A silicon-to-silicon anodic bonding process using a glass layer deposited by electron beam evaporation will be described. Wafers are bonded at a temperature as low as 135 degrees C with an applied voltage as small as 35 V-dc, enabling this technique to be applied to vacuum packaging of microelectronic devices. Experimental results reveal that an evaporated glass layer of more than 1 mu m thick is suitable for anodic bonding. Finally, the role of sodium ions in anodic bonding was also studied by investigating the theoretical bonding mechanism and examining the results of secondary ion mass spectroscopy analysis.