Improvement of LED luminous efficiency by low finished sapphire substrate

Days ago, MicroTech has developed a wet processing workstation for preparation of patterned sapphire substrate, the workstation mass corrosion sapphire, increase light extraction and external quantum efficiency of high brightness LED. The wet etching process can increase the output to reduce the cost, and the production cost is the main obstacle to the competition between LED and fluorescent lamp. To reduce the cost of the LED manufacturers, the use of PSS substrate becomes very important, compared to the average light output power of PSS LED on the conventional sapphire substrate is increased by 37%, the use of PSS can not only reduce the dislocation density of GaN epitaxial layer, improve the light extraction efficiency of LED.

The traditional dry etching PSS patterned substrate is very effective to increase the efficiency of LED, but the yield is low and the controllability is affected by the increase of substrate size. In the wet etching process of MicroTech system is relatively simple, using PECVD deposited on the sapphire wafer on a layer of graphics SiO2 mask lithography exposure to etching pattern, then etching groove with wafer etching and immersion in the buffer. Gem etching process between 260 degrees and 300 degrees, the super high temperature than the conventional 150-180 C corrosion process of the etching rate is much faster, thus significantly increase yield. A neutral consumer evaluation shows that the PSS patterned substrate has a significant improvement in the light extraction and efficiency of LED, even after wafer polishing after etching, while the cost is also significantly reduced. The use of chemical mechanical polishing to improve the shape of the dome on the PSS wafer is in progress, while the development of new non conic shapes is also in progress.

Recently, MicroTech announced it would be similar to the concept of using corrosion workstation to the solar cell industry, to replace the traditional CVD process for dry wet process production, environmental friendly, to achieve high throughput and low cost.