Project ID: PN-II-PT-PCCA-2013-4-0677

Project Responsible P1: Dr. George Stan

Project Type: National

Project Program: UEFISCDI PCCA-2013

Funded by: Romanian National Authority for Scientific Research, UEFISCDI

Contractor: National Institute for Research and Development in Microtechnologies

Sub-Contractor: National Institute of Materials Physics (P1)

Project Status: Finished

Start Date:  1 July, 2014

End Date: 1 October, 2017

Project summary: 

The main objective of this project consists in the manufacturing of the first temperature sensor based on a SAW type device on AlN/Si. The sensor is based on the variation of the SAW resonance frequency vs. temperature. The sensor will be characterized “on wafer” in the 25-150°C temperature range. The sensor structures mounted on a special ceramic carrier, provided with SMA connectors and cables, will be characterized in the 5-500 K temperature range inside a cryostat. We aim to obtain a sensitivity >75 ppm/°C (on-wafer measurements) and 60 ppm/°C for measurements with conectors and cables, and for wireless data transmission, in the 23-150°C temperature range. Exploratory measurements of the sensor behavior will be performed up to 500°C. The project corresponds to the world wide effort to obtain acoustic devices operating in the gigahertz frequency range, using wide band gap semiconductors (AlN, GaN). These materials have very good piezoelectric properties. High quality GaN and AlN layers grown or deposited on Sapphire, SiC or Si substrate permits to use in the fabrication protocol nanolithography, micromachining techniques and monolithic integration. The advantage of using AlN for the SAW structure consist in the possibility to obtain a higher resonance frequency and a higher sensitivity for the sensor. The project has few objectives beyond the state of the art. The main element will be a SAW structure on AlN/Si with the resonance frequency in the 6-9 GHz range. The highest resonance frequency obtained up to now for SAW structures on AlN/Si is 5.1 GHz and was reported by the IMT and INCD-FM groups, partners in this project, using an IDT structure with digits and interdigit spacing 300 nm wide. This project requires interdigitated transducers having the digit/interdigit spacing 80-150 nm wide, a challenge due to the major dificulties of the nanolithographyic process on materials like AlN or GaN. Up to now, the narrowest lines on AlN have been reported on an AlN/Diamond based SAW structure in 2012 (200 nm). For the proposed sensor a „single resonator” structure will be developed. Compared with classical structures based on face-to-face resonators and delay lines, the single resonator structure offers few advantages: higher quality factor, lower losses and mainly, higher values for the sensitivity, as it was recently proved by IMT for GaN. Because the basic idea of the proposed sensor are measurements in hostile environmental conditions, so the information from the sensor will be transferred wireless to a reader unit; the SAW sensor is totally compatible with this operating mode. For this type of data transmission, innovative solutions will be developed, required mainly for the „single resonator” structure. Thin highly textured c-axis AlN films will be obtained. A two steps deposition process will be developed, at low temperatures for the synthesis of thin AlN films. There is a potential advantage of of monolithic integration of the SAW based AlN temperature sensor in a CMOS ICs. AlN technology is CMOS compatible, due to its low deposition temperature. In such circuits fabrication protocols contain nanolithographic process, therefore these processes for the sensor will not add significant costs. The project consortium consists in four teams with excellent expertise and complementarities in the project topics. The IMT team has many contributions in the state of the art for acoustic devices on GaN and AlN, in nanolithography and microwave characterisation. INCD-FM has an excellent expertise in high quality AlN films deposition. UPB has excellence expertise in design and modelling of high frequency devices and circuits. ROMQUARZ is the only Romanian enterprise with an authentic experience in SAW type devices manufacturing on classical piezoelectric materials. They have been involved in SAW devices manufacturing on non-semiconductor materials (quartz, lithium niobate, etc) in the last 20 years.