臺灣博碩士論文加值系統

銅/銅直接接合為未來發展3D-IC領域之重點發展項目之一，主要用於晶片堆疊中，矽穿孔(Through Si via, TSV)電鍍銅銅墊之連結。傳統銅/銅直接接合有幾個待改善的問題，如高接合溫度、高腔體真空度、高荷重加壓以及後退火製程等。本研究以純度99.9%、表面平均粗糙度為2.0 nm的銅塊為試片，進行退火以及接合前預處理包括大氣電漿轟擊和近紅外光照射，配合檸檬酸酸洗與甲酸蒸氣還原兩種去氧化層方法，提出低真空、低溫、高接合強度之銅/銅接合整合製程。實驗結果顯示退火處理，尤其在500oC高溫條件，造成基材軟化與表面粗糙，接合強度較未處理者嚴重劣化。大氣電漿轟擊和近紅外光照射均能有效提升接合效果，以未退火銅塊為例，可分別提升接點強度達31.9%與18.7%。經分析證實大氣電漿轟擊與近紅外光照射均有強化試片次表面並造成表面粗糙的效果，兩者均造成銅次表面之晶格扭曲及殘留壓應力。整合本研究實驗數據亦發現銅/銅接點強度與次表面硬度/粗糙度(H/√R)具正相依關係。潤溼角實驗結果亦釐清預處理提升接合效果的主因為殘留壓應力促進銅原子擴散，而非表面活化。本研究亦成功以大氣電漿轟擊與鉑催化甲酸預處理，進行鍍銅晶圓接合，與未經預處理者相較接合強度增加達61.0%。

Cu to Cu direct bonding is one of the key technologies for 3D chip stacking, especially for the connection of TSV. However, conventional Cu to Cu direct bonding exhibits some drawbacks, such as high bonding temperature, high vacuum, long bonding loading and post-annealing. Therefore, this study aims to develop innovative process to achieve robust Cu to Cu bonding at low temperatures under low vacuum. 99.9% copper bulks with average surface roughness of 2.0nm were used as test materials. Effects of annealing, pre-treatments (including air plasma bombardment and IR exposure), and de-oxidation treatments (such as dipping in citric acid solution and formic acid vapor before bonding), are all carried out for evaluation. Annealed samples, particularly those annealed at 500oC, possessed very poor bonding strength. Air plasma and NIR exposure both gave rise to an significantly enhancement in direct copper bonding. Take un-annealed copper blocks for example, the bonding strength were increased by 31.9% and 18.7% respectively. It is verified that both these two pre-treatments caused a rough surface, lattice distortion and compressive residual stress as well in the sub-surface region. According to the results, a linear relationship between bonding strength and the (H/√R) value (H: sub-surface hardness, R: surface roughness) was first proposed. The water contact angle experiment demonstrates that the improvement of Cu/Cu bonding is due to the enhancement of copper atom diffusion by compressive strength, rather than surface activation. Using this newly developed concept, bonding between copper coated wafers was performed and an increase in bonding strength up to 61.0% was obtained through air plasma bombardment and cleaning with Pt-catalyzed formic acid vapor.

摘要……………………….……………………………………………………….…...i
Abstract……………………………………………………………………………..…ii
總目錄…………………….…………………………………………………………..iii
表目錄……………………………………………………………………………..…..v
圖目錄………………………………………………………………………………...vi
第一章 前言…………………………………………………………………………..1
第二章 文獻回顧……………………………………………………………………..3
2.1 Cu-Cu接合技術簡介………………..……………………………….………3
2.2 提升接合效果之表面改質方法…………………………………….………5
2.2.1 表面活化………………………………………………………..……5
2.2.2 以機械方法產生結構缺陷………………………………………..…6
2.2.3 以電鍍方式控制結晶取向…………………………………….7
2.3 電漿原理及種類………………………………………………………….....7
2.3.1 電漿產生原理…………………………………………………………7
2.3.1 電漿種類………………………………………………………………8
第三章 實驗步驟……………………………………………………………………28
3.1 Cu表面改質處理………………………………………….…………….… 28
3.1.1 試片製備…………………………………………………………..… 28
3.1.2 大氣電漿處理……………………………………………………….. 28
3.1.3 近紅外光處理……………………………………………………….. 28
3.1.4 白金催化甲酸處理………………………………………………….. 28
3.2 經預處理銅表面性質分析……………………………………….............. 29
3.2.1 微觀組織觀察……………………………………………………….. 29
3.2.2 拉曼光譜分析……………………………………………………….. 29
3.2.3 表面粗糙度分析…………………………………………………….. 29
