NNIN Technical Resources
NNIN facilities house over 1100 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.
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, with the most advanced facilities at Cornell, Santa Barbara, and Stanford.
For patterns smaller than 0.5 um electron beam lithography is often the tool of choice. In e-beam lithography, a beam of electrons is scanned across the substrate under computer control to expose the resist NNIN sites have a range of e-beam lithography tools, from SEM based systems to full scale production tools. The most sophisticated e-beam tools are located at Cornell and Georgia Tech, with other advanced e-beam tools located at Penn State, Harvard, Texas, Minnesota, U. Washington, UCSB and Stanford. 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 facilities include support for SU8, polyimide, and PDMS processing at some sites.
Cornell, U. Washington, Penn State, and Georgia Tech support on site mask fabrication for ongoing projects. These considerably improve turnaround time for multistep, multi-iteration projects. Aperture based pattern generators, laser pattern generators, and e-beams are all used.
Deposition and Growth
NNIN sites support a broad range of deposition technologies for metals and insulators. Each site has an extensive set, and, when necessary, samples can be transferred from site to site. Filament evaporation, e-gun 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.
NNIN sites have major capability in Atomic Layer Deposition (ALD). ALD offers the ability to deposit layers one monolayer at a time, giving extremely uniform films over even high aspect ratio structures. The technique and equipment themselves are quite simple; the complexity is in the chemistry of the organic precursors. A wide variety of pure and compound films can be deposited.
Only a limited amount of Compound semiconductor growth, e.g. CVD and MBE, is supported within NNIN. In most cases, these specialized research tools are outside the NNIN facilities.
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 microfluidics 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, as is Vapor HF etching for release of oxide structures.
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).
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 measurements 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 capabilities 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) at a number of NNIN facilities, as well as at separately administered facilities on some campuses. In general, materials analysis instrumentation such as TEM is not within the primary scope of NNIN.
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 materials.
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.
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.