Microbridge method determining the mechanical properties of low stress LPCVD silicon nitride film and its error analysis

Abstract

用微机械悬桥法研究低应力氮化硅薄膜的力学性能。对符合弹性验则的微桥进行测试 ,在考虑衬底变形的基础上 ,利用最小二乘法对其载荷—挠度曲线进行拟合 ,得到低应力lowpressurechemicalvapourdeposited (LPCVD)氮化硅的弹性模量为 3 14 .0GPa± 2 9.2GPa ,残余应力为 2 65 .0MPa± 3 4.1MPa。探讨梯形横截面对弯曲强度计算和破坏发生位置的影响 ,得到低应力氮化硅的弯曲强度为 6.9GPa± 1.1GPa。对微桥法测量误差的分析表明 ,衬底变形、微桥长度和厚度的测量精度对最终力学特性的拟合结果影响最大 The mechanical properties of MEMS materials have attracted many efforts during these years. Several methods were developed, yet the measured results varied. The mechanical properties of low stress low pressure chemical vapour deposited (LPCVD) Silicon nitride film was investigated by the microbridge method using a wedge tip under the nanoindentor. An elastic checking criterion was proposed and carried out to screen out unelastic microbridge samples. With the consideration of the substrate deformation and cross-section of the microbridge, theoretical analysis is conducted on the microbridge deflection. From the least square fitting process, the elastic modulus is evaluated to be 314.0?GPa±29.2?GPa, while the residual stress and the bending strength are 265.0?MPa±34.1?MPa and 6.9?GPa±1.1?GPa, respectively. The error analysis of the microbridge method shows that the substrate deformation, the length and thickness measurement of the micro bridge influence the regressed results greatly. 还原