Hi Oray, everyone

You can use methane/hydrogen/argon to etch GaAs in ICP or RIE.  It does have
some disadvantages over chlorine containing mixtures.  It will operate at a
higher DC bias (which can leave ion bombardment damage on the etched
regions), gives a rougher surface and deposits carbon based deposits in the
chamber which have to be regularly cleaned to avoid particulates.  It has a
maximum etch rate of around 45nm/min in RIE.

Adding chlorine, either as Cl2 or BCl3 or SiCl4 avoids these problems but
then gives difficulties of handling toxic gases.  This means you must either
use a load-locked machine or use a glove box on an open load machine.  There
are other issues with gas lines, continuous monitoring for leaks etc.

Also, while CH4/H2/Ar will etch GaAs, it will not touch anything containing
Al (such as AlGaAs).

Feel free to contact me direct by email at [email protected] if you
need more information.

Martin

---------------------------
>
> Message: 3
> Date: Mon, 20 Sep 2004 19:10:43 +0300
> From: Oray Orkun Cellek 
> Subject: [mems-talk] RIE gases
> To: [email protected]
> Message-ID:
>       <[email protected]>
> Content-Type: text/plain; charset=iso-8859-1
>
> Dear Mems-Talk users,
>
> For safety reasons we plan to establish an RIE system that uses safe
> CH4/H2/Ar plasma for etching GaAs and other compund semiconductors.
>
> I wonder what is the disadvantage of this chemistry when compared to
> the popular and toxic BCl3 and SiCl4 ?
>
> Can you compare these in terms of etch rate and isotropy for an
> ordinary RIE system ?
>
> Does CH4/H2/Ar really demand RF supply systems like ICP or ECR ?
>
> Thank you in advance,
>
> Best Regards,
>
> Oray Orkun Cellek
> Research Assistant, Ph.D. Candidate
> Electrical & Electronics Engineering Department
> Middle East Technical University
> 06531
> Ankara, Turkey
> e-mail : [email protected]
> Tel : +90 312 210 4579
> Fax: +90 312 210 1261
>


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