Semiconductor radiation detector

Abstract

A semiconductor radiation detector device includes a semiconductor substrate. On one surface of the substrate are a MIG layer ( 241 ) of semiconductor of second conductivity type, a barrier layer ( 251 ) of semiconductor of first conductivity type, and pixel dopings of semiconductor of the second conductivity type. The pixel dopings are adapted to be coupled to at least one pixel voltage in order to create a source and a drain of a pixel-specific transistor. The device further includes a first conductivity type first contact, so that the pixel voltage is a potential difference between one of the pixel dopings and the first conductivity type first contact. The location of a main gate ( 983 ) corresponds at least partly to the location of a channel between the source and the drain. The device includes at least one extra gate ( 981, 982 ) horizontally displaced from the main gate ( 983 ).

The invention claimed is: 
     
       1. A semiconductor radiation detector device comprising at least one pixel, wherein the at least one pixel comprises a semiconductor substrate ( 100 ) and on one surface of the substrate in the following order:
 a first layer ( 241 ) of semiconductor of second conductivity type, hereinafter the MIG layer,   a barrier layer ( 251 ) of semiconductor of first conductivity type, configured to form a potential energy barrier for signal charges accumulated in said MIG layer during operation of the device,   pixel dopings ( 921 ,  922 ,  1111 ,  1112 ,  121 ,  122 ) of semiconductor of the second conductivity type, which pixel dopings are adapted to be coupled to at least one pixel voltage in order to create a source and a drain of a pixel-specific transistor;   
       wherein the device further comprises a first conductivity type first contact, said pixel voltage being defined as a potential difference between one of the pixel dopings and the first conductivity type first contact, and a main gate ( 983 ) the location of which corresponds at least partly to the location of a channel between said source and said drain, 
       wherein:
 the at least one pixel further comprises at least one extra gate ( 981 ,  982 ) next to the main gate ( 983 ) and the location of the at least one extra gate ( 981 ,  982 ) corresponds at least partly to the location of a channel between said source and said drain and wherein the at least one extra gate ( 981 ,  982 ) is external to said semiconductor material of the first conductivity type and the second conductivity type. 
 
     
     
       2. The semiconductor radiation detector device according to  claim 1 , comprising two extra gates, the location of a first extra gate is towards said source from the main gate, and the location of the other extra gate is towards said drain from the main gate. 
     
     
       3. The semiconductor radiation detector device according to  claim 2 , wherein each extra gate is located above a corresponding MIG border region at which a part of said channel is vertically aligned with an edge of said MIG layer. 
     
     
       4. The semiconductor radiation detector device according to  claim 1 , wherein each extra gate is located above a corresponding MIG border region at which a part of said channel is vertically aligned with an edge of said MIG layer. 
     
     
       5. The semiconductor radiation detector device according to  claim 1 , wherein said channel goes through a buried channel layer that connects said source and said drain on an opposite side of said barrier layer than said MIG layer. 
     
     
       6. The semiconductor radiation detector device according to  claim 1 , comprising electrically insulating material that separates said main gate and said extra gate or extra gates from said channel. 
     
     
       7. The semiconductor radiation detector device according to  claim 6 , wherein a common layer of electrically insulating material encapsulates both said main gate and said extra gate or extra gates. 
     
     
       8. The semiconductor radiation detector device according to  claim 1 , comprising in said MIG layer a region the net doping of which is higher than the net doping of the remaining MIG layer around said region, wherein said region is vertically aligned with said main gate. 
     
     
       9. The semiconductor radiation detector device according to  claim 1 , comprising a reset gate ( 682 ,  782 ) underneath of which the doping of the MIG layer ( 842 ) and barrier layer ( 852 ) is weaker than underneath the main gate ( 983 ). 
     
     
       10. The semiconductor radiation detector device according to  claim 9 , wherein said reset gate ( 682 ) is horizontally displaced from said main gate ( 181 ), and wherein both said reset gate ( 682 ) and said main gate ( 181 ) are located above a gap that separates said source ( 111 ) and said drain ( 112 ). 
     
     
       11. The semiconductor radiation detector device according to  claim 9 , wherein:
 said field-effect transistor is a first field-effect transistor of a pixel in the device, which pixel comprises also a second field-effect transistor that comprises a second source and a second drain,   said reset gate is simultaneously a transfer gate that is located above a gap that separates the field-effect transistors of the pixel.   
     
     
       12. The semiconductor radiation detector device according to  claim 1 , comprising at least two pixel-specific selection transistors which have different threshold voltages. 
     
     
       13. A semiconductor radiation detector device comprising at least one pixel, wherein the at least one pixel comprises a semiconductor substrate and on one surface of the substrate the semiconductor radiation detector comprises:
 a first conductivity type well doping,   a second conductivity type source doping and a second conductivity type drain doping inside said first conductivity type well doping,   an opening in the first conductivity type well doping located in between said source doping and said drain doping,   a first layer of semiconductor of second conductivity type, hereinafter the MIG layer, said MIG layer located in said opening of the first conductivity type well doping,   a barrier layer of a semiconductor of first conductivity type arranged directly on the MIG layer in between the MIG layer and said one surface of the substrate and located in said opening of the first conductivity type well doping, said barrier layer configured to form a potential energy barrier for signal charges accumulated in said MIG layer during operation of the semiconductor radiation detector device,   a channel between said source and said drain as well as between said one surface and said barrier layer, said channel carrying charges of said second conductivity type,   a main gate external to the semiconductor substrate and located in between said source doping and said drain doping as well as on said opening in the first conductivity type well doping above said channel,   
       wherein:
 the at least one pixel further comprises at least one extra gate external to the semiconductor substrate and located in between the main gate and the second conductivity type source doping or drain doping wherein the at least one extra gate is located above a boundary of said well doping and said opening, and wherein the at least one extra gate is adapted to be coupled to a potential such that the channel resistance is lower beneath the at least one extra gate than beneath the main gate such as to create inside the semiconductor substrate underneath the extra gate:
 an artificial source if the extra gate is located in between the second conductivity type source doping and the main gate, or 
 an artificial drain if the extra gate is located in between the second conductivity type drain doping and the main gate. 
 
