What is the working principle of the mechanical structure of the Zolizo pull single crystal furnace

in inert gases.

argon) environment, polysilicon will be used with a graphite resistance heater.

The material is melted, and the soft seed crystal shaft lifting and rotating mechanism is used in a specific temperature area to rotate and lift the original seed crystal at a uniform speed, and the crucible is crucible at the same time.

With the growth of the single crystal, it rotates and increases at a constant speed, and the growth into a dislocation-free monocrystalline silicon rod is realized.

Extension of knowledge points:

Straight-pull single crystal furnace is a kind of equipment that melts polycrystalline materials such as polycrystalline silicon with graphite heaters in an inert gas (mainly nitrogen and helium) environment, and grows single-crystal without dislocation by straight-pull method. The mechanical structure of the Zyopull single crystal furnace is as follows:

The basic principle is that the polycrystalline silicon material is heated and melted until the temperature is appropriate. After the seed crystal immersion, welding, crystal introduction, shouldering, shouldering, turning, waiting, finishing and other steps, the drawing of a single crystal ingot is completed.

There are mainly electrical and mechanical parts; The electrical part is the control system. The mechanical part is mainly a thermal field. Molten silicon is placed in the crucible, and the crystal orientation of the seed crystal is replicated by pulling the seed crystal.

Equipment of the Zolithic Pull Method: furnace body, vacuum system, gas system, thermal field system, electrical control system, transmission control system.

Furnace body: The furnace body is the place where polysilicon melts and monocrystalline silicon grows, and the heating system is in it.

Vacuum system: After the AR gas is introduced into the furnace body, the vacuum pump is used to evacuate the oxygen in the furnace body, and the oxygen in the furnace body is drained repeatedly to avoid the residual oxygen affecting the oxygen content of the monocrystalline silicon rod.

Gas system: The incoming AR gas not only acts as a heat transfer medium, but also takes away the volatile SiO and CO in the furnace body

and other gases. Thermal field systems: Thermal field systems include graphite heaters, graphite crucibles, graphite-carbon felt insulation covers, graphite insulation covers, and stones.

Ink electrode. Electrical Control System:

Temperature control system: The combination of power feedback and temperature feedback is used to control the temperature.

Diameter control system: The diameter size is controlled by the combination of drawing speed control and temperature control.

Transmission control system: The transmission system includes crystal rise, crystal rotation, pot rise, and pot rotation, and generally adopts speed measuring motor and drive electricity.

The machine coaxial method takes out the signal voltage of the speed change, and combines the signal voltage of this speed with one.

The constant voltage is relatively thick and the driving voltage of the drive motor is controlled by the amplification area to achieve stability.

The purpose of the fixed speed.

Rationale:The polycrystalline silicon material is heated and melted until the temperature is appropriate. After the steps of seed crystal immersion, welding, crystal introduction, shoulder release, shoulder turning, warp waiting, and finishing, a single crystal ingot is drawn.

Metal single crystal, since all vacuum systems will have air leakage, so if the air has a large impact on the mass of the body, it is necessary to use atmosphere protection. When I grow single crystals, I use high-purity AR, which is about a dozen atmospheres. The growth atmosphere is mainly determined by the specific material you grow and the vacuum degree that your equipment can maintain, if your furnace pressure is not very good, and the design can also withstand a certain amount of positive pressure, it is recommended to use positive pressure growth.

The dismantling process in the production process of Zolithic monocrystalline silicon is carried out after the furnace is shut down for about 6 hours after the finishing is completed, and the crystals are normally removed, the volatiles in the furnace are removed, and the furnace is scrubbed with alcohol. Check whether the thermal field (graphite tray bowl, heater, electrode, etc.) is normal, and clean and change the oil of the mechanical vacuum pump according to the production heat. Then enter the production process of the next furnace:

Vacuum --- blanking --- --- drawing --- stopping --- dismantling of the furnace.

