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

Abstract

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 SiO 2 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 300°C, which is sufficient for Imec's MCM-D technology implementation.

Rapid Thermal Treatment for Improving Thermal Processing Stability of Ar-Implanted Surface Passivated High-Resistivity Silicon

“…Although attenuation of the unimplanted CPW line was stable after high temperature annealing, a large dc-voltage dependence was observed (not shown) [8]. For a p-type Si substrate, a positive bias voltage leads to an inversion layer underneath the interface of a MOS structure.…”

“…The attenuation of the unimplanted CPW line (sample A) was about 1.7 dB/cm at 30 GHz while those of the implanted CPW lines (samples B, E) were about 0.7 dB/cm at 30 GHz. The silicon substrates were damaged by ion implantation, thus generating traps [8]. These traps capture mobile carriers near the surface of the substrate.…”

Microstrip thin-film MCM-D technology on high-resistivity silicon with integrated through-substrate vias

“…Therefore, this technique eliminates the additional loss introduced by the charges [5], [6]. The authors have previously demonstrated that the surface of the HRSi remains passivated after the thin-film processing [7], [8] and therefore it is the passivation technique used in the wafers subject of this study. Fig.…”