反转法消除硅片重力附加变形适用性研究

Research on the Suitability of Inverting Method to Cancel Gravity-induced Deflection of Wafers

建立了计算硅片重力附加变形的有限元模型,模型包含硅片残余应力的影响。通过有限元与实验方法研究了反转法对抛光与磨削加工硅片适用性。结果表明,反转法适用于抛光硅片,有限元与反转法所得重力附加变形差值小于1μm;对#5000砂轮磨削的300 mm直径394μm厚度硅片,硅片残余应力使反转前后重力附加变形不再相同,误差超过最大重力附加变形值的5%;对#2000砂轮磨削的200 mm直径194μm厚度硅片,残余应力超过临界值,硅片变形发生分岔,硅片自由面形与重力附加变形不再符合叠加关系,反转法不再适用。

A finite element model( FEM) was presented to calculate the GIDs of wafers. The model includes the effect of initial stress. The suitability of the inverting method was discussed for wafers after polishing and grinding by the model and experiments. The results show that the method is suitable for polished wafers. The difference between the GIDs obtained using the model and the inverting method is less than 1 μm. The error is larger than 5% of the maximum GID value for the 300 mm diameter and 394μm thickness wafer ground by #5000 diamond wheel. For the 200 mm diameter and 194 μm thickness wafer ground by #2000 diamond wheel bifurcation occurs as the residual stress is larger than the critical value. The method can not be used since the wafer flatness and the GID could not be superposed.