新型SOG的特性及其在次微米平坦化技術的應用

Abstract

為開發更小間距的超大型積體電路後段製程平坦化技術, 本實驗使用新型 的SOG.首先,我們分析此材料的特性, 以了解實際應用時的參數, 此特性 包括厚度及均勻度與轉速的關係, 鏈結反應後收縮率及均勻度與轉速的關 係, 蝕刻率與氧氣流量的關係, 蝕刻率的選擇性等.此外,紅外光譜分析, 熱分析, 熱重分析等技術亦被用來探討此一新型SOG 的物性與化性.為了 解其填充小間距及平坦化的能力, 此材料被用在小間隙上. 許多方法被用 來解決 SOG與PECVD 間裂縫的問題, 包括改變PECVD 本身材質, 改變 SOG 覆蓋前的條件, 改變PECVD 膜的應力, 及改變SOG 覆蓋的程式, 以得到更 好的小間隙填充及平坦化的結果.最後, 將此材料應用在 256 Kbyte SRAM 上,得到84% 的良率.此外,其在作後段絕緣層整合上搭配 Si-rich PECVD 可以得到非常平坦的面. 由於此新型 SOG只需覆蓋兩次, 比目前所 用的少覆蓋一次,因此更適合大量生產產的需求. When the line width of VLSI backend processes reduces to sub- half micron regime, a new siloxane-type SOG is demanded. In this work, AS314 from Allied Signal Inc. was investigated. Material characteristics, such as thickness and uniformity vs. spin speed, shrinkage and uniformity vs. spin speed, etch rate vs. O2 flow rate, and etch selectivity vs. O2 flow rate were evaluated. Four- ier Transform Infra-red (FTIR) spectroscopy, differential scanning calorimeter (DSC) thermal analysis,and thermogravimetric analyzer (TGA) were employed to study the chemical and physical properties of AS314. To investigate the gap-filling and planarization capabilities of AS314, a series of experiments were performed on patterned wafers with various gaps down to 0.4痠 in dimension. Several meth -ods were proposed to solve the problem of crack formation bet- ween SOG and PECVD oxide for narrow gaps.The effect of Si content in PECVD oxide, water absorption of PECVD oxide, surface condi- tions of PECVD oxide, surface tension of PECVD oxide, and coating procedures on the results of SOG coating were evaluated. Application of AS314 to 256Kbyte SRAM was made. Yield as high as 84% was achieved. In addition, integration of interlayer diele -ctric film was investigated. AS314, together with Si-rich PECVD oxide, formed a near-perfect planar topography. Comparing double- coat AS314 with triple-coat AS111 process, the former saves 40 minutes per lot in production, which is desirable for manufactur- ing.