CN113629166A - Polycrystalline silicon surface treatment method - Google Patents
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- 229910021420 polycrystalline silicon Inorganic materials 0.000 title claims abstract description 47
- 238000000034 method Methods 0.000 title claims abstract description 31
- 238000004381 surface treatment Methods 0.000 title claims abstract description 9
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 33
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 33
- 239000010703 silicon Substances 0.000 claims abstract description 33
- 239000003513 alkali Substances 0.000 claims abstract description 32
- 230000007797 corrosion Effects 0.000 claims abstract description 27
- 238000005260 corrosion Methods 0.000 claims abstract description 27
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 21
- 238000004140 cleaning Methods 0.000 claims abstract description 17
- 239000007788 liquid Substances 0.000 claims abstract description 16
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims abstract description 8
- 235000011114 ammonium hydroxide Nutrition 0.000 claims abstract description 8
- 238000005530 etching Methods 0.000 claims description 21
- 230000008569 process Effects 0.000 claims description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 16
- 239000012535 impurity Substances 0.000 claims description 10
- 229910001868 water Inorganic materials 0.000 claims description 10
- 238000005406 washing Methods 0.000 claims description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
- 239000008367 deionised water Substances 0.000 claims description 6
- 229910021641 deionized water Inorganic materials 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 6
- 239000002184 metal Substances 0.000 claims description 6
- 229920005591 polysilicon Polymers 0.000 claims description 6
- 239000013078 crystal Substances 0.000 claims description 5
- 238000004506 ultrasonic cleaning Methods 0.000 claims description 5
- 239000003921 oil Substances 0.000 claims description 4
- 238000010521 absorption reaction Methods 0.000 claims description 3
- 230000003749 cleanliness Effects 0.000 claims description 3
- 238000002474 experimental method Methods 0.000 claims description 3
- 239000002923 metal particle Substances 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 238000007664 blowing Methods 0.000 claims description 2
- 238000009210 therapy by ultrasound Methods 0.000 claims description 2
- 239000000203 mixture Substances 0.000 abstract description 2
- 238000002310 reflectometry Methods 0.000 description 16
- 229910021419 crystalline silicon Inorganic materials 0.000 description 13
- 238000006243 chemical reaction Methods 0.000 description 12
- 238000004458 analytical method Methods 0.000 description 6
- 229910021417 amorphous silicon Inorganic materials 0.000 description 5
- 238000011161 development Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 5
- 238000010248 power generation Methods 0.000 description 5
- 239000002253 acid Substances 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 230000031700 light absorption Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- 238000001039 wet etching Methods 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 239000007888 film coating Substances 0.000 description 1
- 238000009501 film coating Methods 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 238000005247 gettering Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002096 quantum dot Substances 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000005215 recombination Methods 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
- 235000019795 sodium metasilicate Nutrition 0.000 description 1
- 229910052911 sodium silicate Inorganic materials 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- H01L31/02—Details
- H01L31/0236—Special surface textures
- H01L31/02363—Special surface textures of the semiconductor body itself, e.g. textured active layers
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- H01L31/02—Details
- H01L31/0236—Special surface textures
- H01L31/02366—Special surface textures of the substrate or of a layer on the substrate, e.g. textured ITO/glass substrate or superstrate, textured polymer layer on glass substrate
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- H01L31/0747—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN heterojunction type comprising a AIVBIV heterojunction, e.g. Si/Ge, SiGe/Si or Si/SiC solar cells comprising a heterojunction of crystalline and amorphous materials, e.g. heterojunction with intrinsic thin layer
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Abstract
The invention relates to a polycrystalline silicon surface treatment method, which comprises the following steps: preparing a polycrystalline silicon wafer, S1: firstly, cleaning by adopting RCA liquid, wherein the ratio of NH4OH to H2O2 to H2O is 1:1:5, the concentration of NH4OH is 25-28 percent, the concentration of H2O2 is 30 percent, and then adding a silicon wafer for cleaning; then processing with RCA II solution, the mixture ratio is HCl H2O2 and H2O is 1:1:6, the HCl concentration is 36% -38%, then adding silicon chip to clean; s2: after the completion, 6% of HF dilute solution is prepared, and the cleaned silicon wafer is placed into the solution to be soaked for two minutes; s3: after the polycrystalline silicon wafer is corroded by alkali liquor, an uneven structure can be formed on the surface of the silicon wafer; the concentration of NaOH is fixed to be 15%, the temperature of the corrosive liquid is 80 ℃, the corrosion time is set to be 10-20 min, and the concentrations of the alkaline corrosive liquid are respectively set to be 10-20%.
