CN102275932A - Method for laser purification of polycrystalline silicon wafer - Google Patents
Method for laser purification of polycrystalline silicon wafer Download PDFInfo
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- CN102275932A CN102275932A CN2011102027452A CN201110202745A CN102275932A CN 102275932 A CN102275932 A CN 102275932A CN 2011102027452 A CN2011102027452 A CN 2011102027452A CN 201110202745 A CN201110202745 A CN 201110202745A CN 102275932 A CN102275932 A CN 102275932A
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Abstract
The invention provides a method for laser purification of a polycrystalline silicon wafer, and relates to polycrystalline silicon wafers. And the method for laser purification of the polycrystalline silicon wafer provided by the invention has higher efficiency, simple process and less pollution. The method comprises the steps of cleaning a polycrystalline silicon wafer, drying, and placing on a heating platform for preheating; carrying out laser irradiation on the preheated polycrystalline silicon wafer; carrying out irradiation scanning treatment on the treated polycrystalline silicon wafer; annealing the polycrystalline silicon wafer; and etching the surface part of the polycrystalline silicon wafer to obtain a target product. Mass spectrometric analysis shows that the iron content in partial region of the polycrystalline silicon wafer can be reduced by 2-3 orders of magnitude at one time; and the purified polycrystalline silicon wafer can be directly applied to solar cells and the like. The method can be used for directly processing low-purity polycrystalline silicon wafers, can reduce the recycling process of the low-purity silicon in the silicon industry, can realize mass continuous production, and can reduce the phosphorus content in the polycrystalline silicon wafer by laser-melting the silicon wafer and solidifying.
Description
Technical field
The present invention relates to polysilicon chip, especially relate to a kind of method with much more relatively physical metallurgy method polysilicon chips of laser purification foreign matter content.
Background technology
Silicon materials are basic raw materials of preparation silicon solar cell, various silicon discrete devices and various silicon integrated circuits, are the strategic materials of development solar energy industry and information microelectronic industry.
Laser technology has in industrial general application: laser remolten, laser polishing, laser melting coating, laser alloying and disperseization, laser bending, laser sintered, laser growth, material welding, material punching and laser cutting etc.Laser technology also is widely used in semiconductor material and device preparation technology, as laser doping, laser annealing, laser injection, laser scribing and laser lithography etc., but the report that Shang Weijian has laser to purify and use.
Chinese patent CN101092742 discloses a kind of horizontal stretch technology that adopts does not have the method that cutting prepares crystallitic polysilicon chip in use for high performance solar batteries, and the silicon crystal raw material is cleaned purifies earlier is high purity silicon; Again high purity silicon is added an amount of doping agent and place the electric-controlled type high-temperature smelting pot under dustfree environment, to be heated to 1400～1500 ℃ of high temperature, silicon materials are melted fully; Then melted silicon control stretching speed in horizontal stretch equipment is evenly stretched or adopt liquid level float glass process technology to make the crystallitic polysilicon chip of 0.2～0.4mm thickness; At last the wafer of making is organized into and meets the crystallitic polysilicon flake products that uses specification.
Summary of the invention
The objective of the invention is at low-purity silicon chip, particularly purity the existing technical problem of purification, the method with laser purifying polycrystalline silicon sheet that a kind of efficient is higher, technology simple, pollution is less is provided less than the physical metallurgy method polysilicon chip of 6N.
Concrete processing step of the present invention is:
1) with after polysilicon chip cleaning, the oven dry, places on the heating platform and carry out preheating;
In step 1), the purity of described polysilicon chip can be less than 6N, and the purity of described polysilicon chip is preferably 4～6N; The thickness of described polysilicon chip can be 0.1～3mm; The temperature of described preheating can be 100～750 ℃, and the time of preheating can be 5～120s.
2) carry out irradiation with the polysilicon chip of laser after to preheating;
In step 2) in, it is the laser of rectangle, circle or geometrical shape such as linear that described laser can adopt light spot shape, the energy distribution of described laser can be distribution modes such as uniform distribution or Gaussian distribution, described Wavelength of Laser can be 1.064 μ m, 0.98 μ m or 10.6 μ m equiwavelengths, the mode of operation of described laser can be continuous laser or pulse laser, described laser energy be adjusted to can make silicon chip that fusing takes place laser to be any angle with the silicon chip plane, described angle is preferably 90 ° or 60 °.
