Ultra temperature-stable bulk-acoustic-wave resonators with SiO2 compensation layer

Area of Science:

• Materials Science
• Electrical Engineering
• Physics

Background:

• Bulk acoustic-wave resonators (BAR) are crucial for frequency control applications.
• Conventional BARs suffer from significant temperature-dependent frequency drift.
• Achieving high temperature stability is essential for advanced electronic systems.

Purpose of the Study:

• To develop temperature-compensated bulk acoustic-wave resonators (BAR).
• To achieve a temperature coefficient of frequency (TCF) below 1 ppm/°C.
• To explore the use of silicon dioxide's unique positive TCF for compensation.

Main Methods:

• Investigated two types of resonators: film bulk acoustic resonators (FBAR) and high-overtone acoustic resonators (HBAR).
• FBARs utilized an Al/ZnO/Al/SiO2 stack on a surface-micromachined cantilever released by XeF2 vapor etching.
• HBARs employed an Al/ZnO/Al resonator on a bulk-micromachined SiO2/Si/SiO2 substrate.

Main Results:

• Demonstrated temperature-compensated BARs with TCF < 1 ppm/°C at frequencies above 3 GHz.
• Successfully leveraged the positive TCF of silicon dioxide to counteract negative TCFs of other materials.
• Both FBAR and HBAR designs exhibited excellent temperature stability.

Conclusions:

• The proposed design effectively compensates for temperature-induced frequency variations in BARs.
• Silicon dioxide's unique properties enable high-performance, temperature-stable acoustic resonators.
• These resonators are suitable for applications demanding precise frequency control over a wide temperature range.