Micro & Nano Fabrication
Instrumentation's Micro/Nano Fabrication Laboratory was organized to assist the
newly formed Accelerator Test Facility in the fabrication of microstructure
arrays used to study novel acceleration mechanisms with a laser linac. The
expertise gained in this area has since been used to manufacture specialized
micro or nanoscale structures for many investigators in both academia and
industry. Past collaborations with industry include the development of infrared
filter arrays for NASA, and efforts with Lockheed-Martin and Standard
Microsystems to develop multi-axis accelerometers and improved versions of ink
jet printer heads using high aspect ratio microfabrication. From 2004 to 2009,
a JEOL 6500F scanning electron microscope in the laboratory was equipped with
an electron beam lithography capability that allowed it to serve as a jump start facility for visiting researchers to design and fabricate nanostructures
while the Center for Functional Nanomaterials was being completed. John Warren
and Don Elliott, Instrumentation staff members, were involved the design,
equipment choice, and initial commissioning of the CFN clean room that now is
BNL's primary laboratory for both large and small nanofabrication research.
The Micro & Nanofabrication Laboratory is equipped with, or as access to in
other Instrumentation laboraotries, all major apparatus used in nano/
microfabrication design, processing, and characterization. Visiting
experimenters are encouraged to actively participate in the design process by
learning the fundamental fabrication processes such as anisotropic etching,
plasma etching, and high aspect ratio lithography and then designing masks for
the chosen method. Patterning steps take place in a Class-100 clean room
equipped with resist spinners, developing tanks, and etching stations. Major
equipment used for nanofabrication includes a Lesker Lab18 vacuum deposition
unit, a Karl Suss MJB-6 mask aligner, an Oxford Plasmalab 80Plus reactive ion
etching unit, and a Nikon optical microscope equipped with a custom-designed
quantitative metrology measurement capability. An adjoining Class-l000 room
contains oxidation furnaces for growing oxide layers on silicon wafers, and a
wet bench for anisotropic etching. The JEOL 6500F scanning electron microscope
is a multi-purpose tool that can be used for high resolution imaging, electron
beam lithography, and EDX electron beam micro X-ray analysis.
Current Research Efforts
IC Failure Analysis for RHIC's STAR PXL Detector
Griener (LBNL), Radeka, and Warren
On-going efforts have developed a method of etching integrated circuits using reactive ion etching in CHF3/Ar plasma. The method uses the aluminum conductors in the IC as a mask, and strips away exposed oxide and oxynitride layers to reveal the interior of the device. With a 3 um/hour etch rate, deeply buried features can be revealed by etching for several hours without damaging the microstructure. By correlating hot-spots seen by infrared imaging with scanning electron micrographs, the precise area of damage in the PXL sensors can be determined and used as a guide to minimize defective sensors in future sensor designs.
High Resolution Pinhole Mask for the LSST Optical Beam Simulator
Tyson (UC Davis), O'Connor, Elliott, and Warren
To characterize the optoelectronic performance of the LSST CCDs prior to final camera construction, the CCD array must be illuminated with a realistic astronomical scene. One such method is to fabricate a pinhole array mask consisting of thousands of artificial stars and use them to illuminate the CCD array on an optical bench. Such an array has been created with optical lithography by patterning a 0.4 um thick aluminum layer that is vacum sputtered on a fused silica wafer. A master mask is used to pattern photoresist that covers the aluminum layer, which is then etched to form the individual pinholes. Exacting requirements such high contrast and low reflectivity make the lithography difficult, but scanning electron microscopy has shown that 3 um diameter pinholes can be fabricated with a high degree of accuracy.
Improved Carbon Targets for the RHIC Polarimeter
Steski (CAD) and Warren
Experiments have shown that carbon targets fabricated by electron beam evaporation fail after only a few hours of being irradiated by the 200 GeV proton beam at RHIC. Since carbon target lifetime is a crucial parameter for the polarimetery experiment, efforts were made to understand the failure mechanism and develop more robust targets. It was proposed that target heating during beam exposure gave rise to carbon graphitization. Graphitization should make the targets more conductive and perhaps stronger to better withstand the tensile force from electrostatic interaction with the proton beam. Electron microscopy diffraction of irradiated targets has shown that graphitization does occur, and that it can be simulated by heating the target before placing it in the RHIC polarimeter. Efforts are now underway to determine the precise time-temperature annealing cycle required to optimize the materials properties of the target for optimum longevity when it is irradiated by the proton beam.
High Resolution SEM Imaging of Lysosyme Protein Crystals
Salazar-Kuri, Stojanoff (Photon Sciences) and Warren
The determination of protein crystal structure using low angle X-ray diffraction is an active research area at the NSLS II. Nucleation of the crystals is often difficult but it has been found that nanoscale pores etched in single crystal silicon serve as a perfect nucleation site. The SEM micrograph shows lysozyme protein crystals that have nucleated and grown in the silicon nanopores. The pores range in size from 1 nm to less than 100 nm. Some of the crystals inside the pores display the characteristic tetragonal crystal structure.
High Speed X-ray Quantitative Analysis Using A Silicon Drift Detector
Petrovic (Condensed Matter Physics) and Warren
The study of high Tc iron-based superconductors requires high quality impurity-free single crystals.? The stoichiometry of the crystals must be precise if superconductivity is to be observed, so an accurate and rapid determination of atomic composition of test crystals is essential.? The ZAF method of structure analysis using electron beam induced X-ray spectra is used for quantitative determination.? Accuracy is dependent on the total number of counts accumulated in the spectra, and a silicon drift detector attached to a JEOL 6500 F SEM, allowing 100K counting rates with minimal dead time, has proven ideal for this task.