在半導體製程中，化學機械平坦化製程扮演著使積體電路內部連接層高度平坦化的角色。在實際製程中，通常會用一剛性較強的晶圓扣環固定住晶圓，而晶圓扣環的存在可能影響晶圓與研磨墊間接觸應力之均勻度，進而影響材料移除率之均勻度。為了具體分析晶圓扣環對於接觸應力均勻度的影響，我們利用潤滑理論和接觸力學建立二維理論模型，以計算晶圓附加晶圓扣環情況下之接觸應力、研磨液壓力分佈，並且探討晶圓扣環的背壓與尺寸等參數，對於接觸應力均勻度、研磨墊與粗糙峰變形量、等效液膜厚度、研磨液壓力以及研磨液之體積流率的影響。結果發現附加晶圓扣環可使得晶圓邊緣部份的接觸應力下降，從而提高接觸應力之均勻度，但是卻會增加研磨液通過晶圓與晶圓扣環時的流阻，進而讓研磨液流率降低。根據參數研究結果，我們可以進一步找出可提升接觸應力均勻度的最佳化參數設定。

　　Chemical mechanical planarization (CMP) has played an enabling role in achieving near-perfect planarity of interconnection and metal layers in ultralarge scale integrated (ULSI) semiconductor devices. In practice, there is a retaining ring that keeps the wafer in place; its presence may affect the contact stress uniformity on the wafer-pad interface, which is an important factor determining the material removal rate (MRR) uniformity. To understand the effects of the presence of a retaining ring on the contact stress uniformity, here we use two-dimensional lubrication theory and contact mechanics model to calculate the contact stress and fluid pressure distributions on the wafer-pad interface, and then examine the effects of retaining ring back pressure and size on the contact stress uniformity. Our numerical results indicate that the presence of a retaining ring decreases the contact stress at the wafer edge, and hence improves the contact stress uniformity. However, it also increases the slurry flow resistance and therefore decreases the volumetric flow rate of the slurry. Through systematic parameter studies, we also deduce the optimal parameter settings that minimize the contact stress uniformity.

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