Isolation structure for semiconductor integrated circuit substrate
View Patent ↗Isolation regions for semiconductor substrates include dielectric-filled trenches and field oxide regions. Protective caps of dielectric materials dissimilar from the dielectric materials in the main portions of the trenches and field oxide regions may be used to protect the structures from erosion during later process steps. The top surfaces of the isolation structures are coplanar with the surface of the substrate. Field doping regions may be formed beneath the field oxide regions. To meet the demands of different devices, the isolation structures may have varying widths and depths.
1. An isolation structure formed in a semiconductor substrate, the isolation structure comprising a trench formed in the substrate, the trench comprising a mixture of a first dielectric material and a second dielectric material, the proportion of the second dielectric material in the mixture increasing with decreasing depth in the trench, wherein the second dielectric material is relatively more resistant to removal by normal semiconductor etch processes as compared with the first dielectric material.
2. The isolation structure of claim 1 wherein the second dielectric material comprises silicon nitride.
3. The isolation structure of claim 2 wherein the first dielectric material comprises silicon oxide.