Hydrogenation and annealing kinetics of group-III acceptors in oxidized silicon

• Published in: Journal of applied physics 1985-01, Vol.57 (12), p.5148-5161
• Main Authors: Sah, Chih-Tang, Pan, Samuel Cheng-Sheng, Hsu, Charles Ching-Hsiang
• Format: Article
• Language: English
• Subjects: Applied sciences; Electronics; Exact sciences and technology; Interfaces; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.335249

Acceptor (B, Al, Ga, and In) density versus time curves during avalanche electron injection (AEI) and constant-temperature thermal annealing experiments obtained from metal-oxide-silicon capacitors (MOSCs) show two distinguishable phases. The time dependence of the acceptor density during AEI shows an initial delay due to electron-impact release of hydrogen trapped in the gate conductor and oxide layers and a long-time decay due to the thermal capture and electron-impact emission of the atomic hydrogen at the group-III acceptor centers in the silicon surface layer. Thermal anneal of hydrogenated acceptor begins at 50 °C for boron and 100 °C for Al, Ga, and In. The initial phase during thermal annealing of AEIed MOSCs follows a first order kinetics at higher annealing temperatures, reaching a steady-state acceptor density before the second phase begins. The long-time anneal follows strictly a second-order kinetics which is rate limited by the recombination of two hydrogen atoms to form a molecule. Incomplete anneal is observed at higher temperatures when the dissociation rate of the hydrogen molecule becomes comparable with the recombination rate of two hydrogen atoms. Analytical solutions are obtained which account for all the details of the observed hydrogenation and annealing curves. These solutions are used to evaluate the thermal capture and emission rates and electron-impact emission rates of hydrogen or proton at the group-III impurity centers and the bimolecular generation and recombination rates of hydrogen. A new concept of hydrogen or proton traps in analogy to the electronic hole or electron traps is introduced to analyze the kinetics and account for the observed chemical trends between thermal capture and emission rates, thermal activation energy and bond strength. Chemical trends are noted which are consistent with the trapped proton activation energy and hydrogen bond strength trend, B