Discrete Scatterbars for Lithographic Process Margin
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Solution Overview
Problem
Lithographic imaging processes face challenges in achieving consistent critical dimensions due to proximity effects caused by variations in pitch, leading to image distortions and the formation of undesirable resist residue, which negatively impacts yield.
Innovation Solution
The implementation of novel geometries for subresolution assist features, such as discretized scatterbars, which alter the environmental conditions to reduce line width variations and prevent resist residue formation by capitalizing on line-end pull back and forbidden pitches, while taking advantage of resolution disparities in dipole illumination sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If assist features are added to the mask to compensate for pattern distortions, then line-width uniformity and process margin are improved, but resist residue formation increases which negatively impacts yield
Solution Approach 1:
The assist feature is divided into multiple discrete segments rather than being a continuous structure. This segmentation allows the assist feature to provide the necessary diffraction effects for improving line-width uniformity while reducing the total area that can generate resist residue, thereby resolving the contradiction between manufacturing precision and harmful factor generation
Solution Approach 2:
The assist feature segments are strategically positioned at specific locations around the main pattern features where they are most needed to correct proximity effects. By concentrating the assist feature functionality only where required rather than using continuous structures, the patent improves line-width uniformity locally while minimizing overall resist residue formation
2Manufacturing precision
If continuous scatterbars are used as assist features, then proximity effects are reduced, but resist residue forms due to partial exposure from diffracted light
Solution Approach 1:
The continuous scatterbar is segmented into discrete sections with gaps between them. This segmentation maintains the beneficial diffraction effects for improving critical dimension consistency while reducing the continuous exposed area that generates resist residue through partial exposure from diffracted light
Solution Approach 2:
Portions of the continuous scatterbar structure are extracted or removed to create discrete segments. This extraction eliminates the problematic continuous regions that generate excessive resist residue while preserving the essential assist feature functionality in the remaining segments
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in more consistent critical dimensions and improved process margin by avoiding resist residue, enhancing the fidelity of printed features and increasing the yield of the lithographic imaging process.
Implementation Method 1
light diffracted from the edges of the novel subresolution assist features placed near semi-isolated features provides a beneficial interaction with light associated with the semi-isolated feature
Data Source
AI summary
The subject invention provides a system and method for improving the process margin of a lithographic imaging system. The process margin improvement is achieved through the novel placement of discrete assist features and/or the use of forbidden pitches and specific pitch orientations. Novel geometries are utilized, which take advantage of line-end pull back and/or a lack of resolution of pitches perpendicular to an axis of a dipole illumination source. The strategic placement of a series of discrete scatterbar segments on a mask near positions of critical features, such as, for example, contacts, mitigates resist residue that can result from the use of a contiguous scatterbar.