Impact of Direct Plasma Hydrogenation on Thermal Donor Formation in n-Type CZ Silicon

In this paper, the role of a direct plasma hydrogenation treatment and a subsequent air annealing at 450DGC in the formation of thermal donors (TDs) in n-type Czochralski (CZ) silicon is investigated by means of a combination of capacitance-voltage (C-V) and deep-level transient spectroscopy (DLTS). The hydrogenation treatment is found to enhance the introduction rate of TDs at 450DGC for shorter annealing times, reaching its maximum acceleration after 5 h and for the longest plasma hydrogenation studied (2 h). For much longer annealing times, the TD introduction rate becomes independent of the presence of hydrogen in the material. DLTS detects only one donor level having an activation energy, which lowers with increasing doping density of the material, from 0.106 to 0.093 eV. After activation energy correction for the Poole-Frenkel electric-field-enhanced emission, this trap is found to fit well with the conventional singly ionized oxygen thermal donor level. However, from C-V free carrier and DLTS trap concentrations, it is derived that other shallower donors, created by the plasma hydrogenation and 450DGC anneal should play an important role in the free carrier concentration increase of the n-CZ silicon.