Dry etching and boron diffusion of heavily doped high-aspect ratio Si trenches

Wen Han Juan; Jason W. Weigold; Stella W. Pang

doi:10.1117/12.251222

23 September 1996 Dry etching and boron diffusion of heavily doped high-aspect ratio Si trenches

Wen Han Juan, Jason W. Weigold, Stella W. Pang

Proceedings Volume 2879, Micromachining and Microfabrication Process Technology II; (1996) https://doi.org/10.1117/12.251222
Event: Micromachining and Microfabrication '96, 1996, Austin, TX, United States

Abstract

The deep etch-shallow diffusion process has been applied to the fabrication of comb drive resonators and micromirrors successfully. Etch rate of Si with various doping concentrations in a Cl₂ plasma generated by an electron cyclotron resonance source and B diffusion in high aspect ratio Si trenches were characterized. It was found that lightly B and P doped Si were etched at similar rates of 0.17 micrometers/min, whereas heavily B doped p⁺⁺Si had a slower etch rate of 0.16 micrometers/min and heavily P doped n⁺⁺Si had faster etch rate of 0.31 micrometers/min. Typical etch conditions are 100 W microwave power and 100 W rf power at 3 mTorr, with 20 sccm of Cl₂ flow and a source to sample distance of 8 cm. The difference between the p⁺⁺ and n⁺⁺Si rate was more significant when etched at higher microwave power, higher rf power, or higher temperature. The depth of a heavily B doped Si layer was measured for different feature sizes, trench openings, and aspect wide trenches to 1.5 micrometers at the bottom of 2 micrometers wide trenches. The diffusion layer on the sides of the trenches for a 30 min B diffusion was 3.25 micrometer thick and it is independent of the trench opening and the trench aspect ratio.

Citation Download Citation

Wen Han Juan, Jason W. Weigold, and Stella W. Pang "Dry etching and boron diffusion of heavily doped high-aspect ratio Si trenches", Proc. SPIE 2879, Micromachining and Microfabrication Process Technology II, (23 September 1996); https://doi.org/10.1117/12.251222

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