Debris-free low-stress high-speed laser-assisted dicing for multi-layered MEMS

We have developed a novel debris-free low-stress high-speed laser-assited dicing technology for multi-layered MEMS wafers, which generally consist of glass and Si. Our technology combines two processes: fabrication of dicing guidelines and wafer separation process. The first process is an internal transformation using a pulsed 1μm laser. The second process is non-contact separation by thermally-induced crack propagation using a CO₂ laser or mechanical separation by bending stress. We tested several pulsed lasers with different pulsewidths, including a Nd:YVO₄ laser and an Yb fiber laser for generating the internal transformation in Si and/or glass. The internal transformed lines worked well as a guide of the separation. We found that internal transformation only in the Si layer was enough for dicing the glass/Si double-layered wafers. Also the thermal stress induced by the CO ₂ laser was quite effective in propagating the crack inside the glass layer without internal transformation. The double-layered wafer consisting of glass and silicon can be diced with low stress by our technology.