低介電常數材料特性分析與研究

Abstract

隨著元件尺吋縮小，元件速度主要受限於訊號在金屬連線間傳送的時 間延遲， 為了改善此問題，本論文主要針對利用低介電常數材質來 降低金屬連線中的電 容值。本篇論文共研究三種低介電常數材料， 包括摻氟二氧化矽(SiOF)，與旋 轉式塗佈介電材質(SOG)。在摻氟二 氧化矽方面，此種介電質是最容易應用在 業界上的，但是許多論文 發現摻氟二氧化矽易吸收水氣，使介電常數值上升。 因此本論文利 用NH3電漿處理使摻氟二氧化矽表面氮化，穩定摻氟二氧化矽的 介 電常數。在旋轉式塗佈介電材質(SOG)方面，現已發展出介電常數小於3的 SOG 材質，此低電介常數SOG材質極為可能成為將來應用的主流，本篇 論文研究二種 不同結構的SOG，一為含碳氫鍵結的有機SOG，另一則為 含氫鍵結的無機SOG﹐此 二種的介電常數在理想狀態下約為2.7, 內容 主要針對其基本特性與熱穩定性做 詳細的探討，結論發現碳氫鍵結 SOG的熱穩定性較好，含氫鍵結的SOG則必須將製 程的溫度，時間控制 恰當，才可得到較低的介電常數值。 Interconnect delay is a performance-liming factor for ULSI circuits when feature size is scaled into the deep submicron region. Using low dielectric constant material for the interlayer insulator is an effective way to solve the problem. We study three kinds of low dielectric constant material, including fluorine doped oxide( SiOF), methylsilsesquioxane spin on polymer and hydrogen silsesquioxane spin on glass. PECVD fluorine doped oxide( SiOF) is a popular way to reduce the dielectric constant, but it is reported that SiOF film with high level of fluorine incorporation have been shown to be unstable because of moisture absorption. In this work, NH3 plasma post-treatment are applied to as-deposited SiOF films. Moisture resistance and dielectric constant stability are investigated. We found that NH3 plasma post-treatment is quite efficient to enhance the capability of moisture absorption resistance of SiOF. In addition, two novel SOG material with permittivity lower than silicon dioxide interlevel dielectric have been developed. Those SOG can offer a k of less than 3.0. Two kinds of low k SOG are investigated, one is organic material-methylsilsesquioxane, the other is inorganic-hydrogen silsesquioxane. These spin on glass can offer low dielectric constant (~2.7) on the optimal conditions. The intrinsic properties and thermal stability of these spin on glass are investigated. We found that the thermal stability of methylsilsesquioxane is good because of Si-C bone in the film, and the thermal processing of hydrogen silsesquioxaone must be done carefully to attain the lowest dielectric constant.