Simple Fabrication and Characterization of a Platinum Microhotplate Based on Suspended Membrane Structure

Abstract

One of the key components of a microsensor is the Micro electromechanical system (MEMS) microheater. It has a wide range of applications such as gas sensors, pressure sensors, and so on. In this study, a platinum microhotplate based on suspended membrane structure is introduced. A simple microfabrication process is adopted to form the micromachined suspended microheater. Some integrated circuit processes such as E-beam evaporation of Pt and Au, oxidation, wet etching process, and photolithography process are used to fabricate the device. As the usage of deep-reactive ion etching and low-pressure chemical vapor deposition systems are avoided, the microfabrication process of the hotplate is accessible even in laboratories with limited equipment. In order to achieve uniform temperature distribution over the active heater area and to increase the robustness of the membrane, a thin silicon island was placed underneath the dielectric membrane. Thermal and thermomechanical behaviors of this structure obtained by finite element analysis show that the designed microhotplate is relatively strong. Experimental results show that power consumption and time constant are 50 mW and 4.23 ms, respectively, for the temperature variation from 30 • C to 500 • C in the fabricated microhotplates.

Thermal Performance of Micro Hotplates with Novel Shapes Based on Single-Layer SiO2 Suspended Film

“…Figure 10 d shows the temperature distribution of design 4 under 22 V voltage, where the highest temperature was 448.6 °C and the temperature difference on the whole platform was almost within 50 °C. Compared with that of the traditional four-beam micro hotplate listed in Table 1 [ 13 , 15 ], temperature uniformity was increased by about 30–50%. The temperature profiles swept by two orthogonal straight lines on the same position of four designs are also shown in Figure 10 .…”

“…The suspended-membrane type micro hotplate has also been widely investigated, but the shape of suspended film is monotonous and there are still problems with the strength and temperature uniformity. F. Samaeifer performed complicated processes of five photolithography with four masks to fabricate the suspended-membrane micro hotplate with Si island [ 13 ]. M. Kaur developed a double spiral hotplate with non-uniform temperature distribution on the suspended platform and stress concentration at the connection between the beam and the platform [ 14 ].…”