Zhang,
    You may not need to merge the layers in your design file at all.
Many mask writers have the capability to logically merge layers just
berfore printing, e.g. XOR, AND etc.. Check with the folks writing your
mask.

-Mike Martin
 U. of Louisville


>>> "Zhang Xuming"  08/26/06 3:40 AM >>>
Dear MEMS experts:

I have had a problem in merging two layout layers for a long time, and
would seek your help.

In the layout design (i'm using L-Edit), it is convenient to define
two
logic layers for a single layer of real structure (for example, the
structural silicon layer of SOI wafer). One layer is for positive
(i.e.,
draw what we want to have), another is for negative (draw where we
want
to remove). These two logic layers make it easy to draw complicated
structures and to make markers.

However, it comes with a problem. Before sending for making photomask,
we need to merge the two logic layers into one layer. L-Edit can do
the
mergence for very simple standard objects (e.g., rectangles). But for
many complicated designs in large area, it is untolerably slow. Some
companies have their own developed tools, but the mergence sometimes
loses some parts of structures.

How do you solve this problem? What is the commercially-available
software tool you use?