A mask for manufacturing microcircuits is comprised of a substratum and a layer of matter, such as, for example gold, adjacent the substratum. An aperture is located in the layer of matter. The aperture in the layer of matter exhibits a cross-section resembling an inverted isosceles trapezoid. The method for manufacture of the mask comprises the steps of appositioning a patterned layer of photoresist to a layer of gold which is adjacent the substratum. The structure comprising the photoresist, the gold layer and the substratum is exposed to a beam of ions having a preselected kinetic energy such that the ions remove gold exposed by apertures in the photoresist layer. The kinetic energy of the ions is selected such that an aperture is eroded in the layer of gold, the aperture exhibiting an inverted isosceles trapezoidal cross-section.