The photodiode used by the Foveon F018-50-
F19A is unique in that three cathode implants
are used, one for each of the red (R), green (G),
and blue (B) colours as different depths below
the slicon surface. Figure 7 is a Scanning
Capacitance Microcopy (SCM) image of the
stacked RGB photo-cathodes embedded in the
P-epitaxial layer. The blue photo cathode is seen
along the top of the photodiode. This N-type
cathode implant is appoximately 0.10 μm deep.
The green photo-cathode is nearly 0.65 μm thick.
It extends from a depth of approximately 0.90
μm to 1.6 μm. An N-sinker diffusion, located at
the right end of the cathode, rises towards the
surface, where it meets the green transfer
transistor. the approximately 0.75 μm thick red
photo-cathode lies in a depth range of
approximately 2.7 μm to 3.5 μm.