| AVS 62nd International Symposium & Exhibition | |
| Electronic Materials and Processing | Monday Sessions |
| Session EM+NS+PS-MoM |
| Session: | More Moore! Materials and Processes to Extend CMOS Another Decade |
| Presenter: | Seongkyung Kim, Seoul National University, Korea, Republic of Korea |
| Authors: | S.K. Kim, Seoul National University, Korea, Republic of Korea H.J. kim, Seoul National University, Korea, Republic of Korea |
| Correspondent: | Click to Email |
Recently Ⅲ-Ⅴ compound materials have attracted significant attention as promising channel materials for sub-10 nm logic MOSFET due to their high mobility. GaSb is a strong candidate for pMOSFETs because of its high hole mobility in addition to the insolubility of its native oxides. Even with the outstanding electrical properties of GaSb, there are some drawbacks related to the instability of its native oxides and metallic layer of elemental Sb. The native oxides and metallic layer of elemental Sb are considered to be sources of Fermi level pinning and flat C-V curves. Therefore, it is necessary to improve surface treatment methods. Since it is possible to eliminate its native oxides and elemental Sb by heating them, it is essential to research temperature related surface treatments.
In this study, various ALD temperatures from 190 oC to 310 oC and pre-RTP(Rapid Thermal Process), which is first introduced here as a pre-deposition treatment, have been adopted for eliminating the remaining native oxides after cleaning. N2 gas atmosphere is used to suppress the oxygen to interact with GaSb surface for the pre-RTP. GaSb metal-oxide-semiconductor capacitors were fabricated on p-type GaSb, which has a carrier concentration of 1.0~2.0 x 1017 cm-3. GaSb was degreased with acetone, ethanol, and isopropane for 5 minutes each and then etched by HCl. 10 nm of Al2O3 has been deposited as a gate dielectric with TMA and DI water by thermal ALD. For the metal gate, a Pt electrode has been deposited with an electron-beam evaporator.
When the deposition temperature increases, the Ga2O3 peak increases and the substrate peak decreases under XPS analysis. It is observed that the amount of Sb increases at the GaSb/Al2O3 interface as the deposition temperature increases in AES depth profiles. Both Ga2O3 and elemental Sb have increased generation as the deposition temperature increases, since the surface chemical reactions are accelerated by increased temperature. The CV curve becomes flat as the deposition temperature increases. It indicates that Ga2O3 has a flattening effect of the CV curve and the more amount of Ga2O3 that is generated, the flatter the CV curve will become.
Desorption of the native oxides and elemental Sb should occur by annealing the substrate. After the pre-RTP, the amount of elemental Sb increases, since the remaining native oxide, after cleaning, is reduced by increased temperatures. The remaining native oxide Sb2O3, after cleaning, supplies oxygen to the substrate and becomes elemental Sb. The leakage current increases with pre-RTP. It shows that the elemental Sb increases the leakage current. Further study on optimizing pre-RTP conditions is needed.