ALUMINUM NITRIDE SUBSTRATE, ALUMINUM NITRIDE CIRCUIT BOARD, SEMICONDUCTOR APPARATUS, AND METHOD FOR MANUFACTURING ALUMINUM NITRIDE SUBSTRATE

摘要

The present invention provides an aluminum nitride substrate and an aluminum nitride circuit board having excellent insulation characteristics and heat dissipation properties and having high strength, a semiconductor apparatus, and a method for manufacturing an aluminum nitride substrate. An aluminum nitride substrate according to the present invention is an aluminum nitride substrate having aluminum nitride as a main component and comprising a polycrystal containing a plurality of aluminum nitride grains, and complex oxide grains being present at grain boundaries of the aluminum nitride grains and including a rare earth element and aluminum, wherein the aluminum nitride grains have a maximum grain size of 10μm or less, the complex oxide grains have a maximum grain size smaller than the maximum grain size of the aluminum nitride grains, the number of the complex oxide grains having a grain size of 1μm or more being present in a field of view of 100μm×100μm of a surface of the aluminum nitride substrate observed is 40 or more, the aluminum nitride substrate has a bending strength of 400 MPa or more in an unpolished state after firing, and the aluminum nitride substrate has a volume resistivity of 1012Ωm or more.