High-Precision Mapping and Analysis of Wafer-Scale Distortions in InP Membranes to Si 3D Integration

Heterogeneous integration helps to maximize the performance of photonics or electronics devices by leveraging the strengths of diverse material platforms within a unified process flow. A promising approach is the 3D integration of InP photonic or electronic membranes to other substrate materials containing photonics or electronics ICs via adhesive bonding. However, wafer-scale spatial distortions arising from the bonding process can compromise fabrication. Herein, we used electron-beam metrology to investigate the distortion of InP membranes resulting from wafer-scale bonding with benzocyclobutene (BCB). We measured both the linear and residual components of distortions across the tested wafers. First, bonding of InP substrate with BCB on various carrier substrates (Si, InP, SiC, and glass) was realized, which unveiled post-bonding membrane expansion factors in the range of ~0-325 ppm and beyond that for the glass carrier. The diversion of these values from theoretical estimations was linked to the adhesive bonding process. Next, we examined the effect of BCB thickness in the ranges of 1-12μm, residual mechanical stress, and the impact of defects on distortions. Using these findings, we experimentally verified that the largest part of distortions can be efficiently pre-compensated to overcome the challenges of multilayer overlay errors in the fabrication of heterogeneously integrated photonic and electronic devices.