1	"R" R. Sun Angstrom Sun Technologies Inc., Acton, MA T. Sammet, M. Hatzistergos, H. Efstathiadis (NanoTech Center at UAlbany)
2	"Copper interconnects in combination with..." Copper interconnects in combination with low-k dielectrics has been under development for high speed and low cost integrated circuits. Diffusion barrier is needed to ensure success in copper metallization schemes due to possible device degradation and failure caused by high diffusivity of copper. Tungsten carbide as one of a few candidates: thermodynamically and chemically stable, good electrical conductivity, obtainable amorphous structure with many deposition technique Barrier layer will be very thin according to ITRS roadmap. This poses challenge to characterization and film quality control. Combination of Grazing angle x-ray reflectometry (XRR) and Spectroscopic ellipsometry (SE) provides a way to precisely characterize such films non-destructively. In this study, WCx films were prepared with the Pulse Chemical Vapor Deposition (PCVD) technique. With thickness obtained from XRR technique, optical model was established for SE analysis.
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4	"1" 1. WCx Film Deposition: Technique: Pulsed CVD Source: Tungsten hexacarbonyl [W(CO)6] for W and Acetylene [C2H2) for carbon. Sequence with Argon purged pulse: W(CO)6 – Ar – C2H2 –Ar Deposition paramters: Partial pressure (Ar) 1 Torr Partial pressure (C2H2) 1 Torr Partial pressure (W(CO)6) 27mTorr Pulse time (Ar) 5s Pulse time (C2H2) 1s Pulse time (W(CO)6) 3s Substrate temperature 380oC 2. Film Evaluation Combined XRR and Ellipsometer XRD: Scintag XDS 2000 x-ray diffractometer (scanned on a sample with 312nm WCx film) Auger Electron Spectroscopy (AES): Physical Electronics Model 15-110B Atomic Force Microscopy (AFM): Nanoscope III
5	"Grazing x-ray reflectance is simply..." Grazing x-ray reflectance is simply a reflection measurement in the hard x-ray range at the grazing angles. At a wavelength of 1.54Å (Cu - Ka), all the materials are quasi-transparent and the optical indices can be expressed by: n = 1-d-ib, where d and b are in the range of 10-5-10-7. So position of the interference fringes gives directly the thickness of the layers. The mean roughness is given by the rate of decrease of the reflectance curve. Thus, layer thickness, roughness, d & b were fitted on XRR reflectivity.
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15	"WCx films grown with a..." WCx films grown with a pulsed CVD were characterized with a combined grazing x-ray reflectometry and spectroscopic ellipsometry technique. With the thickness determined by XRR, it was found that Drude law with two Lorentz absorption bands can be used to describe optical dispersion behaviors for WCx films. Thus, WCx film thickness and surface roughness can be determined by ellipsometry analysis with confidence. AES analysis showed that WCx film grown under present conditions has a nearly W₂C compound stoichiometry with a slightly excess carbon. XRD spectra shows that the films as grown at 380 ^oC has amorphous structure. The investigation of the surface roughness showed an increase of roughness with increasing film thickness. The results from AFM are consistent with both XRR and SE analyses. Performance of WCx barrier in the Cu/barrier/Si stack was evaluated with secco etch method. It is found that 32nm thick WCx in such stack can prevent Cu diffusion up to 500 ^oC
16	"www.angstec.com" www.angstec.com RSun@angstec.com Phone: (978) 204-2317 Fax: (978) 263-6675 Richard Sun @ Angstrom Sun Technologies Inc.