A Nanocrystalline Silicon Surface-Passivation Layer on an HR-Si Substrate for RFICs

In this letter, a thin nanocrystalline silicon (nc-Si) layer grown by hot-wire chemical vapor deposition is used as a surface-passivation layer (SPL). The transmission loss αTL of coplanar waveguide lines on an oxide-coated high-resistivity silicon substrate with a 100-nm-thick nc-Si SPL is less than 1.05 dB/cm at frequencies up to 20 GHz. Furthermore, we found that the very thin nc-Si SPL is also greatly effective for reducing crosstalk noise and further enhancing the isolation characteristics of electrical circuits. Therefore, an nc-Si SPL is capable of providing good surface passivation for RF IC applications.