nickel silicide process concern in SNF.

Ed Myers edmyers at stanford.edu
Wed Nov 3 10:38:43 PST 2004


All,

I feel it's important we close on this soon.  It's my expectation to do a 
quiet "green light" for the SCT, probably next week.  The first materials 
which will come out of the tool for continued processing will be aluminum, 
tungsten and nickel.  With the "green lighting" of the tool the process 
development for these materials will commence.  The development will be 
done by users under my supervision.  My expectation is wafers with the 
metals could be circulating through the fab by mid November.

Another point is the limit on film thickness.  I don't think we should put 
a limit on the deposition thickness at this time.  No one I've talked with 
wants thin films.  1,500 to 2,000 Angstroms is more typical.  The only way 
limiting the film thickness makes sense is putting an adhesion layer 
between each deposition.  The adhesion layer would be something like Al or 
Ti.  This has raised a cross contamination concern.  First we need to see 
how the hardware will respond to the depositions.  I know a very thin W 
layer on the original designed shielding yielded a tremendous amount of 
particles.  We need to see what happens with the current hardware.  I think 
it will be better, since I have not seen as much heat induced discoloration 
on the new shielding design.

With the recent interest in Nanolithography, I see a need for clean Cr in 
the very near future.

Ed


At 09:38 AM 11/3/2004, Michael Deal wrote:
>At 09:19 AM 11/3/2004, you wrote:
>>Great!  Thanks!  So, are there "official" semiclean B rules now (other 
>>than the wet bench concerns?)  Are they ready enough to post to 
>>SpecMat?  (And are there any plans for plasma etchers?  I think this is 
>>where Jun has concerns...)
>>
>>Mary
>
>Mary,
>    Here's what we decided a month or two ago:
>
>
>>>Here is the current list of materials planned for the SCT:
>>>              Ni, Co, Pt, Al, Hf, Ta, Mo, W, Ti, Cr, Zr
>>>All targets except for Pt, Zr, and Cr, are already here.
>>>
>>>Al, W, and Ti are currently classified as "semi-clean."  The others (Ni, 
>>>Co, Pt, Hf, Ta, Mo, and Cr, and Zr) are currently being studied and used 
>>>by our users and by industrial chip manufacturers as gate materials and 
>>>as silicides.   So far, unlike Au, Cu, alkalai metals, etc., no harmful 
>>>effects have been seen on device performance with these 
>>>elements.  However, we should still be careful with them in case 
>>>something may arise.   In many cases, the users most sensitive to their 
>>>effects (i.e. those building CMOS devices) are the ones who are now 
>>>studying and using them.  Jim and I are working with several of the 
>>>students who are using these materials and we will keep a close eye on this.
>>>
>>>Here's what we propose:
>>>
>>>1. Deposition of all metals in the SCT will be limited to 100nm (may be 
>>>increased to 200nm).   This will limit the problems (peeling, 
>>>contamination, etc.) caused by excess deposition of these materials.
>>>2. Al, Ti, and W will be classified as "semi-clean-A" and will be 
>>>treated as before in terms of what equipment wafers deposited with these 
>>>elements can go into subsequent to their deposition in the SCT. These 
>>>include LTO (tylanbpsg), tylanfga, wbsolvent, wbgeneral, wbmetal, 
>>>wbsilicide as well as many of the litho and etch equipment.
>>>3. The other elements (Ni, Co, Pt, Hf, Ta, Mo, Cr, and Zr) will be 
>>>classified as "semi-clean-B."  Wafers deposited with these elements in 
>>>the SCT can go into all the equipment listed in the semi-clean group, 
>>>EXCEPT for the etching systems.  (Most can only be wet-etched anyway.)
>>>
>>>Before we do this, however, Jim will look into any issues regarding the 
>>>use of wet benches and any possible cross-contamination that might occur 
>>>during cleaning.
>>>
>>>Finally, many of these materials already have some "special processing 
>>>rules" such as how any etching solution must be disposed of.  These 
>>>rules will be continued.





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