PQuest after clean, 4-18-08--corrected date

[jim kruger]

Sorry, I mis-typed the date.

jim
--- 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
> PQuest.
> 
> The leak-up rate was   2.2 mTorr/minute, but this
> was
> after a GaAs recipe chamber conditioning and only
> one
> day after the Wet Clean.  The “Best Ever” leak-up
> rate,  expected after ~ days since wet lcean and
> after
> an O2 chamber clean is about 1.0 mTorr / min.  I
> judge
> ~2 to be OK, 5 or 10 is a problem.
> 
> The back-side wafer He blow-by is very good right
> now.
>  The issue is that the there is a high flow
> impedance
> 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
> point
> = 13 C), the ‘no wafer  ” flow was 11.1 sccm .  With
> a
>  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
> characterize
> your recipe.
> 
> jim
> 
> 
> 
>      
>
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