Low-voltage punch-through transient suppressor employing a dual-base structure

Abstract

A punch-through diode transient suppression device has a base region of varying doping concentration to improve leakage and clamping characteristics. The punch-through diode includes a first region comprising an n+ region, a second region comprising a p− region abutting the first region, a third region comprising a p+ region abutting the second region, and a fourth region comprising an n+ region abutting the third region. The peak dopant concentration of the n+ layers should be about 1.5E18 cm −3 , the peak dopant concentration of the p+ layer should be between about 1 to about 5 times the peak concentration of the n+ layer, and the dopant concentration of the p− layer should be between about 0.5E14 cm −3 and about 1.OE17 cm −3 . The junction depth of the fourth (n+) region should be greater than about 0.3 μm. The thickness of the third (p+) region should be between about 0.3 μm and about 2.0 μm, and the thickness of the second (p−) region should be between about 0.5 μm and about 5.0 μm.

What is claimed is:  
     
       1. A punch-through diode transient suppression device comprising: 
       a first region comprising an n+ region;  
       a second region comprising a p− region abutting said first region;  
       a third region comprising a p+ region abutting said second region;  
       a fourth region comprising an n+ region abutting said third region;  
       a passivation layer disposed over an upper surface of said fourth region; and  
       an isolation trench disposed at outer edges of said p− region, said p+ region, and said fourth n+ region, said isolation trench extending into said first n+ region.  
     
     
       2. The punch-through diode transient suppression device of  claim 1  wherein: 
       said first and fourth regions have a peak dopant concentration of about 1.5E18 cm −3 ;  
       said third region has a peak dopant concentration of between about 50 to about 2,000 times said peak dopant concentration of said second region; and  
       said second region has a dopant concentration of between about 0.5E14 cm −3  and about 1.0E17 cm −3 .  
     
     
       3. The punch-through diode transient suppression device of  claim 2  wherein: 
       said fourth region has a junction depth of greater than about 0.3 um;  
       said third region has a thickness of between about 0.3 um and about 2.0 um, and  
       said second region has a thickness of between about 0.5 um and about 5.0 um.  
     
     
       4. A punch-through diode transient suppression device comprising: 
       a n+ substrate having an upper surface;  
       a p− region disposed on said upper surface of said n+ substrate, said p− region having an upper surface, a side surface, and a first end; and  
       a p+ region disposed on said upper surface of said p− region, said p+ region having an upper surface and a first end;  
       an n+ region disposed on an upper surface of said p+ region, said n+ region having an upper surface;  
       an isolation diffusion region disposed on said side of said p− region, said isolation diffusion region having an upper surface; and  
       a passivation layer disposed over said upper surface of said n+ region, at said upper surface of said isolation diffusion region, at said first end of said p− region, and at said first end of said p+ region.  
     
     
       5. The punch-through diode transient suppression device of  claim 4  wherein: 
       said substrate and said n+ region have a peak dopant concentration of about 1.5E18 cm −3 ;  
       said p+ region has a peak dopant concentration of between about 50 to about 2,000 times said dopant concentration of said p− region; and  
       said p− region has a dopant concentration of between about 0.5E14 cm −3  and about 1.0E17 cm −3 .  
     
     
       6. The punch-through diode transient suppression device of  claim 5  wherein: 
       said n+ region has a junction depth of greater than about 0.3 um;  
       said p+ region has a thickness of between about 0.3 um and about 2.0 um, and  
       said p− region has a thickness of between about 0.5 um and about 5.0 um.  
     
     
       7. The punch-through diode in  claim 1 , wherein said passivation layer is disposed over said upper surface at outer edges of said p− region and said p+ region; said passivation layer including a contact aperture therethrough to an upper surface of said n+ region. 
     
     
       8. The punch-through diode transient suppression device of  claim 1  wherein: 
       said first and fourth regions have a peak dopant concentration of about 1.5E18 cm −3 ;  
       said third region has a peak dopant concentration of between about 50 to about 2,000 times said peak dopant concentration of said second region; and  
       said second region has a dopant concentration of between about 0.5E14 cm −3  and about 1.0E17 cm −3 .  
     
     
       9. The punch-through diode transient suppression device of  claim 8  wherein: 
       said fourth region has a junction depth of greater than about 0.3 μm;  
       said third region has a thickness of between about 0.3 μm and about 2.0 μm, and  
       said second region has a thickness of between about 0.5 μm and about 5.0 μm.  
     
