Nanofabrication Facility
Our in-house nanofabrication facility houses extensive capabilities from scanning e-beam writers to various materials processing systems, allowing fabrication of complex nanostructures. In addition to fabrication, growth and processing, the structures are characterized for both electrical continuity and structural integrity by a number of techniques. Integration of this facility with our measurement lab is important as it allows an efficient and effective approach to the projects which require everything from fabrication, processing, characterization to measurement in extreme environments.
The in-house nanofabrication facility spans an area of over 1500 sqft which has been remodeled to operate as a class-10,000 clean room. An isolated cleanroom inside the facility allows an even cleaner environment at the level of class 1000. A laminar-flow hood inside this clean room provides a volume of workspace with an environment down to class 100. A number of fume hoods and laminar-flow hoods provide localized clean space.
The types of nanostructures manufactured in our lab vary in their fabrication techniques, materials, and level of complexity. Nanoelectronics structures typically involve metallic nanowires or quantum dots on silicon substrates. Nanomechanical structures are suspended devices with three-dimensional relief with simple designs of beams and cantilevers to antennas and complex torsion oscillators. Some of these structures have many layers of materials to have provisions for access to local electrical, magnetic and/or mechanical signals. Bio-functionalized structures are nanomechanical structures with additional processes for coating biomaterials with nanometer scale resolution. Tip-enhanced microscopy requires metallic pillars or tips with a diamater of roughly 10 nm and a height of up to 1 micron. In addition to these structures, we are also developing techniques for high-density nanostructures by combining hard and soft lithography.
Electron-Beam Writer for Nanolithography
A JEOL JSM-6400 scanning electron microscope with a Deben beam blanker is currently used for imaging and beam writing. The resolution of the electron beam at 40 kV is determined to be 3 nm, leading to a lateral resolution of 15 nm for imaging and writing. Fitted with Nabity software for lithography, the e-beam writer allows lithography and imaging on a variety of insulating and conducting substrates.
Substrate Prepapration: Spin-Coating, Surface Profiling, and Optical Lithography
The clean-room facility includes spin-coater, surface profilometer, high-resolution optical microscopes, ozone stripper, plasma cleaner and mask aligner for substrate preparation for lithography. For insulating structures, a thin conducting layer is deposited for high resolution e-beam lithography on substrate surface.
Material Deposition: Evaporators and Sputtering Systems
The facility includes three thermal evaporators for dedicated nonmagnetic deposition, and multiple-material deposition. In addition, there is a sputtering system for deposition of materials such as niobium, oxides and nitrites. The supporting optical processing facility (OPF) in Photonics Center also houses a number of thermal evaporators, e-gun evaporators, and sputtering chambers.
Structure Characterization
Characterization includes check for structural integrity, surface topography and electrical continuity of electrical lines. Nanofabricated structures are characterized with the JEOL scanning electron microscope (SEM), a digital instruments atomic force microscope (AFM), and a probe station. Electrical characterization is also performed at low temperatures in 4-Kelvin dippers.
Wirebonding, 4-Point Probe Station, Pulse Probe
The facility includes a wedge bonder and a thermal ball bonder for making electrical contacts between the nanoscale structures and contact pads. In some cases, a four-point probe station with precision current sources and LCR meter allows room temperature measurement without bonding. An Agilent oscilloscope with capabilities for time-domain reflection characterization is used to check for electrical continuity with picosecond pulses.
Additional Fabrication Facilities
The central support facility for fabrication is the optical processing facility (OPF), which houses a number of optical mask aligners, reactive ion etch system, e-gun evaporators, thermal evaporators, sputtering chamber, plasma cleaners, probe station, and other materials processing and characterization systems.