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Sabtu, 30 November 2013

Sapphire Etching - Dry Vs Wet Process

By Paul Drake


There are two popular etching processes being used to produce patterned 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

- the most common method to etch sapphire substrate and is considered to be a very slow process with a low throughput rate;

- the time to etch a standard 2-inch wafer is between 30 and 60 minutes;

- 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;

- dry etching rates range between 50nm and 200nm in a minute (an estimate by some experts);

- it creates bright, efficient LEDs but does so slowly and with limited throughput.

Wet etching

- wet etching process provides the advantage of being extremely fast and it comes a lot cheaper than dry etching;

- it produces LEDs that are not quite as efficient and effective as the dry etching process, however it is very scalable;

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

- in wet etching, a polishing touch-up work is done on the wafers so that light extraction efficiency is increased.

Some equipment used in 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 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 -- used chemical dry etching process for thin film in a gaseous state semiconductor process. 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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