銅化學機械研磨中動態腐蝕對陷碟之影響

Abstract

由於銅本身具有良好的導電性和優越的抗電子遷移能力，半導體產業為降低導線間RC Delay的效應，使得銅成為半導體製程中取代鋁的新一代導電材料，因為銅金屬無法進行蝕刻製程，使得化學機械研磨製程的應用更加廣泛。在未來先進製程（20/14nm）甚至到3D IC製程，化學機械研磨仍是表面平坦化不可或缺的一段製程。 一般化學機械研磨分為兩道研磨製程，第一道為金屬銅的移除，第二道為阻障層的移除和陷碟的修復，在第二道研磨製程可修復一些第一道製程所造成稍微輕微的表面缺陷，如銅導線上的刮傷和表面微粒殘留等；因此可得知第一道製程所造成的陷碟跌深度將大大影響第二道製成的修復能力，所以陷碟深度的控制將是化學機械研磨製程的一大課題。 陷碟的產生主要來自研磨過程中兩大因素：機械作用力和化學作用力。機械力的影響主要來自研磨機台、研磨墊和研磨顆粒，因此可藉由機台參數之調整來控制機械力的影響。本研究將探討化學作用力與陷碟效應之間的關聯性，在化學機械研磨過程中，晶圓、研磨液和研磨墊間的微觀世界是很難明確的定義期間發生的各種腐蝕作用（八種腐蝕型態）。因此，本實驗將所有腐蝕型態濃縮定義成兩大類：靜態腐蝕和動態腐蝕，並利用研磨機台參數設定和量測儀器來達成靜態腐蝕和動態腐蝕的實驗設計和數據量測。 為避免實驗結果是因特定情況所產生，研究將搭配不同pH值區間的研磨液，和固定pH值之研磨液並添加不同腐蝕抑制劑，這些調配而成的研磨液利用機台進行研磨，並利用儀器分析本研究中設定的四種指標：研磨率、電化學儀器分析腐蝕電流、靜態腐蝕和動態腐蝕，探討各個指標與陷碟效應之間是否有關聯性，並了解在排除機械作用力之後陷碟效應產生的主要因素為何，能否運用這些指標來預測陷碟產生率和作腐蝕抑制劑的篩選。

According to copper is with nice electrical conductivity and better ability to reduce electron migration, it has been utilized to replace aluminum as a new generation of conductive material in the semiconductor manufacturing process by reducing the effects of RC Delay which cause between conducted wires in the semiconductor industry. In the future, semiconductor manufacturing advanced process (20/14nm) and even to the 3D IC manufacturing process, chemical mechanical polishing is an integral process of the surface planarization . The process of chemical mechanical polishing are generally divided into two polishing process. The first process is the removal of copper, and the second is the barrier layer removed and the dishing repair. It means the second polishing process can repair the surface with some slightly defects such as scratches on the copper wire and the particle residues on the surface, which caused by the first process. Consequently, the depth of dishing which made by the first process will greatly affect the repair capacity made by the second polishing. In addition to this , the dishing control on the depth of dishing is a major issue in the chemical mechanical polishing process. The dishing is mainly produced and impacted by two major factors in the polishing process; one of the factors is the mechanical force and the other is the chemical interaction. For the mechanical force, the major impact of mechanical force is from the polishing machine, polishing pad and abrasive particles, and therefore the impact could be adjusted by machine parameters to control the influence of mechanical force. In terms of the factor of the chemical interaction, this study investigated the correlation between the chemical interaction and the dishing performing in the chemical mechanical polishing process. In the microscopic world, it is difficult to define specifically various corrosion (8 kinds of corrosion patterns) are occurred by the reaction between the wafer, the polishing solution or the polishing pad during the chemical mechanical polishing process. Accordingly, this study simplified the definition of all the corrosion types as two categories which are static corrosion and dynamic corrosion. Moreover, the experiments of the static corrosion and dynamic corrosion are completed by experimental design and data measurements which are applying the polishing machine parameter setting and measuring instruments. Experimental slurry are designed to process with the different pH and adjusting various corrosion inhibitors in the fixed pH, which are considered to process the polishing and gain the data to be analyzed by using the analysis instrument. To research and discuss the relation between the dishing behavior and four indexes : removal rate, electrochemical - corrosion current, static corrosion and dynamic corrosion. In this study, it is also discussed if any one of these indexes could be the key to anticipate the dishing behavior and usefully select corrosion inhibitor excluding the effect of mechanical force.