| AVS 55th International Symposium & Exhibition | |
| Surface Science | Friday Sessions |
| Session SS+EM+NC-FrM |
| Session: | Semiconductor Surfaces |
| Presenter: | M. Milojevic, University of Texas at Dallas |
| Authors: | M. Milojevic, University of Texas at Dallas B. Brennan, Dublin City University, Ireland H.C. Kim, University of Texas at Dallas F.S. Aguirre-Tostado, The University of Texas at Dallas J. Kim, University of Texas at Dallas R.M. Wallace, University of Texas at Dallas G. Hughes, Dublin City University, Ireland |
| Correspondent: | Click to Email |
The combination of high k dielectric materials on high mobility III-V semiconductors offers the potential for MOSFETs with larger transconductance at lower operating voltages than are currently achievable with silicon based devices. Arsenic and gallium oxidation states are suspected to be the cause of Fermi level pinning, and therefore the removal or minimization of such states is required in order to develop practical devices. This study investigates the atomic layer deposition (ALD) of aluminium and lanthanum oxide based high-k dielectrics on the ammonium sulphide (NH4)2S and ammonium hydroxide NH4OH treated In0.53Ga0.47As surface grown by metal organic vapour phase epitaxy (MOVPE) on lattice matched InP substrates using in-situ surface chemical analysis. Monochromatic, in-situ X-ray photoelectron spectroscopy (XPS) and ex-situ atomic force microscopy (AFM) were used to determine optimal (NH4)2S conditions based on varying the sulphur concentration, temperature and treatment time. The ALD of the high-k films carried out at 300°C consists of a metal precursor pulse followed by a water pulse with an high purity N2 carrier gas and was sequentially examined with in-situ XPS after every half cycle of the deposition process to determine the initial interfacial oxide and substrate reactions taking place during the growth. A ‘clean up’ effect, whereby the ALD process reduces native oxides at the surface during high-k deposition, is well known for thin dielectric films. In the case of TMA/water based deposition of Al2O3, we have found that the first TMA pulse is responsible for the removal of virtually all of the arsenic oxide left on the surface after the pre-treatments, especially with (NH4)2S, to within the detection limits of XPS. Gallium oxide bonding is reduced to approximately a monolayer consistent with a Ga-O-Al bond at the interface. Similar results for La-based precursor reactions will also be presented. Capacitance-voltage measurements were also carried out on metal oxide semiconductor MOS devices formed after the high-k dielectric growth. Supported by MARCO MSD Focus Center, Science Foundation Ireland, and FUSION.