Silicon surface roughness improvement during plasma etch

To reduce etch depth loading in shallow trench isolation and deep trench isolation etch, excess oxygen is added to slow down the etch rate in large opening area. The approach often causes surface roughness problem in large open area. This paper studies the surface roughness mitigation in STI etch with $\mathrm{C}1_{2}/\mathrm{O}_{2}$ plasma through a comparison experiments conducted with a NAURA poly etcher. Results show that high BRF/SRF power ratio with low pressure could reduce surface roughness. However it cannot resolve the issue completely. By using synchronous pulsing plasma, we can significantly reduce open area surface and micro-trenching compare with traditional continuous wave (CW) plasmas.