CN101525136A

CN101525136A - Method for purifying silicon

Info

Publication number: CN101525136A
Application number: CN200810007729A
Authority: CN
Inventors: 赵志强
Original assignee: BYD Co Ltd
Current assignee: BYD Co Ltd
Priority date: 2008-03-07
Filing date: 2008-03-07
Publication date: 2009-09-09
Anticipated expiration: 2028-03-07
Also published as: CN101525136B

Abstract

The invention provides a method for purifying silicon. The method comprises the following steps: melting and atomizing silicon containing impurities under the protection of inert gases; and evaporating the impurities in an atomization state. The method for removing the impurities from silicon is to remove phosphor in the silicon by an atomization method, greatly improves the evaporation area, and improves the evaporation efficiency, thereby having good dephosphorization effect. Solar grade silicon with the phosphor content lower than 1ppm can be prepared by the method.

Description

The method that a kind of silicon is purified

Technical field

The present invention relates to the method that a kind of silicon is purified.

Background technology

Solar energy level silicon is the basic raw material of photovoltaic industry, and its purity is generally 99.99-99.9999%.The starting material of solar energy level silicon preparation are levels of metal silicon, and the purity of levels of metal silicon is generally 98-99.5%.Silane thermal decomposition process (or claim Siemens Method) is generally adopted in purification from levels of metal silicon to solar energy level silicon, and its shortcoming is that energy consumption height, seriously polluted, facility investment and production cost are higher.Because high equipment investment cost and the manufacturing cost of prior art solar energy level silicon causes the solar module cost high, seriously restricted the development of photovoltaic industry.

In recent years, metallurgy method prepares solar energy level silicon because cost is lower, has been subjected to paying attention to widely.Directional solidification method is the levels of metal silicon impurities removing method of using always.Because the segregation coefficient of most of metals less than 0.01, therefore can be removed most metallic impurity with directional solidification method.But directional solidification method is difficult to remove bigger P, B, the elements such as C, O of segregation coefficient, wherein remove the difficulty maximum with P and two kinds of elements of B again, and they is bigger to the Solar cell performance influence.In P and two kinds of elements of B, B can remove by the method that adds sour gas, and the removal of P is difficult relatively more.

When temperature was 1600-2000K, the vapour pressure of P was about 10 of silicon ⁸-10 ¹⁰Doubly.That is to say that in this temperature range, the vapour pressure of P is higher than silicon far away.It is present that to remove the P method all be to utilize this principle to realize the purpose of divided silicon and P basically.

The more sophisticated at present P method of removing is an electron-beam process, and it is to shine silicon face with electron beam, makes it fusion and reaches the purpose that evaporation removes P.This method facility investment is big, energy consumption is high, production capacity is low, is difficult to produce in batches.

US6090361 has proposed a kind of levels of metal silicon to be purified to the method for solar energy level silicon, is to utilize the higher principle of the vapour pressure of P under the high temperature, will after the fusing of levels of metal silicon P is evaporated under vacuum condition from melt, thereby reduce the content of P.The shortcoming of this method is that the evaporation area of melt is little, and vaporization efficiency is low, and it is bad to remove the P effect.

Summary of the invention

The objective of the invention is to overcome in the prior art and from silicon, to remove the shortcoming that the method vaporization efficiency is low, phosphor-removing effect is bad that phosphorus prepares solar energy level silicon, a kind of vaporization efficiency height, silicon method of purification that phosphor-removing effect is good are provided.

The invention provides the method that a kind of silicon is purified, wherein, this method is included under the protection of inert gas, with impure silicon fusion, atomizing, under atomizing state with impurity evaporation.

The present invention removes impurity from silicon method is to utilize atomization to evaporate the phosphorus of removing in the silicon, has greatly increased evaporation area, has improved vaporization efficiency, thereby has had good phosphor-removing effect.Can make the solar energy level silicon that phosphorus content is lower than 1ppm with the inventive method.

Description of drawings

Fig. 1 is the schematic representation of apparatus that is used for preparation method of the present invention.

Reference numeral

1: reinforced stove 2: opening for feed

3: treat purified silicon 4: hot-plate

5: gas bomb 6: the atomized feed pipe

7: feed back pipe 8: the atomizing stove

9: atomizing nozzle 11: range of atomization

12: purified silicon 13: the feed back valve

14: vacuum pump 15: the charging valve

16: the discharging valve

Embodiment

The method that silicon provided by the invention is purified is included under the protection of inert gas, with impure silicon fusion, atomizing, under atomizing state with impurity evaporation.

