The physical purification method of Pure Silicon Metal and equipment thereof
Technical field
The present invention relates to the physical purification method and the equipment thereof in the purification techniques field, particularly a kind of Pure Silicon Metal of solar-grade polysilicon material.
Background technology
Crystalline silicon is to use solar cell material the most widely at present, and the solar energy level silicon material of main flow all adopts the Siemens Method preparation.For reducing material cost, there is several different methods that low-cost silicon material such as metalluragical silicon are handled at present, make it purity near 6N, meet the purity requirement of silicon solar cell, be respectively:
1. pyrocarbon one silicon and aluminium one Si reduction purification technique;
2. segregation effect of insulated grid oxidation purifying metalluragical silicon when utilizing crystallization;
3. pickling purification technique;
4. slagging scorification purification technique;
5. air-blowing and evaporation purification technique;
6. glow discharge produces the cold plasma purification technique.
The pickling purification technique can carry out at normal temperatures, but its processing efficiency and effect are limited, generally handles the auxiliary of means as other;
Glow discharge produces the cold plasma purification technique and also can handle at a lower temperature, (is lower than 10 but its ion density is low
10), ion energy little (less than 1eV), treatment effect is limited, in addition, its hypobaric working conditions has limited its material and has transported;
Other several methods all relate to the thawing of silicon material, need the pyroprocessing more than 1400 ℃.
Summary of the invention
Technical problem to be solved by this invention is: a kind of physical purification method and equipment thereof of Pure Silicon Metal are provided, reduce the purification difficulty, improve purification efficiency.
The present invention solves the scheme that its technical problem adopts: a kind of physical purification method of Pure Silicon Metal; The method that in fluidized-bed, adopts dielectric barrier discharge is as isoionic producing method; With fluidized-bed silica flour is carried out preheating and transmission; Use silicon particle size; Carrier gas preheating temperature and flow rate of carrier gas are controlled the particle average handling time; Use the carrier gas preheating temperature; The plasma excitation power supply power of the atmosphere kind of carrier gas and dielectric barrier discharge is controlled purification effect; In flow process, the silica flour that constrains in the plasma body is realized purifying, the silicon material after purifying the most at last is from the terminal output of fluidized-bed.
Concrete steps are following:
1) fluidized-bed integral body is evacuated to 1mTorr;
2) feed the carrier gas that is preheated to design temperature from grid distributor, and control flow velocity and adjusting pressure;
3) treat steady air current after, open the plasma excitation power supply and produce plasma, regulate the pressure of feed system and rewinding and gas-recycling plant, it is mobile that the flow field is produced, after flow velocity reached set(ting)value, feed system began continuous charging;
4) through regulating silicon particle size, carrier gas preheating temperature and flow rate of carrier gas, control particle mean residence time;
5) silicon and the gas that recycling finishes from rewinding and gas-recycling plant.
Carrier gas is main with rare gas element mainly, according to different impurities, selects to feed H
2, HCl, O
2In these three kinds of function gases a kind of, two kinds or all.
The median size of silicon particle size≤50 μ m.
The plasma excitation power supply is 5kV to a 10kV sine ac power supply, and the frequency of sine ac power supply is 200Hz~20kHz.
The plasma excitation power supply is a nanosecond pulse power supply.
The carrier gas preheating temperature is 800 ℃-1000 ℃.
According to the situation of silicon material itself, can implement multistage purification or repeat purification.
A kind of equipment for purifying; Comprise fluidized-bed; Feed system; Plasma excitation power supply and rewinding and gas-recycling plant; Fluidized-bed comprises grid distributor and bed body; The bed body is the closed environment of vacuum-pumping; Bed body internal surface applies the dielectric of low-k; The parallel pole of dislocation parallel to each other is set in the bed body; Make fluid pass plasma area with the S type; Its surface-coated high-dielectric coefficient coating; Insulate between parallel pole and bed body; On parallel pole, add the plasma excitation power supply, between parallel pole, form dielectric barrier discharge, form plasma; The front end of fluidized-bed connects feed system; End and rewinding and gas-recycling plant; Carrier gas gets into the bed body through grid distributor, and silica flour gets into fluidized-bed through feed system and carries out purifying, and the silicon material after the purification is from terminal rewinding and the gas-recycling plant of getting into of fluidized-bed.
Particularly, parallel pole has three, horizontal each other parallel misalignment, and fluidized material can flow through the parts transversely S type of dislocation.
The invention has the beneficial effects as follows: can be under normal pressure and nearly non-pressurized condition the purified silicon material, the ion density that is used to purify is high, energy is big, purification efficiency is high, cost is low.Under normal pressure and nearly non-pressurized condition, dielectric barrier discharge can generate energy density reach 10 under multiple atmosphere
14Cm
-3Ion density, than high 4 to 5 one magnitude of common glow discharge plasma.In addition, its electronics average energy can reach more than the 10eV.In addition, normal pressure and nearly non-pressurized air pressure make the gas phase particle transport and become feasible.
Description of drawings
Below in conjunction with accompanying drawing and embodiment the present invention is further specified;
Fig. 1 is the front view of fluidized-bed of the present invention;
Fig. 2 is the vertical view of fluidized-bed of the present invention;
Among the figure, 1. feed system; 2. rewinding and gas-recycling plant; 3. grid distributor; 4. parallel pole; The bed body; 6. plasma excitation power supply.
