Pitch Multiplication Using Protective Spacer for High Fidelity
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Solution Overview
Problem
Current photolithography techniques have reached their limits for feature size reduction, and existing multiple patterning methods, such as self-aligned double-patterning (SADP) and self-aligned litho-etch-litho-etch (SALELE), suffer from sidewall spacer taper and profile variations, leading to feature size variations and unreliable pattern transfer in semiconductor integrated circuits.
Innovation Solution
A self-aligned multi-patterning method involving the conformal deposition of spacer materials, where a protective spacer is used to maintain a vertical profile during etching, reducing sidewall taper and ensuring uniformity, and the use of non-mandrel materials to form lines with a vertical profile for reliable pattern transfer into the underlying layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional multiple patterning methods (SADP, SALELE) are used for feature size reduction, then pitch multiplication is achieved, but sidewall spacer taper and profile variations occur leading to feature size variations
Solution Approach 1:
A protective spacer layer is deposited conformally onto the sidewall spacers before the etch process. This preliminary protective layer prevents etching of the top portions of the sidewall spacers, ensuring uniform vertical profiles are maintained throughout the etch process, thereby eliminating the taper and profile variations that cause feature size variations.
Solution Approach 2:
The protective spacer material acts as an intermediary layer between the etch process and the sidewall spacers. It selectively protects the top portions of the sidewall spacers during etching, mediating the interaction between the etch chemistry and the spacer structure to produce uniform vertical profiles without direct etch damage.
2Reliability
If conventional etching processes are used without protective spacers, then the etching process is simpler, but sidewall taper occurs leading to unreliable pattern transfer
Solution Approach 1:
The protective spacer is deposited in advance before the etch process to pre-establish protection on the sidewall spacers. This preliminary action ensures that when the etch process occurs, the sidewall spacers are already protected, guaranteeing reliable vertical profile transfer without requiring complex in-process adjustments or multiple etch steps.
Solution Approach 2:
The invention changes the physical and chemical parameters of the spacer structure by adding a protective layer with different etch selectivity. This parameter change transforms the etching process from one that creates tapered profiles to one that produces uniform vertical profiles, significantly improving pattern transfer reliability despite the additional deposition step.
3Length of moving object
If photolithography is used at current limits, then existing technology is utilized, but feature size reduction is no longer achievable
Solution Approach 1:
The patterning process is segmented into multiple discrete steps: forming mandrel lines, depositing sidewall spacers conformally, adding protective spacers, etching back to define gaps, filling gaps with non-mandrel material, and transferring patterns. This segmentation allows each step to be optimized independently, achieving feature size reduction while maintaining high pattern fidelity that cannot be achieved with single-step photolithography.
Solution Approach 2:
The invention transitions from two-dimensional planar photolithography to three-dimensional self-aligned multi-patterning. By utilizing vertical dimensionality through conformal spacer deposition on sidewalls and protective layer addition, the process achieves pitch multiplication and superior pattern fidelity beyond the limits of conventional planar lithography resolution.
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 significantly reduces feature size variations and ensures high pattern fidelity by maintaining a uniform and vertical spacer profile, resulting in reliable and precise pattern transfer in semiconductor integrated circuits.
Implementation Method 1
The protective spacer material is removed from horizontal surfaces of the first spacer material
Implementation Method 2
The first spacer material is etched back to the underlayer to define sidewall spacers of the first spacer material on sidewalls of each of the plurality of mandrel lines
Implementation Method 3
The sidewall spacers are anisotropically etched such that the non-mandrel lines include the protective spacer material about a top portion and the first spacer material about a bottom portion
Data Source
AI summary
Methods and structures for pitch multiplication include forming a plurality of mandrel lines and non-mandrel lines on a target layer, wherein the non-mandrel lines include a protective spacer material about a top sidewall portion and a first spacer material about a lower sidewall portion, wherein the protective spacer material has a different etch selectivity than the first spacer material. The plurality of mandrel lines and non-mandrel lines are transferred into the target layer.