Development of viscous PR flow technology for 0.26 /spl mu/m contact pitch on 0.84 /spl mu/m/sup 2/ SRAM cell [photoresist flow]

The PR (photoresist) flow process for small contact patterning is difficult to predict and optimize because it is sensitively affected by the process condition, pattern density and environment as well. In this paper, a model of viscous flow by surface tension for the PR flow process was presented and the 3D transient flow simulation using CFD-ACE+ (computational fluid dynamics software) was introduced. In the simulation, the effect of temperature on the PR flow and the direction of PR flow by contact size, shape, and surrounding bulk density were taken into account. By using the combined results of PR flow simulation and additional lithography simulation by the Solid-C program, enabled a realization of a uniform contact shape in various environments on a 0.84 /spl mu/m/sup 2/ SRAM cell. This process sequence widened process tolerance on device integration and exhibited an improved contact resistance distribution and reduced junction leakage current.