Vol. 103, Issue 4, April 2009, pp.44-51

Design and Development of Polysilicon-based Microhotplate for Gas Sensing Application

Mahanth PRASAD, V. K. KHANNA and Ram Gopal

MEMS Laboratory, Central Electronics Engineering Research Institute (CEERI)/Council of Scientific and Industrial Research (CSIR), Pilani-333031 (Rajasthan), India

Tel.: +91-1596-252332, fax: +91-1596-242294

E-mail: mahanth.prasad@gmail.com

Received: 25 January 2009   /Accepted: 20 April 2009   /Published: 27 April 2009

Abstract: The paper presents the design and development of a polysilicon-based microhotplate (MHP) on a SiO₂ membrane formed by bulk micromachining in <100> orientation P-type silicon. The chip comprises four microheater cells, which can be used separately or in series combination. The chip size is 2.1 × 2.1 sq. mm. The design and simulation of a single-cell microhotplate is carried out using ANSYS. The complete fabrication process is described in this paper. The temperature coefficient of resistance (TCR) of polysilicon resistors of values 5.7 kW and 3.36 kW has been measured as 0.69 × 10^-3 and 0.5 × 10^-3 per °C respectively. These values are used to estimate the temperature of the polysilicon heater by measuring the change in resistance value of the resistor on applying a voltage to it. Temperatures up to 367 °C have been calculated at low bias voltages. As the sensitivity of the gas sensing film is temperature dependent, the developed hotplate will be used as a platform for fabricating the gas sensors.

Keywords: Polysilicon heater, Bulk micromachining, MHP, Gas sensor, TCR

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