processing policies in SNF for SCT metals and Ge (corrected subject line)

Michael Deal mdeal at stanford.edu
Fri Dec 10 07:54:16 PST 2004



Labmembers,
       The SNF Special Materials (Specmat) committee has decided on some 
new policies regarding the processing of two types of materials:  1. metals 
deposited in the new SCT sputter deposition system, and 2. Ge wafers or Si 
wafers with Ge thin film layers.   Below are the policies regarding 
them.  If you have any questions, please email 
specmat at snf.stanford.edu.   Thanks.


Processing of Semiclean B materials

The following materials will be deposited in the new SCT sputter deposition 
system:

              Ni, Co, Pt, Al, Hf, Ta, Mo, W, Ti, Cr, Zr

The SCT system is Au-free.   While there has been some concern with these 
metals in regards to contamination of MOS devices, these materials are 
currently being successfully used in industrial MOS processes in gate 
dielectrics, gate electrodes, and contacts.  Based on input from 
labmembers, industrial collaborators, literature investigations, as well as 
previous experience with some of these materials, the specmat committee has 
decided on the following modified equipment-class policy:

         1. All metals from SCT will be classified as semiclean B.
         2. Al, Ti, and W deposited in the Gryphon will be classified as 
semiclean A.
         3. All metals from Innotec and Metallica are still gold 
–contaminated.

- Semiclean A class wafers will be treated the same as the old semiclean class.

- Semiclean B class wafers (i.e. those deposited in the SCT system) can be 
processed in all semiclean equipment (i.e. tylanbpsg, tylanfga, etc.) as 
well as the litho equipment, with the following IMPORTANT restrictions:

         a. Semiclean B class wafers can only be cleaned or wet-etched at 
wbgeneral in dedicated clean beakers.
         b. Dry-etching of these films will be allowed on a case-by-case 
basis.  (Etching oxide down to these SCT metals will be allowed in oxide 
etchers in the semiclean equipment set, ie. AMTetcher and P5000.)
         c. When annealing semiclean B class wafers in the AG4108 RTA, the 
silicide tray must be used, which from now on will be referred to as the 
"semiclean tray".  (Once the AG4100 comes on line, it will be classified as 
a semiclean tool and will be used for all semiclean materials including SCT 
metals and Ge.  The AG4108 will be dedicated to clean materials only.)
         d. Semiclean B materials (as with semiclean A materials) should 
use the metal-side of tylanfga.


Processing of germanium (Ge)

Although Ge is not a contamination problem in Si, because of limited 
knowledge regarding Ge cleaning, Ge wafers will be classified as a 
semiclean B material.   Therefore:

- Ge wafers can be processed in all semiclean equipment (i.e. tylanbpsg, 
tylanfga, etc.) as well as the litho equipment, with the following 
IMPORTANT restrictions:

         1.  Ge wafers can only be cleaned or wet-etched at wbgeneral in 
dedicated clean beakers.
         2.  When using the AG4108 RTA, the silicide tray must be used, 
which from now on will be referred to as the "semiclean tray". (When the 
AG4100 becomes available, all Ge and other semiclean processing will be 
done in the AG4100.)



The specmat committee will conduct further experiments and monitoring to 
ensure that other labmembers’ projects remain unaffected by the use of 
these materials and to possibly allow some or all of these restrictions to 
be modified or removed in the future.




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