Passivation mechanism of thermal atomic layer-deposited Al2O3 films on silicon at different annealing temperatures

Abstract

Thermal atomic layer-deposited (ALD) aluminum oxide (Al2O3) acquires high negative fixed charge density (Qf) and sufficiently low interface trap density after annealing, which enables excellent surface passivation for crystalline silicon. Qf can be controlled by varying the annealing temperatures. In this study, the effect of the annealing temperature of thermal ALD Al2O3 films on p-type Czochralski silicon wafers was investigated. Corona charging measurements revealed that the Qf obtained at 300°C did not significantly affect passivation. The interface-trapping density markedly increased at high annealing temperature (>600°C) and degraded the surface passivation even at a high Qf. Negatively charged or neutral vacancies were found in the samples annealed at 300°C, 500°C, and 750°C using positron annihilation techniques. The Al defect density in the bulk film and the vacancy density near the SiOx/Si interface region decreased with increased temperature. Measurement results of Qf proved that the Al vacancy of the bulk film may not be related to Qf. The defect density in the SiOx region affected the chemical passivation, but other factors may dominantly influence chemical passivation at 750°C.

The impact of thickness and thermal annealing on refractive index for aluminum oxide thin films deposited by atomic layer deposition

“…These applications benefit from the excellent optical and electrical properties of Al 2 O 3 films such as wide bandgap, high conduction, high compatibility with Si substrate, and high dielectric constant [8]. The properties of Al 2 O 3 films have been studied a lot [9-11]. However, most articles focused on electrical and mechanical properties of Al 2 O 3 films.…”

Passivation ability of graphene oxide demonstrated by two-different-metal solar cells

“…For a solar module with an efficiency of 20%, 1% improvement on efficiency can correspond to 5% reduction in cost. Surface structures [ 1 – 3 ] and passivation [ 4 – 7 ] can be utilized to improve the efficiency. Passivation of bare Si surfaces can be easily achieved with hydrogen termination, alkylation, and so on, but the effect may deteriorate in a certain time [ 8 ].…”

Coupled Investigation of Contact Potential and Microstructure Evolution of Ultra-Thin AlOx for Crystalline Si Passivation

“…By taking advantage of the negative fixed charge density of AlO x itself, a passivation with surface recombination velocity (SRV) close to 10 cm/s has been achieved for p-type silicon [10]. Two main approaches have been developed to improve the passivation quality provided by AlO x including thermal annealing [11][12][13][14] and light-soaking [15][16][17].…”