ALD in extreme conditions
The world’s most transparent display is enabled by ALD
We have talked about atomic layer deposition in industrial use on many occasions In this blog, but we haven’t yet written stories about the oldest and largest ALD use case of them all.
Industrial use of ALD started over 30 years ago in Espoo, Finland, in the Home of ALD, the factory which today is the Beneq headquarters and production facility. World’s first ALD-based commercial products were electroluminescent displays, which are now sold under our Lumineq display brand.
End of July at the ALD2016 conference in Dublin, Beneq’s Sami Sneck shared the incredible story of ALD-based Lumineq displays with the ALD community. Given the great feedback we got for the presentation, we figured the highlights are worth sharing in the blog too. The industrial ALD production in the Beneq factory is in many ways quite extraordinary.
Batch-based ALD in volume production
While Beneq has a multitude of customers who use Beneq ALD equipment for industrial production, no-one can match the production volumes and batch sizes of Lumineq display manufacturing in Finland. We have almost 20 ALD reactors currently in use in the display production. The batch size is 42 or 80 pieces of 195x265 mm glass substrates. Millions of ALD-based displays have left the factory since the 1980’s.
Multi-layer ALD with thickness of over 1,5 µm
Most ALD coatings we create are very thin (that is often the whole point), but when the equipment is fast and the process optimized, it is also possible to manufacture micrometer-level ALD films that are economically viable.
A Lumineq display has five distinct ALD layers (one ion barrier, two dielectric layers, an index matching layer, which also acts as a moisture barrier, and the actual electroluminescent phosphor layer) that are deposited with Beneq P400 reactors. The combined thickness of the ALD layers in each display is a whopping 1590 nm!
High-temperature ALD processes
The process temperatures we use in the ALD-based production phases in the display factory are extremely high. The ion barrier is deposited in 470°C and the dielectric layers and the phosphor in over 500 degrees. The source temperatures used for some of the chloride processes are also above 500°C, which is – to say the least – very unusual, especially for large-scale batch production.
From extreme conditions to extreme conditions
The ALD-based display structure is the foundation of the inherent ruggedness Lumineq displays are known for. Lumineq displays are used in very demanding applications, where they need to withstand shocks, humidity, extreme cold and wide temperature changes. The unique performance in extreme conditions would simply not be possible without ALD.
The transparent Lumineq TASEL displays, which are manufactured with the same ALD-based process, are the most transparent displays in the world. The high degree of transparency (over 80% transmission) is achieved by replacing the aluminum electrodes with transparent Indium Tin Oxide (ITO) electrodes. Using ITO requires a totally pin-hole free dielectric layer, which can only be achieved with an ALD coating.
For more fascinating facts and details about how ALD makes Beneq’s rugged and transparent electroluminescent displays possible, please download Sami’s presentation in full.