Formation of contacts on semiconductor substrates

Abstract

Embodiments of the invention are concerned with a method of manufacturing a radiation detector having one or more conductive contacts on a semiconductor substrate, and comprise the steps of: applying a first conductive layer to a first surface of the semiconductor substrate; applying a second conductive layer to form a plurality of contiguous layers of conductive materials, said plurality of contiguous layers including said first conductive layer; and selectively removing parts of said plurality of contiguous layers so as to form said conductive contacts, the conductive contacts defining one or more radiation detector cells in the semiconductor substrate.

1. A method of manufacturing a radiation detector having one or more conductive contacts on a semiconductor substrate, the one or more conductive contacts having respective contact positions, the method including the steps of:
 forming a layer of photoresist material on a first surface of the semiconductor substrate; 
 removing said photoresist material from areas corresponding to said contact positions to expose said first surface of the semiconductor substrate surface; 
 applying a first conductive layer to a on remaining photoresist material and on said exposed first surface of the semiconductor substrate; 
 applying a second conductive layer to form a plurality of contiguous layers of conductive materials on remaining photoresist material and on said exposed first surface of the semiconductor substrate, said plurality of contiguous layers including said first conductive layer; 
 selectively removing parts of said plurality of contiguous layers overlying said remaining photoresist material by removing said remaining photoresist material so as to form from remaining conductive material said conductive contacts, the conductive contacts defining one or more radiation detector cells in the semiconductor substrate, wherein each conductive contact comprises a first surface adjacent the semiconductor substrate, and a second, exposed surface; and 
 forming a layer of passivation material on said exposed surfaces of the conductive contacts and the regions around between said conductive contacts; 
 forming a further layer of photoresist material over said passivation layer; 
 removing portions of the further photoresist layer to expose portions of the passivation material overlying said conductive contacts; and 
 removing, using a passivation etchant, portions of said passivation material overlying said conductive contacts to expose the conductive contacts, such that the passivation material remains in the regions between said conductive contacts; and 
 removing remaining further photoresist material. 
 
     
     
       2. A method according to  claim 1 , including applying a third conductive layer between said first and second conductive layers, said third layer being a conductive layer. 
     
     
       3. A method according to  claim 1 , including applying a further conductive layer to the second conductive layer, said further layer being a conductive layer. 
     
     
       4. A method according to  claim 1 , including:
 forming a layer of photoresistive material on said substrate surface;   selectively exposing said photoresistive material and removing said photoresistive material from areas corresponding to said contact positions to expose said semiconductor substrate surface;   forming at least said first and second layers of conductive material on remaining photoresistive material and on said exposed semiconductor substrate surface; and   removing conductive material overlying said remaining photoresistive material by removing said remaining photoresistive material.   
     
     
       5. A method according to  claim 1 , wherein the step of removing portions of said passivation material overlying said conductive contacts to expose the conductive contacts comprises:
 forming a further layer of photoresistive material over said passivation layer;   selectively exposing said further layer of photoresistive material and removing said further photoresistive material to expose portions of said passivation layer corresponding to said contact positions;   removing said exposed portions of passivation material; and   removing remaining further photoresistive material.   
     
     
       6. A method according to claim  5  1, wherein said portions of said passivation layer are removed from areas smaller than the size of said conductive contacts such that the passivation layer overlaps said conductive contacts. 
     
     
       7. A method according to  claim 1 , wherein each of said first and second conductive layers is applied by sputtering, evaporation, electrolytic deposition, or electroless deposition. 
     
     
       8. A method according to  claim 1 , including forming a layer of conductive material on a surface of said substrate opposite to said first surface. 
     
     
       9. A method of manufacturing a radiation imaging device comprising:
 manufacturing a radiation detector in accordance with  claim 1 ; and individually connecting individual detector cell contacts for respective detector cells to corresponding circuits on a readout chip. 
 
     
     
       10. A method of manufacturing a radiation detector having one or more conductive contacts on a semiconductor substrate, the method including the steps of:
 applying a first conductive layer to a first surface of the semiconductor substrate;   applying a second conductive layer to form a plurality of contiguous layers of conductive materials, said plurality of contiguous layers including said first conductive layer;   selectively removing parts of said plurality of contiguous layers so as to form said conductive contacts, the conductive contacts defining one or more radiation detector cells in the semiconductor substrate;   forming a layer of photoresistive material on said substrate surface;   selectively exposing said photoresistive material and removing said photoresistive material from areas corresponding to said contact positions to expose said semiconductor substrate surface;   forming at least said first and second layers of conductive material on remaining photoresistive material and on said exposed semiconductor substrate surface; and   removing conductive material overlying said remaining photoresistive material by removing said remaining photoresistive material.   
     
     
       11. A method according to  claim 10 , including applying a third layer between said first and second layers, said third layer being a conductive layer. 
     
     
       12. A method according to  claim 10 , including applying a further layer to the second layer, said further layer being a conductive layer. 
     
     
       13. A method according to  claim 10 , including forming a layer of passivation material on said conductive contacts and the regions around conductive contacts; and removing portions of said passivation material overlying said conductive contacts to expose the conductive contacts. 
     
     
       14. A method according to  claim 13 , wherein the step of removing portions of said passivation material overlying said conductive contacts to expose the conductive contacts comprises:
 forming a further layer of photoresistive material over said passivation layer;   selectively exposing said further layer of photoresistive material and removing said further photoresistive material to expose portions of said passivation layer corresponding to said contact positions;   removing said exposed portions of passivation material; and   removing remaining further photoresistive material.   
     
     
       15. A method according to  claim 14 , wherein said portions of said passivation layer are removed from areas smaller than the size of said conductive contacts such that the passivation layer overlaps said conductive contacts. 
     
     
       16. A method according to  claim 10 , wherein each of said first and second layers is applied by sputtering, evaporation, electrolytic deposition, or electroless deposition. 
     
     
       17. A method according to  claim 10 , including forming a layer of conductive material on a surface of said substrate opposite to said first surface. 
     
     
       18. A method of manufacturing a radiation imaging device comprising:
 manufacturing a radiation detector in accordance with  claim 10 ; and individually connecting individual detector cell contacts for respective detector cells to corresponding circuits on a readout chip.   
     
     
       19. A method according to claim 1, wherein the first conductive layer is a contact layer formed adjacent to the substrate, and the second conductive layer is a diffusion barrier layer. 
     
     
       20. A method according to claim 1, wherein the length of the first surface of the conductive contact in a direction parallel to the plane of the substrate is greater than the length of the second surface of the conductive contact in said direction, whereby each conductive contact is provided with a substantially trapezoidal cross-section. 
     
     
       21. A method according to claim 1, wherein the first conductive layer is formed adjacent to the substrate surface, the first conductive layer comprising platinum. 
     
     
       22. A method according to claim 2, wherein the third conductive layer comprises gold. 
     
     
       23. A method according to claim 1, wherein the second conductive layer comprises nickel. 
     
     
       24. A method according to claim 3, wherein the further conductive layer comprises gold. 
     
     
       25. A method according to claim 1, wherein the step of forming a layer of photoresist material on said substrate surface includes applying photoresist material to all exposed surfaces.