Tuesday, November 26, 2013

Dry Vs Wet Process - For Sapphire Etching


by Paul Drake


Dry and Wet Etching are two popular processes that are being used for the production of patterned sapphire substrate. Having said that, it makes sense to understand the difference between the two so that you can determine which particular process suits best to your unique needs. So, I have prepared below some sort of comparison between the two processes.

Dry etching

- the most popular method used by manufacturing companies to etch sapphire substrates and it has a very slow process with a low throughput rate;

- a standard 2-inch wafer can consume between 30 and 60 minutes to etch;

- experts say that it does not scale effectively; as wafer size increases, throughput of a dry etcher falls because fewer wafers fit inside the vacuum chamber. This results to the use of more expensive plasma etching tools to attain the same throughput as achieved using smaller wafers;

- the dry etching rates range between 50nm and 200nm per minute;

- dry etching creates bright and efficient LEDs but the process takes it so slow and limited throughput.

Wet etching

- it has the advantage of being an extremely fast process and it can be carried out in a lot cheaper procedure than dry etching;

- it is very scalable but produces LEDs that are not quite as effective or efficient as dry etching;

- wet etching process provides a cost-saving advantage compared to dry etching;

- in a wet etching process, the etcher needs to perform a polishing touch-up on the wafers to improve the light extraction efficiency.

Sample of equipment utilized in sapphire etching process:

The Accubath Xe-Series -- used in wet etching process; an etching bath equipment developed by Imtec Acculine with Sapphire etching in mind. This particular tool has been proven to be a great help in semiconductor manufacturing as this tool helps to process substrate in a fast manner and improves the processes that were previously thought to be too slow because of temperature constraint.

Hitachi High-tech Silicon Etch System -- this equipment is capable of generating a stable high density plasma at a very low pressure; it is utilized in dry etching based on an ECR (*1) plasma source.

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.




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