In Situ Remote H-Plasma Cleaning of Patterned si-SiO₂ Surfaces

A RF H-plasma exposure was used to clean the surface of Si-SiO₂ patterned wafers. The areal coverage of SiO₂ to bare Si was 4 to 1, and the patterns were long strips, small squares, and large open regions. The plasma-surface etching was monitored by residual gas analysis (RGA). The RGA spectra indicated etching of the Si surface at temperatures below 400°C and no detectable by-products due to interactions with the SiO₂ regions for temperatures ˂450°C. The patterned surfaces were characterized with low energy electron diffraction (LEED) (from the bare Si regions) and atomic force microscopy (AFM). The LEED patterns indicate 1 X 1 and 2 x 1 surface symmetries at 300 and 450°C, respectively. The sharpness of the LEED patterns as well as the 2x1 reconstruction indicated that the H-plasma cleaned the bare Si regions. In addition, AFM measurements indicated that the Si and SiO₂ surface rms roughnesses do not vary significantly due to the H-plasma exposure. It can be concluded from the RGA and AFM data that the remote H-plasma process at 450°C cleaned the surface and did not significantly react with either the Si or SiO₂ regions.