Isolated diode
View Patent ↗Various integrated circuit devices, in particular a diode, are formed inside an isolation structure which includes a floor isolation region and a trench extending from the surface of the substrate to the floor isolation region. The trench may be filled with a dielectric material or may have a conductive material in a central portion with a dielectric layer lining the walls of the trench. Various techniques for terminating the isolation structure by extending the floor isolation region beyond the trench, using a guard ring, and a forming a drift region are described.
1. An isolated diode formed in a P-type semiconductor substrate, the substrate not comprising an epitaxial layer, the isolated diode comprising:
an N-type floor isolation region submerged in the substrate;
a trench extending from a surface of the substrate at least to the floor isolation region, the trench having a central portion filled with a conductive material and a dielectric material lining the walls of the trench, the conductive material providing electrical contact from the floor isolation region to the surface of the substrate, the trench and the floor isolation region together forming an isolated pocket of the substrate; and
a P-type anode region in the isolated pocket, the anode region extending from the surface of the substrate to the floor isolation region, the anode region comprising a shallow portion and a deep portion, the shallow portion being located adjacent the surface of the substrate, the deep portion being located below the shallow portion, the shallow portion having a first doping concentration, the deep portion having a second doping concentration, the second doping concentration being greater than the first doping concentration.
2. The isolated diode of claim 1 comprising:
a dielectric layer above the surface of the substrate, the dielectric layer having a first opening above the anode region and a second opening above the conductive material;
an anode contact in the first opening in contact with the anode region; and
a cathode contact in the second opening in contact with the conductive material.
3. The isolated diode of claim 1 wherein the deep portion of the anode region forms a junction with the floor isolation region.