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低温净化冶金硅工艺

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黉 Press Trans.Nonferrous Met.Soc.China 21(201 1)1 185-1 192 Ava・i:la;bl e o,nSlinec aite 1^,nvIn^cf.secieDnceidrierct.cto m Transactions of Nonferrous Metals Society of China www.tnmsc.cn Low—temperature puriicatifon process of metallurgical silicon ZHAO Li.xin 一,WANG Zhi ,GUO Zhan.cheng ,一,LI Cheng。yi 1.National Engineering Laboratory for Hydrometallurgica1 Cleaner Production Technology, Institute of Process Engineering,Chinese Academy of Sciences,Beijing 1 00 1 90,ChiIla: 2.Graduate University of Chinese Academy of Sciences,Beijing 100049,China; 3.State Key Laboratory ofAdvanced Metallurgy, University of Science nd aTechnology Beijing,Beijing 1 00083,China; 4.School of Chemical and Environmental Engineering. China University ofMining nd aTechnology,Beijing l00083,China Received 22 October 20 1 0;accepted 24 November 20 1 0 Abstract:The removal of B and P consumes most Of heat energy in Si metallurgical puffication process for solar-grade Si. Meta1.1iquating puriifcation of metallurgical radeg silicon(MG.Si).also called Si.recrystallization from metal1iquid.was a potential energy.saving method for the removal of B and P eficifently,since Si could be melted at lower temperature by alloying wih metta1. The selection criteria of meta1.1iquating syrstem was elaborated,and A1,Sn and In were selected out as the optimum metallic medims.For Sn.Siu system.the segregafion coe ̄cient of B decreased to 0.038 at 1 500 K,which was much less than 0.8 at the melting point ofSi.The mass fraction ofB was diminished from 15×10-o tO 0.1x10_o as MG.Si was puriied by ftwice.while that of most metallic elements could be decreased to 0.1 x 10_。by pufffying iust once.During he tmeta1.1iquating process,the formation of compounds between impurity elements and Si was also an important route of impurity remova1.Finally,one low.temperature metallurgical process based on metal-liquating method was proposed. Key words:metal1iquating method;metallrgiucal purification process:tin.silicon system:solar grade silicon Because of the character difference among impurities.no 1 Introduction With the rapid development of photovoltaic industry, the main feed stock for solar cell called solar grade method can high.effectively remove all the impurities once for all and the process is always the combination of diferent means[2].The impurities inside MG.Si can be classified into two categories:some are solid.dissolved inside Si matrix and some segregate at grain boundaries. For metallic impurities.the liquid.solid segregation coeficientf of which is far less than 1.most of them silicon(SoG.Si)falls into the sattus of seriOUS shortage. Among new technologies for SOG.Si under researching. metallurgical process is one of the most potential appropriative methods[1].Recently,some tiral products Of mis process have been marketed and their solar cells have also come out.HoweveL most of the approaches segregate out at Si grain boundaries.To remove the segregated impurities,acid leaching is an effective method.The removal e伍ciency of acid-leaching can used in metallurgical process,such as slagging refining, vacuum refining and plasma treating,should be carried reach up to 95%『31.The solid.dissoIved metallic impurities,especially transitional elements,though their out at high temperature(higher hatn he tmelting point of si)for a long time.Therefore.1ow.cost is still the challenge for metallrgicalu process and searching for amount is trace.can still seriously decrease the e伍ciency of solar cell[41.T0 remove these impurities, unidirectional solidiication or zone reffining is an effective method.But nonmetallic impurities.especially new low—cost technology is always its research trend. Metallurgical process is actually the orderly. purifying process of silicon,in which the impurities are B nd tahe segregation coefficients ofwhich re a0.8 and 0.35.respectively,are almost completely solid.dissolved removed step by step from metallrgiucal silicon(MG—Si). inside Si matrix.so acid lcaching and unidirectiona1 Foundation item:Project(2009BAB49B04)supposed by National Key Technologies R&D