3.2.4 奈米壓痕分析……………………………………………………….. 29
3.2.5 表面殘留應力分析………………………………………………….. 30
3.2.6 表面活性分析……………………………………………………….. 30
3.3 熱壓接合及接點剪力強度測試…………………………………………... 30
3.3.1 Cu/Cu熱壓接合………………………………………………………30
3.3.2 接合試片剪力測試………………………………………………….. 31
第四章 結果與討論………………………………………………………………… 36
4.1退火處理效應…………………………………………….………………... 36
4.2大氣電漿轟擊效應………………….…….………………...……………... 37
4.3近紅外光照射效應…………………….…………………………………... 39
4.4 提升Cu/Cu接合強度之要因探討……………………..…….……………40
4.5 鉑催化甲酸應用於Cu/Cu接合製程探討…………..…….……………....40
4.6大氣電漿轟擊應用於實際鍍銅晶圓接合…………………….…………... 41
第五章 結論………………………………………………………………………… 65
參考文獻…………………………………………………………………………….. 66

[1] R. Maheshwary,” 3D Stacking: EDA Challenges & Opportunities, SEMATECH Symposium,” Tokyo Japan, Sep. 2009
[2] K. N. Chen,a) A. Fan, C. S. Tan, and R. Reif,” Microstructure evolution and abnormal grain growth during copper wafer bonding” App. Phy. Lett. , 81(2002)3774-3776
[3] Y. S. Tang, Y. J. Chang, K. N. Chen, “Wafer-level Cu-Cu bonding technology,” Microelectron. Reliab., 52(2011)312–320.
[4] L. peng, D. F. Lim, L. Zhang, H. Y. Li, and C. S. Tan, “Effect of Prebonding Anneal on the Microstructure Evolution and Cu–Cu Diffusion Bonding Quality for Three-Dimensional Integration” J. Electronic. Mater., 41(2012)2567.
[5] J. Fan, D. F. Lim, L. Peng, K. H . Li and C. S. Tan, “Low Temperature Cu-to-Cu Bonding for Wafer-Level Hermetic Encapsulation of 3D Microsystems” Microsyst Technol, 19(2013)661-667.
[6] Y. P. Huang, Y. S. Chien, R. N. Tzeng, M. S. Shy, T. H. Lin, K. H. Chen, C. T. Chiu, J. C. Chiou, C. T. Chuang, W. Hwang, H. M. Tong and K. N. Chen, “Novel Cu-to-Cu Bonding With Ti Passivation at 180oC Ti in 3-D Integration” IEEE Electron. Device Lett. 34(2013)1551
[7] S. Y. Kim, K. Hong, K. Kim, H. K. Yu, W. K. Kim and J. L. Lee, “Fluxless eutectic bonding of GaAs-on-Si by using Ag/Sn solder “ J. Appl. Phy., 103(2008)076101.
[8] S. L. Chua, G. Y. Chong, Y. H. Lee and C. S. Tan, “Direct copper-copper wafer bonding with Ar/N2 plasma activation “ IEEE-EDSSC, (2015)134-137.
[9] T. Suga, T. Itoh, Z. Xu, M. Tomita and A. Yamauchi, “Low-Temperature Process of Fine-Pitch Au–Sn Bump Bonding in Ambient Air “ IEEE Electronic Components and Technology Conference, (2002)105-111.
[10] T. Sakai, N. Imaizumi and T. Miyajima, “Room-Temperature Cu Microjoining with Ultrasonic Bonding of Cone-Shaped Bump “ IEEE, 52(2012)04CB10-1.
[11] T. Sakai, N. Imaizumi and S. Sakuyama, “Effects of calcium channel blocker-based combinations on intra-individual blood pressure variability: post hoc analysis of the COPE trial “ ICEP-IAAC, 104(2015)464-467.
[12] C. Okoro, R. Agarwal, P. Limaye, B. Vandevelde, D. Vandepitte and E. Beyne, “A novel Cu-Cu bonding approach for 3D integration,” ECTC, pp.1370–1375, 2010.
[13] A. He, T. Osborn, S. A. B. Allen and P. A. Kohl, “Low-Temperature Bonding of Copper Pillars for All-Copper Chip-to-Substrate Interconnections,” Electrochem. Solid St. Lett. ,9(2006)192-195.
[14] R. Agarwal, W. Zhang, P. Limaye, R. Labie, B. Dimcic, A. Phommahaxay and P. Soussan, “Cu/Sn microbumps interconnect for 3D TSV chip stacking,” ECTC, (2010)858–863.
[15] B. Lee, J. Park, S. J. Jeon, K. W. Kwon and H. J. Lee, “A Study on the Bonding Process of Cu Bump/Sn/Cu Bump Bonding Structure for 3D Packaging Applications,” J. Electrochem. Soc., 157(2010)420-424.
