6H-SiC单晶片划痕形貌与残余应力研究

Morphology and Residual Stress of 6H-SiC Single Crystal Wafer Induced by Scratching

为了研究6H-SiC单晶片在(0001)晶面C面划擦过程中材料的损伤机理,首先通过微纳米划痕系统划擦单晶片,得到不同载荷作用下沿不同晶向的划痕,再通过摩擦力传感器、显微镜以及激光Raman光谱检测不同晶向划痕的摩擦系数、表面形貌以及残余应力。结果表明:6H-Si C单晶片沿不同晶向划擦后的摩擦系数基本稳定在0.185~0.240;单晶片在不同载荷作用下的划擦过程中沿[1210]晶向出现了不同程度的损伤,随着载荷的增加单晶片从塑性去除逐渐转变为脆性去除,划痕中心的凹陷与两侧堆积现象逐渐加剧;当划痕加载力小于10.7 N时,材料处于塑性去除模式,残余应力主要呈现残余压应力,局部有较小的残余拉应力;当划痕加载力大于10.7N时,材料从塑性去除向脆性去除转变,在14.8N时转变为脆性去除模式,划痕底部残余拉应力逐渐增大,以残余拉应力为主,但在划痕两侧堆积处呈现较大残余压应力。该研究可为6H-SiC单晶片精密超精密研磨加工损伤机理的研究提供理论支持。

In order to clarify the damage mechanism of 6H-SiC single crystal wafer in the scratching process of (0001) crystal surface, the SiC wafer was scratched by a micro-nanoscale scratch system. The scratches along different crystal directions under different loads were analyzed. The friction coefficient, surface morphology and residual stress of the scratches along different crystal directions were determined by a friction sensor, microscope and laser Raman spectroscope. The results show that the friction coefficient of SiC wafer is basically stable at 0.185-0.240 after scratching along different crystal directions. In the scratch process of SiC wafer under different loads, different damage degrees occur along [1210] crystal direction. The material mode gradually changes from plastic removal mode to brittle removal mode, and the groove in the center and the accumulations on both sides of the scratch gradually intensify with the increase of load. The material is removed by plastic removal mode, and the residual stress mainly presents the residual compressive stress with a small residual tensile stress locally when the scratch load is less than 10.7 N. The material removal mode gradually changes from plastic removal to brittle removal, and then to brittle removal mode at 14.8 N when the scratch load is larger than 10.7 N. The residual tensile stress at the bottom of the scratch gradually increases, mainly residual tensile stress, but there is a large residual compressive stress at the accumulation on both sides of the scratch. This study could provide a theoretical support for the research of damage mechanism of SiC wafer precision ultra-precision machining.