Structure of trench MOSFET and method for manufacturing the same

• US 7,872,306 B2
• Filed: 08/30/2007
• Issued: 01/18/2011
• Est. Priority Date: 01/16/2007
• Status: Expired due to Fees

• Current Assignee: Fu-Yuan Hsieh
• Original Assignee: Fu-Yuan Hsieh
• Inventors: Hsieh, Fu-Yuan
• Primary Examiner(s): MATTHEWS, COLLEEN ANN
• Application Number:
  US11/847,445
• Publication Number:
  US 20080169505A1
• Time in Patent Office: 1,237 Days
• Field of Search: 257/330, 257/E29.136, 257/E21.409, 257/E21.418, 257/E21.419
• US Class Current: 257/331
• CPC Class Codes: H01L 21/743 Making of internal connections, substrate contacts
• CPC Class Codes: H01L 29/41741 for vertical or pseudo-vertical devices
• CPC Class Codes: H01L 29/42376 characterised by the length or the sectional shape
• CPC Class Codes: H01L 29/456 on silicon
• CPC Class Codes: H01L 29/4941 with a barrier layer between the silicon and the metal or metal silicide upper layer, e.g. Silicide/TiN/Polysilicon
• 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 29/7811 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

Abstract

A trench MOSFET with copper metal connections includes a substrate provided with a plurality of trenches. A gate oxide layer is formed on the sidewalls and bottoms of the trenches. A conductive layer is filled in the trenches to be used as a gate of the MOSFET. A plurality of source and body regions are formed in an epi layer. An insulating layer is formed on the epi layer and formed with a plurality of metal contact holes therein for contacting respective source and body regions. A barrier metal layer is formed on the sidewalls and bottoms of the metal contact holes in direct contact with respective source and body regions. A metal contact layer is filled in the metal contact holes. A copper metal layer is formed on another barrier metal layer on the insulating layer connected to respective source regions through the metal contact layer to form metal connections of the MOSFET.

Claims

1. A trench Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) comprising:

a plurality of trenches formed on top of an epi layer, wherein the epi layer is formed on a heavily-doped substrate;

a gate oxide layer formed on sidewalls and bottoms of the plurality of trenches;

a conductive layer filled in the plurality of trenches to be used as a gate structure of the MOSFET;

a plurality of source and body regions formed in the epi layer;

an insulating layer deposited on the epi layer formed with a plurality of metal contact holes therein;

a separating part formed on the insulating layer, wherein the separating part includes a bottom surface abutting with the insulating layer, a top surface opposite to the bottom surface, and a peripheral surface extending between the top and bottom surfaces;

a metal contact layer filled in the plurality of metal contact holes, wherein at least one of the plurality of metal contact holes with the metal contact layer filled therein is formed in the conductive layer for contacting the gate structure, and at least another one of the plurality of metal contact holes with the metal contact layer filled therein is formed for contacting respective source and body regions;

a first barrier metal layer formed on sidewalls and bottoms of the plurality of metal contact holes in direct contact with respective source and body regions and the gate structure;

a second barrier metal layer formed on the insulating layer and on sidewalls of the separating part, with the second barrier metal layer formed on the peripheral surface of the separating part;

a copper metal layer formed on the second barrier layer and on the sidewalls of the separating part, with the metal contact layer forming source and gate metal layers of the MOSFET, wherein the source metal layer is connected to respective source and body regions through the metal contact layer filled in the at least another one of the plurality of metal contact holes, the gate metal layer is connected to the gate structure through the metal contact layer filled in the at least one of the plurality of metal contact holes, and the source metal layer is separated from the gate metal layer by the separating part, with the top surface of the separating part being free of the second barrier metal layer and the copper metal layer.

2. The trench MOSFET according to claim 1, wherein the epi layer is an N-type doping epi layer, and the heavily-doped substrate is a heavily-doped N-type substrate for the N-channel MOSFET.

3. The trench MOSFET according to claim 1, wherein the epi layer is a P-type doping epi layer, and the heavily-doped substrate is a heavily-doped P-type substrate for the P-channel MOSFET.

