CN102344140A - Method for depositing crystalline silica - Google Patents
Method for depositing crystalline silica Download PDFInfo
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- CN102344140A CN102344140A CN2010102444530A CN201010244453A CN102344140A CN 102344140 A CN102344140 A CN 102344140A CN 2010102444530 A CN2010102444530 A CN 2010102444530A CN 201010244453 A CN201010244453 A CN 201010244453A CN 102344140 A CN102344140 A CN 102344140A
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Abstract
The invention, belonging to the technical field of silicon purification, relates to a method for depositing crystalline silica, comprising the following steps: plasmizing raw material gas, then introducing the plasmized raw material gas into a magnetic field for separation to form an air flow I which carres a positive charge and an air flow II which carries a negative charge; introducing the air flow I and bell-type reactor I II respectively into a bell-type reactor I and a bell-type reactor II for depositing; wherein, the raw material gas comprises silane gas. The method disclosed herein effectively inhibits the homogeneous reaction in the depositing process, reduces the generation of silicon particles in gas phase, so as to improve the utilization rate of silane, improve the conversion efficiency of silane, and reduce the cycle cost of the method, so that purity and yield of the prepared crystalline silica are greatly improved.
Description
Technical field
The invention belongs to silicon purification techniques field, relate in particular to a kind of deposition method of crystalline silicon.
Background technology
At present, silane thermal decomposition process is the crystalline silicon working method of using always.Silane thermal decomposition process is to adopt silane pyrolytic decomposition deposited crystal silicon in reactor drum.It has two kinds of implementations: (1) fluidized bed process: in fluidized-bed reactor, deposition generates granular polycrystalline silicon on the silicon seed particle surface; (2) new silane thermal decomposition process: in the bell-jar reactor drum, deposition is produced rod-like polycrystal silicon on the silicon seed bar.
The thermo-efficiency of fluidized bed process is high, and production cost is low.But polycrystalline silicon growth speed is slow, an efficiency of conversion is low, and reduction temperature is high, energy consumption is high, yield poorly.And because the granular polycrystalline silicon specific surface area is big, contaminated easily, product gas purity is low, need combine to come the purity that further improves silicon with other purification process.
New silane thermal decomposition process had appearred afterwards.In the new silane thermal decomposition process, silane collides pyritous silicon seed bar, and thermolysis becomes silicon and hydrogen, and siliceous deposits is on the silicon seed bar.After treating that deposition finishes, take out silicon seed bar (being silicon rod) and promptly get high-purity rod-like polycrystal silicon.
New silane thermal decomposition process, the purity that need not combine additive method to come purified silicon, silane is prone to purify, silicon content higher (87.5%) in the silane, productive rate is high.Produce closed cycle, almost no coupling product is discharged; Low, the little power consumption of heat decomposition temperature, raw material consumption is low.
But in new silane thermal decomposition process, silane gas reaches certain temperature, can spontaneous generation homogeneous reaction.Be the spontaneous decomposition of silane gas meeting, in gas phase, directly generate silicon particle and hydrogen.This homogeneous reaction can seriously reduce end product quality and productive rate.
So the purity of polysilicon in urgent need to be improved and productive rate.
Summary of the invention
Technical problem to be solved by this invention is: in the prior art, the purity of silane-deposited crystalline silicon is low, the problem that productive rate is low, thus the crystalline silicon deposition method that a kind of purity is high, productive rate is high is provided.
A kind of crystalline silicon deposition method, it comprises the steps:
(1) plasma:, form the plasma air-flow with the unstripped gas plasma; Said unstripped gas comprises silane gas;
(2) separate: said plasma (orifice) gas stream is passed in the magnetic field separates, form air-flow I and air-flow II; Said air-flow I is positively charged, and said air-flow II is electronegative;
(3) deposition: said air-flow I, II imported respectively among bell-jar reactor drum I, the II deposit.
Method of the present invention; Effectively suppressed the homogeneous reaction in the deposition process, reduced the generation of silicon particle in the gas phase, the utilization ratio of silane is improved; Improved the transformation efficiency of silane, thereby the purity and the productive rate that have reduced the prepared crystalline silicon of the cycle cost of method have had all significantly and have improved.
