I would like to structure a CsI layer of 200 um thickness. How could I do that? Is Reactive ion etching an option? CsI is very sensitive for water, so wet etching is no option.
It should be possible with a mixture of CF4 and Ar+. There is information on this in scientific literature. I do not know how well it will work for such thick layers, though.
Other ways to obtain structured CsI(Tl) scintillators are growth and, a rather novel and apparently supreme method, filling of micro-pores (See Linnros group and Scint-X company in Stockholm, Sweden).
CsI is readily etched in CF4 Plasma. Highly anisotropic profiles can be etched. There is some work carried out in Tufts Plasma Engineering Lab. To etch 200 microns, I don't think RIE is a good idea because of slow etching rates usually in RIE.
I confirm...CsI can be easily etched by CF4 plasma creating a volatile by-product CF3I and solid carbon that participate In the formation of a passivation Layer ( composed of C, Cs, and F) . Of course to avoid the etching stop and reach anisotropic profiles, one need to remove the passivation layer at the profile bottom while keeping it on the edge ..,For that BIAS is necessary (and physical assistance can help: Ar) . This etching mechanism is nevertheless very low ...to improve this, one need to have a dense plasma (For that use ICP Or TCP reactors instead of simple RIE ) and help solid carbon to desorb gaseously by warming up the wafer.
Regards
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