低介電常數材料（HSQ）之特性探討

Abstract

低介電常數材料（HSQ）之特性探討 研究生:張虔輔 指導教授 : 施敏 博士 張鼎張 博士 國 立 交 通 大 學 電子工程學系 電子研究所碩士班 摘要 隨著元件尺寸愈做愈小，元件速度主要受限於訊號在金屬導體連線間傳送的時間延遲(RC delay)，所以金屬內連線的時間延遲變成控制元件操作速度的主要原因。為了改善這個問題，低介電常數材料受到廣泛的研究，期望能降低金屬導體連線內的雜散電容，提高元件的速度。 HSQ是一種以二氧化矽為基礎，無機的低介電常數材料，介電常數大約在2.8左右；此外銅金屬因為其高導電率和抗電致遷移的能力較鋁為佳，所以被研究用來取代鋁導線。但由於銅原子很容易擴散到以二氧化矽為基礎的介電層中，造成電性不穩定，一般而言會採用阻障層來抑制銅原子的擴散，但阻障層會使接觸電阻提高，進而降低積體電路的運作速度。 在本論文中，HSQ電容在外加高溫度及高電場的應力(stress)影響後，利用C-V曲線、漏電流情形及材料分析來進一步探討銅離子的擴散及電荷分佈的情形；我們採用電漿處理的方式來取代阻障層，氫氣電漿處理過後，HSQ表面懸鍵(dangling bonds)減少，表面變得更為緻密，使得銅離子不易擴散到介電層裡；在經過氨氣電漿處理過後，由於HSQ表面形成氮化矽的薄膜，HSQ表面分佈的電荷數變少，且銅離子不易擴散。綜合上述，電漿處理於現今銅金屬及低介電常數材料HSQ的整合應用上具有極大的潛力。

Study of Hydrogen Silsesquioxane ( HSQ ) - A Low Dielectric Constant Material Student : Chien-Fu Chang Advisor : Dr. Simon M. Sze Dr. Ting-Chang Chang Institute of Electronics National Chiao-Tung University Abstract Hydrogen silsesquioxane ( HSQ ) is an important low-k material . It has been extensively studied for its basic properties and its application to microelectronics . The quality of low-k HSQ film is dependent on the residual quantity of Si-H bonds after curing . A low dielectric constant can be achieved if the density of Si-H bonds is maintained at a high level and the formation of Si-OH bonds in the film is minimized .The dielectric constant of HSQ is about 2.8 . The reaction of low-k HSQ film with copper was investigated by using metal-insulator-semiconductor ( MIS ) capacitor . In addition , different plasma treatments ( NH3 and H2 ) were applied on HSQ films instead of conventional barrier layer for enhancing the resistance of HSQ film against copper diffusion . Stressing HSQ films at temperatures up to 200℃ and electric fields up to 1.5 MV/cm was conducted on copper-insulator-silicon capacitors to investigate the penetration of Cu ions into HSQ and the existance of charges at the interface between the metal and the HSQ film . The results of capacitance-voltage , current-time , voltage-time , and current density-electric filed measurements were compared . For the H2 plasma treatment , the hydrogen radicals could recover the broken Si-H bonds and form a passivation layer at the surface of the HSQ film . It would prevent copper from penetrating into HSQ . For the NH3 plasma treatment , plasma provided nitrogen to form a thin SiNx layer at the surface of the HSQ film . This would maintain the porous structure and prevent low-k HSQ from copper attack . It could also decrease positive charges at the interface between HSQ and metal under bias-temperature-stress stressing . Abstract ( Chinese ) ………………………………………………………………… i Abstract ( English ) ………………………………………………………………… ii Acknowledgement ………………………………………………………………… iv Contents …………………………………………………………………………… v Table Captions ……………………………………… …………………………… vii Figure Captions …………………………………………………………………… viii Chapter 1 Introduction 1.1 General Background ………………………………………………… 1 1.2 Motivation & Material Options ……………………………………… 5 1.3 Organization of This Thesis ………………………………………… 8 Chapter 2 Fundamental Concept and Experimental Method 2.1 Background ………………………………………………………… 10 2.2 Experimental ………………………………………………………... 12 2.3 Characterization of the HSQ film …………………………………… 13 Chapter 3 Properties of Hydrogen Silsesquioxane 3.1 Properties of HSQ Film ……………………………………………… 15 3.1.1 Intrinsic Properties of HSQ Film …………………………… 16 3.1.2 Electrical Property of HSQ Film …………………………… 17 3.1.3 Thermal stability of HSQ film ……………………………… 17 3.2 The Effect of NH3-plasma treatment for HSQ …………………………… 19 3.2.1 Material Property …………………………………………… 20 3.2.2 Electrical Property …………………………………………… 20 3.2.3 Comparison between HSQ with and without post-treatment … 21 3.3 Measurement of C-V Curves for HSQ ……………………………… 22 3.3.1 C-V Curves for HSQ without post-treatment ………………… 22 3.3.2 C-V Curves for HSQ with post-treatment …………………… 23 Summery ………………………………………………………………… 23 Chapter 4 Kinetics of Charges and Copper Drift in HSQ Dielectric Material 4.1 Oxide-padded Dielectric Material …………………………………… 26 4.2 Oxide-padded Dielectric Layer with NH3 Plasma Treatment ……… 27 4.3 Oxide-padded Dielectric Layer with H2 Plasma Treatment ………… 28 4.4 Comparison Between Capacitor with and without Plasma Treatment … 30 4.5 Inorganic Barrier Layer ……………………………………………… 31 4.6 Summary …………………………………………………………… 32 Chapter 5 Conclusions and Future Work 5.1 Conclusions …………………………………………………………… 33 5.2 Future Work …………………………………………………………… 34 References ………………………………………………………………………… 36