Tungsten-related deep levels in a silicon crystal are investigated using microwave and conventional deep level transient spectroscopy. It is found that tungsten atoms have two diffusion constants. Most tungsten atoms stay near the surface of Si crystal, but the remainder go deeper than 1 μm from the surface. It is also found that tungsten atoms make both a hole trap of 0.41 eV and an electron trap of 0.22 eV. Device characteristics are found to be seriously degraded due to deep levels made of deeply diffused tungsten atoms.
The behavior of auxiliary wafers used for Sb diffusion has been studied, with the auxiliary wafers set face to face with diffusion wafers. A high Sb concentration, as high as the solid solubility of Sb into silicon, was attained by auxiliary wafers lapped with alumina powder but not attained by those lapped with carborundum powder. Sapphire substrates, chemical vapor deposition-Al2O3 film deposited on silicon wafers, and Al+ -implanted silicon wafers were used for the auxiliary wafers, and they brought desirable results. Chemical analysis showed that the glass layer grown on the diffusion wafer contained aluminum oxide, which was estimated to give a high Sb concentration in the diffusion wafer.
Diffusion of oxygen atoms into diamond can be introduced by CrO3 treatment followed by an exposure to a hydrogen plasma. From characterization using Rutherford backscattering spectrometry, it is found that the depth distribution of the doped oxygen in the diamond is homogeneous from the surface where its concentration is about 1020 atoms/cm3. The doped oxygen can form cathodoluminescence centers yielding luminescence peaks at 3.75 and 4.64 eV at room temperature. After the diffusion of oxygen atoms, damages in the diamond cannot be detected by Raman scattering spectroscopy.
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