多孔硅对单晶硅少子寿命影响状况的研究

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。

Effect of the porous silicon on the minority carrier lifetime of monocrystalline silicon

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 layers in the case of the different etching time,which was characterized by SEM,and tested the minority carrier lifetime by WT-2000 μ-PCD.It was found that compared with the other samples,the surface morphology of porous silicon was best under the condition of etching 11min in the same solution ratio,as well as the porosity was largest.We noticed a significant improvement for the minority carrier lifetime at 850℃ for 150min.The improvement level of the minority carrier lifetime was different for the etching time.The sample of etching 11min 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 silicon/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 exceeded them of initial crystalline silicon,which was beneficial to the migration for metallic impurities from the bulk to the PS layer.