[labnetwork] Crygenic Plasma Etching of Black Silicon

[Kevin M McPeak]

Dear Colleagues,

We have a user at the LSU Nanofab that has developed a recipe for etching black Si into 4" Si wafers at cryogenic temperatures  (-130 C) using our Oxford ICP100 tool. The user also wants to produce Black Si on small pieces, e.g. 1" x 1" Si pieces which are attached to an Al masked Si carrier wafer. He is currently using Fomblin oil as a heat transfer agent between the Si chip and the carrier wafer (3 - 4 drops). Unfortunately, the small chips are giving him patchy black Si, whereas the whole 4" wafers are very uniform.

I suspect this issue is related to heat transfer across the Fomblin layer. He is currently waiting 2 minutes after loading the carrier + Si chip before striking the plasma. 3 - 4 drops of Fomblin between the carrier and 1" x 1" chip.

Does anyone have experience with cryogenic etching of Black Si on chips? If so, I would very much appreciate your thoughts on best practices for achieving good heat transfer to the chips. Thanks in advance.

Regards,
Kevin

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Kevin M. McPeak
Assistant Professor | LSU Dept. of Chemical Engineering
225-578-0058 | mcpeaklab.com | lsu.edu/nanofabrication