图形化Si基Ge薄膜热应变的有限元分析

Thermal Strain Finite-element Analysis in Ge Film on Patterned Si Substrate

利用有限元方法模拟了图形化Si衬底上外延Ge薄膜的热失配应变,研究了薄膜内部以及表面的应变分布情况,分析了应变与薄膜厚度、衬底尺寸的变化关系.结果表明,热失配应变在异质结构的界面处最大,沿外延层生长方向递减;在薄膜表面,中心区域应变最大,由中心到边缘逐渐减小,边缘发生突变,急剧减小;不同的膜厚下,薄膜表面应变分布规律相同,并且薄膜越厚,应变越小;图形衬底单元的尺寸对薄膜应变有较大的影响,当衬底厚度在6μm以内,宽度在10μm以内时,更有利于薄膜应变的释放.

Film/substrate heterostructure based on patterned substrate has advantages in strain release and dislocation capture,and capture,and is widely used in microelectronics and optoelectronics. Residual stress in heterostructure leads to negative effects on the performance of the material and devices. Finite element method is used in this paper to simulate thermal mismatch strain in pitaxiat film on patterned Si substrate. Strain distribution is analyzed which is from the inside out of the film and the strain against film thickness and substrate size are obtained. The results indicate that maximal thermal v^srqgtch appears in the interface of film/substrate heterostructure,and the thermal mismatch is smaller from the interfase to the epitaxial film surface;strain decreases gradually from center to edge and suddenly drops on the edge ; strain distribution of the film is in the same rule with different thickness and thin film means small strain; size of the substrate has great influence on film strain,strain release of the epitaxial film can be accepted when the substrate thickness and width are 6 μm and 10 μm respectively.