High voltage MOSFET diode reverse recovery by minimizing P-body charges
This invention discloses a method for manufacturing a semiconductor power device in a semiconductor substrate comprises an active cell area and a termination area. The method comprises the steps of a) growing and patterning a field oxide layer in the termination area and also in the active cell area on a top surface of the semiconductor substrate b) depositing and patterning a polysilicon layer on the top surface of the semiconductor substrate at a gap distance away from the field oxide layer; c) performing a blank body dopant implant to form body dopant regions in the semiconductor substrate substantially aligned with the gap area followed by diffusing the body dopant regions into body regions in the semiconductor substrate; d) implanting high concentration body-dopant regions encompassed in and having a higher dopant concentration than the body regions e) applying a source mask to implant source regions having a conductivity opposite to the body region with the source regions encompassed in the body regions and surrounded by the high concentration body-dopant regions; and f) etching contact trenches into the source, body contact, and body regions.
1. A method for manufacturing a semiconductor power device in a semiconductor substrate comprises an active cell area and a termination area comprising:
growing and patterning a field oxide layer in said termination area and also in said active cell area on a top surface of said semiconductor substrate using a first mask;
forming a gate oxide layer on said top surface of said semiconductor substrate;
depositing and patterning with a second mask a polysilicon layer on said gate oxide at a gap distance away from said field oxide layer, wherein said polysilicon layer acts as planar gates in the active area;
performing a blank body dopant implant to form body dopant regions in said semiconductor substrate substantially aligned with said gap area followed by diffusing said body dopant regions into body regions in said semiconductor substrate;
forming body contact regions encompassed in and having a higher dopant concentration than said body regions, wherein said field oxide layer patterned in the termination area and the active cell area reduces P-body charges in the semiconductor power device in forming the body and body contact regions;
applying a source mask as the third mask to implant source regions having a conductivity opposite to said body regions with said source regions encompassed in said body regions and located above said high concentration body contact regions;
depositing an insulation layer on top of said semiconductor power device and applying a contact mask as the fourth mask to open contact openings and remove said field oxide, and etching into the semiconductor substrate to form contact trenches, wherein said contact trenches further reduce the amount of P-body charges in the device; and
depositing a metal layer filling in said contact trenches to contact said body regions and said source regions, and patterning said metal layer with a fifth mask.
2. The method of claim 1 wherein:
said step of depositing a metal layer filling in said contact trenches further comprises depositing a Schottky metal layer to form integrated Schottky diodes.
3. The method of claim 2 further comprising:
forming shallow body-type regions adjacent to said body regions immediately below said contact trenches to adjust the Schottky barrier height.
4. The method of claim 1 wherein:
said step of performing a blank body dopant implant to form body regions further comprises performing a blank body dopant implant by implanting a first dopant body-dopant concentration with a reduced-body dopant concentration, and compensating by forming said body contact regions with an increased concentration to reduce body-dopant charges while maintaining a gate threshold voltage.
5. The method of claim 1 wherein:
said step of manufacturing said semiconductor power device further comprises a step of manufacturing a MOSFET power device.
6. The method of claim 1 wherein:
said step of manufacturing said semiconductor power device further comprises a step of manufacturing an IGBT power device.
7. The method of claim 6 wherein:
said applying a contact mask as the fourth mask to open contact openings further comprises forming an opening between polysilicon gates to form a Schottky diode trench.
8. The method of claim 1 wherein:
said step of manufacturing said semiconductor power device further comprises a step of manufacturing a superjunction power device.
9. The method of claim 8 further comprising prior to said step of growing and patterning a field oxide layer:
forming charge balanced alternating p-type and n-type columns in said semiconductor substrate.
10. The method of claim 1 further comprising a step of:
forming a body-type dopant region adjacent to the body region and below said contact trench to reduce the curvature of the body region.
11. The method of claim 1 wherein:
said step of depositing and patterning with a second mask a polysilicon layer further comprises depositing and patterning with a second mask a polysilicon layer in the termination area, wherein the polysilicon layer formed in the termination area act as field plates.
12. The method of claim 1 further comprising a step of:
forming a metal layer on the bottom of the semiconductor device to form a bottom electrode.