Temperature compensated radio-frequency harmonic bulk acoustic resonators

Abstract

In this work, we propose a compensated temperature pressure sensor fabricated on compound LiNbO 3 /Quartz/Quartz substrates obtained by Au/Au bonding at room temperature and double face lapping/polishing of LiNbO 3 /Quartz stack and a final gold bonding with a structured Quartz wafer. This paper shows the possibility to obtain device which is intrinsically low sensitive to thermal effects, and even allowing a second order compensation thanks to the Quartz thermal stability Sensitivity of the final sensor to bending moments then is tested and results show pressure sensitivity of such devices.

High-Overtone Bulk Acoustic Resonator

“…Figure 18 shows the temperature dependence for different configuration of HBAR devices constituted by LiNbO3 and Quartz layers with different cut orientations. This work shows clearly that the choice of materials and the cut orientation of these materials have a direct impact on the frequency shift with temperature variations [26]. Moreover, the frequency dependence on temperature is different for each overtone of HBAR devices.…”

“…Nevertheless, some works show the possibility to have an intrinsic compensation of the temperature for HBAR devices [8], [26]. Figure 18 shows the temperature dependence for different configuration of HBAR devices constituted by LiNbO3 and Quartz layers with different cut orientations.…”

High-Q and low TCF HBAR based on LiTaO<inf>3</inf> substrate

“…However, the targeted performances of an ideal HBAR are a high resonance frequency (higher than 1 GHz), a temperature coefficient of frequency (TCF) less than 10 ppm over a wide range of temperature around a turnover temperature, and a Q.f product higher than 5×10 13 Hz. The goal of this paper is to present a new HBAR device stack, based on a thinned LiNbO 3 piezoelectric layer transferred on a LiTaO 3 substrate, satisfying these specifications and to compare its performances with the previous works which present low TCF [5] or high quality factor [6]. Firstly, we discuss the choice of materials to reach to these performances (high quality factor, low TCF).…”

“…This work presents the later approach with HBAR devices. Such resonators combine operation at gigahertz frequencies, thanks to the use of a thin piezoelectric film, with the high quality factors brought by low propagation losses in a bulk substrate such as Quartz [5] or Sapphire [6]. Increasing quality factor is a key aspect to decrease Leeson's frequency.…”

A 4.596 GHz frequency synthesis based on a solid-mounted resonator

“…A great issue in such oscillators is their high thermal frequency sensitivity. Several solutions were proposed to reduce the frequency-temperature dependence of FBAR [6], [7] and HBAR [8]. This paper presents an original SMR oscillator-based 4.596 GHz frequency synthesis.…”