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针对抛光垫的使用寿命对铜膜平均去除速率一致性的影响进行研究,同时采用实时表面形貌控制(RTPC)技术,对抛光过程中,铜膜表面形貌进行实时监控。实验结果表明:抛光垫的使用寿命对铜膜化学机械抛光(CMP)平均去除速率影响很大,使用前期(抛光垫使用时间Tt≤500 pcs),铜膜平均去除速率稳定,粗抛一致性良好(片内非均匀性(WIWNU)为3.37%),粗抛后剩余膜厚范围小于60 nm。使用后期(Tt>500 pcs),粗抛速率一致性较差,粗抛后剩余膜厚范围大于100 nm。抛光垫修整能有效恢复抛光垫表面状态,采用在线同步修整技术,可以延长抛光垫使用寿命到750 pcs以上。但是过长的修整时间不能保证铜膜良好的平均去除速率一致性,也会加大抛光垫磨损,降低使用寿命。
The effect of the service life of the polishing pad on the uniformity of the average removal rate of the copper film was studied, and the real time surface topography (RTPC) technology was used to monitor the surface morphology of the copper film during the polishing process. The experimental results show that the service life of the polishing pad has a great influence on the average removal rate of copper chemical mechanical polishing (CMP). In the pre-use period (polishing pad use time Tt≤500 pcs), the average copper removal rate is stable and the rough consistency is good (3.37% on-chip inhomogeneity (WIWNU)), and the remaining film thickness after rough throwing is less than 60 nm. In the late stage of application (Tt> 500 pcs), the consistency of coarse throwing rate is poor, and the remaining thickness range after rough throwing is larger than 100 nm. Polishing pad trimming can effectively restore the surface condition of the polishing pad and can be extended to 750 pcs or more using on-line simultaneous trimming. But too long dressing time can not guarantee the copper film a good average removal rate consistency, will also increase the polishing pad wear and reduce service life.