Methods for modeling of a design in reticle enhancement technology
Methods for reticle enhancement technology include inputting a target wafer pattern, the target wafer pattern spanning an entire design area, and iterating a proposed mask for the entire design area until the proposed mask meets criteria towards producing the target wafer pattern. Each iteration includes calculating a predicted wafer pattern from the proposed mask. The calculating comprises calculating a cost and derivative data, the cost and the derivative data being based on comparing the predicted wafer pattern to the target wafer pattern. The cost further comprises specifications for mask manufacturability.
1. A method for reticle enhancement technology (RET) comprising:
inputting a target wafer pattern, the target wafer pattern spanning an entire design area;
iterating a proposed mask for the entire design area until the proposed mask meets criteria towards producing the target wafer pattern, wherein each iteration comprises:
calculating a predicted wafer pattern from the proposed mask;
wherein the calculating comprises calculating a cost function and a functional derivative of the cost function, the cost function and the functional derivative of the cost function being based on comparing the predicted wafer pattern to the target wafer pattern; and
wherein the cost function further comprises specifications for mask manufacturability.
2. The method of claim 1 , wherein the specifications for mask manufacturability include at least one of minimum size, minimum spacings, maximum curvature, or minimum dose margin.
3. The method of claim 1 , wherein the proposed mask is a continuous tone mask (CTM), and wherein the CTM is represented by a continuous range of values.
4. The method of claim 3 , wherein the continuous range of values are converted to contiguous regions of allowed transmission values, wherein the contiguous regions correspond to shapes on a manufacturable mask.
5. The method of claim 1 , wherein the proposed mask is converted to a quantized tone mask (QTM) wherein the conversion is obtained through regularization.
6. The method of claim 1 , further comprising dividing the entire design area into a plurality of tiles, each tile having a halo region surrounding the tile, wherein the calculating is performed for each tile and its halo region.
7. The method of claim 6 , wherein each iteration further comprises updating the proposed mask for an individual tile in the plurality of tiles and using the updated proposed mask for the individual tile in the plurality of tiles to update halo regions of tiles that neighbor the individual tile, wherein all tiles in the plurality of tiles are calculated before the next iteration.
8. The method of claim 1 , wherein the calculating is performed on a computing platform having an aggregate total memory of all computing nodes of the computing platform, wherein the aggregate total memory holds the target wafer pattern and the proposed mask of the entire design area throughout all iterations.
9. The method of claim 1 , wherein the calculating further comprises mask process correction (MPC).
10. The method of claim 9 , wherein the MPC comprises one or more of correcting for linearity, enhancing critical dimension uniformity (CDU) and enhancing line-edge roughness (LER) as measures of resilience to manufacturing variation.