High voltage vertical conduction superjunction semiconductor device

Abstract

A high voltage vertical conduction semiconductor device has a plurality of deep trenches or holes in a lightly doped body of one conductivity type. A diffusion of the other conductivity type is formed in the trench walls to a depth and a concentration which matches that of the body so that, under reverse blocking, both regions fully deplete. The elongated trench or hole is filled with a dielectric which may be a composite of nitride and oxide layers having a lateral dimension change matched to that of the silicon. The filler may also be a highly resistive SIPOS which permits leakage current flow from source to drain to ensure a uniform electric field distribution along the length of the trench during blocking.

1. A high voltage vertical conduction superjunction semiconductor device comprising:
 a body of one conductivity type;  
 a plurality of spaced vertical trenches formed into the upper surface of said body;  
 diffusions including a diffusion of thean other conductivity type formed into the interior surface of each of said plurality of said trenches;  
 a MOSgated structure connected to the top of said body and to the top of each of said diffusions;  
 the thickness and concentration of said diffusion  diffusions and the width and concentration of said body being matched to insure  ensure substantially full depletion of said diffusion  diffusions and body when blocking voltage is applied to said body;  
 wherein said MOSgated structure comprises a base of the other conductivity type extending across the top of said body, a plurality of spaced source regions of the one conductivity type diffused into said base, a plurality of second trenches in the top of said base and between respective pairs of said trenches, a gate oxide lining the interior of said second trenches and a conductive polysilicon gate filling the interior of said second trenches; and a source contact formed on the top surface of said device and in contact with said base and with said source regions.  
 
     
     
       2. The device of  claim 1  wherein the interiors of each  of each of said trenches is filled with a dielectric material. 
     
     
       3. The device of  claim 2 , wherein said dielectric is silicon dioxide. 
     
     
       4. The device of  claim 1 , wherein each of said trenches are laterally elongated parallel trenches. 
     
     
       5. The device of  claim 4 , wherein the interiors of each of said trenches is filled with a dielectric material. 
     
     
       6. The device of  claim 1 , wherein each of said trenches has a closed cellular topology. 
     
     
       7. The device of  claim 2 , wherein each of said trenches has a closed cellular topology. 
     
     
       8. A high voltage vertical conduction superjunction semiconductor device comprising:
 a body of one conductivity type;  
 a plurality of spaced vertical trenches formed into the upper surface of said body;  
 diffusions including a diffusion of thean other conductivity type formedextending into said body from the interior surface of each of said plurality of trenches; and  
 a MOSgated structure that includes a base region of the other conductivity connected to the top of said body and to the top of each said diffusions;  
 the thickness and concentration of said diffusion  diffusions and the width and concentration of said body being matched to insure  ensure substantially full depletion of said diffusion  diffusions and body when blocking voltage is applied to said body; and  
 wherein said vertical trenches extend through said base region and the interiors of each of said trenches is filled with a highly resistive material which is connected to a source electrode at its top and said  a drain structure at its bottom and carries an intentional leakage current under blocking conditions to force a uniform electric field distribution along the length of each of said trenches during a blocking condition.  
 
     
     
       9. The device of  claim 1 , wherein said dielectric is a highly resistive material which is connected to a source electrode at its top and said drain structure at its bottom and carries an intentional leakage current under blocking conditions to force a uniform electric field distribution along the length of said trench during a blocking condition. 
     
     
       10. The device of  claim 8 , wherein each of said trenches are laterally elongated parallel trenches. 
     
     
       11. The device of  claim 8 , wherein each of said trenches has a closed cellular topology. 
     
     
       12. A high voltage vertical conduction superjunction semiconductor device comprising:
 a body of one conductivity type;  
 a plurality of spaced vertical trenches formed into the upper surface of said body;  
 diffusions including a diffusion of the other conductivity type formedextending into said body from the interior surface of each of said plurality of said trenches; and  
 a MOSgated structure that includes a base region of the other conductivity type connected to the top of said body and to the top of each of said diffusions;  
 the thickness and concentration of said diffusion  diffusions and the width and concentration of said body being matched to insure  ensure substantially full depletion of said diffusion  diffusions and body when blocking voltage is applied to said body; and  
 wherein said trenches extend through said base region and the interiors of each of said trenches is filled with a semi-insulating polysilicon.  
 
