The use of flat displays is already standard in many homes, offices and in the industry today. No matter in which area you find your application, they are the most important interfaces between man and machine. The most widely used representatives of their kind today are the Active Matrix Liquid Crystal Displays (AMLCD) and organic light emitting diodes (OLEDs), whose market has been growing steadily since 2007.

 

 

One of the global players is certainly the company SAMSUNG and LG. For the manufacturers of flat screens, it is particularly important to use inexpensive glass substrates coated with poly-crystalline silicon (p-Si) (from which TFTs are made). The use of pulsed excimer lasers, which melt the silicon for a short time while the thermal limits of the glass substrate are not hurt,is especially good for that. The most commonly used laser in the literature is the XeCl Excimer laser with one wavelength of λ = 308 nm. The radiation penetrates at this wavelength only a few nanometers into the silicon surface. In the display industry it is crucial to work with formation of the largest possible and defect-free crystallites with little variation in the statistical size distribution over the entire substrate. Since the processing, by the glass substrate, is thermally limited to about 500-650 °C, Today, the so-called low-temperature crystallization process (Low Temperature Poly Silicon Technology = LTPS) are applied. This method can be great realized  with an Excimerlaser. As the demands of the display manufacturers grow, it is endeavored to expose larger and larger substrates. Since one depends on a constant energy density in the annealing process, it clear that with the enlargement of the substrates the Energy of the laser must rise. Since it is technically very complicated to increase the energy provided by an Excimer-Discharge unit, it is close to use two or three couple of several discharge units. This strategy is also pursued by Coherent and represented in their product range: LineBeam 750 (VYPER), LineBeam 1000 (TwinVYPER) and LineBeam 1500 (TriVYPER). The flagship of the company is the TriVYPER; an energy output of 6000 mJ and consists of 6 laser subunits or 3 VYPER subunits. The biggest challenge is to synchronize all laser discharge units. The company has also succeeded. The synchronization of the laser subunits is in the single-digit range of nanoseconds. Since the properties of an Excimerlaser by itself are not exactly
characterized by homogeneity in the energy distribution, it is essential to use for the six laser beams (in the case of TriVYPER, for example) an optical system. This function is realized by the so-called Beam Delivery System or LineBeam. Here are the rays mixed and homogenized through different optics and geometries, so that finally in the exposure chamber we use a homogeneous UV 308 nm radiation.

 

Watch "Smart phones, tablets and TVs from AMLCD to OLED". Take a look at Coherent's vision for the future with excimer laser annealing at the heart of it.

Coherent ELA (Excimer Laser Annealing)