At the Society for Information Display’s Display Week, being held this week at the Henry B. Gonzalez Convention Center here, Corning revealed the latest iteration of its silicon on glass (SiOG) technology. With SiOG, Corning transfers a thin film of single-crystal silicon from a 300-mm silicon wafer to a substrate of display glass and bonds the silicon film to the glass substrate. The SiOG substrate can then be used by a panel maker to make the thin-film-transistor backplane for an active-matrix display.
Senior Analyst and Editor
Corning first announced this technology two years ago, but at that time the implementation looked more like a physics experiment than a key component for a display manufacturing process. That has now changed. Corning showed its SiOG material on a Gen 2 substrate, and expects to scale it to Gen 4 by the end of the year.
The size of each section of single-crystal film is limited by the size of the silicon wafer it comes from, so a substrate must by coated in sections. (See photo.) This also means the process is highly scalable. Eric Mozdy, SiOG Product Line Manager, told me there is no reason the process can’t be scaled to Gen 8. The main limitation is the decision to buy the equipment to implement the process on the larger substrates.
So why is this a potential game-changer for AMOLED displays? Currently, commercial AMOLED displays use low-temperature polysilicon (LTPS) for their backplane material. The most widely used LTPS processes are currently limited to half of a Gen 4 substrate at a time, and have significant uniformity and cost issues. People would like to use amorphous silicon, but there are serious stability issues when a-Si is used with current driven OLEDs rather than voltage-driven LCDs. The SiOG process would permit the fabrication of stable OLED pixel switches with higher yield and much greater performance than LTPS, and on larger substrates.
That sounds great, but what about cost? Mozdy said that when you look at the downstream savings — that is, that the panel maker can eliminate the LTPS process, obtain higher yields, and be able to use the single-crystal silicon for integrating high-performance circuitry on the display substrate — the overall cost of using SiOG could be less than the current process. Some panel makers are experimenting with SiOG now, and we could see prototype displays before the end of the year.
There are other solutions, real and potential, for parts of the backplane problem, but Corning’s is particularly elegant. It is also elegant from Corning’s perspective in that it transfers significant value from the panel maker to the glass maker, while reducing overall cost to the panel maker — if Corning’s projections are correct.