Design and batch fabrication of probes for sub-100 nm scanning thermal microscopy

A batch fabrication process has been developed for making cantilever probes for scanning thermal microscopy (SThM) with spatial resolution in the sub-100 nm range. A heat transfer model was developed to optimize the thermal design of the probes. Low thermal conductivity silicon dioxide and silicon nitride were chosen for fabricating the probe tips and cantilevers, respectively, in order to minimize heat loss from the sample to the probe and to improve temperature measurement accuracy and spatial resolution. An etch process was developed for making silicon dioxide tips with tip radius as small as 20 nm. A thin film thermocouple junction was fabricated at the tip end with a junction height that could be controlled in the range of 100-600 nm. These thermal probes have been used extensively for thermal imaging of micro- and nano-electronic devices with a spatial resolution of 50 nm. This paper presents measurement results of the steady state and dynamic temperature responses of the thermal probes and examines the wear characteristics of the probes.