Method and apparatus for performing dark field double dipole lithography (DDL)
A method of generating complementary masks for use in a dark field double dipole imaging process. The method includes the steps of identifying a target pattern having a plurality of features, including horizontal and vertical features; generating a horizontal mask based on the target pattern, where the horizontal mask includes low contrast vertical features. The generation of the horizontal mask includes the steps of optimizing the bias of the low contrast vertical features contained in the horizontal mask; and applying assist features to the horizontal mask. The method further includes generating a vertical mask based on the target pattern, where the vertical mask contains low contrast horizontal features. The generation of the vertical mask includes the steps of optimizing the bias of low contrast horizontal features contained in the vertical mask; and applying assist features to the vertical mask.
1. A method of generating complementary masks for use in a dark field double dipole imaging process, said method comprising the steps of:
identifying a target pattern having a plurality of features, said plurality of features comprising horizontal and vertical features;
generating a horizontal dark field mask based on said target pattern, said horizontal dark field mask including low contrast features, said generation of said horizontal dark field mask comprising the steps of:
optimizing the bias of said low contrast features contained in said horizontal dark field mask; and
applying assist features to said horizontal dark field mask;
generating a vertical dark field mask based on said target pattern, said vertical dark field mask containing low contrast features, said generation of said vertical dark field mask comprising the steps of:
optimizing the bias of low contrast features contained in said vertical dark field mask; and
applying assist features to said vertical dark field mask; and
decomposing the target pattern into the horizontal dark field mask and the vertical dark field mask, the decomposing comprising:
performing model-based optimization of both masks so as to optimize imaging performance criteria after double exposure of a feature in the target pattern during the dark field double dipole imaging process using both masks.
2. The method of generating complementary masks for use in a dark field double dipole imaging process according to claim 1 , wherein the model-based optimization comprises one or more of a model-based bias optimization, a model-based placement optimization, and a model-based assist feature placement optimization.
3. The method of generating complementary masks for use in a dark field double dipole imaging process according to claim 1 , wherein said imaging performance criteria comprise one or more of DOF, MEF, ILS, NILS, or contrast.
4. The method of generating complementary masks for use in a dark field double dipole imaging process according to claim 3 , wherein the optimization process for both masks is performed simultaneously.
5. The method of generating complementary masks for use in a dark field double dipole imaging process according to claim 3 , wherein the optimization process for both masks is performed in a serial manner.
6. A method of generating complementary masks for use in a dark field double dipole imaging process, the method comprising the steps of:
identifying a target pattern having a plurality of features, the plurality of features comprising horizontal and vertical features;
decomposing the target pattern into a horizontal dark field mask and a vertical dark field mask, the decomposing comprising performing model-based optimization of both masks so as to optimize imaging performance criteria after double exposure of one or more of the features in the target pattern during the dark field double dipole imaging process using both masks.
7. The method of generating complementary masks for use in a dark field double dipole imaging process according to claim 6 , wherein the imaging performance criteria comprise one or more of ILS and NILS of a portion of a simulated image corresponding to the one or more features.