掺Sn改善UMG-Si铸锭中铁对少子寿命的影响作用

Improvement of the Minority Carrier Lifetime of Fe Contaminated UMG-Si Ingot by Sn Doping

为削弱有害杂质元素Fe对多晶硅性能的影响,采用Si-Sn微合金化的途径,研究Sn对不同Fe污染程度时提纯多晶硅(UMG-Si)定向凝固后少子寿命的变化。掺入30ppmw或100ppmw Fe杂质后,在Sn元素含量分别为0ppmw、15ppmw、30ppmw、50ppmw时,测试定向凝固多晶硅少子寿命变化。随着Fe含量增加硅锭少子寿命减少,初始杂质Fe含量为0ppmw、30ppmw、100ppmw时,硅锭中部平均少子寿命分别为0.81μs、0.52μs和0.40μs。掺入适量的Sn元素,能有效削弱杂质Fe的危害,提高少子寿命。当初始Fe含量为30ppmw时,掺入Sn为15ppmw、30ppmw后,硅锭中部平均少子寿命提高23%、25%。当Fe含量为100ppmw时,掺入Sn含量为15ppmw、30ppmw、50ppmw后,少子寿命可提高40%、50%、40%。原子半径比Si大的Sn原子引入晶格应力,抑制间隙原子Fe成核、阻碍Fe扩散,有效减少杂质Fe的危害。

In order to eliminate the effect of harmful impurity iron on silicon ingot properties, this research studied the influence of Sn doping on minority carrier lifetime （MCL） of iron contaminated directional solidified upgraded metallic grade silicon （UMG-Si）. The contents of Fe doping were 30 ppmw and 100 ppmw, while the contents of Sn were 0 ppmw, 15 ppmw, 30 ppmw and 50 ppmw. The MCL was reduced with the increase of Fe content. When the contents of Fe were 0 ppmw, 30 ppmw, 100 ppmw, the average MCLs of ingots center were 0. 81 μs, 0. 52 μs, 0. 40 μs, respectively. Sn can reduce the harmful effect of Fe and improve the MCL. When the contents of Sn were 15 ppmw and 30 ppmw, the MCL increased by 23% and 25% with 30 ppmw Fe addition. And when the contents of Sn were 15 ppmw, 30 ppmw and 50 ppmw, the MCL increased by 40%, 50% and 40% with 100 ppmw Fe addition. The suppression of the harmful effect of Fe on the MCL of the UMG-Si ingots is attributed to lattice strain induced by the larger atomic radius of Sn.