矽酸鹽類低介電常數材料之研究

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大部分碳氫成分分解，再浸泡濕式的化學蝕刻溶液（wet stripper）來分解剩餘的碳氫成分，達到光阻灰化（ashing）的目的，但無論是氧電漿製程或是濕式的化學蝕刻液都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、熱穩定性處理後的特性與利用數種電漿與化學溶液對氧電漿與濕式蝕刻液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薄膜抗氧電漿及蝕刻液的能力；而利用一些化學溶液也可修復氧電漿與蝕刻液對我們的薄膜的傷害，使得漏電流與介電常數能維持在相當低的結果。經過上述的前續及後續處理，低介電常數材料- HOSP 在現今金屬連線製程整合應用上將具有極大潛力。

As IC technology moves into the deep submicron regime, it is required to decrease the metal pitch and to increase the number of metal layers for interconnect to accommodate the increased packing density and functional complexity. This makes propagation delay in interconnects becomes an appreciable fraction of the total time delay. Use of the spin on glass (SOG) low dielectric constant material (low-k) as the intermetal dielectric (IMD) results in low inter-line capacitance, high speed, low power dissipation, and low cross-talk noise. An organic SOG, Hybird-Organic –Siloxane-Polymer (HOSP), is one of the promising low dielectric constant materials. The HOSP with dielectric constant of 2.6 has good filling, low stress and comparable enough mechanical strength. In this work, the intrinsic properties of HOSP film, including physical, electrical and thermal stability have been studied. In addition, the compatibity of HOSP film with integration processes has been investigated. In integration processing, photoresist stripping is commonly implemented with O2 plasma ashing and wet stripper solution dipping. Dielectric properties of HOSP film could be degraded during photoresist removal. To mitigate the issue, gas plasma pre-treatments and chemical solution (Trimethylchlorosilane (TMCS) and Hexamethyldisilazane (HMDS)) post-treatments were proposed. Material and electrical analyses were also used to explain these improvements.