SUBMICRON SI TRENCH PROFILING WITH AN ELECTRON-BEAM FABRICATED ATOMIC FORCE MICROSCOPE TIP

The atomic force microscope (AFM) has the potential for profiling on a nanometer scale. However, for the AFM to be useful as a reliable and accurate metrology tool, the atomic force sensor used (i.e., cantilever and sensor tip) should be highly reproducible in the fabrication process and the tip shape used should be known with high accuracy. Moreover, for profiling and critical dimension measurement of device trenches with submicron openings and trench depth of 1-mu-m or more, nanometer-scale tip shapes with high aspect ratio will be required. In order to meet the above requirement, a novel high-resolution direct electron-beam deposition process has been developed in which a sharp tip is grown onto an existing Si cantilever structure. In the example to be discussed, sharp tips have been grown directly on the integrated tip of a micromachined Si cantilever by decomposition of a dimethyl-gold organometallic complex. The direct e-beam deposition process provides a unique capability for the controllable fabrication of high aspect ratio, nanometer-scale tip structures. Typical dimensions of the AFM tips achieved are 0.1-mu-m in column diameter, 1-4-mu-m high, and 15 nm in tip radius. Recent feasibility experiments of using these e-beam tips in the laser force microscope have demonstrated for the first time that this nanoscale tip can be used for mapping 1-mu-m-deep Si trenches. Submicron trenches with openings as small as 0.36-mu-m have been successfully profiled. In this paper, various issues on tip fabrication, deep trench profiling and comparison of AFM and corresponding scanning electron microscopy measurements will be discussed.