Wherein, described fused condition can be the melting condition of routine, as long as can make silicon be transformed into molten state, for example, described fused temperature can be 1414-1700 ℃, is preferably 1500-1700 ℃.

Described atomization process is with impure silicon atomizing with atomizing nozzle.The structure of described atomizing nozzle is identical with the nozzle that routine is used for liquid, its material can be any high temperature material, is preferably in the pottery that graphite, fusing point that molybdenum alloy, fusing point that tungstenalloy, metal molybdenum, fusing point that tungsten, fusing point be not less than 2000 ℃ be not less than 2000 ℃ be not less than 2000 ℃ be not less than 2000 ℃ one or more.The present invention is not particularly limited the pressure difference of atomizing nozzle inlet end and exit end, as long as fused silicon is atomized by atomizing nozzle.

Described tungstenalloy is preferably one or more among W-Ti, W-Ni, W-Mo, the W-Cu, described molybdenum alloy is preferably one or more among Mo-Re, Mo-W, Mo-Ti, the Mo-Nb, the purity of described graphite is preferably 99-99.9%, and described pottery is preferably high-melting-point boride, zirconium thing base ceramic material such as ZrB ₂Or ZrO ₂Base ceramic material.

The condition of described evaporation comprises that temperature can be 1420-2350 ℃, is preferably 1500-1700 ℃; Pressure can be 0.001-1000Pa, is preferably 0.01-10Pa; Time can be 3-30 minute, is preferably 5-15 minute.

Different according to the content of impurity in the silicon, phosphorus content that needs reach and evaporation time, described atomizing and evaporative process can be carried out repeatedly.Under the preferable case, described atomizing and evaporation are carried out 3-10 time.

Described rare gas element is one or more in the neutral element gas.

Will pass through dephosphorization from the Pure Silicon Metal to the solar power silicon, remove boron, de-carbon, remove several steps such as metal, each step does not have the fixed order.Silicon method of purification of the present invention is specially adapted to remove the phosphorus impurities in the silicon.

Fig. 1 is the schematic representation of apparatus that is used for preparation method of the present invention, describes preparation method's provided by the invention concrete steps in detail below in conjunction with Fig. 1:

1, under the room temperature, in reinforced stove 1, adds a certain amount of purified silicon for the treatment of by opening for feed 2;

2, with opening for feed sealing, open gas bomb 5 (rare gas element is housed), in reinforced stove 1, feed rare gas element make pressure in the stove 1 that feeds in raw material greater than a normal atmosphere to 1Mpa; Open vacuum pump 14, closed gas bomb 5 after bleeding 1-2 minute, continuing to be pumped to the stove internal gas pressure is 0.01-10Pa; With the air in the emptying stove.

3, close charging valve 15, open heating power supply, hot-plate 4 is started working, treat that purified silicon 3 all after the fusing, continues to be heated to 1500-1700 ℃;

4, close feed back valve 13, open charging valve 15, open gas bomb 5, make the air pressure in the reinforced stove 1 remain on 0.1-10MPa, treat that purified silicon 3 will enter atomizing stove 8 along atomized feed pipe 6 by atomizing nozzle 9 under pressure,, descend slowly and lightly through range of atomization 11 with vaporific in atomizing stove 8 bottoms;

5, when in the reinforced stove 1 treat that purified silicon all enters the atomizing stove after, close gas bomb 5 immediately, bleeding and making furnace pressure is 0.01-10Pa, keeps 5-15 minute, the silicon droplet in the stove that atomizes drop to the liquid level of purified silicon 12;

6, open feed back valve 13, make the molten state silicon in the atomizing stove 8 under action of gravity, be back to reinforced stove 1, and the maintenance temperature is 1500-1700 ℃ by feed back pipe 7;

7, above-mentioned steps 4-6 is repeated 3-10 time, under protection of inert gas, make purified silicon 12 flow out the silicon product after promptly obtaining purifying by discharging valve 16.Phosphorus impurities is wherein discharged from system through vacuum pump with gas form, can be cooled to room temperature under protection of inert gas by discharging valve 16 effusive purified silicons 12.

Below, will the present invention will be described in more detail by embodiment.

Embodiment 1

Present embodiment is used to illustrate the preparation method of solar energy level silicon of the present invention.

Preparation facilities as shown in Figure 1.