Description
Technical Field
The invention relates to the field of solar cell preparation methods, in particular to a polycrystalline silicon surface treatment method.
Background
The solar power generation technology is a new technology for directly converting light energy into electric energy by utilizing a photovoltaic effect and storing the electric energy, in particular to a silicon-based semiconductor solar cell power generation technology, and since the first c-Si solar cell appears in 1954, the development of a silicon solar cell is further promoted. After the c-Si solar cell is successfully developed, the research on the amorphous silicon solar cell gradually goes into laboratories all over the world, and the amorphous silicon solar cell is successfully prepared in two decades, namely the RCA laboratory dominated by American scientists in 1974. Subsequently, the development of solar cells is more rapid, such as common crystalline silicon solar cells, thin film solar cells, quantum dot solar cells, and the like. The efficiency of a mature component of the crystalline silicon solar cell can reach about 20 percent, and occupies the mainstream position of the market, and the main factors limiting the development are that the purity requirement of the material is strict, the preparation process is complex, and the efficiency is improved to a certain bottleneck; although the amorphous silicon solar cell is low in development cost and suitable for large-area production, the efficiency is not easy to improve, and good repeatability is not provided, so that the market application of the amorphous silicon solar cell cannot be popularized.
At present, the cost of photovoltaic power generation is higher than that of fossil fuel, water energy, nuclear energy and wind energy, and the development of the photovoltaic industry is seriously restricted. In order to take advantage of photovoltaic power generation, it is urgently required to reduce the cost of the battery. In recent years, the technology of solar cell (HIT) power generation with an intrinsic thin layer has been attracting the interest of scientists, and this simple and novel structure has been widely studied in various countries around the world due to its advantages of high conversion efficiency and relatively low cost. The main body of the cell structure is still amorphous silicon and crystalline silicon materials, and the difference of the cell structure from the traditional process is that a layer of intrinsic silicon thin film is added in a PN junction. The intrinsic layer in the HIT solar cell structure enables the cell to passivate the surface of crystalline silicon while forming a PN junction, so that better interface quality can be obtained, and the photoelectric conversion efficiency of the cell can be improved. In addition, compared with the traditional battery, the HIT battery has more outstanding advantages such as high open voltage, stability, low cost and the like, and the battery with the HIT structure has almost no light-induced degradation phenomenon through research. Researchers at the university of Zhongshan think that the monocrystalline silicon HIT solar cell module is more suitable for areas with strong sunlight radiation and wide area through comparison of different areas.
Texturing on the surface of crystalline silicon is one of the commonly used processes in the manufacturing process of solar cell industry. The main purpose of texturing is to increase the absorption of incident light, and the process flow is to use different technologies to texture the surface of polysilicon, thereby improving the final conversion efficiency of the cell. At present, in the aspect of texture etching of crystalline silicon, wet etching is mainly adopted, and specifically, the wet etching method comprises an acid etching method and an alkali etching method. The alkali corrosion method mainly aims at monocrystalline silicon, and the corrosion speed of alkali liquor on crystal grains with different crystal orientations is different, namely anisotropic corrosion, so that uneven surface structures can be formed on the surface, and the structures can increase the multiple reflection probability of incident light on the surface, and achieve the purpose of increasing light absorption. Research finds that the acid etching process has a more obvious effect in the texturing process of polycrystalline silicon, the etching speed of the acid etching solution is the same when the etching solution etches the surface of the polycrystalline silicon, namely isotropic etching, after the polycrystalline silicon is immersed in the acid etching solution, surface defects or mechanical damages can be preferentially etched, so that the phenomenon of preferential etching can be shown, because the energy levels of the parts with relatively poor lattice structures are low, the reaction is easier to carry out, after etching for a certain time, dendritic etching pits can be distributed on the whole surface of the polycrystalline silicon, the absorption of light on the surface of the polycrystalline silicon can be obviously increased, and the photoelectric conversion efficiency of the HIT cell can be improved.