Program,China Corresponding author:GUO Zhan—cheng;Tel/Fax:+86—10—62579402,62558489;E—mail:zcguo@metal1.ustb.edu.ca DOI:10.1O16/S10O3—6326r11)60841-8 l186 ZHAO Li—xin,et al/Trans.Nonferrous Met.Soc.China 21(2011)1185—1192 solidification are not effective methods.Methods of oxidation and slag refining are perfect for the removal of B with higher content.but not competent for B wim trace content[5—7].Whi1e the plasma treatment is effective for the removal of B,the input Of MG.Si must be little during puriifcation so that B can react with reactive gas as soon as possible.Thereby the仃eatment capacity of plasma process is small and its energy consumption is high[8一l1】.For P,the higher saturated vapor pressure by contrast with Si makes it possible to be removed by vacuum refining.However,the remova1 rate of P becomes very 1ow with the decrease of its concen仃ation. If the removal rate was accelerated by increasing the evaporation area,the loss of Si,the energy consumption and the manufacture diifculty of equipment increase rapidly[12—14].Among the puriifcation methods used in metallurgical process recentlN Si must be molten so that impuriyt atoms can easily transfer within Si matrix.Long time of high—temperature operation determines its higher energy consumption,especially for hte removal of B and P,and the larger segregation coefifcients make them dififcult to be removed by traditional segregation methods.In brief,the high.efifciency remova1 of B and P is actually the key of saving energy,and the low—temperature purification technology and higher removal rate of B and P are two main approaches of low.cost metallurgical process. CHEN and P NG『1 5]proposed one method to remove B from MG—Si under the atmosphere of vapor/nirtogen at low temperature(900。c、.Since Si was still solid at this temperature.the transfer of impuriyt atoms inside Si particle was the control step during purification.and the remova1 efHciency of B was very low.Y0SHIK and MORJTA『1 61 proposed one method of A1-Si alloying to purify MG—Si.During the purification process.MG.Si firstly melted into meta1 1iquid and then recrystallized out.Here it is named meta1.1iquating process.Since Si can be melted at temperature far lower than the Si melting point,the method can make energy.saving possible.The meta1. 1iquating method has ever been used to prepare the polycrystalline.Si thin film for solar cel1.which is called liquid phase epitaxy(LPE).During LPE,poly-Si thin iflm grows slowly from the saturated alloying liquid of Si.Many metals such as A1,Sn and In have been used as mediums[17—19].Commonly,the deposition rate of thin iflm is very slow and rigorous temperature gradient is needed so that crystals grow perfectly and few defects are developed.Like other metallrugical purification methods. metal-liquating method also could not directly purify MG—Si to meet the demand of SoG.Si.and it stil1 needs to combine with other methods. 西ile YOSH删 and MORITA[1 6]adopted metal—liquating method to improve zone refining of Si.more details such as the link with other method were not stated and the proposed process was not fit for large.scale production. In this study,the metal-liquating method using Sn.Si system including the choice of medium.the principle of purification,the separation of metal and the combination with other methods was investigated. Finally,one low—temperature metallurgical process based on metal。liquating was proposed. 2 Selection of metal—liquation system If solid—dissolved impurities inside Si could easily transfer and could be rapidly removed under low temperature。MG—Si must be firstly melted.This can be realized just by metal—liquating method.when silicon is alloyed with meta1.or say Si is dissolved into the molten meta1.MG.Si could melt down at temperature even much lower than Si melting point.As the alloy liquid is cooled.Si could recrystallize and the impurities remain inside the metal liquid.The metal-liquating purification method is also the recrystallization purification of Si from metal liquid.The meta1 used can be regarded as the medium for meta1.1iquating. The keys of the method are to melt Si under low temperature and to purify Si through recrystallization. The purpose of the method is to achieve the energy-saving purification of MG-Si under low temperature.Though many kinds of metals can dissolve Si at low temperature.only a few are the competent liquation medium.The selection criteria of media are listed below: 1、No intermediate compound generated.The generation of the intermediate compound between medium and Si would result in seriPUS entrainment of the meta1.Further,it is difficult for the 1atter process to separate medimu,and the loss of medium would also be serious. 