Funding type: COFUND Marie Slodowska Curie Action
This project is under the Marie Skłodowska-Curie Actions (MSCA) program. There are no nationality conditions but the candidates must fulfill the MSCA mobility conditions, which means that she/he must not have stayed more than 1 year in France during the last 3 years immediately before the call deadline (31/05/2019)

Expected start date: 01/10/2019

Contacts:
Ass. Prof. Bertrand VILQUIN
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+33 4 72 18 62 54

Pr. Jian Zhen OU, RMIT
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websites:

• https://www.rmit.edu.au/about/our-locations-and-facilities/facilities/research-facilities/micronano-research-facility
• http://inl.cnrs.fr/en/

Collaborations/External partners :

STMicroelectronics

Domain and scientific context :

The development of an ion-sensitive semiconductor device that combines the principles of a MOS transistor and a glass reference electrode was proposed by Bergveld in 1970 [Bergveld 70]. Commonly called ISFET, this device measures ionic activities in electrochemical or biological environments. The ISFET type pH sensors have a sensitive dielectric layer on which the electrolyte will be deposited. Several dielectrics can be used: SiO2, Si3N4, Al2O3, SnO2, Ta2O5 [Matsuo 81]. This type of sensor used for 30 years since the first demonstration of ISFET has a maximum sensitivity limited to ambient temperature of 59.6 mV / pH. More recently, different approaches have demonstrated increased sensitivities that exceed this limit, called the Nernst limit. Parizi reached 130 mV / pH with a circuit comprising two sensors, each with a field effect transistor and an enlarged sensitive grating [Parizi 12]. They achieved these performances by capacitively coupling a floating gate of a MOSFET with an ion sensitive gate which is remote from the gate of the transistor. Even greater sensitivities were also achieved using double grid ISFETs: Jang used a dual ultra-thin body (UTB) grid to reach 426 mV / pH [Jang 14], while Huang reached 453 mV / pH using the best electrostatic control of the channel with both grids [Huang 15].

Figure 1. Overview of cross-platform sensors based on FDSOI technology and BEOL integration of sensitive grids for gas sensors, and other sensors.

In the case of an FDSOI sensor, a change in voltage, or its equivalent load, on the active gate will cause a significant variation in the threshold voltage of the rear gate given the strong capacitive coupling of the two gates. The change in surface potential will be amplified by a factor which is proportional to the capacity ratios of the back gate with its buried oxide and the active gate with its very fine gate oxide [Spijkman 11].

As a result, the integration of a sensitive grid into the BEOL of an FDSOI technology will make it possible to obtain highly sensitive ultra-sensitive ISFET sensors that can be used for: i) pH measurements (water, sweat, ...), but also ii) nucleic acid measurements or enzymes for ultra-sensitive biological sensors, and finally modifying sensitive layer materials and sensor architecture iii) gas measurements. Preliminary work has already yielded promising results for a hydrogen sensor [Ayadi 16, Ayadi 17] and a pH sensor with a record sensitivity of 475 mV / pH [Ayele 17]. The transduction principle for gas sensor applications is very similar to that of ISFETS described above. The review article [Chiu 13] illustrates the integration of a sensor network with an electronic data processing system. This compact system operates as an "electronic nose" very low consumption. Conductive polymers are used as sensitive layers to reduce measurement temperatures and manufacturing costs. The integration of polymer-based sensitive materials on a 0.35μm CMOS circuit recently [Lee 14] allowed the realization of a network of sensors allowing the detection at 27 ° C of several gases: CO2, NO, CO, BTX and humidity. This work by the National Taiwan University and Intel Lab, Hillsborog have demonstrated a complete system with a total consumption of 400 μW. The main energy constraint for sensor applications for IoT is the lowering of the operating temperature to reduce system consumption. The consumption of the systems is of course related to the temperature of the measurement but especially to the regeneration of the sensors which requires a heating step for degassing. The sensors made at Michigan State University consume 3.2 μW [Li 14]. The overall consumption of the systems is due to the microcontroller and the heating resistance.

In this project we propose integrated sensitive grids FDSOI chips. The advantage of these devices is the fact of having excellent electrostatic control and being able to modulate the threshold voltage for a very low energy cost [Skotnicki 15]. This makes this type of sensor relevant to the Internet of Things (IoT) market where energy consumption and cost are critical.

