NIST working on single-nanowire positioning system for testing properties

May 4, 2007 – Researchers at the National Institute of Standards and Technology (NIST) say they have created a method for manipulating and positioning individual nanowires on semiconductor wafers, enabling fabrication of test structures using only optical microscopy and conventional photolithographic processing.

Today’s smallest-diameter nanowires are assembled atom-by-atom in a “bottom-up” bulk growth process, e.g. through CVD, which creates “haystacks” of nanowires of varying lengths and diameters, NIST explains in a statement. Typically, that means “throw[ing] a whole bunch of these down on the test surface, hunt around with a microscope until you find a good-looking wire in about the right place, and use lithography to attach electrical contacts to it,” said NIST electronics engineer Curt Richter, in a statement.

The new process from NIST uses a modified probe station with high-resolution optical microscope and a system that positions work surfaces under a pair of customized titanium probes, each with <100-dia. tips (see figure, above). Silicon nanowires suspended in a drop of water are deposited on a staging wafer patterned with tiny posts; once dried the nanowires are left sitting on top of these posts, and can be picked up by the probe tips using static electricity. The test structure wafer is positioned under the probes, and the wafer and/or probe tips are moved until the nanowire can be placed on the desired position. (The figure, below, shows a nanowire placed into an etched trench.)

While admittedly “not at all suited to mass production,” the process does have potential application in creating elaborate structures to test nanowires’ properties. NIST has already built a multiple electrical-contact test structure to measure nanowire resistance independent of contact resistance, as well as an electromechanical switch to measure the nanowires’ flexibility. Improving the probe tips’ sharpness and utilizing higher-resolution microscopes should improve the testers’ sensitivity beyond current capabilities of >60nm-dia. wires.

(a) Schematic of NIST single nanowire manipulation system. (Source: NIST)
(b) Scanning electron microscope image shows a single silicon nanowire positioned in an etched trench using NIST’s nanowire manipulation technique. The trench helps keep the nanowire in position during the fabrication of the rest of the test structure, which measures metal/nanowire contact resistance. [Scale bar = 20 microns] (Source: NIST)


Easily post a comment below using your Linkedin, Twitter, Google or Facebook account. Comments won't automatically be posted to your social media accounts unless you select to share.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>


SEMI-GAS Xturion Blixer enables on-site blending of forming gas mixtures
10/03/2017The Blixer provides a cost-effective alternative to purchasing expensive pre-mixed gas cylinders by enabling operators to blend ...
Automated thickness measurement system speeds production
09/20/2017ACU-THIK is an automated thickness measurement tool incorporating dual contact probes for high accuracy inspection of semiconductor wafers....
3D-Micromac launches the second generation of its high-performance microcell OTF laser systems
04/17/2017The high-performance production solution for Laser Contact Opening (LCO) of PERC solar cells achieves a th...