Experiments and modeling of thin film processes

Abstract: The processes employed in modern microelectronics are very sophisticated, often representing a complex combination of physical and chemical components with a large number of parameters. Our knowledge and understanding about these processes are often limited; their description is mostly empirical or semi-empirital at best. This thesis treats various aspects of plasma based etching and deposition processes used in material processing for microelectronics.A substantial part of this thesis deals with the further development of the existing modeldescribing reactive sputtering. The model is generalized and refined to include timedependent systems as well as to account for the varying thickness of the compound layerat the target. It is found that the pulse frequency during pulsed DC sputtering does notinfluence the stoichiometry of the deposited compound at frequencies higher than 1 kHz.In a related work the steady state thickness of the compound layer is both calculated andexperimentally verified. A further computational study sheds light on the transport of thesputtered species during pulsed DC sputtering in view of film composition. The transport is studied by Monte Carlo simulations, which indicate that at high pulse frequency (>5kHz) the substrate receives a continuous flux of sputtered atoms.Moreover this thesis utilizes a recently suggested general and universal method for thedetermination of the angular dependence of the etch rate in a dry etch process. Chlorineand fluorine chemistries during polysilicon etching in RIE and ICP plasmas are studied. Itis shown that the angular dependency of the C1 chemistry exhibits a transition from undercosine to over cosine behavior with increasing substrate bias.Finally, as an application of both the etch and deposition studies a capacitor occupying asubstantially smaller chip area was manufactured using high dielectric constant Ta2O5.The material is deposited by reactive sputtering in an oxygen-argon ambient, whilespecific etching recipes have been developed to etch selectively Ta2O5, SiO2 and polysilicon.