不同硅晶面指数上的类倒金字塔结构研究与分析

Different silicon crystal face index of inverted pyramid structure

晶体硅作为一种重要的半导体材料,在集成电路、太阳能电池等方面具有广泛的应用.基于各向异性的刻蚀方法,不同晶面指数的硅都可以在表面形成由{111}晶面族组成的正/倒金字塔.本文基于{111}晶面族与(abc)晶面相交构成类倒金字塔结构的特性,建立了硅的晶面指数(abc)与所形成的类倒金字塔结构的数学模型.将硅的晶面指数(abc)分成0ab <c, 0a <b=c, a=b=c三种情况进行讨论,分别得到不同晶面指数的类倒金字塔结构.实验结果的扫描电子显微镜图证实了理论计算的准确性.晶面指数与类倒金字塔结构具有一一对应的关系,因此可以根据各向异性刻蚀后的类倒金字塔结构,进行硅的晶面指数进行检测.

As a kind of important semiconductor material, crystalline silicon has vast applications in many industries, such as integrated circuits and solar cells. With anisotropic etching method, including alkali etching and copper assisted catalytic etching, pyramid or inverted pyramid structure on the surface of silicon can be formed due to different crystal face indices of the silicon wafer, which is especially for multi-crystalline silicon wafers, because there are many different crystal faces on the surface. The proportion of different crystal faces has a high reference value for controlling the quality of multi-crystalline silicon. In this paper, the mathematical model of the inverted pyramid structure is established by making use of the relationship between the silicon crystal indices（abc） and {111} crystal plane. The inverted pyramid structures with different crystal face index（abc） values are divided into three possible cases for discussion, which are0≤ a ≤b 〈c, 0 ≤a〈 b = c and a = b = c. The inverted pyramid structure on which the crystal face index（abc） satisfies 0 ≤a ≤b 〈c is of a pentahedron composed of five points and has a quadrangular cross section. The inverted pyramid structure in which the crystal face index（abc） satisfies 0 ≤a 〈b = c is of a heptahedron composed of eight points and has a hexagonal cross section. The inverted pyramid structure whose crystal plane index（abc） satisfies a = b = c = 1 is also of a heptahedron and has a hexagonal cross section but is composed of nine points. In general, the cross section of the（111） crystal face inverted pyramid is similar to an equilateral triangle because three of the edges are easier to etch away. The scanning electron microscopy image results show that the crystal indices are（100）,（110） and（111）, thereby demonstrating the correctness of the theoretical calculations. The index of crystal face has a one-to-one correspondence relationship with the inverted pyramid structure. Therefore, according to the inverted pyramid structure after anisotropic etching, we can measure the index of Si crystal face.