Self-Aligned Double Patterning for Dense 2D Interconnects
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Solution Overview
Problem
Current photolithography techniques face challenges in forming dense 2D patterns for semiconductor devices due to alignment errors, tip-to-tip spacing limitations, and issues like corner rounding and pull-back, especially in advanced technologies below 10 nm, where single patterned mask layers are insufficient.
Innovation Solution
A 1D self-aligned double patterning process is employed, involving the formation of a patterning template with mandrel elements and spacers to define aligned line segment openings in a hard mask layer, followed by etching and filling recesses in a dielectric layer with conductive material, which allows for precise control of tip-to-tip spacing and minimizes pull-back and corner rounding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photolithography with single patterned mask layer is used, then the process is simple, but it cannot form dense 2D patterns with sufficient resolution for advanced technologies below 10 nm
Solution Approach 1:
The patent applies segmentation by dividing the single complex 2D pattern formation into multiple simpler patterning steps. Specifically, it uses self-aligned double patterning (SADP) to first form 1D line patterns, then combines them to create the final 2D interconnect structure. This breaks down the impossible single-step patterning into manageable sequential steps, each with relaxed resolution requirements.
Solution Approach 2:
The patent transitions from attempting to form 2D patterns directly in a single layer to forming 1D patterns that are then combined. The self-aligned double patterning process creates intermediate 1D line segments that are subsequently connected to form the 2D interconnect network, effectively using dimensional decomposition to solve the patterning challenge.
2Manufacturing precision
If traditional double patterning process is used, then multiple exposures are performed to define target pattern, but alignment errors and overlay control issues occur
Solution Approach 1:
The patent implements self-service through self-aligned double patterning, where the first patterned layer automatically serves as the alignment reference for the second pattern. The spacer formation process uses the mandrel structures as self-aligned templates, eliminating the need for separate alignment operations and overlay control that plague traditional double patterning methods.
3Manufacturing precision
If 2D interconnect patterns are formed conventionally, then the process is straightforward, but tip-to-tip spacing is limited and corner rounding and pull-back defects occur
Solution Approach 1:
The patent segments the continuous 2D pattern formation into discrete 1D line segment openings formed by self-aligned double patterning. This segmentation allows precise control of tip-to-tip spacing through the spacer thickness, avoiding the corner rounding and pull-back defects that occur in conventional 2D pattern formation where all features are exposed simultaneously.
4Quantity of substance
If feature sizes and pitches are reduced to increase device density, then device capacity increases, but existing photolithography tools cannot form patterns with sufficient resolution
Solution Approach 1:
The patent uses segmentation to achieve high device density by forming patterns in multiple steps rather than attempting to print all features at once. The self-aligned double patterning process creates intermediate patterns with relaxed pitch requirements, which are then combined to achieve the final high-density 2D interconnect structure that would be impossible to form in a single exposure.
Solution Approach 2:
The patent employs dimensional decomposition by forming 1D line patterns that are subsequently combined to create the final 2D high-density interconnect structure. This approach allows each 1D patterning step to achieve acceptable resolution with existing tools, while the combination of multiple such layers achieves the target high density that would require beyond-current-capability resolution in a single step.
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 enables the formation of 2D interconnect structures with improved scaling capabilities and reduced tip-to-tip spacing, addressing the limitations of traditional double and triple patterning processes by maintaining precise alignment and reducing defects.
Implementation Method 1
The hard mask layer is etched in the presence of the block mask and the patterning template to define aligned first and second line segment openings in the hard mask layer
Implementation Method 2
The recesses are filled with a conductive material
Data Source
AI summary
One method includes forming a mandrel element above a hard mask layer, forming first and second spacers on the mandrel element, removing the mandrel element, a first opening being defined between the first and second spacers and exposing a portion of the hard mask layer and having a longitudinal axis extending in a first direction, forming a block mask covering a middle portion of the first opening, the block mask having a longitudinal axis extending in a second direction different than the first direction, etching the hard mask layer in the presence of the block mask and the first and second spacers to define aligned first and second line segment openings in the hard mask layer extending in the first direction, etching recesses in a dielectric layer disposed beneath the hard mask layer based on the first and second line segment openings, and filling the recesses with a conductive material.