Hi Shifeng,

Narrow lines are very hard to deposit by evaporation because as the metal is
deposited on top of the resist, it builds up along the edges of the pattern and
eventually will close the gap entirely.  This presents two problems: the first,
as you have experienced, liftoff is difficult because the solvent is unable to
penetrate the closed pattern of metal; second, if you do manage to remove the
metal, you will most likely find that the cross-section of the metal pattern is
tapered to a point at the top for the same reason.  This may not be a problem if
you have a device that does not require the lines to carry a lot of current, but
if there is too much current it will act as a fuse.

If the sample is important to recover, you may try to remove the metal by using
a low-tack adhesive tape.  By pressing the tape lightly on the surface and then
peeling it away, you may be able to remove the metal from the photoresist,
exposing the resist which can then be stripped normally.

Brad Cantos
[email protected]
http://holage.com




On Mar 10, 2010, at 4:44 PM, li shifeng wrote:

> Hi, All,
>
> I pattened 100nm lines on the glass substrate. The height of the line is
around 250nm. I used an e-beam evaportor to deposit 5nm Ti and 80nm Au. I found
it is very hard to lift off. What are the possible reasons?  Any suggestions to
succeed with an Au lift off process for smaller patterns?
>
> Thanks!
>
> Shifeng