IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Applied Surface Analysis Tuesday Sessions
       Session AS-TuP

Paper AS-TuP11
Analysis of Boron-, Germanium- and Fluorine Diffusion through a SiO@sub 2@ Gate Oxide Into Silicon using Secondary Ion Mass Spectrometry

Tuesday, October 30, 2001, 5:30 pm, Room 134/135

Session: Aspects of Applied Surface Analysis II Poster Session
Presenter: F. Persson, Chalmers University of Technology, Sweden
Authors: F. Persson, Chalmers University of Technology, Sweden
H. Svensson, Chalmers University of Technology, Sweden
U. Södervall, Chalmers University of Technology, Sweden
M. Willander, Chalmers University of Technology, Sweden
Correspondent: Click to Email
This project work is a study of diffusion using in-situ B-doped, B- and BF-implanted samples as sources for boron. The main aim of this report is to see how fast boron and germanium moves through a SiO2 gate oxide into a Si-matrix. To get an answer to this and other questions, we have with a SIMS analyzed annealed specimens at different times and temperatures. Using Fick's law and data from the SIMS, the diffusion constants have been determined. An interesting fact emerging is the dependence of the oxide thickness as a barrier against penetration. SiO2<2,5 nm let through atoms at 950°C and 240 s while SiO2<3 nm is pervious first at 1050°C and 60 s. Another observation is the anomalously high values of boron after the annealing, especially where germanium is involved. Besides, boron penetrates faster from a SiGe gate than from pure Si. The fast influx of fluorine from the BF-implanted samples is also worth mentioning. According to our results, in-situ B-doped gate is preferable to B-implanted gate as gate material. In-situ doping provides a highly uniform profile from surface to the SiO2 interface. By implantation it is difficult to achieve a uniform doping profile, which can lead to gate-depletion or by annealing to an increased boron penetration through the oxide.