Tfa image sensor with stability-optimized photodiode

Abstract

The invention relates to a TFA image sensor with stability-optimized photodiode for converting electromagnetic radiation into an intensity-dependent photocurrent with an intermetal dielectric, on which, in the region of the pixel matrix, a lower barrier layer is situated and a conductive layer is situated on the barrier layer, and vias being provided for the contact connection to the ASIC, the vias in metal contacts on the ASIC. A TFA image sensor having improved electrical properties is provided. This is achieved in that an intrinsic absorption layer is provided between the TCO layer and the barrier layer with a layer thickness of between 300 nm and 600 nm. Before the application of the photodiodes, the topmost, comparatively thick metal layer of the ASIC is removed and replaced by a matrix of thin metal electrodes which form the back electrodes of the photodiodes, the matrix being patterned in the pixel raster.

1 . A TFA image sensor with stability-optimized photodiode for converting electromagnetic radiation into an intensity-dependent photocurrent with an intermetal dielectric, on which, in the region of the pixel matrix, a lower barrier layer is situated and a conductive layer is situated on said barrier layer, and vias being provided for the contact connection to the ASIC, said vias ending in metal contacts on the ASIC, wherein an intrinsic absorption layer is provided between the TCO layer and the barrier layerwith a layer thickness of between 300 nm and 600 nm.  
   
   
       2 . The TFA image sensor as claimed in  claim 1 , wherein the layer thickness of the intrinsic absorption layer is approximately 450 nm.  
   
   
       3 . The TFA image sensor as claimed in  claim 1 , wherein the band gap of the intrinsic absorption layer of the photodiode is increased.  
   
   
       4 . The TFA image sensor as claimed in  claim 1 , wherein the increase in the band gap is realized by using an amorphous silicon-carbon alloy (a-Sic:H) as absorption layer.  
   
   
       5 . The TFA image sensor as claimed in  claim 1 , wherein, in particular, the photodiode of reduced layer thickness is arranged on a surface that is as planar as possible.  
   
   
       6 . The TFA image sensor as claimed in  claim 1 , wherein the photodiode with small intrinsic layer thickness is deposited on an ASIC having a flat surface topography.  
   
   
       7 . The TFA image sensor as claimed in  claim 1 , wherein the ASIC is coated with a passivation.  
   
   
       8 . The TFA image sensor as claimed in  claim 1 , wherein, within the pixel matrix, firstly the back electrodes of all the pixels are connected to one another via the topmost CMOS metal plane, which is made planar in the region of the pixel matrix.  
   
   
       9 . The TFA image sensor as claimed in  claim 8 , wherein the metal plane is situated on a CMP-planarized surface (CMP=Chemical Mechanical Polishing) of the topmost intermetal dielectric layer.  
   
   
       10 . A method for fabricating a TFA image sensor as claimed in  claim 1 , wherein, before the application of the photodiodes, the topmost, comparatively thick metal layer of the ASIC is removed and replaced by a matrix of thin metal electrodes which form the back electrodes of the photodiodes, said matrix being patterned in the pixel raster.  
   
   
       11 . The method as claimed in  claim 10 , wherein an antireflection layer that is present and the metal layer are completely removed above the pixel matrix, so that all that remains is the barrier layer situated underneath.  
   
   
       12 . The method as claimed in  claim 10 , wherein the lower barrier layer is completely removed, this then being followed by the deposition and patterning of the further metal layer in the form of pixel back electrodes.  
   
   
       13 . The method as claimed in  claim 10 , wherein the ASIC passivation is opened in the photoactive region of the TFA sensor.  
   
   
       14 . The method as claimed in  claim 10 , wherein the antireflection layer of the upper metallization layer of the ASIC in the photoactive region of the TFA sensor is removed.  
   
   
       15 . The method as claimed in  claim 10 , wherein the conductive layer of the upper metallization layer of the ASIC in the photoactive region of the TFA sensor is removed.  
   
   
       16 . The method as claimed in  claim 10 , wherein the lower barrier layer of the upper metallization layer of the ASIC in the photoactive region of the TFA sensor is patterned or removed.  
   
   
       17 . The method as claimed in  claim 16 , wherein a further metal layer is deposited and patterned.  
   
   
       18 . The method as claimed in  claim 17 , wherein further layers, such as color filter layers, are deposited and patterned.  
   
   
       19 . A method for fabricating a TFA image sensor as claimed in  claim 1 , wherein 
 the ASIC passivation in the photoactive region of the TFA sensor is opened,    the antireflection layer of the upper metallization layer of the ASIC in the photoactive region of the TFA sensor is removed,    the conductive layer of the upper metallization layer of the ASIC in the photoactive region of the TFA sensor is removed,    the lower barrier layer of the upper metallization layer of the ASIC in the photoactive region of the TFA sensor is patterned or removed,    a further metal layer is deposited and patterned,    the photodiode layers are deposited and patterned, and    further layers, such as color filter layers, are deposited and patterned.