CN102275932B - Method for laser purification of polycrystalline silicon wafer - Google Patents
Method for laser purification of polycrystalline silicon wafer Download PDFInfo
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- CN102275932B CN102275932B CN 201110202745 CN201110202745A CN102275932B CN 102275932 B CN102275932 B CN 102275932B CN 201110202745 CN201110202745 CN 201110202745 CN 201110202745 A CN201110202745 A CN 201110202745A CN 102275932 B CN102275932 B CN 102275932B
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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 dispersion, 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 there is not yet the report that laser is purified and used.
Chinese patent CN101092742 discloses a kind of horizontal stretch technique that adopts and prepares the method for crystallitic polysilicon chip in use for high performance solar batteries without cutting, and first the silicon crystal raw material being cleaned purifies is high purity silicon; Again high purity silicon is added appropriate doping agent and be placed in the electric-controlled type high-temperature smelting pot be heated to 1400～1500 ℃ of high temperature under dustfree environment, silicon materials are melted fully; Then with melted silicon restrained stretching speed Uniform Tension or adopt liquid level float glass process technology to make the crystallitic polysilicon chip of 0.2～0.4mm thickness in horizontal stretch equipment; 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 for low-purity silicon chip, the particularly purity existing technical problem of purification less than the physical metallurgy method polysilicon chip of 6N, provide that a kind of efficient is higher, technique is simple, the method with laser purification of polycrystalline silicon wafer of less pollution.
Concrete technology step of the present invention is:
1) with after polysilicon chip cleaning, oven dry, place on heating platform and carry out preheating;
In step 1) in, 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) polysilicon chip after to preheating carries out irradiation with laser;
In step 2) in, it is the laser of rectangle, circle or the geometrical shape such as linear that described laser can adopt light spot shape, the energy distribution of described laser can be the distribution modes such as even distribution or Gaussian distribution, the wavelength of described 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 is adjusted to the laser that can make silicon chip that fusing occurs to be any angle with the silicon chip plane, and described angle is preferably 90 ° or 60 °.
3) make laser carry out the irradiation scan process to polysilicon chip;
In step 3) in, the described concrete grammar that makes laser carry out the irradiation scan process to polysilicon chip can adopt mobile laser or the method by the platform movement silicon chip; The described laser that makes carries out can passing into 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) in, 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 the speed of described movement 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 surface part, obtain target product.
In step 5) in, the method for described etch polysilicon sheet surface 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 silicon chip subregion generation melting and refreezing solid as thermal source, and this process is similar to directional freeze.Mainly that to utilize the equilibrium segregation coefficient Ks of metallic impurity in silicon such as Fe in 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, carry out effective separating-purifying.After 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 the 5N left and right, can not directly prepare commercial solar cell, generally needs again to reclaim processing 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 relatively low 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 advantages:
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 the application such as solar cell after 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 with respect to the silicon chip motion scan, can be produced in enormous quantities continuously.
5) vapour pressure due to phosphorus is high, also can reduce the content of phosphorus in polysilicon chip by laser fusion silicon chip resolidification.
Description of drawings
Fig. 1 is polysilicon chip surface topography comparison diagram before and after 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 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 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 after laser melting, crystal boundary does not observe.
Embodiment
Embodiment 1
Be the polysilicon chip of 180 μ m with thickness, through after cleaning, drying, silicon chip be placed on quartz plate, quartz plate is placed on heating platform, prevents that heating platform is to the pollution of silicon chip.300 ℃ of preheating temperatures, warm up time 30s.Then use light spot shape to be rectangle, long 20mm, wide 0.5mm, laser power evenly distributes, and 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.Then take out silicon chip, 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, namely gets the target silicon chip after etching 4 μ m.
Show with the iron level in the SIMS test sample 10 μ m degree of depth: in original silicon chip in crystal grain iron level 10
15～10
17Atoms/cm
3The order of magnitude.Show through the silicon chip after laser irradiation scanning and can't see crystal boundary, its iron level is reduced to less than 5 * 10
14Atoms/cm
3
Be the polysilicon chip of 190 μ m with thickness, through after cleaning, drying, silicon chip be placed on quartz plate, quartz plate is placed on heating platform, prevents that heating platform is to the pollution of silicon chip.250 ℃ of preheating temperatures, warm up time 60s.Then use light spot shape to be rectangle, long 20mm, wide 0.5mm, laser power evenly distributes, and 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.Then take out silicon chip, 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, namely gets the target silicon chip after 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, namely iron level is less than 10ppb.
