Research/DRIE Wafer Fixed with DP Oil

DRIE of arbitrary shaped silicon wafer†

Most DRIE chambers are equipped with a 4-inch or 6-inch wafer holder, and arbitrary shaped wafer (after cleaving) must be mounted on a round carrier wafer. DRIE companies recommend heat grease to tentatively glue the wafer onto the carrier wafer but it is very difficult to remove the grease later. It sometimes breaks the MEMS wafer. In such case, use DP oil instead.

↑

Wafer fixed with DP oil†

First, de-gas the DP oil in vacuum to remove all air trapped inside. Use a Q-tip to smear the DP oil onto the carrier wafer (within the shape of the target wafer). Place your wafer and tape down the corners with kapton tapes. And just go to the DRIE.

Caution: Do not use fonbrin oil (that is usually used for a dry pump or mechanical booster); it becomes very solid after DRIE and it is incredibly difficult to remove.

↑

Wafer removal†

Using a transparent quartz wafer is good to see the result of etching from the backside of the wafer. When finished with DRIE, slide the wafer to the edge of the carrier wafer and drop it. Do not attempt to raise it.

↑

DP oil removal†

Do not dip the wafer into acetone but just place it onto a acetone-wet paper towel. Let it be absorbed in the towel, and repeat it a couple of times. This greatly helps not to get the DRIE-ed surface contaminated with the DP oil.

↑

Reference†

DP oil used in our work was from ShinEtsu Chemical: HIVAC-F series (http://www.silicone.jp/j/products/oil/search/straight2.shtml)
If you think this information useful, please refer in your publication by citing "Private communication with Prof. H. Toshiyoshi and his research group at the Institute of Industrial Science, the University of Tokyo (http://toshi.iis.u-tokyo.ac.jp/toshilab/). Thank you. Hiroshi TOSHIYOSHI