湿法去除N型硅硼扩散过程形成的富硼层

Wet-chemical Removal of Boron-rich Surface Layer on Boron Diffused Silicon

硼扩散被广泛应用于n型硅基的p-n结制结工艺,然而硼扩散难免会在硅片表面形成一层很薄的的富硼层,该层由于富集无活性硼原子会严重影响电池性能。本研究制备HF-HNO3化学腐蚀液来去除富硼层,采用该方法去除富硼层后的硅片少子寿命从26.829μs增加到69.106μs;WCT-120测得一个光照下Voc从610mv增加到了625mv,发射极饱和电流密度显著降低;去除富硼层后的方块电阻均匀性表现良好,甚至比采用传统后氧化法更具优势。虽然反射率有细微增加,但是对于镀完氮化硅减反膜后腐蚀所带来的反射率升高只有0.13%,因此,认为该方法可以成功应用到富硼层的去除中。

Boron diffusion is widely used to create p-n junction in n-type silicon wafers. But it is commonly associated with an undesirable growth of a thin boron-rich layer （BRL） on the surface. This layer has a significant negative influence on the efficiency of n-type silicon solar cells due to the richness of inactive boron atoms. In our study, The BRL was removed by wet-chemical etching with etchant solution containing the low-concentration of HF-HNO3. Although the etching process slightly increases the average reflectivity of the samples from 14. 7% to 15.9%, the reflectivity （5.46%） after PECVD SiNx AR coating is still close to that （5.34%） without etching, indication no damage by the etching to the pyramid structure. The removal of BRL by this method increases the minority carrier lifetime from 26. 829μs to 69. 106μs, and improves the implied- Voc to 625 mV without passivation. Moreover, it has almost no negative impact on the uniformity of sheet resistance. This wet-chemical etching method can thus be successfully applied to remove the BRL.