Tantalum pentoxide (Ta2O5) thin films for advanced dielectric applications

This paper reviews the present knowledge on tantalum pentoxide (Ta2O5) thin films and their applications in the field of microelectronics and integrated microtechnologies. Different methods used to produce tantalum oxide layers are described, emphazing elaboration mechanisms and key parameters for each technique. We also review recent advances in the deposition of Ta2O5 in the particular field of microelectronics where high quality layers are required from the structural and electrical points of view. The physical, structural, optical, chemical and electrical properties of tantalum oxide thin films on semiconductors are then presented and essential film parameters, such as optical index, film density or dielectric permittivity, are discussed. After a reminder of the basic mechanisms that control the bulk electrical conduction in insulating films, we carefully examine the origin of leakage currents in Ta2O5 and present the state-of-the-art concerning the insulating behaviour of tantalum oxide layers. Finally, applications of tantalum oxide thin films are presented in the last part of this paper. We show how Ta2O5 has been employed as an antireflection coating, insulating layer, gate oxide, corrosion resistant material, and sensitive layer in a wide variety of components, circuits and sensors. (C) 1998 Elsevier Science S.A. All rights reserved.