薄膜特性對化學機械研磨技術之分析研究

Abstract

在半次微米極大型積體電路(ULSI)的製造中，化學機械研磨(CMP)技術已 成功地達到後段製程中之平坦化需求。此方面的機制與其廣泛地為人所研 究並發表。在本論文中，我們將研究化學機械研磨的巨觀和微觀特性與其 在平坦化之應用。我們從全平表面之介電質膜研磨著手。首先敘述化學機 械研磨技術在過去文獻上的一些理論，再以實驗來探討其巨觀值--平均研 磨速率--在不同研磨條件（如：壓力、轉速、研磨劑濃度、研磨劑供應方 式、和研磨墊狀況等）下之變化，然後進一步探討研磨速率和不同薄膜性 質的關係，並利用這些實驗結果來推測造成研磨速率改變的可能原因和機 制；其次我們再用同樣的方式來研究化學機械研磨技術之微觀值--研磨均 勻度--的特性，以及因薄膜應力造成的晶片彎曲對研磨均勻度的影響，此 外造成研磨不均勻的原因也將探討之。化學機械研磨技術最重要的應用是 對不同結構的不平表面予以平坦化。我們以具有各式線寬和凹溝寬並覆蓋 介電質膜的結構來研磨並探討其平坦化的特性，我們將列出這些不同結構 經過研磨後外觀之改變，而這些改變符合過去文獻中之預測或實驗結果。 最後由圖片顯示經由化學機械研磨後之表面是光滑平坦的，這將證實化學 機械研磨技術應用在積體電路之平坦化製程是絕對可行且令人滿意的。 Implementation of chemical mechanical polishing (CMP) tec- hnology into back-end of the line (BEOL) manufacturing process has proven itself to be the promising planarization method in sub-half micron ULSI fabrication industry. In this thesis, the macroscopic and microscopic characteristics of CMP are studied and then the planarization application is performed and discu- ssed by our experiment. Mean removal rate, the macroscopic characteristics, of CMP is first investigated experimentally with varying polishing p- arameters. Then we will present the correlation between mean removal rate and film properties. Uniformity, the microscopic characteristics, of removal rate is subsequently investigated by varying the foregoing parameters and its variation due to wafer curvature caused by film stress is examined as an exten- sion. The origin which degrades uniformity of CMP is identified Finally, the structure variations of various topography due to polish are shown and they exhibit consistency with the propos- ed planarization behavior. The surface smoothness after CMP is demonstrated. This in turn proves the feasibility of CMP appl- ied to planarization of ULSI process.