AbstractThe critical adhesion energy of benzocyclobutene (BCB)-bonded wafers is quantitatively investigated with focus on BCB thickness, material stack and thermal cycling. The critical adhesion energy depends linearly on BCB thickness, increasing from 19 J/m2 to 31 J/m2 as the BCB thickness increases from 0.4 μm to 2.6 μm, when bonding silicon wafers coated with plasma enhanced chemical vapor deposited (PECVD) silicon dioxide (SiO2). In thermal cycling performed with 350 and 400 oC peak temperatures, the significant increase in critical adhesion energy at the interface between BCB and PECVD SiO2 during the first thermal cycle is attributed to relaxation of residual stress in the PECVD SiO2 layer. On the other hand, the critical adhesion energy at the interface between BCB and PECVD silicon nitride (SiNx) decreases due to the increase of residual stress in the PECVD SiNx layer during the first thermal cycle.
