| AVS 64th International Symposium & Exhibition | |
| 2D Materials Focus Topic | Wednesday Sessions |
| Session 2D+EM+MN+NS-WeA |
| Session: | 2D Device Physics and Applications |
| Presenter: | Il Jo Kwak, University of California at San Diego |
| Authors: | I.J. Kwak, University of California at San Diego J.H. Park, University of California at San Diego S. Fathipour, University of Notre Dame A. Seabaugh, University of Notre Dame C.S. Pang, Purdue University Z. Chen, Purdue University A.C. Kummel, University of California at San Diego |
| Correspondent: | Click to Email |
2D materials such as TMDs(Transition Metal Dichalcogenides), Graphene and BN have attracted great attention as new channel materials for future devices due to their excellent electronic and optical properties. For such devices, sub nanometer thick and defect free gate oxide is an essential part. However, due to the inert surface of the materials, high K oxide such as Al2O3 and HfO2 selectively nucleates on defect sites or step edges. Therefore, for successful integration, preparation of uniform and insulating gate oxides are a matter of importance. In this study, Al2O3 was deposited on 2D materials surface by low temperature ALD using trimethylaluminum(TMA) and H2O without any seeding layer or surface treatments. Using short purge time between two precursor pulses at 50C, a CVD component was induced to provide uniform nucleation sites on the surface. The CVD component generates subnanometer AlOx particles[s1] [file:///C:/Users/kwak1/Downloads/2017_AVS_abstract_bilayer_oxide.docx#_msocom_1] on the surface which provide uniform nucleation sites. In order to obtain lower EOT layer, 10 cycles of Al2O3 ALD was deposited at 50C as a seeding layer and 40 cycles of HfO2 ALD was deposited with Tetrakis(dimethylamido )hafnium (TDMAH) and H2O at 250C. The same oxide was deposited on a SiGe substrate to compare the oxide characteristics. After ALD, MOSCAPs were fabricated to measure electrical properties. AFM measurement revealed that uniform and defect free oxide layers were nucleated on the surfaces. Capacitance-voltage measurement showed that Cox of the bilayer oxide was 2.5 uF/cm2 and the gate leakage current of the oxide was about 10-5 A/cm2 which was comparable to the oxide on a SiGe substrate. Identical bilayer oxide layer was deposited on a dual gated WSe2 FETs . Top gate oxide leakage of the device was about 10-6 A/ cm2. In order to assess the quality of the oxide, a benchmarking study of current density versus EOT of 2D semiconductor FET devices and Si based devises was investigated. The study showed that record-low EOT (1.2 nm) and leakage current (10-8 μA/ μm2) comparable to the best Si devices with La2O3 gate oxide by Iwai et al was achieved by the WSe2 FET. This technique was also applied to initiate nucleation[s2] [file:///C:/Users/kwak1/Downloads/2017_AVS_abstract_bilayer_oxide.docx#_msocom_2] on inert metal surfaces which are important for logic memory devices including selectors. Using the bilayer oxide, insulating oxide was prepared on Au electrodes of a MOSFET device. The leakage current of the oxide was as low as 10-7 A/ cm2.