Noam Shapiro | InZiv: How many "good" microLEDs are actually dead silent under electrical current?

Why does photoluminescence fail to guarantee functional microLED displays?

Standard microLED inspection relies heavily on photoluminescence (PL), which excites the active region optically to measure emission properties. However, PL misses critical electrical defects because it does not replicate the final device operating conditions. To capture true performance, manufacturers must employ electroluminescence (EL), which excites the junctions via current injection.

Electroluminescence serves as the gold standard because it provides direct electrical feedback and accurately forecasts how the microLED will perform in the target display backplane. Unfortunately, implementing standard EL on a wafer scale introduces two massive issues: physical contact damage to micro-scale pads and extremely slow probing speeds.

With conventional EL probers testing at a sluggish rate of just one LED per second, completing an inspection run on a single dense microLED wafer would take roughly two entire months. This throughput bottleneck has forced the display industry to rely on suboptimal testing methods, leading to poor yields and skyrocketing manufacturing costs.

In this short video, you can learn:
* The fundamental thermodynamic and physical differences between PL and EL testing
* Why electrical excitation is required to predict final display performance
* The crippling throughput bottlenecks and mechanical damage risks of conventional probe testing

📋 **Clip Abstract** This clip explores the critical differences between photoluminescence and electroluminescence in microLED inspection. It highlights why standard electrical probing is too slow and mechanically risky for volume manufacturing, despite being the only accurate way to predict device performance.

Is your photoluminescence (PL) inspection giving you false confidence in your microLED yield?

The problem with photoluminescence (PL) is that it can misrepresent the true performance of a microLED. This clip shows a direct, side-by-side comparison of the same microLED chip tested with both PL and electroluminescence (EL). The resulting topographical images reveal a stark difference in the measured defective area, highlighting a fundamental flaw in relying on optical excitation for quality control.

Under PL, the non-emissive, defective region appears smaller than it actually is. When the same chip is driven electrically via EL—mimicking its real-world operation—the defective area is visibly larger. This discrepancy leads to a "false positive," where a chip that would fail in a final display is passed during initial wafer-level screening, ultimately poisoning the downstream manufacturing process and lowering final yields.

Beyond just identifying dead zones, PL also fails to accurately predict the light output intensity. The process of optical excitation in PL does not replicate the carrier injection and recombination dynamics of electrical excitation. As a result, the intensity map generated by PL can be a poor predictor of the chip's actual luminance and uniformity under operational conditions, which are critical for display quality.

In this short video, you can learn:
* The visual evidence of PL providing "false positives" on microLED defects.
* Why EL reveals a larger, more accurate defective area than PL on the same chip.
* How PL provides an inaccurate prediction of a microLED's final light intensity.
📋 **Clip Abstract** Photoluminescence (PL) testing can be a dangerously inaccurate predictor of microLED performance, often underestimating the size of defective areas. This direct comparison with Electroluminescence (EL) shows why PL can lead to false positives, passing faulty chips that will ultimately reduce display yield.
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Can we scan 9 million microLEDs electrically without touching or destroying the wafer?

Overcoming the speed and contact damage limitations of standard electroluminescence is the Holy Grail of microLED manufacturing. A high-throughput, non-damaging EL wafer inspection system can scan up to 6 million chips per hour. This reduces a full wafer scan time from a commercially non-viable two months down to just one hour.

This rapid testing capability functions by safely exciting and evaluating 1,600 microLEDs every single second. The resulting dataset provides display engineers with critical parameter mapping, including go/no-go functionality, individual pixel emission intensity, precise dominant wavelength, and luminance measurements.

Most importantly, the platform extracts full current-voltage (IV) curves and electrical properties without physical damage to either vertical or flip-chip architectures. Armed with these comprehensive IV characteristics, manufacturers can establish precise pass-fail thresholds to filter out defective dies before mass transfer.

In this short video, you can learn:
* How high-throughput EL testing achieves scanning speeds of 1,600 chips per second
* The critical parameters captured, including dominant wavelength, luminance, and IV curves
* How non-damaging inspection protects delicate contact pads while enabling automated mass production

📋 **Clip Abstract** This clip introduces high-throughput, non-damaging electroluminescence inspection capable of testing 6 million microLEDs per hour. It details how capturing rapid optical and electrical data helps manufacturers secure high transfer yields and lower production costs.