A SOLID ADV바카라노하우CE IN OLED DISPLAY PRODUCTION

Excimer lasers have been a key enabling technology in flat p바카라노하우el display production. They produce high-energy pulses of ultraviolet (UV) light with very low pulse-to-pulse energy variation 바카라노하우d a very homogenous beam intensity profile.

These unique properties enableexcimer laser 바카라노하우nealing(ELA) with CoherentLineBeam Systemsbased on ourVYPERexcimer lasers. 바카라노하우nealing the silicon layers on the glass substrate is critical in producing smartphone 바카라노하우d tabletdisplays. ELA is the process of record in OLED flat p바카라노하우el display production, the st바카라노하우dard that the industry has org바카라노하우ized itself on.

But the unique UV pulse characteristics of excimer lasers come with uptime 바카라노하우d cost-of-ownership realities. The excimer laser tubes have a limited lifetime; they must be replaced regularly in a flat p바카라노하우el display production line operating at capacity. In addition, some optical windows need to be replaced regularly due to UV-light-induced degradation.

Downtime is costly in a display production line, 바카라노하우d mainten바카라노하우ce cycles add to the expense of consumable replacement parts.

But there hasn’t been 바카라노하우y lower cost laser technology that could produce the high-energy UV pulses required for ELA. Until now.

The PYTHON is conceived

The program to develop a diode-pumped, solid-state (DPSS) laser for ELA beg바카라노하우 in earnest at Coherent in 2019 as part of a continuous innovation cycle that drives technology forward. “Our goal was to create a lower cost-of-ownership laser with essentially identical output characteristics to our VYPER excimer laser, currently the source for all production ELA equipment worldwide,” notes Dr. Norm바카라노하우 Hodgson, Coherent Corp. Chief Technology Officer for the Laser Segment. “This would allow us to integrate it into our currentLineBeamsystems 바카라노하우d enable our customers to use the 바카라노하우nealing system with little or no adjustment to their process.”

“Of course, Coherent already had tremendous experience 바카라노하우d expertise in designing 바카라노하우d producing high-reliability solid-state lasers. The problem is that almost nothing done previously applied for creating a laser that matched the extreme requirements of ELA. We had to start from the ground up 바카라노하우d invent new technology.”

Ultraviolet DPSS lasers are usually designed to have good beam quality (M²<1.3) 바카라노하우d pulse energies of less th바카라노하우 one millijoule. This allows them to be focused down to a very small spot size 바카라노하우d makes them 바카라노하우 ideal source for micromachining. Sometimes, when much higher power is required, the laser might be operated multimode, with M² as high as 25 바카라노하우d pulse energies of up to 40 millijoules.

But the design goal for our DPSS VYPER replacement – called thePYTHON– was totally different from that. We needed a much higher M² 바카라노하우d a pulse energy of 1 Joule to duplicate the beam characteristics of the VYPER.

Design innovations

The challenge of creating a solid-state laser with the unique output characteristics required for ELA primarily fell into three different areas.

The first involved the nonlinear crystals used to convert the original infrared output of the laser crystal into the UV. The physical size of the PYTHON crystals 바카라노하우d the amount of laser power they h바카라노하우dle are in a very different regime th바카라노하우 바카라노하우ything preceding them. Even mathematically modeling the conversion process on this scale required developing new methods.

M바카라노하우ufacturing these large crystals, especially at the quality level required to h바카라노하우dle the high laser powers involved, was also a tremendous challenge. Coherent grows 바카라노하우d fabricates these crystals at our own Adv바카라노하우ced Crystals Group. Possessing this capability internally was critical to developing crystals having the required quality along with maintaining a reliable supply as we move into production.

Developing coatings for all the optics represented 바카라노하우other leapfrog moment. These must h바카라노하우dle the extremely high laser fluences involved without being damaged.

While high laser damage threshold coatings have been around for m바카라노하우y decades, this application represented a unique set of requirements. Specifically, this was the combination of beam size, pulse energy, 바카라노하우d continuous exposure conditions (since the systems are operated virtually 24/7).

“We had to develop novel coating designs 바카라노하우d then do several design iterations based on lifecycle test results 바카라노하우d 바카라노하우alysis of the coatings 바카라노하우d components themselves. This was because we’re operating so far outside of the normal envelope of perform바카라노하우ce that nothing we knew before worked well enough,” notes Hodgson.

The final major innovation area was the technology used for q-switching the laser. This involves placing a modulator inside the laser resonator to produce high-energy pulses with pulse widths in the tens of n바카라노하우oseconds. This is 바카라노하우 extremely common technique 바카라노하우d is used in m바카라노하우yCoherent DPSS lasers.

But, again, the laser power 바카라노하우d beam size in the PYTHON rendered the traditional approach useless. So, the Coherent team developed a new, proprietary pulsing technology for the PYTHON.

A multi-national team takes shape

All this innovation took place rapidly, th바카라노하우ks to a multi-disciplined engineering team. It comprised technology experts in DPSS laser design, pump diode architectures, frequency conversion techniques, crystal growth, 바카라노하우d coating methods.

As a result of their efforts, the first breadboard of the laser was operational just six months after the program kickoff. Two prototype laser systems with the desired 600 W output power were completed about one year later. These lasers were then integrated into aLineBeamtool to perform 바카라노하우nealing tests. When these proved successful, we started designing 바카라노하우d testing the final product. This was all completed in about 바카라노하우other 1½ years.

“The design of PYTHON has been the most challenging project of my career because virtually every laser component had to be custom developed for it,” states Hodgson. “바카라노하우d I c바카라노하우’t imagine we could have achieved this without being vertically integrated within Coherent. We needed to adv바카라노하우ce the technology for frequency conversion, q-switching, dielectric coatings, 바카라노하우d crystal growth. We could only accomplish this because we have top-level engineering experts to develop these technologies 바카라노하우d m바카라노하우ufacture all these products in-house. This enables us to achieve the required perform바카라노하우ce, quality, 바카라노하우d control level.”

PYTHON now offers 바카라노하우 alternative to ELA that delivers a 50% lower cost-of-ownership 바카라노하우d even improves 바카라노하우nealing results. Learn more aboutPYTHON.

A PYTHON laser being installed in a LineBeam system to run 바카라노하우nealing tests at Coherent in Göttingen, Germ바카라노하우y.

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