Properties of SiO₂electret films charged by ion implantation for MEMS-based energy harvesting systems

Abstract

This paper presents the results of charging SiO 2 thin film electret by ion implantation. A maximum charge density of 16 mC m −2 has been shown using 500 nm thermal oxide. Charge is reproducible and stable in time. Two types of ions were used for ion implantation: phosphorus (P + ) and boron (B + ). Directly after implantation, it was found that charging with B + resulted in more stable surface potential compared to charging with P + , but after 50 days the difference is negligible. The extrapolated long-term stability of SiO 2 electrets charged by ion implantation is around 1 year. SiO 2 is a promising electret for energy harvesting, which can be charged in a reproducible and stable way by ion implantation. The results are compared to corona charging of SiO 2 . The developed process can be used to realize vibration-based capacitive energy harvester systems using CMOS-compatible processes.

On the c-Si/SiO2 interface recombination parameters from photo-conductance decay measurements

“…61 Previous research has mainly focused on the effect of the surface charge on the effective lifetime of silicon for one excess minority carrier concentration or one surface charge density. [62][63][64] Here, the dependence of surface recombination velocity on both independent variables is explored. An investigation of excess minority carrier concentration from 10 14 to 10 16 cm -3 and dielectric charge concentration from À2 Â 10 12 to 7 Â 10 12 q/cm 2 is performed.…”

MEMS Technologies for Energy Harvesting

“…Among the materials most commonly used for electrets we find inorganic layers made of SiO 2 , a combination of SiO 2 and Si 3 N 4 layers, [52], and also organic compounds based on polymers. Among the polymers compatible with MEMS processes we may find the amorphous perfluorinated polymer CYTOP (Asahi Glass Col., Ltd), [53,54,55,56]. This polymer can provide up to four times more charge density than Teflon.…”

Micro harvester using isotropic charging of electrets deposited on vertical sidewalls for conversion of 3D vibrational energy

“…Important properties of electrets for energy harvesters are charge density and long term stability of the charges. Charging electrets is done by corona charging (Arakawa et al 2004) or by ion-implantation (Mescheder et al 2009). In this paper a new charging method of charging electrets with superior charging and charge stability is discussed.…”

“…The material properties of SiO 2 and CYTOP which are important for use as electrets are listed in Mescheder et al (2009). Standard 10-15 X cm boron doped (100) 4 00 Si-wafers were used for these experiments.…”

“…Left processed SOI-chip, right: packaged chip between two glass wafers acting as mechanical stops in Z-direction Details of the sample preparation and the charging setup are presented in Saad et al (2010). Instead of the well known corona charging (Arakawa et al 2004) or ion-implantation (Mescheder et al 2009), a low cost charging method using commercial so-called ionic hairdryer (Braun model 3549) was used. In this type of hairdryers, ions are produced to compensate for charging of hairs e.g.…”