BEOL Mandrel Patterning With Self-Aligned Sub-15 Nm Pitch Lines
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Solution Overview
Problem
Current technologies face challenges in achieving reliable sub-15 nm pitch mandrel patterning for back-end-of-line (BEOL) self-aligned-litho-etch-litho-etch (SALELE) processes, as the number of defects increases with smaller scales, making it difficult to form mandrels with a pitch equal to or less than 30 nm.
Innovation Solution
A method involving self-aligned double patterning (SADP) is used to form conductive metal mandrels with sub-15 nm pitch, including mandrels of constant and varied widths, by creating a multi-layered hard mask, forming spacers, and transferring patterns through a series of etching steps to achieve precise patterning without requiring sub-30 nm pitch mandrel patterning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional SALELE process is used for sub-30 nm pitch mandrel patterning, then manufacturing process is simpler, but manufacturing precision deteriorates due to increased defect formation at smaller scales
Solution Approach 1:
The patent divides the patterning process into multiple discrete steps including forming first mandrels, depositing first spacers, removing first mandrels, forming second mandrels, depositing second spacers, and performing self-aligned double patterning. Each step is optimized independently to achieve sub-15 nm pitch precision while managing overall process complexity through systematic segmentation of the manufacturing workflow
Solution Approach 2:
The patent transitions from direct planar patterning to multi-layered three-dimensional patterning by forming mandrels and spacers in vertical layers. The multi-layered hard mask structure and sequential spacer formation around mandrels create patterns in multiple dimensions, enabling precise sub-15 nm pitch control that cannot be achieved with conventional two-dimensional lithographic approaches alone
2Quantity of substance
If pitch is reduced to sub-15 nm for BEOL SALELE, then device density is improved, but reliability deteriorates due to increased number of defects at smaller scales
Solution Approach 1:
The self-aligned double patterning process inherently aligns second mandrels and spacers to the first mandrel structures without requiring additional alignment steps or external guidance. This self-alignment mechanism eliminates alignment errors that would otherwise introduce defects, enabling reliable sub-15 nm pitch patterning while achieving high device density through precise self-correcting pattern formation
Solution Approach 2:
The patent employs multiple parameter changes including varying mandrel widths (constant and varied width mandrels), adjusting spacer thicknesses, and modifying etch selectivities to optimize pattern fidelity at sub-15 nm pitches. These parameter adjustments compensate for scaling effects and maintain pattern reliability as dimensions are reduced to increase device density
Data Source
AI summary
A method of semiconductor manufacture comprising forming a plurality of first mandrels as the top layer of the multi-layered hard mask and forming a first spacer around each of the plurality of first mandrels. Removing the plurality of first mandrels and cutting the first spacer to form a plurality of second mandrels. Forming a second spacer around each of the plurality of second mandrels and forming a first self-aligned pattern that includes a plurality of third mandrels. Removing the plurality of second mandrels and the second spacer and etching the multi-layered hard mask to transfer the first-self aligned pattern to a lower layer of the multi-layered hard mask. Forming a second self-aligned pattern, wherein the second self-aligned pattern is intermixed with the first self-aligned pattern and etching the first self-aligned pattern and the second self-aligned pattern into the conductive metal layer.