Georg,

I found in that you must have temperature control to reduce
the bubbling you have experienced.  The other option
is to reduce the total amount of flux (using a narrow slit)
hitting the sample.  This problem is especially bad if you
are not scanning your sample.  You have several possibilities
for cooling.  (1) blow cold, cold air over the PMMA.  (2) put
the PMMA on a piece of cooled aluminum (this is best).
I used method (2) in all my exposures and was able to get
very high doses delivered at very high fluence rates.

-Reid


    Dear colleagues,

    I am working on deep x-ray lithography in PMMA up to 1 cm and I am having
    problems with rough surfaces. (Often bubble like structures though I don't
    overexpose).

    I am trying to find out more about PMMA radiation damage and PMMA
    development in very deep structures. Especially effects occuring when one
    overexposes or exposes with high ratio (gasing out, gas diffusion speed in
    PMMA etc.) are things I would be very interested in!

    Can anyone help me find appropriate literature?
    Can anyone share their own experiences?
    I would also like to get in contact with people doing experiments in the
    same field.

    Best regards

    Georg

    -------------------------------------
    Georg Aigeldinger, Research Associate
    Center for Advanced Microstructures and Devices, CAMD
    Louisiana State University
    Baton Rouge, LA 70803, USA





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.______________________________________________________________________.
|Reid (Turtle) Alyn Brennen                Hewlett-Packard Laboratories|
|rbrennen@hpl.hp.com                       Chemical Systems Department |
|(650) 857-4469 office                     3500 Deer Creek Road, MS 26U|
|(650) 852-8502 Fax                        Palo Alto, CA 94303-0867    |
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