Trench polysilicon diode

• US 7,612,431 B2
• Filed: 01/17/2008
• Issued: 11/03/2009
• Est. Priority Date: 12/28/2005
• Status: Active Grant

• Current Assignee: Vishay Siliconix
• Original Assignee: Vishay Siliconix
• Inventors: Pattanayak, Deva, Terrill, Kyle, Chen, Qufei, Xu, Robert
• Primary Examiner(s): Tran; Long K
• Application Number:
  US12/009,379
• Publication Number:
  US 20080135872A1
• Time in Patent Office: 656 Days
• Field of Search: 438/141, 438/983, 438/197, 438/206, 438/270, 438/212, 438/268, 438/272, 257/E21.355, 257/E21.356, 257/E21.357, 257/E21.358, 257/288, 257/341, 257/342, 257/355, 257/594, 257/173, 257/175, 257/328
• US Class Current: 257/594
• CPC Class Codes: H01L 27/0255 using diodes as protective elements
• CPC Class Codes: H01L 27/0629 in combination with diodes, or resistors, or capacitors
• CPC Class Codes: H01L 27/0814 Diodes only
• CPC Class Codes: H01L 29/16 including, apart from doping materials or other impurities, only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 29/66106 Zener diodes
• CPC Class Codes: H01L 29/66136 PN junction diodes
• CPC Class Codes: H01L 29/66727 with a step of recessing the source electrode
• CPC Class Codes: H01L 29/66734 with a step of recessing the gate electrode, e.g. to form a trench gate electrode
• CPC Class Codes: H01L 29/7808 the other device being a breakdown diode, e.g. Zener diode
• CPC Class Codes: H01L 29/7813 with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236
• CPC Class Codes: H01L 29/866 Zener diodes
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

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.

Claims

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.