Mike,

You can sputter metal/metal-oxide or metal-nitride film gradients on glass
to produce good black films.It is possible to get black with films as thin
as 100nm.

Regards,
Glenn

-----Original Message-----
From: Mike Whitson [mailto:[email protected]]
Sent: Thursday, January 05, 2012 7:03 AM
To: General MEMS discussion
Subject: [mems-talk] Optical absorbing material


Hello all,

I'm trying to identify possible materials / vendors for a broadband
(vis-MWIR) optical absorbing layer to be integrated in an optical MEMS
device.  In the past, we've used a spin-coatable black polyimide for the
purpose (purchased from Brewer), but they no longer make or sell the
material.  Wondering if anyone has suggestions for an alternative vendor or
material.  What we're looking for:

* High broadband optical absorption.  Ideally a single material spanning the
entire range from ~300-5000 nm would be good, but sets of materials with
broad absorption bands (eg one for visible, one for 3000 - 5000 nm) would
also work.  Ideally absorption should be high enough to perform well at
sub-wavelength coating thicknesses.

(Good absorption at i- and g-line wavelengths to act as a kind of BARC
during photolithography would be a bonus, but not a requirement.)

* Spin coatable.

* Electrical resistivity as high as possible.  Given that one way to make
such a material is by impregnating carbon black in a polymer matrix, I
understand that getting a truly insulating material may be tough.

* Patternable.  Ideally a diretly photopatternable material would be
wonderful; if not, something amenable to a lift-off or etch process (say O2
RIE with a hard mask) would be sufficient.

* Long life.  This will be a permanent part of the optical device; polymers
that can be crosslinked or otherwise cured would be preferable.

If anyone has suggestions for vendors or even particular materials, I'd be
grateful.

-Mike