SBIR Phase II: Batch Wafer-Scale Fabrication of Improved Probe Tips for Scanned Probe Microscopy

This Small Business Innovation Research (SBIR) Phase II project will perfect a proprietary batch-scale processing technique for fabricating ultrahard and ultrasharp atomic force microscopy (AFM) tips. The new process involves two steps. First, chemical vapor deposition (CVD) is used to coat the tips with a chemically inert, highly conductive, and extremely hard material. Second, a patented process that we have developed, field directed sputter sharpening (FDSS), sharpens the probe tip to atomic dimensions (1- 4 nm radius of curvature at the tip apex). Hard, sharp tips are of considerable scientific and market interest because tip geometry and mechanical properties significantly impact the results of AFM measurements. The current project will carry out research to perfect a batch wafer-scale process able to manufacture hundreds of tips at once. In order to bring the technique to market, the following research and development tasks will be carried out: (a) optimization of process conditions to reproducibly sharpen arrays of AFM probes fabricated on 4-inch wafers, (b) investigation of the ability to coat and sharpen AFM probes with a variety of hard film materials, and (c) assessment of the performance of batch-fabricated probe tips for market-driven probe microscopy applications. The broader/commercial impact of the project arises from the development of robust, reproducible, and durable tips that are more resistant to wear (due to the high hardness) and have favorable characteristics for AFM imaging (small radius of curvature, controlled aspect ratio, and electrically conductive). The project will benefit the academic and industrial communities who use scanning probe microscopy imaging. Although AFM and related probe microscopies have many advantages over electron microscopy (e.g., they can be used under ambient conditions and they can be easily interfaced with optical spectroscopy), one significant drawback is that the probe tips have limited lifetimes owing to wear during use. The development and commercial introduction of probe tips that are ultrasharp, very hard, conductive, and relatively inexpensive will significantly enhance the capabilities of AFM and related techniques such as scanning capacitance microscopy (SCM), a technique of great interest to the microelectronics industry because it is useful for the on-board testing of integrated circuits for delay faults. The research will also be of benefit to those who image insulating surfaces such as polymers and other soft materials where static charge build-up limits efficacy, and to those developing multi-tip probe arrays for lithographic and nanomanufacturing applications.