2、Low concentration of Si at eutectic point and low temperature of eutectic point.At eutectic point,Si would co.crystallize with meta1.The eutectics are commonly binary alloy and have uniform microstructure for Si.meta1 systems.It is dififcult to separate them and the loss of Si is serious.Furthermore,at temperature higher than the eutectic point,plenty of Si would dissolve into meta1 liquid.So the lower the temperature of eutectic point is,the more possible the energy—saving of purification process would be. 3)Small segregation coefifcient of impurities between Si and meta1.When Si recrystallizes from medium.the impurities would redistribute between Si crystal and metal liquid.Low segregation coefifcient of impurities can ensure the high purification efifciency. I/ : 霉Q(1g0 ZHAO Li—xin,et al/Trans.Nonferrous Met.Soc.China 21(2011)1185—1192 1189 process.impurities would remain in the liquid according to segregation coefifcient.The good fluidity of metallic liquid is beneficial for the transfer of impuriyt.Because hte temperature is much lower during meta1.1iquating. most impurities together with Si can form the intermediate compounds,which can be removed before the alloying liquid was cooled.Figure 4 shows the phase diagram Of Fe.Si system.The arrow in the diagram points out that Fe can form Fe Si7 with Si at 1 300。C. The formation of inclusion provides evidence that the compound forms in advance.and then attaches to the surface of Si crystal as Si recrystallizes out(Fig.3Co)). 9_0 ,s0一 .1T1(I旨一 0 I10一=l譬毒∞∞对 Fig.4 Phase diagram of Fe—Si system The removal of the compounds first rapidly reduces hte content of impurities in the liquid.Later,when Si recrystallizes out.the removal e师ciency would further increase.This view point is similar with that proposed by Y0SHIKAWA『1 61.In his research,the removal mode of B was discussed.He proposed that B formed compound together witll Ti.which lragely boosted the removal efnciency of B.However,the mass fraction of B in MG—Si was low,commonly less than 60x1O一.In our study,no compound Of TiB was detected. 3.3 Purification efifciency of metal-liquating method 1.5 g MG—Si was mixed together with 23.5 g tin (purity 99.9%1 in graphite crucible.The mixture was melted nuder the atmosphere ofargon at 1 200。C for 1 h. Then the melt was cooled to 600。C at a cooling rate of 3.5。C/min.The recrystallized Si was separated out by ifltration with hte quartz filter.The Si crystal was leached by aqua regia to remove the attached tin,and then was analyzed by inductively coupled plasma—atomic emission spectrometry(ICP—AES). Figure 5 shows the concen仃ation of impuriyt of MG—Si before and after Sn—Si meta1.1iquating for once nad twice.Commercial MG.Si was used,and its 仃ademark was 1 101.The main impufities of MG.Si and their corresponding mass fraction(10_。)were listed as: Impurity element Fig.5 Concentration of impurity of MG-Si before and after Sn—Si metal—liquating Fe 1238,Al 1054,B 15.4,Ti 195,P 223,V 155 and Mn 1l4. The result utrns out that山e meta1.1iquating of Sn.Si has a high removal efficiency for the metallic impurities. especially for Cu,Ni and up to 99.9%,wiht the mass fraction of less than 0.1×10一remained.For Fe and Al which are always the impurities with high content,the removal efflciency reached up to 99%.For Cr,Mn and Ti etc,the twice removal emciency reached uD tO 99.9%. However,for meta1.1iquating.it is the removal ef右ciency of B and P that is really concemed.The result shows that the once removal e街ciency of B reaches 85%. and the removaI efficiency of wtice removal is more than 99.9%.and the mass fraction of B decreases from 15.4x10-o to less than 0.1×10一.For the removal efifciency of once.1iquating.treatment is about 60%.and the twice removal e ciency reaches uD tO 85%. The result demonstrates that it is feasible for Sn as the medium to rapidly remove B and P via metal-liquating method.In the experiment,the cooling rate is 3.5。