Metal can be locally removed by causing a spark between a sharp tip and a conducting surface. This can be useful in the failure analysis of integrated circuits and in the repair of photolithography masks. These tasks are usually performed using focussed ion beam (FIB). However, a FIB is an expensive piece of equipment and in many cases using microspark erosion can be just as effective.
In the image shown below, a spark was generated by puting the tip in contact with the metal film and allowing 1 mA of current to pass through the contact. The tip was then retracted while the current was flowing. When electrical contact was broken, the inductance of the circuit caused a spark which evaporated metal in the region around the point of contact.
Another application of microspark erosion is the production of nanoparticles. The manipulators were programmed to make contact reaptedly between a tungsten tip and a platinum wire in air. By causing many sparks, small Pt particles were deposited on the substrate.
Electrostatic discharge (ESD)
Electrostatic discharge is the sudden flow of electricity due to dielectric breakdown. Below are two images of a chip that was damaged by ESD. The metal was melted near the bond pads.
- The process of removing metal by causing sparks is similar to an industrially applied method called Electric discharge machining.
- P. C. Tan and S. H. Yeo, Modelling of overlapping craters in micro-electrical discharge machining, J. Phys. D: Appl. Phys. 41 205302 (2008). Online: stacks.iop.org/JPhysD/41/205302
- S. Schwyn, E. Garwin and A. Schmidt-Ott, Aerosol generation by spark discharge, Journal of Aerosol Science
19, pp. 639-642 (1988). Online: doi: 10.1016/0021-8502(88)90215-7