Patent ID: 7713682

Claim:
A method of forming a pattern of dense features of resist material on a substrate, including exposing the substrate to radiation, the substrate including a first layer of a positive tone resist at least partially overlying the substrate, the method comprising: exposing a second layer of a positive tone developable material overlying at least part of the first layer to a first radiation pattern comprising semi-dense dark features in a bright background, the second layer having an absorbance higher than an absorbance of the first layer; developing the positive tone developable material to provide a pattern of features protruding from the first layer, the features separated by areas of uncovered first layer; exposing the uncovered first layer and the protruding features to a second radiation pattern comprising semi-dense dark features in a bright background, the dark features being positioned in interlaced relation with respect to the protruding features; and developing the positive tone resist to provide the pattern of dense features; wherein the absorbance of the second layer is arranged to prevent, during exposing, an exposure of at least a portion of the positive tone resist underneath the positive tone developable material to an exposure dose exceeding a fraction of an energy-to-clear exposure dose associated with the first layer, and to provide substantially complete photoactivation of the second layer.