Therefore, further improvements in the polysilicon surface treatment process are needed.
Disclosure of Invention
The invention aims to provide a polycrystalline silicon surface treatment method which can improve the photoelectric conversion efficiency of a polycrystalline silicon substrate HIT solar cell.
In order to achieve the purpose of the invention, the invention provides a polysilicon surface treatment method, which comprises the following steps:
preparing a polycrystalline silicon wafer of 4cm multiplied by 4cm, wherein the thickness is 200 +/-10 mu m, and the resistivity range is 1-3 omega cm;
s1: before the experiment, the polycrystalline silicon wafer is firstly subjected to early-stage treatment; the polycrystalline silicon has more metal impurities, and is required to be subjected to impurity absorption firstly, so that the silicon wafer achieves good quality, and because impurities such as oil stains, metal particles and the like are introduced into the surface of the polycrystalline silicon wafer in the manufacturing process, the surface is required to be cleaned, and the ideal surface cleanliness is achieved; the cleaning process adopts RCA liquid for treatment; firstly, cleaning with RCA liquid, wherein the ratio of NH4OH to H2O2 to H2O is 1:1:5, the concentration of NH4OH is 25-28%, the concentration of H2O2 is 30%, pouring the solution into a beaker, adding a silicon wafer, ultrasonically cleaning at 80 ℃ for 10min, and after ultrasonic cleaning, washing with deionized water for about 4 times; treating with RCA II solution with HCl (H2O 2) and H2O (1: 1: 6) at a concentration of 36-38%, pouring the solution into a beaker, adding a silicon wafer, ultrasonically cleaning at 80 deg.C for 10min, and washing with deionized water for about 4 times after ultrasonic treatment;
s2: after the two cleaning processes are finished, 6% of dilute HF solution is prepared, and the cleaned silicon wafer is placed into the solution to be soaked for two minutes, so that the residual oxide layer on the surface is removed, and the silicon wafer is prevented from being further oxidized; directly blowing the cleaned product by using nitrogen to dry the product until the next experimental treatment;
s3: due to the anisotropic corrosion characteristic of alkali corrosion, the corrosion rates of NaOH solution to different crystal orientations in the alkali corrosion texturing are different, so that the surface of a polycrystalline silicon wafer can form an uneven structure after the polycrystalline silicon wafer is corroded by alkali liquor;
the concentration of NaOH is fixed to be 15%, the temperature of the corrosive liquid is 80 ℃, the corrosion time is set to be 10-20 min, the concentration of the alkali liquor is changed, and the concentrations of the alkali corrosive liquid are respectively set to be 10-20%.
Preferably, the etching time in step S3 is 15 min.
Preferably, the alkali etching concentration in step S3 is 15%.
According to analysis of reflectivity test data, when the concentration of the alkali etching solution is set to be 10%, the reflectivity of the surface of the polycrystalline silicon is about 26.17%, and is reduced compared with the reflectivity of the original silicon wafer (the reflectivity of the original silicon wafer is 35.43%); when the concentration of the alkali liquor is continuously increased to 15%, the reflectivity of the surface of the polycrystalline silicon wafer is reduced to 24.39%, which is lower than the original silicon wafer by more than ten percent, so that the utilization rate of incident light is effectively increased; however, when the concentration of the alkali liquor is increased to 20%, the reflectivity of the surface of the polycrystalline silicon is increased to 25.19%, and the analysis is consistent with the principle analysis, at the moment, the concentration is too high, the reaction process is not easy to control, so that the alkali corrosion liquor continuously corrodes the edges and corners of the original shape during the reaction, the edges and corners are smooth, and the light trapping effect is reduced.