1, under the room temperature, adding is waited to purify for 300 kilograms and is contained the silicon of phosphorus impurities in reinforced stove 1, and wherein the content of phosphorus impurities is 58ppm;

2, gas bomb 5 (argon gas is housed) is opened in will feed in raw material stove sealing, feeds the argon gas of 0.5MPa in stove; Open vacuum pump 14, closed argon gas steel cylinder 5 after bleeding 1 minute, continuing to be pumped to the stove internal gas pressure is 0.2Pa;

3, close charging valve 15, open heating power supply, hot-plate 4 is started working, after treating purified silicon 3 fusings, continue to be heated to 1500 ℃;

4, close feed back valve 13, open charging valve 15, open gas bomb 5, make the air pressure in the reinforced stove 1 remain on 0.2MPa, treat that purified silicon 3 enters atomizing stove 8 along atomized feed pipe 6 by atomizing nozzle 9 (being made by tungsten) under pressure,, descend slowly and lightly through range of atomization 11 with vaporific in atomizing stove 8 bottoms;

5, when in the reinforced stove 1 treat that purified silicon all enters atomizing stove 8 after, close gas bomb 5 immediately, bleeding and making furnace pressure is 0.5Pa, keeps 10 minutes;

6, open reinforced valve 13, make the molten state silicon in the atomizing stove 8 under action of gravity, be back to reinforced stove 1, and the maintenance temperature is 1500 ℃ by feed back pipe 7;

7, above-mentioned steps 4-6 is repeated 8 times.

Using the same method prepares 3 parallel sample, and note is made A1, A2 and A3 respectively.

Embodiment 2

According to method similarly to Example 1, different is that the Heating temperature in the

step

2,3 and 4 is 1700 ℃; The cutoff pressure of bleeding in the step 2 is 5Pa; Reinforced furnace pressure is 0.8MPa in the step 5; The multiplicity of step 7 is 5 times.

Using the same method prepares 3 parallel sample, and note is made B1, B2 and B3 respectively.

Comparative Examples 1

This Comparative Examples is used to illustrate the preparation method of prior art solar energy level silicon

1, under the room temperature, adding is waited to purify for 300 kilograms and is contained the silicon of phosphorus impurities in reinforced stove, and wherein the content of phosphorus impurities is 58ppm;

2, will feed in raw material stove sealing feeds the argon gas of 0.5MPa in stove; Close the argon gas steel cylinder after bleeding 1 minute with vacuum pump, continuing to be pumped to the stove internal gas pressure is 0.2Pa;

3, after heating makes and treats the purified silicon fusing, continue to be heated to 1500 ℃, and kept 80 minutes;

Using the same method prepares 3 parallel sample, and note is made C1, C2 and C3 respectively.

Product test

Measure product A 1-A3, the B1-B3 make and the content of the P among the C1-C3 with ICP-MS (inductivity coupled plasma mass spectrometry) method (Agilent 7500C).Test result is listed in table 1.

Table 1

The present invention prepares the method for solar energy level silicon and utilizes atomization to evaporate the phosphorus of removing in the metallic silicon, with existing There is the phosphorus removing method of technology to compare, greatly increased disengagement area, improved evaporation efficiency, thereby tool Better phosphor-removing effect is arranged.

Claims

1, a kind of silicon method of purifying is characterized in that this method is included under the protection of inert gas, with impure silicon fusion, atomizing, under atomizing state with impurity evaporation.

2, method according to claim 1, wherein, described fused temperature is 1414-1700 ℃.

3, method according to claim 1, wherein, described atomizing is with impure silicon atomizing with atomizing nozzle.

4, method according to claim 3, wherein, the material of described nozzle is selected from one or more in the pottery that graphite, fusing point that molybdenum alloy, fusing point that tungstenalloy, metal molybdenum, fusing point that tungsten, fusing point be not less than 2000 ℃ be not less than 2000 ℃ be not less than 2000 ℃ be not less than 2000 ℃.

5, method according to claim 1, wherein, described atomizing and being evaporated to repeatedly.

6, method according to claim 5, wherein, described atomizing and being evaporated to 3-10 time.

7, according to claim 1,5 or 6 described methods, wherein, the condition of described evaporation comprises that temperature is 1420-2350 ℃, and pressure is 0.001-1000Pa, and the time is 3-30 minute.

8, method according to claim 1, wherein, described rare gas element is one or more in the neutral element gas.

9, according to claim 1 or 3 described methods, wherein, described impurity is phosphorus.