| AVS 63rd International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF-ThP |
| Session: | Thin Films Poster Session |
| Presenter: | Thomas Grehl, ION-TOF GmbH, Germany |
| Authors: | T. Grehl, ION-TOF GmbH, Germany P. Brüner, ION-TOF GmbH, Germany R. ter Veen, Tascon GmbH, Germany M. Fartmann, Tascon GmbH, Germany T. Blomberg, ASM Microchemistry Ltd., Finland M. Tuominen, ASM Microchemistry Ltd., Finland |
| Correspondent: | Click to Email |
GaSb is a promising candidate as a III-V channel material for p-channel for future metal-oxide-semiconductor field-effect transistors (p-MOSFETs) due to its high hole mobility. Also other applications like thin film solar cells or other optoelectronic applications are being discussed. In many of these applications, a well-controlled deposition of GaSb thin films is required.
During deposition process development, characterization of the early stages of film growth is essential to optimize the deposition conditions and possible pre-treatments of the substrate. Low Energy Ion Scattering (LEIS) is a valuable tool for this: Its key feature is the ability to quantitatively determine the composition of the outermost atomic layer. In addition, it non-destructively obtains information about the composition of the first few nm of the sample. These features make it the ideal technique to follow the nucleation of the film and its development until the film is closed. This includes information about the initial growth per cycle as a function of the cycle number, the accurate determination of film closure, and monitoring of unexpected contamination.
The instrument in this study is equipped with a high-sensitivity and high-resolution energy analyzer to record the energy spectrum of noble gas ions scattered back from the sample surface. The 3 – 8 keV ions undergo binary collisions with surface atoms, leading to a characteristic energy loss depending on the mass of the scattering partner. The energy loss is used for identification, while the intensity is used for quantifying the surface coverage per element. Ions which were scattered at sub-surface atoms are detected with a lower probability due to specific neutralization and reionization effects. At the same time they exhibit a depth-dependent energy loss by traveling through the solid. This explains why on the one hand the surface composition can quantified with ultimate surface sensitivity of one atomic layer, and at the same time the composition of the first few nm can be determined without sputtering.
The GaSb films in this study were deposited on SiO2, using a GaCl3 + Sb(SiMe3)3 chemistry at 110 °C in a Pulsar 2000 reactor. Samples were taken out after 1 – 20 ALD cycles and analyzed using LEIS. As the analysis involved transport of the samples through air, an appropriate method to remove atmospheric hydrocarbons from the surface had to be applied. For this purpose, different treatments were tested for their ability to remove the adsorbents while minimizing the effect on the composition of the surface.