Fabrication and application of a full wafer size micro/nanostencil for multiple length-scale surface patterning

A tool and method for flexible and rapid surface patterning technique beyond lithography based on high-resolution shadow mask method, or nanostencil, is presented. This new type of miniaturized shadow mask is fabricated by a combination of MEMS processes and focused ion beam (FIB) milling. Thereby apertures in a 100-500 nm thick low-stress silicon nitride membrane in the size range from < 100 nm to > 100 mum were made. The stencil device is mechanically fixed on the surface and used as miniature shadow mask during deposition of metal layers. Using this method, aluminum micro- and nanostructures as small as 100 nm in width were patterned. The deposited micro- and nano-scale structures were used as etch mask and transferred into a sub-layer (in our case silicon nitride) by dry plasma etching. High-resolution shadow masking can be used to create micro/nanoscale patterns on arbitrary substrates including mechanically fragile or chemically active surfaces. (C) 2003 Elsevier Science B.V. All rights reserved.

Nanostencil Lithography - Quick & Clean: Towards a reliable scalable nanopatterning method

Jürgen Brugger, Nao Takano, Marc Antonius Friedrich van den Boogaart, Oscar Vazquez Mena

Stencil lithography is a surface patterning technique that relies on the local deposition of material through miniaturized shadow mask membranes. This method has been used since many years in various implementations for the formation of patterns, mainly structured thin metal films, in situations when lithography equipment is not available or when the surfaces don’t allow the harsh process steps typically involved in photolithography such as spin coating of photoresist, high temperature baking, development, wet or dry etching and resist stripping. Stencil lithography is down-sizable into the sub-100-nm scale which makes it very interesting as method for (in-vacuum) rapid-prototyping of nanostructures without the risk of contamination, and for laboratories without access to high-end nanolithography equipment. The major challenges in stencil lithography are following: i) the fabrication of large area nanostencils requires one high-resolution lithography step and sophisticated MEMS processes, ii) the mechanical properties of thin membranes (typically ~ 100 nm thick) requires careful handling, iii) the effect of deposited material on stencil leads to aperture clogging and membrane bending which limits the resolution capabilities, iv) the precise positioning of nanostencils to prefabricated surfaces structures for aligned multiple layer patterning, v) and eventually the recycling of used stencils. Despite these difficulties, stencils are extremely useful tools for flexible and reliable patterning of surface structures across multiple length-scales from mm to sub-100 nm. In collaboration with our project partners we have recently progressed in several of the above mentioned challenges: the fabrication of stencils is now based on a set of advanced silicon micromachining steps including DUV exposure for >200 nm apertures and a combination of DRIE and wet etching. Focused beams are used to fabricate stencils with sub-100 nm apertures. In particular the mechanical stability of the ultra-thin low-stress silicon nitride membranes could be considerably improved by topographic reinforcement rims. As a result, the membranes deform less under the stress of deposited film and consequently the surface patterns are better defined. We have studied patterning by stencil lithography of metals (e.g. Al, Au, Bi, Cr, Ti, Cu) on various surfaces (e.g. Si, SiO2, SU-8, PDMS, PMMA, freestanding SiN cantilevers, and curved surfaces. Pulsed laser deposition of metal on self-assembled monolayers (SAMs) has resulted in novel micro/nanopattern for molecular electronic devices. Parallel fabrication of thousands of sub-micrometer resonating beams that are integrated with CMOS circuitry have been realized by stencil lithography and sacrificial etching. The talk will present the current state-of-the-art of the nanostencil lithography , will highlight the strength of the method but will also discuss the current limits and challenges ahead to make it a truly reliable nanofabrication method.

2006

Stenci Lithography: Status and Prospectives

Jürgen Brugger, Nao Takano, Marc Antonius Friedrich van den Boogaart, Oscar Vazquez Mena

2006

NANOSTENCIL-BASED LITHOGRAPHY FOR SILICON NANOWIRES FABRICATION

Jürgen Brugger, Christian Santschi, Marc Antonius Friedrich van den Boogaart

We propose a novel lithography method based on local deposition through miniature shadow-masks (nanostencils) for the fabrication of silicon based nanoelectronics devices. We demonstrate the fabrication of nanowires with a CMOS compatible stencil based lithography process. The silicon nitride (SiN) stencil is fabricated using optical lithography combined with procedures. Then 45 nm wide structures are made using focused ion beam (FIB) milling. The process results in a 110 nm wide silicon nanowire.

2005

Nanostencil Lithography - Quick & Clean: Towards a reliable scalable nanopatterning method

Jürgen Brugger, Nao Takano, Marc Antonius Friedrich van den Boogaart, Oscar Vazquez Mena

2006