Cu互连层表面无应力平坦化加工技术基础研究

Pulse electrochemical polishing is proposed for copper interconnection layer surface stress free planarization, due to the peeling and surface damage of insulation layer material in copper interconnection layer chemical mechanical polishing. Being most studies discuss the technological rule from the relations between the experimental parameters and machining effect and are lack of deep mechanism research, it is proposed that the pulse current is applied to regulate the passive film characteristics and control the anode surface material removal for obtaining high surface quality. From the influence mechanism of the pulse current to the passive film characteristics, the internal relations of "the action of the pulse curent-anodic polarization-mass transfer process-passive film characteristics-the effect of electrochemical finishing-anode material removal rule" are obtained in order to indicate the controllable removal mechanism of anode surface. It is statistically analyzed that the influence rule of the passive film characteristics evolution to the anode surface removal under condition of pulse current. The relational model between the pulse current parameters and the anode surface removal is established. The mathematical model of the relationship between controllable pulse current parameters and the removal is established and the controllable rule of the pulse current parameters of the expected surface quality is obtained. The process optimization is studied, which ensure the requirements of surface quality. The results have important significance for enriching precision and ultraprecision theory and techniques.

针对目前铜互连层化学机械抛光存在的绝缘层材料界面剥离和表面损伤等质量问题，提出将脉冲电化学方法引入铜表面无应力平坦化加工。针对现有研究大多从实验参量和加工效果间关系角度探讨工艺规律，而对中间过程缺乏深层次的机理性研究现状，提出脉冲电流调控钝化膜特性进而调控阳极表面材料去除规律，获得高质量的阳极表面光整方法。从研究脉冲电流对阳极表面状态的影响机制入手，分析脉冲电流对阳极极化行为、传质过程机制进而对阳极表面电流分布的影响规律，获得"脉冲电流-阳极极化-传质过程-钝化膜特性-电化学作用效果-阳极材料去除规律"的内在联系，揭示阳极材料可控去除机理；统计分析脉冲电流作用条件下，钝化膜特性演化对阳极表面去除量的影响规律，建立脉冲参量和表面去除量之间的关联模型，获得预期表面质量条件下可控脉冲参量的控制规律；研究保证表面质量要求条件下的工艺优化。研究结果对丰富精密及超精密加工理论与技术具有重要意义。

针对目前铜互连层化学机械抛光存在的绝缘层材料界面剥离和表面损伤等质量问题，将脉冲电化学方法引入铜表面无应力平坦化加工。分析了脉冲电压、占空比、频率，极间间隙，加工时间，电解液成分及溶液温度等对阳极表面材料去除的影响规律。采用正交实验方法分析了脉冲参量对阳极极化行为、传质过程的影响规律，获取了最优工艺参量，建立了脉冲参量和表面去除量之间的关联模型，分析了去除量的稳定性和敏感性特征。在选取的优化参量条件下，将铜表面粗糙度从原有Ra153nm降低至Ra37nm。