AVS 45th International Symposium
    Thin Films Division Monday Sessions
       Session TF-MoP

Paper TF-MoP21
Porous Polycrystalline Silicon Micro-Electronic Sensor

Monday, November 2, 1998, 5:30 pm, Room Hall A

Session: Thin Films Poster Session
Presenter: P.G. Han, The City University of Hong Kong, China
Authors: P.G. Han, The City University of Hong Kong, China
H. Wong, The City University of Hong Kong, China
M.C. Poon, The Hong Kong University of Science & Technology, China
N. Wang, The City University of Hong Kong, China
Correspondent: Click to Email
Porous Polycrystalline Silicon(PPS)-based microelectronic sensors have been explored in our laboratory. Using n-type <100> epitaxial silicon wafer as the substrate, undoped poly-Si films with thickness of 700 nm were deposited by thermal decomposition of silane gas(SiH@sub2@) in a low pressure chemical vapor deposition(LPCVD) reactor. Boron was then diffused into the samples at 950°C for 20 min to form a p-type polycrystalline silicon film. The poly-Si film was selectively anodized in HF(50%vol):C@sub2@H@sub5@OH(96%vol)=1:1 solution with Pt eletrode at a current density of 10mA/cm@super2@ for 10 min at room temperature.The sensitivity of the sensors based on this PPS has been characterized and annlyzed at different ambient pressures and temperature as well as gas species. Results show that the current increases remarkably as the pressure decreases and over two order of magnitude change has been detected when the vacuum pressure was pumped to 10@super -2@ ATM. We find that both ethanol and acetone vapors can make the current increase obviously. In acetone vapor, the device even behaves like a diode. The analysis of the electrical conduction mechanisms of the sensors in vaccum envirement and organic vapors will be conducted in this paper. In addition, since the fabrication process is simple, and the sensor characteristics are repeatable and reproducible, it can be easily integrated with the VLSI technology.