C/min.and almost al1 Si recrystallizes out at 850。C for Sn.Si system.The time for Si recrystallization is only 2 h.Even so.the once removal emciency of B nad P reaches 85%and 60%.respectively.By contrast. the maximal operation temperature is only 1 200。C. which is much lower than that of other methods,such as plasma treatment,slagging refining and vacuum refining, etc. 4 Problems linked to metal-liquating method Meta1.1iquating method has the high removal efficiency of metallic impurities in MG.Si.But above al1. hte rapidly effective removal of B and P under low temperature makes the method significant.However,two important problems must be addressed,which are the solid solution of medium and the recovery of waste 1190 meta1. ZHAO Li-xin,et al/Trans.Nonferrous Met.Soc.China 21(2011)1185—1192 in SoG.Si.Therefore.other methods must be introduced to combine with meta1.1iquating method.so that SoG.Si is gained finally and the total cost is reduced further. Firstly,acid leaching should be in仃oduced as the The solid solution of medium is the serious problem irstly.In the Si-rfich side of phase diagrams,either within A1-Si system or Sn-Si system[21,231,there are always a few Sn or A1 existing inside the crystallized Si. For A1.Si system.the maximal content of Alin Si crystal pretreatment in the process.MG—Si contains plenty of impurities.especially Fe and Al with mass fraction of more than 1 O00x 10一.which sometimes even reaches 4 000 ̄10一.Acid leaching can remove almost 95%of metallic impurities.though it is inefiective for B and R During the metal—liquating process, impurities is 1.2%:and for Sn.Si system.the maximal content of Sn in Si is 0.42%.Different from the metal attached to the surface,this part of Sn cannot be removed by acid leaching.So,after most impurities are removed,the newly introduced medium is a problem needed to be redistribute according to the segregation coeficient.The fsolved during the following process,and the dififculty level of which also determines the prospect of the method. Former researches showed that metallic impurities can be easily removed from MG-Si.especially by segregation method.Like other metals,the solid— dissolved medium can be easily removed.For example, as the recrystallized Si is cast again,Sn would segregate at grain boundary like other metal,which can be removed by acid 1caching.Above all-if B and P can be rapidly and effectively removed at lower temperature,the total energy consumption of the process would also be low. During the metal liquating process, Si is recrystallized and separated from metal liquid.Atier purification.the impurities of MG.Si remain in metallic 1iquid.Since the impurities redistribute between medium and Si,the medimu must be the high pure meta1.The usage of high pure metal must increase the cost,so the recovery of the waste meta1 is another problem. Compared with Si,metals commonly have lower melting point and could be easily purified.The segregation method,or say zone refining is the perfect means, especially for Sn,the melting point of which is only 23 1。C.The purity of tin used in the experiments is 99.9%.which can be easily prepared in metallurgical industry.The content ofB and P in Sn is the important index concemed.In our past studies,the super-graviyt segregation was used to rapidly separate trace amount of impurity in meta1.The segregation method can be used to recover hte wasted Sn[24].The recovery of hte waste Sn can reduce hte cost of meta1.1iquating method. 5 Low—temperature metallurgical process of MG-Si purification A1though meta1.1iquating method has the high purification e币ciency,especially for the removal of B and P in MG—Si,the puriyt of Si sitll can not meet the demand Of SOG.Si.For example.the mass fraction of most impurities is near 0.1x10一.but stil1 higher than 0.1 x 1 0。。