Engineering epitaxial γ-Al2O3 gate dielectric films on 4H-SiC

Abstract

The formation of epitaxial γ-Al2O3 thin films on 4H-SiC was found to be strongly dependent on the film thickness. An abrupt interface was observed in films up to 200 Å thick with an epitaxial relationship of γ-Al2O3(111)‖4H-SiC(0001) and γ-Al2O3(44¯0)‖4H-SiC(112¯0). The in-plane alignment between the film and the substrate is nearly complete for γ-Al2O3 films up to 115 Å thick, but quickly diminishes in thicker films. The films are found to be slightly strained laterally in tension; the strain increases with thickness and then decreases in films thicker than 200 Å, indicating strain relaxation which is accompanied by increased misorientation. By controlling the structure of ultrathin Al2O3 films, metal–oxide–semiconductor capacitors with Al2O3 gate dielectrics on 4H-SiC were found to have a very low leakage current density, suggesting suitability of Al2O3 for SiC device integration.

Densification of Thin Aluminum Oxide Films by Thermal Treatments

“…Figure 9 gives a summary of the measured values for all investigated samples. For as-deposited films, breakdown fields up to 8 MV/cm were measured in agreement with reported values [35] [36]. This value is substantially lower after high temperature annealing.…”

Re-distribution of oxygen at the interface between γ-Al2O3 and TiN

“…Nowadays the (poly) crystalline γ-Al 2 O 3 layers offer advantageous alternative to the amorphous (a-) alumina films widely applied in a variety of electron devices. For example, the increase of the conduction band (CB) offset at interfaces with semiconductors upon alumina crystallization 17, 18 allows for better gate insulation of wide-bandgap channel materials such as GaN 19 and SiC 20, 21 . In particular, polycrystalline γ-Al 2 O 3 films obtained by annealing-induced crystallization of the atomic-layer-deposited (ALD) alumina 17, 22 are seen as superior inter-gate insulator in charge trapping memory cells 23 eventually allowing for 3-dimensional integration, improving the cell performance 23 , as well as promising a high-temperature operation 24 .…”

Physical characterization of post-deposition annealed metal-organic decomposed cerium oxide film spin-coated on 4H-silicon carbide

“…One approach to overcome this is to replace the relatively low-k nitrided-SiO 2 with a gate oxide with higher k value [1]. Numerous high-k gate oxides, such as Al 2 O 3 [21][22][23][24], La 2 O 3 [25], HfO 2 [26][27][28], Gd 2 O 3 [29], AlN [30], and ZnO [31], have been deposited on SiC substrate to reduce the electric field in the oxides.…”