Hi to all,
             Can anybody suggest me on this problem...i deposited first
Ni(40nm) and then Au(80nm) on both Si and GaN after patterning for the Lift-off
process...but at the time of Lift-off the whole deposited metal got stripped
away...actually after deposition at room temperature i just heated it in-situ
(in vacuum) at 100C for one hour...
Is this the problem of sticking of Ni with Si and GaN or some other
problem...Suggest me...

Thank You
Hare Krishna
M.Tech Student
IIT Kanpur
India

Christopher Striemer  wrote:

Hi Tao,

A period of 1.5um should be fairly easy to achieve with that laser, even
with the crossed exposure (are you after a 2-D array of holes or
pillars?). Many things could cause your problem, but my best two guesses
are:
1) Reduce your intensity by spreading out your beam. If your features
are gone after 3s develop, you are way over-exposed for a positive resist
like 1805. Since your time is already short, you have to reduce
intensity.
2) There is probably non-uniformity in your optical field. Issues like
spatial filtering, uniform power in both beams, minimizing stray laser
scatter (coherent), and having a minimum number of optical elements in the
beam path can help here.

Good Luck!!

---Chris Striemer striemer@ece.rochester.edu


>Date: Thu, 27 May 2004 15:10:03 -0700
>From: tao liu

>Reply-To: General MEMS discussion
>To: mems-talk@memsnet.org
>Subject: [mems-talk] About laser holography
>
>Hi,
>
>I use HeCd laser to do holography with two-beam interference. The
>wavelength is 446nm. My sample is PR1805/SiO2/GaAs. The period is
>1.5um. The sample is exposed twice to form a crossed grating. After
>exposure and development, I can always see the non-uniformity on the
>sample surface: some area has good exposure, some area has
>under-exposure, and some area has over-exposure. Because the time for
>a single exposure is only ~ 3s and the development is also only ~ 3s,
>I suspect that this is caused by the very short development time. (I
>cannot use long development time for my present conditions. Otherwise
>all the patterns will be lost.) Can anybody give me some hints for
>that? Thanks.
>
>Best regards,
>
>Tao






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