Single ion effect on material and electrical properties of deposited and annealed Al2O3 film on 4H-SiC by atomic layer deposition

Abstract

Abstract It is preferable for the use of highly radiation tolerant SiC devices in space applications due to the strong covalent bond of SiC material. In particular, the MOS devices using SiO2 as a gate dielectric still exhibits a high density of interface states, which enables huge difficulties in accounting for the formation of latent gate damage generated along the heavy ion incidence path. High-k materials represented by Al2O3 gate dielectric offer the most promise to replace the current SiO2 gate dielectric. Al2O3 is a promising high-k material for application in radiation-resistant gate dielectrics on 4H-SiC. The effects of heavy ion irradiation via linear energy transfer (LET) of 99.8 MeV·cm²/mg Bi ions on the surface morphology and interfacial properties of Al2O3 gate dielectric on 4H-SiC were investigated and demonstrated by various characterization methods. It is found that the uniformity of refractive index of 1100 °C annealed Al2O3 films is less affected by radiation compared to as deposited films. Also, the roughness of Rq for the annealed films is varied from 0.28 nm to 0.34 nm before and after irradiation, which shows less degree of increment as compared to as deposited films with increase from 0.24 nm to 0.54 nm. The bombarded pores can be hardly observed in annealed Al2O3. Additionally, the formation of oxygen vacancies or interstitial oxygen contributes to a decrease of Al-O and Al-O-Si bonds after irradiation. Fortunately, the crystallized Al2O3 induced by annealing exhibits a more robust and stable bonding between Al and O and shows less damaged elemental components. These film characterization and underlying mechanisms behind heavy ion irradiation is of meaningful use for development of SiC metal-oxide-semiconductor field effect transistor (MOSFET) irradiation hardening process.