I do not know what kind of evaporation method you have, but in some you can control. Check, for example: Critical Reviews in Solid State and Materials Sciences, 17:6, 547-596; Surface and Coatings Technology. 66, 1994 310-312; Thin Solid Films, 171 (1989) 5-31. About the units, it depends on the method you use I guess. Interferometry is usually performed on optical coatings and is possible to obtain the stress in Pascal units by measuring the radius of curvature: Optics Express, Vol. 20, Issue 15, pp. 16596-16610 (2012).
First you have to calculate strain of the films using well known W H Method, (from the slope of : \beta cos\theta as a function of 4 sin \theta). After then using relation stress = strain \times Young modulus of the sample, you can calculate stress of the film.Details are given in the article: http://www.sciencedirect.com/science/article/pii/S0168900213014824