Full Process Control Solutions for High Precision Mass Production of SRG Optical Waveguides in AR/MR Applications

Abstract

Surface Relief Grating (SRG) waveguides have been adopted as the mainstream solution in the industry, for its slim profile, high transparency, and large field of view. Furthermore, with their superior optical performance and mass production potential, SRG waveguides have emerged as a critical pathway for high‑performance augmented reality (AR) and mixed reality (MR) displays. In the mass production of SRG optical waveguides, where multi‑layer and double‑sided fabrication demand strict process control of overlay, geometry, and defects. We present a full process control solution for SRG mass production, combining optical critical dimension (OCD) metrology for the critical parameters of SRGs such as the grating depth, slanted angle, and periods, picosecond ultrasonic (PULSE™) technology for the metal film thickness measurement, image‑based overlay (IBO) on the IVS™ platform for precise overlay control, automated optical inspection based Dragonfly® system for the defects integrated throughout the entire SRG manufacturing process. OCD shows sub‑nanometer deviation and excellent matching with AFM, with high dynamic stability. PULSE™ technology ensures rapid, non‑contact measurement and uniformity control of chromium (Cr) and aluminum (Al) hard masks. Overlay precision reaches 0.26 nm (X) and 0.18 nm (Y) at 3σ, well within sub‑100 nm alignment requirements. Automated inspection captures >95% of submicron defects with low false positives. This framework has been validated in mass production at leading AR/MR manufacturers, enabling fully digitalized closed‑loop process control and supporting large‑scale, high‑yield SRG waveguide manufacturing.