HI Wei,

A couple of things that you need to watch for here.

First, if you are making a new quartz mask and are trying to align to a pattern
previously applied to a wafer (either etch or metal), then if your original mask
was the source of your run-in/out problems, this alone will not solve them.  You
will have to remake each mask level in quartz to see an improvement.

Second, the pressure that I am referring to is the internal pressure applied
when first bringing the wafer into contact with the mask.  The MJB3 has a series
of pressure gauges, usually on the right side, that indicate settings.  The
chuck floats on a bladder filled with N2, the purpose of which is to establish
the parallelity of the wafer to the mask.  The pressure internal to  this
bladder is what I am referring to, and unfortunately, it's been so long since
I've used one of these aligners, I forgot what the correct name for this is.
Suffice it to say, make sure that all of the pressure gauges are set within
manufacturer's settings.

Third, and related to the pressure, is the actual height of the chuck.
Depending on the age of your aligner, it will have either a technician-only
accessible internal adjustment, or a 10-turn knob on the front of the tool that
allows the height to be adjusted.  This adjustment is quite sensitive and is
best made by a tech with a dial gauge fixture (provided by Suss) that allows the
travel to be measured.  The height could affect the pressure applied between the
mask and the wafer even before your vacuum contact pressure is applied.  To
determine if this could be your problem, you would expect that your second
pattern would appear smaller relative to the first pattern.

I hope this makes sense.

Brad
_________________________________

Brad Cantos
brad.cantos@holage.com
http://holage.com




On 18 May 2011, at 2:21 PM, Wei Tang wrote:

> Hi, Brad
>
> Thanks for the suggestion. I have sent a request to make quartz mask
> and hope to see an improvement of alignment accuracy. Regarding the
> pressure, I use the vacuum contact mode, which apply a -0.6atm
> pressure to the chunk against the mask. The wafer size is 1cmX1cm (I
> think the effect of pressure also depend on wafer size, for larger
> wafers, the press force will be more spread out, can cause less
> bowing). I am wondering is the pressure too big under my condition
> according to your experience?
>
> Thanks,
>
> Wei