Glow Discharge Mass Spectroscopy Study of Ion Concentrations of Joints in Anodic Bonding of Borosilicate Glass to Ultrathin Silicon

Abstract

Ion concentrations in the joints of borosilicate glass anodically bonded to ultrathin silicon were measured by glow discharge mass spectroscopy (GDMS), a highly conventional and sensitive method that measures profiles up to depths of 100 µm. The ion migration behavior was also investigated. The bonding current was an exponential function of the silicon thickness. All cations in the glass migrated towards the cathode, whereas the non-bridging oxygen ions were retained in the glass, possibly because of anodic bonding in the negatively charged depletion layer formed adjacent to the silicon-Tempax^® boundary. The anodic bonding is apparently related to the different migration lengths of the oxygen and silicon ions. The lower migration length of the oxygen ions may result from the lower migration length of the ionized cations. These findings confirm the utility of GDMS in investigating the impact of joints in anodic bonding.