AVS 50th International Symposium
    Applied Surface Science Monday Sessions
       Session AS-MoM

Paper AS-MoM10
Thickness, Dose and Distribution Measurements of Silicon Oxynitride Ultra-thin Films

Monday, November 3, 2003, 11:20 am, Room 324/325

Session: Practical Surface Science
Presenter: R.K. Champaneria, Thermo Electron, UK
Authors: R.K. Champaneria, Thermo Electron, UK
P. Mack, Thermo Electron, UK
R.G. White, Thermo Electron, UK
J. Wolstenholme, Thermo Electron, UK
Correspondent: Click to Email
The continuing requirement for smaller equivalent oxide thickness (EOT) for transistor gate dielectrics has lead to the introduction of new materials with higher dielectric constants than silicon dioxide (high-k dielectrics). At present, silicon oxynitride is an important material for this application. X-ray photoelectron spectroscopy (XPS) is a well-known surface analytical technique. It can provide quantitative information, not only about chemical elements but also their chemical state. The information depth of the technique varies with the material under investigation but is in the region of 5-10 nm for materials commonly encountered in semiconductor device fabrication. This information depth can be controlled by means of the angle at which the photoelectrons are collected (angle resolved XPS or ARXPS) and, by collecting the signal at a number of angles, it is possible to generate a concentration depth profile. Since no material is removed in the generation of the concentration profile, the method is essentially non-destructive. Data will be shown to illustrate how ARXPS can provide accurate and precise measurements of thickness and nitrogen dose in oxynitrides. It will be shown that XPS measurements at a single angle cannot provide accurate measurements of the dose. Using line scans or maps, the uniformity of thickness and dose across a wafer can be measured. ARXPS data can also be used to reconstruct concentration depth profiles. These profiles reveal both the total dose and the distribution of nitrogen in each of its chemical states. It will be shown that methods of profile generation involving sputtering can produce misleading results.