Isa, For only two layers, the box in a box alignment marks work very well. The first mark is just a square. The second mark is a window that goes around the first square, and is larger by a gap that is just a few times bigger than your alignment tolerance (so no more than 2 or 3 microns for 0.5 micron tolerance). The overall size of the square should be large enough to comfortable fit in the field of view. Typically, I do a bunch of these marks to go from coarse alignment to fine alignment. The largest squares I use are 200 microns on a side with 25 micron gaps, going down to 5 micron squares with 1 micron gaps. This simplifies finding the alignment marks in the begining. The sizes you choose will depend on your first later process (does it grow or shrink the mask pattern? Is there a minimum feature size?), your magnification, and your illumination (how well can you see the first layer marks?). But as a rule of thumb, square in a box works great. Make the gap 2 to 3 times bigger than the desired alignment tolerance. Don't forget coarse alignment marks, and put in more marks than you need, as they don't take up much space. Good luck! David Nemeth Senior Engineer Sophia Wireless, Inc. 14225-C Sullyfield Circle Chantilly, VA Ph: (703) 961-9573 x206 Fax:(703) 961-9576 -----Original Message----- From: mems-talk-bounces+nemeth=sophiawireless.com@memsnet.org [mailto:mems-talk-bounces+nemeth=sophiawireless.com@memsnet.org]On Behalf Of Isa Kiyat Sent: Friday, March 12, 2004 2:34 AM To: General MEMS discussion Subject: [mems-talk] Alignment marks I am designing a photomask. I will have a two step lithography with maximum 0.5 um tolerance. I need your suggestions about the kind of alignment marks I should use (shape, dimension any experience will help) . Thanks. ================================= Isa Kiyat _______________________________________________ MEMS-talk@memsnet.org mailing list: to unsubscribe or change your list options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk Hosted by the MEMS Exchange, providers of MEMS processing services. Visit us at http://www.memsnet.org/