以PEG添加劑用於晶圓金屬化之酸性鍍銅系統之研究

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研究生：	葛書鈴 Shu-Ling Ko
論文名稱：	以PEG添加劑用於晶圓金屬化之酸性鍍銅系統之研究 A study of the PEG additive for acid copper deposition for wafer metallization
指導教授：	王詠雲 Yung-Yun Wang 萬其超 Chi-Chao Wan
口試委員:
學位類別：	碩士 Master
系所名稱：	工學院 - 化學工程學系 Department of Chemical Engineering
論文出版年：	2004
畢業學年度：	92
語文別：	英文
論文頁數：	77
中文關鍵詞：	無孔沉積、聚乙二醇、添加劑、吸附、銅內連線
外文關鍵詞：	superfilling, polyethylene glycol, additive, adsorption, copper interconnection
相關次數：	點閱：2 下載：0
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為了達到無孔洞的沉積，我們在鍍液中加入添加劑。傳統電鍍銅的鍍液包含了多種的添加劑。在眾多添加劑中，聚乙二醇(Poly-ethylene glycol, PEG)因為能吸附於電極表面上，達到抑制電流的作用，因此在鍍液中扮演著抑制劑(Suppressor)的角色。尤其當鍍液中含有氯離子(Cl-)時，其抑制的效果尤其明顯。再加上原本因擴散行為所造成濃度的分佈差異，使得導孔內的電流分佈因此受到改變，進而使我們興起以單一添加劑系統進行填孔相關研究的動機。

在本研究中，我們分別以添加不同分子量及濃度聚乙二醇的硫酸銅鍍液進行電鍍銅填孔的實驗。實驗結果顯示，在添加較高分子量聚乙二醇的情況下，會獲得較佳的填孔結果。接著，我們利用循環伏安法(Cyclic voltammetry)、線性掃描伏安法(Linear sweep voltammetry)、定電流法(Chronopotentiometry)來量測不同分子量及濃度下的聚乙二醇在銅電極上的吸附行為。輔以聚乙二醇擴散行為的分析，我們可以解釋添加較高分子量聚乙二醇的情況下，之所以可得到較好的填孔結果，主要是因為分子量較大之聚乙二醇其擴散能力較差，使得其在導孔開口端的吸附量會比底部大得多，再加上其對電流較強的抑制能力，使得開口端的沉積速率得到充分地抑制，整個孔洞內的電流分佈呈現底部大於開口的趨勢，而達到無孔洞沉積的效果。

除了電化學的分析之外，我們也針對不同分子量情況下所沉積之銅層，以掃描探針顯微鏡(SPM)、場發射槍掃描式電子顯微鏡(FEGSEM)、和X光繞射儀(XRD)等儀器，進行與鍍層性質相關的研究分析。由SEM和AFM的結果，我們可看出銅鍍層的顆粒大小會隨著聚乙二醇分子量增加而變小，且鍍層會呈現較不均勻地分佈。XRD的結果則顯示，有添加聚乙二醇所獲得的銅層，其(111)對(200)結構的比例會比沒有添加劑的情形來得小。

The damascene process for fabrication of copper interconnects requires void-free deposition into submicron or vias. Since these trenches and vias are always of high aspect ratio, void-free (or, superfilling) deposition can be realized only when the deposition rate is higher in the bottom of the via than at the entrance. The achievement of void-free deposition requires the use of additives in the plating bath. A conventional solution for copper electroplating contains additives. Among various additives, PEG functions as the suppressor because it can inhibit deposition kinetics, especially when chloride ion is present.

In this laboratory, a single additive system was developed based on the characteristics of current-potential response of acid copper sulfate bath containing PEG and chloride ion. The filling experiments were carried out by the acid copper bath containing PEG of different molecular weights in various concentrations. The filling results show that better filling results can be obtained as the molecular weight of PEG increases. Several electrochemical methods have been employed, including chronopotentiometry, linear sweep voltammetry (LSV) and cyclic voltammetry (CV), to study the PEG adsorption and diffusion behavior.

Besides the above electrochemical analyses, related properties of the as-deposited copper film have also been measured by the atomic force microscopy (AFM), field emission gun scanning electron microscopy (FEGSEM), and the X-ray diffraction (XRD) methods. The results obtained by AFM and SEM show that both the grain size of Cu deposit and the uniformity of metal distribution decreases as the mol. wt. of PEG increases. From the results of XRD, we find that the ratio of (111-200) orientation in the case of the electrolyte containing PEG3200 is much lower than that containing no additives.

Abstract             Ⅰ
中文摘要             Ⅲ
List of Figures      Ⅴ
List of Tables       Ⅸ

Chapter 1.
Introduction and Literature Rewiew                         1
1-1. Introduction                                          1
1-2. Literature review                                     5
 1-2-1. Electroplating copper into submicron features      5
 1-2-2. Effect of additives on electroplating of copper   11
 1-2-3. Fundamental adsorption isotherm of additives      24
 1-2-4. Surface coverage measurement by electrochemical methods                                                   27
1-3. Motivation and objective of this research            32

Chapter 2. Experimental Procedures                        34
2-1. Filling capability                                   34
2-2. Electrochemical analyses                             36
2-3. Film properties                                      37

Chapter 3. Results and Discussions                        38
3-1. The molecular-weight and concentration effect of PEG
on the degree of suppression for copper deposition        38
3-2. The molecular-weight and concentration effect of PEG
on the via-filling                                                   54
3-3. The molecular-weight effect of PEG on the film properties                                                65
 3-3-1. Film morphology                                   65
 3-3-2. Crystallographic texture                          70

Chapter 4. Conclusions                                    72

References                                                74

                                

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