Project: Ultra high frequency Surface Acoustic Wave devices for sensors and tele/radio/space communication

Background:_x000D_Surface acoustic wave (SAW) devices are used in numerous electronic systems such as mobile phones, GPS, and WiFi. Furthermore, recent research has shown their industrial potential for wireless sensor applications. These devices can be remotely interrogated for measuring various physical parameters, without the need for a dedicated power source (passive sensing). However, a key requirement for achieving industrial success is the development of calibration-free SAW devices. For this purpose, increased accuracy at the nanometre level is required in their fabrication. It will be ideal for end-users to be able to replace SAW sensors without the need for any system updating, especially in the case of resonator-based systems which operate in the ISM bands at 434, 866 (EC market) or 915 MHz (US market). Another major advantage of SAW based sensors is the possibility to have individual sensor identification. But this requires the technology to address high frequency ISM bands. New designs are capable of withstanding ISM regulation and to manage sensor collision issues, for instance using ultra-wide band operation or advanced signal processing techniques. The operating frequencies extend from 2.45 to 6 GHz (UHF), imposing challenging conditions for reliable SAW device fabrication. Due to the limited resolution of affordable optical lithography techniques, the fabrication dispersion for a given frequency is roughly 100 ppm at best and is at present a major technological barrier. New lithography techniques are needed which can realize cost effective sub 100nm lithography._x000D__x000D_Goal:_x000D_The CO goal is to develop high quality SAW resonators at intermediate frequencies (400-900 MHz) for wireless sensors operating in narrow-bandwidth ISM bands with ultimate reproducibility. Secondly, we will fabricate devices operating at UHF- bands (2.45 to 6 GHz) allowing for identifiable sensor applications. The development of these devices will be achieved using nano imprint lithography (NIL) which will enable cost-effective nanofabrication of SAW devices. The success criterion for this project is to reach a minimum Q factor of 12000 at 434 MHz (6000 at 866 MHz) and a frequency dispersion of less than 50 ppm. The target for NIL will be to achieve a 3sigma electrode CD variation below 10 nm. This requires development of reliable production of high-end NIL templates as well as stable NIL processing schemes. Although the CO result of the project will be the accurate fabrication of UHF SAW sensors, the efforts will also lead to filter and high stability source applications in telecommunications, radio communication and radar applications._x000D__x000D_Technical Objective:_x000D_In order to achieve this goal, we will model, design, fabricate and characterize UHF SAW devices. Such devices cannot be fabricated using conventional SAW industry technologies due to inherent high demands on lithography resolution. Another factor is the high cost related to the required nanolithography process. A key technological objective will be to establish a production scheme for NIL-templates as well as NIL processes. The NIL technology will circumvent the major technological barrier related to production and will enable cost effective production of UHF SAW resonators having unprecedented performance. This will constitute a fundamental technological leap for the European SAW industry. _x000D__x000D_Market Objective:_x000D_The project will open up the market for calibration-free sensors for industrial metrology and low cost wireless monitoring systems as well as advanced identifiable sensors operating at 2.45, 5.8 GHz, and more. A calibration-free SAW solution has numerous applications such as domotics, medical, automotive and general industrial metrology. The European sensor market for industrial applications was estimated at 2.6 Billion Euros in 2007 (Decision Conseil, April 2008), with a CAGR over the period 2007-2011 at 7%. This market segment is the largest in terms of sensor consumption, representing 26% of the European market. A conservative estimate is that for the first two years after completion of the project, 2.6 Million Euros would be gained (based on a 1% wireless sensor market share). NILT will develop a NIL-template production scheme that ensures production lead times as low as four weeks. It is estimated that this will give a 10% market share within 1-2 years and an annual turnover of 1.5 Million Euros._x000D__x000D_Consortium:_x000D_The consortium comprises of SENSeOR (France) acting as CO participant, followed by ARE (France), FEMTO-ST (France), GVR (Switzerland), NILT (Denmark), and DTI (Denmark). Hence, the consortium is defined by three SMEs and one institute active in high-end SAW development as well as one SME and one institute active in NIL development. The majority of the Ps have successfully collaborated together in an EC funded research project (SAWHOT).

Acronym NILSAW (Reference Number: 6785)
Duration 01/05/2012 - 30/06/2014
Project Topic The project aims to use novel nano imprint lithography (NIL) processes to develop and produce ultra-high frequency surface acoustic wave (SAW) devices, which will enable cost-effective industrial production of a new class of calibration-free SAW sensors having unprecedented performance
Project Results
(after finalisation)
The results compared to the CO goal are as follows:_x000D_(1) goal: High Quality SAW resonators at intermediate frequencies (400-900 MHz) for sensor applications (dispersion better than 20 kHz), achievement: This goal has not been achieved due to the fact that the frequency dispersion is dependent on both the lateral feature size as well as the thickness of the metal IDT structures. Even though the lateral feature size tolerance was improved considerable, better than anticipated, the metal thickness variations were not improved and thus the final frequency dispersion was not improve compared to state-of-the-art._x000D__x000D_(2) Goal: Fabricate devices in the UHF band (2.45 to 6 GHz) for id-tag and sensing, achievement: This goal was achieved and opens new possibilities for manufacturing UHT band SAW components. SAW id-tags at 3 and 6 GHz have been fabricated and tested using nanoimprint lithography. _x000D__x000D_(3) Goal: Frequency dispersions less than 50 ppm for filter and oscillator applications (ARE), achievement: This goal was not achieved due to the same reason as goal (1). The metalization process needs to be optimized in order to achieve these goals and was not performed in the scope of this project. _x000D__x000D_(4) Goal: Develop cost effective manufacturing through J-FIL technology with 90% yield and line-width variations less than 10nm, achievement: The yield of the J-FIL technology was found to be very dependent on the substrate. In some cases the yield can be above 90%, however for most of the quartz and LiNb cuts that where used, the yield was must less than 50%, due to large flatness variations of the substrates. This was not anticipated at the beginning of the project and steps need to be taken in order to solve this, through collaboration with wafer manufacturing and surface polishing industry. Lateral line width variations for the SAW components fabricated through J-FIL process, where reduced to below 5nm, which is better than the set goal. _x000D__x000D_(5) Goal: Develop systematic and automatic SAW testing/probing station, achievement: This was achieved by consortium P FEMTO-ST and was used to characterize the batches of SAW components fabricated throughout the project. _x000D__x000D_(6) Goal: Develop reliable production of J-FIL template (NILT) with a 4-6 weeks fabrication time, achievement: The fabrication process has been developed for both a positive and negative J-FIL template. The trench process is stable and can has a fabrication time below 4week, however the protrusion process has challenges with reproducibility, with respect to the lift-off procedure. When the protrusion process can be improved the expected fabrication time is also below 4 weeks. _x000D__x000D_(7) Goal: 8 publications within the NILSAW project, achievement: despite the difficulty to achieve large amounts of SAW components over 8 publications where achieved based on the NILSAW results._x000D_
Network Eurostars
Call Eurostars Cut-Off 7

Project partner

Number Name Role Country
6 GVR Trade Partner Switzerland
6 NIL Technology Aps Partner Denmark
6 SENSeOR Coordinator France
6 FEMTO-ST, CNRS Partner France
6 Danish Technological Institute Partner Denmark
6 AR Electronique Partner France