A Vertical Micromachined Resistive Heater for a Micro Gas Separation Column

Abstract

Abstract This paper presents a micromachined vertical resistive heater fabricated as part of a micro-gas separation column. The complete device is formed from two silicon die electrostatically bonded to a single glass die. The glass die is conventionally machined and contains four through holes. The holes are filled with a zeolite adsorbent and thus act as separation columns. Each silicon die serves as a screen which allows air to flow through the device while holding the zeolite in place. The 5000 μm diameter screens are deep reactive ion-etched (DRIE) and contain 1964 square 50 μm ×50 μm ×350 μm channels. A junction isolated vertical resistor is integrated into one of the silicon die by performing a phosphorus diffusion after DRIE. Thus, the resistor is embedded into the walls of the micromachined silicon screen. The vertical resistor is used to heat a purge gas and regenerate the zeolite adsorbent. The measured vertical resistance is between 6 and 7 Ω. The residence time of the gas in the heater is ∼60 ms assuming a 1 sccm N2 gas flow rate. The theoretical heat transfer coefficient is 3000 W/m2/°C. The power consumed to heat both the screen and the gas at steady state is ∼33 mW per die.