Embodiment 3
Be the polysilicon chip of 200 μ m with thickness, through after cleaning, drying, silicon chip be placed on quartz plate, quartz plate is placed on heating platform, prevents that heating platform is to the pollution of silicon chip.450 ℃ of preheating temperatures, warm up time 30s.Then use light spot shape to be circle, 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.Then take out silicon chip, 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, namely gets the target silicon chip after 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 physical metallurgy method polysilicon chip.Scan silicon chip by laser irradiation in the present invention, impurity is minute coherent set in polysilicon chip, and silicon chip purity is improved.
The above; only for the better embodiment of the present invention, but protection scope of the present invention is not limited to this, 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 are within all should being encompassed in protection scope of the present invention.
Claims (11)
1. method with laser purification of polycrystalline silicon wafer is characterized in that its concrete technology step is:
1) with after polysilicon chip cleaning, oven dry, place on heating platform and carry out preheating; Purity≤the 6N of described polysilicon chip; The thickness of described polysilicon chip is 0.1～3mm;
2) polysilicon chip after to preheating carries out irradiation with laser;
3) make laser carry out the irradiation scan process to polysilicon chip;
4) polysilicon chip is carried out anneal;
5) etch polysilicon sheet surface part, obtain target product.
2. a kind of method with laser purification of polycrystalline silicon wafer as claimed in claim 1, is characterized in that in step 1), and the purity of described polysilicon chip is 4～6N.
3. a kind of method with laser purification of polycrystalline silicon wafer as claimed in claim 1, is characterized in that in step 1), and the temperature of described preheating is 100～750 ℃, and the time of preheating is 5～120s.
4. a kind of method with laser purification of polycrystalline silicon wafer 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 evenly to distribute or Gaussian distribution.
5. a kind of method with laser purification of polycrystalline silicon wafer as described in claim 1 or 4, it is characterized in that in step 2) in, the wavelength of described 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, and described laser energy is adjusted to the laser that can make silicon chip that fusing occurs to be 90 ° or 60 ° with the silicon chip plane.
6. a kind of method with laser purification of polycrystalline silicon wafer as claimed in claim 1, is characterized in that in step 3), the described method that makes laser carry out the concrete grammar mobile laser of employing of irradiation scan process to polysilicon chip or pass through the platform movement silicon chip; The described laser that makes carries out passing into rare gas element protection to polysilicon chip in the irradiation scanning process to polysilicon chip.
7. a kind of method with laser purification of polycrystalline silicon wafer as claimed in claim 6, is characterized in that described rare gas element adopts nitrogen, argon gas or helium.
8. a kind of method with laser purification of polycrystalline silicon wafer as claimed in claim 1, is characterized in that in step 4), and 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 the speed of described movement is 0～50mm/s; Described anneal is carried out in gas, and described gas is air or rare gas element.
9. a kind of method with laser purification of polycrystalline silicon wafer as claimed in claim 8, is characterized in that described rare gas element adopts nitrogen, argon gas or helium.
10. a kind of method with laser purification of polycrystalline silicon wafer as claimed in claim 1, is characterized in that in step 4), and the temperature of described anneal is 300～900 ℃, and the time of anneal is 1～30min.
11. a kind of method with laser purification of polycrystalline silicon wafer as claimed in claim 1, it is characterized in that in step 5), the method of described etch polysilicon sheet surface part is to use the method for wet etching or dry etching, and polysilicon chip laser irradiated surface etching is removed 0.5～100 μ m.
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| CN 201110202745 CN102275932B (en) | 2011-07-19 | 2011-07-19 | Method for laser purification of polycrystalline silicon wafer |
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| CN102275932B true CN102275932B (en) | 2013-05-08 |
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| CN107170697B (en) * | 2017-04-27 | 2019-12-24 | 昆山国显光电有限公司 | Substrate annealing device |
| 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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Granted publication date: 20130508 Termination date: 20190719 |