多孔硅对单晶硅少子寿命影响状况的研究

摘要

以p型单晶硅片为研究对象,在单晶硅片表面采用化学腐蚀方法制备多孔硅层,通过实验选取制备多孔硅的最佳工艺条件,采用SEM观察多孔硅表面形貌,以及用微波光电导法测试少子寿命的变化情况。结果表明,在相同的腐蚀溶液配比条件下腐蚀11min得到的多孔硅层的表面形貌最好,孔隙率最大。在850℃下热处理150min时样品少子寿命的提高达到最大,不同腐蚀时间的样品少子寿命提高程度不同,腐蚀11min的样品少子寿命提高最大,约有10%左右。多孔层的形成伴随着弹性机械应力的出现,引起多孔层-硅基底界面处产生弹性变形,这有利于缺陷和金属杂质在界面处富集。另外,多孔硅仍具有晶体结构,但其表面方向上的晶格参数要比初始硅的晶格参数大,也有利于金属杂质向多孔层迁移。%P-type monocrystalline silicon （mc-Si） Was used as the starting material. Porous silicon （PS） layer was formed on the front surface of （mc-Si） silicon by chemical etching. We obtained the different porous silicon lay- ers in the case of the different etching time, which was characterized by SEM, and tested the minority carrier li- fetime by WT-2000/~-PCD. It was ft）und that compared with the other samples, the surface morphology of por- ous silicon was best under the condition of etching 11rain in the same solution ratio, as well as the porosity was largest. We noticed a significant improvement for the minority carrier lifetime at 850~C for 150min. The im- provement level of the minority carrier lifetime was different for the etching time. The sample of etching 11rain was more efficient than other samples, up to 10~. It is well known that the porous silicon layer formation was accompanied by the appearance of elastic mechanical stress, which caused the elastic deformation in porous sili- con/silicon interface. These interfaces were the favorable sites for defects and metallic impurities. In addition, PS had a crystalline structure like silicon substrate, but its crystal lattice parameters in surface direction excee- ded them of initial crystalline silicon, which was beneficial to the migration for metallic impurities from the bulk to the PS layer.