Hello everybody, I would like to know, if it is possible to etch Al2O3 with RIE with SF6 ? can you also achieve higher etching rates with SF6 ? or do i have to use another gas to achieve higher etching rate on Al2O3 ?
Does anyone already have experience with the etching of Al2O3 with the RIE system? thanks in advance
Hi Khalid,
Normally, F radical sources such as CF4 have an etch rate on Al2O3 material. the byproduct is in the form of AlF. I do not see any issue when one gas that supplies the F radicals (CF4) will etch alumina whereas the other one wont (SF6). The only thing I would consider here would be the dissociation coefficient of SF6. Say if SF6 is heavier tp dissociate than CF4 then etch rate would be normally lower. In case if a source gas is easier to dissociate and yields a higher density of F radicals, it can lead to a more anisotropic etching. It depends on your tool configuration. in case its a traditional RIE tool where you do not worry too much about the CD control and verticality, then try using the following parameters: 100 sccm SF6, RF:200W-500W, P: 500-700 mTorr, T:25oC. This can be a starting point. Thanks, hope this helps.
Hello Salman,
many thanks for your response. unfortunately the gas CF4 is not available at the moment. Thanks for the initial parameters that you wrote to me. I can adjust all parameters, except the pressure, why should the pressure, with high pressure i think we will have more deposition than etching ? Usually I can etch A2O3 with SF6 and achieve maximum etch rate of around 40nm/min. have you already etched Al2O3 with CF4 and measured the etching rate? Do you know what kind of chemical reactions occur during the process?
thanks
HI Khalid.
What I meant was that you just need a source of F radicals. I guess some sort of AlxFy would be generated as by-product of the etch process. any gas like CHF3, CF4, SF6 can in principal etch alumina, I think the byproduct will always be some sort of AlxFy and it s a non-volatile stuff so yes you are right there will be more deposition than etching. I have not tried any CF4 or SF6 etch of alumina. I would say the best option is to try Cl containing gases like BCl3/Cl2/Ar as AlCl3 is volatile. As I said, technically yes you can etch alumina with F chemistries however the byproducts are to be considered and the gas lines that you mentioned you had, the parameter set I suggested would be a starting point. Best is to use Cl based processes rather than F. I hope this helps.
Hi Khalid,
Further to my previous reply, I think the only best bet you have to etch away Alumina is to do a pure physical etch with your Ar gas. As I said, the F based gases would lead to non volatile product AlF and at some point it will just stop your etch process. If you increase your RIE power to the max, and use just Ar this will provide some level of etching. Please bear in mind the damage that your wafer will incur due to sputter effect.
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