Manufacturing method of trench mosfet

Abstract

A manufacturing method of a trench MOSFET includes forming a trench gate in an epitaxial layer having a first conductivity type on a substrate, performing implantations of a dopant having a second conductivity type on the epitaxial layer in which an implantation dose is gradually reduced toward the substrate, performing a first drive-in step to diffuse the dopant having the second conductivity type in an upper half of the epitaxial layer to form a body region, implanting a dopant having the first conductivity type on a surface of the epitaxial layer, performing a second drive-in step to diffuse the dopant having the first conductivity type to form a source region, comprehensively implanting the dopant having the second conductivity type at an interface of the body region and the source region to form an anti-punch through region having a doping concentration higher than that of the body region.

What is claimed is: 
     
         1 . A manufacturing method of a trench MOSFET, comprising:
 forming a trench gate in an epitaxial layer having a first conductivity type on a substrate;   performing a plurality of implantations of a dopant having a second conductivity type on the epitaxial layer in a manner that an implantation dose is gradually reduced toward a direction of the substrate;   performing a first drive-in step to diffuse the dopant having the second conductivity type in an upper half of the epitaxial layer to form a body region having the second conductivity type;   implanting a dopant having the first conductivity type on a surface of the epitaxial layer;   performing a second drive-in step to diffuse the dopant having the first conductivity type to form a source region; and   comprehensively implanting the dopant having the second conductivity type at an interface of the body region and the source region after the source region is formed to form an anti-punch through region, wherein a doping concentration of the anti-punch through region is higher than a doping concentration of the body region.   
     
     
         2 . The manufacturing method of the trench MOSFET of  claim 1 , wherein a step of performing the plurality of implantations of the dopant having the second conductivity type comprises performing two or three implantations of the dopant having the second conductivity type. 
     
     
         3 . The manufacturing method of the trench MOSFET of  claim 1 , wherein the doping concentration of the anti-punch through region is between 5E+16 atoms/cm 3  and 5E+17 atoms/cm 3 . 
     
     
         4 . The manufacturing method of the trench MOSFET of  claim 1 , wherein the first conductivity type is N-type and the second conductivity type is P-type. 
     
     
         5 . The manufacturing method of the trench MOSFET of  claim 1 , wherein the first conductivity type is P-type and the second conductivity type is N-type. 
     
     
         6 . The manufacturing method of the trench MOSFET of  claim 1 , wherein an energy of implanting the dopant having the first conductivity type is between 20 KeV and 45 KeV. 
     
     
         7 . The manufacturing method of the trench MOSFET of  claim 1 , wherein the second drive-in step comprises rapid thermal processing (RTP). 
     
     
         8 . The manufacturing method of the trench MOSFET of  claim 1 , wherein the step of forming the trench gate comprises:
 forming a trench in the epitaxial layer;   forming a gate oxide layer on a surface of the trench; and   depositing a conductor in the trench as a gate.