In this thesis, we first look at the Optical Proximity Correction (OPC) problem and define the goals, constraints, and techniques available. Then, a practical and general OPC framework is built up using concepts from linear systems, control theory, and computational geometry. A simulation-based, or model-based, OPC algorithm is developed which simulates the optics and processing steps of lithography for millions of locations. The key contributions to the OPC field made in this thesis work include: (1) formulation of OPC as a feedback control problem using an iterative solution, (2) an algorithm for edge movement during OPC with cost function criteria, (3) use of fast aerial image simulation for OPC, which truly enables full chip model-based OPC, and (4) the variable threshold resist (VTR) model for simplified prediction of CD based off aerial image.
A major contribution of this thesis is the development of a fast aerial image simulator which is tailored to the problem of OPC. In OPC applications, it is best to compute intensity at sparse points. Therefore, our fast aerial image simulator is tailored to computing intensity at sparse points, rather than on a regular dense grid. The starting point for the fast simulation is an established decomposition of the Hopkins partially coherent imaging equations, originally proposed by Gamo (14). Within this thesis, the decomposition is called the Sum of Coherent Systems (SOCS) structure. The numerical implementation of this decomposition using Singular Value Decomposition (SVD) is described in detail.
Another contribution of this thesis is the development of a variable threshold resist model (VTR). The model uses the aerial image peak intensity and image slope along a cutline to deduce the development point of the resist, and has two primary benefits: (1) it is fast, (2) it can be fit to empirical data.
We combine the fast aerial image simulator and the VTR model in an iterative feedback loop to formulate OPC as a feedback control problem. (Abstract shortened by UMI.)

/pdf/fast-optical-and-process-proximity-correction-algorithms-for-telex7u167.pdf

Fast optical and process proximity correction algorithms for integrated circuit manufacturing

This tutorial paper surveys the potential implications of subwavelength optical lithography for new tools and flows in the interface between layout design and manufacturability. We review control of optical process effects by optical proximity correction (OPC) and phase-shifting masks (PSM), then focus on the implications of OPC and PSM for layout synthesis and verification methodologies. Our discussion addresses the necessary changes in the design-to-manufacturing flow, including infrastructure development in the mask and process communities, evolution of design methodology, and opportunities for research and development in the physical layout and verification areas of EDA.

/pdf/subwavelength-lithography-and-its-potential-impact-on-design-231y1luz46.pdf

Subwavelength lithography and its potential impact on design and EDA

We review the implications of subwavelength optical lithography for new tools and ows in the interface between layout design and manufacturability. After discussing the necessity of corrections for optical process e ects (i.e., use of optical proximity correction (OPC) and phase-shifting masks (PSM)), we focus on the implications of OPC and PSM for layout and veri cation methodologies. Our discussion addresses the necessary changes in the design-tomanufacturing ow, including infrastructure development in the mask and process communities as well as opportunities for research and development in physical layout and veri cation.

/pdf/subwavelength-optical-lithography-challenges-and-impact-on-246eqmt6jm.pdf

Subwavelength optical lithography: challenges and impact on physical design

http://cden.ucsd.edu/internal/Publications/Archive/SFR/Lithography/Kostas_Adam_PhD_Dissertation.pdf

Domain Decomposition Methods for the Electromagnetic Simulation of Scattering from Three-Dimensional Structures with Applications in Lithography

A pixel-based regularization approach to inverse lithography

We propose a new approach to systematic phase shift mask design. In doing so, we constrain the complexity of the mask at a pre-specified level by limiting the number of "features" on the mask. We then optimize the location, size and phase of the features so as to achieve a desired intensity pattern on the wafer. The main advantage of this object-based approach over our previous pixel-based solution is that it results in substantially larger assisting phase shift features, and is therefore easier to fabricate. Our approach can also be used to design masks with proper bias and/or extension of the depth of focus. We show examples of contact hole, bright line and chromeless line-space mask designs. Finally, we show experimental results using the new approach.

/pdf/computer-aided-phase-shift-mask-design-with-reduced-23qolirup3.pdf

Yong Liu

Papers

Computer-aided phase shift mask design with reduced complexity