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AssigneeNGK Insulators, Ltd.
InventorsTomohiko Shibata, Yukinori Nakamura
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A sapphire single crystal wafer 11 having a diameter not less than two inches and having an off-angled surface which is obtained by rotating an R (1-102) surface about a [11-20] axis by a given off-angle is introduced in a CVD apparatus, and a double-layer structure of first and second aluminum single crystal layers 12 and 13 is deposited on the off-angled surface of the sapphire single crystal wafer by MOCVD. The thus deposited aluminum single crystal layer 13 has (1-210) surface. The first aluminum nitride single crystal layer 12 serves as a buffer layer and has a thickness of 5-50 nm, and the second aluminum nitride single crystal layer 13 has a thickness not less than 1 μm. The off-angle is preferably set to a value not less than ±1°, much preferably a value ±2°, more preferably a value not less than −3°, and particularly preferable to a value within a range from −2°-+10°. The thus obtained aluminum nitride single crystal layer 12, 13 has no clack formed therein, has an excellent piezo-electric property, and has a high propagating velocity for surface acoustic wave.
A method of manufacturing a substrate for a surface acoustic wave device, said substrate comprising a sapphire single crystal substrate made of α-Al2O3 and an aluminum nitride single crystal layer formed on a surface of said substrate, wherein said surface of the sapphire single crystal substrate is formed by an off-angled surface that is obtained by rotating an R(1-102) surface about an (11-20) axis by a given off-angle, and said aluminum nitride single crystal layer is formed by an aluminum nitride single crystal layer deposited on said off-angled surface of the sapphire single crystal substrate by a metal organic chemical vapor deposition to have a (1-210) surface, said method comprising the steps of:
Dependencies are inferred from the claim text.