The past
few years have seen a dramatic acceleration in microLED development. The
industry abounds with new companies focused on a variety of technical
challenges. Just this month, CES featured new microLED screens by some of the leading display
manufacturers. There is little doubt that microLED is poised to emerge as a
leading display technology in the coming years.
One of the
most fundamental challenges facing microLEDs, however, is inspection. The microLED
pixels that are currently being developed are on the single-micron scale. At
this size, sub-pixel defects can be as small as hundreds of nanometers. The
ability to identify defects at this scale is critical for the continued
development of microLED technology. In order for microLEDs to be a commercially
viable display technology, yields must improve dramatically. And the key to
improving yields, as always, is effective inspection.
Of course,
many inspection technologies already exist in the display market. In fact, most
display inspections are based on optical methods, such as AOI (Automated Optical
Inspection). However, optics-based inspection technologies are fundamentally
inadequate for microLEDs. Why does this
method of inspection, so effective with LCD displays for example, fall short
when it comes to microLEDs? The answer relates to a basic principle in optics
known as “the diffraction limit”. Practically, optical techniques tend to have
a resolution limit of approximately 1 micron. Therefore, as the pixel approaches
1 micron in size, and defects emerge on the nanoscale, less and less sub-pixel
information is effectively obtained via standard optical techniques.
Fortunately,
there is a technique which facilitates the continued employment of optics for
inspection – even for single micron pixels and 100nm defects. In 1984, InZiv Chief
Scientist Professor Aaron Lewis, then of Cornell University, demonstrated that
a much higher optical resolution can be achieved when light passes through a
sub-wavelength diameter aperture. The light illuminates a sample that is placed
within its near field, at a distance much less than the wavelength of the
light. The result is a resolution as high as 50nm (up to 20x times more
powerful!) Lewis’s work offered such a profound contribution to the
scientific community, that his student Eric Betzig went on to win the Nobel
Prize in Chemistry in 2014 for related work in super-resolution
microscopy.
Now, with
the advent of microLEDs and their sub-micron defects, this proprietary optical
technique is ideally suited to address the inspection needs of today’s display
manufacturers. Not only does InZiv’s inspection technology offer the highest
resolution in microLED inspection, it also offers a full range of data –
optical, spectral, and structural. EQE, PL and EL mapping, nano-PL and nano-EL
measurements, lifetime measurements, and sidewall measurements can all be
obtained. With the ability to measure ≤1 micron chips and to identify the
smallest defects, InZiv’s OmniPix-ML1000 is quickly emerging as a must-have
tool for microLED developers and manufacturers.
As the
microLED industry continues to move ahead, InZiv will be there to provide the
inspection solutions that are necessary for the unique challenges presented by
this exciting display technology.
