Sapphire Etching - Dry vs Wet Process

There are two popular etching processes being used to produce pattered sapphire substrate - the dry and wet etching. It is imperative to know the differences between the two so that a manufacturing company is able to determine which between the two is better. To help you with that, I have prepared below some points of comparison:

Dry etching

• considered to be the most common method to etch sapphire substrate productiona very slow process with a low throughput rate; 
• a standard 2-inch wafer can consume between 30 and 60 minutes to etch. 
it does not scale effectively. As a wafer size increases, throughput of a dry etcher falls as fewer wafers fit inside the vacuum chamber. And because of that,  more expensive plasma etching tools are needed to achieve the same throughput as was achieved on smaller wafers.
• as an estimate, dry etching rates range between 50nm to 200nm per minute is attainable.
• it creates bright, efficient LEDs but does so slowly and with limited throughput

Wet etching

• is known to provide dual advantages of being extremely fast and a lot cheaper than dry etching
• it is very scalable but produces LEDs that are not quite as effective or efficient as dry etching.
• it provides a considerable cost saving than the dry etching
• polishing touch-up work is performed on hte wafers in order to increase light extraction efficiency

Some equipment used in etching process:

• The Accubath Xe-Series -- an etching bath equipment from Imtec Acculine, was designed with Sapphire etching in mind but we know there are other processes that will benefit from the increased chemical reactivity that higher temperatures provide (300°C). Processes that were previously thought to be too slow due to temperature limitations may now be practical because of innovations like this.
• Hitachi High-tech Silicon Etch System -- this equipment is used in dry etching based on an ECR(*1) plasma source, it is capable of generating a stable high density plasma at a very low pressure.
• CDE-80N Chemical Dry Etching Equipment -- Performs chemical dry etching of thin film on a semiconductor wafer in gaseous state (dry). Damage-free etching process through perfect separation of the etching unit and plasma generating unit enables wide use in the damage removal process.

Each of the etching processes discussed above has its own advantages and disadvantages. But, just like any other processes, select the one you think can improve your bottom-line -- profit.