Characterizing the Life-Cycle of Threshold Electrostatic Discharges Using Coupled Electrical and Optical Measurement

Electrostatic discharge (ESD) poses danger around electronics and sensitive materials. ESDs from tools or hands with limited stored charge are closer to threshold, so we are studying the energy transfer and plasma dynamics in these ESDs. We are making electrical and optical measurements to understand the nonlinear time dependent resistance along with the plasma and neutral density evolution to inform our ESD models.

We use our home-built ESD chamber to obtain time-dependent electron and neutral density profiles. We analyze two-color Mach-Zehnder interferograms with wavelet transforms and Abel inversion. The fast-framing cameras are currently triggered on the leading edge of a current viewing resistor signal; a UV triggering pulse will allow us to measure the earlier ESD phases.

Coupling our electrical and optical measurements allows us to determine how much of the resistance changes are attributed to the evolution of the channel density profiles. The fall and rise in ESD channel resistance following the initial breakdown occurs in distinct phases. In the 1-10us timeframe, we see a rise in resistance without a density change in the electrons, pointing to plasma cooling as the cause. The combination of these data sets informs our models of the spark evolution and low-temperature recombination.