Implementation of contact hole patterning performance with KrF resist flow process for 60nm node DRAM application

Small contact holes are the most difficult structures for microlithography to print because it is sensitively affected by the process condition, pattern density and environment as well. Moreover, the patterning of very small contact hole features for the 60nm node DRAM device generation will be a difficult challenge for 248nm lithography. However, we have already demonstrated the applicability of thermal flow resist to print 80nm contact holes for DRAM device using 248nm lithography in previous studies. In this work, we study the potential for contact photoresist reflow to be used with 248nm photoresist to increase process windows of small contact dimensions at the 60nm node DRAM device generation (0.21 k1). With KrF 0.80NA scanner, resist flow process and layout optimization were carried out to achieve the contact hole patterning. And also the exposure condition was optimized. For a contact hole with CDs of 69nm +/- 10%, Focus-Exposure windows over the wafer are 0.25μm and 8%, respectively. In conclusion, we have successfully achieved the contact hole patterning with KrF resist flow process for the 60nm node DRAM device.