From robinhmb at yahoo.com  Thu Nov 15 19:01:53 2007
From: robinhmb at yahoo.com (Robin King)
Date: Thu, 15 Nov 2007 19:01:53 -0800 (PST)
Subject: Furnace is available this eve.
Message-ID: <379844.61697.qm@web58712.mail.re1.yahoo.com>

 
 


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From kimsangb at stanford.edu  Fri Nov 30 17:40:25 2007
From: kimsangb at stanford.edu (SangBum Kim)
Date: Fri, 30 Nov 2007 17:40:25 -0800
Subject: dry oxidation within-a-wafer thickness uniformity
Message-ID: <20071130174025.6qksy5a268sgcwg8@webmail.stanford.edu>

Dear tylan users,

  Is dry oxidation less uniform than wet oxidation?

  I did dry oxidation at 1000C for 55mins targeting 500A of oxide on  
prime p type 100 wafer just cleaned out of stock room. The thickness  
measured by nanospec with fixed refractive index shows that there are  
thickness variation within-a-wafer as large as 30% (500A vs 750A).

  On the other hand, the characterization result by Nancy on coral  
shows that we should be able to achieve less than 5% variation with  
900C wet oxidation. Has anyone measured within-a-wafer variation of  
your wafers?

  How can I achieve better within-a-wafer variation? A location in the  
tube? Wet vs dry? Temperature? Annealing?

Thanks,
SangBum


From sanli.ergun at gmail.com  Fri Nov 30 18:16:29 2007
From: sanli.ergun at gmail.com (A. Sanli Ergun)
Date: Fri, 30 Nov 2007 18:16:29 -0800
Subject: dry oxidation within-a-wafer thickness uniformity
In-Reply-To: <20071130174025.6qksy5a268sgcwg8@webmail.stanford.edu>
References: <20071130174025.6qksy5a268sgcwg8@webmail.stanford.edu>
Message-ID: <8e6439130711301816y36aca71du9aa9e3f05fadece3@mail.gmail.com>

The quick answer is no, read on for details.

I did a lot of on-wafer and wafer-to-wafer thickness uniformity tests both
with dry and wet oxidation. Both should have very good uniformity, but DRY
oxidation should definitely be more uniform. 30% variation is not possible
with dry oxidation. Either there was something wrong with the oxidation run,
or there was something wrong with nanospec. Do you visually see a color
fringe on your wafers? If yes, then there is something wrong with the
oxidation. If no, then probably nanospec is not measuring right. What is the
history of your wafers? I used to get ~1-2 % thickness uniformity with dry
oxidation, easily, 4 years ago.

Sanli

On Nov 30, 2007 5:40 PM, SangBum Kim <kimsangb at stanford.edu> wrote:

> Dear tylan users,
>
>  Is dry oxidation less uniform than wet oxidation?
>
>  I did dry oxidation at 1000C for 55mins targeting 500A of oxide on
> prime p type 100 wafer just cleaned out of stock room. The thickness
> measured by nanospec with fixed refractive index shows that there are
> thickness variation within-a-wafer as large as 30% (500A vs 750A).
>
>  On the other hand, the characterization result by Nancy on coral
> shows that we should be able to achieve less than 5% variation with
> 900C wet oxidation. Has anyone measured within-a-wafer variation of
> your wafers?
>
>  How can I achieve better within-a-wafer variation? A location in the
> tube? Wet vs dry? Temperature? Annealing?
>
> Thanks,
> SangBum
>



-- 
A. Sanli Ergun
Research Scientist
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