Nanocrystalline silicon thickness dependence of transmission characteristics of CPWs on surface-passivated high-resistivity silicon substrates

A nanocrystalline silicon (nc-Si) layer was used as a surface-passivation layer (SPL) on a high-resistivity silicon (HR-Si) substrate. The transmission loss (alpha(TL)) of coplanar waveguide (CPW) lines on oxide/SPL/HR-Si substrates with an nc-Si SPL of 100, 200, and 400 nm was measured and analysed. The experimental results demonstrate that the thicker nc-Si SPL provides better passivation effect and the alpha(TL) can be down to 0.69 dB/cm. The equivalent series resistance and shunt conductance were extracted to investigate the dependence of alpha(TL) on the SPL thickness. The cross-talk effect of CPWs on oxide/SPL/HR-Si substrates was also studied.