The extended reality (XR) sector is experiencing explosive growth, fueled by surging demand for immersive augmented reality (AR) experiences in consumer electronics, particularly XR glasses—with projections placing the global AR market at approximately USD 150 billion in 2025. This surge, and the sector’s long-term success, hinges on seamless user experiences to fuel widespread adoption. At the heart of this lies diffractive waveguides, the hardware responsible for blending digital images with the real world. Yet, as the industry advances toward high-volume manufacturing amid major investments from global tech leaders, a core challenge persists: achieving superior optical performance at efficient production scales. This tension is prompting a convergence on standardized platforms to achieve quality and scale.
One promising solution gaining momentum is spatial atomic layer deposition (ALD), which looks poised to provide high-quality optical coatings without bottlenecking production. This is highlighted as a leading Asian ODM—backed by a prominent technology firm—selected Beneq’s C2R™ plasma-enhanced spatial ALD system as it moves to scale AR waveguide production. Reports indicate other manufacturers are exploring similar options, suggesting an industry-wide pivot toward spatial ALD for premium XR coatings.
ALD Evolution: From Temporal to Spatial
For those in photonics, ALD is familiar—valued for producing exceptional optical coatings with unmatched conformality and uniformity. Conventional temporal ALD is characterized by sequential precursor pulsing and purging, while plasma-enhanced ALD (PEALD) uses plasma-driven reaction for added flexibility, like lower-temperature processing and greater film tunability (e.g. adjustable stress and refractive indices) over thermal methods.
Despite ALD’s coating quality, thickness scaling has been a challenge, with deposition rates typically at 20–100 nm/h (plasma on the lower end). This has created economic hurdles for mass production of thicker films. In short, economics, not performance, has been the bottleneck for wider ALD use over legacy coating methods.
This is where spatial ALD changes the game: by separating precursors in space, rather than time, it overcomes the productivity bottleneck by boosting throughput—up to 100x faster—while maintaining the film quality benefits that ALD is known for, Fig. 1. Just like temporal ALD, spatial ALD can also be divided between thermal or plasma-enhanced modes, with the latter imparting the earlier mentioned processing benefits. This makes affordable, precise and low-loss coatings feasible, combining speed with quality.
Figure 1. a) Temporal ALD, b) spatial ALD, c) productivity vs. conformality for ALD/spatial ALD and other deposition technologies.
In AR, this shift is particularly relevant. Diffractive waveguides built on platforms like advanced surface relief gratings (SRG+) and nano-imprint lithography (NIL) feature complex topographies that demand exceptionally uniform, conformal layers for peak efficiency, Fig. 2. Plus, with polymers involved, low-temperature processing is essential—spatial ALD, especially when plasma-boosted, fits the bill without compromises.
Figure 2. Surface relief gratings coated with low-temperature TiO2 using spatial ALD. Gap-fill coating is achieved even with slanted profiles.
Inside Beneq’s C2R™: A Practical Take on Spatial ALD
Beneq’s C2R™ is illustrative as it uses a rotary setup to spatially isolate precursors to achieve deposition rates up to 2000 nm/h—up to 100 times faster than conventional ALD, according to Beneq. Plasma integration supports low-temperatures processing for polymer compatibility and tuneability—factors that position it well for coating diffractive gratings in AR waveguides. It deposits high-index materials like TiO₂ (refractive index ~2.61 at 448 nm), Al₂O₃, Ta₂O₅, and HfO₂, delivering low optical loss (~3 dB/cm) and stress control (from +1000 to -200 MPa) for stable multilayers. Beyond oxides, fluoride-based materials are part of the catalogue of processes. In-situ broadband monitoring and real-time optimization and compensation enhance coating precision. Spatial ALD thus offers the best of both worlds: high quality—uniformity, conformal gap-filling, and low-loss metrics—and productivity, making it ideal for AR waveguides.
Real-World Impact and What’s Next
The paradigm shift from temporal to spatial ALD represents a pivot from ALD’s historical limitations, opening avenues for photonics manufacturing. Beyond AR, spatial ALD shows promise for addressing hurdles in automotive lenses, UV coatings, and silicon photonics, where balancing quality, low-temperature processing, and cost are essential. As photonics needs intensify, plasma-enhanced spatial ALD is capturing industry attention, appealing to those chasing performance without compromise. Innovators like Beneq, are charting this path forward.
Author
Dr. Alexander Perros, Director of Business Development, Beneq Oy
