Attenuated Phase Shift Mask for Sidewall Spacer Loop Breaking
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Solution Overview
Problem
Current lithography techniques beyond the 40 nm node face challenges such as line-edge roughness, shot noise, acid diffusion blur, and high costs associated with alternative radiation methods, necessitating multiple patterning methods like double, quadruple, or octuple patterning, which complicate pattern placement and overlay, and require additional exposures to remove sidewall spacer loops.
Innovation Solution
An attenuated phase shift mask with etched and unetched regions that control light phase shift and transmission, allowing for the formation of sloped edges and enabling the removal of sidewall spacers in a single exposure, thereby simplifying the patterning process and reducing the need for additional exposures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sidewall spacers are used to form double patterned features, then pattern density is improved, but loops are formed that require additional exposure to remove
Solution Approach 1:
The patent applies preliminary action by pre-forming break features in the phase shift mask before the sidewall spacer deposition. These break features are positioned to align with where loops would form, allowing the loops to be automatically broken during the spacer formation process without requiring additional exposure steps. This resolves the contradiction by preparing the mask in advance to prevent the problematic loop formation.
Solution Approach 2:
The patent introduces break features as intermediary elements in the phase shift mask that mediate between the desired loop formation and the need to avoid loops. These break features are transparent regions that allow light transmission, creating intensity variations that prevent complete loop closure while maintaining the beneficial sidewall spacer patterning. This intermediary structure resolves the contradiction by providing a mechanical solution within the mask design itself.
2Manufacturing precision
If multiple direct exposure methods are used for multi-patterning, then pattern resolution is improved, but pattern placement and overlay challenges increase
Solution Approach 1:
The patent merges multiple patterning functions into a single exposure step by incorporating break features directly into the phase shift mask design. Instead of requiring separate exposure steps for creating patterns and breaking loops, the mask integrates both functions, allowing simultaneous achievement of high-resolution patterning and loop breaking in one lithography exposure. This resolves the contradiction by combining operations that would otherwise require multiple precision-critical steps.
3Manufacturing precision
If conventional masks are used for sidewall spacer patterning, then additional exposure is required to remove loops, but throughput is reduced and cost increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring the phase shift mask with break features that will automatically break loops during the normal sidewall spacer formation process. This eliminates the need for a separate exposure step to remove loops, thereby maintaining high manufacturing precision for edge definition while improving throughput by reducing the total number of process steps required.
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
The attenuated phase shift mask enables the creation of well-defined straight edges and allows for the removal of sidewall spacers without extra exposures, improving throughput and reducing costs by integrating loop breaking and spacer definition in a single patterning step, while being compatible with multiple patterning techniques.
Implementation Method 1
a layer (104) attached to the substrate for reducing transmission and imparting a phase shift to light transmitted through the layer
Implementation Method 2
attenuated phase shift mask having elements including a substrate and a layer attached to the substrate for reducing transmission
Data Source
AI summary
An attenuated phase shift mask (AttPSM) is fabricated with a set of fully transmitting regions, some parts adjacent phase-shifting regions with a first reduced transmission and first phase shift near 180 degrees, and remaining parts adjacent phase-shifting regions with a second transmission higher than the first transmission and second phase shift lower than the first phase shift.