Laser micromachining is a flexible technique for precision patterning of surfaces in microelectronics, microelectromechanical
devices and integrated optical devices. Typical applications include drilling of holes, cutting of conducting
lines or shaping of micro component surfaces. The resolution, edge finish and residual damage to the surrounding and
underlying structures depend on a variety of parameters including laser energy, intensity, pulse width and wavelength.
Femtosecond pulses are of particular interest because the limited time of interaction limits the lateral expansion of the plasma
and the inward propagation of the heat front. Thus, very small spot size can be achieved and minimal heating and damage of
underlying layers can be obtained. An additional advantage of femtosecond pulses is that multiphoton absorption leads to
efficient coupling of energy to many materials independent of the linear reflectivity of the surface. Thus metals and
transmitting dielectrics, which are difficult to micromachine, may be machined with such pulses. The coupling is improved
further by employing ultraviolet wavelength laser pulses where the linear absorption typically is much higher than for visible
and infrared laser pulses. To explore these advantages, we have initiated a study of the interaction of 250nm femtosecond
laser pulses with metals. The laser pulses are obtained by generating the third harmonic from a femtosecond Ti:sapphire laser
operating at 750nm. The pulses are focused to various intensities in the range of 1010Wcm2 to 1015 Wcm2 using reflective
and refractive microscope objectives and ablation thresholds and ablation rates have been determined for a few metals. In
addition the ability to control feature size and produce submicron holes and lines have been investigated. The results are
presented and compared to results obtained using infrared and visible femtosecond laser pulses.