New Ebeam process RE2: NEW THREAD PMMA's restocked today... chemicals stay in the SNF clean room...

James W. Conway jwc at snf.stanford.edu
Fri Jan 21 18:19:03 PST 2011


Ebeam Lab Users:

I have restocked the lab with both 5% 950K PMMA and 9% 950K PMMA this 
morning.

Where did the former bottles in the lab travel to?  Please return... 
No??Asked...

Note: While I have no problem if you need to coat a wafer or two for 
experiments in any lab any where else -- NO VOLUMES OF RESIST or any 
other chemicals are to leave the SNF clean room without approval.

Clear?

Have a great weekend,

James

On 1/19/2011 2:41 PM, Carter Lin wrote:
> Thank you James. Can you put some 5% 950K and 9% PMMA on the resist
> cabinet please?
>
> Best
> Carter
>
> On Tue, Jan 18, 2011 at 9:11 AM, James W. Conway<jwc at snf.stanford.edu>  wrote:
>> Hello Carter,
>> Dose is very dependent on acceleration voltage due to the penetration depth
>> and excitation volume into the sample.  Lower the Acc. voltage the lower the
>> doses.  Some effects are related to sidewall angle due to lower Acc. voltage
>> having effects from the back scatter range as well; this can be controlled
>> by careful dose-to-clear determination.  For 250 nm circles written as area
>> writes your dose on thick PMMA should be around 135 to 150 uC/cm**2 at 10
>> keV, and 160 - 175 uC/cm**2 at 15 keV.
>>
>> *** You will need to determine the proper dose for your non-standard film
>> thickness.  ***
>>
>> Higher acceleration dosages AT THE DOSE TO CLEAR and not overexposing will
>> render straight vertical side walls angles suitable for your processing.  In
>> fact I believe thinner thickness films 200 - 350 nm will work fine as well.
>> My recommendation is to expose using either single layer 300 nm of 5% 950K
>> PMMA or 5% 495K PMMA.  Attached are my 5% single layer processes for your
>> review.
>>
>> Best practice to prebake your thin films before plating at 90 degrees C for
>> 2 min. on hotplate to toughen up the resist and ensure suitable adhesion.

>> See me during office hours if you have any questions,
>>
>> James
>>
>> On 1/14/2011 9:18 PM, Carter Lin wrote:
>>
>> Hi James,
>>
>> I am planning to try a new process. Basically I want to use PMMA as
>> mask for electroplating some vertical nanopillars of 250nm diameter
>> and 1um in height. Here is the work flow I have in mind
>>
>> 1. coat glass substrate with Cr/Au as seeding layer
>> 2. spin 9% 950K PMMA to 1um thick
>> 3. write circles of diameter 250nm with 1500uC/cm^2 dose, develop
>> 4. electroplate Au to make pillars using PMMA as a mask
>>
>> I am writing to ask for your comments + suggestions, because I have
>> doubt on whether step 3 will work. The papers i read use 100kV
>> electron beams, but the max we can go with Raith is 30kV right? So
>> would that give a lot of scattering and leads to bad sidewall defined
>> for step 4? Meanwhile the dose seems to be 10x as high as the normal
>> dose we use. Will that be a problem?
>>
>> Thank you
>> Carter
>>
>>
>
>



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