Compared with the prior art, the polycrystalline silicon surface treatment method has the following advantages:
by changing parameters such as alkali corrosion time and alkali corrosion concentration, the conclusion is drawn: when the alkali etching concentration is 15%, the temperature is 80 ℃ and the alkali etching time is 15min, the average reflectivity of the polycrystalline silicon is 24.37%, which is lower than the reflectivity of the original silicon wafer by 35.43%, so that the light energy utilization rate can be effectively increased.
Detailed Description
The present invention will be further described with reference to the following specific examples.
Examples
A4 cm × 4cm piece of polycrystalline silicon was prepared, with a thickness of 200 + -10 μm and a resistivity in the range of 1-3. omega. cm.
S1: before the experiment, the polycrystalline silicon wafer is firstly subjected to pretreatment. The polycrystalline silicon has more metal impurities, and is required to be subjected to gettering firstly, so that the silicon wafer achieves good quality, and because impurities such as oil stains, metal particles and the like are introduced into the surface of the polycrystalline silicon wafer in the manufacturing process, the surface is required to be cleaned, and the ideal surface cleanliness is achieved. The cleaning process adopts RCA liquid for treatment. Firstly, cleaning with RCA liquid, wherein the ratio of NH4OH to H2O2 to H2O is 1:1:5 (the concentration of NH4OH is 25-28 percent, and the concentration of H2O2 is 30 percent), pouring the solution into a beaker, adding a silicon wafer, ultrasonically cleaning for 10min at 80 ℃, and washing with deionized water for about 4 times after ultrasonic cleaning; and then treating with RCA II solution, wherein the proportion of HCl is H2O2: H2O is 1:1:6 (the concentration of HCl is 36-38%), pouring the solution into a beaker, adding a silicon wafer, carrying out ultrasonic cleaning for 10min at 80 ℃, and after ultrasonic cleaning, washing with deionized water for about 4 times.
S2: after the two cleaning processes are finished, 6% of dilute HF solution is prepared, and the cleaned silicon wafer is placed into the solution to be soaked for two minutes, so that the residual oxide layer on the surface is removed, and the silicon wafer is prevented from being further oxidized. After the washing, the mixture is directly blown by nitrogen to be subjected to the next experimental treatment.
Due to the anisotropic corrosion characteristic of alkali corrosion, the corrosion rates of NaOH solution to different crystal orientations in the alkali corrosion texturing are different, so that the surface of the polycrystalline silicon wafer can form an uneven structure after the polycrystalline silicon wafer is corroded by alkali liquor. The chemical reaction equation of the alkali corrosion process is as follows:
Si+2NaOH+H2O＝Na2SiO3+2H2↑
the concentration of NaOH is fixed to be 15%, the temperature of the corrosive liquid is 80 ℃, the corrosion time is set to be 10min, 15min and 20min, the reflectivity is better when the corrosion time is fixed to be 15min and the temperature of the alkaline liquid is fixed to be 80 ℃, at the moment, the concentration of the alkaline liquid is changed, and the influence of the concentration on the reflectivity is researched. The concentrations of the alkaline etching solutions were set to 10%, 15%, and 20%, respectively.
According to analysis of reflectivity test data, when the concentration of the alkali etching solution is set to be 10%, the reflectivity of the surface of the polycrystalline silicon is about 26.17%, and is reduced compared with the reflectivity of the original silicon wafer (the reflectivity of the original silicon wafer is 35.43%); when the concentration of the alkali liquor is continuously increased to 15%, the reflectivity of the surface of the polycrystalline silicon wafer is reduced to 24.39%, which is lower than the original silicon wafer by more than ten percent, so that the utilization rate of incident light is effectively increased; however, when the concentration of the alkali liquor is increased to 20%, the reflectivity of the surface of the polycrystalline silicon is increased to 25.19%, and the analysis is consistent with the principle analysis, at the moment, the concentration is too high, the reaction process is not easy to control, so that the alkali corrosion liquor continuously corrodes the edges and corners of the original shape during the reaction, the edges and corners are smooth, and the light trapping effect is reduced.
