Quartz crucible is actually a kind of container, which is made of high-purity quartz sand through a mold and made of high-temperature arc method. It has the characteristics of high temperature resistance, long service time and high purity.
1. Understanding the Quartz Crucible
Quartz crucible is actually a kind of container, which is made of high-purity quartz sand through a mold and made of high-temperature arc method. It has the characteristics of high temperature resistance, long service time and high purity.
Quartz crucibles can be used below 1450°C and are divided into two types: transparent and opaque. The earliest quartz crucibles were all transparent. This transparent structure easily led to uneven heat transfer conditions and increased the difficulty of ingot growth, so this kind of crucible was eliminated.
At present, translucent quartz crucible is an indispensable basic material for pulling large-diameter single crystal silicon and developing large-scale integrated circuits. Today, the developed countries of the world’s semiconductor industry have replaced the small transparent quartz crucible with this crucible. The translucent quartz crucible has the advantages of high purity, strong temperature resistance, large size and high precision, good heat preservation, energy saving and stable quality.
2. The production process of quartz crucible
According to the different formulation process, the production and molding of quartz crucible generally adopts two methods: grouting or coagulation. The two production processes are largely the same. However, due to the differences in production methods, the selection of supporting equipment for the two processes is still different.
(1) Production process of grouting method
The grouting method has a long history in the production process of ceramics, it is relatively traditional, and it is relatively easy to master. It is the most commonly used production molding method at present. The grouting method is widely used in the production of quartz crucibles.
The general production process of the grouting method: grouting – demoulding – turning – curing – initial inspection – repairing – drying – calcining – trimming – final inspection – packaging
The main supporting production equipment for grouting production: stainless steel mold – cantilever suction cup hoisting machine – demoulding turning machine – demoulding platform – curing furnace – initial inspection line – cantilever suction cup hoisting machine – less air dryer ——Cantilever suction cup hoisting machine——calcining furnace——cantilever suction cup hoisting machine——edging machine——cantilever suction cup hoisting machine——final inspection into billet table——final inspection billet turning machine——light inspection rotary table——lighting Final inspection table – final inspection blank line – cantilever suction cup hoisting machine – packaging
Since the demoulding time of injection molding is generally 8 hours, the molding efficiency is relatively low, and the output should not be too large.
(2) Production process of injection coagulation method
Injection molding has just emerged in the production of quartz crucibles, and the process is relatively difficult and difficult to master. It is relatively rarely used in the production process of quartz crucibles. However, compared with the grouting method, this method can greatly shorten the demoulding time and improve the demoulding efficiency, and has certain advantages in large-scale production.
The injection coagulation method is not easy to master in the production of quartz crucibles, and currently there are a few domestic companies using this method. Due to its certain advantages in mass production, it is the development direction of future production processes.
General production process of injection coagulation method: grouting – demoulding – turning – initial inspection – repairing – drying – calcining – trimming – final inspection – packaging
The main supporting production equipment for injection coagulation production: stainless steel mold – cantilever suction cup hoisting machine – demoulding and turning machine – demoulding platform – initial inspection line – cantilever suction cup hoisting machine – less air dryer – cantilever suction cup Hoisting machine – calcining furnace – cantilever suction cup hoisting machine – trimming machine – cantilever suction cup hoisting machine – final inspection into the billet table – final inspection billet turning machine – light inspection rotary table – light final inspection table – – Final inspection of the blank line – Cantilever suction cup hoisting machine – Packaging
(3) Process comparison
Because the grouting method relies on the water absorption of the plaster mold to dry, the demoulding time is long and the production efficiency is low. The injection molding method uses a steel mold, but it is equipped with additives in the product ingredients. The green body can be rapidly solidified and formed during the production process, improving the strength, and it is easy to quickly demould. Cured by curing oven. However, during the calcination process of such products, these organic additives will decompose and volatilize, thereby reducing the density and strength of the product. At present, the domestic methods to improve the density and strength of finished products have basically been solved. From the above comparison and analysis, it is known that the two production processes use basically the same supporting equipment, only the coagulation method does not require a curing furnace to cure the green body, and the process flow and other supporting equipment are basically the same.
3. Use and maintenance of quartz crucible
The main chemical composition of quartz crucible is silicon dioxide, which does not interact with other acids except hydrofluoric acid, and is easy to interact with caustic alkali and alkali metal carbonate;
The quartz crucible has good thermal stability and can be heated directly on the flame;
Quartz crucibles are easily broken, so be careful when using them;
Quartz crucible can use potassium hydrogen sulfate (sodium), sodium thiosulfate (drying at 212 ℃) as flux, and the melting temperature should not exceed 800 ℃.
Fourth, the demand analysis of quartz crucible
In terms of service life, the ideal life of the quartz crucible is 400 hours+, and the worst case is about 300 hours. (Note: The service life of the quartz crucible corresponding to the N-type silicon wafer is 50-100 hours lower than that of the P-type silicon wafer, that is, the life of the quartz crucible for the P-type silicon wafer is about 400 hours, and the life of the quartz crucible for the N-type silicon wafer is 300-350 hours).
Quartz crucible consumption of a single crystal furnace: At present, a single crystal furnace of P-type silicon wafer uses an average of 2 quartz crucibles a month (720 hours) and 24 quartz crucibles a year. Quartz crucible consumption of 1GW silicon wafer: 1GW182 silicon wafer production capacity corresponds to 100 single crystal furnaces, and 1GW silicon wafer shipment corresponds to about 2400 quartz crucibles.
4. Summary
Quartz crucibles are mainly used in semiconductor, photovoltaic and other fields. Due to the high degree of product precision and rapid technological development in the photovoltaic industry, the requirements for the purity and precision of quartz crucibles are becoming increasingly strict. The quartz product industry in my country started late, and only a few large-scale enterprises have reached the advanced level in terms of quartz crucible technology. In terms of technology change, with the continuous iteration of downstream industry technology, quartz crucible manufacturers need to keep pace with the times, develop and produce products that meet the needs of downstream fields in a timely manner, and meet the requirements of downstream customers to reduce costs and increase efficiency in order to maintain a competitive advantage.