An energy beam, such as the coherent output of a laser, is applied to a thin film in a controlled manner, preferably as a pluse. The length of the pulse is regulated to form a tapered aperture in the film. The duration, energy and wavelength of the beam pulse with respect to the thickness, thermal properties and optical properties of the film are such that impingement of the beam pulse on a first surface of the film results in controlled removal of a small amount of the film. The pulse is terminated before the temperature gradient between the first film surface and a second film surface (the film's thickness being bounded by the surfaces) is zero. Plural pulses may be serially applied to form the tapered aperture to a desired depth.
Typically, the thin films range in thickness from several hundred angstroms (.about.400A.) to about 10,000A. and may be dielectrics (SiO.sub.2, Si.sub.3 N.sub.4, Ta.sub.2 O.sub.5), metals (Au, Al, Ta, etc.) and silicon.
Relative motion of the pulsed beam and the film produces a pattern of tapered holes or, alternatively, a tapered kerf or moat.