New material request: polystyrene microspheres in aqueous suspension
ahryciw at gmail.com
Mon Oct 22 09:12:58 PDT 2007
I've been talking with James Conway during Raith training, and he has told
me that unfucntionalised latex microspheres are actually not a new material
for SNF, since they are already used in the e-beam lab, etc. As such, I
assume that there is no problem with my using the spheres in the lab, so
long as the rest of my process is compatible with SNF procedures.
On 10/10/07, Aaron Hryciw <ahryciw at gmail.com> wrote:
> Dear SpecMat Committee –
> Please regard this email as a request for a new material for use at SNF; a
> general MSDS for this class of materials (from the chemical supplier from
> whom the material has been purchased) is attached.
> Contact information*
> Aaron Hryciw
> Coral login: ahryciw
> Phone: 3-5840 (office); (650) 353-0347 (cell)
> ahryciw at stanford.edu
> PI: Mark Brongersma (Mat. Sci. Eng.)
> * Chemical or material name*
> Polystyrene microspheres (diameters between 100 nm and 1 um) suspended in
> DI water, 10% solids by weight, 15 mL vials.
> MSDS from supplier attached.
> Will be diluted with methanol or ethanol before use.
> Common/trade names: polymer microsphere suspension, polystyrene
> microspheres, polystyrene nanospheres, latex microspheres suspensions.
> Storage group identifier: *G*. Non-Reactive Materials and Non-Hazardous
> Main hazard class: 11. Non Hazardous.
> *Vendor/manufacturer info
> *Duke Scientific Corporation
> 2463 Faber Place
> P.O. Box 50005
> Palo Alto, CA
> Phone: 1-800-334-3883 or 1-650-424-1177
> Fax: 1-650-424-1158
> info at dukesci.com
> www.dukescientific.com (in particular: http://22.214.171.124/www.dukescientific.com/pages/pagefb6d.html?s=979&ss=984&t=1007
> Reason for request
> *My interest in polystyrene microspheres is due to their use as a
> self-assembled monolayer mask, as a means of fabricating large (~cm^2) arrays
> of silicon nanowires (NWs) with controlled size, length, and areal density
> (please refer to Huang et. al, attached). Nanosphere lithography (NSL)
> comprises a rapid, parallel approach to fabricating well-controlled NWs
> without requiring conventional photolithographic techniques. The material
> used for the mask (viz., the polystyrene microspheres) is also very benign
> and poses no health or safety hazards when used properly for this technique.
> * Process Flow*
> I intend to follow the general process flow detailed in the attached paper
> ( Huang et. al). if necessary, the entire process flow needn't occur in
> SNF (only use of the RIE tool is strictly required), although, for the sake
> of cleanliness, I would prefer it.
> A full process flow in SNF would be as follows:
> 1. Clean (100) n-type Si wafers or pieces (ca. 1x1 cm^2) in an
> ultrasonic cleaner using acetone (10 min), then methanol (5 min).
> 2. Clean in Piranha (4:1 v/v H2SO4:H2O2) and RCA solution (1:1:5
> v/v/v NH3:H2O2:H2O @ 80 °C) for 1 hr.
> 3. Rinse in DI water.
> 4. Place substrate in a Petri dish (I will have my own dedicated
> glassware) and cover with DI water.
> 5. Pipette polystyrene microsphere solution (5% solids in 15 mL DI
> water + 15 mL methanol) onto water surface and gently tilt Petri dish to
> encourage self-assembly of large single-crystal hcp arrays.
> 6. Allow water to evaporate slowly, depositing microspheres onto
> substrate. [The foregoing six steps could be performed at wbgeneral,
> wbmetal, or wbnonmetal, as necessary.]
> 7. RIE microsphere array to desired sphere diameter using O2 plasma
> etch: 40 sccm, 30 W RF power, 5 Pa pressure. [Performed on one of the
> drytek tools, consistent with previous material groups.]
> 8. Deposit 40 nm of Ag. [innotec or metallica]
> 9. Etch Si NWs in an etchant consisting of HF (4.6 M) , H2O2 (0.44M), and H2O. [wbgeneral]
> 10. Remove microspheres by soaking in toluene for 2 hr. [wbsolvent]
> 11. Remove Ag film by soaking in nitric acid for 15 min. [wbgeneral]
> If necessary, steps 1–6 and 7–11 could be performed outside SNF (in our
> lab in McCullough Bldg., for instance).
> *Amount and form
> *Two or three 30-mL vials containing microspheres (of two or three
> different sizes) suspended in 15 mL DI water + 15 mL methanol. Once the
> 15-mL DI-water-suspended material (as purchased) has been diluted with
> methanol, no further mixing will be required.
> If the entire process flow is approved for use in SNF, I would store the
> vials of microsphere aqueous/methanoic suspensions at SNF. If only step 7
> is approved for SNF, I would store them in our group's lab.
> As per the MSDS, waste materials containing microspheres could be
> disposed of in SNF's hazardous materials bins in a sealed, labeled plastic
> bag, due to their non-hazardous nature.
> Thank-you for considering this new material for use at SNF. I would enjoy
> the opportunity to discuss possible amendments to the abovementioned process
> flow if necessary to allow it in the cleanroom.
> Best regards,
> – Aaron
> Aaron Hryciw
> Postdoctoral Scholar
> Geballe Laboratory for Advanced Materials
> Stanford University
> 476 Lomita Mall (04-490)
> McCullough Building, Rm. 325
> Stanford, CA 94305-4045
> Tel.: (650) 723-5840
> Fax.: (650) 736-1984
Geballe Laboratory for Advanced Materials
476 Lomita Mall (04-490)
McCullough Building, Rm. 325
Stanford, CA 94305-4045
Tel.: (650) 723-5840
Fax.: (650) 736-1984
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