SILICON-NITRIDE CHEMICAL-MECHANICAL POLISHING MECHANISMS

To elucidate the fundamentals of chemical mechanical polishing (CMP) o f silicon nitride, low pressure chemical vapor deposited silicon nitri de is analyzed by X-ray photoelectron spectroscopy and Fourier transfo rm infrared spectroscopy both before and after CMP, demonstrating the salient increase of oxygen content, amine species, and silanol groups forming on the nitride surface. In addition, chemical testing of the c ollected slurry identifies ammonia as one of the nitride reaction prod ucts during CMP. Nitride hydrolysis is proposed as the dominant chemic al reaction, through which the nitride surface is chemically modified and softened, enabling continuous material removal with a process that achieves atomic-scale surface smoothness. Moreover the nitride polish rate can be promoted or suppressed through the modulation of the nitr ide hydrolysis.