Manufacturing method of trench-type power device

1 . A manufacturing method of a trench-type power device, wherein the manufacturing method comprises:

forming a drift region on a semiconductor substrate;

forming a first trench and a second trench in the drift region;

forming a gate stack in the first trench;

forming a doped region and a well region of P type in the drift region by performing first ion implantation; and

forming a source region of N type in the well region by performing second ion implantation,

wherein the well region in which a dopant concentration gradually decreases with depth is formed by the first ion implantation, and an upper part of the well region is inverted by the second ion implantation to form the source region,

wherein in the first ion implantation, by using the gate stack as a hard mask, the well region is formed between the first trench and the second trench, and the doped region is formed below a bottom of the second trench, and the doped region extends to a first depth in the drift region, the well region extends to a second depth in the drift region, and the first depth is greater than the second depth.

2 . The manufacturing method according to claim 1 , wherein in the second ion implantation, by using the gate stack as a hard mask and shielding the second trench with a resist mask, a dopant is implanted in the upper part of the well region.

3 . The manufacturing method according to claim 1 , wherein a dopant type of the semiconductor substrate and the drift region is N-type, and the semiconductor substrate serves as a drain region of a power transistor.

4 . The manufacturing method according to claim 1 , further comprising:

forming Schottky metal on a sidewall of the second trench,

wherein the Schottky metal and the drift region form a Schottky barrier diode.

5 . The manufacturing method according to claim 4 , wherein the step of forming the Schottky metal comprises:

forming a conformal first metal layer in the second trench; and

removing a portion, which is located at an upper part of the sidewall of the second trench, of the first metal layer, and a portion, which is located at a bottom of the second trench, of the first metal layer, by performing anisotropic etching,

wherein a portion, which remains at a lower part of the sidewall of the second trench, of the first metal layer forms the Schottky metal.

6 . The manufacturing method according to claim 5 , wherein in the step of forming the Schottky metal, a top end of the Schottky metal is located between the source region and the drift region by controlling etching time of the anisotropic etching.

7 . The manufacturing method according to claim 6 , wherein after the step of forming the Schottky metal, the manufacturing method further comprises:

forming a conformal second metal layer in the second trench;

generating silicide by reaction of a portion of the second metal layer, by performing a silicidation process; and

removing unreacted metal of the second metal layer relative to the Schottky metal and the silicide, by performing a selective etching process,

wherein a portion, which is located at the upper part of the sidewall of the second trench, of the silicide, forms a first contact layer, and a portion, which is located at the bottom of the sidewall of the second trench, of the silicide forms a second contact layer.

8 . The manufacturing method according to claim 6 , wherein after the step of forming the Schottky metal, the manufacturing method further comprises:

filling a conductive material in the second trench to form a conductive channel for providing an electrical connection path between the source region and the Schottky metal.

9 . The manufacturing method according to claim 1 , wherein the doped region is separate from the well region in position, and is formed simultaneously with the well region by the first implantation after the second trench is formed.