If your looking for a cheaper solution than EV you can go with any
microscope that has a back/bottom side illuminator and an IR camera (as long
as you don't have metal between your front and backside alignment marks :-)

                                                        eric
>
> Message: 7
> From: Roger Brennan 
> To: "[email protected]" 
> Date: Wed, 31 Jul 2002 06:04:54 -0700
> Subject: [mems-talk] Front-to-Back Inspection Microscope
> Reply-To: [email protected]
>
> Hi,
>
> I am looking for a method of checking frontside-to-backside alignment at
> develop inspect.  The photoresist pattern (on both sides of the silicon
> wafer) is a little over a micron thick.  Years ago, AO (American Optical)
> offered such a microscope. All suggestions will be appreciated.
>
> Thanks in advance,
> Roger Brennan