Double Patterning Contact Hole Etching via Gradient Etch Stop Layers
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Solution Overview
Problem
Conventional double patterning processes for semiconductor technologies face challenges in maintaining desired critical dimensions for high aspect ratio resist layers, particularly at small feature sizes, due to high manufacturing costs and low throughput.
Innovation Solution
A double patterning method involving multiple etching processes with a gradient composition of etch stop layers and a hard mask layer, using positive and negative resist patterns to form intermediate and final hard mask features, allowing for reduced feature size through a series of lithography and etching steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional double patterning processes are used to form small feature sizes, then manufacturing precision is improved, but productivity deteriorates due to low throughput
Solution Approach 1:
The patent segments the patterning process into multiple lithography and etching steps (first and second patterning processes) to achieve smaller feature sizes. Each pattern layer is formed separately with intermediate hard mask features, allowing precise control of critical dimensions while maintaining throughput through efficient process integration.
Solution Approach 2:
The patent applies preliminary action by forming intermediate hard mask features before the final patterning step. The first pattern layer and first hard mask features are prepared in advance, creating a foundation that enables subsequent patterning steps to achieve higher precision without compromising overall process efficiency.
2Manufacturing precision
If multiple etching processes are used in conventional double patterning, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent introduces intermediate hard mask features as mediators between the first and second patterning processes. These intermediate features serve as temporary structures that guide the formation of final patterns, simplifying the overall process complexity by providing clear process milestones and reducing the need for complex single-step etching.
Solution Approach 2:
The patent applies local quality by using different resist types (positive and negative) and different hard mask materials in different regions of the process. The first pattern layer uses positive resist while the second uses negative resist, and intermediate hard mask features are formed with specific materials optimized for their local etching requirements, enabling precise feature size control through localized process optimization.
3Manufacturing precision
If high aspect ratio resist layers are used to achieve small feature sizes, then manufacturing precision is improved, but reliability deteriorates due to difficulty in maintaining critical dimension
Solution Approach 1:
The patent transitions from relying solely on vertical resist layer thickness (one dimension) to using lateral hard mask feature dimensions (another dimension) to define final feature sizes. By forming intermediate hard mask features with controlled lateral dimensions through lithography, the process achieves small feature sizes with better critical dimension stability, as the hard mask features provide robust dimensional control independent of resist layer aspect ratio.
Data Source
AI summary
A method of lithography patterning includes forming a first etch stop layer, a second etch stop layer, and a hard mask layer on a material layer. The materials of the first etch stop layer and the second etch stop layer are selected by the way that there is a material gradient composition between the second etch stop layer, the first etch stop layer, and the material layer. Hence, gradient etching rates between the second etch stop layer, the first etch stop layer, and the material layer are achieved in an etching process to form etched patterns with smooth and/or vertical sidewalls within the second and the first etch stop layers and the material layer.