Method of manufacturing a superjunction device

• US 20050181577A1
• Filed: 12/17/2004
• Published: 08/18/2005
• Est. Priority Date: 12/19/2003
• Status: Active Grant

• Current Assignee: Third Dimension Semiconductor Incorporated
• Original Assignee: Third Dimension Semiconductor Incorporated
• Inventors: Hshieh, Fwu-Iuan
• Granted Patent: US 7,109,110 B2
• Time in Patent Office: Days
• US Class Current: 438/427
• CPC Class Codes: H01L 21/266 using masks H01L21/26586 takes precedence
• CPC Class Codes: H01L 29/0634 Multiple reduced surface field (multi-RESURF) structures, e.g. double RESURF, charge compensation, cool, superjunction (SJ), 3D-RESURF, composite buffer (CB) structures
• CPC Class Codes: H01L 29/0653 adjoining the input or output region of a field-effect device, e.g. the source or drain region
• CPC Class Codes: H01L 29/0696 of cellular field-effect devices, e.g. multicellular DMOS transistors or IGBTs
• CPC Class Codes: H01L 29/66712 Vertical DMOS transistors, i.e. 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

Abstract

A partially manufactured semiconductor device includes a semiconductor substrate. The device includes a first oxide layer formed on the substrate, with a mask placed over the oxide-covered substrate, a plurality of first trenches and at least one second trench etched through the oxide layer forming mesas. The at least one second trench is deeper and wider than each of the first trenches. The device includes a second oxide layer that is disposed over an area of mesas and the plurality of first trenches. The device includes a layer of masking material that is deposited over a an area of an edge termination region adjacent to an active region. The area of mesas and first trenches not covered by the masking layer is etched to remove the oxidant seal. The device includes an overhang area that is formed by a wet process etch.

Claims

1. A partially manufactured semiconductor device comprising:

a semiconductor substrate having first and second main surfaces opposite to each other, the semiconductor substrate having a heavily doped region of a first conductivity type at the second main surface and having a lightly doped region of the first conductivity type at the first main surface;

a first oxide layer formed over the first main surface with a mask placed over the oxide-covered substrate, a plurality of first trenches and at least one second trench being etched through the oxide layer into the semiconductor substrate through openings in the mask forming mesas, each first trench having a first extending portion extending from the first main surface toward the heavily doped region to a first depth position, the at least one second trench having a second extending portion extending from the first main surface toward the heavily doped region to a second depth position, each mesa having a sidewall surface, each of the plurality first trenches and the at least one second trench being separated from adjacent trenches by one of the mesas, the at least one second trench being deeper and wider than each of the plurality of first trenches;

a second oxide layer formed over an area of mesas and the plurality of first trenches, the second oxide layer covering the top of each mesa and sealing the top of each of the plurality of first trenches and the at least one second trench at an edge of the area containing the mesas and the plurality of first trenches;

a layer of masking material selected from a group including a photoresist, a nitride, a metal, and polysilicon, deposited over a preselected area of an edge termination region adjacent to an active region containing at least the area of mesas and the plurality of first trenches, and partially over the at least one second trench at an edge of the area of the active region containing the mesas and the plurality of first trenches, the edge termination region containing a portion of the at least one second trench, the active region being the area on which a semiconductor device will be formed and the termination region being an area which provides insulation between cells of semiconductor devices;

the area of mesas and the plurality of first trenches not covered by the masking layer having the oxidant seal removed over the plurality of trenches including the at least one second trench; and

an overhang area that includes the masking material and that is formed by a wet process etch which removes areas of the oxide layer not protected by the masking material, the overhang area extending partially over the at least one second trench.

2. A partially manufactured semiconductor device according to claim 1, further comprising:

implanted areas, including the sidewalls of each trench in the active region, which form P-N junctions along the first depth direction of each of the plurality of first trenches and part of the at least one second trench along the second depth direction.

3. A partially manufactured semiconductor device according to claim 2, further comprising:

an insulating material filling the plurality of first trenches disposed in the active region and the at least one second trench disposed at least partially in the edge termination region; and

a planarized top surface.

12. The method according to claim 3, wherein the lateral dimension of each of the dopants of the first and second conductivity type regions in the top surface of the semiconductor device is greater than the distance from the sidewall surfaces of the adjacent pair of trenches to the P-N junction of the first and second doped regions.

13. The partially manufactured semiconductor device according to claim 1, wherein the sidewall surface of each mesa has a predetermined inclination angle maintained relative to the first main surface

4. A semiconductor device comprising:

a semiconductor substrate having first and second main surfaces opposite to each other, the semiconductor substrate having a heavily doped region of a first conductivity type at the second main surface and having a lightly doped region of the first conductivity type at the first main surface;

a first oxide layer formed over the first main surface with a mask placed over the oxide-covered substrate, a plurality of first trenches and at least one second trench being etched through the oxide layer into the semiconductor substrate through openings in the mask forming mesas, each first trench having a first extending portion extending from the first main surface toward the heavily doped region to a first depth position, the at least one second trench having a second extending portion extending from the first main surface toward the heavily doped region to a second depth position, each mesa having a sidewall surface, each of the plurality first trenches and the at least one second trench being separated from adjacent trenches by one of the mesas, the at least one second trench being deeper and wider than each of the plurality of first trenches;

