Metal schemes of trench MOSFET for copper bonding

1. A vertical semiconductor power MOS device with a buffer metal layer for copper bonding comprising a plurality of semiconductor power cells with each cell comprising a plurality of trench gates surrounded by a plurality of source regions above a plurality of body regions above a drain region disposed on a bottom surface of a substrate, wherein said trench MOSFET further comprising:

a substrate of a first type conductivity;

an epitaxial layer of said first type conductivity over said substrate, having a lower doping concentration than said substrate;

a plurality of trenches extending into said epitaxial layer, surrounded by a plurality of source regions of said type conductivity above said body regions of the second type conductivity;

a first insulating layer lining said trenches as gate dielectric;

a doped polysilicon of the first type conductivity as gate regions overlying said first insulating layer;

a second insulating layer disposed over said epitaxial layer as an oxide interlayer;

a plurality of source-body contact trenches penetrating through said second insulating layer and said source regions, and into said body regions;

a first front metal layer of Ti/TiN/W or Co/Ti/W comprising a Tungsten (W) layer deposited over a Ti/TiN or Co/TiN barrier layer, covering said second insulating layer and filling into said source-body trenches as trench metal plug connected to said source and body regions, and also as said buffer metal layer for minimizing copper wire bonding damage to semiconductor device;

a second front metal disposed on front surface of device as source metal for Cu wire bonding;

a backside metal disposed on backside of said substrate as drain metal.

2. The trench MOSFET of claim 1 , wherein the angle between said source-body contact trench sidewalls and said top surface is 90+/−5 degree within said source and said body regions.

3. The trench MOSFET of claim 1 , wherein the angle between said source-body contact trench sidewalls and top surface is less than 85 degree within said source and body regions.

4. The trench MOSFET of claim 1 , wherein the angle between said source-body contact trench sidewalls and said top surface is 90+/−5 degree within said source regions and is less than 85 degree within said body regions.

5. The trench MOSFET of claim 1 further comprises a resistance reduction layer composed of a low resistance metal layer such as a Ti or Ti/TiN layer underneath said second front metal is deposited on top of said first front metal.

6. The trench MOSFET of claim 1 , wherein said second metal is Al alloys or Cu.

7. A method for manufacturing a trench MOSFET with improved metal schemes comprising the steps of:

growing an epitaxial layer upon a heavily N doped substrate, wherein said epitaxial layer is doped with a first type dopant, e.g., N dopant;

forming a trench mask with open and closed areas on the surface of said epitaxial layer;

removing semiconductor material from exposed areas of said trench mask to form a plurality of gate trenches;

growing a sacrificial oxide layer onto the surface of said trenches to remove the plasma damage introduced during opening said trenches;

removing said sacrificial oxide and said trench mask;

forming a first insulating layer on the surface of said epitaxial layer and along the inner surface of said gate trenches as gate oxide;

depositing doped poly or combination of doped poly onto said gate oxide and into said gate trenches;

forming a body mask and implanting said epitaxial layer with a second type dopant to from P-body regions;

removing said body mask and forming a source mask;

implanting whole device with a first type dopant to form source regions;

forming a second insulating layer onto whole surface;

forming a contact mask on the surface of said second insulating layer and removing the insulating material and semiconductor material;

implanting BF2 ion to form P+ area wrapping sidewalls and bottom of source-body contact trench within P-body region;

depositing Ti/TiN/W or Co/TiN/W consequently into source-body contact trenches and on the front surface;

depositing a layer of Al alloys on the front and rear side of device, respectively.

8. The method of claim 7 , wherein forming said gate trenches comprises etching said epitaxial layer according to the open areas of said trench mask by dry silicon etching.

9. The method of claim 7 , wherein filling said doped poly comprises making doped poly mesa over the first insulating layer to form terrace gate.

10. The method of claim 7 , wherein forming said P-body regions comprises a step of diffusion to achieve a certain depth after P-body implantation step.

11. The method of claim 7 , wherein forming said source regions comprises a step of diffusion to achieve a certain depth after n+ Ion Implantation step.

12. The method of claim 7 , wherein forming said source-body contact trench comprises etching through said N+ source regions and into said P-body regions by dry silicon etching according to the exposed areas of said contact mask.

13. The method of claim 7 , wherein implanting BF2 ion to form P+ area comprises implanting BF2 ion above source-body contact trench as well as above the second insulating layer.