CHARPAN

Charged Particle Nanotech

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Achievements in Industrial Applications

In March 2007 the first resist-less 3D nanopatterning of surfaces was accomplished by realizing a 10 x 10 matrix of microlenses with nanometer surface definition.

A 10 x 10 array of microlenses was produced in different materials (a):

On a Silicon wafer surface a 10 x 10 array of convex microlenses was sputtered using the 10keV Argon ion multi-beam of the CHARPAN PMLP POC Tool.
On a GaAs wafer surface a 10 x 10 array of concave microlenses was produced using the 10keV Argon ion multi-beam of the CHARPAN PMLP POC Tool.

As expected, surfaces were shown to be extremely smooth [SEM image: PHILIPS Research].
Prolonged sputtering of GaAs led to the formation of cones (b) due to redepositioning of sputtered material. This behaviour had been expected due to simulations performed. The regular array of smooth cones produced may well proof of interest for emerging applications.
With respect to exploring the potential of the CHARPAN technology to fabricate plasmon colour filters an important study on colour reconstruction using metallic colour filters has been performed at CEA - LETI.

Another application CHARPAN which has always been addressed by the project is 3D template fabrication for Nano Imprint Lithography (NIL). The work performed by Butschke et al.^[3] at IMS Chips together with Molecular Imprints outlines an improved process for producing high resolution 1x templates for Dual Damascene NIL. The process involves patterning with particle beams, which was executed by single-beam e-beam writing for the time being.

Likewise processes used in Step and Flash Imprint Lithography and corresponding template requirements were analysed by J. Kettle, G. Lalev and S. Dimov of Cardiff University. This included the fabrication of lenses for LEDs (in particular AlGaInP LEDs)^[4], of patterned 3-Nickel components^[5] and the development of functional materials^[6].

Yet another extremely import field of PMLP applications will be the generation of complex masks. Here, resist-less processes like the one suggested by Butschke and others from IMS Chips and IMS Nanofabrication^[5] will decrease the number of processing steps necessary. Thus throughput, which has dropped significantly with the necessity of writing OPC features, will increase again, not only due to the multiple beam methodology itself but also due to its 3D patterning capability.

The figure shows the hard mask process flow: Conventional resist approach vs. ion multi-beam patterning
Another advantage is the direct patterning of the hardmask layer above the chrome on this high resolution mask. The resist processes used to date to structure the hardmask are limited by pattern collapse and a significant etch bias.
Running the previously described process with 10kV Ar+ at a dose of 12,45 mC/cm2, acceptable chrome features could be realized. Looking on shape and resolution, the profile angle in Cr is nearly perpendicular. The smallest feature resolved so far is 60nm for lines and 45nm for contacts.

Progress has also been made with respect to the processing techniques for COLORCHIP proprietary optical devices, planned to be fabricated with the CHARPAN Tool. The images show ICP RIE etched grooves in COLORCHIP substrates with process parameters as established for fused silica patterning (a) and with improved parameters (b) [COLORCHIP, FhG IISB]

^[2] van Delft, F. et al.: "3-dimensional Projection Mask-Less Patterning (PMLP) of microlenses and cones: modelling and monitoring of ion multi-beam kinetic sputtering in GaAs", Poster Presentation: MNE'07, Copenhagen, Denmark, 2007 Sep 23-26.
^[3] Butschke, J. et al.: "3D Template fabrication process for the Dual Damascene NIL approach" Photomask and Next-Generation Lithography Mask Technology XIV. Edited by Watanabe, Hidehiro. Proceedings of the SPIE, Volume 6607, pp. 66070U, (2007)
^[4] Kettle, J. et al.: "Fabrication of lenses for AlGaInP LEDs using Step and Flash Imprint lithography", 7th IEEE International Conference on Nanotechnology, Hong Kong, China, 2-5 Aug 2007
^[5] Kettle, J. et al.: "Fabrication of pattened 3- nickel components with electroforming and Step and Flash Imprint Lithography", MNE 2007, Copenhagen, Denmark, 23-26 Sep 2007
^[6] Kettle, J. et al.: "Development of functional material for Step and Flash Imprint Lithograpgy process", MNE 2007, Copenhagen, Denmark, 23-26 Sep 2007
^[7] Butschke, J. et al.: "Resist-less mask structuring using an ion multi-beam projection pattern generator", SPIE Photomask Technology (BACUS) Conference, Monterey, CA, USA, 17-21 Sept 2007