A rapid and accurate method for measuring the thickness of diffused layers in silicon and germanium

Abstract

Surface-layer thicknesses can be measured very practically by making use of the brittleness of silicon and germanium, thus eliminating cumbersome, precise grinding and polishing procedures. The germanium or silicon slice is broken in a special manner producing a rather flat cleavage surface, in which any disturbing fracture line is more or less perpendicular to the very sharp, long edges. In this surface the exposed p-n junctions are marked as very thin lines by one of the well-known methods (electrolytical, chemical). The distances between these lines or to the edge of the cleavage surface are measured under a high-power metallographic microscope with an eyepiece micrometer. Magnification factors mostly used are 400 or 600 times. Very thin layers of about 1 μ are still measurable. The method is used for diffused layers as well as for alloyed contacts or combinations as in the case of alloy diffusion.