Staggered Trench Bit Line Formation via Dual Mask Etching
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Solution Overview
Problem
The challenge in semiconductor manufacturing is the difficulty in forming conductive patterns with high productivity, particularly in creating bit lines, due to the narrow width of line patterns and the need for a trim process to separate them, which complicates the damascene process.
Innovation Solution
A method is developed to form conductive patterns by creating a staggered pattern of trenches on a substrate using a first and second mask with uneven boundaries, allowing for the omission of the trimming process by arranging first and second trenches alternately and repeatedly, and filling them with conductive material to form bit lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a damascene process is used to form line patterns, then the line patterns can be formed with reduced width, but a trim process is required to separate each line pattern, reducing productivity
Solution Approach 1:
The patent divides the formation of separated line patterns into two stages: first forming continuous line patterns with a first mask, then forming a second mask with openings that selectively expose portions of the continuous lines. This segmentation allows the trim process to be integrated into the masking sequence rather than being a separate post-processing step, thereby maintaining precision while improving productivity.
Solution Approach 2:
The patent performs preliminary actions by forming the first mask and continuous line patterns before forming the second mask. The second mask is then patterned with openings that define the final separated line pattern geometry. This preliminary formation of continuous lines followed by selective removal allows for more efficient processing compared to attempting to form separated lines directly.
2Productivity
If the line pattern width is reduced for high integration, then device integration is improved, but the difficulty of patterning metal layers increases
Solution Approach 1:
The patent transitions from attempting to pattern narrow metal lines directly in the planar dimension to forming continuous lines first, then using a second mask layer with openings to define the final pattern. This two-dimensional approach to pattern formation (using stacked mask layers) circumvents the direct patterning difficulty of narrow lines while achieving the desired integration density.
Solution Approach 2:
The patent introduces continuous line patterns as an intermediary structure between the initial mask and the final separated line patterns. These continuous lines serve as a intermediate form that is easier to form than the final narrow separated lines, and from which the final pattern can be derived through the second masking step.
3Manufacturing precision
If a trim process is added to separate line patterns, then pattern separation is achieved, but process complexity and manufacturing time increase
Solution Approach 1:
The patent merges the trim process functionality into the mask formation sequence by forming a second mask layer with openings that simultaneously serve as both the pattern definition layer and the trim guide. This integration eliminates the need for a separate trim process step, reducing overall process complexity while maintaining pattern separation precision.
Solution Approach 2:
The second mask layer serves multiple functions: it defines the openings for the final line pattern, acts as an etching mask for removing material to create separations, and provides a template for the trim process. This multi-functionality reduces the number of dedicated process steps needed while achieving the same pattern separation result.
Data Source
AI summary
An insulation layer is formed on a substrate. A first mask is formed on the insulation layer. The first mask includes a plurality of line patterns arranged in a second direction. The plurality of line patterns extend in a first direction substantially perpendicular to the second direction. A second mask is formed on the insulation layer and the first mask. The second mask includes an opening partially exposing the plurality of line patterns. The opening has an uneven boundary at one of a first end portion in the first direction and a second end portion in a third direction substantially opposite to the first direction. The insulation layer is partially removed using the first mask and the second mask as an etching mask, thereby forming a plurality of first trenches and second trenches. The plurality of first trenches and the second trenches are arranged in a staggered pattern.