Uniformity and sheet resistance of flat polysilicon by experimental approach

Abstract

The requirement for uniform polysilicon resistance for devices that use polysilicon as resistors has increased. Among the several poly-deposition processes, the flat-polysilicon process is known to be the most effective process to improve the uniformity of polysilicon resistance. In this paper, the flat-polysilicon process was evaluated to improve the polysilicon-resistance uniformity for devices using polysilicon for resistors. The results from the flat-polysilicon process showed improved thickness uniformity, compared with those for normal-temperature tilted polysilicon, and improved 1sigma sheet-resistance uniformity. The temperature tilted normal polysilicon with single injector produced a 6.35% sheet. resistance uniformity (1sigma), while the flat polysilicon with 3 injectors resulted in a below-0.40% sheet-resistance uniformity (1sigma). By using the experimental data, correlation analysis between sheet resistance and thickness was performed.