护环对硅片抛光表面压强分布和轮廓的影响

Effect of retaining ring on pressure distribution and profile of polishing wafer surface

为了获得单晶硅片化学机械抛光过程中护环对接触压强分布的影响规律，从有护环化学机械抛光实际出发，建立了抛光过程的接触力学模型和边界条件，利用有限元法对有护环抛光接触状态时的接触压强分布进行了计算和分析，并利用抛光实验对计算获得结果进行了验证。获得了硅片与抛光垫间的接触表面压强分布形态，以及护环几何参数对压强分布的影响规律。确定了护环抛光接触压强的分布也存在不均匀性，而且在硅片外径邻域内接触压强最大，并导致被加工硅片产生平面度误差和塌边。结果表明，当选择护环与硅片的间隙为0，负载比为2．5～3．5，以及适当的护环宽度时，可以改善接触压强分布的均匀性。

In order to study the effect of a retaining ring on the pressure distribution of siliconwafter surface during the processes of Chemical Mechanical Polishing （CMP）, the mechanism model and boundary conditions of CMP processes were set up based on the practices of CMP with a retaining ring. Then, the contact pressure distribution was calculated and analyzed in polishing experiments using ANSYS. The contact pressure distribution between silicon wafer and polishing pad and the effect of the retaining ring on it were obtained. Analytical results indicate that the contact pressure distribu- tion is nonuniform and it is maximal on the borderline of silicon wafer, which generates the flatness errors and the subsiding of the outside edge of wafer. Experimental results suggest that the contact pressure distribution uniformity can be improved when the clearance between the ring and wafer is 0, the load ratios of the ring to wafer are 2.5-3.5 and the ring widths are chosen properly.