Source Mask Optimization for Lithography Design Rules
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Solution Overview
Problem
Integrated circuit fabrication faces challenges in achieving desired tradeoffs between fabrication costs and yield, particularly at technology nodes beyond 28 nanometers, due to difficulties in forming short lines, terminated lines, and crossovers between adjacent parallel route tracks using 193 nanometer illumination sources.
Innovation Solution
A process involving the generation of design rules and optimization of illumination source models through source mask optimization (SMO) operations, using template structures with varying design rule values, either in a non-iterative or conditional iterative manner, to optimize photolithography processes for forming short lines, terminated lines, and crossovers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If 193 nanometer illumination sources are used for lithography at 28 nanometer node and beyond, then fabrication cost is reduced, but manufacturing precision deteriorates due to inability to form short lines, terminated lines and crossovers with desired lateral dimensions
Solution Approach 1:
The patent applies parameter changes by systematically varying illumination source parameters (angular ranges, radial ranges, dipole orientations) and design rule parameters (line widths, spacing) to find optimal combinations that enable precise patterning at 28nm node using 193nm illumination. Multiple illumination source models with different parameter sets are generated through SMO operations to achieve desired manufacturing precision while maintaining cost-effectiveness of 193nm lithography.
2Manufacturing precision
If multiple pattern steps are used to form desired first metal interconnect layouts at 28 nanometer node, then manufacturing precision is improved, but productivity deteriorates due to increased process complexity and fabrication time
Solution Approach 1:
The patent applies preliminary action by performing source mask optimization operations and generating optimized illumination source models before actual production lithography. The design rule generation and SMO operations are conducted in advance to create pre-optimized process parameters, allowing single-step lithography to achieve what would otherwise require multiple pattern steps, thereby improving productivity while maintaining precision.
3Manufacturing precision
If design rules and illumination source models are optimized for various line types, then manufacturing precision is improved, but device complexity increases due to multiple SMO operations and iterative processes
Solution Approach 1:
The patent applies segmentation by dividing the optimization process into distinct segments: generating template structures for different line types (short lines, terminated lines, crossovers), performing SMO operations on each template type separately, and generating specific illumination source models for each segment. This segmented approach manages complexity by breaking down the overall optimization into manageable, specialized sub-processes.
Solution Approach 2:
The patent applies dynamics through iterative SMO operations where illumination source models are dynamically adjusted and refined based on performance feedback. The conditional iterative process allows the optimization to adapt and evolve, with design rules and source parameters being modified across multiple iterations to progressively improve manufacturing precision while managing process complexity.
Data Source
AI summary
A process of generating design rules, OPC rules and optimizing illumination source models for an integrated circuit layout, to form short lines, terminated lines and crossovers between adjacent parallel route tracks, may include the steps of generating a set of template structures which use a set of characteristic design rules, and performing a plurality of source mask optimization (SMO) operations on the set of template structures with different values for the design rules in each SMO operation. In a first embodiment, the SMO operations are run using a predetermined set of values for each of the design rules, spanning a desired range of design rule values. In a second embodiment, the SMO operations are performed in a conditional iterative process in which values of the design rules are adjusted after each iteration based on results of the iteration.