[labnetwork] Need help with RIE process

[Mac Hathaway]

Hi Rick,

That's definitely arcing.  Question is, when is it occurring...  It's 
been a while since I worked with electrostatic chucks, but as I recall, 
you can build up static charges on fully covered wafers, during plasma 
processes. The problems we used to see were that the wafer would stick 
along one edge when the lifter pins came up, and I think we could even 
see the arcing at the point of contact when the wafer finally "unstuck".

Do these wafers have oxide on both sides?.... Also, is there a window 
where you can watch the wafer during de-chucking?

What we used to do, if I remember correctly, was to run a weak argon (?) 
plasma at the end of the etch, which we called the "dechuck" step.  It 
took a bit of tuning to get it right.  You could even try keeping it on 
while the pins are coming up, to allow a discharge path behind the 
wafer, but that will be a function of your software, and hardware 
interlocks.  Lastly, sometimes this problem goes away if you just give 
the dechuck step more time, to allow excess static charge to bleed off.

As I say, it was a while ago, so there may be more recent approaches to 
incomplete dechucking that I'm not aware of.


Mac

Mac Hathaway

Senior Process and Systems Engineer

Harvard Center for Nanoscale Systems

11 Oxford St.

Cambridge, MA02138

617-495-9012


On 3/4/2015 7:08 AM, Morrison, Richard H., Jr. wrote:
>
> Hi everyone,
>
> I have a strange problem that I need some help with. We have an  Ulvac 
> NE-550 RIE system with an electrostatic chuck. The wafer is a double 
> sided polish with 1um of SiO2. One side has an AZ4620 resist pattern 
> 8um thick to etch the 1um of oxide. Because the process runs hot we 
> break the etch into 9 different steps and move into the LL after every 
> step. On the polished side that is down on the ESC check we have 
> craters on the surface that look like a lightning strike or meteor 
> strike, this is fairly deep several microns.
>
> I have attached a photo of the damage. Have any of you seen anything 
> like this? I need to fix the issue because the side that is down ends 
> up being the frontside of the wafer and that is a killer defect. We 
> think the oxide is charging and when the lift pins come up (at ground 
> potential) we get a discharge.
>
> Rick
>
> Draper Laboratory
>
> Principal  Member of the Technical Staff
>
> Group Leader Microfabrication Operations
>
> 555 Technology Square
>
> Cambridge Ma, 02139-3563
>
> www.draper.com
>
> rmorrison at draper.com
>
> W 617-258-3420
>
> C 508-930-3461
>
> ------------------------------------------------------------------------
> Notice: This email and any attachments may contain proprietary (Draper 
> non-public) and/or export-controlled information of Draper Laboratory. 
> If you are not the intended recipient of this email, please 
> immediately notify the sender by replying to this email and 
> immediately destroy all copies of this email.
> ------------------------------------------------------------------------
>
>
> _______________________________________________
> labnetwork mailing list
> labnetwork at mtl.mit.edu
> https://www-mtl.mit.edu/mailman/listinfo.cgi/labnetwork
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mtl.mit.edu/pipermail/labnetwork/attachments/20150304/ec0da824/attachment.html>