AVS 49th International Symposium
    Plasma Science Wednesday Sessions
       Session PS+TF-WeP

Paper PS+TF-WeP9
TaN Diffusion Barriers by Chemical-Enhanced Physical Vapor Deposition (CEPVD)

Wednesday, November 6, 2002, 11:00 am, Room Exhibit Hall B2

Session: Plasma Etching & Deposition
Presenter: N. Li, University of Illinois, Urbana-Champaign
Authors: N. Li, University of Illinois, Urbana-Champaign
J.P. Allain, University of Illinois, Urbana-Champaign
D.N. Ruzic, University of Illinois, Urbana-Champaign
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Ta and TaN films deposited by physical vapor deposition (PVD) or ionized PVD (iPVD) are widely used as a conducting diffusion barrier layer in ultra-large scale integrated (ULSI) devices to prevent migration of Cu into adjacent dielectrics. While PVD films lack the highly conformal sidewall coverage of chemical vapor deposition (CVD) or metalorganic CVD (MOCVD), they offer high density and low resistivity desired for optimum barrier performance. Since the parameter space of PVD is quite different from CVD, getting the best attributes of both methods is problematic. We describe a novel process called chemically-enhanced physical vapor deposition (CEPVD) that, by the addition of a proper amount of precursor in the vicinity of the substrate, has the potential to deposit films with PVD quality and CVD step coverage. A Ta target is sputtered in a magnetron system with the Ta-containing metal-organic precursor vapor, TBTDET, in combination with a reactive (N@sub 2@) carrier gas and an RF-powered secondary ionization plasma. In this preliminary experiment, planar films were deposited on silicon wafers at different pressure, RF incident power, substrate temperature and bias voltage. The ionized metal deposition conveys significant energy to the surface through bombardment, promoting film adhesion and generating films of stable crystallographic orientation. In addition the ion bombardment enhances the impurity volatilization and reduces the substrate temperature needed for chemical decomposition. Deposition rate and ionization fraction are measured using a gridded energy analyzer and a quartz crystal microbalance (QCM). Surface morphology are visualized using SEM and AFM; film composition and microstructure are characterized by XPS and XRD, respectively. Resistivity is evaluated by a four-point probe. Extension of the method to patterned structures is also discussed.