Hi Darren,

The photo is somewhat hard to interpret, but if you try to SEM the photoresist
profile, you would probably see a very shallow angle on the resist edge cross-
section.  This could be due to the lack of edge sharpness of the mask, but in
any case, your intuition is correct that it would not make a good lift-off
profile.

It appears that a couple of things may be going on:

1. The resist may be underexposed.  Try using more exposure.  This is a simple
experiment, but likely to fail.

2. Since you are using a film mask, and assuming that you are using contact
photolithography, it is very likely that you are not making good contact between
the mask and the resist.  This is the nature of film masks.

For the best lift-off, you should use either a resist designed for lift-off or,
if it is available, an image-reversal oven.  In either case, you may need a
reverse polarity mask as these are mostly negative acting.  But above all, if
you need sharp edges, use a chrome mask, or even a photo-emulsoion mask (if they
even still make these).

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


On 15 Aug 2010, at 5:11 PM, Darren Alvares wrote:

> Hi All,
>
> I am using a photoplotted transparency mask to pattern resist for a lift off
process. I have a series of lines I have exposed. See image:
http://yfrog.com/mhimage31np
>
> Looking at the pattern under the microscope indicates that there is no sharp
edge on the corner. I have used AZ6632 positive resist. To me this doesn't look
like it will be successful with lift off.
>
> This lines are smallest to largest 10,20,30..um.
>
> Any suggestions or thoughts on:
>
> -Whether lift off will occur.
> -What could be the problem. Resist, Exposure Time, Baking, Proper Contact with
substrate?
>
> Looking forward to hearing from you regarding this.
>
> Cheers,
> Darren