Chemistry Reference
In-Depth Information
Figure 3.22. Schematic diagram of the process of the NIL technique. The mas-
ter, the organic film and the substrate are represented by black, grey and white
components, respectively.
e.g., by vapour deposition, essentially by the process known as graphoepitaxy
(Moulin
et al.
, 2002).
Nanoimprint lithography
One of the most successful lithographic techniques is nanoimprint lithography
(NIL), mainly because both its working principle and operation are quite simple
(Chou
et al.
, 1996). A schematic diagram of the NIL technique is shown in
Fig. 3.22.
NIL uses a hard mould or master containing nanoscale features defined on its
surface ready to emboss into an organic material prepared on a substrate by e.g.,
vapour deposition, spin-coating, etc., thus creating a thickness contrast in the or-
ganic material. NIL has the capability of patterning down to
c
. 10 nm features. Hard
moulds are usually made of silicon and the grating is fabricated by well-established
lithographic techniques such as electron beam or interference lithography. Once
the mould grating is available the processing is rather simple. Gratings are used as
stamps and pressed against the organic film. After release of the mask the pattern is
transferred to the film. This is analogous to a classical typewriter used without the
ink tape. This is the reason why expectations are high for this deposition method.
The NIL process can be performed either in air or under controlled conditions (vac-
uum, inert gas atmosphere), depending on the stability of the organic materials and
on the relevance of contaminants, e.g., oxygen and water, which are detrimental
e.g., for OLEDs. Examples of NIL-patterned light-emitting films preserving their
