Synergetic effects of wafer rigidity and retaining-ring parameters on contact stress uniformity in chemical mechanical planarization
Synergetic effects of wafer rigidity and retaining-ring parameters on contact stress uniformity in chemical mechanical planarization
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DOI：
10.1007/s00170-011-3215-8
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发表时间：
2011-03
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影响因子：
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通讯作者：
Ian Hu;Tian-Shiang Yang;Kuo-Shen Chen
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文献类型：
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作者：
Ian Hu;Tian-Shiang Yang;Kuo-Shen Chen
在这里，我们使用二维流体膜润滑和接触力学模型来计算接触应力和流体（即，在化学机械平坦化（CMP）中晶片-垫界面上的浆料）压力分布。特别地，晶片的有效刚度（由晶片载体结构确定）、保持环宽度及其背压被视为设计参数。目的是研究这些参数对接触应力均匀性的协同影响，接触应力均匀性直接影响到晶片表面材料去除率的空间均匀性。我们的数值计算结果表明，对于一个给定的晶片刚度，可以选择保持环的宽度和背压，以尽量减少接触应力的不均匀性（NU）。而且，所得的最小NU随着有效晶片刚性而减小，这表明使用软（例如，浮动型）晶片载体。此外，对于软晶片载体，证明了使用多区域晶片背压分布在降低NU方面甚至更有效。
Here we use two-dimensional models of fluid film lubrication and contact mechanics to calculate the contact stress and fluid (i.e., slurry) pressure distributions on the wafer–pad interface in chemical mechanical planarization (CMP). In particular, the effective rigidity of the wafer (determined by the wafer carrier structure), the retaining-ring width and its back pressure are taken to be the design parameters. The purpose is to study the synergetic effects of such parameters on the contact stress uniformity, which directly affects the spatial uniformity of the material removal rate on the wafer surface. Our numerical results indicate that, for a given wafer rigidity, one may choose the retaining-ring width and back pressure to minimize the contact stress non-uniformity (NU). Also, the resulting minimum NU decreases with the effective wafer rigidity, suggesting that it is beneficial to use a soft (e.g., floating-type) wafer carrier. Moreover, for a soft wafer carrier, it is demonstrated that using a multi-zone wafer-back pressure profile is even more effective in reducing NU.