SILICON-ON-INSULATOR DEVICE ISLANDS FORMED BY OXYGEN IMPLANTATION THROUGH PATTERNED MASKING LAYERS

Separation by implanted oxygen is recognized as a versatile technology to produce silicon-on-insulator substrates. The lateral isolation of device islands is achieved by subsequent local oxidation or mesa etching of the silicon top layer. In an alternative approach, implantation is performed through patterned masking layers leading to a continuous but nonplanar buried oxide. Thereby, total dielectric isolation (vertical and lateral) of the device island is achieved in a single implantation stage. The masking structures used in this investigation are thermal oxides and polycrystalline silicon layers with window openings as well as patterned wafers formed by local oxidation of the bulk silicon wafers. Oxygen was implanted with energies of 100 and 200 keV to doses up to 2.2 x 10(18) O+ cm-2. The resulting structures are studied by cross-sectional scanning electron microscopy and transmission electron microscopy and the effects of mask material and implantation energy are discussed.