3) make laser carry out the irradiation scan process to polysilicon chip;
In step 3), the described concrete grammar that makes laser carry out the irradiation scan process to polysilicon chip can adopt mobile laser or move the method for silicon chip by platform; The described laser that makes carries out can feeding rare gas element protection to polysilicon chip in the irradiation scanning process to polysilicon chip, and described rare gas element can adopt nitrogen, argon gas or helium etc.
4) polysilicon chip is carried out anneal;
In step 4), described anneal can be carried out anneal to polysilicon chip in nitrogen, argon gas; The method of described anneal can adopt laser to produce the method that moves relative to polysilicon chip, and described mobile speed can be 0～50mm/s; Described anneal can be carried out in gas, and described gas can be air or rare gas element, and described rare gas element can adopt nitrogen, argon gas or helium etc.; The temperature of described anneal can be 300～900 ℃, and the time of anneal can be 1～30min.
5) etch polysilicon sheet top layer part obtains target product.
In step 5), the method for described etch polysilicon sheet top layer part can be used the method for wet etching or dry etching, and polysilicon chip laser irradiated surface etching is removed 0.5～100 μ m.
The present invention utilizes laser, and scanning makes the silicon chip subregion melting and refreezing take place admittedly as thermal source, and this process is similar to directional freeze.Mainly be that to utilize the equilibrium segregation coefficient Ks of metallic impurity in silicon such as Fe in the silicon, Al, Au (be K＜＜1 much smaller than 1, equilibrium segregation coefficient K be defined as impurity in solid phase silicon concentration and in liquid-phase silicone the ratio of concentration) characteristic, effectively separate purification.After the general directional freeze, the size of the qualified regional shared total material volume ratio of purifying is decided according to the state of the art of directional freeze.The subregion foreign matter content is higher, and purity is about about 5N, can not directly prepare commercial solar cell, generally need reclaim reworking again, makes cost improve.The present invention is that the silicon ingot with these low-purity is cut into silicon chip, utilizes laser as thermal source, and polysilicon chip is carried out scan process, and the polysilicon chip that purity is low relatively melts recrystallize, makes the purity of polysilicon chip be improved.Have certain researching value and commercial value.
Compare with the method for purification of existing polysilicon, the present invention has following outstanding advantage:
1) mass spectroscopy shows, the present invention can once reduce by 2～3 orders of magnitude with the subregional iron level in polysilicon chip middle part.
What 2) the present invention is directed to is the purification of sheet polycrystalline silicon material, can directly apply to application such as solar cell after the purification.
3) the present invention directly processes the polysilicon chip of low-purity, reduces the processing of recovery again of low-purity silicon in the silicon industry.
4) laser is with respect to the silicon chip motion scan, in enormous quantities continuous production.
5), also can reduce the content of phosphorus in the polysilicon chip by laser fusion silicon chip resolidification owing to the vapour pressure height of phosphorus.
Description of drawings
Fig. 1 is polysilicon chip surface topography comparison diagram before and after the laser irradiation scanning.In Fig. 1, before a is laser irradiation, after b is laser irradiation.
Fig. 2 is Fe content SIMS (second ion mass spectroscopy analysis) analysis chart in the original polysilicon chip.In Fig. 2, X-coordinate is the degree of depth (μ m), and ordinate zou is concentration (atoms/cm
3); Mark ● represent the Fe content in the original polysilicon chip crystal grain, ▲ represent the Fe content on the polysilicon chip crystal boundary.
Fig. 3 is Fe content sims analysis figure in the polysilicon chip after laser fusion solidifies.In Fig. 3, X-coordinate is the degree of depth (μ m), and ordinate zou is concentration (atoms/cm
3); Mark ● represent the Fe content in the silicon chip behind the laser melting, crystal boundary does not observe.
Embodiment
Embodiment 1
With thickness is the polysilicon chip of 180 μ m, through behind the cleaning, drying, silicon chip is placed on the quartz plate, and quartz plate is placed on the heating platform, prevents the pollution of heating platform to silicon chip.300 ℃ of preheating temperatures, warm up time 30s.Use light spot shape to be rectangle then, long 20mm, wide 0.5mm, the laser power uniform distribution, laser power is the continuous Nd of 230W: YAG laser, laser beam and silicon chip plane are 90 °, with the speed motion scan of relative silicon chip 3mm/s.Take out silicon chip then, 700 ℃ of annealing 15min in nitrogen atmosphere.Take out silicon chip, with the laser irradiated surface of plasma etching silicon chip, etching gas is SF
6, gas flow is 25sccm, promptly gets the target silicon chip behind the etching 4 μ m.
