晶圆化学机械抛光中保持环压力的有限元分析

Calculating Suitable Pressure on Retaining Ring in Chemical Mechanical Polishing(CMP) of Wafer

在集成电路(IC)行业中,化学机械抛光(CMP)是获得全局平坦化的技术。随着晶圆直径的增加,在CMP加工过程中,晶圆边缘容易出现"过磨(over-grinding)"现象,降低了平坦度和晶圆利用率。在晶圆外部施加保持环可以把晶圆中心处和边缘处的抛光垫压平到一致高度,克服晶圆边缘的"过磨"现象。由此说明,保持环上施加的压力起着至关重要的作用。在实际中,晶圆和CMP工艺成本高,依靠实验探索CMP加工后晶圆边缘效应的规律不可行,所以保持环压力不宜通过实验方法确定,需要借助其它方法预测该压力。文中采用有限元模拟的方法分析保持环压力,得出了保持环压力与晶圆压力比值的最优值,并且研究了晶圆与保持环的间隙对最优压力的影响规律。针对不同CMP工艺,保持环压力能够迅速确定,从而提高晶圆抛光质量及利用率,降低晶圆制造成本。

We present a FEM method for forecasting the suitable pressure on the retaining ring,which is critical in manufacturing good quality wafers.In the full paper,we explain our method and its calculation results in some detail.In this abstract,we just add some pertinent remarks to listing the two topics of explanation.The first topic is： the establishment of FEM model.In this topic,we establish the axisymmetrical FEM model for the CMP process,as shown in Fig.2 in the full paper.The second topic is： simulation results.In this topic,we use the wafer with the diameter of 200 mm and the optimum value of the pressure on the wafer equal to 0.069 MPa,and use 0.075 mm as the gap between the wafer and the retaining ring.At this time,the optimal pressure on the retaining ring is 0.158 7 MPa.