Defect detection using PL measurement method | Micro LED PL inspection system

Highly sensitive detection of defects that cannot be detected by AOI.

In general, scratches, dust, and wiring failures can be detected by appearance inspections such as automated optical inspection, but cracks in crystals and defects in LED chips cannot be adequately detected by AOI.


Hamamatsu Photonics has focused on the "emission wavelength" and "emission intensity" that can be measured by PL-based imaging and developed a technology to detect defects and impurities inside the crystal of semiconductor wafers for micro LEDs.


As MiNY PL allows defects detection with highly sensitive images, clear observation of microscopic defects will be possible.


Combining this internal inspection using PL measurement with appearance inspection makes more precise inspections possible.

Detect defects

Converts emission wavelength to a mapping image and detects wavelength variations with high accuracy of ± 0.5 nm

Subtle variations in the emission wavelength of the micro LEDs are said to directly affect the color and brightness of the display. A wavelength variation of 2 nm in the emission wavelength of a micro LEDs can be recognized by the human eye as color unevenness. Variations in emission wavelength is a key parameter for producing micro LEDs with uniform hue and brightness.

MiNY PL can detect wavelength variation with an accuracy as high as ±0.5 nm and visualize variations in emission wavelengths within a wafer as color unevenness by converting differences in emission wavelengths from chip to chip into a mapping image. This enables more precise and efficient determination of wafer quality.


The emission spectrum can also be measured by using the optional spectroscopic analysis module.

Detect defects

Software for detailed analysis from Emission wavelength, PL intensity, and Appearance check.

The software for MiNY PL acquires and displays appearance and PL images. It also has the performances to enhance the accuracy of analysis such as analysis supporting various.

Features that increase analysis accuracy

  • Supports a variety of chip designs 
  • RGB-compatible measurement settings 
  • Guide function for quality judgment


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