Debris-free low-stress laser dicing for multi-layered MEMS wafers

We have developed a novel debris-free low-stress laser dicing technology for multi-layered MEMS wafers, which are generally consisted of glass and Si. Our technology combines two processes: dicing guide fabrication and wafer separation process. The first process is the 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 silicon and/or glass. The internal transformed lines worked well as a guide of the separation. We found that the internal transformation only in Si layer was enough for dicing the glass/Si double-layered wafer. Also the thermal stress induced by the CO₂ laser was quite effective to propagate the crack inside the glass layer without internal transformation. The double-layered wafer consisting of glass and silicon can be diced in low stress by our technology.