Well-ordered structures across an entire wafer can be produced (see image 3) if LIL is used. This technique allows to generate very small structures at a resolution of less than 100 nm with photoresists (see also AR NEWS 22. issue, April 2011).
One problem of LIL applications however are the “standing waves“ which may occur during exposure. Image1demonstrates the patterning of a commonly used negative resist with interference lithography. Clearly visible are the maxima and minima of the “standing wave” in the 100 nm stripes, some of which have even tipped over. The use of anti-reflective layers may inhibit the formation of these annoying waves.
But there are more simple ways…
This interfering effect is more or less masked if the new experimental sample SX AR-N 4340/8 is used. Image 2 shows 60-nm stripes produced with this resist. Due to the principle of chemical enhancement of the resist, the effect of the “standing waves“ is eliminated. It is thus possible to produce vertical side walls and, if required, even an undercut for lift-off procedures. All samples were exposed at 20° (nominal spacing 389 nm) and a laser wave length of 266 nm.
These investigations were carried out by Dr. Fuhrmann, IZM of the Martin-Luther University Halle, under the direction of Prof. Dr. G. J. Schmidt. For product developments, Allresist intensively cooperates with ambitious research facilities.
Further results will be published in our next AR NEWS. We will be glad to answer your questions with respect to this application already now.
These interesting results prompted us to choose SX AR-N 4340/8 as resist of the month.
[Bild] „Interference structure“ /wMedia/img/klein/RdMJan13_1.jpg
Image 1 Interference structure with AR-N 4240
[Bild] „60-nm stripes“ /wMedia/img/klein/RdMJan13_2.jpg
Image 2 60-nm stripes of SX AR-N 4340/8
[Bild] „LIL- Metal deposition “ /wMedia/img/klein/RdMJan13_3.jpg
Image 3 LIL – Metal deposition lift-off- Si RIE etching for the manufacture of Si-n anowires (all images by: IZM of the MLU Halle)