Trench polysilicon diode
View Patent ↗Embodiments of the present invention include a method of manufacturing a trench transistor. The method includes forming a substrate of a first conductivity type and implanting a dopant of a second conductivity type, forming a body region of the substrate. The method further includes forming a trench in the body region and depositing an insulating layer in the trench and over the body region wherein the insulating layer lines the trench. The method further includes filling the trench with polysilicon forming a top surface of the trench and forming a diode in the body region wherein a portion of the diode is lower than the top surface of the trench.
1. A trench polysilicon diode comprising electrostatic discharge (ESD) protection comprising:
a N+ (P+) type substrate;
a N− (P−) type epitaxial region over said substrate;
a trench formed in said N− (P−) type epitaxial region, said trench comprising a top surface;
an insulating layer lining said trench;
a polysilicon filling said trench forming a top surface of said trench;
a P+ (N+) type doping polysilicon in said trench and formed by a P+ (N+) type ESD implant;
a N+ (P+) type doping polysilicon in said trench and formed by a N+ (P+) type source implant; and
a diode formed in said trench such that a portion of said diode is formed below said top surface of said trench, wherein said trench comprises an ESD trench.
2. The trench polysilicon diode as described in claim 1 wherein said insulating layer comprises an oxide.
3. The trench polysilicon diode as described in claim 1 wherein said insulating layer in said trench has a breakdown voltage rating greater than a drain-source breakdown voltage of trench MOSFET transistor for excellent isolation between them.
4. The trench polysilicon diode as described in claim 1 wherein said insulating layer is of a few thousand angstroms in thickness and said insulating layer thickness in said trench depends on its breakdown voltage requirement.
5. The trench polysilicon diode as described in claim 1 wherein said diode is formed prior to the formation of a MOSFET trench of said transistor.
6. The trench polysilicon diode as described in claim 1 wherein said diode is a trench diode and is used for temperature sensing.
7. The trench polysilicon diode as described in claim 1 wherein said N+ (P+) type doped polysilicon in said trench is used as a resistor.
8. The trench polysilicon diode as described in claim 1 wherein said diode is a Zener diode.
9. The trench polysilicon diode as described in claim 8 wherein said Zener diode is used for electrostatic discharge protection.
10. The trench polysilicon diode as described in claim 8 wherein said Zener diode is used for a clamping function.