Surface acoustic wave device and surface acoustic wave oscillator

Abstract

The surface acoustic wave device (10) includes at least an IDT (16) serving as an electrode pattern (14) to excite a Rayleigh surface acoustic wave, to excite the upper limit mode of the surface acoustic wave stop band. The surface acoustic wave device is characterized in: the piezoelectric substrate (12) for fabricating IDT (16) is made of a quartz substrate that is cut out at a cut angle represented by an Euler angle representation (phi, theta, Psi) of (0 DEG , 95 DEG <=theta<=155 DEG , 33 DEG <=|Psi|<=46 DEG ); electrode finger grooves are formed between the electrode fingers of the comb-tooth-shaped electrode (18 (18a, 18b)) which compose the IDT (16); and electrode finger bases is the quartz portions sandwiched between the electrode finger grooves and has upper surfaces on which the electrode fingers are positioned.

Description

technical field [0001] The present invention relates to a surface acoustic wave device using an upper limit mode of the stop band of a Rayleigh wave type surface acoustic wave, and a surface acoustic wave oscillator equipped with the device. Background technique [0002] The IDT and the reflector constituting the surface acoustic wave element chip have a plurality of conductive strips, and the periodic structure of the conductive strips forms a frequency band that reflects SAW in a specific frequency range with a high reflection coefficient, that is, a stop band. [0003] In a surface acoustic wave device using an ST-cut crystal substrate having a predetermined in-plane rotation angle φ, the upper stop mode of the Rayleigh-wave surface acoustic wave can be excited, and its good frequency-temperature characteristics are known. Moreover, if two electrode fingers are provided at one wavelength of the surface acoustic wave, a good single-type IDT can be used, which is different ...

AI Technical Summary

Problems solved by technology

However, in the invention of Patent Document 1, manufacturing errors during mass production are not considered

For example, in the manufacturing process of a SAW device, when forming a resist pattern and forming an electrode pattern by wet etching, etc., it is affected by the difference in the thickness and width of the resist pattern, and side etching in which etching is performed from the side of the electrode pattern. , the line width of the electrode fingers that make up the IDT sometimes produces errors

When forming an electrode pattern by dry etching, the variation in line width of electrode fingers due to side etching is reduced, but variation in line width of electrode fingers occurs due to variation in thickness and width of the resist pattern as in wet etching

[0009] In addition, in the surface acoustic wave device disclosed in Patent Document 1 using a crystal substrate having an in-plane rotation angle, when the line occupancy ratio η between individuals varies due to manufacturing errors or the like, the amount of frequency fluctuation when the temperature changes is large. Variety

That is, the deviation of the frequency temperature characteristic increases

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