     
     
       13. The device of  claim 2 , wherein said dielectric is a semi-insulating polysilicon. 
     
     
       14. The device of  claim 10 , wherein said dielectric  highly resistive material is a semi-insulating polysilicon. 
     
     
       15. The device of  claim 11 , wherein said dielectric  highly resistive material is a semi-insulating polysilicon. 
     
     
       16. The device of  claim 2 , wherein said dielectric material consists of alternate vertical layers of at least a first and second dielectric of diverse thermal expansion characteristics which, together, match the expansion characteristics of silicon. 
     
     
       17. The device of  claim 16 , wherein said first and second dielectrics are silicon dioxide and silicon nitride respectively. 
     
     
       18. The device of  claim 16 , wherein said MOSgated structure comprises a base of the other conductivity type extending across the top of said body, a plurality of spaced source regions of the one conductivity type diffused into said base, a plurality of second trenches in the top of said base and between respective pairs of said trenches, a gate oxide lining the interior of said second trenches and a conductive polysilicon gate filling the interior of said second trenches; and a source contact formed on the top surface of said device and in contact with said base and with said source regions. 
     
     
       19. The device of  claim 16 , wherein each of said trenches are laterally elongated parallel trenches. 
     
     
       20. The device of  claim 17 , wherein each of said trenches are laterally elongated parallel trenches. 
     
     
       21. The device of  claim 20 , wherein said first and second dielectrics are silicon dioxide and silicon nitride respectively. 
     
     
       22. The device of  claim 20 , wherein said device contains a plurality of parallel trenches; each of said trenches being filled by said dielectric filler. 
     
     
       23. A high voltage vertical conduction superjunction semiconductor device comprising:
   a body of one conductivity type;        a plurality of spaced vertical trenches formed into the upper surface of said body;        diffusions including a diffusion of an other conductivity type extending into said body from the interior surface of each of said plurality of said trenches;        a MOSgated structure connected to the top of said body;        the thickness and concentration of said diffusions and the width and concentration of said body being matched to ensure substantially full depletion of said diffusions and body when blocking voltage is applied to said body;        wherein said MOSgated structure comprises a base of the other conductivity type extending across the top of said body, a plurality of spaced source regions of the one conductivity type diffused into said base, a plurality of second trenches in the top of said base and between respective pairs of said trenches, a gate oxide lining the interior of said second trenches and a conductive polysilicon gate filling the interior of said second trenches; and a source contact formed on the top surface of said device and in contact with said base and with said source regions.     
     
     
       24. A high voltage vertical conduction semiconductor device comprising:
   a substrate of one conductivity type;        a body of said one conductivity type over said substrate;        a base region of an other conductivity type;        a plurality of spaced vertical trenches formed into the upper surface of said body and extending through said base region, each trench including opposing sidewalls and a bottom, said bottom residing in said body, whereby each trench terminates in said body, each trench being filled with an insulator;        diffusions including a diffusion of the other conductivity type electrically coupled to said base region and extending into said body from said sidewalls and said bottom of each trench and forming a PN junction with said body, the thickness and concentration of each said diffusions and the width and concentration of said body being selected to ensure substantially full depletion of said diffusions and        a source electrode electrically connected to said diffusions; and        a drain electrode electrically connected to said substrate.     
     
     
       25. The semiconductor device of  claim 24 , wherein said insulator is comprised of an oxide. 
     
     
       26. The semiconductor device of  claim 24 , wherein said insulator includes a nitride. 
     
     
       27. The semiconductor device of  claim 24 , wherein said insulator includes an oxide liner and a nitride filler. 
     
     
       28. The semiconductor device of  claim 24 , wherein said insulator is selected to reduce thermal stress on said body. 
     
     
       29. A high voltage vertical conduction superjunction semiconductor device comprising:
   a substrate of one conductivity type;        a body of said one conductivity type over said substrate;        a base region of an other conductivity type;        a plurality of spaced vertical trenches formed into the upper surface of said body and extending through said base region;        diffusions including a diffusion of the other conductivity type electrically coupled to said base region and extending into said body from the interior surface of each said plurality of said trenches, the thickness and concentration of said diffusions and the width and concentration of said body being selected to ensure substantially full depletion of said diffusions and body when blocking voltage is applied to said body;        a MOSgated structure connected to the top of said body;        a source electrode electrically connected to said diffusions;        a drain electrode electrically connected to said substrate; and        a highly resistive current path between said drain electrode and said source electrode.