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Improved Optical Proximity Correction in Microlithography

IP.com Disclosure Number: IPCOM000124181D
Publication Date: 2005-Apr-11
Document File: 3 page(s) / 55K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses simultaneous calculations of segment interactions, during the mask database optical proximity correction (OPC), to obtain a better reproduction of the design layout on wafers. Benefits include a solution that requires no iterations.

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Improved Optical Proximity Correction in Microlithography

Disclosed is a method that uses simultaneous calculations of segment interactions, during the mask database optical proximity correction (OPC), to obtain a better reproduction of the design layout on wafers. Benefits include a solution that requires no iterations.

Background

Conventional OPC is computed segment by segment in a sequential fashion. As each correction iteration is performed, assumptions are made about the movement of neighboring segments and approximations to their impact on the current segment. The current method does not take into account the contribution of the current segment movement to other segments, and only approximates the impact of the movement of other segments on this segment. As a result, this iterative solution can produce convergence issues between near but non-sufficient configurations. Manufacturing tolerances are alternately met in one segment but not the other, with the failure oscillating between segments from iteration to iteration.

The current solution approximates local change by simulating an infinitely long strip of chrome and computing sequentially the adjustment required for each segment. This approximation is applied to each segment, then repeated until (hopefully) there is convergence. The problem with existing methods is the failure to calculate the contribution of all the segments to all other segments in a simultaneous manner.

General Description

The disclosed method’s calculation during OPC computes how far the edge of the image is from where it needs to be, the impact per unit change of changing the chrome, and then applies the change.  A new method, PROTOBOX, was invented for this simultaneous approach. The desired image edge changes are combined with the computed change (per change) in chrome (per segment) and solved using a standard method called SVD.  This creates a method for solving simultaneously for all segments in a problem area. Additional methods were developed to recognize a problem area that is appropriate for applying the solver. The following are the mathematical details.

During OPC, an evaluation point is assigned to each segment; for each evaluation point one can describe any OPC function (signal intensity, process window, MEEF, etc) as a function of displacements of neighboring segments:

 Fj(CR1, CR2, ……., CRn), F: any OPC function, where j is the j-th evaluation point, n the number of segments, CR the displacement of a segment. By doing

Taylor

expansion on every Fj we can construct an equation set:

 

 

 

 

where 2nd order and higher terms are omi...