4. The trench MOSFET according to claim 1, wherein the insulating layer is made of silicon dioxide layer.

5. The trench MOSFET according to claim 1, wherein the first barrier metal layer is formed by depositing Ti or Ta metal first, and then depositing TiN or TaN material.

6. The trench MOSFET according to claim 1, wherein the second barrier metal layer is formed by depositing Ta metal, or formed by depositing Ta then TaN material.

7. The trench MOSFET according to claim 1, wherein the gate oxide layer in the plurality of trenches is of a single oxide of which an oxide thickness is uniform along the sidewalls and bottoms of the plurality of trenches.

8. The trench MOSFET according to claim 1, wherein the gate oxide layer at the bottoms of the plurality of trenches has a larger thickness than that at the sidewalls of the plurality of trenches so as to reduce the capacitance of the gate oxide layer.

9. The trench MOSFET according to claim 1, further comprising:

a plurality of heavily-doped regions disposed at the bottoms of the plurality of metal contact holes.

10. A method for manufacturing a trench MOSFET comprising:

providing an epi layer on a heavily-doped substrate;

forming a plurality of trenches in the epi layer;

covering a gate oxide layer on sidewalls and bottoms of the plurality of trenches;

forming a conductive layer in the plurality of trenches to be used as a gate structure of MOSFET;

forming a plurality of source and body regions in the epi layer;

forming an insulating layer on the epi layer;

a separating part formed on the insulating layer, wherein the separating part includes a bottom surface abutting with the insulating layer, a top surface opposite to the bottom surface, and a peripheral surface extending between the top and bottom surfaces;

forming a plurality of metal contact holes in the insulating layer and the plurality of source and body regions;

forming a metal contact layer filled in the metal contact holes, wherein at least one of the plurality of metal contact holes with the metal contact layer filled therein is formed in the conductive layer for contacting the gate structure, and at least another one of the plurality of metal contact holes with the metal contact layer filled therein is formed for contacting respective source and body regions;

forming a first barrier metal layer on sidewalls and bottoms of the plurality of metal contact holes in direct contact with respective source and body regions and the gate structure;

forming a second barrier metal layer on the insulating layer and on sidewalls of the separating part, with the second barrier metal layer formed on the peripheral surface of the separating part; and

forming a copper metal layer on the second barrier metal layer and on the sidewalls of the separating part, with the metal contact layer, forming source and gate metal layers of the MOSFET, wherein the source metal layer is connected to respective source and body regions through the metal contact layer filled in the at least another one of the plurality of metal contact holes, the gate metal layer is connected to the gate structure through the metal contact layer filled in the at least one of the plurality of metal contact holes, and the source metal layer is separated from the gate metal layer by the separating part, with the top surface of the separating part being free of the second barrier metal layer and the copper metal layer.

11. The method according to claim 10, wherein the epi layer is an N-type doping epi layer, and the heavily-doped substrate is a heavily-doped N-type substrate for the N-channel MOSFET.

12. The method according to claim 10, wherein the epi layer is a P-type doping epi layer, and the heavily-doped substrate is a heavily-doped P-type substrate for the P-channel MOSFET.

13. The method according to claim 10, wherein the insulating layer is made of silicon dioxide layer.

14. The method according to claim 10, wherein the first barrier metal layer is formed by depositing Ti or Ta metal first, and then depositing TiN or TaN material.

15. The method according to claim 10, wherein the second barrier metal layer is formed by depositing Ta metal, or formed by depositing Ta then TaN material.

16. The method according to claim 10, wherein the gate oxide layer in the plurality of trenches is a single oxide of which an oxide thickness is uniform along the sidewalls and bottoms of the plurality of trenches.

17. The method according to claim 10, wherein the gate oxide layer at the bottoms of the plurality of trenches has a larger thickness than that at the sidewalls of the plurality of trenches so as to reduce the capacitance of the gate oxide layer.

18. The method according to claim 10, further comprising:

forming a plurality of heavily-doped regions disposed at the bottoms of the plurality of metal contact holes.