Fwd: anisotropic sputter etching of ZnSe/GaAs in MRC tool

Ed Myers edmyers at stanford.edu
Tue Apr 24 16:48:15 PDT 2007


Kristiaan,

The SpecMat committee met today to review your request.  There is 
significant concern due to the health implications highlighted by the 
MSDS for selenium.  When a compound has multiple statements about 
being toxic when inhaled we are extremely reluctant, since we do not 
want any potential for an exposure.

If this request is to move forward we will need more detail, such as 
the thickness of the layer you are etching and how often you 
anticipate performing this etch.  In addition we have to determine if 
we can safely recover the tool once selenium is introduced in to the chamber.

Regards,
Ed



At 02:28 PM 4/24/2007, kdegreve at stanford.edu wrote:
>Dear Madam or Sir,
>
>would there be any information available yet about the request I had
>submitted April 5th regarding sputter etching of GaAs/ZnSe in the MRC
>tool? This process would be very important for us, any help is already
>much appreciated.
>
>Many thanks and best regards,
>
>Kristiaan De Greve, PhD candidate, EE department, Yamamoto group.
>
>----- Doorgestuurd bericht van kdegreve at stanford.edu -----
>     Datum: Tue, 17 Apr 2007 10:58:05 -0700
>       Van: kdegreve at stanford.edu
>Antwoorden aan:kdegreve at stanford.edu
>  Onderwerp: Fwd: anisotropic sputter etching of ZnSe/GaAs in MRC tool
>       Aan: SpecMat at snf.stanford.edu
>       Cc: kdegreve at stanford.edu
>
>Dear Madam or Sir,
>
>would there be any information available on the status of the request
>(sent in Thursday April 5th)?
>
>Many thanks and best regards,
>
>Kristiaan.
>
>----- Doorgestuurd bericht van kdegreve at stanford.edu -----
>      Datum: Thu,  5 Apr 2007 23:27:43 -0700
>        Van: Kristiaan De Greve <kdegreve at stanford.edu>
>Antwoorden aan:Kristiaan De Greve <kdegreve at stanford.edu>
>   Onderwerp: anisotropic sputter etching of ZnSe/GaAs in MRC tool
>        Aan: SpecMat at snf.stanford.edu
>        Cc: kdegreve at stanford.edu, sanaka at stanford.edu
>
>Dear Madam or Sir,
>
>after having discussed with Jim McVittie about the possibility of doing
>anisotropic etching/sputter etching-ion milling at Stanford, I would like
>to file a request to use the MRC Argon plasma.
>
>The basic thing I am looking for is anisotropic etching of ZnMgSe (up to 18%
>Mg) MBE grown epilayers on GaAs substrates, in order to make freestanding
>mesas and microdisks. Mesas and microdisks (resp. sizes: 50-200 nm and ~1
>um) are lithographically defined by e-beam writing on negative e-beam
>resist layer of ~ 200 nm (MAN 2403).
>
>In the official SpecMat form:
>
>1) name: Kristiaan De Greve, kdegreve in coral, 650 283 0803 (cell),
>kdegreve at stanford.edu, EE PhD student in Yoshi Yamamoto's group.
>
>2) * material: zincselenide(ZnSe)/zincmagnesiumselenide(ZnMgSe, ~18% Mg)
>heterostrocture, epilayer (~80nm) on GaAs substrate, small pieces of 3x4mm;
>covered with developed MAN2403 negative e-beam resist
>     * main hazards: - GaAs: toxic when inhaled/swallowed, possibly
>carcinogenic, http://www.wafertech.co.uk/msds/msds_gaas.html for the MSDS
>                     - ZnSe: toxic when inhaled, swallowed,
>http://ptcl.chem.ox.ac.uk/MSDS/ZI/zinc_selenide.html for the MSDS
>
>     * storage group: it's not really a chemical, I don't see any category
>under which it would fall
>
>3) 'supplyer': MBE grown at the university of Paderborn, Germany, by Dr.
>Alex Pawlis in the group of prof. Klaus Lischka (apawlis at mail.upb.de)
>
>4) reason for request: in order to isolate small ZnSe mesa structures, we
>need a dry etching (preferrably) or sputter etching process that can
>anisotropically transfer patterns written into negative e-beamresist into
>the ZnSe/GaAs; the mesa height is about 100 nm, i.e. into the GaAs
>substrate.
>
>After talking with Jim McVittie, the option of sputter etching was withheld
>(the alternative, dry etching in the PQuest - a tool initially purchased by
>the Yamamoto group! - meeting resistance from GaAs III-V laser processors
>who fear contamination of Zn into their processes). As the Ar plasma is
>essentially non reactive, this tool has been used in the past for ion
>milling/sputter etching of all kinds of materials, including Zn compounds.
>
>No other tools are available for anitropic etching of these ZnSe epilayers;
>wet etching loses quite some resolution, and the MRC plasma, although
>second to the PQuest, would be of tremendous help with our experiments.
>
>5) process flow: - spin coating of MAN 2403 resist, 3000 rpm 30s, curing
>                     @90deg C, 1' @Ginzton cleanroom (3x4 mm pieces)
>                   - e-beam writing in Raith 150, 360 uC dose, 10 kV
>                     acceleration voltage
>                   - development of MAN resist in MaD532, 30s, rinse with DI
>                     water
>                   - sputter etching in MRC, negative e-beam resist as mask
>                   - resist stripping in MAN resist stripper (remover 1165)
>                     in Ginzton cleanroom
>
>6) amount and form: 3x4 wafer pieces, 3-4 pieces in a run
>
>7) storage: in sample holders and subsequently vacuum chambers in Ginzton
>labs
>
>8) disposal: these samples are actively measured and remeasured (optical,
>cryogenic experiments); left-over pieces are disposed of as hazardous waste
>in Ginzton labs.
>
>Many thanks and best regards,
>
>Kristiaan De Greve.
>
>----- Einde doorgestuurd bericht -----
>
>
>
>----- Einde doorgestuurd bericht -----





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