This invited paper reviews progress over the past ten years of contributed effort to the understanding and the mitigation
of multilayer defects on the EUV mask blank. These defects are an EUV-specific type of mask defects. Whereas the only
true solution is to totally avoid the presence of such ML-defects during blank manufacturing, some level of capability of
printability mitigation has been demonstrated, both by absorber compensation repair and by pattern shift. In both cases, it
is essential that one can build on a full-proof blank inspection capability, that detects all printable blank defects, at a very
low false detection rate, such as by using actinic blank inspection. This capability, together with providing accurate
defect location information, establishes an essential prerequisite for their mitigation or avoidance. On the latter, the
proposal is made to extend pattern shift to intentional pattern deformation.