臺灣博碩士論文加值系統

本論文探討電鍍液在電鍍過程中的劣化行為，採用的電鍍液系統分別為單獨添加PEG之溶液與同時添加PEG、SPS之溶液，電鍍模式為定電流電鍍。利用三種電化學分析（電鍍v-t曲線、交流阻抗測試、極化曲線掃瞄）來進行電鍍液的檢測，並利用掃瞄式電子顯微鏡（SEM）觀察電鍍製程填洞良率與銅膜表面平整度。對於實驗結果的討論，參考文獻中可能的機制並加以引用，同時設計適當的實驗來驗證此機制影響我們電鍍系統的可能性。
在單獨添加PEG之溶液中，填洞良率與銅膜性質皆隨著電鍍液時效而劣化。關於此現象我們引用了兩個有可能的機制來解釋：1)長鏈PEG裂解，2)PEG與銅離子形成錯和物。在電鍍製程中，未裂解的長鏈PEG藉著吸附達到有效的抑制，此行為決定了定電流模式電鍍之下所需的電壓；當PEG裂解，包覆銅離子形成錯和物，降低溶液導電度，進而造成電鍍電壓逐漸上升。
在同時添加PEG、SPS之溶液中，首先對於兩添加劑的關係，我們對文獻中的所提的機制做小部分的修正與補充。而在電鍍過程之中，電鍍電壓呈現兩階段的變化：在電鍍初期，電壓為逐漸下降的趨勢；時效增加之後，電壓為逐漸上升的趨勢。對此我們採用三個可能的機制來進行討論。此外，在溶液電阻發生變化之後，電鍍填洞良率與銅膜性質仍能有效維持。

The degradation effects on (PEG, SPS)-containing baths are investigated in this study. The baths are analyzed by three methods: in-situ measured v-t curves of galvanostatic plating, AC-impedance scan, and i-E curve scan. The gap-filling capability for the baths was examined by cross-sectional SEM images. By modifying the mechanisms that were presented in previous literatures, some possible models for the degradation are proposed.
In the PEG-containing bath, an evident deterioration of the gap-filling yield and of the surface roughness of the deposited film are observed after ECD aging. Two mechanisms are proposed to explain this degradation: 1) crack of long-chain PEGs, and 2) complexing between PEGs and Cu ions. When some long-chain PEGs crack into shot-chain ones, the remained long-chain PEGs still dominate the value of cell voltage, while slight fluctuation in voltages is attributed to the formation of complexes that results from the continuously cleaved short-chain PEGs.
In the (PEG, SPS)-containing bath, a modified mechanism of the behaviors of PEG and SPS are proposed and called “Slow adsorption / desorption mechanism.” As the electroplating proceeds, the variation among v-t curves is divided into two trends: the cell voltages are increasing following by decreasing as more samples plated. Besides, the yield of gap-filling is slightly affected by the variation of the bath, and the superfilling could be maintained even after aging of bath. Three possible mechanisms for the trend of degradation are proposed and will be further discussed in this thesis.

Chapter1. Introduction
1.1. Review of Electrochemical deposition (ECD) in Multilevel Interconnection
1.1.1. Basics of Copper ECD
1.1.2. Copper ECD in damascene processing
1.1.3. Organic Additives of Plating Baths
1.2. Overview of thesis
Chapter2. Effect of PEG on Cu ECD
2.1. Review of Previous Studies
2.1.1. Characteristics of PEG
2.1.2. Mechanism for superfilling
2.1.3. Degradation
2.2. Experiments
2.3. Results and Discussion
2.3.1. Evolution of cell voltage during ECD process
2.3.2. Degradation of PEG-containing electrolyte
2.3.2.1. Factors affecting the cell voltage during ECD
2.3.1.2. Proposed Model
2.3.2. Effect of degradation on gap-filling
2.4. Conclusions
Chapter3. Effect of SPS on Cu ECD
3.1. Review of Previous Studies
3.1.1. Characteristics
3.1.2. Filling model
3.2. Experiment
3.3. Results and Discussion
3.3.1. Roles of PEG and SPS during ECD process
3.3.2. Degradation of the electrolyte
3.3.3. Effect of degradation on gap-filling
3.4. Conclusions
Reference

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