Semiconductor Patterning Method Using Three Memorization Layers
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Solution Overview
Problem
Current patterning methods in semiconductor fabrication, such as litho-etch and spacer-assisted multiple patterning techniques, face challenges in achieving aggressive critical dimensions due to sensitivity to process variability, particularly edge placement errors, which limits the formation of tight pitch patterns with small tip-to-tip separation.
Innovation Solution
A patterning method involving a layer stack of three memorization layers, where each layer is used multiple times to form trench patterns, utilizing lithography and etching processes combined with spacer-assisted techniques to create interrupted trenches with improved edge placement error margins, allowing for tighter pitch patterns and reduced sensitivity to process variability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If spacer-assisted multiple patterning techniques are used to form tight pitch patterns, then critical dimensions are reduced, but sensitivity to edge placement errors increases
Solution Approach 1:
The patent divides the patterning process into multiple sequential litho-etch steps, where each step forms a portion of the final pattern. The first litho-etch forms initial trenches, spacer lines are deposited, then a second litho-etch forms additional trenches. This segmentation allows each litho-etch step to work with relaxed pitch requirements while achieving an aggregate tight pitch pattern, thereby reducing sensitivity to edge placement errors in any single step.
Solution Approach 2:
The patent performs preliminary patterning actions by forming mandrel lines and spacer lines before forming the final trench patterns. The spacer lines are deposited and patterned in advance to define the pitch for subsequent trench formation. This preliminary action establishes a framework that guides the final patterning steps, allowing for better control over edge placement and reducing sensitivity to variability.
2Manufacturing precision
If aggressive target critical dimensions are pursued, then pattern density increases, but process variability sensitivity increases
Solution Approach 1:
The patent segments the complex patterning task into multiple simpler litho-etch steps, each operating at relaxed pitch. The first step forms trenches at a relaxed pitch, spacer lines are deposited, then the second step forms additional trenches. This segmentation allows each step to achieve good precision without being pushed to the limits of lithographic resolution, thereby reducing overall process variability.
Solution Approach 2:
The patent introduces spacer lines as intermediary structures between the lithographically defined mandrels and the final trench patterns. These spacer lines act as a buffer that decouples the lithographic precision requirements from the final pattern dimensions. The spacer width, controlled by conformal deposition, determines the final pitch, reducing sensitivity to lithographic edge placement variability.
3Area of stationary object
If tight pitch patterns with small tip-to-tip separation are formed, then area utilization improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent segments the trench formation into two separate litho-etch processes, where the first process forms trenches with adequate spacing, and the second process forms additional trenches in the spaces between. This segmentation allows each process to maintain adequate tip-to-tip separation, avoiding the precision challenges of forming all trenches in a single tight-pitch step.
Solution Approach 2:
The patent transitions from a two-dimensional planar patterning approach to a three-dimensional approach using vertical spacer deposition. By depositing spacers conformally on the sidewalls of mandrels, the pitch control is moved from the lateral lithographic dimension to the vertical deposition dimension, enabling tighter effective pitch while maintaining relaxed lithographic requirements.
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 method enables the formation of trench patterns with smaller critical dimensions and increased flexibility in shape, reducing sensitivity to process variability and edge placement errors, thereby facilitating the creation of comparably tight pitch patterns with improved reliability.
Implementation Method 1
lithography and etching processes... to form trenches, openings, or other patterns... A pattern such as a trench pattern may be lithographically defined (i.e., exposed and developed) in a resist layer
Implementation Method 2
patterning the upper memorization layer using lithography and etching to form upper trenches... patterning the intermediate memorization layer and the lower memorization layer to form intermediate trenches...
Implementation Method 3
forming sidewall spacer lines along sidewalls of the upper trenches... spacer-assisted (SA) technique... makes it possible to ensure at least minimum separation between adjacent trenches
Data Source
AI summary
A method that provides patterning of an underlying layer to form a first set of trenches and a second set of trenches in the underlying layer is based on a combination of two litho-etch (LE) patterning processes supplemented with a spacer-assisted (SA) technique. The method uses a layer stack comprising three memorization layers: an upper memorization layer allowing first memorizing upper trenches, and then one or more upper blocks; an intermediate memorization layer allowing first memorizing intermediate trenches and one or more first intermediate blocks, and then second intermediate blocks and intermediate lines; and a lower memorization layer allowing first memorizing first lower trenches and one or more first lower blocks, and then second lower trenches and one or more second lower blocks.