Double Hardmask Pattern Transfer for Vertical Sidewall Multipatterning
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Solution Overview
Problem
Conventional self-aligned double patterning processes suffer from leaned mask profiles, leading to critical dimension variations, recess depth variations, pitch walking, and high line edge roughness, which compromise the uniformity and precision of semiconductor feature fabrication.
Innovation Solution
Employing a double hardmask process involving a mask stack comprising a lower hardmask, middle mask, and upper hardmask, with selective etching to correct leaned mask profiles, ensuring vertical sidewalls and improved uniformity by etching each mask layer sequentially.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional self-aligned double patterning processes are used, then the manufacturing process is simple, but the mask profile becomes leaned leading to critical dimension variations and poor uniformity
Solution Approach 1:
The mask layer is segmented into multiple hardmask layers (lower hardmask, middle mask, upper hardmask) with different materials and etch selectivities. Each layer is selectively etched to transfer the pattern sequentially, correcting the leaned mask profile at each step and achieving vertical sidewalls in the final pattern.
Solution Approach 2:
Different regions of the mask stack are assigned different material properties and etch selectivities. The lower hardmask, middle mask, and upper hardmask each have tailored characteristics that enable selective etching, allowing local correction of mask leaning while maintaining overall pattern fidelity.
2Shape
If conventional single hardmask process is used, then the process complexity is low, but the sidewalls are not vertical leading to pitch walking and high line edge roughness
Solution Approach 1:
The etching process is segmented into multiple selective etch steps, each targeting a specific hardmask layer. The first etch selectively removes the upper hardmask, the second etch selectively removes the middle mask, and the third etch selectively removes the lower hardmask. This segmented approach ensures vertical sidewalls at each stage, preventing pitch walking and line edge roughness.
Solution Approach 2:
The etch selectivity parameters are changed between different etch steps by adjusting process conditions and selecting appropriate etch chemistries for each hardmask layer. This allows precise control over which layer is etched at each step, ensuring vertical sidewall formation throughout the multi-layer patterning process.
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 achieves improved uniformity and precision in semiconductor feature fabrication by minimizing mask leaning and critical dimension variations, enhancing the quality of final patterns.
Implementation Method 1
etching the upper hardmask, selectively to the middle mask, to transfer the initial pattern to the upper hardmask
Implementation Method 2
etching the middle mask, selectively to the lower hardmask and the patterned upper hardmask, to transfer a pattern of the patterned upper hardmask to the middle mask
Implementation Method 3
etching the lower hardmask, selectively to the patterned middle mask, to transfer a pattern of the patterned middle mask to the lower hardmask
Data Source
AI summary
A method of processing a substrate that includes: forming recesses in a first mask layer over a mask stack including a lower hardmask, a middle mask, and an upper hardmask, the recesses defining an initial pattern including a plurality of spacer structures, each of the spacer structures having a first sidewall and an opposite second sidewall, the first sidewall having a different height from the second sidewall; etching the upper hardmask, selectively to the middle mask, to transfer the initial pattern to the upper hardmask; etching the middle mask, selectively to the lower hardmask and the patterned upper hardmask, to transfer a pattern of the patterned upper hardmask to the middle mask; and etching the lower hardmask, selectively to the patterned middle mask, to transfer a pattern of the patterned middle mask to the lower hardmask.