Please click on the address for the pictures:

ftp://public00:00public@thorium.recherche.gme.usherb.ca/public00

Hi,

We are trying to fabricate some beams but we have some problems making them
straight. As you can see in picture #1, the rod is falling.  In picture #2, the
beam is rising.  We also noticed that there's an angle in the deposition, see
picture #3. The base is larger than the top (i.e. there's more Si at the
bottom).  This probably cause some mechanical stress.


We use a Si substrate with some SiO2 on it and resist.  We do a lithography and
then, we evaporate Si using an electron canon.  We evaporate 1.8 microns at a
rate of 5 Amstrong/sec. and we do not control the temperature in the evaporator.
 The Si is evaporated on the SiO2 and the resist.  After that, we lift-off the
resist and then in order to liberate some parts or the structure, we wet etch
(B.O.E.) the SiO2.


We suspect that the problem comes from the evaporation, more precisely from an
elevation of temperature. We think that the temperature of the beam gets higher
the more we evaporate Si which causes the angle in picture #3 (caused by
residual stress).  Unfortunatly, we're not sure if this is the source of the
problem or if it's something else (e.g. stiction). Any suggestions that would
make our beams straighter or fabrications techniques to make straight beams
would be greatly appreciated.


Thanks,


Guy Haché, M.Sc.A.
Assistant de recherche, research assistant
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Département de génie électrique et de génie informatique
Université de Sherbrooke
2500, boulevard Université
Sherbrooke (Québec) Canada
J1K 2R1
Téléphone.:  (819) 821-8000 3706
Télécopieur:  (819) 821-7937
e-mail: guy.hache@usherbrooke.ca
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