Keywords : gas sensor; pH sensor; CMOS; functional oxide

Objectives :

The overall objective of this sub-axis is to manufacture a low-power multi-platform integrated sensor system comprising the various sensors as well as the read-out circuit (s) for gas detection. To meet this need, several technological bricks will be developed: a pH sensor of the ISFET type (ion sensitive field effect transisor) on FDSOI with good sensitivity performance, a hydrogen sensor as a demonstrator and subsequently CO sensors, NOx and BTX based on the same capacitive coupling principle, and finally the associated read-out circuit (s).
We will build on our previous studies of hydrogen detection with platinum layers to make prototypes of hydrogen sensors incorporating the heater resistance. We can then evaluate the consumption of the sensors according to the operating temperatures. In order to be able to test the sensors quickly, an external read-out circuit will be used. In a second step, we plan to integrate the read-out circuit in a system-on-a-chip. The design could be that of an analog block with a linear amplifier trans-impedance gain adjustable. A multiplexer may also be implemented at the end of the program to the read-out circuit in a multi-gas detection optics (CO, NOx, BTX).

Scientific challenges :

The transduction principle for gas sensor applications is very similar to that of ISFETS described above. The review article [Chiu 13] illustrates the integration of a sensor network with an electronic data processing system. This compact system operates as an "electronic nose" very low consumption. Conductive polymers are used as sensitive layers to reduce measurement temperatures and manufacturing costs. The integration of polymer-based sensitive materials on a 0.35μm CMOS circuit recently [Lee 14] allowed the realization of a network of sensors allowing the detection at 27 ° C of several gases: CO2, NO, CO, BTX and humidity. This work by the National Taiwan University and Intel Lab, Hillsborog have demonstrated a complete system with a total consumption of 400 μW. The main energy constraint for sensor applications for IoT is the lowering of the operating temperature to reduce system consumption. The consumption of the systems is of course related to the temperature of the measurement but especially to the regeneration of the sensors which requires a heating step for degassing. The sensors made at Michigan State University consume 3.2 μW [Li 14]. The overall consumption of the systems is due to the microcontroller and the heating resistance. The proposed works will initially focus on the selection of sensitive materials, particularly for the measurement of air quality. The studies will focus on SnO2, TiO2, WO3 materials for the detection of COx and NOx. CO sensors present the main challenge of our work because detection is generally well above 350 ° C [Udrea 01]. We therefore propose a study to lower the measurement temperatures by incorporating catalysts (platinum or palladium) as already demonstrated with CO detection at 35 ° C [Lamp 05].

Expected original contributions :

• Realization of a sensor embledded on CMOS (with respect of the low thermal budget)
• Operation at low temperature (if possible at room temperature)
• Low power consummation (<1µW)
• Limit of detection (LoD) of 100ppm
• Response time about 50s.

Research program and methodology :

Main goals

• Year 1    Functional oxides growth and characterizations with respect of BEOL thermal budget
• Year 2    Testing the layers in different gas atmosphere (CO, NOx, etc.)
• Year 3    Fabrication and characterizaitons of the read-out circuit

Integration of mono-sensors on FET structure with high sensibility

Scientific supervision:

• Description of the supervision committee :

• Integration inside the laboratories (percentage of working time inside these laboratories) : 67% at INL, 33% at RMIT

PhD funding : Co-Fund Marie Sladowska Curie Action (MSCA) ECL/RMIT (ECLAUsion program)

Profile of the candidate :

The candidate should have a good knowledge and a solid background in the field of Physics; Electronic Engineering; Material Science and Engineering. S/he should work towards his/her Masters/honours or Engineering degree in a field apposite to one of these areas. An experience in clean-room fabrication, material deposition or electronic characterization will be strongly appreciated.

Objectives for the valorization of the research work :

The results obtained can be valorized through communications in the field of materials science (Advanced Materials, ACS Nano ...), and nano-electronic & sensors devices (IEEE, AIP, Elsevier ...). Furthermore, dissemination of the work at international conferences dedicated to materials and devices for neuromorphic engineering will also be carried out (eMRS, IEEE-ESSDERC, IEEE-IMW, ...). The targeted valorisation objectives are from 2 to 5 peer-reviewed international journals and at least 3 papers in international conferences.

