Deep X-Ray Lithography

Lithography & Patterning (Synchrotron-based lithography)

Deep X-Ray Lithography (DXRL) is a manufacturing process by which a material, which changes its dissolution rate in a liquid solvent (developer) under high energy irradiation, is exposed through an X-ray mask to synchrotron radiation. The pattern of the mask is transferred to the material. This is possible by the availability of synchrotron radiation characterized by high brilliance and extreme parallelism. Coupled with electrodeposition, casting, hot embossing, molding, or microelectroerosion (the so called LIGA process), it allows using a wide range of materials: plastics, metals and alloys, ceramics. It is a very flexible tool for fabricating microdevices.

The beamline performs an irradiation of samples with controlled X-ray doses, favouring material science studies and the fabrication of microdevices made of new materials like silica, titania, carbon bucky papers, new TR polymers…

Therefore, DXRL is a key technique to fill the gap between the nano/bio scale (current target of cutting edge studies) and the macroscale, allowing manipulation and analysis of nano-sized objects.

The possibility to fabricate micromolds or microelectrodes for the production of small batches of microdevices, makes LIGA process suitable for industrial applications.

The facility provides access to the Deep X-ray Lithography beamline, equipped with a DEX02 Jenoptik scanner which allows a fully automatic exposure procedure, a scanning speed ranging from 1-50 mm/s, the irradiation of 4 inches masks and resist substrates (water cooled), horizontal and vertical apertures, and an exposure area of 54x84 mm. A set of 5 filters allows a tailored hardening of the beam so obtain a better dose contrast especially for thick resists. The exposures can be performed at 90 mbar in helium or nitrogen atmosphere. Specific sample holders have been designed for powder irradiation and new sample holders can be designed and constructed for particular applications.

A chemical lab with a chemical and a laminar hood, spin and dip-coater, oven (CARBOLITE, which reaches a maximum temperature of 1100 ˚C), balances, stirrers is available.

In order to characterize the structures, the following tools are available:

1- Optical Microscope LEICA MZ125

2- UV-VIS spectrometer (Cary 60, Agilent Technologies) equipped with a standard cuvette holder and a Slide-Mounted External Specular Reflectance. Interchangeable masks for examining small samples or small areas of large samples are provided.

3- FT- IR spectrometer (Alpha-T, Bruker Optics) equipped with modules for the analysis of different types of samples.

provided at NFFA-Europe laboratories by:

TUG

Italy

provided at Large Scale Facilities by:

KIT

Germany

KIT

Germany

KIT DXRL

Applications

Deep X-ray lithography (DXRL) uses synchrotron radiation to pattern thick PMMA layers (thickness: several microns up to a few millimetres) in order to achieve high aspect ratio microstructures (aspect ratio up to 100). The structures are characterised by very steep sidewalls (slope angle better than 1 mrad) and sidewall roughness in the range of 20 to 30 nm. For optical applications usually microoptical benches with cylinder lenses, prisms and fixing structures for other optical components are fabricated. The structures are either used as prototypes, as lost form for metal replication or as moulds to fabricate mould inserts. Other application areas are several kinds of X-ray optical components like lenses and gratings. We are also involved in fabricating RF MEMS components, sensors and phantoms with high resolution test patterns.

TUG

Italy

DXRL at TUG

Applications

The DXRL facility offered by TUG dedicated to deep X-ray lithography, allows both the production of high aspect ratio three dimensional microstructures with quasi perfect side-wall verticality and optical quality roughness, and the radiation assisted synthesis and processing of novel functional materials in order to exploit their functionalization, and to be able to pattern them and position the desired properties in selected areas of microdevices. A laboratory placed near to the beamline allows the preparation and the post processing of the samples that will be irradiated.

Source Energy Range

At present, the energy range is focused on hard X-rays (1-20 keV with a Gaussian shape with a peak at 6keV). This allows a high penetration depth and the possibility to irradiate materials that cannot be modified with a different energy range. The scanner is equipped with a filter chamber; these filters allow to shift the spectrum towards the high energies in order to have a better dose contrast, especially for thick resists. The chamber just before the filter chamber hosts the beam stop; there is a set of 5 horizontal slits that can be manually inserted in the middle of the beam in order to shift the spectrum towards the lower energy. This improves the mask contrast.