Deep submicron device isolation with buried insulator between source/drain polysilicon (BIPS)

A novel isolation technology, called buried insulator between source/drain polysilicon (BIPS), is described. The BIPS isolation structure consists of refilling CVD (chemical vapor deposition) oxides in openings between source/drain polysilicon patterns by double photoresist etchback. A defect- and bird's-beak-free process can be realized by this isolation. Devices with BIPS isolation are compared with LOCOS (local oxidation of silicon) with respect to isolation parasitic effects and current drive capability. A 0.5-μm isolation is achieved, and the narrow channel effects are almost supressed with BIPS isolation. The subthreshold characteristics of devices with BIPS isolation give the same shape value as those for conventional devices with LOCOS isolation. A ring oscillator with BIPS isolation exhibits a propagation delay time of 69 ps/gate.