     
       10. The punch-through diode in  claim 7 , further including an isolation region disposed at outer edges of said p−region, said p+ region, and said n+ region, said isolation region extending into said n+ region. 
     
     
       11. The punch-through diode in  claim 4 , wherein said passivation layer includes a contact aperture therethrough to said upper surface of said n+ region. 
     
     
       12. A punch- through diode transient suppression device comprising:    
       
         a first region comprising a first dopant type and a first dopant concentration value;  
       
       
         a second region comprising a second dopant concentration value that differs from said first dopant concentrative value, said second region abutting said first region;  
       
       
         a third region comprising a third dopant type that differs from said first dopant type, said third region abutting said second region;  
       
       
         a fourth region comprising said first dopant type, said fourth region abutting said third region;  
       
       
         a passivation layer disposed over an upper surface of said fourth region, said passivation layer having an aperture allowing a metal contact to provide an electrical connection with said fourth region;  
       
       
         an isolation trench disposed at outer edges of said second region, said third region, and said fourth region, said isolation trench extending into said first region.  
       
     
     
       13. The punch- through diode transient suppression device of    claim 12   , wherein said first and fourth regions each comprises an n dopant type.    
     
     
       14. The punch- through diode transient suppression device of    claim 13   , wherein said first and fourth regions each comprises an n+ dopant type.    
     
     
       15. The punch- through diode transient suppression device of    claim 12   , wherein said third region comprises a p dopant type.    
     
     
       16. The punch- through diode transient suppression device of    claim 15   , wherein said third region comprises a p+ dopant type.    
     
     
       17. The punch- through diode transient suppression device of    claim 12   , further comprising a first metal contact disposed in said aperture, said first metal contact making an electrical connection with said fourth region.    
     
     
       18. The punch- through diode transient suppression device of    claim 17   , further comprising a second metal contact making an electrical connection with said first region.    
     
     
       19. The punch- through diode transient suppression device of    claim 12   , wherein:    
       
         said fourth region has a junction depth of greater than about  0 . 3  μm;  
       
       
         said third region has a thickness of between about  0 . 3  μm and  2 . 0  μm; and  
       
       
         said second region has a thickness of between about  0 . 5  μm and about  5 . 0  μm.  
       
     
     
       20. The punch- through diode transient suppression device of    claim 12   , wherein said second region reduces a capacitance of the suppression device.    
     
     
       21. The punch- through diode transient suppression device of    claim 12   , wherein said passivation layer is further disposed on a first end of said second region and a first end of said third region.    
     
     
       22. A punch- through diode transient suppression device comprising:    
       
         an n+ dopant type substrate having an n+ dopant concentration value;  
       
       
         a first region for reducing a capacitive level of the suppression device, said first region abutting said n+ dopant type substrate and comprising a first dopant concentration value that differs from said n+ dopant concentration value;  
       
       
         a second region abutting said first region, said second region comprising a second dopant type that differs from said n+ dopant type;  
       
       
         an n+ dopant type region abutting said second region;  
       
       
         a passivation layer disposed over an upper surface of said n+ dopant type region, said passivation layer having an aperture allowing a metal contact to provide an electrical connection with said n+ dopant type region; and  
       
       
         an isolation region disposed at outer edges of said first region, said second region, and said fourth region, said isolation region extending into said n+ dopant type substrate.  
       
     
     
       23. The punch- through diode transient suppression device of    claim 22   , wherein said second region comprises a p dopant type.    
     
     
       24. The punch- through diode transient suppression device of    claim 23   , wherein said second region comprises a p+ dopant type.    
     
     
       25. The punch- through diode transient suppression device of    claim 22   , further comprising a first metal contact disposed in said aperture, said first metal contact making an electrical connection with said n+ dopant type region.    
     
     
       26. The punch- through diode transient suppression device of    claim 25   , further comprising a second metal contact making an electrical connection with said first n+ dopant type substrate.    
     
     
       27. The punch- through diode transient suppression device of    claim 22   , wherein:    
       
         said n+ dopant type region has a junction depth of greater than about  0 . 3  μm;  
       
       
         said second region has a thickness of between about  0 . 3  μm and about  2 . 0  μm; and  
       
       
         said first region has a thickness of between about  0 . 5  μm and about  5 . 0  μm.  
       
     
     
       28. The punch- through diode transient suppression device of    claim 22   , wherein said passivation layer is further disposed on a first end of said first region and a first end of said second region.