The application of reticle analyzer in DRAM fab

Abstract

In modern advanced IC fabs, reticle management is essential for process control and yield management, since any reticle issue can potentially impact thousands of wafers, resulting in a huge economic loss. For reticle caused issues, the possibility of human mistakes made in defect disposition has dramatically increased as the defects on reticles become more complicated. The difficulty in defect disposition originates from smaller critical dimension (CD) and complex pattern designs like aggressive OPC and SRAF. Conventionally, defect disposition after reticle inspection is done by operators or engineers, and defects are evaluated based on engineers’ experience or AIMS tool, which are high risk and time-consuming methods. Use of automated defect disposition solutions has been reported in some photomask shops, but in DRAM fabs, an efficient and accurate defect disposition system is not yet present. In collaboration with KLA, Changxin Memory Technology (CXMT) accessed and utilized KLA’s Reticle Analyzer (RA), an intuitive web-based analysis interface that integrates Automatic Defect Classification (ADC), Lithographic Printability Review (LPR), and Defect Progress Monitor (DPM) to overcome reticle defect disposition difficulties. The comprehensive analytics tool systematically disposes all defects detected by KLA reticle inspection systems, eliminating human error in defect classification and providing 99.5% accuracy without under-classifying any defects. Furthermore, CXMT studied the LPR solution for multiple critical layers with programmed-defect masks, then verified the simulated LPR results in CD error (CDE). The correlation between LPR results and wafer printing results shows accurate CDE prediction in high volume production. Additionally, DPM was used to generate statistical process control like charts for reticle defectivity. This study shows that the integrated RA software offers a modern solution for wafer fabs that automates reticle defect management and shortens time to decision for engineers.