Lithography Assist Pattern Spacing Optimization
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Solution Overview
Problem
In semiconductor manufacturing, when main pattern features are disposed at random pitches, adding uniform assist pattern features does not maximize margin improvement effects due to varying pitches, leading to potential overlay and mask constraint violations.
Innovation Solution
A method to create mask pattern data by determining the spacing and size of assist pattern features based on the pitch of main pattern features, adjusting their positions and sizes to ensure optimal margin and prevent overlay, using off-axis illumination to improve lithography margins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform assist pattern features are added to all main pattern features, then the process is simple and easy to manufacture, but the margin improvement effects are not maximized for varying pitches
Solution Approach 1:
The patent applies local quality by varying the pitch of assist pattern features according to the specific pitch of each main pattern feature. Instead of using a uniform pitch for all assist features, the system calculates and assigns different pitches to assist features based on their corresponding main pattern's pitch characteristics, thereby optimizing margin improvement for each local region with varying pitch requirements
Solution Approach 2:
The patent changes the pitch parameter of assist pattern features dynamically based on the pitch of main pattern features. The system calculates the pitch of each main pattern feature and uses this information to determine the appropriate pitch for its corresponding assist pattern feature, transforming a static uniform pitch approach into a dynamic parameter-adjusted approach that adapts to different pitch conditions
2Manufacturing precision
If assist pattern features are placed closely to improve margin, then margin improvement is enhanced, but overlay and mask constraint violations occur
Solution Approach 1:
The patent dynamically adjusts the pitch parameter of assist pattern features based on the pitch of main pattern features. By calculating the appropriate pitch for each assist feature according to its corresponding main pattern's pitch, the system optimizes the balance between achieving sufficient lithography margin improvement and preventing overlay violations or mask constraint breaches that would occur with fixed close spacing
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 allows for high-precision formation of main pattern features on a semiconductor wafer with improved yield by optimizing assist pattern feature placement, avoiding overlay and mask constraint violations, and enabling simultaneous exposure of periodic and non-periodic patterns using off-axis illumination.
Implementation Method 1
process margins (an exposure amount margin and/or a focus margin) are improved in comparison with a perpendicular illumination by using a modified illumination such as a dipole illumination or a quadrupole illumination that irradiates obliquely onto a photomask
Data Source
AI summary
A mask pattern data creation method includes: determining whether or not a spacing of adjacent assist pattern feature data is not more than a prescribed spacing, based on: initial position data indicating an initially set position of the assist pattern feature data determined based on an illumination condition; and initial size data indicating an initially set size of the assist pattern feature data satisfying a size condition to not optically form an image on the transfer destination; and moving at least one of the adjacent assist pattern feature data or reducing a size of the at least one to increase the spacing of the assist pattern feature data to exceed a prescribed spacing in the case where it is determined that the spacing of the assist pattern feature data is not more than the prescribed spacing.