Skills that will be developed during the PhD :

The candidate will be trained in the fabrication of crystalline materials in the form of thin layers. He / She will also receive training in clean room steps for the realization of simple electrodes and devices. His working environment will allow him to acquire knowledge in electrical characterization of materials (current - voltage, capacitance - voltage measurements). He / she will be integrated into the international nanoelectronics and sensors communities, the national functional oxide community (OXYFUN) and the international functional oxide thin film scientific community.

Professional opportunities after the PhD:

The training and formation received during the thesis will allow the PhD student to apply for an academic position in all the laboratories involved in this field or to seek a private job in research and development departments of large companies that take advantage of this type of materials (Thales , STM, IBM ...).

Bibliographic references about the PhD topic :

• [Bergveld 70] P. Bergveld, "Development of an ion-sensitive solid-state device for neurophysiological measurements," IEEE Transactions on Biomedical Engineering 1 (1970): 70-71.
• [Matsuo 81] H. Abe, M. Esashi, and T. Matsuo, “ISFET’s using inorganic gate thin films,” IEEE Trans. Electron Devices, vol. 26, no. 12, pp. 1939–1944, Dec. 1979.
• [Parizi 12] K. B. Parizi, A. J. Yeh, A. S. Y. Poon, and H. S. P. Wong, “Exceeding Nernst limit (59mV/pH): CMOS-based pH sensor for autonomous applications,” in 2012 International Electron Devices Meeting, 2012, p. 24.7.1-24.7.4.
• [Jang 14] H. J. Jang, and W. J. Cho, “Performance enhancement of capacitive-coupling dual-gate ion-sensitive field-effect transistor in ultra-thin-body,” Dep. Electron. Mat. Eng., Kwangwoon Univ., Seoul 139-701, Rep. Korea, Jun. 13, 2014.
• [Huang 15] Y. J. Huang, C. C. Lin, J. C. Huang, C. H. Hsieh, C. H. Wen, T. T. Chen, L. S. Jeng, C. K. Yang, J. H. Yang, F. Tsui, Y. S. Liu, S. Liu and M. Chen, “High performance dual-gate ISFET with non-ideal effect reduction schemes in a SOI-CMOS bioelectrical SoC,” Presented at Electron Devices Meeting (IEDM), IEEE (Dec, 2015).
• [Skotnicki 15] T. Skotnicki, & S. Monfray, “UTBB FDSOI: Evolution and opportunities,” In Solid State Device Research Conference (ESSDERC), (2015) 45th European (pp. 76-79), IEEE.
• [Spijkman 11] Spijkman, M., E. C. P. Smits, J. F. M. Cillessen, F. Biscarini, P. W. M. Blom, and D. M. De Leeuw, "Beyond the Nernst-limit with dual-gate ZnO ion-sensitive field-effect transistors," Applied Physics Letters 98, no. 4 (2011): 043502.
• [Chiu 13] Shih-Wen Chiu and Kea-Tiong Tang, Towards a Chemiresistive Sensor-Integrated Electronic Nose: A Review,  Sensors 2013, 13, 14214-14247; doi:10.3390/s131014214
• [Lee 14] Chang-Hung Lee, Wen-Yu Chuang, Melissa A. Cowan, Wen-Jung Wu and Chih-Ting Lin, A Low-Power Integrated Humidity CMOS Sensor by Printing-on-Chip Technology, Sensors 2014, 14, 9247-9255; doi:10.3390/s140509247
• [Li 14] Haitao Li, Xiaoyi Mu, Yuning Yang, Mason, A.J., Low Power Multimode Electrochemical Gas Sensor Array System for Wearable Health and Safety Monitoring, Sensors Journal, IEEE, vol. 14, p 3391 – 3399, 2014
• [Udrea 01] F. Udrea and J.W. Gardner, SOI CMOS gas sensors, Sensors and Actuators B – Chemical, 78 2001,  180-190
• [Lampe 05] U. Lampe, E. Simon, R. Pohle, M. Fleischer, H. Meixner, H.-P. Frerichs, M. Lehmannb, G. Kiss, GasFET for the detection of reducing gases, Sensors and Actuators B 111–112 (2005) 106–110