The mechanical department of the Zzozo-pull silicon single crystal furnace is mainly composed of the base and column, the exhaustion transmission parts, the main furnace room, the auxiliary furnace room, the rotating and lifting parts containing the seed crystal, the hydraulic lifting parts of the main and auxiliary furnace chambers, and the vacuum and inflation system. Destroy.

The Czochralski (CZ method) is to put the raw material polysilicon crystal into a quartz crucible, heat and melt it in a single crystal furnace, and then immerse a rod-shaped crystal (called seed crystal) with a diameter of only 10mm into the melt. At the right temperature, the silicon atoms in the melt will form regular crystals at the solid-liquid interface along the arrangement structure of the silicon atoms of the crystal seed, becoming a single crystal. By rotating the seed slightly upward, the silicon atoms in the melt will continue to crystallize on the single crystal formed in front of it, and continue its regular atomic arrangement structure.

If the whole crystallization environment is stable, crystallization can be formed over and over again, and finally a cylindrical single crystal crystal with neatly arranged atoms can be formed, that is, silicon single crystal ingots. When the crystallization accelerates, the crystal diameter will become coarse, and increasing the ramp-up rate can make the diameter thinner, and increasing the temperature can inhibit the crystallization speed. Conversely, if the crystallization slows down and the diameter becomes thinner, it can be controlled by reducing the drawing speed and cooling.

At the beginning of crystal pulling, a thin neck of a certain length and a diameter of 3 5 mm is first drawn out to eliminate the crystallization dislocation, and this process is called crystal introduction. The diameter of the single crystal is then enlarged to the process requirements, and the equal diameter stage is entered until most of the silicon melt is crystallized into a single ingot, leaving only a small amount of leftover. Controlling the diameter and ensuring the equal diameter growth of the crystal is an important part of the manufacturing of single crystals.

The melting point of silicon is about 1450, and the crystal pulling process is always carried out in an environment of high temperature and negative pressure. The diameter inspection must be carried out non-contact outside the crystal drawing furnace through the viewing window. During crystal pulling, the junction between the solid crystal and the liquid melt will form a bright ring with high brightness, called the aperture.

It is actually the reflection of the bright light of the crescent moon at the interface of the solid and liquid on the crucible wall. When the crystal becomes thicker, the diameter of the aperture becomes larger, and vice versa. By detecting the change in aperture diameter, the change in the diameter of the single crystal can be reflected.

Automatic diameter detection has been developed based on this principle.

1. Zone melting method (FZ).

In order to prevent contamination caused by the chemical reaction between the melt and the crucible, the non-increasing pot crystal growth process is called zone melting. The basic structure is shown in Figure 1-1. A polycrystalline rod is installed vertically, and one end of the rod is melted by heating with water-cooled radio frequency induction.

Relying on the surface tension of the melt and the levitating force generated by the electric field, the melt adheres to the crystal rod. The end of a directional seed crystal is invaded into the melt, and the relative motion of the heater and the crystal melt is used to continuously melt the polycrystalline rod, while the other side gradually forms crystals. Although the crystals grown in this method will not be contaminated by the crucible, this method is only suitable for the growth of crystals with a large melt surface tension coefficient.

2. Straight pull method (CZ).

The Zzochralski method is also known as the "Czochralski method", abbreviated as the CZ method. It is the main method for growing monocrystalline silicon. In this method, the raw material (polysilicon) is packed in a crucible in a single crystal furnace of the Zzopull method (CZ) and heated to a molten state, and the seed crystals are introduced into the molten silicon, and the seed crystals are sandwiched at the lower end of the lifting rod to control the temperature appropriately.

When the seed crystal and the molten silicon reach equilibrium, the melt will be adsorbed underneath the seed crystal with the support of surface tension. At this time, the seed crystals are lifted while rotating, and these adsorbed melts will also move upward with the seed crystals. During the upward movement, the melt temperature drops, which will cause the melt to condense into crystals and grow into single crystal rods with the direction of the seed crystals.