Pixel process progress: New measurements guide improvements in microLED process technology

The Challenge 

MicroLEDs are microscopic light-emitting semiconductors that form the pixels of next-generation displays. They promise brighter images, lower power consumption and smaller high-resolution displays. Their appeal spans augmented and virtual reality headsets, automotive head-up displays and wearables, where transparent, high-brightness screens create possibilities close to users’ faces. But this proximity makes quality unforgiving. Variations in colour, brightness or uniformity that would be invisible on a television can become obvious when worn or embedded in a windscreen. Defects that might once have been tolerated are now commercially unacceptable. 

Traditional semiconductor inspection methods were developed for mature silicon manufacturing, where devices behave consistently and testing a few wafer locations is usually enough to confirm quality. MicroLEDs are different. A single wafer can contain millions of tiny light-emitting devices, each acting as an individual pixel. Even one faulty pixel can be visible, so manufacturers need to check entire wafers reliably without slowing production. 

The challenge spans the manufacturing process, where early steps strongly influence brightness, efficiency and reliability. Companies such as Porotech, a UK company developing porous semiconductor materials, and RENA, a global leader in wet-chemical surface treatment, are developing techniques to enhance performance and yield. Yet small process changes can significantly affect the final display. Yet there is still no consistent, wafer-scale method to compare process impacts across suppliers or production lines, making it hard to identify which approaches truly work. 

Without early, reliable inspection, problems are often discovered late, when wafers have already accumulated months of value and fixes are costly. As the microLED market scales, manufacturers will need faster, earlier and more consistent measurement. Those who define how quality is measured will shape how the supply chain develops.

The Solution 

NPL was well placed to address this gap. As part of the Department for Science, Innovation and Technology’s 2025 investment in new semiconductor metrology capabilities, NPL combined expertise in applied metrology, compound semiconductors and advanced characterisation, and convened partners across the value chain. 

The University of Cambridge provided early-stage gallium nitride wafers and the porosification process. RENA supplied production passivation equipment. Porotech contributed microLED wafers representing later semiconductor manufacturing stages. 

The project demonstrated how metrology can track changes across multiple manufacturing stages. To do so, NPL developed new metrology techniques, two of which were the focus of this work package. 

The first is rapid and non-destructive: photoluminescence spectroscopy illuminates a wafer and analyses the light it emits. Its colour, intensity and uniformity reveal material quality and device performance. Crucially, it can image entire wafers in minutes rather than measuring point by point, providing an early health check while defects remain cheap to deal with. 

The second technique is slower and more forensic. NPL uses OrbiSIMS mass spectrometry, a unique high-resolution tool it developed to analyse the chemical and structural makeup of materials at nanoscale. By identifying trace contaminants, compositional changes and structural features, it helps explain why a defect occurred once rapid screening has flagged a problem. For manufacturers, this provides root-cause insight rather than guesswork and speeds up the process considerably. For example, assessing porosification previously relied on electron microscopes, testing small material volumes over several hours. OrbiSIMS can deliver the same outcome in minutes, allowing manufacturers to probe multiple wafer areas and obtain more representative data. 

Together, the two methods reflect how semiconductor fabricators operate in practice: fast, wafer-scale screening to detect defects, followed by deep analysis to understand and correct them. 

The Outcome 

This work package addressed a key challenge in microLED manufacturing: improving yield through better measurement. Current approaches often rely on end-of-line testing, which is time-consuming and makes it difficult to identify which process stages need optimisation. By contrast, this project demonstrated how in-line measurement can give manufacturers earlier visibility of defects and performance changes, helping to reduce costs and accelerate process maturity. It also addressed a gap in existing methods, which tend to focus on physical structure but lack the chemical insight needed to understand and refine device performance. 

Working with RENA and Porotech, and with support from the University of Cambridge, NPL developed and demonstrated two complementary measurement capabilities. Together, these allow manufacturers to track key performance characteristics across multiple wafer-processing stages, while providing deeper insight into the chemical and structural changes that influence device behaviour. 

These capabilities give manufacturers earlier, more reliable insight into process performance. The work also showed clear improvements in light output linked to partner-developed techniques, indicating a stronger foundation for more efficient devices. For industry partners, this provides robust evidence to guide development decisions and improve manufacturing outcomes, while demonstrating how advanced metrology can support the scale-up of next-generation display technologies.

The Impact 

The commercial implications are significant. MicroLEDs are widely seen as a large, fast-growing market, with applications spanning consumer electronics, automotive displays and wearables. As production ramps up, detecting defects early reduces technical risk, shortens development cycles and protects yield, all critical for investors and manufacturers. 

For the UK, early leadership in metrology offers strategic leverage. Domestic firms rely heavily on imported inspection tools, often from the United States. Developing home-grown capability strengthens supply-chain resilience, supports international standards development and gives British companies influence in how the industry evolves. 

The project also showcases the strength of UK intellectual property. NPL’s OrbiSIMS platform offers a distinctive forensic capability, while its photoluminescence imaging approach is patented and being commercialised. By linking materials, measurement and devices, the programme demonstrates how measurement science can underpin industrial competitiveness.

In a sector where tiny imperfections cause faults obvious to the naked eye, the ability to measure well is not merely technical housekeeping. It is the foundation of trust, performance and growth.