Low-damage grinding process of gallium oxide based on cerium oxide

Abstract

The ultra-wide bandgap semiconductor material β-Ga₂O₃ exhibits potential in power devices and UV detectors. However, its hard and brittle characteristics and cleavage properties result in severe damage during processing. This study used cerium oxide (CeO₂) in an alkaline solution to grind β-Ga₂O₃. The (010) β-Ga₂O₃ exhibited less surface and subsurface damage (SSD), although it encountered significant SSD during processing. SEM of (010) β-Ga₂O₃ cross sections showed that the SSD caused by CeO₂ is plastic slip. Median cracks with a depth of less than 1 μm were only observed in some areas. In contrast, diamond produces microcrack defects in the subsurface up to a depth of 2 μm. When grinding with CeO₂, bonds of Ga-O-Ce are formed with active oxygen on the surface of β-Ga₂O₃. The material is removed by combining mechanical and “chemical tooth” models. A characteristic peak of this structure appears at 530.01 eV in the O 1s spectrum of the sample's XPS. The mechanical action of CeO₂ deforms the surface structure, removing surface damage through ductile domain removal. After 3 h of CMP, the FWHM of the rocking curve for the CeO₂ ground sample decreased from 668 ± 20 ″ to 61 ± 5 ". In contrast, the diamond ground sample only reduced from 643 ± 23 ″ to 210 ± 8 ". This decreased rate for the CeO₂ sample was significantly higher than for the diamond. The method eliminates the damage by combining actions, reducing new damage. It has research value and economic benefits for optimizing the process and obtaining damage-free β-Ga₂O₃ substrates.