Embodiment
A kind of physical purification method of Pure Silicon Metal; The method that in fluidized-bed, adopts dielectric barrier discharge is as isoionic producing method; (10000Pa is to normal pressure) carries out preheating and transmission with fluidized-bed to silica flour under the nearly normal pressure of atmosphere; Use silicon particle size; Carrier gas preheating temperature and flow rate of carrier gas are controlled the particle average handling time; Use the carrier gas preheating temperature; The power of the atmosphere kind of carrier gas and the plasma excitation power supply 6 of dielectric barrier discharge is controlled purification effect; In flow process, the silica flour that constrains in the plasma body is realized purifying, the silicon material after purifying the most at last is from the terminal output of fluidized-bed.
Concrete steps are following:
1) fluidized-bed integral body is evacuated to 1mTorr;
2) feed the carrier gas that is preheated to design temperature from grid distributor 3, and control flow velocity and adjusting pressure;
3) treat steady air current after, open plasma excitation power supply 6 and produce plasmas, regulate the pressure of feed system 1 and rewinding and gas-recycling plant 2, the flow field is produced flows, after flow velocity reached set(ting)value, feed system 1 began continuous charging;
4) through regulating silicon particle size, carrier gas preheating temperature and flow rate of carrier gas, control particle mean residence time;
5) silicon and the gas that recycling finishes from rewinding and gas-recycling plant 2.
Carrier gas is main with rare gas element mainly, according to different impurities, selects to feed H
2, HCl, O
2In these three kinds of function gases a kind of, two kinds or all, wherein, H
2, the H ion that produces of HCl can remove P, B impurity in the silicon material.Cl, O ion can be removed the transition metal in the silicon material.
The median size of silicon particle size≤50 μ m.
Plasma excitation power supply 6 is 5kV to a 10kV sine ac power supply, and the frequency of sine ac power supply is 200Hz~20kHz.
For improving the yield of plasma high energy part, can replace sine-wave power with nanosecond pulse power supply.
The carrier gas preheating temperature is 800 ℃-1000 ℃.
According to the situation of silicon material itself, can implement multistage purification or repeat purification.
The equipment of dielectric barrier discharge is formed with common glow discharge device similar, and difference is block media and the excitation power supply between the parallel capacitance plate.This kind parallel capacitance plate discharge electrode can realize in a variety of forms that the present invention adopts the electric capacity flat board of dislocation as electrode, makes fluid pass plasma area with the S type.
Illustrated in figures 1 and 2, this equipment for purifying comprises fluidized-bed, feed system 1, plasma excitation power supply 6 and rewinding and gas-recycling plant 2, and fluidized-bed comprises grid distributor 3 and bed body 5, selects the grid distributor 3 of different percentage of open area according to particle grain size.The preheating carrier gas gets into bed body 5 through grid distributor 3, has dragged particle at last and has formed fluid.
Bed body 5 is the closed environment of vacuum-pumping, and feed system 1 and rewinding and gas-recycling plant 2 also all are in same closed system kind.Bed body 5 internal surfaces apply the dielectric of low-k; The parallel pole 4 of dislocation parallel to each other is set in bed body 5; Make fluid pass plasma area with the S type; Its surface-coated high-dielectric coefficient coating; Parallel pole 4 and 5 insulation of bed body add plasma excitation power supply 6 on parallel pole 4, form dielectric barrier discharge 4 of parallel poles; Form plasma, the spatial dimension of plasma distribution scope between parallel pole 4.As shown in Figure 2, parallel pole 4 has three, horizontal parallel misalignment each other, and middle one is connected with plasma excitation power supply 6, parallel pole 4 ground connection of both sides, fluidized material can be mobile through the parts transversely S type that misplaces.
The front end of fluidized-bed connects feed system 1, terminal and rewinding and gas-recycling plant 2; Carrier gas gets into bed body 5 through grid distributor 3; Silica flour gets into fluidized-bed through feed system 1 and carries out purifying, and the silicon material after the purification is from terminal rewinding and the gas-recycling plant 2 of getting into of fluidized-bed.
Embodiment 1:
Elder generation is evacuated to 1mTorr with the base vacuum of system in the present embodiment, feeds the carrier gas (Ar: H that comprises function gas then
2: HCl=98: 1: 1), the gas preheating temperature is 900 ℃.Regulate pressure to normal pressure, then system is applied the sine ac power supply of voltage 4kV, frequency 10kHz.Behind the discharge stability, load pending silicon material with carrier gas to system through feed system 1.Among the embodiment, silicon material powder is heated to 900 ℃ with the carrier gas meeting, is beneficial to the carrying out of solid phase diffusion in the particle.Particle median size 50 μ m.The mean residence time of particle in device is 1h, according to the situation of silicon material itself, can implement multistage purification or repeat purification.
Embodiment 2:
Present embodiment is under relatively low vacuum tightness (10
4Pa) implement experimental program, need, otherwise average handling time can corresponding shortening the refinement of further silicon material particle diameter (1 μ m).Other parameters and embodiment 1 are similar.