A universal bonding strategy for achieving CMOS-compatible silicon heterogeneous integration

Abstract

Silicon heterogeneous integration stands as a pivotal technology that underpins advancements in photonic integrated circuits and micro-electromechanical systems. In contrast to epitaxial growth, wafer bonding has gained significant attention for heterogeneous integration, as it overcomes limitations associated with lattice constants and film thickness. However, current silicon (Si) bonding methods face challenges when integrating materials such as lithium niobate (LiNbO3), silicon carbide, and fluoride glass, resulting in low interfacial strength and high thermal stress. In this work, a universal bonding strategy is presented that facilitates the formation of robust Si heterostructures, achieving a bonding strength of 4.2 MPa at 110 °C, which is significantly lower than the temperatures required for complementary metal-oxide-semiconductor (CMOS). This approach utilizes ultrathin amorphous silicon (a-Si) bonding interlayer deposited via COMS-compatible sputtering, enabling the transformation of higher-density chemically active non-stoichiometric silicon oxide (SiOx, 2 > x > 1) following surface activation, thereby demonstrating superior low-temperature bonding ability while preserving the structural advantages of direct bonding. Additionally, interfacial thermal stress and deformation are mitigated through finite element simulations to optimize structural mechanics. This versatile bonding strategy has been successfully demonstrated on several traditionally challenging-to-bond materials, providing a solid foundation for the development of next-generation Si-based devices.