Optimization of scatterometry parameters for Shallow Trench Isolation (STI) monitor

摘要

In recent years scatterometry has been shown to demonstrate very impressive long term repeatability of better than 1.5nm when measuring a simple resist stack. However, does this impressive precision hold true for a more complicated stack such as that of Shallow Trench Isolation (STI)? Furthermore what benefits does scatterometry metrology bring compared to CD-SEM and X-SEM metrology for STI characterization and monitoring? In this work, we examine the impact of critical attributes fundamental to scatterometry metrology, such as grating parameter sensitivity and library optimization, for the STI layer of a CMOS process using KLA-Tencor's SpectroscopicCD~(TM). We report the results from an optimized library to characterize the STI process after trench etch and the sensitivity of the metrology will also be discussed. Finally, the efficiency of this technique is demonstrated by reference to the monitoring results for a period of approximately five months.