Description of drawings
Fig. 1 is a schema of the present invention.
Fig. 2 is the synoptic diagram of magnetic field separation device of the present invention.
Embodiment
Clearer for technical problem, technical scheme and beneficial effect that the present invention is solved, below in conjunction with accompanying drawing and embodiment, the present invention is further elaborated.Should be appreciated that specific embodiment described herein only in order to explanation the present invention, and be not used in qualification the present invention.
A kind of crystalline silicon deposition method, it comprises the steps:
(1) plasma:, form the plasma air-flow with the unstripped gas plasma; Said unstripped gas comprises silane gas;
(2) separate: said plasma (orifice) gas stream is passed in the magnetic field separates, form air-flow I and air-flow II; Said air-flow I is positively charged, and said air-flow II is electronegative;
(3) deposition: said air-flow I, II imported respectively among bell-jar reactor drum I, the II deposit.
The staple of unstripped gas of the present invention is a silane gas, can be pure silane gas, can certainly contain other gases that other do not influence siliceous deposits.
Under the preferable case, also comprise hydrogen in the unstripped gas of the present invention.
Like this, can make unstripped gas plasma more easily, the concentration of silane when having diluted deposition simultaneously improves the utilization ratio of silane, and hydrogen can also take away the silicon particle that homogeneous reaction produces, and avoids the silicon of pollution deposit.Hydrogen can also increase the flow of gas simultaneously, increases the turbulence situation of gas on the silicon seed bar, thereby effectively eliminates the frictional belt.Improve the utilization ratio of silane simultaneously.
In the unstripped gas mol ratio of silane gas and hydrogen be preferably 5: 1～1: 2, more preferably 2: 1～1: 1.So both can avoid hydrogen too much, production efficiency is descended, also avoid of the fluctuation of a large amount of hydrogen silicon seed bar surface temperature.Can make the utilization ratio of silane high again, eliminate the frictional belt simultaneously.
In order to strengthen the purity of deposition silicon, the purity of preferred silane gas of the present invention is preferably greater than 99.999wt%, and the purity of hydrogen is greater than 99.999wt%.
Wherein, plasma is known in those skilled in the art, its objective is can change gas molecule into positive ion, negative ion, electronics, the higher reaction particle of radical isoreactivity.
General common employing such as lower device are realized the plasma of unstripped gas: dielectric barrier discharge plasma device, corona discharge plasma device, glow discharge plasma device, microwave discharge plasma device, rf (discharge) plasma device etc.
The preferred microwave discharge plasma device of the present invention.More preferably the power of its microwave is 400～600W, and frequency is 2.45GHz.
The flow velocity of the plasma air-flow of handling from plasma apparatus is generally 1 * 10
5～10
6M/s.
The high speed plasma air-flow that step (2) will be come out from plasma apparatus directly is passed in the magnetic field and separates, and under the effect in magnetic field, with positive and negative charge particle in the plasma air-flow separately, forms air-flow I and air-flow II.Air-flow I contains positively charged particle, and air-flow II contains electronegative particle.Certainly, all contain a large amount of neutral molecules and radical among air-flow I, the II.
When plasma (orifice) gas flows in the magnetic field, the band positive and negative charge particle in the plasma air-flow promptly receives the influence of lorentz's force under the effect in magnetic field.Because the lorentz's force of the particle of band positive and negative charge is in the opposite direction, thereby the movement path generation of the particle of band positive and negative charge is departed from, thereby reach isolating effect.And the motion of electroneutral particle is unaffected, and is separated at random.
The intensity in the preferred magnetic field of the present invention is 0.005～0.01T.
The present invention preferably adopts following magnetic field separation device to realize: as shown in Figure 2; The magnetic field separation utensil has with " Y " type cavity; This cavity has the end that 2,3, one inlet mouths 1 of an inlet mouth 1 and two air outlets are positioned at cavity, is connected with the outlet of plasma apparatus.The plasma air-flow gets into cavity from inlet mouth 1.There is uniform magnetic field in the cavity region intermediate.The magnetic field width is greater than the width of inlet mouth.Two air outlets 2,3 are positioned at an other end of cavity.Air-flow I and air-flow II flow out from two air outlets respectively.
