PQuest after clean, 4-18-08--corrected date
jimkruger at yahoo.com
Fri Apr 18 14:19:47 PDT 2008
Sorry, I mis-typed the date.
--- jim kruger <jimkruger at yahoo.com> wrote:
> Date: Fri, 18 Apr 2008 12:41:00 -0700 (PDT)
> From: jim kruger <jimkruger at yahoo.com>
> Subject: PQ after clean 5-18-08
> To: pquest <pquest at snf.stanford.edu>
> PQuest check 4-18-08
> After the chamber clean and Turbo pump scare, I
> checked the Leak-up rate and the He blow-by on
> The leak-up rate was 2.2 mTorr/minute, but this
> after a GaAs recipe chamber conditioning and only
> day after the Wet Clean. The Best Ever leak-up
> rate, expected after ~ days since wet lcean and
> an O2 chamber clean is about 1.0 mTorr / min. I
> ~2 to be OK, 5 or 10 is a problem.
> The back-side wafer He blow-by is very good right
> The issue is that the there is a high flow
> between the pressure monitor and the chuck so the
> pressure behind the wafer is lower for high blow-by
> flows and thermal impedance is raised.
> For Chuck Temperature = 11 C (chiller at 0, set
> = 13 C), the no wafer flow was 11.1 sccm . With
> new carrier wafer in place it was 5.5 sccm. This
> gives a delta of 5.6 sccm, very good.
> I judge a He blow-by delta of 3 or 4 to be good, 2
> marginal, 1 or less poor.
> The flows are all temperature dependent (lower for
> higher Chuck temperature) so you need to
> your recipe.
> Be a better friend, newshound, and
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