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A Simulation-Based Method For Resolution of Phase-Shifter Placement Conflicts in Full Phase Alternating Aperture PSM Disclosure Number: IPCOM000020000D
Publication Date: 2003-Oct-16
Document File: 6 page(s) / 90K

Publishing Venue

The Prior Art Database


The assignment of phase to the phase-shifters in an alternating aperture phase shifting (AAPS) mask can be a difficult problem due to phase, or coloring, conflicts. A method for resolving those conflicts using simulation of critical areas adjacent to the phase shifters causing the conflicts. These simulations can then be used to associate a cost with different possible resolutions and thus facilitate a final choice of resolutions.

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1. Descriptive Title

A Simulation-Based Method for Resolution of Phase-Shifter Placement Conflicts in Full Phase Alternating Aperture PSM

2. Problem

Full Phase technology is based on combination of a full-field alternating aperture PSM (AAPSM) and a binary trim mask. Full-field AAPSM means that all of the layout patterns need to be phase shifted. As various chip designs have arbitrary layout properties and complexity, it presents a significant implementation challenge for AAPSM since it is based on alternation of 0 and 180-degree phase shifters. As a result, multiple regions of a given layout may end up with a phase conflict where certain segments of critical patterns cannot be phase shifted. In order to fix the phase conflicts, it has been previously proposed to add so called 'cut-lines' which allow breaking the phase cycles. It also has been proposed to enable automated optimization mechanisms for phase conflict resolution based on certain simple criteria (such as adjacent geometries and spacing) translated into cost functions. Nevertheless, although it is possible to implement such a methodology from a global standpoint, it is very probable that there will be a number of remaining phase conflicts with a comparable cost which are difficult to differentiate.
3. Solution

In this disclosure we propose a simulation-based approach to resolve phase shifter conflicts. This method modifies the conventional phase-shifter placement flow by plugging-in a simulation engine for advanced conflict resolution. The implementation of this method would consist of the following steps:

1. After completion of the shifter placement costing, the software would flag the layout regions/patterns that are difficult to set apart from a conventional standpoint
2. Then the software would perform a simulation of critical areas (contours or cross-sections) and calculate a specified lithography parameter, which would reflect on the imaging robustness. Among candidate parameters could be image contrast, NILS, MEEF, DOF at a specified exposure latitude, etc.
3. Calculated lithography parameter allows to refine the costing of the critical layout areas, therefore ensuring an optimal phase shifter placement from lithography standpoint

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