Certainly, qualified other magneticstrengties that calculate through lorentz's force R=mv/qB and according to the flight path of particle and diameter, the length of magnetic field separation device also can reach isolating purpose.
Step (3) imports the air-flow I after separating and air-flow II respectively among bell-jar reactor drum I, the II and to deposit.Be about to deposit among the air-flow I importing bell-jar reactor drum I, with depositing among the air-flow II importing bell-jar reactor drum II.
Wherein, the bell-jar reactor drum is a device known in those skilled in the art.
In the bell-jar reactor drum, between two electrodes on chassis, three silicon seed bars are installed, form " ∏ " shape current return.Wherein the silicon seed bar at two ends is held with graphite card lobe or graphite awl collet chuck.
Before the deposition reaction, earlier the bell-jar reactor drum is carried out nitrogen purging, hydrogen exchange, then with the silicon seed bar preheated one-section time, the back makes it become conductor with the high-voltage breakdown of 3000～5000V; Perhaps directly use the 12000V high-voltage breakdown behind the hydrogen exchange at normal temperatures.
After the silicon seed bar punctured, the resistance heat that the electric current through the silicon seed bar produces heated up the silicon seed bar, and the temperature of preferably controlling the silicon seed bar is 800～1100 ℃, and the temperature of silicon seed bar is sedimentary temperature.
When temperature reaches, feed air-flow then.
In the deposition process, preferably keeping the pressure (being sedimentary pressure) of whole reactor is 5～20mmHg, more preferably 10～15mmHg.
Responseless silane gas and hydrogen can be got rid of from the tail gas outlet of bell-jar reactor drum.
After deposition finishes, the silicon seed bar is taken out, promptly get high-purity crystal silicon.
When silane gas reaches certain temperature, homogeneous reaction promptly takes place.Be the spontaneous decomposition of silane gas meeting, in gas phase, directly generate silicon particle and hydrogen.This homogeneous reaction can seriously reduce end product quality and productive rate.Contriver of the present invention learns through secular experimental study and analysis, this be because: the silicon particle of generation can be suspended in the silane gas, and particle is less, is submicron particles.And along with the carrying out of reaction, the silicon particle can become the sedimentary core of new decomposition, and promptly silane decomposes deposition at the silicon particle surface.Like this, the silicon particle that suspends in the gas phase is more and more many, and the diameter of silicon particle is more and more big.Owing to be suspended in the silicon particle in the gas phase, its specific surface area is big, adsorbs impurity easily, and purity is low.Some bigger silicon particles drop on the silicon seed bar, and this had both influenced the configuration of surface of silicon seed bar, thereby make the silicon can not be in good, orderly depositing at the silicon seed bar.And can reduce the purity of silicon seed bar, reduce the quality of the finished product.On the also easy inwall of the silicon particle that suspends in addition, because the reactor wall temperature is relatively low attached to reactor drum.When being attached to certain thickness, the silicon particle on the inwall also can come off and drop on the silicon seed bar, thereby produces severe contamination.The generation of silicon particle must influence the sedimentation velocity of silicon on the silicon seed bar in the gas phase, reduces production efficiency, and silicon all is deposited on the silicon seed bar, can reduce the productive rate of HIGH-PURITY SILICON.
Contriver of the present invention is unexpected to find that method of the present invention can effectively improve the purity of silicon and the transformation efficiency of silicon.This be because: at first; The present invention will be with the air-flow of the particle of positive and negative charge deposition respectively separately, because the mutual repellency of like charges, so in air, collide in having reduced between particle and the particle; Thereby reduced the homogeneous reaction of bringing because of collision, suppressed the generation of gas-phase silicon particle.Be connected because the silicon seed bar is pressed with external AC, so the deposition reaction on the silicon seed bar of charged particle, its electrically charged derivation can not caused the accumulation of electric charge, makes reaction can continue to carry out.Finally cause being deposited on the purity and the productive rate of the silicon on the silicon seed bar.The second, the active higher plasma body that the present invention adopts as sedimentary raw material, has increased sedimentary efficient.
