X-Ray lithography is widely believed to occupy an important future lithographic niche in the vicinity of 0.5 micron and below."] It will be technically easier to achieve resolution and depth of focus with X-Ray than with optical steppers in this lithographic regime. It will be much less expensive to print large volume runners like Dynamic RAMs, microprocessors, or CODECs with X-Ray than with electron beam direct write. However, it is also recognized that distortion in the X-Ray mask membrane may be a major obstacle to the exploitation of this niche, because of the extraordinary registration requirements of submicron design rules.