Investigation on the thermal distribution of nMOSFETs under different operation modes by scanning thermal microscopy

A Wollaston resistive probe based scanning thermal microscope (SThM) is used to investigate the thermal distribution within the gate channel of an nMOSFET with width to length ratio (W/L) of 2.0 /spl mu/m/3.0 /spl mu/m. The dynamic mode of SThM is used to detect and characterize thermal wave propagation in an nMOSFET biased at different operation modes, i.e. linear, near saturation, far saturation, and near breakdown. An ultra compliant polyimide thermal probe is later employed and the resulting 2D thermal distribution is compared with the results obtained using the Wollaston resistive probe. Measurements using the two probes reveal that the highest thermal wave amplitude region in the gate is closest to the drain at pinch-off, and slowly spreads out and extends towards the source as the MOSFET approaches the near breakdown operation mode.