Alignment marks etched in LTO ?

[Ed Myers]

All,

Be careful.  We have seen alignment marks which are marginal and work 
for a number of layers but not for your whole process.  If Jim pulled 
his batch data and saw a strong signal, I would feel more 
comfortable.  The system has a large capture range, which is why some 
are lead to believe the marks are fine when in reality they are 
extremely marginal.

ASML engineers have a simulation program which they can use to 
determine the correct alignment mark depth for the various films.  I 
recommend we contact ASML to run the simulation and also verify the 
quality of the alignment mark before I would commit my wafers.

How many times have you heard "it aligned at the last layer."  Many 
times this came from marginal alignment marks.

Ed


At 03:40 PM 5/13/2009, jim kruger wrote:

>I have etched (wet) into 1000A thermal Oxide on Si.  Seems to work 
>fine.  I have not tried to overlay more than 2 levels with this.
>
>jim
>
>--- On Wed, 5/13/09, Gaurav Thareja <gthareja at stanford.edu> wrote:
>
> > From: Gaurav Thareja <gthareja at stanford.edu>
> > Subject: Alignment marks etched in LTO ?
> > To: asml at snf.stanford.edu
> > Date: Wednesday, May 13, 2009, 3:22 PM
> > Dear ASML users.
> >
> > Does anybody have any experience in etching and aligning
> > ASML alignment marks in LTO or Thermal Oxide (instead of
> > etching in the substrate) ?
> >
> > please let me know
> >
> > warm regards
> > ~gaurav
> >
> > --
> > Gaurav Thareja
> > Ph.D candidate, Nishi group
> > Electrical Engineering
> > Stanford University
> > 420 Via Palou Mall, CISX 128
> > Stanford, CA 94305
> > Tel: 650-704-1029
> > Email: gthareja at stanford.edu
> >
>
>
>