A novel selective growth of nanowire on CMOS MEMS compatible gas sensor

Abstract

In this paper, we proposed a new sensing mechanism which the sensing structure with zinc oxide (ZnO) nanowires to increase sensitivity. The ZnO nanowires are grown selectively on top of the sensing membrane with proposed ring-type electrodes which is implemented using 0.35μm CMOS MEMS process. The ZnO nanowire is achieved by chemical bath deposition (CBD) method with several prepared solutions, zinc acetate dihydrate and hexamethylenetetramine mixed at Zn(CH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> COO) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ·2H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O · C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> =1:1, the others is zinc nitrate hexahydrate and hexamethylenetetramine mixed at Zn(NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> × 6H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O : C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> =5:1. The growth of nanowires reveals a novel selective deposition on the metal layers of sensing area other than the passivation of Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> which means a high specific definition of sensing region beyond the conventional sol-gel method. The research on selective growth of nanowire benefits the deposition of sensing material on certain active regions beyond the drawback of conventional sol-gel deposition. The advantages of the sensor are low cost and suitable for industrial production.