| AVS 54th International Symposium | |
| Nanometer-scale Science and Technology | Friday Sessions |
| Session NS-FrM |
| Session: | Nanolithography and Nanoprocess Technology |
| Presenter: | H. Schift, Paul Scherrer Institute, Switzerland |
| Authors: | H. Schift, Paul Scherrer Institute, Switzerland S. Bellini, ETH Zürich, Switzerland H. Sehr, Paul Scherrer Institute, Switzerland J. Gobrecht, Paul Scherrer Institute, Switzerland |
| Correspondent: | Click to Email |
Stamps for nanoimprint lithography (NIL)1 need an excellent anti-sticking surface property, which is easy to achieve with silane chemistry, if molds are made from silicon.2 Other stamp materials, such as metals, need intermediate layers, preferably made from silicon oxide (SiO2).3 Then the chlorosilane group of commercially available fluorinated silanes can react with hydroxyl groups on the oxide surface under elimination of hydrochloric acid, and covalent binding can be achieved which is durable in hot embossing and injection molding processes. Two routes were developed to achieve a thin intermediate coating of stamps, one based on the thermal evaporation of Ti/SiO2, and the other on Plasma Enhanced Chemical Vapor Deposition (PECVD) of SiO2. Since evaporation is directed, a full conformal coverage of the surface, particularly if high aspect ratio structures need to be coated, is often only achieved with specific mounting setups or several subsequent coating steps from different directions. This is time consuming due to the evacuation steps and only results in limited thickness homogeneity. Therefore the PECVD was developed and applied on different metals (brass, nickel, steel) without the use of the Ti adhesion promoter. The process is conformal and 20 nm thick coatings can be achieved with high homogeneity. It is more flexible and can be performed within a few minutes. The most crucial point is the adhesion of the thin interlayer to the stamp surface during the demolding process. The durability of both layers was tested using different mechanical methods and coated molds were used in hot embossing and injection molding. Several thousand injection molding cycles are possible, and to date is seems that the durability of the new PECVD coating matches that of the evaporated films. This is a further step to establish anti-sticking coating techniques in high volume manufacturing of polymer parts by replication, and to enlarge the range of stamp materials used for molding and NIL.
1 Schift H., Kristensen A., In Handbook of Nanotechnology, Vol. ed. B. Bhushan, second edition, Springer Verlag, Berlin, Germany, 239-278 (2007).
2 Schift H., Saxer S., Park S., Padeste S., Pieles U., Gobrecht J., Nanotechnology 16, S171-S175 (2005).
3 Park S., Schift H., Padeste C., Schnyder B., Kötz K., Gobrecht J., Microelectronic Eng. 73-74, 196-201 (2004).