AutoCAD 2010 :: Drawing A Pattern Of Circles?

I am trying to make a hexagonal lattice of circles (1 micron dia, period - 3 microns) and exted it over a square cm in area atleast. The final objective is to make this as a mask pattern for the Laser fabrication/writer. So I create the pattern over a small area and use array command to extend it over a finite area (~500 microns or so). I then combine these points to a single block and then use the mirror command to extend it even further. But as soon as I reach an area of 2.5 mm square, the program seems to slow down and doesnt respond. I assume this is the limitation of my computing power to handle so many objects at once. (I have 4 GB RAM and 97 % is utilized at this time). Is there a way to circumvent this computing limitation, making use of some facility/command within AutoCAD?