Thank you for responding.
We dilute 50 ml BOE with 2000 ml DI and pour away mixed BOE and DI until we
get about 50ml or less. And we do the same dilution more than 5 times. Then
the sample in less than 50 ml DI water is diluted with 1000 ml of metahnol
and keep the same dilution mora than 5 times.
Is this enough? Is there any other way of diplace BOE and DI completely with
methanol?
We also use extra dry CO2 not the spectrocsopy CO2.
We'll try to use the spectrocsopy CO2.
Please give me more processing tips.
Thanks.
=================================
Sang Won Park
Graduate Research Assistant
Electrical Engineering
The University of Texas at Dallas
Phone) 972 - 883 - 2893
Fax) 972 - 883 - 6839
----- Original Message -----
From: "Henry Yang" 
To: 
Sent: Friday, April 12, 2002 11:12 AM
Subject: Re: [mems-talk] Critical point drying.


> How are you rinsing the BOE? Are you sure that you have displaced the BOE
> completely with DI and then Methanol? Seems like you are pretty careful
> with rinsing but that would be my first suspection.
>
> Another guess is that the flushing of Methanol with CO2 is not complete.
At
> UCLA we used to flush the chamber about 10-15 times (Roughly 20 minutes)
> continuously. You are only flushing for a total of 6 minutes.
>
> What grade of CO2 are you using? Some grades come with a bit of oil. They
> will cause stiction as well. Try spectroscopy grade CO2.
>
> The haze in the chamber is not that big of a deal assuming that there is
> only CO2 present. They might just be localized inhomogeniety. We used to
> seem them in our Polarion chamber.
>
> Good luck.
>
> Henry Yang
> IBM Almaden Research Center
> 408-927-2319
>
> "Sang Park" @memsnet.org on 04/11/2002 10:27:56 AM
>
> Please respond to mems-talk@memsnet.org
>
> Sent by:    mems-talk-admin@memsnet.org
>
>
> To:    
> cc:
> Subject:    [mems-talk] Critical point drying.
>
>
>
> Hi, all.
> I am using the SPI critical point drying apparatus form PSI supplies
> (division
> of Structure Probe, Inc.) to release comb-finger structures (0.5um wide,
> 0.5
> um thick, and 10um long) on 1 um thick SiO2 on a Si substrate. I usually
> use
> Buffered Oxide Etchant to remove SiO2 under comb-finger structures to be
> released without any atiction problem. After I put my sample in the ample
> boat
> with methanol, I load the boat into the critical point drying apparatus.
> Then
> I flush with CO2 for about 3 minutes and wait for 30 minutes for methanol
> and
> CO2 to be mixed well. And I do flusing agian for 3 minutes and the
> apparatus
> is heated up above 35C with the pressure of more than 1300 psi. After I
> wait
> for 10 minutes or so, I vent the CO2 gas.
> But there is the point I have a problem. While I'm venting the CO2, I
> notice a
> little haze generated and that can be seen by my own eyes.
> After finishing the venting and taking out the sample, I noticed some
parts
> are o.k., but some parts, especially the end of suspended structurs, are
> stuck
> to the substrate.
> Please send me any processing tips to solve this problem.
> Thanks.
>
> =================================
> Sang Won Park
> Graduate Research Assistant
> Electrical Engineering
> The University of Texas at Dallas
> Phone) 972 - 883 - 2893
> Fax) 972 - 883 - 6839
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