具有低介電係數阻障介電層的研究

Abstract

本論文研究積體電路製造技術中的多層導體連線製程。隨著半導體技術的進步，元件的尺寸也不斷地縮小，而多層金屬導體連線的設計，也成為超大型積體電路技術所必須採用的方式。然而，隨著金屬導線層的數目增加及導線間的距離不斷縮小，電子訊號在金屬連線間傳送時，金屬連線的電阻-電容延遲時間(RC delay time)，變成半導體元件速度受限的主要原因。為了降低訊號傳遞的時間延遲，現今已經發展以金屬銅（電阻率為1.7μΩ-cm）來取代金屬鋁（電阻率為2.7μΩ-cm）成為導線的連線系統。而在降低電容方面，則朝向低介電常數 ( low-k ) 材料發展。但是在銅與鑲嵌的製程與電性操作的環境下，溫度與電場的作用，銅極易擴散至低介電常數材料中，並與之發生反應，造成材料特性的劣化與漏電流增大，甚至導致介電質崩潰。因此，在符合製程相容性要求的前提之下，發展具抗銅金屬擴散特性的介電阻障層材料，便成為重要的研究課題。 目前一種碳化矽(silicon carbide)材料薄膜，具有低的介電係數(k~4)，因此受到廣大的矚目，而被應用於介電阻障層技術中，用來取代傳統具高介電係數的氮化矽(silicon nitride) (k~8)，以降低導線系統的延遲時間。本論文將討論碳化矽膜的材料基本特性，以及其在製程整合時會遇到的一些問題，例如氧電漿與熱退火處理對碳化矽膜的影響；除此之外並研究其與銅或鋁導線整合時，所衍生的電性問題，並探討其漏電流的機制。

In the era of deep submicron semiconductor fabrication, interconnect resistance-capacitance (RC) delay dominates the performance of whole integrated circuits (ICs). To mitigate the issue, two realistic methods are accepted popularly. The first method is to replace the aluminum wires with copper interconnects which offer lower resistivity. The second method is to use a lower dielectric constant material as the inter-metal dielectric (IMD). However, some difficulties come up in integrating low-k material with copper wires, including dielectric integrity and high diffusivity of copper ions. In order to prevent copper from penetrating into dielectric material under both high electric fields and operation temperature, barrier dielectric have been developed to enhance resistance to copper drift. Silicon carbide (SixCy) with lower dielectric constant (k~4) is a promising barrier dielectric material to replace typically used silicon nitride (SixNy), (k~8). In this study, we will discuss the basic material properties of silicon carbide, such as FTIR, AES, SIMS and XPS analysis. It’s investigated that the properties of nitrogen-doped silicon carbide are much better than those of pure silicon carbide. Moreover, the electrical characteristics remain stable after O2-plasma ashing, thermal treatment and even BTS (bias-temperature-stress) in high electric field (up to 4MV/cm, 150oC, 1000 sec). These treatments are frequently implemented will be faced in the fabrication process. It’s also demonstrated clearly that the more nitrogen concentration of silicon carbide, the better barrier ability against copper diffusion. Finally, we find that the leakage behavior of silicon carbide is Poole-Frenkel transport which is similar to conventional amorphous silicon nitride film.