High Resolution Optical Surface Microtopography
Original Publication Date: 1981-May-01
Included in the Prior Art Database: 2005-Feb-11
The topography of a sample, such as a photolithographic mask, can be determined by a scanning laser beam in an autofocus arrangement, maintaining the laser focus on the sample by appropriate mechanical lens displacement. However, the probing of structures, such as mask openings, in the submicron range at a high depth-to-width ratio is difficult, as the focus Airy disk has dimensions comparable to those of objectives with great numerical apertures. Apart from this, the mechanical movement of the objective is cumbersome.