TRENCH MOSFET WITH ESD TRENCH CAPACITOR

• US 20080042208A1
• Filed: 05/16/2007
• Published: 02/21/2008
• Est. Priority Date: 08/16/2006
• Status: Abandoned Application

• Current Assignee: Force Mos Technology Co., Ltd.
• Original Assignee: Force Mos Technology Co., Ltd.
• Inventors: Hshieh, Fwu-Iuan
• Application Number:
  US11/749,391
• Publication Number:
  US 20080042208A1
• Time in Patent Office: Days
• US Class Current: 257/360
• 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 29/41766 with at least part of the source or drain electrode having contact below the semiconductor surface, e.g. the source or drain electrode formed at least partially in a groove or with inclusions of conductor inside the semiconductor H01L29/41733 - H01L29/41758 take precedence
• 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 29/7803 structurally associated with at least one other device assemblies H01L25/00; integrated circuits H01L27/00
• CPC Class Codes: H01L 29/7808 the other device being a breakdown diode, e.g. Zener diode
• CPC Class Codes: H01L 29/7811 with an edge termination structure guard regions per se H01L29/0619; field plates per se H01L29/402
• 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 29/945 Trench capacitors
• 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

An electrostatic discharging (ESD) protected metal oxide semiconductor field effect transistor (MOSFET), an epitaxial layer on substrate; a trench gate structure formed in the epitaxial layer; a source region formed in the substrate near the gate structure; a trench capacitor formed underneath gate metal pad in the epitaxial layer connected between the source region and the gate structure, wherein the trench capacitor acts as an ESD improved element for the MOSFET.

Claims

1. An electrostatic discharging (ESD) protected metal oxide semiconductor field effect transistor (MOSFET), comprising:

an epitaxial layer on substrate;

a trench gate structure formed in the epitaxial layer;

a body and source regions formed in the epitaxial layer surrounding the gate structure in active area; and

a trench capacitor formed underneath gate metal pad in the epitaxial layer connected between the source region and the gate structure,

wherein the trench capacitor acts as an ESD improved element for the MOSFET.

2. The MOSFET of claim 1, further comprising a polysilicon Zener diode formed on the epitaxial layer and connected between the source region and the gate structure.

3. The MOSFET of claim 2, wherein the Zener diode is disposed on the trench capacitor, sandwiched with a thick oxide with thickness greater than 1 KA.

4. The MOSFET of claim 2, wherein when an electrostatic voltage is larger than a breakdown voltage of the Zener diode, the Zener diode passes the electrostatic charge from a gate to a source of the MOSFET.

5. The MOSFET of claim 2, wherein the Zener diode consists of a plurality of doping regions with alternative n+/P+ polarities.

6. The MOSFET of claim 2, wherein inner metal connections are used to connect the Zener diode, the source region and the trench gate structure.

7. The MOSFET of claim 6, wherein the inner metal connections realize metal contacts for the Zener diode, the source region and the trench gate structure by metal plugs.

8. The MOSFET of claim 1, wherein the trench capacitor comprises a plurality of trench structures.

9. The MOSFET of claim 1, wherein the larger the area of electrode plates of the trench capacitor, the better the effect of ESD.

10. The MOSFET of claim 9, wherein the larger the area of the trench capacitor, the larger the area of electrode plates of the capacitor.

11. A method for fabricating an ESD protected MOSFET, comprising:

forming trenches in a epitaxial layer;

forming a body and source regions in the epitaxial layer at both sides of the trenches in active area;

forming an oxide layer covering the epitaxial layer and the trenches;

forming a doped polysilicon layer on the oxide layer and filling the trenches;

removing the polysilicon layer that are on top of the epitaxial layer to form a trench gate structure and a trench capacitor, wherein the oxide layer acts as a gate oxide layer of the gate structure and the dielectric layer of the trench capacitor;

forming an insulating layer on the epitaxial layer, the trench capacitor and the trench gate structure;

forming an undoped polysilicon layer on the trench capacitor;

forming a Zener diode on the polysilicon layer; and

forming metal connections for connecting the Zener diode and the capacitor between the trench gate structure and the source region.

12. The method of claim 11, wherein the trench capacitor comprises a plurality of trench structures.

13. The method of claim 11, wherein the larger the area of electrode plates of the trench capacitor, the better the effect of ESD.

14. The method of claim 13, wherein the larger the area of the trench capacitor, the larger the area of electrode plates of the capacitor.

15. The MOSFET of claim 11, wherein when an electrostatic voltage is larger than a breakdown voltage of the Zener diode, the Zener diode passes the electrostatic charge from a gate to a source of the MOSFET.

16. The method of claim 11, wherein the Zener diode consists of a plurality of doping regions with alternative n+/P+ polarities.

17. The method of claim 11, wherein inner metal connections are used to connect the Zener diode, the source region and the trench gate structure.

18. The method of claim 17, wherein the inner metal connections realize metal contacts for the Zener diode, the source region and the trench gate structure by metal plugs.