Lithography / Nano Imprint

The fabrication of precise 2D Au nanoparticle arrays over a large area is presented. The technique was based on pre-patterning of the substrate before the deposition of a thin Au film, and the creation of periodic particle arrays by subsequent dewetting induced by annealing. Two types of pre-patterned substrates were used: The first comprised an array of pyramidal pits and the second an array of circular holes.

A new illumination system for mask aligner lithography is presented. The illumination system uses two subsequent microlens-based Köhler integrators. The second Köhler integrator is located in the Fourierplane of the first. The new illumination system uncouples the illuminationlight from the light source and provides excellent uniformity of the light irradiance and the angular spectrum. Spatial filtering allows to freely shape the angular spectrum to minimize diffraction effects in contact andproximity lithography.

Mask defectivity is an acknowledged road block for the introduction of EUV lithography (EUVL) for manufacturing. There are significant challenges to extend the conventional methods of cleaning developed for standard 193nm opticalphotomask to meet the specific requirements for EUV mask structure and materials. In this work, the use of UV activated media for EUV mask surface cleaning is evaluated and the effects on Ru capping layer integrity are comparedagainst conventional cleaning methods. Ru layer surface is analyzed using roughness measurements (AFM) and reflectivity changes (EUV-R and optical).

In this paper SUSS MicroTec demonstrates the use of an alternative acid-free resist strip and cleaning process, which not only overcomes the named drawbacks of conventional ozone water use, but reduces resist strip time by 50% to 75%. The surface materials investigated during this study are; chrome absorber layers on binary masks, MoSi based shifters, chrome hard mask layers on EPSM, and ruthenium capping layers on EUV masks. Surface material integrity and CDstability results using this new, acid-free approach are presented in the following pages.

Preservation of mask cleanliness is essential to avoid risk of repeated printing of defects. The development of mask cleaning processes capable of removing particles adhered to the mask surface without damaging the mask is critical to meet high volume manufacturing requirements. In this paper we have presented various methods of residual (crosslinked) resist removal and final imprint mask cleaning demonstrated on the SUSS MicroTec MaskTrack automated mask cleaning system. Conventional and non-conventional (acid free) methods of particle removal have been compared and the effect of mask cleaning on pattern damage and CD integrity is also studied.

The ASonic® nozzle developed by SUSS MicroTec combines the very favorable dark loss, defect and global CD-linewidth control benefits of a fast and uniform low impact initial develop dispense (surface wetting), with an enhanced developer agitation through acoustic streaming, which provides improved local CD-control independent of pattern size and loading.

The principle functionality of the ASonic® nozzle is described. Developing loading effect is examined with various conditions and CD linearity, proximity and CD uniformity are also verified.

Nowadays, the development of inte-grated circuit (IC) industry and scien-tific researches rely more and more on the nanofabrication technologies. The resolution limits of optical lithog-raphy are very real even with a number of “optical tricks” at work. E-beam lithography (EBL) provides excellent resolution down to several nanometers. However, the throughput of EBL is too low for mass production due to its scanning exposure principle. Nano imprint lithography (NIL) has been included on the ITRS lithography roadmap for 32 nm, 22 nm and 16 nm nodes. This parallel patterning technique shows great potentials in fabrication of nanostructures with high resolution at low costs.

We show that a wide range of different micro-optical structures can be optimized by controlling the light diffraction in proximity lithography. Parameter settings were found for submicron binary pattern up to continuous profile structures with extensions up to several tens of microns. An additional interesting application of this approach is the combination of binary and continuous profiles in single elements, e.g. micro lenses with diffractive correction or AR structures. Experimental results achieved for blazed gratings with a period of 2 microns are presented