Show with the iron level in the SIMS test sample 10 μ m degree of depth: in the original silicon chip in the crystal grain iron level 10
15～10
17Atoms/cm
3The order of magnitude.Silicon chip after the process laser irradiation scanning shows can't see crystal boundary, and its iron level is reduced to less than 5 * 10
14Atoms/cm
3
With thickness is the polysilicon chip of 190 μ m, through behind the cleaning, drying, silicon chip is placed on the quartz plate, and quartz plate is placed on the heating platform, prevents the pollution of heating platform to silicon chip.250 ℃ of preheating temperatures, warm up time 60s.Use light spot shape to be rectangle then, long 20mm, wide 0.5mm, the laser power uniform distribution, laser power is the continuous Nd of 220W: YAG laser, laser beam and silicon chip plane are 90 °, with the speed motion scan of relative silicon chip 2mm/s.Take out silicon chip then, 600 ℃ of annealing 20min in nitrogen atmosphere.Take out silicon chip, with the laser irradiated surface of plasma etching silicon chip, etching gas is SF
6, gas flow is 25sccm, promptly gets the target silicon chip behind the etching 3 μ m.
Detect iron level from original silicon chip iron level 10
15～10
17Atoms/cm
3The order of magnitude, its iron level is reduced to less than 4 * 10
14Atoms/cm
3, promptly iron level is less than 10ppb.
Embodiment 3
With thickness is the polysilicon chip of 200 μ m, through behind the cleaning, drying, silicon chip is placed on the quartz plate, and quartz plate is placed on the heating platform, prevents the pollution of heating platform to silicon chip.450 ℃ of preheating temperatures, warm up time 30s.Use light spot shape to be circle then, diameter 2cm, power is distributed as Gaussian distribution, and laser power is the continuous Nd of 300W: YAG laser, laser beam and silicon chip plane are 90 °, with the speed motion scan of relative silicon chip 4mm/s.Take out silicon chip then, 700 ℃ of annealing 20min in nitrogen atmosphere.Take out silicon chip, with the laser irradiated surface of plasma etching silicon chip, etching gas is SF
6, gas flow is 25sccm, promptly gets the target silicon chip behind the etching 3 μ m.
Detect iron level from original silicon chip iron level 10
15～10
17Atoms/cm
3The order of magnitude, its iron level is reduced to less than 2 * 10
14Atoms/cm
3
The invention provides a kind of method of purification that fast, effectively improves polysilicon chip purity, particularly a kind of purification technique of removing metallic impurity in the physical metallurgy method polysilicon chip.By laser irradiation scanning silicon chip, impurity divides coherent set in polysilicon chip, and silicon chip purity is improved among the present invention.
The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.
Claims (10)
1. method with laser purifying polycrystalline silicon sheet is characterized in that its concrete processing step is:
1) with after polysilicon chip cleaning, the oven dry, places on the heating platform and carry out preheating;
2) carry out irradiation with the polysilicon chip of laser after to preheating;
3) make laser carry out the irradiation scan process to polysilicon chip;
4) polysilicon chip is carried out anneal;
5) etch polysilicon sheet top layer part obtains target product.
2. a kind of method with laser purifying polycrystalline silicon sheet as claimed in claim 1 is characterized in that in step 1) the purity≤6N of described polysilicon chip.
3. a kind of method with laser purifying polycrystalline silicon sheet as claimed in claim 2 is characterized in that in step 1) the purity of described polysilicon chip is 4～6N.
4. as claim 1 or 2 or 3 described a kind of methods, it is characterized in that in step 1) the thickness of described polysilicon chip is 0.1～3mm with laser purifying polycrystalline silicon sheet.
5. a kind of method with laser purifying polycrystalline silicon sheet as claimed in claim 1 is characterized in that in step 1) the temperature of described preheating is 100～750 ℃, and the time of preheating is 5～120s.
