Etching for 0.15-µm-Level Patterns with Low Microloading Effect Using Beam Plasmas Generated by Gas Puff Plasma Sources

Microloading effects in high-density plasmas, which typically appear as a difference in the etch rates between the outermost space and the inner space in a line-and-space (L&S) pattern, were investigated using numerical simulations of ion trajectories and ion fluxes incident on the patterned surfaces, taking into account the effects of electrical properties of the materials, plasmas flowing to a wafer and local charging on the patterned surface. The simulation results showed that decrease of the incident ion flux densities were particularly enhanced in the area around the outermost space in the L&S pattern. Moreover, the difference in the incident ion fluxes among the patterns was reduced with increase of the drift velocities of the plasmas. Moreover, experiments on etching of fine patterns on the scale of around 0.15 µ m were also performed using chlorine beam plasmas with high drift velocities generated by gas puff plasma sources. The etch rate of poly-Si stayed nearly constant with decrease of pattern sizes from 1.0 to 0.15 µ m for time-averaged pressure of =0.2 m Torr in the specimen chamber.