4H-SiC for High Overtone Bulk Acoustic Resonator (HBAR)

4H-SiC for High Overtone Bulk Acoustic Resonator (HBAR)

High-overtone bulk acoustic resonator (HBAR) combines the advantages of surface acoustic wave (SAW) and bulk acoustic wave (BAW) resonators, providing high Q values, stable frequency operating range, and low frequency jitter noise, which can meet the needs of highly stable microwave signals. In addition, high-overtone bulk acoustic wave resonator also has high driving capability, suitable for stable operation at short and high frequencies. PAM-XIAMEN can provide semi-insulated 4H-SiC substrate to study the achievable Q factor of the HBAR. The specific wafer information please refer to the table below:

SiC Bulk Acoustic Resonator Wafer

1. 4H-SiC Substrate for HBAR Fabrication


Item 4H-SiC Substrate
Type/Dopant Semi-insulating
Orientation <0001>+/-0.5 °
Thickness 350 ± 25 um
MPD <15 cm-2
Resistivity ≥1E5 Ω·cm
Surface Process DSP//Si face epi-ready with CMP
Surface Roughness <0.5 nm 


2. What Is A High Overtone Bulk Acoustic Resonator?

High overtone Bulk Acoustic Resonator is a device composed of a substrate, piezoelectric thin film, and upper and lower electrodes, which has high quality factor Q and multimode resonance spectrum characteristics.

So far, there have been many studies on growing piezoelectric thin films on supporting substrates with bottom electrodes to prepare “sandwich” structure HBAR devices, such as aluminum nitride or zinc oxide thin films on silicon or sapphire substrates. The piezoelectric thin film is sandwiched between two layers of electrodes as a transducer to excite and generate bulk sound waves, while the supporting substrate serves as a resonant cavity. The resonant frequency of high overtone is determined by the equivalent sound velocity and thickness of the piezoelectric thin film, while the frequency interval between high over-tone of different orders is determined by the thickness of the supporting substrate. In addition, the frequency response range of HBAR (i.e. The frequency range of high overtone of different orders that exist) is positively correlated with the electromechanical coupling coefficient (K2) of piezoelectric thin films.

3. SiC based High Overtone Bulk Acoustic Resonator Applications

HABRs have important application value in acoustooptic modulation, sensors, oscillators, and 5G multi band filters due to its ability to achieve extremely high Q values in the GHz frequency band.

The effective implementation in sensor applications has been already proven. These devices maximize the Q-factor that can be obtained using elastic waves at room temperature, resulting in a quality factor frequency product close to or slightly higher than 1014, which is an effective Q-factor of approximately 100000 at 1GHz.

For more information, please contact us email at victorchan@powerwaywafer.com and powerwaymaterial@gmail.com.

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