Design, development and reliability testing of a low power bridge-type micromachined hotplate

• Development and reliability of a platinum-based microheater with low power consumption.
• The microhotplate consumes only 11.8 mW when heated up to 400 °C.
• Reliability testing of hotplate was performed at higher temperatures. At temperatures, 404 °C, 508 °C and 595 °C, the microhotplate continuously operated up to 16.5 h, 4.3 h and 4 min respectively without degrading its performance.
• Pulse-mode of operation, maximum current capability and vibrational testing of fabricated microhotplate were performed.

In this paper, the development and reliability of a platinum-based microheater with low power consumption are demonstrated. The microheater is fabricated on a thin SiO2 bridge-type suspended membrane supported by four arms. The structure consists of a 0.6 μm-thick SiO2 membrane of size 50 μm × 50 μm over which a platinum resistor is laid out. The simulation of the structure was carried out using MEMS-CAD Tool COVENTORWARE. The platinum resistor of 31.0 Ω is fabricated on SiO2 membrane using lift-off technique. The bulk micromachining technique is used to create the suspended SiO2 membrane. The temperature coefficient of resistance (TCR) of platinum used for temperature estimation of the hotplate is measured and found to be 2.2 × 10−3/°C. The test results indicate that the microhotplate consumes only 11.8 mW when heated up to 400 °C. For reliability testing, the hotplate is continuously operated at higher temperatures. It was found that at 404 °C, 508 °C and 595 °C, the microhotplate continuously operated up to 16.5 h, 4.3 h and 4 min respectively without degrading its performance. It can sustain at least 53 cycles pulse-mode of operation at 540 °C with ultra-low resistance and temperature drifts. The structure has maximum current capability of 19.06 mA and it can also sustain the ultrasonic vibration at least for 30 min without any damage.