A micro-Raman spectroscopic investigation has been performed to observe structural disorder in each grain of aluminum nitride ceramics as semiconductor equipment parts. A selective thermal oxidation treatment normalizes a different rate of a corrosion reaction depending on the crystal face and consequently improves the corrosion resistance. Upon thermal oxidation treatment, line widths of Raman bands increased more in grains including mainly crystals with (100) preferred orientation than in those of (002), indicating that (100) faces oxidize preferentially rather than (002) faces. According to Raman shift from the oxidized sample, oxidation induces residual compressive stress for grains including a large number of (100) prefer-oriented crystals. On fluorination of the oxidized sample, no increase of line widths was observed in both kinds of grains, suggesting that prior anisotropic thermal oxidation treatment of (100) faces, which are more sensitive to corrosion than (002) faces, inhibits the progress of corrosion.
