Isolation method for low dark current imager
View Patent ↗A method for forming the passivation layer for silicon-isolation interface between photosensitive regions of an image sensor, the method includes providing a substrate having a plurality of spaced apart photosensitive regions that collect charge in response to incident light; etching trenches in the substrate between the photosensitive regions; forming a plurality of masks over the photosensitive regions so that trenches between the photosensitive regions are not covered by the masks; implanting the image sensor with a first low dose to passivate the trenches; filling the trenches with a dielectric to form isolation between the photosensitive regions; forming a plurality of masks which cover the photosensitive regions but does not cover a surface corner of the isolation trench to permit passivation implantation at the surface corner of the trench isolation; and implanting the image sensor at a second low dose to passivate the surface corner of trenched isolation region.
1. A method for forming the passivation layer for silicon-isolation interface between photosensitive regions of an image sensor, the method comprising:
(a) providing a substrate having a plurality of spaced apart to-be formed photosensitive regions that collect charge in response to incident light;
(b) etching trenches in the substrate between the to-be formed photosensitive regions;
(c) forming a plurality of masks over the to-be formed photosensitive regions so that trenches between the to-be formed photosensitive regions are not covered by the masks;
(d) implanting the image sensor with a first low dose to passivate the trenches;
(e) filling the trenches with a dielectric to form isolation between the to-be formed photosensitive regions;
(f) forming a plurality of masks which cover the to-be formed photosensitive regions but does not cover a surface corner of the isolation trench to permit passivation implantation at the surface corner of the trench isolation; and
(g) implanting the image sensor at a second low dose to passivate the surface corner of trenched isolation region.
2. A method as in claim 1 wherein step (d) includes passivating a bottom and side of the trenches.
3. The method as in claim 1 further comprising the step of providing oxide as the dielectric.