On‐Chip Microheater‐Based Back‐End‐of‐Line Compatible Synthesis of VO2 Films for Reconfigurable Silicon Photonics

Abstract

We report a back‐end‐of‐line (BEOL)‐compatible approach for integrating high‐quality vanadium dioxide (VO2) into silicon photonic platforms using on‐chip doped silicon microheaters as localized thermal processors. VO2 is a promising material for reconfigurable photonics due to its large refractive index modulation and fast, energy‐efficient metal‐insulator transition (MIT). However, its integration is hindered by the high thermal budget required for crystallization and the difficulty of patterning. In this work, vanadium metal is deposited at room temperature and patterned via a lift‐off process, followed by microheater‐assisted local oxidation and crystallization to form VO2 without exceeding the global BEOL temperature constraints. Structural and spectroscopic characterization confirms the formation of VO2 with high crystallinity and accurate stoichiometry. Device‐level integration is demonstrated using silicon racetrack resonators, where the measured switching contrast shows excellent agreement with simulations based on literature optical constants, indicating material quality comparable to that of high‐temperature‐grown films. The microheater platform enables both material synthesis and reversible MIT switching, and is inherently scalable via parallel electrical biasing for wafer‐scale processing. Beyond VO2, this approach provides a general pathway for integrating thermally demanding functional materials into complementary‐metal‐oxide‐semiconductor (CMOS)‐compatible systems.