[16] H. Y. Chuang, J. J. Yu, M. S. Kuo, H. M. Tong, and C. R. Kao, “Elimination of voids in reactions between Ni and Sn: A novel effect of silver,” Scripta Mater., 66(2012)171-174.
[17] P. I. Wang, S. H. Lee, T. C. Parken, M. D. Frey, T. Karabacak, J. Q. Lu and T. M. Lu, “Low Temperature Wafer Bonding by Copper Nanorod Array,” Electrochem. Solid St. Lett., 12(2009)138-141.
[18] C. Li, X. Liu, K. Li, and M. Chen, “Research on low temperature bonding using nanoporous copper” IEEE-ICEP., (2015)1026-1028.
[19] J. Yan, G. Zou, A. Hu and Y. N. Zhou, “Preparation of PVP coated Cu NPs and the application for low-temperature bonding”, J. Mater. Chem., 21(2011)15981-15986.
[20] C. S. Tan, D. F. Lim, S. G. Singh, S. K. Goulet and M. Bergkvist, “Cu-Cu diffusion bonding enhancement at low temperature by surface passivation using self-assembled monolayer of alkane-thiol,” Appl. Phys. Lett., 95(2009)192-198.
[21]Y. P. Huang, Y. S. Chien, R. N. Tzeng, and K. N. Chen, “Demonstration and Electrical Performance of Cu/Cu Bonding at 150°C With Pd Passivation” IEEE, 62(2015)2587-2592.
[22] E. J. Jang, S. Hyun, H. J. Lee and Y. B. Park, “Effect of wet pretreatment on interfacial adhesion energy of Cu-Cu thermocompression bond for 3D IC packages,” J. Electron. Mater., 2009.38(2009)2449-2454.
[23] W. Yang, H. Shintani, M. Akaike, and T. Suga, “Low temperature Cu-Cu direct bonding using formic acid vapor pretreatment,” ECTC, (2011)2079-2083.
[24] T. G. A. Youngs, S. Haq and M. Bowker, “Formic acid adsorption and oxidation on Cu(110),” Surf. Sci., 602(2008)1775–1782.
[25] W. Lin and Y. C. Lee” Study of fluxless soldering using formic acid vapor,” IEEE Trans. Adv. Packag., 22(1999)592–601.
[26] D. E. Fein and I. E. Wachs, “Quantitative determination of the catalytic activity of bulk metal oxides for formic acid oxidation,” J. Catal., 210(2002)241-254.
[27]W. Yang, H. Shintani, M. Akaike, and T. Suga,” Low Temperature Cu-Cu Direct Bonding using Formic Acid Vapor Pretreatment” IEEE-ICEP, (2011)2079-2083.
[28]T. Suga, A. Masakate, W. Yang and N. Matsuoka, “Formic acid treatment with Pt catalyst for Cu direct bonding at low temperature” IEEE-ICEP, FD3-1(2014)644-647
[29]N. Matsuoka, M. Fujino, M. Akaike and T. Suga, “Process parameters for formic acid treatment with Pt catalyst for Cu direct bonding” ICEP-IAAC, TE2-1(2015)460-463
[30] 張智勛 以有機氣氛進行銅表面改質與金屬直接接合低溫技術開發 國立東華大學
[31]M. Inamura, N. Yoshida, T. Oda, T. Abe, H. Abe, and I. Kusunoki, “Vacuum sealing using surface activation bonding of Si wafer” IEEE, 84(2010)518-522
[32]H. Takagi, R. Maeda, T. R. Chung, and T. Suga, ” Low-temperature direct bonding of silicon and silicon dioxide by the surface activation method” IEEE, 70(1998)164-170
[33]K. Makoto, A. Hiroaki, S. Akio, K. Fumihisa, K. Yoshio, O. Takashi, S. Naoto, “Ray type dependence of radiation induced surface activation phenomenon” Japan INST Metal, 4(2007)423-426
[34]M. Xiaobo, L. Weili, S. Zhitang, L. Wei, and L. Chenglu, “Vold-free low-temperature silicon direct-bonding technique using plasma activation” JAB-FEB, 1(2007)229-234
[35] T. Suga, T. Itoh, Z. Xu, M.Tomita and A. Yamauchi, ” Surface Activated Bonding for New Flip Chip and Bumpless Interconnect Systems” IEEE-ECTC, (2002)105-111
[36] S. Y. Kim, K. Hong, K. Kim, H. K. Yu, W. K. Kim and J. L. Lee, “Effect of N2, Ar, and O2 plasma treatments on surface properties of metals” J. App. Phy., 103(2008)076101-1~076101-3
[37] J. W. Kim, K. S. Kim, H. J. Lee, H.Y. Kim, Y. B. Park and S. Hyun, ” The effect of plasma pre-cleaning on the Cu-Cu direct bonding for 3D chip stacking.” 18th IEEE-IPFA (2011)1-4
[38] S. L. Chua, G. Y. Chong, Y. H. Lee and C. S. Tan, “Direct Copper-Copper Wafer Bonding with Ar/N2 Plasma Activation” IEEE-ESDDC, (2015)134-137
[39]S. Kim, Y. Nam, and S. E. Kim, “Effects of forming gas plasma treatment on low-temperature Cu–Cu direct bonding” J. App. Phy,. 55(2016) 06JC02-1- 06JC02-4
[40] H. Inui, K. Takeda, H. Kondo, and K. Ishikawa, “Electron density change of atmospheric-pressure plasmas in helium flow depending on the oxygen/nitrogen ratio of the surrounding atmosphere” Appl. Phys. Express 3,
55(2010)066101-1.
