Daniel de Sá Pereira | Bühler Alzenau: Your high-index waveguide material is turning crystalline and scattering light. How do you stop it?

Can we deposit thick high-index TiO2 films for AR without inducing lossy crystallization?

Depositing high refractive index (RI) titanium oxide (TiO2) is essential for fabricating efficient, high-angle diffractive optical elements in augmented reality (AR) waveguides. However, as the thickness of TiO2 films increases, they tend to transition from amorphous to crystalline phases. This crystallization introduces grain boundaries, which cause high optical scattering loss and degrade the performance of waveguide gratings.

To combat this limitation, advanced magnetron sputtering techniques are being deployed to tightly control the film growth dynamics. This enables the deposition of fully amorphous TiO2 layers up to 600 nanometers in thickness. Crucially, this process maintains a high, stable refractive index across the entire depth while preserving a completely amorphous structure.

This manufacturing breakthrough directly addresses the scalability demands of next-generation AR devices. By scaling amorphous film thicknesses without sacrificing optical quality, optical designers can engineer deeper, more complex grating profiles. This translates directly to wider fields of view and superior out-coupling efficiency in consumer-grade smart glasses.

In this short video, you can learn:
* How magnetron sputtering controls the phase transformation of TiO2 to keep it fully amorphous.
* The engineering milestone of doubling controllable amorphous film thickness from 300 to 600 nanometers.
* Why maintaining a stable refractive index at higher thicknesses is vital for AR waveguide gratings.

📋 **Clip Abstract** This clip details how Bühler Leybold Optics successfully scaled the deposition of amorphous titanium oxide films to 600 nm thickness. By preventing crystallization and maintaining a stable refractive index, this sputtering technique enables the fabrication of highly efficient diffractive AR waveguides.

Can next-generation planarization bypass the physical limitations of chemical mechanical planarization to achieve true atomic-scale flatness?

As micro-roughness and surface waviness become critical bottlenecks in advanced semiconductor packaging and precision optics, conventional chemical mechanical planarization (CMP) often reaches its physical limits. Ion beam trimming (IBT) emerges as the definitive successive step to CMP, offering a non-contact, dry etching alternative that can target and eliminate micro-roughness at sub-nanometer scales. By utilizing highly controlled ion bombardment, this technology flattens surfaces to tolerances that traditional mechanical slurries simply cannot resolve.

The core of this advanced planarization capability lies in the adaptation of proven ion beam figuring technology. By leveraging years of industrial experience in high-precision optical figuring, specialized ion sources can be precisely modulated to correct spatial thickness variations across a substrate. This transition from optical figuring to semiconductor-grade trimming allows manufacturers to address localized topography errors with extreme spatial resolution.

To transition this technology from laboratory environments to high-volume manufacturing, the system architecture must balance throughput, flexibility, and automation. High-yield production demands rapid processing speeds, while research and development applications require a modular platform capable of integrating in-situ metrology and measurement diagnostics directly into the vacuum chamber.

In this short video, you can learn:
* Why ion beam trimming (IBT) is positioned as the essential process step after chemical mechanical planarization (CMP).
* How established ion beam figuring technology is repurposed to achieve ultra-flat surface topologies.
* The design considerations for balancing high-throughput production yields with R&D flexibility and in-situ metrology.

📋 **Clip Abstract** The speaker introduces ion beam trimming (IBT) as an advanced flattening technology that surpasses the capabilities of chemical mechanical planarization (CMP) by reducing micro-roughness. He explains that the tool leverages established ion beam figuring technology while incorporating automation, high throughput for production yield, and integration flexibility for R&D measurements.

🎤 Speaker: Daniel de Sá Pereira
🏢 Company: Bühler Leybold Optics
📅 Event: AR/VR Connect 2025
📍 Location: Conference Centre, High Tech Campus, Eindhoven, Netherlands

🌐 Learn more at the next TechBlick event: https://www.techblick.com

How do you prevent ultra-thin 300mm optical wafers from turning into "potato chips" during deposition?

Manufacturing flat meta-optics on thin glass substrates presents a major mechanical challenge in semiconductor-level optical fabs. When depositing thick functional layers on thin (e.g., 210-micron) 300mm wafers, high internal film stress causes severe wafer warping, commonly known as "potato chipping." This warp disrupts automated handling equipment and ruins photolithographic depth-of-focus window parameters.

To solve this, advanced stress-engineering processes are applied during magnetron sputtering to minimize intrinsic film stress. By meticulously tuning deposition parameters, engineers can now deposit 2 to 3-micron thick coatings on a single side of an ultra-thin wafer without causing any structural bending.

Maintaining a perfectly flat wafer geometry is critical for seamless integration into high-throughput automated fabs. It allows for advanced post-processing, such as flipping the wafer to deposit double-sided structures, which is essential for building complex meta-surfaces and high-index AR gratings.

In this short video, you can learn:
* The root causes of wafer warp ("potato-chipping") when coating thin 300mm optical substrates.
* The sputtering process controls used to minimize intrinsic stress in 2-to-3 micron thick films.
* Why maintaining wafer flatness is a critical requirement for robotic automation and double-sided lithography.

📋 **Clip Abstract** This clip addresses the challenge of wafer warp when depositing thick optical coatings on thin 300mm glass substrates. It explains how stress-matched deposition techniques enable 2-to-3 micron thick flat coatings, unlocking automated processing and double-sided meta-surface fabrication.