NNIN Technical Resources

NNIN facilities house over 700 major tools supporting thousands of processes, all openly available to users. These cover the full range of nanotechnology including both top down and bottom up approaches . A complete searchable tool listing is available elsewhere on this site.   NNIN laboratory facilities fall into the following general broad categories.  In all cases, NNIN offers not only access to tolls but project and process support, through regular NNIN staff as well as our Technical Liaisons. The links in the text below open a new window with a predefined search of the NNIN tool database.
Lithography Lithography is the process of patterning in a transfer layer. NNIN has extensive photolithography resources for patterning to 0.5 um.  These include a wide assortment of contact aligners (front and backside) as well as more sophisticated projection lithography tools, i.e. steppers.  All sites have extensive photolithography capability.  For specialized applications, state-of-the-art  deep UV (193 nm) projection lithography is offered at NCSU.    For patterns smaller than 0.5 um electron beam lithography is often the tool of choice. In ebeam lithography, a beam of electrons is scanned across the substrate under computer control to expose the “resist”.  NNIN sites have a range of ebeam lithography tools, from SEM based systems to full scale production tools.  The most sophisticated ebeam tools are located at Cornell and Georgia Tech, with other advanced ebeam tools located at Penn State, Harvard, Texas, and Stanford. Limited ebeam capability is available at Washington and UCSB. Contact NNIN for guidance as to the most appropriate site for any project keeping in mind that it may be the auxiliary processing capabilities that are the determining factor.      NNIN also has a variety of microtransfer patterning technologies, including imprint lithography, embossing, and microcontact printing. This includes a Molecular Imprints Imprio Step and Flash SFIL tool at U.Texas at Austin.  Microcontact printing of various organic and biological materials is available at several sites including Penn State, Harvard, and Washington. A complete range of resist processing support technologies is available including coating, development, curing, vapor priming, and image reversal. Specialized facilitities include support for SU8, polyimde, and PDMS processing at some sites. Cornell, Stanford, Penn State, and Georgia Tech support on site mask fabrication for ongoing projects. These considerably improves turn around time for multistep, multi-iteration projects. Aperature based pattern generators ,  laser pattern generators, and ebeams are all used.
Deposition and Growth NNIN sties support a broad range of deposition technologies for metals and insulators.  Plasma deposition.  Each site has an extensive set, and, when necessary, samples can be transferred from site to site.  Filament evaporation, egun evaporation and sputtering are widely available. Plasma assisted Chemical Vapor Deposition (PECVD) can be used to grow films by chemical vapor deposition at lower temperatures.  These are generally silicon, silicon dioxide and silicon nitride for various passivation, dielectric, and interlayer spacer applications.  (Non-plasma) CVD is generally done in furnace tubes for the growth of a range of silicon compounds on clean wafers. This includes a low stress silicon nitride film that is popular for MEMS and membrane applications. Thermally grown silicon dioxide is a common building block for nanostructures and is widely available in the network. Compound semiconductor growth including GaAs, GaN, and SiCs are available by CVD and MBE,  particularly via the Howard and New Mexico sites.
Etching Critical to most any nanotechnology process sequence is the ability to selectively remove materials with high selectivity and resolution.   A full range of dry etching technologies are available, widely spread across the network.  Reactive ion etching and other forms of dry etching are the most common.  Over 50 dry etch tools are, in almost every possible configuration.  Since different gases are required for different materials, and there are many incompatibilities, many systems are  required to provide full coverage. Few individual laboratories can provide the type of coverage that is possible in a high use user facility.  Etching of silicon, silicon nitride, and silicon dioxide are most common and are available at most network facilities.. The network also offers extensive facilities for metals and compound semiconductors.   High density plasma tools ( ICP, TCP, ECR) are available for more demanding etch applications. Deep RIE of silicon ( >100 um with aspect ratio >50:1) via the Bosch Process is available at many sites. Deep RIE is critical to many MEMS and microfludics projects.   Ion beam etching  and  ashing/stripping processes are also available.  Xenon Difluoride Vapor Etch is available for an anisotropic silicon etch for release of suspended structures for MEMS applications.
Wet Chemical Processing A full spectrum of wet chemical etching and deposition processes are available. These include  RCA type wafer cleans, crystallographic etches using KOH, isotropic etches, and electroplating processes.   Critical Point Drying is available at several sites and  is sometimes used to dry wafers after wet processes to minimize stiction problems.
Other Traditional Thin Film and Device Processing Other supported processes include ion implantation, Chemical Mechanical Polishing (CMP), and Rapid Thermal Annealing (RTA). Back end processes include wire bonding, scribing, and dicing (sawing).
