AVS 46th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM1-ThM

Paper EM1-ThM7
Surface Modification and Cleaning Enhancement of TaSiN Films with Dilute Hydrofluoric Acid*

Thursday, October 28, 1999, 10:20 am, Room 608

Session: Cu, Low-k Dielectrics and Interfaces
Presenter: P.J.S. Mangat, Motorola, Inc.
Authors: P.J.S. Mangat, Motorola, Inc.
W.J. Dauksher, Motorola, Inc.
K.D. Cummings, Motorola, Inc.
W.L. O'Brien, Mad City Labs, Inc.
Correspondent: Click to Email
Amorphous TaSiN and TaSi alloys films are of great interest for application in the fabrication of reticles for Next Generation Lithography (NGL) and for incorporation in semiconductor devices. TaSiN films act as absorber and scatterer, respectively, on the masks for X-Ray Lithography and Scattering with Angular Limitation in Projection Electron-beam Lithography. Recently, we have successfully extended its application to an absorber for Extreme Ultra-Violet Lithography reticles. The films have been extensively characterized in terms of resistivity, composition, defectivity, surface roughness, crystalline state, and chemical robustness. One little understood, but critical characteristic of these films, is that they undergo stress change from tensile to compressive upon interaction with dilute Hydrofluoric (HF) acid. We have investigated the cause of this behavior using high-resolution core level (Ta 4f and Si 2p) photoemission spectroscopy with synchrotron radiation. Our results using photoemission and Auger electron spectroscopy confirm that surfaces of as-deposited and annealed films are composed primarily of Si-oxides with trace amounts of Ta-oxide. Upon interaction with HF, the surface oxide undergoes major reorganization and Ta gets heavily oxidized resulting in the formation of Ta2O5. Such a reaction would lead to a build up of strain in the oxidized region, which we interpret as being contributing factor for the observed stress changes in the TaSiN thin films. We further extended the study in terms of desorbtion of the surface oxide. Upon annealing the surface, we observe that the temperature for oxide desorbtion is reduced by 200 oC from 650 oC due to the HF interaction. This can be attributed to a change in the bonding configuration by HF, wherein the Si-O bonds are broken and weak Ta-O bonds are formed. This causes the loosely bonded oxide to desorb at lower temperatures. * Work Performed at Synchrotron Radiation Center,UW-Madison, Stoughton, WI 53589.