VLSI金属互连线1／f^γ噪声指数与电迁移失效

Correlation between Frequency Exponent of 1/fγ Noise and Electromigration Failure in VLSI Interconnections

对VLSI的金属互连线实施高应力下的加速寿命试验和常规应力下的噪声频谱测量 ,得到了金属薄膜1/fγ噪声的频率指数γ在电迁移演化过程中的变化规律 ,发现γ指数在寿命试验的某个时间点发生突变 ,从 1 0上升到 1 6以上 .这种突变可以归因于电迁移诱发空洞形成过程的起点 ,因而是金属薄膜结构开始发生不可逆结构变化的标志 .

The accelerated-life tests with high stresses and noise spectrum measurement at normal bias conditions are performed for Al-based interconnection in VLSI, and the variation of frequency exponent γ of 1/fγ noise with the electromigration evolution during the test is observed. It is found that the abrupt change of the exponent γ, from 1.0 to 1.6 above, occurs after a period of the test. The change may be caused by the voids induced by electromigration, and hence the invertible structure variation in the metal thin films starts to be formed at the time. Therefore, the exponent γof 1/fγ noise can be used as an indicator to evaluate the destruction to thin film interconnection induced by electromigration.