Photomask Pattern Orientation for Multi-Patterning Lithography
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Solution Overview
Problem
In photolithography, the two-print/two-etch process faces difficulties in patterning due to 'ghost features' that interfere with critical dimension control and require sub-resolution assist features, which complicate pattern formation as densities of integrated circuit devices increase.
Innovation Solution
A method for preparing photomask patterns involves forming a first photomask pattern with longitudinal edges and a second photomask pattern where at least 90% of the longitudinal edges are oriented in the same direction, allowing for improved orientation and alignment during the multi-patterning process, reducing the complexity of pattern formation and interference from assist features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the two-print/two-etch process is used to increase device density, then productivity is improved, but device complexity increases due to ghost features interfering with pattern formation
Solution Approach 1:
The patent extracts and eliminates the problematic ghost features from the second photomask pattern. By identifying that ghost features are the source of interference and complexity, the invention removes these unnecessary pattern elements while retaining the essential functional features needed for device patterning, thereby simplifying the overall pattern formation process
Solution Approach 2:
The patent segments the photomask patterning process into two distinct prints, where the first print establishes the base pattern and the second print adds only the necessary additional features without reproducing ghost features. This segmentation allows each print to have a specific, simplified function rather than attempting to create the complete pattern in a single complex step
2Manufacturing precision
If sub-resolution assist features are added to compensate for ghost features, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by optimizing the first photomask pattern to minimize the formation of ghost features in the first place. Through careful design of the initial pattern and use of proximity correction techniques, the process prevents the creation of problematic ghost features that would subsequently require assist features to compensate, thereby achieving precision without added complexity
3Manufacturing precision
If the drawn pattern is split into multiple photomasks, then manufacturing precision is improved, but ease of manufacture decreases
Solution Approach 1:
The patent merges the advantages of multiple photomasks with the simplicity of a streamlined process by using two prints where the second print is specifically designed to complement the first rather than independently define features. This merging approach combines the precision benefits of multi-mask patterning with simplified alignment and processing requirements, making the overall process easier to manufacture while maintaining high accuracy
Data Source
AI summary
The present disclosure is directed a method for preparing a system of photomask patterns for implementing a drawn pattern on a substrate with a multi-patterning lithography process. The method comprises receiving data describing a drawn pattern. A first photomask pattern is formed for implementing a region of the drawn pattern on the substrate. A second photomask pattern is formed comprising one or more pattern features having longitudinal edges for implementing the region of the drawn pattern on the substrate, wherein at least 90% of all the longitudinal edges of the second photomask pattern that are positioned within the region are oriented in substantially the same direction. Both a system for forming the photomask patterns and a process for patterning a device using the photomask patterns are also disclosed.