Implementation of contact hole patterning performance with KrF resist flow process for 80nm DRAM application

Currently, 193nm lithography including contact hole patterning is being integrated into manufacturable process at 80nm technology nodes. However, for 193nm contact hole patterning, many researchers have reported various troubles such as poor profiles, low exposure dose, and pattern edge roughness due to inherent flaws of ArF resist materials. Also, it is desirable to be extended the KrF lithography at a cost. Of course, the patterning of very small contact hole features for the 80nm DRAM device generation will be a difficult challenge for 248nm lithography. 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 80nm DRAM device generation. In KrF 0.80NA scanner, resist flow process and layout optimization was carried out to achieve the contact hole patterning. The contact CD at best focus is 140nm and the amount of photoresist flow is approximately 52nm. For a contact hole with CDs of 88nm +/- 10%, Focus-Exposure windows over the wafer are 0.3um and 10%, respectively. In conclusion, we have successfully achieved the contact hole patterning with KrF resist flow process for 80nm DRAM device.