低介電常數材料在積體電路上之應用研究

Abstract

隨著元件尺寸縮小，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，低介電常數材料的使用成為必要的選擇。本論文主要針對如何改進利用低介電常數材質時容易出現的製程整合與銅導線搭配時介面的問題。本篇論文研究的低介電常數材料Hybrid-Organic-Siloxane-Polymer(HOSP)為一種旋轉式塗佈介電材質。其本身為含矽氧、矽碳、矽氫與碳氫鍵結的有機旋塗式低介電材質。在旋塗的過程中，富良好的流動性，因此，有極佳的局部平坦化能力，並能填入高深寬比的孔洞中，且因有機官能基之存在而具低介電常數。此材料的介電常數在理想狀態下約為2.5。然而，在積體電路的製造技術中，光阻（photoresist）的去除，常是利用氧電漿處理方式來將光阻中的碳氫成分分解，達到光阻灰化（ashing）的目的，但氧電漿製程同時會破壞具有有機成分低介電材料HOSP的特性，而使得薄膜漏電流上升，介電常數也隨之增加。本論文內容主要針對其基本特性、熱穩定性、各種電漿處理後的特性與對氧電漿與銅金屬接觸的效應做詳細的探討與分析。結果發現此利用電漿處理之後，可提升HOSP薄膜抗氧電漿、抗銅擴散的能力；使得漏電流與介電常數能維持在相當低的結果；同時並能有效強化HOSP薄膜的熱穩定性。經過電漿後續處理，低介電常數材料- HOSP 在現今銅金屬連線製程整合應用上將具有極大潛力。

Interconnect delay is a performance-limiting factor for ULSI circuits when feature size is scaled to the deep submicron region. Using low dielectric constant materials for the interlayer insulator is an effective way to solve this problem. We have studied a low dielectric constant material, the HOSP spin-on polymer, which has a permittivity lower than that of silicon dioxide. The low-k material is an organic compound containing silicon-oxygen, silicon-methyl, silicon-hydrogen, and carbon-hydrogen bonds. It can offer a dielectric constant as low as 2.5 under optimal conditions. In this work, the intrinsic properties such as thermal stability, the impact of oxygen plasma and copper metal gates are investigated. By employing plasma post treatment, the resistance of HOSP to oxygen plasma and copper penetration is improved significantly. In addition, the results show that the plasma-treated HOSP films have higher thermal stability. These improvements are due to the formations of inorganic layer generated by plasma processes. Abstract (Chinese) ................................................ i Abstract (English) ....................................... iii Acknowledgements ......................................... v Contents ................................................. vi Table Captions ........................................... viii Figure Captions ................................................. ix Chapter 1 Introduction 1-1.General Background ..................................... 1 1-2.Motivation and Material Options ........................ 3 1-3.Organization of This Thesis ............................ 9 Chapter 2 Intrinsic Properties of HOSP 2-1.Introduction ........................................... 10 2-2.Experimental............................................ 11 2-3.Results and Discussion ................................. 12 2-4.Summary ................................................ 15 Chapter 3 Effects of Plasma Post Treatment on HOSP 3-1. Introduction ...........................................17 3-2. Experimental............................................18 3-3. Results and Discussion ................................ 20 3-3-1.NH3 Plasma Treatment.................................. 20 3-3-2.H2 Plasma Treatment................................... 21 3-3-3. N2O Plasma Treatment................................. 22 3-3-4. Thermal Stability of NH3 Plasma-Treated HOSP......... 23 3-3-5. Thermal Stability of H2 Plasma-Treated HOSP.......... 24 3-4. Summary................................................ 25 Chapter 4 Enhancement of HOSP Film in Resisting Oxygen Plasma Process and Copper Penetration 4-1.Introduction.............................................26 4-2.Experimental ........................................... 26 4-3.Results and Discussion ................................. 27 4-4. Summary................................................ 32 Chapter 5 Conclusions and Suggestions for Future Work 5-1.Conclusions ............................................ 34 5-2.Suggestions for Future Work ............................ 36 References.................................................. 38