it reaches its service life; The seed crystal is firmly clamped and aligned for calibration; The crucible axis and seed crystal axis rotate steadily without shaking or jamming.
4. Electrical and Control Systems
Confirm that the UPS backup power supply is functioning properly; Calibration of thermocouples, infrared temperature sensors, pressure sensors, and liquid level sensors; All alarm interlocks shall not be artificially blocked, and it is prohibited to modify process parameters arbitrarily.
Single crystal furnace with magnetic field: It is strictly prohibited for ferromagnetic tools, magnetic cards, and mobile phones to approach areas with strong magnetic fields to prevent equipment damage and personal injury.
2、 Key points to pay attention to during the growth and operation process
1. Melting stage (high incidence of silicon jump)
Control the heating rate and prohibit power surges; Pay attention to the phenomenon of silicon jumping (molten silicon splashing); Silicon jump can damage the thermal field and seriously cause silicon leakage accidents.
Maintain normal flow of argon gas, promptly handle bridge construction and edge hanging, and prohibit rough operations.
2. Introduction of crystals - Shoulder placement - Equal diameter - Final crystal pulling stage
Closely monitor the distance between the liquid port, crystal oscillation, crucible rotation, crystal rotation, furnace pressure, argon flow rate, temperature and power. If there is any drift in the parameters, adjust them promptly and do not make significant changes.
Maintain a stable argon gas flow inside the furnace and promptly remove SiO volatiles; Fluctuations in furnace pressure can directly cause crystal defects.
Do not strike or shake the furnace body to avoid vibration causing seed breakage and crystal dislocation; Do not lean on the stove or electrical control cabinet.
The observation window should be kept transparent. If white oxidation is found, priority should be given to investigating whether there is water leakage or air leakage. Water leakage can cause single crystal oxidation to be scrapped and seriously lead to accidents.
3. Mechanical moving parts
The crucible lifting and seed crystal pulling operation runs steadily without any abnormal noise or shaking; Regular lubrication of the screw rod; Regularly clean the shaft seal to prevent dust accumulation from causing vacuum leakage and shaking.
4. Operation inspection
Regular inspection: water cooling temperature and pressure, argon pressure, pump unit status, electrode ignition, and abnormal heating of the furnace body; Prioritize analyzing the root cause when an alarm occurs, and do not allow simple resetting to continue production.
3、 Typical Emergency Response for Sudden Abnormalities
It is strictly prohibited to disassembly the furnace directly under high temperature conditions. The furnace chamber must be fully cooled before opening the cover.
1. Sudden water outage
Immediately cut off the heating power supply; Activate emergency water supply; It is strictly prohibited to directly supply cold water to the high-temperature furnace body to prevent water vapor explosion; Unable to restore water supply, shut down the furnace according to the process, wait for the furnace to cool down sufficiently before disassembly.
2. Sudden power outage
Short term power outage: protect the supply of argon gas and lift the seed crystal off the liquid surface; Long term power outage: lift the seed crystal away from the molten silicon, control the position of the crucible, and prevent the silicon liquid from solidifying and bursting graphite components; Power and heating should be cut off simultaneously, and the argon gas ball valve should be closed in a timely manner to avoid the risk of secondary chamber flushing.
3. Suspected risk of silicon leakage (severe shaking of liquid level, abnormal jumping of current, alarm)
Immediately stop heating and quickly lift the seed crystal off the liquid surface; Crucible lifting protection guide tube; Shutdown the furnace for sufficient cooling, then disassembly the furnace for inspection. It is forbidden to open the lid at high temperatures for inspection.
4. Rapid decrease in vacuum degree
Check for leaks; If accompanied by abnormal power, there is a high probability of water leakage, immediately reduce power and shut down the furnace.
5. Seed crystal fracture
Observe for silicon leakage at the first time and determine whether to perform remelting treatment based on the remaining molten silicon. Do not blindly continue pulling crystals.
4、 Attention to furnace disassembly, cooling, and thermal field maintenance
1. After the crystal pulling is completed, strictly follow the cooling procedure. If the cooling is not in place, it is strictly prohibited to open the furnace drum and auxiliary chamber door. High temperature may cause burns to personnel and damage the thermal field due to air rushing in.
2. Use specialized insulation tools to remove high-temperature graphite components and place them on a dedicated cart. Do not place them directly on the ground; The hot screen is placed upside down to prevent impurities from contaminating the graphite components.
3. Clean the furnace chamber of volatile substances and silicon powder dust; Classification inspection of graphite parts, direct scrapping for cracking, ablation, and silicon infiltration; The sealing ring is regularly replaced as a set due to aging.
4. Regularly change the oil of the vacuum pump and maintain the pump assembly; The filtering device promptly cleans the silicon dust to prevent the accumulation of dust and the risk of fire.
5. During the disassembly process, do not place your hands between the furnace tube and the joint gap of the auxiliary chamber to prevent squeezing injuries.