Analytical Instrumentation, Methods & Materials
Batch Fabrication of High Aspect Ratio Micromechanical Probe Tips
Inventors: Daniel van der Weide, Yaqiang Wang
The Wisconsin Alumni Research Foundation (WARF) is seeking commercial partners interested in developing a multi-step batch process for manufacturing silicon probe tips with superior tip height and high aspect ratio for atomic force microscopy.
The atomic force microscope (AFM), one of many types of scanned-proximity probe microscopes, images a sample by lightly touching it with a probe tip attached to the end of an extremely flexible leaf spring cantilever. Current methods of manufacturing high aspect ratio probe tips are complex and expensive, and result in tips shorter than 30 microns.
UW-Madison researchers have developed a multi-step batch process for manufacturing silicon probe tips with superior tip height and high aspect ratio for atomic force microscopy. First, an etchant protective island is formed on the surface of a silicon substrate with the substrate exposed around the island. The substrate is etched isotropically around the island by reactive ion etching (RIE) to partially undercut the substrate beneath the island. Next, the silicon surrounding the island is anisotropically etched using deep reactive ion etching (DRIE) to define a tip shaft of the desired height. The sidewall of the shaft is smoothed by a wet chemical clean and RIE to remove characteristic scalloping features from the DRIE step. At the same time, the RIE creates the desired shaft diameter. Finally, the protective island is removed from the tip and the top of the tip shaft is sharpened to an apex.
- Production of tips for AFM
- Particularly useful for industrial semiconductor quality testing applications
- Can be used, with some additional steps, to produce a coaxial tip with high aspect ratio for scanning near-field microwave microscopy (SNMM)
- Allows for mass production of up to 400 tips on a single wafer
- Less expensive than current manufacturing methods
- Can produce tips taller than 30 microns (potentially greater than 100 microns) while maintaining the vertical sidewall needed for both AFM and SNMM applications
- Produces tips with an aspect ratio of height to width of seven or greater
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