AbstractThe residual stress in spin coated films and the effect of heat treatments on this stress were determined by the Fizeau interference method. Three types of spin coated polyimide (PI) films have been studied. Two of them were prepared by thermal conversion of their poly(amic acid)s (PAAs) and the third one by solvent evaporation of the soluble preimidized PI. For the imidized PI films the residual stress vs. bake temperature shows an inclined steplike behavior while this function for soluble PI is approximately linear. The room temperature stress relative to silicon substrates in fully baked films (400°C) is between 40 and 70 MPa and nearly independent of the film thickness. From the stress measurement, the thermal expansion coefficient and Young's moduli have also been obtained. The thermal expansion coefficient and the Young's modulus are in the order of 9.0 × 10−6°C−1and 10 GPa, respectively. These values deviate from those published for bulk material which is explained by the in‐plane orientation of the molecular chains in spun‐o
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