KTH Royal Institute of Technology
100 44 Stockholm
Further information can be found on the conference homepage
Anodic Bonding using Evaporated Borosilicate Glass Thin-Films
Abstract - The use of bulk borosilicate glass for anodic wafer bonding to silicon is well established in industry. We present an alternative approach, where a microstructured borosilicate glass thin-film is used as anodic bond layer, which allows for very moderate bond parameters with voltages as low as 30 – 60 V for silicon-to-silicon anodic bonding.
The glass films are deposited by plasma-assisted e-beam evaporation at high deposition rates. For anodic bonding film thicknesses of about 3 μm has proven to be sufficient.
The amount of sodium ions, crucial for anodic bonding, was investigated by wavelength dispersive X-ray spectroscopy (WDX) using a micro probe and proved to be close to the value of bulk borosilicate glass (3.5 – 4.5 %). In contrast to other methods of depositing borosilicate thin-films such as sputtering, depletion of the sodium ions by the deposition process is not observed.
The glass layer is deposited at temperatures below 80 °C and can be precisely microstructured by standard lift-off lithography. Adhesion to various substrate materials has been proven so that a range of materials can be made usable for anodic bonding to silicon.
In the paper we present experimental results on anodic bonding of different materials using intermediate borosilicate glass thin films.