Intra field CD uniformity correction by Scanner Dose MapperTM using Galileo® mask transmission mapping as the CDU data source

Intra-field CD variation can be corrected through wafer CD feedback to the scanner in what is called the Dose Mapper (DOMA) process. This will correct errors contributed from both reticle and scanner processes. Scanner process errors include uncorrected illumination non uniformities and projection lens aberration. However, this is a tedious process involving actual wafer printing and representative CD measurement from multiple sites. A novel method demonstrates that measuring the full-field reticle transmission with Galileo® can be utilized to generate an intensity correction file for the scanner DOMA feature. This correction file will include the reticle transmission map and the scanner CD signature that has been derived in a preliminary step and stored in a database. The scanner database is periodically updated after preventive maintenance with CD from a monitoring reticle for a specific process. This method is easy to implement as no extra monitoring feature is needed on the production reticle for data collection and the new reticle received can be immediately implemented to a production run without the need for wafer CD data collection. Correlation of the reticle transmission and wafer CD measurement can be up to 90% depending on the quality of CD data measurements and repeatability of the scanner signature. CD mapping on the Galileo® tool takes about 20 minutes for 1500 data points (there is no limit to the number of measurement point on the Galileo®), which is more than enough for the DOMA process. Turn Around Time (TAT) for the whole DOMA process can thus be shortened from 3 Days to about an hour with significant savings in time and resources for the fab.