| AVS 56th International Symposium & Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM-TuA |
| Session: | High-K Dielectrics on High Mobility Substrates |
| Presenter: | H.D. Lee, Rutgers University |
| Authors: | H.D. Lee, Rutgers University T. Feng, Rutgers University L. Yu, Rutgers University D. Mastrogiovanni, Rutgers University A. Wan, Rutgers University T. Gustafsson, Rutgers University E. Garfunkel, Rutgers University |
| Correspondent: | Click to Email |
The integration of high-k dielectrics with high mobility III-V semiconductors is important due to the need for higher speed and lower power electronic devices than are offered by Si-based technologies. While high-k dielectric deposition on GaAs and InGaAs semiconductors appears particularly promising, the removal of native oxides and the growth an ideal dielectric layer remains a serious challenge. This obstacle arises in part from the high density of defects present at most GaAs-dielectric interfaces, and is related to Fermi-level pinning at the interface. Several groups have shown that chemical cleaning and subsequent passivation of the interface prior to dielectric deposition can greatly reduce the interface state density (Dit). However, few passivation solutions are practical for future large scale CMOS device manufacturing.
Although several studies (including our own) have shown the reduction of native oxides on GaAs and InGaAs during atomic layer deposition (ALD) of dielectrics, detailed structural and chemical information about the interface and reduction process have not been reported. We have examined depth profiles of the elements in native oxides and ALD-deposited Al2O3 layers on GaAs substrates with an integrated tool that enables ALD growth with in situ characterization by medium energy ion scattering spectroscopy (MEIS). Films were also analyzed by x-ray photoelectron spectroscopy (XPS).
We will present data on the reduction of surface “native” oxides from GaAs substrates following reactions with trimethylaluminum (TMA) precursor. MEIS and XPS measurements after one single TMA pulse without oxygen exposure show that ~65% of the native oxide including ~75% of the As oxides are reduced, and a 5Å oxygen rich aluminum oxide layer is formed. XPS also shows that 3 additional TMA pulses reduce all As oxides to a level below our detection limit, and the Ga oxides were also reduced substantially. Further MEIS study of Al2O3 grown with the normal atomic layer deposition cycles of TMA and water shows that the growth rate of Al oxide during the reduction of native oxides is faster than the rate after the reduction. The preferential interface reduction of native oxides (especially AsO) helps create a higher capacitance, lower interface defect density CMOS gate stack.