a second oxide layer formed over an area of mesas and the plurality of first trenches, the second oxide layer covering the top of each mesa and sealing the top of each of the plurality of first trenches and the at least one second trench at an edge of the area containing the mesas and the plurality of first trenches;

a layer of masking material selected from a group including a photoresist, a nitride, a metal, and polysilicon, deposited over a preselected area of an edge termination region adjacent to an active region containing at least the area of mesas and the plurality of first trenches and partially over the at least one second trench at an edge of the area of the active region containing the mesas and the plurality of first trenches, the edge termination region containing a portion of the at least one second trench;

the area of mesas and the plurality of first trenches not covered by the masking layer having the oxidant seal removed over the plurality of trenches including the at least one second trench;

an overhang area that includes the masking material and that is formed by a wet process etch which removes areas of the oxide layer not protected by the masking material, the overhang area extending partially over the at least one second trench;

implanted areas, included the sidewalls of each trench in the active region, which form P-N junctions along the first depth direction of each of the plurality of first trenches and part of the at least one second trench along the second depth direction;

an insulating material filling the plurality of first trenches disposed in the active region and the at least one second trench disposed in the edge termination region;

a planarized top surface; and

a superjunction device formed on the device, the active region being the area on which the superjunction device is formed and the termination region being an area which provides insulation between cells of superjunction devices.

14. The semiconductor device according to claim 4, wherein the sidewall surface of each mesa has a predetermined inclination angle maintained relative to the first main surface.

5. A method of manufacturing a semiconductor device comprising:

providing a semiconductor substrate having first and second main surfaces opposite to each other, the semiconductor substrate having a heavily doped region of a first conductivity type at the second main surface and having a lightly doped region of the first conductivity type at the first main surface;

oxidizing the exposed surface of the lightly doped region of the first conductivity type;

providing a plurality of first trenches and at least one second trench and mesas in the semiconductor substrate, each first trench having a first extending portion extending from the first main surface toward the heavily doped region to a first depth position, the at least one second trench having a second extending portion extending from the first main surface toward the heavily doped region to a second depth position, each mesa having a sidewall surface, each of the plurality first trenches and the at least one second trench being separated from adjacent trenches by one of the mesas, the at least one second trench being deeper and wider than each of the plurality of first trenches, the at least one second trench being positioned at a border between an active region and a termination region, the active region being the area on which semiconductor devices will be formed and the termination region being an area which provides insulation between cells of active devices;

performing a chemical vapor deposition (CVD) process step to seal the tops of each of the plurality of first trenches and the at least one second trench, creating voids within each of the plurality of first trenches and the at least one second trench, and covering the top of each mesa;

depositing a layer of material selected from a group including a photoresist, a nitride, a metal and polysilicon over the edge termination region and partially over the at least one second trench at the border between the active and edge termination regions;

performing a dry oxide etch step to remove the seal over the plurality of first trenches and the at least one second trench;

performing a wet oxide etch step to remove the oxide from the CVD step remaining in the plurality of first trenches, the at least one second trench and on the tops of the mesas, while oxide from the initial oxidization remains on the tops of the mesas, the wet oxide etch step forming an overhang of the photoresist/nitride/metal/polysilicon material over the at least one second trench at the border between the active and termination regions;

implanting a dopant of the first conductivity type into at least one mesa of the semiconductor substrate between an adjacent pair of the plurality of first trenches at a sidewall surface of one trench to form at the sidewall surface of the one trench a first doped region of the first conductivity type having a doping concentration lower than that of the heavily doped region, the overhang preventing the implantation of the bottom of the at least one second trench at the border between active and termination regions;

implanting a dopant of the second conductivity type into at least one mesa at a sidewall surface opposite to the sidewall implanted with the dopant of the first conductivity type to provide a second doped region of the second conductivity type at the sidewall surface opposite to the sidewall implanted with the dopant of the first conductivity type;

refilling the plurality of first trenches with an insulating material; and

planarizing the top surface of the device.

6. The method according to claim 5, further comprising:

forming a superjunction device on the resulting structure.

7. The method according to claim 5, further comprising:

providing a third doped region of the second conductivity type at the first main surface of the first and second doped regions to be electrically connected to the second doped region;

providing a fourth doped region of the first conductivity type at either the first main surface or a sidewall surface of the one trench such that the fourth doped region is opposite to the first doped region with the third doped region posed there between; and

providing a gate electrode layer above the third doped region between the first and fourth doped regions, with a gate insulation layer interposed therebetween.

8. The method according to claim 7, wherein the gate electrode layer is formed in at least one of the trenches.

9. The method according to claim 7, wherein the gate electrode layer is formed on the first main surface.

10. The method according to claim 5, further comprising:

providing a third doped region of the second conductivity type at the first main surface of the first and second doped regions to be electrically connected to the second doped region.

11. The method according to claim 5, further comprising:

providing an electrode layer in Schottky contact with the first doped region.

15. The method according to claim 5, wherein the sidewall surface of each mesa has a predetermined inclination angle maintained relative to the first main surface.

16. The method according to claim 5, wherein the seal prevents deposition of any material in the plurality of first trenches and the at least one second trench.

17. The method according to claim 5, wherein the implanting the dopant of the first conductivity type is performed at a first predetermined angle of implant.

18. The method according to claim 5, wherein the implanting the dopant of the second conductivity type is performed at a second predetermined angle of implant.

19. A semiconductor formed by the method of claim 5.