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Monocrystalline Silicon Preparation Principle
- Dec 04, 2017 -

Monocrystalline silicon preparation principle

1, Czochralski method
Czochralski method is currently used in a large area more monocrystalline silicon preparation technology, also known as Czochralski method (Czoalsik: CZ method) is a crystal growth method established by Czekski in 1917, now become The main method of preparing single crystal silicon. The use of rotating seed crystal from the melt in the crucible to prepare a single crystal method, also known as Czochralski method. At present, most domestic manufacturers of single-crystal silicon solar cells using this technology. High-purity polycrystalline silicon into the high-purity quartz crucible, melting in a silicon single crystal furnace; and then use a seed crystal fixed on the seed shaft into the melt surface, until the seed and melt melt, and slowly upward Pull the seed, the crystal will grow in the bottom of the seed. The basic principle is shown in the figure. The polycrystalline silicon material is placed in a crucible and melted by heating. After the temperature is suitable, a single-crystal silicon ingot is drawn through steps of immersing, welding, seeding, placing shoulders, shoulders, equal diameters, finishing and the like . Furnace heat transfer, mass transfer, fluid mechanics, chemical reactions and other processes have a direct impact on the growth and growth of single crystal into a single crystal quality, crystal pulling process can directly control the parameters of the temperature field, the seed crystal To the crucible and the growth of single crystal rotation and lifting rate, the type of furnace gas protection, flow, flow rate, pressure and so on. CZ method is to melt the silicon material, starting from a little crystallization, usually such purification can only be carried out once.

2, the advantages and disadvantages of Czochralski
The device and the process are relatively simple and easy to realize automatic control; the production efficiency is high and the preparation of the large-diameter single crystal is easy; and the impurity concentration in the single crystal can be easily controlled to prepare the low-resistance single crystal.
Easily contaminated by the crucible, silicon purity decreased, drawn silicon single crystal resistivity greater than 50 ohm ˙ cm, the quality is difficult to control.

3, zone melting method
Floating zone melting method appears later than the Czochralski method, proposed by W˙G ˙ Pfann in 1952, P˙H˙keck et al. 1953 for the purification of semiconductor silicon. Floating zone melting method is to clamp the polycrystalline silicon rods with the upper end, the lower end of the seed, high-frequency current through the coil and polycrystalline silicon rods coupled to produce eddy current, the polycrystalline rods partially melted, pick the seeds, bottom-up So that the silicon rod melting and single crystal growth, using this method is called single crystal silicon melting zone single crystal. The zone melting method has horizontal zone melting and suspension zone melting. The former is mainly used for germanium purification and growth of germanium single crystal. The growth of the silicon single crystal mainly adopts the floating zone melting method, and the crucible is not used in the growth process. The melting zone is suspended in the polycrystalline silicon rod And below the growth of the single crystal between the zone melting method does not use the crucible, less pollution, the high purity of the silicon single crystal grown by the zone melting purification, oxygen content and carbon content is low. High-resistance silicon single crystal growth in this method. At present, the area of single-crystal melting is relatively narrow, not as mature as Czochralski process, and some structural defects in single crystal are not solved.