Self-Aligned Litho-Etch Patterning for Sub-Resolution Spacing
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Solution Overview
Problem
Double patterning techniques like litho-etch, litho-etch (LELE) face challenges with misalignment and overlay issues, limiting the end-to-end spacing between patterns to the photolithography resolution limit, which restricts further miniaturization of semiconductor devices.
Innovation Solution
A self-aligned litho-etch (SALE) process involving a multi-layer hard mask with etch rate modifying species implantation and directional etching to form etch stops, followed by spacer layer formation and directional etching to reduce edge-to-edge distance, enabling end-to-end spacing smaller than the lithographic resolution limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If double patterning techniques (litho-etch, LELE) are used to pattern critical design layers, then the ability to print sub-wavelength features is improved, but misalignment and overlay errors occur due to multiple lithography steps
Solution Approach 1:
The spacer layer automatically forms on the sidewalls of the mandrel structure through conformal deposition, creating self-aligned patterns without requiring additional lithography alignment steps. The etch stops are formed by ion implantation directly into the mandrel, ensuring precise spatial registration between the mandrel and the final patterned features
Solution Approach 2:
Etch stops are formed by ion implantation into the mandrel structure before the spacer layer is deposited. This preliminary modification of the mandrel ensures that subsequent directional etching will stop at the precisely intended location, preventing overlay errors before they can occur
2Manufacturing precision
If conventional litho-etch processes are used, then the process is simpler, but the end-to-end spacing between patterns is limited to the photolithography resolution limit
Solution Approach 1:
The process transitions from two-dimensional planar patterning to three-dimensional vertical structuring by forming spacers on the sidewalls of mandrels. This vertical dimension allows the end-to-end spacing to be determined by the mandrel dimensions and spacer thickness rather than being constrained by the lithography resolution limit
Solution Approach 2:
The patterning process is divided into distinct functional segments: mandrel formation, etch stop creation through ion implantation, spacer layer deposition, and directional etching. Each segment performs a specific function that contributes to achieving the overall goal of sub-lithographic spacing
3Manufacturing precision
If etch stops are formed by ion implantation in the mandrel, then the directional etching can achieve precise spacing, but the process complexity increases
Solution Approach 1:
The formation of etch stops and the mandrel structure are merged into a single ion implantation step. The ion implantation simultaneously creates the etch stops within the mandrel and modifies the mandrel material properties, eliminating the need for separate etch stop formation steps
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 SALE process achieves end-to-end spacing smaller than the lithographic resolution limit, enhancing device density and reducing misalignment errors, thereby facilitating the miniaturization of semiconductor devices.
Implementation Method 1
implanting an etch rate modifying species in the first layer in a portion of each of the plurality of cut shapes to form a plurality of etch stops
Implementation Method 2
The first layer is directionally etched at the plurality of cut shapes such that the plurality of etch stops remain
Data Source
AI summary
A method of defining a pattern includes forming a plurality of cut shapes and a first plurality of openings within a first layer of a multi-layer hard mask to expose first portions of the second layer. A plurality of etch stops is formed by implanting an etch rate modifying species in a portion of the plurality of cut shapes. The first layer is directionally etched at the plurality of cut shapes such that the plurality of etch stops remain. A spacer layer is formed on the first layer and the first portions. A second plurality of openings is formed within the spacer layer to expose second portions of the second layer. The spacer layer is directionally etched to remove the spacer layer from sidewalls of the plurality of etch stops. Portions of the second layer exposed through the first plurality of openings and the second plurality of openings are etched.