Dmitriy Kim | WEVE Co., Ltd: If wafer and carrier steps were flawless, why do panels still need dual-side inspection for flip chips?
07:52 - 09:33
Other snippets from this talk
Summary of the clip:
If wafer and carrier steps were flawless, why do panels still need dual-side inspection for flip chips?
The method can be applied across three different production and inspection steps, spanning epi wafers, COWs, and COCs. The panel stage is especially interesting because it does not matter whether earlier steps were completely perfect. You still must confirm that chips placed on panels are cracks-free. That is why panel inspection remains necessary even after wafer and carrier screening.
A single data point can be misleading. A white light surface inspection, or AOI, appears pretty much okay at first glance. Viewed through photoluminescence, however, it is quite obvious that many chips are far from being okay. This comparison shows the importance of having different data points for a particular sample, because surface appearance alone does not reveal the full chip condition.
Flip chips are one difficult chip type. For flip chips, inspection must be done on both sides of the wafer or carrier, because the light-emitting layer faces down. Both-side inspection and data correlation are therefore required. This issue was overcome a few years ago. The method now works with all popular design types, including fully populated wafers and wafers with staircase patterns.
In this short video, you can learn:
* Panel inspection is still required because chips must be confirmed cracks-free even if prior wafer and carrier steps were perfect.
* White light AOI can look acceptable while photoluminescence reveals many chips far from okay, so multiple data points are needed.
* Flip chips require dual-side wafer or carrier inspection and data correlation because their light-emitting layer faces down.
📋 **Clip Abstract** The method spans three production and inspection steps, from epi wafers and COWs to COCs, with panel inspection still needed to confirm chips are cracks-free regardless of earlier perfection. It contrasts white light AOI with photoluminescence, then explains that flip chips need both-side inspection and data correlation because the light-emitting layer faces down, while all popular wafer designs are supported.
About the speaker:
* Speaker: Dmitriy Kim
* Companies: WEVE Co., Ltd
* Event: Eindhoven 2026
* Location: High Tech Campus, Eindhoven
#PhotoluminescenceInspection, #WhiteLightAOI, #FlipChipInspection, #StaircaseWaferDesign, #MicroLEDInspection, #WaferLevelMetrology
This is a highlight of the presentation:
Multimodal MicroLED Inspection: From Wafer Screening to Panel Integration
More Highlights from the same talk.
02:13 - 04:37
Why does photoluminescence mapping take 6 minutes instead of 2.5, and what does 4,000x resolution density buy you?
Why does photoluminescence mapping take 6 minutes instead of 2.5, and what does 4,000x resolution density buy you?
Conventional photoluminescence mapping, or PL mapping, is used to screen epitaxial wafers. It is not very precise. It used to work when inspection targeted epi wafers for mini-LEDs or larger LEDs. Many companies still use this outdated method. Newer solutions are available. One example covers a six-inch wafer and completes PL inspection in 2.5 minutes, but its measurement step is two millimeters. That step matters because microLED epi wafers need higher resolution to locate affected areas.
Our approach resolves that limitation. It analyzes a full epi wafer in around six minutes with a measurement pitch of 30 microns. Against widely accepted solutions on the market, that gives roughly 4,000 times higher density in terms of resolution. The left illustration shows what our technology provides; the right shows the resolution of the widely used alternative. This finer pitch is necessary for microLED production because affected areas must be found across the wafer.
The comparison becomes stark when the same existing techniques are used and resolution is simply increased from two millimeters to 30 microns. Theoretically, that would take around 180 hours instead of just 2.5 minutes. That is how significant the difference is. A six-inch wafer inspected at 30-micron pitch in six minutes is not a small upgrade; it changes what can be screened for in microLED epi wafers.
In this short video, you can learn:
* Conventional PL mapping was adequate for larger mini-LED and LED epi wafers, but its two-millimeter measurement step is insufficient for microLED epi wafers.
* The discussed high-resolution PL inspection completes a six-inch full epi wafer in around six minutes at a 30-micron measurement pitch.
* Increasing the same existing method from two millimeters to 30 microns would theoretically take around 180 hours instead of 2.5 minutes.
📋 **Clip Abstract** Photoluminescence mapping has long screened epitaxial wafers, but its two-millimeter measurement step is poorly matched to microLED epi wafers. A 30-micron measurement pitch delivers roughly 4,000 times higher resolution density and inspects a six-inch wafer in around six minutes, whereas merely scaling the existing approach to that pitch would theoretically take around 180 hours.
