AVS 61st International Symposium & Exhibition
    Thin Film Friday Sessions
       Session TF+AS-FrM

Paper TF+AS-FrM8
Low Energy Ion Scattering Data Analysis for Ultra Thin Films using TRBS

Friday, November 14, 2014, 10:40 am, Room 307

Session: Thin Film Characterization
Presenter: Thomas Grehl, ION-TOF GmbH, Germany
Authors: T. Grehl, ION-TOF GmbH, Germany
P. Brüner, ION-TOF GmbH, Germany
B. Detlefs, CEA-LETI, France
E. Nolot, CEA-LETI, France
H. Grampeix, CEA-LETI, France
E. Steinbauer, Johannes Kepler University, Austria
P. Bauer, Johannes Kepler University, Austria
H.H. Brongersma, ION-TOF GmbH, Germany
Correspondent: Click to Email
Low Energy Ion Scattering (LEIS) is well known for its extreme surface sensitivity, allowing elemental characterization and quantification of the outermost atomic layer. This makes it a valuable tool for thin film analysis, e.g. to gain insights to the early stages of film growth or determine film closure. Also contamination analysis can be performed, again making use of the high surface sensitivity to assess the surface composition as the basis for subsequent deposition steps.

In addition, distinct information about sub-surface layers is obtained in a non-destructive way, giving information about the depth distribution of elements up to 10 nm. Although the mechanism for this in-depth signal is well understood, a model for the quantification of the data needs to be established.

One way of modeling the data is demonstrated using TRBS [1], a specialized version of TRIM [2] which was optimized for simulating ion scattering. Combining the TRBS data for backscattering of primary ions and an empirical model for the energy dependent reionization probability gives promising results. By fitting the simulation to the measured data conclusions about film composition, thickness and interface quality can be drawn.

This approach will be demonstrated using different thin film examples. One of the sample sets consisting of HfO2/Al2O3 stacks also characterized by AR-XPS, XRR and GIXRF will be discussed in detail. We will show the possibility to determine film thickness variations in the Å range. These measurements can be performed in a few minutes without destroying the sample by sputtering. At the same time, the composition of the outer atomic layer is detected, making the approach well suited for routine analysis of films during or after deposition.

[1] A particularly fast TRIM version for ion backscattering and high energy implantation, Biersack, J.P.; Steinbauer, E.; Bauer, P.; Nucl. Instr. and Meth. in Phys. Res., B61, 1991, 77-82

[2] The Stopping and Range of Ions in Solids; Pergamon, New York, 1985