which is demanded for total content of metals 1ess the content of impurity inside Sn.Si system is.the higher the puriyt of the puriifed Si is.Moreover,after purification,most of the impurities are transferred into the wasted meta1.The high content of impurities would increase the recovery cost of meta1.Acid leaching belongs to hydrometalturgy,and its energy consumption is 1ow.Using acid.1eaching as pretreatment to remove most of impurities can relieve the pressure of purification in the following process. Secondly,unidirectional solidiitcation should be introduced as the last part of the process.As Si crystallizes from metallic liquid.trace amount of metal would solid.dissolve inside Si crystal inevitablV. 0therwise.the trace amount of metallic impurities still remains in recrystallized Si after the metal—liquating puriifcation.For example,the remnants of most metals are near 0.1 x 1 0一.while the remained mass fraction of Fe and Al can reach 5 x 1 0_。’.These remained metallic impurities need to be removed further.Among the studies about metallrugical process.unidirectional solidification is regarded as the last part of the process.In our process, unidirectiona1 solidification is still introduced as the last Dart Of the process to remove the trace amount of remained metals. Based on the above analysis.a low.temperature metallurgical process of MG—Si purification is proposed. Figure 6 shows the flow sheet of the 1ow.temperature metallurgica1 process.The whole process can be divided into three parts:pretreatment,metal—liquating and unidirectional solidification.Within pretreatment.MG.Si is crashed and acid—leached to remove most of the metallic impurities.Within meta1.1iquating.the treated Si particles are melted together with Sn and then recrystallize and separate.The Si crystal is acid.1eached to remove the attached Sn.The recovery of the waste Sn is also included.In this step,the content of B and P is reduced to meet the demand.Witl1in unidirectional solidification,the recrystallized Si is purified by segregation method.确e remaining metallic impurities are gathered and removed,and the puriyt of Si s ̄isfies the demand of SOG.Si.In this step.the top and boRom of Si ingot can be recycled to acid—leaching of second step : 一0日o ∞ ≥ :; ; ∞△- 0∞一力 . ZHAO Li—xin,et al/Trans.Nonferrous Met.Soc.China 21(2011)1185—1192 1191 [2] MORITA K,MIKI Thermodynamics of solra-grade-silicon MG.Si refining[J].Intermetallics,2003,l1(11):1】l1—1117. [3】DIETL J.Hydrometallurgical purification of metallurgical—grades silicon .Solra Cells,l983,1O:145-154. [4] HOFSTETTER J,LELIEVRE J E del cANIzO C,LUQUE A. Acceptable contmaination 1evels in solra grade silicon:From feedstock to solra cell[J]l Materials Science and Engineering B, 2009.159—160:299—304. [5] wu Ji-jun,MA Wen—hui,YANG Bin,DAI Yong-nian,MORITA K. Boron removal from metallurgical rgade silicon by oxidizing refining [J].Transactions ofNonferrous Metals Society ofChina,2009,l9(2): 463-467. [6] KHAT K C P,JOYCE D B,SCHMID F.A simple process to remove boron from metallurgical grade silicon[JJ.Solra Energy Materials and Solar Cells,2002,74(1):77—89. [7] TANAHASHI M,NAKAHIGASHI H,1=f岫DA K,Y MAUCHI C. Removal of boron from metallurgical—grade silicon by applying Ca0一based flux treatment『El//KONGOLI E,ITAGAJ(I K. YAMAUCHI C.SOHN H Y Yazawa Intemational Symposium on Metallurgical and Materials Processing:Principles and Technologies. SoG.Si San Diego,California:TMS,2003:613-624.叫  n Fig.6 Flow sheet of low—temperature metallurgical process [8] KICHIYA S,TOMONORI K,NOBUO S.Removal of boron from metallurgical—grade silicon by applying the plasma rteatment[J]l ISIJ due to its lower content ofB and P International,1992,32:630—634. [9] BENMANSOUR M,ROUSSEAU S,MORVAN D.Effects of the DC bias in a molten silicon bath on its purification and 6 Conclusions hydrogenation by RF thermal plasma[J】l Surface and Coatings Technology,2008,203(7):839—843. 1)Low energy consumption is still the challenge for de WOLF S,SZLUFCIK J,DELANNOY Y'PEIuCHAUD 1. metallurgical process as the special production HABLER C,E1NHAUS R.Solra cells from upgraded metallurgical technology of SOG—Si.Long.time removal of B and P rgade(UMG)and plasma-puriifed UMG multi—crystalline silicon substrates[J].Solar Eneryg Materials and Solra Cells,2002,72(1): under high temperature is the main reason. 