Trench MOSFET having a top side drain

• US 8,653,587 B2
• Filed: 02/13/2012
• Issued: 02/18/2014
• Est. Priority Date: 02/13/2012
• Status: Active Grant

• Current Assignee: Force Mos Technology Co., Ltd.
• Original Assignee: Force Mos Technology Co., Ltd.
• Inventors: Hsieh, Fu-Yuan
• Primary Examiner(s): Lee, Cheung
• Assistant Examiner(s): JOY, JEREMY J
• Application Number:
  US13/371,496
• Publication Number:
  US 20130207172A1
• Time in Patent Office: 736 Days
• Field of Search: 257/330, 257/E29.262
• US Class Current: 257/330
• CPC Class Codes: H01L 29/0623 Buried supplementary region, e.g. buried guard ring multi-RESURF H01L29/0634
• CPC Class Codes: H01L 29/0661 specially adapted for altering the breakdown voltage by removing semiconductor material at, or in the neighbourhood of, a reverse biased junction, e.g. by bevelling, moat etching, depletion etching
• CPC Class Codes: H01L 29/0878 Impurity concentration or distribution
• CPC Class Codes: H01L 29/407 Recessed field plates, e.g. trench field plates, buried field plates
• 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 29/4236 within a trench, e.g. trench gate electrode, groove gate electrode
• 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 29/7809 having both source and drain contacts on the same surface, i.e. Up-Drain VDMOS transistors
• 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 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

This invention discloses a trench MOSFET comprising a top side drain region in a wide trench in a termination area besides a BV sustaining area, wherein said top side drain comprises a top drain metal connected to an epitaxial layer and a substrate through a plurality of trenched drain contacts, wherein the wide trench is formed simultaneously when a plurality of gate trenches are formed in an active area, and the trenched drain contacts are formed simultaneously when a trenched source-body contact is formed in the active area.

Claims

1. A trench MOSFET having a top side drain comprising:

a substrate of a first conductivity type;

an epitaxial layer of the first conductivity type onto said substrate, wherein said epitaxial layer has a lower doping concentration than said substrate;

an active area comprising a plurality of gate trenches filled with gate material, surrounded by a body region of a second conductivity type, and flanked by a source region of the first conductivity type;

a top side drain formed in a wide trench in a termination area and comprising a top drain metal connected to said epitaxial layer through a plurality of trenched drain contacts each filled with a contact metal plug, wherein said wide trench is formed simultaneously when said gate trenches are formed in said active area;

a BV sustaining area formed in the termination area and adjacent to the top side drain.

2. The trench MOSFET of claim 1 further comprising a sinker region in said epitaxial layer underneath said wide trench, wherein said sinker region is heavily doped with the first conductivity type and reaching the interface between said epitaxial layer and said substrate.

3. The trench MOSFET of claim 1 further comprising a sinker region is said epitaxial layer underneath said wide trench, wherein said sinker region is heavily doped with the first conductivity type and not reaching the interface between said epitaxial layer and said substrate.

4. The trench MOSFET of claim 1, wherein said By sustaining area comprising multiple trenched floating gates formed in multiple floating trenches which are formed simultaneously when said wide trench in said termination area is formed.

5. The trench MOSFET of claim 1, wherein said BV sustaining area comprising a metal field plate atop a body dopant region in said termination area, wherein said body dopant region is of a second conductivity type.

6. The trench MOSFET of claim 1, wherein said BV sustaining area comprising a trenched sidewall spacer close to a sidewall of said wide trench as a filed plate and connected to a source metal which is also connected to a source area and a body region in said active area.

7. The trench MOSFET of claim 4, wherein said By sustaining area further comprising a trenched sidewall spacer close to a sidewall of said wide trench.

8. The trench MOSFET of claim 5, wherein said BV sustaining area further comprising a trenched sidewall spacer close to a sidewall of said wide trench.

9. The trench MOSFET of claim 1, wherein said trenched drain contacts are formed simultaneously when a trenched source-body contact is formed in said active area to connect said source region and said body region to a source metal, as well as when a trenched gate contact is formed in a gate contact area to connect the gate material in a gate contact trench to a gate metal for gate connection.

10. The trench MOSFET of claim 9, wherein said source region in said active area is formed by lateral diffusion, having a higher doping concentration and a greater junction depth along sidewalls of said trenched source-body contact than along an adjacent channel region at a same distance from a top surface of said epitaxial layer.

11. The trench MOSFET of claim 9, wherein said source region in said active area is formed by vertical diffusion, having a same doping concentration and a same junction depth from sidewalls of said trenched source-body contact to an adjacent channel region at a same distance from a top surface of said epitaxial layer.

12. The trench MOSFET of claim 9, wherein said source metal, said gate metal and said top drain metal each comprising Al alloys bounded with Au, Cu or Al wire.

13. The trench MOSFET of claim 9, wherein said source metal, said gate metal and said top drain metal each comprising Ti/Ni/Ag or Ti/Ni bounded with a solder ball for flip chip packaging.

14. The trench MOSFET of claim 1 further comprising a back drain metal comprising Ti/Ni/Ag or Ti/Ni/Au on a rear side of said substrate, wherein said back drain metal has a resistivity about 5˜

10 times lower than said substrate.