 
     
     
       14. The semiconductor radiation detector device according to claim 13, wherein the semiconductor radiation detector device comprises two extra gates, the location of a first extra gate is in between the second conductivity type source doping and the main gate, and the location of the other extra gate is in between the second conductivity type drain doping and the main gate. 
     
     
       15. The semiconductor radiation detector device according to claim 13, wherein a buried channel layer of semiconductor of second conductivity type is arranged directly on said barrier layer in between the barrier layer and said one surface of the substrate and located in said opening of the first conductivity type well doping, and wherein said channel goes through said buried channel layer. 
     
     
       16. The semiconductor radiation detector device according to claim 13, comprising electrically insulating material that separates said main gate and said extra gate or extra gates from said channel. 
     
     
       17. The semiconductor radiation detector device according to claim 13, wherein a common layer of electrically insulating material encapsulates both said main gate and said extra gate or extra gates. 
     
     
       18. The semiconductor radiation detector device according to claim 13, comprising in said MIG layer a region a net doping of which is higher than a net doping of the remaining MIG layer around said region, wherein said region is vertically aligned with said main gate. 
     
     
       19. The semiconductor radiation detector device according to claim 13, comprising next to said main gate on said opening of the first conductivity type well doping a reset gate underneath of which the doping of the MIG layer and barrier layer is weaker than underneath the main gate. 
     
     
       20. The semiconductor radiation detector device according to claim 19, wherein said second conductivity type source doping, said second conductivity type drain doping and said main gate correspond to a first field-effect transistor, 
       and wherein the semiconductor radiation detector device further comprises a second field-effect transistor comprising a second source, a second drain and a second main gate, said second main gate located in said opening of the first conductivity type well doping
 said reset gate is located in between said main gate and said second main gate and said reset gate acting also as a transfer gate. 
 
     
     
       21. The semiconductor radiation detector device according to claim 13, comprising at least two pixel-specific selection transistors having different threshold voltages. 
     
     
       22. A semiconductor radiation detector device comprising at least one pixel, wherein the at least one pixel comprises a semiconductor substrate and on one surface of the substrate the semiconductor radiation detector comprises:
 a first conductivity type well doping,   a second conductivity type source doping and a second conductivity type drain doping inside said first conductivity type well doping,   an opening in the first conductivity type well doping located in between said source doping and said drain doping,   a first layer of semiconductor of second conductivity type, hereinafter the MIG layer, said MIG layer located in said opening of the first conductivity type well doping,   a barrier layer of a semiconductor of first conductivity type arranged directly on the MIG layer in between the MIG layer and said one surface of the substrate and located in said opening of the first conductivity type well doping, said barrier layer configured to form a potential energy barrier for signal charges accumulated in said MIG layer during operation of the semiconductor radiation detector device,   a channel between said source and said drain as well as between said one surface and said barrier layer, said channel carrying charges of said second conductivity type,   a main gate external to the semiconductor substrate and located in between said source doping and said drain doping as well as on said opening in the first conductivity type well doping above said channel,   
       wherein:
 the at least one pixel further comprises next to said main gate on said opening of the first conductivity type well doping a reset gate underneath of which the doping of the MIG layer and barrier layer is weaker than underneath the main gate. 
 
     
     
       23. The semiconductor radiation detector device according to claim 22, wherein a buried channel layer of semiconductor of second conductivity type is arranged directly on said barrier layer in between the barrier layer and said one surface of the substrate and located in said opening of the first conductivity type well doping, and wherein said channel goes through said buried channel layer. 
     
     
       24. The semiconductor radiation detector device according to claim 22, comprising at least one extra gate external to the semiconductor substrate and located in between the main gate and the second conductivity type source doping or drain doping wherein the at least one extra gate is located above a boundary of said well doping and said opening, and wherein the at least one extra gate is adapted to be coupled to a potential such that the channel resistance is lower beneath the at least one extra gate than beneath the main gate such as to create inside the semiconductor substrate underneath the extra gate:
 an artificial source if the extra gate is located in between the second conductivity type source doping and the main gate, or   an artificial drain if the extra gate is located in between the second conductivity type drain doping and the main gate.   
     
     
       25. The semiconductor radiation detector device according to claim 24, wherein the semiconductor radiation detector device comprises two extra gates, the location of a first extra gate is in between the second conductivity type source doping and the main gate, and the location of the other extra gate is in between the second conductivity type drain doping and the main gate. 
     
     
       26. The semiconductor radiation detector device according to claim 22, comprising in said MIG layer a region a net doping of which is higher than a net doping of the remaining MIG layer around said region, wherein said region is vertically aligned with said main gate. 
     
     
       27. The semiconductor radiation detector device according to claim 22, wherein said second conductivity type source doping, said second conductivity type drain doping and said main gate correspond to a first field-effect transistor, 
       and wherein the semiconductor radiation detector device further comprises a second field-effect transistor comprising a second source, a second drain and a second main gate, said second main gate located in said opening of the first conductivity type well doping:
 said reset gate is located in between said main gate and said second main gate and said reset gate acting also as a transfer gate. 
 
     
     
       28. The semiconductor radiation detector device according to claim 22, comprising at least two pixel-specific selection transistors having different threshold voltages.