Method of the present invention has not only improved the purity of silicon rod, has reduced the loss of silane, and simultaneously owing to the plasma bodyization of silane, has improved a transformation efficiency of silane, has reduced cycle cost.
Below in conjunction with specific embodiment the present invention is done further elaboration.
Embodiment 1
Silane gas is mixed with mol ratio with hydrogen at 1: 1, and with the flow velocity feeding microwave discharge plasma apparatus of 5L/min, controlling its power is 500W, and frequency is 2.45GHz.
The plasma air-flow that will from the microwave discharge plasma apparatus, come out is then directly introduced in the magnetic field separation device.Magneticstrength is controlled at 0.005T in this magnetic field separation device, and the magnetic field separation utensil has with " Y " type cavity, and this cavity has an inlet mouth and two air outlets, and an inlet mouth is positioned at an end of cavity, is connected with the outlet of plasma apparatus.The plasma air-flow gets into cavity from inlet mouth.There is uniform magnetic field in the cavity.The long 1.3m of field region, wide 0.4m.Two air outlets are positioned at an other end of cavity.Air-flow I and air-flow II flow out from two air outlets respectively.
With before air-flow I and the air-flow II feeding bell-jar reactor drum, earlier the bell-jar reactor drum is carried out nitrogen purging, hydrogen exchange again, then the silicon seed bar is preheating to 800 ℃, the back makes it become conductor with the high-voltage breakdown of 5000V.
When the temperature of silicon seed bar reached 850 ℃, among the bell-jar reactor drum I that the air-flow I that separates, II are incorporated into above-mentioned processing, the II, the temperature of control silicon seed bar was 850 ℃, keeps air pressure 10mmHg.
After treating that deposition finishes, the silicon seed bar is taken out from the bell-jar reactor drum, promptly obtain HIGH-PURITY SILICON.Note is made A1.The A1 surface is silver gray, decorative pattern as the no rainbow, and its section is fine and close, does not have obvious interlayer.
Comparative Examples 1
Earlier the bell-jar reactor drum is carried out nitrogen purging, hydrogen exchange, then the preheating of silicon seed bar is reached 800 ℃, the back makes it become conductor with the high-voltage breakdown of 5000V.
After the temperature of silicon seed bar reaches 850 ℃; Again silane gas is mixed with mol ratio with hydrogen at 1: 1; Flow velocity with 5L/min feeds in the bell-jar reactor drum, and the temperature of control silicon seed bar is 850 ℃ in the deposition process, and the pressure in the maintenance bell-jar reactor drum is 10mmHg.
After treating that deposition finishes, the silicon seed bar is taken out from the bell-jar reactor drum, promptly obtain HIGH-PURITY SILICON.Note is made AC1.The AC1 surface is silver gray, decorative pattern as the no rainbow, and the top of silicon rod has bacterium shape thing to generate.
Embodiment 2
Different is with embodiment 1: silane gas mixes with mol ratio with hydrogen at 1: 2, and other parts are with embodiment 1.Obtain the HIGH-PURITY SILICON note and make A2.
Embodiment 3
Different is with embodiment 1: silane gas mixes with mol ratio with hydrogen at 5: 1, and other parts are with embodiment 1.Obtain the HIGH-PURITY SILICON note and make A3.
Embodiment 4
Different is with embodiment 1: hydrogen not in the unstripped gas is pure silane gas; Other parts are with embodiment 1.Obtain the HIGH-PURITY SILICON note and make A4.
Embodiment 5
Different is with embodiment 1: the temperature of control silicon seed bar is 1100 ℃, keeps air pressure 15mmHg.
Other parts are with embodiment 1.Obtain the HIGH-PURITY SILICON note and make A5.
Performance test:
The purity test of silicon: adopt plasma inductance coupling mass spectrograph (ICP-MS) to measure the purity of silicon A1-A5 and AC1, test result such as table 1.
