Change in STS etch chiller temperature

Eric Perozziello eap at gloworm.Stanford.EDU
Thu Mar 20 13:00:27 PST 2003

Please keep in mind that the temperature was mistakenly changed
a few months ago.  It is back to the manufacturer's recommended
temperature now. So, it has been reset to the correct setting.

This all started because the chiller died last summer, and was replaced
with a temporary chiller just to keep the machine operating.  Some
people apparently designed their process when the wrong chiller
was operating on the machine.

According to the logs, the original chiller was re-installed, and set to
the correct temperature (18 deg C, Cesar Baxter, July 22).
Sometime later (no record), the ciller was changed to 12 C.  This
has caused numerous problems for numerous people.  We couldn't get a
clean bottom on trenches or open areas even with the baseline process
(something that is pretty fundamental!).

The lowered temperature was also likely responsible for the visible
buildup of garbage in the system, which causes problems for some time
even after the chiller is returned to the proper temperature. Chiller
temperature back to normal-> no more garbage.

So it is not an issue of "taking a vote".  Sidewall angles can
be corrected by changing passivation.  Mask erosion can be fixed with
designed mask bias.   Incorrect chiller temperature is not soemthing
you can live with, unless you scrub the chamber daily.

On Thu, 20 Mar 2003, Donald Disney wrote:

> My etch results have also been degraded, apparently by the change in chiller
> temperature.  I would like to see how many people were adversely impacted by
> this change vs. the number that benefited.  I suspect more were adversely
> affected.  If so, I request that the SNF staff please consider reseting the
> temperature.  Please send your comments.
> Don Disney
> -----Original Message-----
> From: Ben Jian [mailto:opticalmachine at]
> Sent: Thursday, March 13, 2003 3:29 PM
> To: stsetch at
> Subject: STS etch
> Dear STS Etch users,
> The chiller temperature on the STS Etch was recently changed from 13 degree
> C to 20 C in response to users complaining about grass formation at 13
> degree C, and will stay at 20 C for the foreseeable future. Unfortunately my
> process is ruined by this temperate change. So with Nancy's approval, next
> Tuesday and Wednesday the chiller will be turned back to 13 C so that I can
> get all my wafers etched. Sorry for any inconvenience this may cause.
> Best regards.
> Ben
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