Biaxial modulus and coefficient of thermal expansion of Cu0.57Ni0.42Mn0.01 (constantan) films

Abstract

Copper-nickel alloys are often used as precision wire resistors with 53 at% Cu, 46 at% Ni, and 1 at% Mn (constantan) [l]. They are also applied for resistive thin films, e.g. in surface mounted resistors [2, 31. For low sheet resistances, the films must be relatively thick (tf 2 1 pm). Especially for such thick films the mechanical stress is important for stability and reliability [4, 51. This correlation has been analysed in this work in order to evaluate the influence of the substrate and to find the relevant mechanical material parameters.Mechanical film stresses result in a curvature of the substrate. By measuring the curvature radii before and after deposition (ro, r), the stress c can be determined from Stoney's equation revised for biaxial stress [6],