Back-gated buried oxide MOSFETs in a high-voltage bipolar technology for bonded oxide/SOI interface characterization

A novel back-gated P-MOSFET structure is fabricated in a high-voltage complementary bipolar technology using BESOI (bonded etch back SOI) substrates. The P+ buried layer regions, used for the PNP BJT are used as the source and drain regions, the N- epi as the channel region, the silicon handle wafer as the gate, and the BOX (buried oxide) as the gate oxide. The P-MOSFET was used to characterize the interface between the BOX and the SOI. The devices exhibit high sub-threshold slope which is attributed to a high interface state density of about 2/spl times/10/sup 12//cm/sup 2/ at the bonding interface. Bias-temperature stress measurements show an effective mobile charge density of 4/spl times/10/sup 10//cm/sup 2/ in the buried oxide.