Study on Compensation of Thermal Stresses in the Fabrication Process of Thin-Film Transistor

It is essential to align masks without tolerance in every deposition step when fabricating thin-film transistors (TFTs) on a polymer substrate. However, the shrinkage of the polymer substrate due to thermal effect may arise during the deposition process. We observed the variation of shrinkage as a function of the annealing temperature. It was found that the substrates keep shrinking up to a critical temperature and stay the same above that point. The thermal treatment was conducted on substrates polycarbonate (PC), the polyarylate (PAR), and poly(ether sulfone) (PES). After predeposition annealing, the shrinkage was prevented but deformation was observed on the surface. An inorganic thin film with a different thermal expansion coefficient was employed to remove the deformation and this resulted in the elimination of strain.