AFM compatible microfabricated near-field microwave probes for scanning microscopy

Scanning local probe microscopy (SLPM) tools such as scanning tunneling microscope (STM), atomic force microscope (AFM), magnetic force microscope (MFM), scanning capacitance microscope (SCM), and near-field scanning optical microscope (NSOM), have become important tools in imaging of materials with near atomic resolution. These probes, however, either operate with low frequency signals (≤1 GHz) or operate in the optical regime.; In this thesis, the design and microfabrication of silicon co-axial scanning near-field microwave probes compatible with AFM imaging were reported. Scanning near-field microwave microscope (SNMM) imaging is suitable for nondestructive surface and subsurface characterization of materials over a wide frequency range between 0.1 GHz and 140 GHz. This novel SLPM tool can bridge the frequency gap that exists among other commercial SLPM probes as mentioned above.; The microfabricated SNMM probe consists of a silicon V-shaped cantilever beam, a co-axial tip, and aluminum co-planar waveguides. The V-shaped cantilever beams have spring constants in the range of 0.1 N/m–10 N/m, mechanical resonant frequencies in the range of 10 KHz–200 KHz, comparable with those of commercial AFM probes. The tip itself is oxidation-sharpened heavily doped silicon surrounded by an oxide layer that acts as insulator and covered with an aluminum co-axial shield layer. The co-axial tip structure enables the silicon tip to protrude through an aperture in the aluminum shield layer. The aperture confines the electromagnetic field in the exposed tip region to perform microwave measurement.; More than 300 SNMM probe chips were fabricated on a 4-inch SOI wafer in a batch process consisting of seven photolithography steps. Co-axial tip with height ∼10 μm, apex radius ∼50 Å, and aperture radii in the range between sub-micron and micron (500 nm—several microns) have been achieved.; Mechanical and electrical characterizations of the SNMM probes were discussed. The first simultaneous contact AFM and SNMM surface imaging were presented.