About the speaker:
* Speaker: Dmitriy Kim
* Companies: WEVE Co., Ltd
* Event: Eindhoven 2026
* Location: High Tech Campus, Eindhoven
#PhotoluminescenceMapping, #EpiWaferScreening, #MicroLEDInspection, #MicronPitchResolution, #MicroLEDManufacturing, #WaferMetrology
12:45 - 14:03
How much data does inspecting 10 million chips per wafer generate, and can fabs actually handle it?
How much data does inspecting 10 million chips per wafer generate, and can fabs actually handle it?
Starting from a six-inch wafer, in the case of COWs, it contains around 10 million chips. The inspection data collected is around 70 gigabytes per wafer. Information is obtained individually from each chip. The data includes the locations of each chip. That combination of per-chip information and coordinates is what makes later traceability possible, because the volume and granularity are both high.
The point of inspecting at different levels is traceability. Manufacturers are sometimes not sure where a problem occurs. To go back and find it, you need to trace each chip exactly. That is why the data and chip locations are needed, because the whole point is tracing each chip. The stated value is the ability to return to a specific chip when the origin of a problem is uncertain.
The question also raised whether there is a spectrum for each point, just some characteristics, or any standard. In the answer, the criteria start from a six-inch wafer and COWs. For that case, the inspection yields around 70 gigabytes per wafer, with information from each chip and each chip's location. So the discussion is anchored in per-chip data volume and traceable locations rather than a stated standard or spectrum.
In this short video, you can learn:
* A six-inch COWs wafer contains around 10 million chips, and inspection data is around 70 gigabytes per wafer.
* The inspection gets information individually from each chip and includes the locations of each chip.
* Multi-level inspection is used so manufacturers can trace each chip exactly when they are not sure where a problem occurs.
📋 **Clip Abstract** A six-inch COWs wafer contains around 10 million chips, and the inspection data is around 70 gigabytes per wafer. Information is obtained individually from each chip, with chip locations included, so multi-level inspection can trace each chip exactly when manufacturers are not sure where a problem occurs.
About the speaker:
* Speaker: Dmitriy Kim
* Companies: WEVE Co., Ltd
* Event: Eindhoven 2026
* Location: High Tech Campus, Eindhoven
#COWsWafer, #TenMillionChips, #SeventyGigabytesPerWafer, #PerChipTraceability, #MicroLEDInspection, #SemiconductorInspection
05:47 - 07:35
Can photoluminescence alone qualify microLED chips, or must AOI and colour-difference analysis be fused with it?
Can photoluminescence alone qualify microLED chips, or must AOI and colour-difference analysis be fused with it?
Two inspection routes dominate chip screening: electroluminescence, which needs an electrical current applied to make the chip glow, and photoluminescence, which excites the same emission with photons and no contacts. The field's requirements are described as tough: the method must be accurate, fast enough, repeatable and non-destructive, because a destroyed sample yields no data. It must also be flexible across many chip types and designs, and ultimately low cost.
The two methods are compared constantly, and the talk reports a steady stream of questions about which is correct and which should be used. The answer given here is not a straight choice. While working on microLED inspection, the team concluded that photoluminescence alone is not enough to qualify chips, which is why the approach moved to fusing several inspection signals rather than betting on a single one.
The multimodal stack combines three inspections: automated optical inspection, photoluminescence inspection and colour-difference analysis. Fusing that huge amount of data, the system analyses a six-inch wafer in around ten minutes, whether the wafer is chip-on-wafer or chip-on-carrier. That throughput is the practical payoff of combining methods: coverage of defects that emission mapping alone would miss, delivered at a cycle time that keeps wafer-level screening usable in production.
In this short video, you can learn:
* Photoluminescence alone is not enough for microLED chip qualification, according to the team's own experience.
* Any inspection method has to be accurate, fast enough, repeatable, non-destructive, flexible across chip types and designs, and low cost.
* Automated optical inspection, photoluminescence and colour-difference analysis are fused to analyse a six-inch COW or COC wafer in roughly ten minutes.
📋 **Clip Abstract** Chip screening is usually framed as electroluminescence versus photoluminescence, but the stated requirements — accuracy, speed, repeatability, non-destructiveness, design flexibility and low cost — make a single method hard to defend. The presented solution fuses automated optical inspection, photoluminescence and colour-difference analysis, analysing a six-inch COW or COC wafer in around ten minutes.
About the speaker:
* Speaker: Dmitriy Kim
* Companies: WEVE Co., Ltd
* Event: Eindhoven 2026
* Location: High Tech Campus, Eindhoven
#PhotoluminescenceInspection, #AutomatedOpticalInspection, #ColourDifferenceAnalysis, #ChipOnCarrier, #MicroLED, #DisplayManufacturing