臺灣博碩士論文加值系統

在極大型積體電路製造上，銅因其有較低之電阻值以及較高抵抗電致遷移的能力，已成為未來金屬內連接線的另一選擇。而嵌入式製程則為製作銅導線之主要方式，其中，銅金屬及擴散阻障金屬之化學機械研磨更是影響銅金屬嵌入式導線製程良率之關鍵。然而，經過化學機械研磨後，晶圓表面會殘留大量的污染物，包括研磨過程所使用的研磨粉體、金屬離子及其他不純物之污染。若無有效之清洗製程去除此外來之污染物，則將影響後續製程之良率，而且殘留於介電層表面之大量銅離子污染極易擴散進入主動元件區，造成元件特性之劣化，故研磨後清洗製程為成功應用化學機械研磨於銅金屬嵌入式導線製程之關鍵技術。
在本論文中，我們提出一種新的清洗方法可以有效的去除吸附於銅金屬表面之膠體二氧化矽研磨粉體。此清洗製程包括以稀釋硝酸與BTA混合之水溶液進行磨光(buffing)，以及PVA刷子搭配非離子性界面活性劑Triton X-100進行刷洗。在磨光的過程中，藉由硝酸輕微蝕刻去除銅金屬表面之氧化銅鈍化層，可以有效去除吸附之膠體二氧化矽，而BTA將於銅金屬表面形成Cu(I)-BTA保護層以取代氧化銅鈍化層。然而Cu(I)-BTA表面為疏水性，使得膠體二氧化矽極易再度吸附於其表面。因此經過磨光程序後，再以界面活性劑Triton X-100作為濕潤劑進行刷洗，將可改善Cu(I)-BTA表面之疏水性並完全去除殘留之膠體二氧化矽研磨粉體。而Triton X-100之濕潤機制乃藉由接觸角與表面張力之量測來進行研究。藉由我們的清洗製程，可以有效地去除吸附之膠體二氧化矽研磨粉體，同時在清洗過程中並未造成銅導線之腐蝕。
銅金屬化學機械研磨後清洗製程之另一關鍵為去除介電層表面殘留之銅離子污染。在本研究中，採用非極性金屬螯合劑D2EHPA之水溶液進行刷洗，以有效去除金屬離子之污染。D2EHPA具有膦酸基對於過渡金屬離子為強錯合劑，金屬離子在水溶液中會與D2EHPA以配位的方式形成電中性之螯合鹽類。D2EHPA濃度與水溶液pH值對於D2EHPA螯合能力之影響乃藉由溶劑萃取實驗進行研究。研究結果顯示，藉由D2EHPA水溶液進行刷洗可以有效地去除介電層表面之銅離子污染。

Under intensive investigation for Ultra-Large-Scale-Integration (ULSI), copper has emerged as an attractive, alternative choice for future interconnect applications owing to its low electrical resistivity and high electromigration resistance. The damascene process is regarded to be an essential and critical step for manufacturing copper interconnects, and the chemical-mechanical polishing (CMP) of copper and barrier layer metals is the key to enable this process. Unfortunately, copper CMP process leaves a large amount of contaminants on the surface, which must be eliminated. There are two major contaminants. One is the abrasive from the polishing slurry, and the other is the metallic impurity contamination on the wafer surface.
In this study, a novel method for efficient removal of colloidal silica abrasives from polished copper surface was proposed and demonstrated. This post-CMP cleaning process involves buffing process with diluted HNO3/BTA aqueous solution and a PVA brush scrubbing process with wetting surfactants, Triton X-100, for copper surface passivation and colloidal silica removal. Buffing with HNO3/BTA aqueous solution was able to remove copper oxide and forming Cu(I)-BTA hydrophobic passivation. Scrubbing with Triton X-100 surfactant is to enhance wettability on Cu(I)-BTA surface for the removal of residual silica abrasives. The wetting ability of Triton X-100 was determined by a contact angle and surface tension measurement. By this cleaning process, it was demonstrated that colloidal silica abrasives could be removed efficiently without copper corrosion.
One of the greatest challenges to the copper CMP cleaning process is the removal of residual copper contamination from the interlevel dielectric (ILD) surface. To meet this requirement, a PVA brush scrubbing process with non-polar metal chelator, D2EHPA, solution was introduced. The D2EHPA molecules bearing the phosphonate group are strong complexing agent towards transition metal ions. D2EHPA with metal ion in solution to form uncharged metal-chelate complexes by coordination. The effects of D2EHPA concentration and pH on copper ion chelating capability of D2EHPA were investigated by solvent extraction experiment. We have shown that scrubbing with D2EHPA is effective in removing copper contamination from the ILD surface.

Abstract (in Chinese)….…...……………………………………………………………..i
Abstract (in English)……………………………………………………………...……..ii
Acknowledgements………………………………..……………………………………iii
Contents…………………………………………………………………………………iv
Table Caption……………………………………………...…………………….………vi
Figure Caption……………………………………………...…………………………..vii
Chapter 1 Introduction…………………………………………………………………...1
1.1 Motivation……………..………………………………………………...1
1.1.1 Copper Interconnect Technology…………………………………1
1.1.2 Copper Damascene Process and CMP……………………………1
1.1.3 Post-Copper CMP Cleaning……………………………………...3
1.2 Thesis Outline……………………………………………………………4
Chapter 2 Fundamental Concepts………………………………………………………..6
2.1 CMP in the Copper Damascene Process………………………………...6
2.2 Distribution Equilibrium…………………………………………………7
2.3 Wetting by Surfactants…………………………………………………...8
2.3.1 Mechanisms of Adsorption……………………………………….9
2.3.2 Adsorption Isotherms…………………………………………...10
Chapter 3 Copper Ion Complexation with Non-Polar Metal Chelators………………..12
3.1 Introduction…………………………………………………………….12
3.2 Experimental Procedures……………………………………………….13
3.2.1 Chelating Capability of Metal Chelators………………………..13
3.2.2 Solubility of Metal Chelators in Water………………………….14
3.3 Results and Discussions………………………………………………...15
3.3.1 Chelating Capability of Metal Chelators………………………..15
3.3.2 Solubility of Metal Chelators in Water………………………….17
3.4 Summary………………………………………………………………..18
Chapter 4 Wetting Ability of Surfactants on Cu(I)-BTA Surface……………………...19
4.1 Introduction…………………………………………………………….19
4.2 Experimental Procedures……………………………………………….20
4.2.1 Wetting Ability of Surfactants…………………………………..20
4.2.2 Surface Charge of Colloidal Silica……………………………...21
4.3 Results and Discussions………………………………………………...22
4.3.1 Wetting Ability of Surfactants…………………………………..22
4.3.2 Controlling of Surface Charge by Surfactants…………………..24
4.4 Summary………………………………………………………………..25
Chapter 5 Post-CMP Cleaning in the Copper Damascene Process…………………….26
5.1 Introduction…………………………………………………………….26
5.2 Experimental Procedures……………………………………………….27
5.2.1 Sample Preparation……………………………………………...27
5.2.2 CMP and Post-CMP Cleaning Process………………………….28
5.2.3 The Performance of Post-CMP………………………………….30
5.3 Results and Discussions………………………………………………...31
5.3.1 Colloidal Silica Abrasives Removal…………………………….32
5.3.2 Copper Contamination Removal………………………………..35
5.4 Summary………………………………………………………………..36
Chapter 6 Conclusions………………………………………………………………….37
References……………………………………………………………………………...39
Tables…………………………………………………………………………………...43
Figures………………………………………………………………………………….48
Publication List…………………………………………………………………………94
Vita……………………………………………………………………………………...95

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