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研究了一种0.13μm嵌入式闪存产品量产中常见的由于后段主要金属层互连短路引起的闪存电路读取数值失效的案例。通过采用电学失效分析和物理失效分析,成功观察到了含Cu成分较高的θ相(Al2Cu)在阻挡层TiN与Al-Cu金属薄膜界面处析出,导致Ti N刻蚀被阻止。由于Al-Cu物理气相沉积(PVD)时作业腔内的硅片表面温度接近350℃,推测θ相(Al_2Cu)的形成是硅片表面温度偏低所导致的。基于上述假设提出一个优化的Al-Cu物理气相沉积工艺方案,通过提高作业腔中硅片表面温度避免θ相生成。实验结果表明,新的工艺方案可以有效避免θ相(Al_2Cu)形成,并能解决金属互连短路的问题。
A case study of a numerical failure of a flash memory circuit readout caused by the short-circuit of the main metal layer in the back-end section of a common 0.13-μm embedded flash memory product was investigated. By using electrical failure analysis and physical failure analysis, it was successfully observed that θ phase (Al2Cu) with high Cu content precipitated at the interface between the TiN and Al-Cu metal films, which prevented the TiN etching from being blocked. As the surface temperature of the silicon wafer in the work chamber near Al-Cu physical vapor deposition (PVD) approaches 350 ℃, it is inferred that the formation of θ phase (Al 2 Cu) is caused by the low surface temperature of the silicon wafer. Based on the above assumptions, an optimized Al-Cu physical vapor deposition process is proposed to prevent the formation of θ phase by increasing the surface temperature of the silicon wafer in the working chamber. The experimental results show that the new process scheme can effectively prevent the formation of θ phase (Al 2 Cu) and solve the problem of metal interconnection short circuit.