Improving monocrystalline silicon surface quality with chemical mechanical polishing using the slurry with the additive of isopropanol

Enhancing the silicon surface smoothness with chemical mechanical polishing (CMP) is crucial to achieve better beam quality in X-ray systems. The additive in CMP slurry is the key factor in determining the resulting surface morphology. This paper exploits the effect of isopropanol (IPA) additive on regulating the material removal process and resulting microscopical surface morphology through varying the IPA concentration and polishing pressure. The improvement of surface quality and a dropping material removal rate (MRR) are obtained by increasing the IPA concentration from 0.1 to 2.5 mol/L. When the polishing pressure increases from 0.25 to 0.48 psi, a better surface quality and enhanced MRR are observed. By using the optimal polishing pressure of 0.48 psi and IPA concentration of 2.5 mol/L, the root-mean-square roughness can be reduced to 0.10 nm under a measurement area of 1 µm × 1 µm with atomic force microscopy, more than 58.3% lower compared to surfaces polished without IPA. This work suggests an approach to obtain the ultra-smooth silicon mirrors, which has promising applications in the field of X-ray, aerospace, and photovoltaics.