低介電常數材料MSQ之製程整合

Abstract

摘 要 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，利用低介電常數材料來降低金屬連線中的電容值，進而降低時間延遲以增進元件工作效率。,以期降低訊號在金屬連線間傳送的時間延遲，達到增進元件工作效率。 本論文研究積體電路製造技術中的多層導體連線製程，探討低介電常數材料(MSQ) 在整合中遇到的問題所做的研究(1)化學機械研磨時所造成的損害(2)去光阻時對有機材料MSQ所造成的損害(3)對銅金屬接觸的效應做詳細的探討與分析。 並利用電漿處理(H2 and NH3)解決之，利用電漿處理過後(H2 and NH3)，發現此材料可有效抵擋上述的侵蝕和入侵,原理主要在於用(1)氫（H2）電漿處理後材料(MSQ)上的無鍵結鍵，形成矽氫鍵去鈍化材料表面，使其他元素無路徑入侵材料內部，使材料劣化。(2)氨(NH3) 電漿處理後材料上形成矽氮鍵，使得表面變成一層堅固的膜，不易被入侵，以維持其基本特性。

Abstract As integrated circuit dimensions continue to shrink, interconnect RC delay becomes an increasingly serious problem. Fabrication of interconnect structures using new materials of low resistivity and low permittivity to replace the traditional Al and SiO2 interconnect technology is in high demand. Specially, copper and low dielectric constant (low-k) polymers show great promise. Among various low-k materials, spin-on glass (SOG) materials have been widely used as an interlayer dielectric in multilevel interconnections because they are applied easily and have relatively low process costs. One class of materials, which offers many of properties of silica (SiO2) (hardness, thermal and dimensional stability etc.) are the organosilicates. Methylsilsesquioxane (MSQ) represents an important member of this family. MSQ exhibits a relatively low dielectric constant (k=2.6-2.8) as compared to SiO2 (k=4.0).It is intrinsically hydrophobic, has reasonable mechanical hardness, and possesses exceptional thermal and dimensional stability (in excess of 450℃). For these reasons, MSQ represents an excellent candidate for applications on the multilevel interconnect architecture. On the other hand, surface planarization is a key technology during the manufactures of multilevel interconnects. Chemical mechanical planarization (CMP) process is satisfactory for the requirement of global planarization technology. As a result, a novel CMP process for the low-k interlayer has been proposed to enhance performance of IC. In this work, the characteristics of post-CMP low-k MSQ have been investigated. Experimental results have shown that the dielectric properties of MSQ are degraded by CMP process. Applying plasma post-treatment such as NH3 and H2 plasma, however, both the leakage current and dielectric constant of post-CMP MSQ are decreased and closed to that magnitude of as-cured MSQ film. For the interaction of copper and low-K MSQ, we also find that dielectric degradation will occur due to copper diffusion into post-CMP MSQ film. Both the leakage current and dielectric constant of Cu-gate capacitor are increased compared to Al-gate capacitor when process temperature is higher than 450oC. Material and electrical characteristic measurement also show that NH3 and H2 plasma treatments are efficient against copper diffusion into post-CMP MSQ. Therefore, dielectric properties of low-K MSQ can be efficiently enhanced by both plasma treatments. 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 ................................................. 2 1.3 Organization of This Thesis ......................................................... 6 Chapter 2 Chemical Mechanical Polishing of Organic Low-K Methylsilsesquioxane 2.1 Introduction ................................................................................ 8 2.2 Experimental Procedure ............................................................. 8 2.3 Results and Discussion ............................................................... 11 2.3.1 CMP MSQ with Silicate-based Slurry ............................ 11 2.3.2 CMP MSQ with Additive TMAH ................................... 12 2.3.3 Curing->O2 or H2 Plasma->CMP................................... 13 2.3.2 Bake->CMP->Curing .......….....……………….......... 14 2.4 Summary .................................................................................... 15 Chapter 3 Improvement of Post-CMP Characteristic on MSQ by Plasma Treatment Techique 3.1 Introduction ................................................................................ 16 3.2 Experimental Procedure ............................................................. 17 3.3 Results and Discussion ............................................................... 19 3.3.1 Electrical Properties of Post-CMP MSQ..................... 20 3.3.2 O2 Plasma Impact on post-CMP MSQ …….………....... 22 3.3.3 Effects of H2 Plasma Treatment .........................…...........23 3.3.3 Effects of NH3 Plasma Treatment .................................... 26 3.4 Summary .........................………............................. 29 Chapter 4 The Effect of Copper on Post-CMP Low-K Methylsilsesquioxane Spin on Glass 4.1 Introduction ................................................................................ 31 4.2 Experimental Procedure ............................................................. 32 4.3 Results and Discussion ............................................................... 34 4.3.1 Impact of Copper Diffusion on post-CMP low-K ..... 34 4.3.2 Effects of Plasma Treatments on Copper Diffusion Resistance……………………..………….. 36 4.4 Summary ..............………......................................... 39 Chapter 5 Conclusions and Suggestions for Future Work 5.1 Conclusions ................................................................................ 41 5.2 Future Work ................................................................................ 43 References .................................................................................................................. 44