Electrical Characterization In addition to tools for materials characterization, a number of the NNIN sites have tools for characterizing the electrical properties of materials or structures.  These tools may be found by searching the "Electrical Characterization" area of the NNIN tool database.  Several of the NNIN sites have tools for characterizing the sheet resistance of conductive deposited films.  There are also facilities for making more detailed I-V (current-voltage) measurements of devices and structures including low-current measurments of less than 1 picoamp.  AC impedance measurement instruments are also available for measuring the capacitance or inductance of a range of structures.  Finally, several of the NNIN sites also offer probe station capabiities to allow small, unpackaged structures and devices to be electrically characterized.
Structure and Materials Characterization Scanning Electron Microscopy is critical to any nanotechnology project and extensive state of the art resources are available at every site.  A variety of optical microscopy resources are also available.  Stylus and Optical Profilometers are widely available for measuring feature heights. Scanned probe instruments, primarily AFMs, are also widely available on the network for surface and structure characterization at the nm scale. These instruments can be used not only to characterize surface topography, but also to map on a nanoscale surface chemistry, storage/loss modulus, hardness, interfacial energy, crystallinity, polarization, magnetization, surface charge, and local work function.  Nanoindentation is available to characterize the mechanical properties of materials on a nano scale.  Scanning and conventional transmission electron microscopy (STEM and TEM) is available via the characterization facilities at Cornell, Stanford, Minnesota, and New Mexico. TEM is generally a labor intensive and sample preparation intensive exercise but knowledgeable staff area available at these sites to assist with both hands on and remote characterization. Energy dispersive spectroscopy  can be used on STEM systems to map chemical composition on a sub nm scale. Many types of x-ray diffraction systems are available to determine structural properties. Rutherford Backscattering, X-ray photoemission spectroscopy and Auger electron spectroscopy are available for chemical analysis. For thin film characterization, a variety of tools are available including electrical  ( e.g. resistivity)  , mechanical (e.g. stress)  , and optical ( elliposmetry, spectroscopic ellipsometry, reflectometry) techniques
Biological and Chemical Processing, Synthesis, and Molecular Assembly The visions of nanotechnology crucially depend on the ability to build and maneuver structures at the scale of 10-100 nm.  Traditionally, engineers fabricate nanometer-sized objects through the “top-down” approach by carving them out of lithography from a large substrate.  Yet the capital requirement makes this advance less desirable towards large-scale manufacturing.  Alternatively, the “bottom-up” approach, which relies on the assembly of nanoscale objectives from molecular-scale precursors through chemical processes, may hasten development of future nanotechnology applications by providing a cost-effective route to copious quantities of uniform nanostructures, such as quantum dots, nanotubes, and nanowires of varies matierals. Soft lithography – a collection of novel patterning techniques based on printing, molding and embossing using a transparent elastomeric stamp – represents a new conceptual approach in fabrication and manufacturing of new types of structures and devices that exceeds the scope defined by classic photolithography in the practice of microelectronics industry. As an illustration, Microcontact Printing – the forerunner of Soft Lithography – exploits an elastomeric stamp with patterned relief structures for printing “ink” on a flat or cylindrical substrate with feature size as small as 200 nm.  The “ink” essentially covers all kinds of compounds, materials, and structures.  Typical examples include chemical species that can form self-assembled monolayers (SAMs), conventional organic polymers; dendrimers; proteins and other biological macromolecules; polyelectrolyte multilayered thin films; lipid bilayers; metal ions or complexes; catalysts; colloidal particles; and micro-/nanostructures of metals or semiconductors.  As an alternative, Dip Pen Lithography (DPL) provides an alternative approach to “print” materials on a substrate using an Atomic Force Microscope cantilever instead of an elastomeric stamp.  DPL enables patterned structures as small as 20 nm.  Nanoimprint Lithography based on embossing and molding allows fabricating patterns of structures in polymer with resolution as small as 20 nm.
Nanoparticles and Nanomaterials Nanoparticles are frequently used as building blocks for larger structures while in other instances they may compromise the performance of a system.  Nanoparticles can be used to create nanomaterials and nanostructures through a variety of sintering or fusing processes.  Characteristics of these particles such as size, shape, composition and crystalline structure have a major effect on the properties of the final nanomaterial.  Particles can be airborne, suspended in liquids or deposited on solid surfaces.  Characteristics of these particles can help identify their source and suggest control techniques.  NNIN has the capability of measuring a wide variety of particle characteristics in different media.  The measurements provided at the Minnesota node include: Particle size distributions from 3 nm to over 10 m with high resolution in real time; Aerosolizing a broad range of materials in different phases; Characterization of particle shape; Selecting mono-sized particles from a broad distribution for further characterization, conditioning and/or deposition or detection; and Providing real-time size and composition characterization of individual sub-micron particles. The combined expertise of our staff covers a broad range of topics in aerosols including: Measurement of airborne contaminant levels on location; Characterization of powders by size; Measurement of non-volatile residue in solutions; Deposition of size-classified particles on wafers, microscopy grids or other surfaces; and Consultation on filtration or cleanroom issues.
Process Integration Of course none of these instruments stands on its own. Many are needed to accomplish most projects. The integration of these processes is thus important part of the offerings of each NNIN site.