International Business Machines Corporation

Jaione Tirapu-Azpiroz

Alan Edward Rosenbluth

Kafai Lai

Timothy A Brunner

Michael Straight Hibbs

Kehan Tian

David O S Melville

Ramya Viswanathan

Printing risks for sub-lithographic assist features (SRAFs) can be predicted and minimized by employing an SRAF printing model, which is calibrated at a different image plane than an image plane at which a main feature model for predicting shapes of printed images of main features is calibrated. The optical model parameters of the main feature model and the SRAF printing model are calibrated separately such that the main feature model predicts the bottom CD and the SRAF printing model predicts the printing of SRAF features in a photoresist. Optionally, different degrees of printing risk can be assigned for different SRAF configurations.

Method for calibrating an SRAF printing model

A computer-implemented method is provided for generating an electromagnetic field (EMF) correction boundary layer (BL) model corresponding to a mask, which can include using a computer to perform a method, in which asymmetry factor data is determined from aerial image measurements of a plurality of different gratings representative of features provided on a mask, wherein the aerial image measurements having been made at a plurality of different focus settings. The method may also include determining boundary layer (BL) model parameters of an EMF correction BL model corresponding to the mask by fitting to the asymmetry factor measurements. Alternatively, the asymmetry factor data can be determined from measurements of line widths of photoresist patterns, wherein the photoresist patterns correspond to images cast by a plurality of gratings at a plurality of different defocus distances, and the gratings can be representative of features of a mask.

EMF correction model calibration using asymmetry factor data obtained from aerial images or a patterned layer

A desired set of diffracted waves using mask features whose transmissions are chosen from a set of supported values are generated. A representation of the mask as a set of polygonal elements is created. Constraints which require that the ratio of the spatial frequencies in the representation take on the amplitude ratios of the desired set of diffracted waves are defined. An optimization algorithm is used to adjust the transmission discontinuities at the edges of the polygons to substantial equality with the discontinuity values allowed by the set of supported transmissions while maintaining the constraints.

Method for forming arbitrary lithographic wavefronts using standard mask technology

A method, system, computer program product and table lookup system for calculating image intensity for a mask used in integrated circuit processing are disclosed. A method may comprise: decomposing a Manhattan polygon of the mask into decomposed areas based on parallel edges of the Manhattan polygon along only one dimension; determining a convolution of each decomposed area based on a table lookup; determining a sum of coherent systems contribution of the Manhattan polygon based on the convolutions of the decomposed areas; and outputting the determined sum of coherent system contribution for analyzing the mask.

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Poughkeepsie, NY, United States of America

Jaione Tirapu-Azpiroz