Dear Tim,
You wrote:
"I am not sure it is that unlikely a structure as the surface layers
need to
include quite a few layers including a passivation layer, at least one
metalization layer to bring in connections (possibly 2) at least one
layer
for the filters and possibly three seperate layers (1 for each color)
and
maybe even passivation layers between each of those."
The metallisation layers are likely to be sub-micron, youre right about
the "filling factor" for the sensing element itself. I've been
calculating on the assumption that the sensors fill completely the chip
chip, but I was trying to give some useful approximations. I think in an
RGB chip, the filter layers will not be one on top of another, but will
be side by side. They are likely to be the thickest layer, and could be
several microns. However, thick layers are notoriously difficult to
pattern so I think they would go for a thin layer of something with a
high absorption coefficient.
That said the undercutting that one gets when etching thick layers such
as the filter could be used to approximate a hemispherical lens on top
of each element, wich would help gather the low angle rays.
"In a a non RGB sensor as
is used in a dichroic beam splitter design the pixels are
proportionately
larger and don't need all the filter layers so the signals are larger by
a
factor of 3 and they don't have such deep wells. For analytic
applications as
your coleagues are probably using (?), the same thinner design
applies,since
they don't need on chip filters. "
I did say at one point that I was ignoring the effect of small pixel
sizes on noise levels but this would need to be considered.
My colleagues don't use them for analytical applications but for a
variety of imaging applications. The UK MoD requires us to retain
experise and knowledge base in all aspects of miltary and commercially
available devices, hence they know a lot about commercially available
devices, even when they don't have an immediate use for them.
Can you send me the full reference for the Kodak paper as it looks
useful? should be able to get a copy from our library.
Chris
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