Auxiliary mechanism of in-situ micro-nano bubbles in oxide chemical mechanical polishing

Silicon dioxide is the most important gate oxide dielectric material, and its surface planarization is an important factor in the continuous shrinking of the size of integrated circuits. Developing a novel chemical mechanical polishing auxiliary technique to achieve efficient polishing of oxide wafers is a significant challenge. In this study, a novel in-situ micro-nano bubbles auxiliary method, which used a nano-hydrophobic film to prepare a gas supersaturated slurry that can generate instant in-situ micro-nano bubbles during polishing, was developed for oxide wafers. Compared with conventional slurries, this auxiliary method increased the material removal rate by about 30% and ensured the low surface roughness of the wafer of 0.14 nm. The existence of micro-nano bubbles and the multi-size distribution and zeta potential of the micro-nano bubbles were measured by optical microscope and dynamic light-scattering methods. Then, to investigate the auxiliary mechanism of this in-situ micro-nano bubbles, different analytical methods, such as oxide thickness measurement system, scanning electron microscopy, Fourier transform infrared spectroscopy, and atomic force microscopy, were used to characterize the sample. The results indicated that during the polishing process, the micro-nano bubbles generated in situ have a good cleaning effect. In addition, the free radicals generated after in-situ micro-nano bubbles burst simultaneously modified the surfaces of the wafer and the pad. The improvement of the adsorption between the wafer and abrasives promoted the chemical reaction between them. After conditioning, the rougher and cleaner pad had a higher mechanical effect. Most importantly, this in-situ micro-nano bubbles auxiliary method has the potential to be applicable to all slurries.