A novel method for laser assisted room temperature bonding of two substrates is presented. The method enables the
packaging of delicate (bio)structures and/or finished (MEMS) devices, as there is no need for a high temperature
annealing process. This also allows the bonding of two substrates with non-matching thermal expansion coefficients.
The basis of the presented technology is the ability to create a direct pre-bond between two substrates. These can be two
glass substrates, of which one has a thin film metal coating (e.g. Cr. Ti, Ta, Au…), or a silicon-glass combination. After
(aligned) pre-bonding of the two wafers, a laser (e.g. a Nd:YAG laser) is used to form a permanent bond line on the bond
interface, using the metal layer as a light absorber (or the silicon, in the case of a glass-silicon combination). The
permanent bond line width is in the order of 10-50μm.
The use of a laser to form the permanent bond ensures a hermetic sealing of the total package; a distinctive advantage
over other, more conventional methods of room temperature bonding (e.g. adhesive bonding). He-leak testing showed
leak rates in the order of 10-9 mbar l/s. This meets the failure criteria of the MIL-STD-883H standard of 5x10-8 mbar l/s.
An added functionality of the proposed method is the possibility to create electrical circuitry on the bond interface, using
the laser to modify the metal interlayer, rendering it electrically non-conductive. Biocompatible packages are also
possible, by choosing the appropriate interlayer material. This would allow for the fabrication of implantable packages.