density rule active dummy layer
maximum density is exactly the opposite of the minimum density error. layers such as diffusion, poly and metals may exceed the allowable concentration per given area at chip level. when fabricating chips, the silicon is polished. it is preferable to have uniform concentration of all layers all through out the chip, so it would be polished uniformly. maximum density causes the chip to be polished unevenly, causing less dense areas to be polished out.