A study of thermal stability and annealing behavior of Schottky contacts on Boron doped p-type Cz grown silicon is presented. This study includes defects introduced during electron beam deposition (EBD) process and those introduced by irradiating the silicon sample with protons. Annealing studies of the samples were carried out from room temperature up to 800˚C in argon in steps of 100˚C in order to monitor the defects being annealing out and other defects being introduced at and below the metal-silicon interface. We have used techniques such as current – voltage and capacitance - voltage measurements, to monitor the quality of the contacts as well as advanced characterization techniques such as conventional and Laplace (L) deep level transient spectroscopy (DLTS), to determine the electrical properties of defects, after each annealing step.
Titanium then Molybdenum, each 100 nm thick were deposited on p-Si using EBD process through a circular mask. The molybdenum layer was used to prevent annealing degradation of the metal contacts. We have observed the following hole traps at, 0.32 eV and 0.54 eV above the valence band, induced during EBD processing of Titanium/Molybdenum (Ti/Mo) Schottky contacts on our samples. The annealing studies further revealed hole traps at, 0.15 eV, 0.23 eV, 0.38 eV and 0.59 eV above the valence band. The samples were annealed until all defects have been completely removed. We have observed that all the defects were annealed out at various temperature levels during our study and our samples were defect free at 600 ˚C. Annealing studies were also carried out above 600˚C up to 800˚C in order to check any defects being annealed-in. At this point the sample was irradiated with 2 MeV protons at room temperature and two primary hole traps, 0.15 eV and 0.32 eV were observed. The complete defect structure was then obtained by studying the defect annealing behaviour as well as the depth profiles of the defects as the samples were annealed from 100˚C, in steps of 100˚C. The defects introduced due to proton irradiation were compared to those introduced by electron irradiation on identical samples.
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