Laser-assisted bonding between silicon and glass for the production of hermetic packages

Inhalt:
Hermetic packages fabricated using silicon microtechnology are important for the actual miniaturisation of quantum sensors, which will provide high accuracy and sensitivity for future industrial systems. For this purpose, bonding between silicon and glass with a UV marking laser is investigated. Compared to other hermetic bonding methods, laser bonding allows a lower global temperature stress and shorter process times while having the potential for high mechanical bond strengths and high hermetic properties. The laser parameter of power, marking speed and number of repetitions, which control the local temperature input by the laser, are evaluated. With optimum parameters a mechanical strength of at least 42.2 MPa is achieved, based on the bonding area of 4.6 mm². Here, the glass substrate breaks and the bond is not the limiting factor for the mechanical strength. A problem for the hermeticity is cracking of the glass substrate caused by too high temperature input which is shown in detail in this paper. This requires a high control of the temperature input by an automatic laser power regulation or substrate cooling for further optimization potential.