Density Measurements of Some Thin Copper Films

Abstract

Density measurements have been made on vacuum‐deposited copper films in the thickness ranges 50 to 150 A and 500 to 1000 A. To obtain the density, an analysis was made of the relation between the reflection coefficient and the glancing angle of incidence for 1.54 A x‐rays. For films in the range 500 to 100 A, this analysis was augmented by a chemical determination of the average mass per unit area. Although there is evidence of nonuniform density with depth in the film, especially for the very thin films, the average density of a film thicker than about 300 A was found within the limits of the experimental accuracy to be equal to the bulk density. This conclusion is in disagreement with some previously published work; the discrepancy appears to lie in differences between the x‐ray method of measuring film thickness and the conventional optical interference method.