Hall effect spectroscopy of thermal donors in silicon films synthesized by oxygen implantation

Abstract

The electrical properties of silicon layers formed by implantation of oxygen (SIMOX) are controlled by oxygen thermal donors (TDs) which are activated in a high density (10 15–10 16 cm −3) during technological processes. It has been found that 650°C is the annealing temperature at which TDs are activated in the lowest density. The conventional Hall effect analysis consists of deriving the electrical TD ionization energy from the activation energy in the Arrhenius plot of n vs. 1/T. However, it is well known that this method is not very accurate in the case of oxygen defects in silicon since many levels coexist. Thus, we propose a spectroscopic analysis of Hall effect measurements based on a differential evaluation of the n vs. 1/T characteristics which clearly reveals the existence of TDs in SIMOX thin films. The films annealed at 650°C for 1 h showed only deep TD levels (240 and 300 meV), whereas shallow TD levels (45–65 meV) were activated in arsenic-implanted films. These TD levels, which were not detected in the conventional analysis, were responsible for an apparent decrease in the activation energy in the high temperature range.