基于负性光刻胶掩膜的湿法多晶硅制绒

Texturization of Polycrystalline Silicon Wafers by Wet Etching Process Using Negative Photoresist Masks

提出了一种用于大规模多晶硅太阳能电池生产的制绒工艺,采用负性光刻胶作为湿法刻蚀的掩膜,制备蜂巢状低反射率绒面。通过研究氢氟酸/硝酸溶液中各向同性刻蚀时腐蚀坑的形成过程,发现随着刻蚀时间的增加,在掩膜图形的开孔下逐渐形成六方分布的球面形状的腐蚀坑,腐蚀坑的深径比(深度/开孔直径)出现先上升然后下降的趋势。同理论计算值对比发现,随着刻蚀时间增加,掩膜和硅片的附着紧密性及掩膜的阻挡效应降低,酸液可能渗入了掩膜和硅片的界面,横向刻蚀速度快速上升,降低了深径比,导致实际的反射率高于理论计算值。尽管如此,本文还是成功制备了孔径15微米的蜂巢状绒面,反射率达到了22.9%。

An approach of texturization for industrial scale fabrication of muhicrystalline silicon （mc-Si） solar cells was reported. Using negative photoresist mask and wet etching method, a honeycomb textured surface with low reflectivity was obtained. Through the study of above isotropic etching process in aqueous solutions of HNO3 and HF, it is found that the spherical pits with hexagonal distribution are formed and also it is observed that with increasing etching time, the ratio of depth to aperture of etching pits （h/D） rises first and then fails. Comparing with that ratio calculated by the numerical model, it is observed that as the etching time increases, the average measurement of h/D becomes much lower than calculated, leading to a higher reflectivity of textured surface of mc-Si. This result suggests that the blocking effect of photoresist mask gradually weakens with the etching time. The weak adhesion can cause the acid infiltrating into the interface between photoresist mask and Si wafer, which leads to a rapidly growing horizontal etching rate and therefore the fall of h/D value. Although the proposed approach of texturization did not achieve the ideal results, the honeycomb textured surface with the pitch of 15μm was fabricated successively and the lowest average reflectivity of 22.9% was obtained.