[41]J. Kim, B. Jeong, M. Chiao, and L. Lin, ”Ultrasonic Bonding for MEMS Sealing and Packaging” IEEE, 2(2008)1521-1525
[42]L. Junhui, Z.Xiaolong, L. Linggang, D. Luhua, and H. Lei, “Effects of Ultrasonic Power and Time on Bonding Strength and Interfacial Atomic Diffusion During Thermosonic Flip–Chip Bonding” IEEE, 3(2012)521-526
[43]J. B. Lee, J. L. AW, and M. W. Rhee, “Evaluation of Die-Attach Bonding Using High-Frequency Ultrasonic Energy for High-Temperature Application”J. Electro. Mater., 9(2014)3317-3323
[44]Y. Aria, M. Nimura, and H. Tomokage, “Cu-Cu Direct Bonding Technology Using Ultrasonic Vibration for Flip-chip Interconnection” ICEP-IAAC, (2015)468-472
[45]K. N. Chen, A. Fan and R. Rfif, “Interfacial morphologies and possible mechanisms of copper wafer bonding” J. Mater. Sci., 37(2002)3441-3446
[46]K. N. Chen, A. Fan, R. Rfif and C. Y. Wen, “Microstructure evolution and abnormal grain growth during copper wafer bonding” App. Phy. Let., 81(2002)3447-3449
[47]J. Cho, M. P. C. Roma, S. Maganty and S. Park, “Mechanism of low temperature copper-to-copper direct bonding for 3D TSV package interconnection” IEEE-ECTC, (2013)1133-1140
[48]C.-M. Liu, H.-W. Lin, Y.-C. Chu, C. Chen, D.-R. Lyu, K.-N. Chen and K. N. Tu, “Low temperature direct copper-copper bonding enabled by creep on highly (111)-oriented Cu surfaces” Scripta Mater., 78-79(2014)65-68
[49] C.-M. Liu, H.-W. Lin, Y.-S. Huang, Y.-C. Chu, C. Chen, D.-R. Lyu, K.-N. Chen and K. N. Tu, “Low temperature direct copper to copper bonding enabled by creep on (111)surfaces of nanotwinned Cu” Sci. Rep., (2015)1-11
[50] 徐逸明 常壓電漿原理、技術與應用 馗鼎奈米科技股份有限公司
[51] B. Eliasson、U. Kogelschatz,“Non Equilibrium Volume Plasma Chemical Processing” , IEEE transaction on plasma science, 6(1991) 1063-1077
[52] G.S. Selwyn et.al, “Materials Processing Using an Atmospheric
Pressure,RF-Generated Plasma Source”, Contrib. Plasma Phys.,
6(2001)610
[53] 楊超棨 介電質差壓電漿產生器之開發及其於質譜分析之應用
國立中山大學
[54] 張家豪 電漿源原理與應用之介紹 國立清華大學
[55] X.J. Dai etc. “Plasma treatment advantages for textiles “ Textile Institute 81st World Conference, Melbourne, Australia, 2001.
[56] M.G. McCord etc., Textile Res. J.72, 6(2002)491-498
[57]何主亮教授 電漿基礎 教育部材料科技改進計畫
[58] S. Kanazawa etc., “Characteristics of Organic Light-Emitting Devices by the Surface Treatment of Indium Tin Oxide Surfaces Using Atmospheric Pressure Plasmas “J. Phys. D: Appl. Phys., 21(1998)836
[59]Y. Takahasshi, and K. Uesegi, “Stress induced diffusion along adhesional contact interfaces” Acta Mater., 51(2003)2219-2234
[60]K. M. Crosby, “Grain Boundary Diffusion in Copper under Tensile Stress”
Cornell University Library, 2003