Surface acoustic wave device of multilayer film structure and preparation method thereof

Abstract

A surface acoustic wave device of a multilayer film structure comprises a CVD diamond film, an a-AlN film of axle a preferred orientation, a c-BN film of axle c preferred orientation and an interdigital transducer (IDT) in a successive superposition mode to form a diamond-complex film structure, wherein the thickness of the CVD diamond film is 20-25 micrometers, the thickness of the a-AlN film is 300-500nm, the thickness of the c-BN film is 300-500nm, the thickness of the IDT is 100nm, and the IDT is an aluminium film. The surface acoustic wave device of the multilayer film structure has the advantages that hardness and sound velocity of the diamond are high, high sound velocity of the a-AlN can effectively relieve a sound velocity frequency dispersion effect caused by big difference of the sound velocity between the diamond and the c-BN and a high electromechanical coupling coefficient of the c-BN. The surface acoustic wave device of the multilayer film structure can be used for manufacturing surface acoustic wave (SAW) devices which are high in frequency, high in sound velocity, high in power and high in electromechanical coupling coefficients.

Description

technical field [0001] The invention relates to the technical field of surface acoustic wave devices, in particular to a surface acoustic wave device with a multilayer film structure and a preparation method thereof. Background technique [0002] In recent years, high-frequency SAW filters have been widely used in intermediate frequency (IF) filtering of 3G digital mobile communication high-frequency systems. However, with the increasing shortage of radio communication frequency band resources, the frequency band below 2.5 GHz has been fully occupied, and only high-power and miniaturized surface acoustic wave (SAW) devices operating in the high-frequency band (2.5-10 GHz) can meet the needs of mobile communication systems. and bandwidth requirements of optical communication systems. Therefore, the development of high frequency (above 2.5GHz) SAW filters is imminent. [0003] However, for conventional SAW materials such as quartz, zinc oxide, and lithium niobate, the phase ...

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Problems solved by technology

[0003] However, for conventional SAW materials such as quartz, zinc oxide, and lithium niobate, the surface velocity of the surface acoustic wave is low, and both are lower than 4000m / s. The finger width d of the finger transducer (IDT) must be less than 0.4um. If the center frequency is increased to 5GHz, the IDT finger width d corresponding to the surface acoustic wave device must be less than 0.2um, which is no different from the current semiconductor industry level. It is a great challenge, and with the reduction of the IDT finger width d, various problems such as severe finger breakage, poor reliability, low yield, and high price will be encountered in production, which seriously restricts the further development of the frequency of SAW devices. improve

At the same time, the reduction of IDT finger width will increase its resistance and generate a lot of heat. If the heat cannot be dissipated, the power that the device can withstand will be reduced. Therefore, devices made of conventional surface acoustic wave device materials cannot meet the requirements. Modern SAW devices with high frequency, high power and high electromechanical coupling coefficient

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