Microlens Structure for Image Sensors

Abstract

A microlens structure and a method of fabrication thereof are provided. The method comprises forming a layer of microlens material over a substrate, which has photo-sensitive elements formed therein. The microlens material, which comprises a photo-resist material, is exposed in accordance with a desired pattern a plurality of times. The energy used with each exposure process is less than the energy required if a single exposure is used. Furthermore, the masks used for each exposure may differ. In an embodiment, the masks are varied so as to create a notch in the upper corner of the microlens. The microlens structure may have a height less than about 0.5 um and/or a gap between microlenses less than about 0.2 um. In an embodiment, one or more dielectric layers having a combined thickness greater than about 3.5 um are interposed between the photo-sensitive elements and the microlenses.

1 . An image sensing semiconductor device comprising:
 a substrate having an image sensing portion and a logic portion, the image sensing portion having a plurality of photo-sensitive devices formed thereon and the logic portion having one or more interconnection layers; and   a plurality of microlenses, at least one microlens being formed over one or more of the plurality of photo-sensitive devices, the microlenses being less than 0.5 um in height.   
   
   
       2 . The image sensing semiconductor device of  claim 1 , wherein a gap between the microlenses is less than about 0.2 um. 
   
   
       3 . The image sensing semiconductor device of  claim 1 , wherein a gap between the microlenses is less than about 0.1 um. 
   
   
       4 . The image sensing semiconductor device of  claim 1 , wherein the logic portion includes more than about 4 interconnection layers. 
   
   
       5 . The image sensing semiconductor device of  claim 1 , wherein the photo-sensitive devices are CMOS image sensors. 
   
   
       6 . The image sensing semiconductor device of  claim 1 , wherein the photo-sensitive devices are CCD image sensors. 
   
   
       7 . The image sensing semiconductor device of  claim 1 , further comprising one or more dielectric layers between the microlenses and the photo-sensitive devices. 
   
   
       8 . The image sensing semiconductor device of  claim 7 , wherein the one or more dielectric layers have a combined thickness greater than about 3.5 um. 
   
   
       9 . An image sensing semiconductor device comprising:
 a substrate having an image sensing portion, the image sensing portion having a plurality of photo-sensitive devices formed thereon; and   a plurality of microlenses, at least one microlens being formed over one or more of the plurality of photo-sensitive devices, a gap between the microlenses is less than about 0.2 um.   
   
   
       10 . The image sensing semiconductor device of  claim 9 , wherein the microlenses are less than 0.5 um in height. 
   
   
       11 . The image sensing semiconductor device of  claim 9 , wherein the gap between the microlenses is less than about 0.1 um. 
   
   
       12 . The image sensing semiconductor device of  claim 9 , further comprising one or more dielectric layers between the microlenses and the photo-sensitive devices. 
   
   
       13 . The image sensing semiconductor device of  claim 12 , wherein the one or more dielectric layers have a combined thickness greater than about 3.5 um. 
   
   
       14 . An image sensing semiconductor device comprising:
 a substrate having an image sensing portion, the image sensing portion having a plurality of photo-sensitive devices formed thereon;   a plurality of microlenses, at least one microlens being formed over one or more of the plurality of photo-sensitive devices; and   one or more dielectric layers between the microlenses and the photo-sensitive devices, the one or more dielectric layers having a combined thickness greater than about 3.5 um.   
   
   
       15 . The image sensing semiconductor device of  claim 14 , wherein the microlenses are less than about 0.5 um in height. 
   
   
       16 . The image sensing semiconductor device of  claim 14 , wherein a gap between the microlenses is less than about 0.2 um. 
   
   
       17 . The image sensing semiconductor device of  claim 14 , wherein a gap between the microlenses is less than about 0.1 um.