49-58. Metal—liquating purification is the potential method YUGE N,ABE M,HANAZAWA K,BABA H,NAKAMURA N, which can rapidly remove them under low temperature. KAI'0 SAKAGUCHI HIⅥ SA S.AR ATANI F.Purification of 2、With Sn as the medium of meta1.1iquating metallrugical—grade silicon up to solra rgade[J].Prog Photovolt:Res method,the calculated segregation coefifcient of B is Appl,2001,9(3):203—209. YUGE N,HANAZAWA K.NISHIKAWA K,TERASHIMA H. less than 0.038.which is far lower than the initial value Removal of phosphorus,aluminum and calcium by evaporation in of 0.8.As Si recrystallizes from Sn.Si system at a molten silicon[J].The Journal ofthe Japan Institute ofMetals,1997, cooling rate of 3.5。C/min,the removal efficiencies of B, 61(10):1086—1093. P and other metals reach more than 85%.60%and 99 9%. .WEI Kui—xian,MA Wen—hui,DAI Yong-nian,YANG Bin,LIU respectively.During metal-liquating process,the Da-chun.WANG Jing—Fu.V cuum distillation refining of formation of compounds between impurity elements and metallrugical grade silicon(I):Thermodynamics on removal of Si is also an important route for impurity remova1.The phosphorus from metallurgical grade silicon[J】.Transactions of Nonferrous Metals Society ofChina,2007.17(s1):sl022-s1025. recrystallized Si is 1arge plate like crystal with less Sn MA Wen-hui,WEI Kui.xian,YANG Bin,YANG Bin。UU Da.chun. attached,which makes it easy to separate Si from Sn DAI Yong—nian.WANG Jing—fu.Vacuum distillation refining of liquid. metallu ca】grade silicon(II):Kinetics on removal of phosphoms 3、Two important problems relative to meta1. from metallurgical grade silicon[J].Transactions of Nonferrous 1iquating purification,the solid.solution of medium and Metals Society ofChina,2007,17(s1):s1026一s1029. CHEN Chao,PANG Ai—SUO.Remova1 method of boron from the recovery of waste metal,were discussed.A polycrystalline silicon.China:101054178A[P].2007.(in Chinese) low—temperature metallurgical process based on YOSHIKAWA t MORITA K.Refining of silicon during its metal—liquating method was proposed.The process solidiifcation from a A1-Si melt[J]_J Crystal Growth,2009,3 lI: contained three parts:pretreatment,metal-liquating and 776-779. Mc CANN M J,WEBER K J.PETRAV1C M.BLAKERS A unidirectional sO1idificatiOn. Boron doping of silicon layers grown by liquid phase epitaxy[J】_ Journa1 ofCrystal Growth.2002,241:45-50. References KnlA K,Y MATSUGU H,WEN C J,K0MIY M H。 讧ADA K.Zone—defined growth of multicrystalline silicon film from [1】 WODITSCH KOCH w Solar grade silicon feedstock supply for metal—silicon solution[J].Solra Eneryg Materials and Solar Cells, PV induslry[J].Solra Energy Materials and Solra Cells,2002,72(1): 2001,65(4):465—47O. l1—26. PETER K,KOPECEK R,F A=T1{P'BUCHER E.ZAHEDI C.Thin 1192 ZHA0 Li.xin,et a ans.Nonfe1TOUS Met.Soc.China 21f20l11 l185-1192 ERIKSSON G HACK JUNG I H,KANG Y B,MELAN( ̄ON J, PELTON A D,ROBELIN C,PETERSEN S.FactSage thermochemical software and databases-Recent developments[J]. Calphad,2009,33(2):295_3 l1. iflm silicon solar cells on upgraded metallurgical silicon substrates prepared by liquid phase epitaxy[J】.Solr Energy Mataerials and Solar Cells,2002,74(2):219—223.[20] YASUJI YUTAKA S.Handbook of physico—chemical properties at high temperatures[M】.Tokyo:The Iron and Steel Institute of Japan,1988:2-3.[23】 MONDOLFO L E Aluminum alloys structure and properties[M】. London:Butterworth,1976:313—315. 『2l1 JACOBS M H G SPENCER P J.A thermodynamic evaluation ofthe [24】 ZHAO L X,GUO Z C,WANG Z,WANG M Y.Removal of system Si-Sn【J].Calphad,1996,2O(1):89—91.『22] BALE C W BELLSLE E,CHARTRAND P'DECTEROV S A,1ow—content impurities from A1 by super-gravity[J].Metal Mater Trns aB,2010,41(3):505—508. 低温净化冶金硅工艺 赵立新 一,王志 ,郭占成 一,李成义 1.中国科学院过程工程研究所湿法冶金清洁生产技术国家工程实验室,北京100190; 2.中国科学院研究生院,北京100049; 3.北京科技大学高效钢铁冶金国家重点实验室,北京100083: 4.中国矿业大学化学与环境工程学院,北京100083 摘要:硼、磷杂质的去除在冶金净化法生产太阳能级多晶硅工艺中耗能最大。金属熔析净化法可以实现冶金硅 在金属液中低温下熔化,而后再结晶净化,是一种可行的低能耗硼磷去除方法。对熔析体系的选择原则进行总结, 筛选出铝、锡和铟金属作为合适的熔析介质。对于Sn.Si体系,1 500 K时硼的分凝系数为0.038,远小于纯硅熔 点的对应值0.8。冶金硅二次熔析净化处理可使硼的质量分数由15x10 降至O.1×10一,而多数金属杂质可一次性 去除至0.1×10 以下。在熔析过程中,杂质和硅生成化合物是主要的杂质去除方式。提出一种以金属熔析法为基 础的低温冶金硅净化工艺。 关键词:金属熔析法;冶金净化法;锡硅体系;太阳能级多晶硅 (Edited by FANG Jing-hua) 

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