Quantitative thermal probing of devices at sub-100 nm resolution

Localized Joule heating in submicron features affects reliability of VLSI devices. This paper reports the use of batch-fabricated probes for scanning thermal microscopy (SThM) to characterize self-heating in miniaturized devices. The spatial resolution of the SThM technique is found to be about 70 nm. Existence of a liquid film bridging the tip and sample during scanning is verified and the thermal contact conductance of the liquid bridge is found to be significant. The thermal design of the probe was optimized in previous work and its thermal performance is now characterized. We apply the SThM technique for mapping temperature distribution on VLSI via structures under DC current heating. Excellent agreement was found between the results obtained from the SThM technique and that from a resistive thermometry method. This paper also demonstrates a novel phase imaging technique for locating subsurface hot spots. The subsurface imaging technique has the potential to be used for detecting defects in multilevel interconnects.