AVS 46th International Symposium
    Thin Films Division Tuesday Sessions
       Session TF-TuM

Paper TF-TuM5
Plasma Enhanced Atomic Layer Deposition of Ta for Diffusion Barrier Applications

Tuesday, October 26, 1999, 9:40 am, Room 615

Session: Advanced Thin Film Formation Chemistry
Presenter: S.M. Rossnagel, IBM Research Division
Authors: A. Sherman, Sherman and Associates, Inc.
S. Malhotra, IBM Research Division
S.M. Rossnagel, IBM Research Division
Correspondent: Click to Email
Atomic Layer Deposition (ALD) is a variation of conventional CVD that uses sequential steps for the adsorption of a monolayer of one reactant and the subsequent exposure of this monolayer to a second reactant, which results in the deposition of roughly a monolayer of the desired elemental or molecular species. This paper describes the use of a free radical second reactant which is produced by a remote plasma source. Because of the high reactivity, it is possible to form films at moderate temperatures rather than the high temperatures of conventional CVD. In this paper, we describe the ALD of Ta, which is used in semiconductor interconect structures for diffusion, adhesion, or nucleation layers in high aspect ratio features which are subsequently filed with Cu. The ALD process is self-limiting in that each 2-step process results in approximately a single atomic layer and film thickness is built up in a controlled manner with a specific number of steps. This is unlike conventional CVD or PVD which are generally timed and require rate calibration. The Ta system uses moderate temperature adsorption of TaCl5 vapor followed by a reaction step using atomic hydrogen from an inductively-coupled rf plasma. The system has been extended to 200mm wafers using a modified Applied Materials Endura (PVD) system, compatible with existing manufacturing tools. Conformal Ta films with uniform thickness have been measured in high aspect ratio features and XRD, AES and RBS data sugget films of high purity adequate for interconnect applications.