STRESS EFFECTS OF WATER SORPTION IN CURE BAKED PHOTORESIST UNDERLAYERS AN THE MAGNETIC EASY-AXIS OF PERMALLOY FILM OVERLAYERS

Variations in the uniaxial mechanical stress of permalloy films can ch ange the magnetic easy axis of the permalloy films through the magneto strictive effect. Conventional inductive film heads are fabricated wit h the use of cure baked photoresist (CBP). We show that water absorpti on in the CBP can produce significant changes in the magnetic properti es of permalloy films similar to those used in recording head yokes. T he diffusion coefficient of water in 3 mu m thick CBP films was measur ed with a quartz crystal microbalance and found to be 2.2 x 10(-9) cm( 2)/s at 25 degrees C. A large and reversible change in the magnetic ea sy axis is observed in 1 mu thick permalloy films that overlay a mound of CBP when it is exposed to water vapor. We infer from the observed magnetic easy axis changes that uniaxial stresses of greater than 5 x 10(8) dynes/cm(2) are produced due to the swelling and contraction of the underlaying CBP.