Table 1
| Embodiment | Silicon purity/wt% | Transformation efficiency/the % of silicon |
| Embodiment 1 | 99.9999996 | 98.75 |
| Embodiment 2 | 99.9999993 | 97.63 |
| Embodiment 3 | 99.9999991 | 97.95 |
| Embodiment 4 | 99.9999994 | 98.26 |
| Embodiment 5 | 99.9999992 | 98.51 |
| Comparative Examples 1 | 99.9999989 | 78.80 |
Annotate: the transformation efficiency of silicon is meant the weight of the gain in weight of silicon seed bar divided by element silicon in the silane.
Can find out from table 1, embodiment 1 with respect to Comparative Examples 1 no matter be that the productive rate of purity and the silicon of silicon has all had significantly and improves, this explanation the present invention effectively suppresses the generation of homogeneous reaction, thus the influence of avoiding the silicon particle of homogeneous reaction to bring.The transformation efficiency of other embodiment silicon purity and silicon all remains on higher level, and with respect to Comparative Examples 1 raising is by a relatively large margin arranged also.
The above is merely preferred embodiment of the present invention, not in order to restriction the present invention, all any modifications of within spirit of the present invention and principle, being done, is equal to and replaces and improvement etc., all should be included within protection scope of the present invention.
Claims (10)
1. crystalline silicon deposition method, it comprises the steps:
(1) plasma:, form the plasma air-flow with the unstripped gas plasma; Said unstripped gas comprises silane gas;
(2) separate: said plasma (orifice) gas stream is passed in the magnetic field separates, form air-flow I and air-flow II; Said air-flow I is positively charged, and said air-flow II is electronegative;
(3) deposition: said air-flow I, II imported respectively among bell-jar reactor drum I, the II deposit.
2. crystalline silicon deposition method according to claim 1 is characterized in that: said unstripped gas also comprises hydrogen.
3. crystalline silicon deposition method according to claim 2 is characterized in that: the mol ratio of silane gas and hydrogen is 5: 1～1: 2 in the said unstripped gas.
4. crystalline silicon deposition method according to claim 2 is characterized in that: the purity of said silane gas is greater than 99.999wt%, and the purity of said hydrogen is greater than 99.999wt%.
5. crystalline silicon deposition method according to claim 1 is characterized in that: in step (1) plasma process, the flow of said unstripped gas is 2～10L/min.
6. crystalline silicon deposition method according to claim 1 is characterized in that: said plasma apparatus is the microwave discharge plasma apparatus.
7. crystalline silicon deposition method according to claim 6 is characterized in that: the power of said plasma apparatus is controlled at 400～600W.
8. crystalline silicon deposition method according to claim 1 is characterized in that: in the step (2), the intensity in said magnetic field is 0.005～0.01T.
9. crystalline silicon deposition method according to claim 1 is characterized in that: in the step (3), said sedimentary temperature is 800～1100 ℃.
10. crystalline silicon deposition method according to claim 1 is characterized in that: in the step (3), said sedimentary pressure is 5～20mmHg.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107473228A (en) * | 2017-10-12 | 2017-12-15 | 亚洲硅业（青海）有限公司 | A kind of nanoscale crystalline silicon and preparation method thereof |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4471003A (en) * | 1980-11-25 | 1984-09-11 | Cann Gordon L | Magnetoplasmadynamic apparatus and process for the separation and deposition of materials |
| CN1679142A (en) * | 2002-08-26 | 2005-10-05 | 亚利桑那西格玛实验室公司 | Barrier coatings produced by atmospheric glow discharge |
| CN101456558A (en) * | 2007-12-14 | 2009-06-17 | 邹学柏 | Production process of solar polycrystalline silicon material |
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2010
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4471003A (en) * | 1980-11-25 | 1984-09-11 | Cann Gordon L | Magnetoplasmadynamic apparatus and process for the separation and deposition of materials |
| CN1679142A (en) * | 2002-08-26 | 2005-10-05 | 亚利桑那西格玛实验室公司 | Barrier coatings produced by atmospheric glow discharge |
| CN101456558A (en) * | 2007-12-14 | 2009-06-17 | 邹学柏 | Production process of solar polycrystalline silicon material |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107473228A (en) * | 2017-10-12 | 2017-12-15 | 亚洲硅业（青海）有限公司 | A kind of nanoscale crystalline silicon and preparation method thereof |
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Application publication date: 20120208 |