Notched Trim Mask for Phase Shifting Lithography
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in integrated circuit fabrication is line end widening, which affects feature definition and device performance, and complicates optical proximity correction in phase shifting masks, leading to increased fabrication costs.
Innovation Solution
A notched trim mask design with transitional areas featuring notches between structures for non-critical and critical features, which minimizes line end widening and simplifies optical proximity correction, allowing for improved feature definition and reduced fabrication costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a standard trim mask is used with phase shifting mask, then the manufacturing process is simple, but line end widening occurs which degrades feature definition and device performance
Solution Approach 1:
The trim mask is segmented into distinct functional regions: a first structure for non-critical features, a second structure for critical features, and transitional areas with notches between them. This segmentation allows each region to serve its specific purpose in controlling line end widening while maintaining overall mask functionality.
Solution Approach 2:
Different regions of the trim mask are given different local qualities and functions. The notches in the transitional areas provide localized correction for line end widening, while the first and second structures maintain their respective functions for non-critical and critical feature definition. This local differentiation resolves the contradiction by applying complexity only where needed.
2Manufacturing precision
If optical proximity correction is applied to compensate for line end widening, then feature definition improves, but mask manufacturing complexity and cost increase
Solution Approach 1:
The notches are pre-formed in the trim mask during standard mask fabrication, performing the proximity correction action in advance. This preliminary action eliminates or reduces the need for additional OPC steps during manufacturing, thereby maintaining ease of manufacture while achieving improved line end definition.
Solution Approach 2:
The notched transitional areas act as an intermediary structure between the first and second mask structures. These notches mediate the optical interaction to reduce line end widening effects, providing a simpler alternative to complex OPC algorithms and reducing both manufacturing complexity and cost.
3Ease of manufacture
If the trim mask structure is simplified, then manufacturing cost decreases, but line end widening cannot be corrected
Solution Approach 1:
The mask is segmented into functional zones where the notched transitional areas specifically address line end precision issues, while the first and second structures maintain simplified designs for non-critical and critical features respectively. This segmentation allows simplified manufacturing overall while preserving precision where it matters most.
Solution Approach 2:
The notches modify the geometric parameters of the mask structure in the transitional areas, creating specific optical path differences that correct line end widening. These parameter changes are localized and do not complicate the overall mask fabrication process, achieving precision correction with minimal added complexity.
Data Source
AI summary
A phase shifting mask (PSM) and a trim mask can be used in a dual exposure to form circuits on an integrated circuit. The trim mask can include first structures that define non-critical features of a design (e.g. line ends), second structures that protect areas exposed by phase shifters, wherein such areas including critical features (e.g. transistor gates) of the design, and transitional areas located between the first and second structures. Notably, these transitional areas can include notches. This notched trim mask can advantageously minimize line end widening, thereby improving feature definition and device performance on the resulting integrated circuit. The notched trim mask can also advantageously simplify the optical proximity correction of its associated PSM, thereby minimizing fabrication costs.