Glass-to-glass anodic bonding process and electrostatic force

In this paper, 4-in. glass wafers (Pyrex 7740), with one wafer surface sputtered with a layer of amorphous Si, are successfully bonded together. The effects of the bonding parameters on bond quality are investigated using Taguchi method. Four process parameters: bonding temperature, voltage, bonding time and vacuum condition, are considered. The bond efficiency ranges from 94% to 99.9% and the bond strength ranges from 10 to 25 MPa. A model for evaluating the electrostatic force for glass-to-glass wafer anodic bonding is established. It is found that both bonding temperature and voltage applied have significant effects on the magnitude of the electrostatic force. At a high bonding temperature and a high voltage, a larger electrostatic force is generated due to higher ion mobility. The established model is in a good agreement with the experimental results. (C) 2004 Elsevier B.V. All rights reserved.