Stress reduction and wafer bow accommodation for the fabrication of thin film lithium niobate on oxidized silicon

Abstract

Sub-micrometer-thick lithium niobate on an insulator is a promising integrated photonic platform that provides optical field confinement and optical nonlinearity useful for state-of-the-art electro-optic modulators and wavelength converters. The fabrication of lithium niobate on insulator on a silicon substrate through ion slicing is advantageous for electronic-photonic integration but is challenging because of debonding and cracking due to the thermal expansion coefficient mismatch between silicon and lithium niobate. In this work, the fabrication of thin film lithium niobate on insulator on a silicon handle wafer is achieved, informed by structural modeling, and facilitated by accommodating for dissimilar wafer bows using a bonding apparatus. Structural finite element analysis of strain energy and stress, due to thermal expansion coefficient mismatch at elevated temperatures, is conducted. High strain energies and stresses that result in debonding and cracking, respectively, are studied through modeling and reduced by selecting optimized substrate thicknesses followed by an experimental technique to bond substrates with dissimilar bows. A lithium niobate thin film with a thickness of 800 nm is successfully transferred to an oxidized silicon wafer with a root mean square surface roughness of 5.6 nm.

O3-Annealing Effect on the Etching Resilience of a TiO2/Al2O3 filter Prepared by Atomic Layer Deposition

“…However, the integration of photonic circuits poses challenges to the performance of optical coatings . Processes such as polishing, chemical etching, and laser processing can adversely affect the characteristics of materials, leading to changes in surface roughness, uneven etching profiles, and even delamination. , A standard workaround to mitigate this problem involves transferring the optical coating onto prepatterned substrates, which can result in debonding and cracking . Therefore, it is crucial to investigate methods that enhance the resilience of optical materials to manufacturing processes associated with photonic integration.…”

Fabrication of Low Loss Lithium Niobate Rib Waveguides Through Photoresist Reflow

“…operation of these devices at low voltages [5], [7]. The ability to fabricate thin film LNOI on silicon substrates has also opened avenues for hybrid integration of electronic and optical devices [14]- [16].…”