1 1.Introduction 2.Market production of gas sensors 3.Development of resistance gas sensors technology 4.Influence of micromachining technology 5.Non-resistance type gas sensors 6.Measurement modules Gas sensors

2 Introduction Main fields of gas sensors applications : safety control (combustible and toxic gases) air quality (buildings, vehicles) process control in industry laboratory analytics burning control in vehicle engines Only in analytics and in industry one uses expensive gas analysers. In other cases there is a need of cheap, small size and easy in application gas sensors.

3 Market production Gas sensors manufactured by Figaro Eng. Inc.

4 Market production Lambda sensor

5 First reports: gas sensing properties of Ge: W.H.Brattain, J.Bardeen, Bell Syst. Tech. J. (1952) First reports on gas sensing properties of metal oxides: G. Heiland, Z. Physik (1954) A. Bielański, J. Dereń, J. Haber, Nature (1957) T. Seiyama et al., Anal. Chem. (1962) N. Taguchi – gas sensors as a commercial product (TGS sensors), production at the end of Gas sensors – historical review The dominating technology at present: deposition of thick films onto ceramic substrates. One observes increasing role of micromachining technology combined with technology of gas sensitive thin films. The most frequently used gas sensitive oxide layers: SnO 2, ZnO, TiO 2, WO 3, In 2 O 3.

6 Understanding resistance gas sensor (a), (c) (b), (d) Jonosorption reaction with a capture of electron: Reduction of oxygen ion: Change in conductance:

7 Structure of monocrystalline sensor: 1 – alumina substrate, 2 – platinum electrodes, 3 – conducting paste, 4 – crystalline ZnO, 5 – heater (screen printing), 6 – leads Development of gas sensors technology, monocrystals

8 Sintered semiconductor powder with appropriate catalytic admixtures and a binder TGS 203 sensor for CO detection R H = 1.9 Ω V H = 0.8 V V C = 12V P H = 2 x 370 mW Development of gas sensors technology, sintered structures

9 FIS microsensor SB series: (a) structure, (b) basic measurement circuit. Termination „1” is common for the heater voltage V H and the sensor voltage V C. Due to miniaturisation the consumed power does not exceed 130 mW. The sensor is used for detection of methane, propane and other inflammable and toxic gases. Development of gas sensors technology

10 Figaro TGS 800 series Structure of the sensor: layer of SnO 2 with a thickness of ca. 50 μm, alumina tube (inner diam. 1 mm, length ca. 4.2 mm), Pt wire leads (Φ = 0,08 mm), platinum heater (30 Ω), required working temp. ca. 300 o C, power of the heater ca. 830 mW. Development of gas sensors technology Basic measurement circuit

11 FIS sensor SP series working in a pulse modulated temperature regime. Advanced thick film technology, Au contacts, RuO or Pt heater, power consumption 300 – 400 mW. Thick films

12 Figaro sensor TGS 2400 series for detection of toxic gaes One-side configuration, power consumption 14 mW (avg value) Pulse control, power supply V C =V H = 5V Thick films

13 (b) suspended membrane ( hotplate type) (a) closed membrane Influence of micromechining technology

14 Influence of micromechining technology Sensor in a package Sensors layout Motorola MGS 1100 sensor for CO detection

15 Micromachined sensors manufactured in cooperation ITE Warsaw - AGH Schematic of the resitance – type gas sensor on the silicon membrane Power consumption below 100 mW

16 3” Si wafer with manufactured sensors Single sensor die, upper view Micromachined sensors manufactured in cooperation ITE Warsaw – AGH, cont.

17 Micromachined gas sensor in TO-5 encapsulation without a cap with a cap and a steel protecting mesh Micromachined sensors manufactured in cooperation ITE Warsaw – AGH, cont.