【作者】 钟琴；

【导师】 辜敏；

【作者基本信息】 重庆大学 ， 环境科学， 2010， 硕士

【摘要】 铝是传统的集成电路的互连介质,由于铜比铝具有更低的电阻率和较高的抗电迁移性,是较铝更理想的材料。要实现铜在芯片上微米或亚微米级刻槽中的超等角电沉积填充,必须借助添加剂。铜超等角电沉积填充镀液中通常采用的添加剂有3-巯基-1-丙烷磺酸钠(MPS)或者聚二硫二丙烷磺酸钠(SPS)、聚乙二醇(PEG)和氯离子(Cl~-)。论文采用循环伏安(CV)、线性电位扫描(LSV)、计时安培(CA)和交流阻抗(AC impedance)电化学方法结合扫描电镜(SEM)方法研究了在CuSO4-H2SO4体系中,添加剂MPS、PEG、Cl~-及其协同作用对铜在玻碳电极(GCE)上的电沉积过程的影响。CV、LSV和电化学阻抗谱(EIS)实验结果一致表明:MPS单独作用时,阻化铜的电沉积,并且随着MPS浓度的增加,其阻化作用增强;在电解液中存在添加剂MPS和Cl~-(MPS-Cl~-)时,CV曲线上铜的沉积峰电位正移程度比只含有Cl~-更大,LSV曲线正移程度也更大,反应电阻比只含有Cl~-更小,这些表明MPS-Cl~-对铜的电沉积过程有强烈的促进作用,并且比只含有相同浓度Cl~-的促进作用更强,并且随着MPS浓度的增加,促进的作用增强;MPS和PEG(MPS-PEG)的协同作用对铜的电沉积具有抑制作用,并且比MPS或者PEG单独作用下的阻化作用更强,当保持溶液中的PEG浓度不变时,随着MPS浓度的增加,对铜电沉积的阻化作用也增大;添加剂MPS、PEG和Cl~-同时存在(MPS-PEG-Cl~-)对铜的电沉积具有促进作用,并且随着MPS浓度的增加,促进的作用增强。CA和SEM研究结果表明:MPS可以提高铜的成核数密度,对铜的电结晶表现为促进作用,并且成核数目随着MPS浓度的增大而增加,铜离子的扩散系数没有明显变化;MPS-Cl~-可以提高铜的成核数密度和铜离子的扩散系数,并且成核数密度随着MPS浓度的增大而增加;MPS-PEG作用下会减小铜的成核数密度,成核数密度随着MPS浓度的增大有减小的趋势,对铜离子的扩散系数没有明显影响;MPS-PEG-Cl~-会提高铜的成核数密度,并且成核数密度随着MPS浓度的增大而增加。用CA实验对铜成核机理的研究表明:在CuSO4-H2SO4电解液中,没有添加剂时,铜在玻碳电极上的电结晶符合三维瞬时成核机理;添加剂MPS或MPS-PEG不改变Cu的电结晶成核机理,仍然按瞬时成核和三维生长方式进行;MPS-Cl~-或MPS-PEG-Cl~-作用下,在电结晶刚开始时成核机理符合三维瞬时成核,但是过一段时间后,成核机理逐渐转变为连续成核,与Cl~-的成核机理基本一致。SEM的表征结果可以证明MPS或者MPS-Cl~-作用下,铜的电结晶仍符合三维瞬时成核机理。EIS的实验结果表明随着极化电位的增加,会减小MPS或者MPS-PEG对铜电沉积的阻化作用,增大MPS-Clˉ或MPS-PEG-Clˉ对铜电沉积的促进作用。不同添加剂作用下的EIS都显示在增加极化电位的情况下,高频端的容抗弧直径减小,反应电阻减小。更多还原

【Abstract】 Copper is a preferred material for the fabrication of interconnect structures in integrated circuits because of its lower resistivity and superior electromigration properties than aluminium. Electrochemical deposition is a simple technique to realize copper superfilling in the micron- or submicron-size trench of chip due to the presence of organic and inorganic additives in the electrolyte. The most commonly additives employed are 3-mercapto-1-propanesulfonate sodium salt (MPS) or bis-(3-soldiumsulfopropyl disulfide) (SPS), polyethylene glycol (PEG) and chloride ions (Cl~-). In this work, the influence of MPS, PEG, Cl~- and their synergistic effect on the copper electrodeposition on a glass carbon electrode (GCE) from CuSO4-H2SO4 electrolytes were studied by using cyclic voltammetry (CV), linear sweep voltammetry(LSV), chronoamperometry(CA), AC impedance and scanning electron microscopy (SEM) techniques.The experiment results of CV, LSV and EIS indicated that MPS inhibited copper electrodeposition. And the inhibition effect became stronger with the increase of MPS concentration. In the presence of MPS-Cl~-, the cathodic potential peak of CV curves shifted to positive direction. The LSV curves positive shifted and the charge transfer resistance became smaller compared to with Cl~- ions alone. These results indicated that MPS-Cl~- had a significant acceleration on copper electrodeposition and the acceleration was greater than the Cl~- ions. Moreover, the accelerated effect of MPS-Cl~- became stronger with the increase of MPS concentration. MPS-PEG had a stronger inhibition than either MPS or PEG. The inhibition effect of MPS-PEG became stronger with the increase of MPS concentration. The copper electrodeposition was accelerated in the presence of MPS-PEG-Cl~-. And the acceleration effect of MPS-PEG-Cl~- became stronger with the increase of MPS concentration.The experiment results of CA and SEM indicated that MPS accelerated the electrocrystallization process of copper and the nuclear number density was increased with the increase of MPS concentration. MPS-Cl~- could increase both the nuclear number density and Cu2+ diffusion coefficient. However, the nuclear number density decreased with the increase of the concentration of MPS in electrolytes with MPS-PEG. The nuclear number density increased with the increase of MPS concentration in electrolytes with MPS-PEG-Cl~-. The diffusion coefficient of Cu2+ did not changed observably in solution with MPS and MPS-PEG.The experiment results of CA demonstrated that copper electrocrystallization from the 0.05 M CuSO4-0.5 M H2SO4 electrolytes either with or without MPS followed instantaneous nucleation with three-dimensional growth. The addition of MPS-PEG did not change the nucleation mechanism, and still followed the instantaneous nucleation with three-dimensional growth. In the presence of MPS-Cl~- or MPS-PEG-Cl~-, the nucleation mechanism was 3-dimentional instantaneous nucleation during the early short time of electrocrystallization, and then it changed to 3-D progressive nucleation gradually in the late stage of electrocrystallization. The experiment results of SEM demonstrated that copper electrocrystallization from the 0.05 M CuSO4-0.5 M H2SO4 electrolytes with MPS or MPS-Cl~- followed 3-D instantaneous nucleation.EIS results showed the inhibition effect of MPS or MPS-PEG on copper electrodeposition was reduced with the increase of polarization potential. Whereas the promoting function of MPS-Cl~- or MPS-PEG-Cl~- on copper electrodeposition was enhanced with the increase of polarization potential. The reaction resistance of copper in electrolytes with any additive packages decreased with the increase of polarization potential.更多还原