Controlled chemical mechanical polishing of polysilicon and silicon dioxide for single-electron device.

In this article, the authors report experimental results of the chemical mechanical polishing (CMP) of silicon dioxide (SiO₂) and polysilicon to produce nanoscale features with very smooth surfaces. The sizes of the features polished ranged from 30 to 500 nm. For polysilicon polishing, the nanostructures were defined in positive tone e-beam resist and the pattern was transferred to the oxide substrate using reactive ion etching. These etched nanostructures (70 nm deep trenches) were conformally filled with low pressure chemical vapor deposited polysilicon and polished using a CMP system. Polishing planarized the sample and removed the polysilicon overburden to expose the filled trenches in the SiO₂. The polished structures were studied using scanning electron microscopy (cross sections) and atomic force microscopy (surface). The authors report controllable CMP to realize ∼20 nm thick layers after polishing, with rms roughness of ∼0.3 nm. Better control of the CMP process (few nm/min removal rate) was demonstrated by using diluted slurry or pure de-ionized water as the CMP slurry. [ABSTRACT FROM AUTHOR]