6. a kind of method with laser purifying polycrystalline silicon sheet as claimed in claim 1 is characterized in that in step 2) in, it is rectangle, circle or linear that described laser adopts light spot shape; The energy distribution of described laser is uniform distribution or Gaussian distribution.
7. as claim 1 or 6 described a kind of methods with laser purifying polycrystalline silicon sheet, it is characterized in that in step 2) in, described Wavelength of Laser is 1.064 μ m, 0.98 μ m or 10.6 μ m, the mode of operation of described laser is continuous laser or pulse laser, described laser energy be adjusted to can make silicon chip that fusing takes place laser to be any angle with the silicon chip plane, described angle is preferably 90 ° or 60 °.
8. a kind of method with laser purifying polycrystalline silicon sheet as claimed in claim 1 is characterized in that in step 3), and the described concrete grammar that makes laser carry out the irradiation scan process to polysilicon chip adopts mobile laser or moves the method for silicon chip by platform; The described laser that makes carries out in the irradiation scanning process polysilicon chip, feeds rare gas element to polysilicon chip and protects; Described rare gas element preferably adopts nitrogen, argon gas or helium.
9. a kind of method with laser purifying polycrystalline silicon sheet as claimed in claim 1 is characterized in that in step 4) described anneal is carried out polysilicon chip in nitrogen, argon gas; The method of described anneal adopts laser to produce the method that moves relative to polysilicon chip, and described mobile speed is preferably 0～50mm/s; Described anneal is carried out in gas, and described gas is air or rare gas element, and described rare gas element can adopt nitrogen, argon gas or helium; The temperature of described anneal is preferably 300～900 ℃, and the time of anneal is preferably 1～30min.
10. a kind of method as claimed in claim 1 with laser purifying polycrystalline silicon sheet, it is characterized in that in step 5), the method of described etch polysilicon sheet top layer part is to use the method for wet etching or dry etching, and the best etching of polysilicon chip laser irradiated surface is removed 0.5～100 μ m.
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| CN102275932B CN102275932B (en) | 2013-05-08 |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107170697A (en) * | 2017-04-27 | 2017-09-15 | 昆山国显光电有限公司 | A kind of annealing of substrates device |
| CN107324340A (en) * | 2017-08-14 | 2017-11-07 | 大连理工大学 | A kind of apparatus and method for reclaiming Buddha's warrior attendant wire cutting silica flour waste material |
| CN108033454A (en) * | 2018-01-18 | 2018-05-15 | 苏明杰 | A kind of quartz sand purifying method |
| CN110143594A (en) * | 2019-06-19 | 2019-08-20 | 中国科学院宁波材料技术与工程研究所 | A kind of methods and applications of induced with laser Si oxide disproportionation |
| CN111486704A (en) * | 2020-04-10 | 2020-08-04 | 上海大学 | Laser heat source smelting purification method |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101404307A (en) * | 2008-10-29 | 2009-04-08 | 中山大学 | Production method for polycrystalline silicon solar cell texture surface |
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Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101404307A (en) * | 2008-10-29 | 2009-04-08 | 中山大学 | Production method for polycrystalline silicon solar cell texture surface |
Non-Patent Citations (1)
| Title |
|---|
| 方芳等: "激光再结晶和氢退火对多晶硅电学性质的影响", 《电子科学学刊》 * |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107170697A (en) * | 2017-04-27 | 2017-09-15 | 昆山国显光电有限公司 | A kind of annealing of substrates device |
| CN107324340A (en) * | 2017-08-14 | 2017-11-07 | 大连理工大学 | A kind of apparatus and method for reclaiming Buddha's warrior attendant wire cutting silica flour waste material |
| CN107324340B (en) * | 2017-08-14 | 2019-04-12 | 大连理工大学 | A kind of device and method recycling Buddha's warrior attendant wire cutting silicon powder waste material |
| CN108033454A (en) * | 2018-01-18 | 2018-05-15 | 苏明杰 | A kind of quartz sand purifying method |
| CN110143594A (en) * | 2019-06-19 | 2019-08-20 | 中国科学院宁波材料技术与工程研究所 | A kind of methods and applications of induced with laser Si oxide disproportionation |
| CN111486704A (en) * | 2020-04-10 | 2020-08-04 | 上海大学 | Laser heat source smelting purification method |
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| CN102275932B (en) | 2013-05-08 |
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