| AVS 64th International Symposium & Exhibition | |
| Thin Films Division | Wednesday Sessions |
| Session TF+EM+MI-WeM |
| Session: | Thin Films for Microelectronics |
| Presenter: | Pei-Yu Chen, The University of Texas at Austin |
| Authors: | P.Y. Chen, The University of Texas at Austin A. Posadas, The University of Texas at Austin S. Kwon, The University of Texas at Dallas Q. Wang, The University of Texas at Dallas M. Kim, The University of Texas at Dallas A. Demkov, The University of Texas at Austin J.G. Ekerdt, The University of Texas at Austin |
| Correspondent: | Click to Email |
Motivated by the need for faster device speed, the industry is considering compound semiconductors, such as gallium nitride (GaN) in the III-V family of materials, which have higher electron mobility than silicon. To passivate the nitride surfaces and enable GaN-based electronic devices, a high quality and thermally stable dielectric layer material is required. Recently, rare earth sesquioxides have received attention due to their electrical properties, thermal and chemical stability, and relatively high dielectric constant [1]. Using atomic layer deposition (ALD) with erbium tris(isopropylcyclopentadienyl) [Er(iPrCp)3] and water, crystalline cubic (C-type) Er2O3 is successfully grown on GaN at 250 °C for the first time. ALD enables the conformal deposition of Er2O3 film on GaN and features a stable growth rate of 0.82 Å/cycle in this work. In-situ x-ray photoelectron spectroscopy is used to determine film composition and in-situ reflection high-energy electron diffraction is used to verify the surface order and the film crystallinity at various stages in the growth process. The cubic structure of Er2O3 is confirmed by a combination of both out-of-plane and in-plane X-ray diffraction (XRD). The orientation relationships between C-Er2O3 film and GaN substrate are C-Er2O3(222) || GaN(0001), C-Er2O3(-440) || GaN(11-20), and C-Er2O3(-211) || GaN(1-100). The out-of-plane C-Er2O3(222) XRD peak shifts as a function of film thickness indicating a slight change in d-spacing caused by the presence of strain at the interface as shown in Fig. 1(a)(b). The observed tensile strain results from the lattice mismatch between GaN and Er2O3. As the film thickness increases, the C-Er2O3 becomes more relaxed. In-plane XRD also displays peak shifts with opposite trend from the out-of-plane scan as expected. Scanning transmission electron microscopy (STEM) is used to examine the microstructure of C-Er2O3 and its interface with GaN and is in excellent agreement with the simulated atomic positions (Fig. 1(c)). An interfacial layer consisting of 1-3 atomic-layers is observed by STEM. The electron energy loss spectroscopy (EELS) profiles for Ga, Er, O, and N suggest partial oxidization of GaN at the interface. Overall, this work demonstrates a low temperature, all-chemical process for the growth of crystalline C-Er2O3 on GaN by ALD.
[1] R. Dargis, A. Clark, F. E. Arkun, T. Grinys, R. Tomasiunas, A. O'Hara, and A. A. Demkov, “ Monolithic integration of rare-earth oxides and semiconductors for on-silicon technology,” J. Vac. Sci. Technol. A, 32, 041506 1-8 (2014).