Stability of HSQ nanolines defined by e-beam lithography for Si nanowire field effect transistors
SEM 45° tilted view of HSQ lines in four stability states: (a) stable, (b) clustering or grouped collapsed lines, (c) completely collapsed lines forming free ribbons on the surface, (d) wavy lines with a spatial wavelength of ; and (e) wide lines of pitch and aspect ratio of 11. Scale bar in images (a)–(d) is .
Critical aspect ratio as a function of (a) grating pitch and (b) e-beam exposure dose for HSQ lines of three thicknesses: 60, 130, and .
Oxygen content in thick HSQ squares on Si as a function of area dose.
Schematic of line instability model combining the effect of capillary forces and swelling strain.
Swelling strain of wavy HSQ lines of thickness as a function of line dose.
(a) Schematic of the fabrication process of Si nanowire FETs. (b) atomic force microscopy image of HSQ lines crossing the gap between two Cr pads, showing the line peeling-off problem; scale bar is . (c) HSQ lines across the step of Cr pads without instability issues; scale bar is . (d) curve of SiNW FETs with wide, long Si channels. The device contains 12 lines crossing the gap and source-drain bias is . (e) curve of the same device with several different .
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