Friday, November 29, 2013

Sapphire Etching - Dry Vs Wet Process

By Paul Drake


In patterned sapphire substrate manufacturing, there are two popular processes that are being used my many semiconductor companies - the Dry and the Wet process. And because these processes differ in many ways, it is important to understand the difference between the two so that you can determine which between the two suits best to your unique needs. Consider the following:

Dry etching

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

- Etching a standard 2-inch wafer can take 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;

- as an estimate, dry etching rates range between 50nm and 200nm per minute is attainable;

- dry etching is also known in producing bright and efficient LEDs; however, the process takes so slow and produces limited throughput.

Wet etching

- is known to provide dual advantages of being extremely fast and a lot cheaper than dry etching;

- the LEDs that are produced using wet etching process are not as efficient and effective as that of the dry etching process; however, it is very scalable.

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

- polishing touch-up work is performed on the wafers in order to increase light extraction efficiency.

Here are some equipment being used in etching sapphire:

The Accubath Xe-Series -- designed to perform a wet etching process; this etching bath equipment has been proven to be a great help for semiconductor manufacturers as it helps improve the processes that were previously thought to be too slow due to temperature limitations. This equipment is developed by Imtec Acculine.

Hitachi High-tech Silicon Etch System -- a dry etching that is based on an ECR(*1) plasma source, capable of generating a stable high density plasma at 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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