High-resistivity silicon surface passivation for the thin-film MCM-D technology

High-resistivity silicon (HRSi) has excellent properties as substrate material to integrate microwave passive components. However, the existence of a layer of free surface charges under the silicon-silicon dioxide interface generated by impurities in the SiO₂ and in the interface itself undermines the RF properties of the bulk HRSi. This paper demonstrates how the surface charges increase the RF loss of CPW lines processed on HRSi and make their loss DC dependent. It also presents how Ar implantation can successfully restore the excellent RF properties of the bulk HRSi in terms of loss and DC dependency. The temperature stability of this technique is also studied and proved to withstand temperatures up to 300degC, which is sufficient for Imec´s MCM-D technology implementation