The texture surface of the crystalline silicon mainly has the following functions: (1) and removing the mechanical damage layer on the surface of the silicon wafer. When the silicon chip is manufactured, the processes of wire cutting, lapping and the like are carried out, and the damage layer generated on the surface of the silicon chip by the processes can reach dozens of micrometers. In the manufacturing process of the cell, the damage layer is not beneficial to film coating, and a large number of recombination centers are formed on the surface of the crystalline silicon, so that the service life of minority carriers of the substrate is shortened, and the photoelectric conversion efficiency of the solar cell is influenced finally; (2) a clean surface is obtained. When a polycrystalline silicon wafer is produced in a factory, the surface of crystalline silicon can not be contacted with metal instruments and oil stains, so that a large amount of metal and organic impurities can be generated on the surface of the crystalline silicon, and along with the corrosion of the surface in the texturing process, the metal and organic impurities can be removed in the corrosion and cleaning processes, so that the surface of the silicon wafer is kept clean; (3) the light absorption is increased, which is also the main purpose of texturing the surface of the crystalline silicon, and after incident light irradiates the surface of the polycrystalline silicon substrate, the incident light can be absorbed on the surface for multiple times under the action of light reflection and refraction, which is the light trapping effect.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this patent application, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In this specification, unless expressly stated or limited otherwise, the terms "mounted," "connected," and "fixed" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integral to one another; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present specification can be understood by those of ordinary skill in the art as appropriate.
In this specification, unless explicitly stated or limited otherwise, a first feature may be "on" or "under" a second feature such that the first and second features are in direct contact, or the first and second features are in indirect contact via an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (3)
1. A polysilicon surface treatment method is characterized by comprising the following steps:
preparing a polycrystalline silicon wafer of 4cm multiplied by 4cm, wherein the thickness is 200 +/-10 mu m, and the resistivity range is 1-3 omega cm;
s1: before the experiment, the polycrystalline silicon wafer is firstly subjected to early-stage treatment; the polycrystalline silicon has more metal impurities, and is required to be subjected to impurity absorption firstly, so that the silicon wafer achieves good quality, and because impurities such as oil stains, metal particles and the like are introduced into the surface of the polycrystalline silicon wafer in the manufacturing process, the surface is required to be cleaned, and the ideal surface cleanliness is achieved; the cleaning process adopts RCA liquid for treatment; firstly, cleaning with RCA liquid, wherein the ratio of NH4OH to H2O2 to H2O is 1:1:5, the concentration of NH4OH is 25-28%, the concentration of H2O2 is 30%, pouring the solution into a beaker, adding a silicon wafer, ultrasonically cleaning at 80 ℃ for 10min, and after ultrasonic cleaning, washing with deionized water for about 4 times; treating with RCA II solution with HCl (H2O 2) and H2O (1: 1: 6) at a concentration of 36-38%, pouring the solution into a beaker, adding a silicon wafer, ultrasonically cleaning at 80 deg.C for 10min, and washing with deionized water for about 4 times after ultrasonic treatment;
s2: after the two cleaning processes are finished, 6% of dilute HF solution is prepared, and the cleaned silicon wafer is placed into the solution to be soaked for two minutes, so that the residual oxide layer on the surface is removed, and the silicon wafer is prevented from being further oxidized; directly blowing the cleaned product by using nitrogen to dry the product until the next experimental treatment;
s3: due to the anisotropic corrosion characteristic of alkali corrosion, the corrosion rates of NaOH solution to different crystal orientations in the alkali corrosion texturing are different, so that the surface of a polycrystalline silicon wafer can form an uneven structure after the polycrystalline silicon wafer is corroded by alkali liquor;
the concentration of NaOH is fixed to be 15%, the temperature of the corrosive liquid is 80 ℃, the corrosion time is set to be 10-20 min, the concentration of the alkali liquor is changed, and the concentrations of the alkali corrosive liquid are respectively set to be 10-20%.
2. The method for treating the surface of polysilicon according to claim 1, wherein the etching time in step S3 is 15 min.
3. The method for treating the surface of polysilicon according to claim 1, wherein the alkali etching concentration in the step S3 is 15%.
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