AVS 46th International Symposium
    Applied Surface Science Division Tuesday Sessions
       Session AS-TuM

Paper AS-TuM4
Cesium Depth Profiling of Ultra-Shallow Implants

Tuesday, October 26, 1999, 9:20 am, Room 6A

Session: Ion Beam Analysis and Depth Profiling
Presenter: E. Niehuis, ION-TOF GmbH, Germany
Authors: E. Niehuis, ION-TOF GmbH, Germany
T. Grehl, ION-TOF GmbH, Germany
D. Lipinsky, ION-TOF GmbH, Germany
O. Brox, Universität Münster, Germany
A. Benninghoven, Universität Münster, Germany
Correspondent: Click to Email
Currently fabricated junction depths are between 50 nm and 100 nm, and they will decrease to about 10 nm for future deep sub-micron process technology. High depth resolution SIMS profiling is needed to control implant dose, junction depth, dopant distribution and its modification by thermal and chemical processes. In order to improve the depth resolution of SIMS, primary beam energies have been reduced over the last few years from several keV to a few hundred eV. In particular, oxygen depth profiling of B in Si in the sub-keV range has been studied in great detail over the last 2 years. In Cs depth profiling at low energies for the analysis of electronegative elements like As and P in Si two specific problems arise: 1. The decrease of the sputter yield with Cs energy results in a significant increase of the Cs surface concentration under steady state conditions. This has a strong influence on secondary ion emission and results in erosion rate changes in the transient regime. 2. A significant part of the implant dose is located in a native oxide or a screening oxide of the implantation process. Negative SI yields in a SiO@sub 2@ and Si matrix are quite different leading to errors in profile shape and implantation dose. We have investigated Cs sputtering at sub-keV energies using a TOF-SIMS instrument in the dual beam mode. A low energy Cs beam generates the sputter crater while a pulsed Ga beam at 15 keV energy probes the composition in the center of the crater. As the conditions of the analytical beam (energy, angle, spot size) are not changed with Cs beam energy, this dual beam mode is well suited for systematic studies in the very low energy regime. This paper will discuss the change of the positive and negative SI emission and erosion rate for SiO@sub 2@ and Si with Cs sputter energy. In addition, we investigate correction procedures in the transient regime and at the SiO@sub 2@/Si interface region.