Semiconductor Patterning with Reversible Hardmask for Mixed-Density Layouts
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Solution Overview
Problem
The increasing complexity of forming patterns with various shapes, sizes, and densities in semiconductor memory devices poses challenges in process difficulty and margin maximization, particularly as feature sizes decrease.
Innovation Solution
A pattern forming method involving the creation of a hardmask structure with multiple layers, photoresist patterns, and reversible hardmask patterns to transfer shapes accurately between different areas of a semiconductor memory device, allowing for the formation of island patterns and dam structures in high-density areas and line patterns in low-density areas, using techniques like EUV lithography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional lithography methods are used to form patterns with various shapes, sizes, and densities, then the feature size decreases and integration increases, but the process difficulty increases and process margin decreases
Solution Approach 1:
The substrate is divided into multiple areas (first area with high pattern density, second area with low pattern density), and each area is processed with appropriate patterning methods. The method segments the patterning process into multiple steps including forming photoresist patterns, upper hardmask patterns, and reversible hardmask patterns in different areas to achieve optimal results for each density regime
Solution Approach 2:
Different patterning approaches are applied to different areas based on their specific requirements. The first area uses a combination of engraved and embossed patterns with reversible hardmask, while the second area uses simpler embossed patterns, optimizing each local region's pattern formation process
2Adaptability or versatility
If multiple pattern types with different shapes and sizes are formed simultaneously, then design flexibility increases, but manufacturing precision becomes more difficult to maintain
Solution Approach 1:
The method performs preliminary actions by forming multiple hardmask layers and photoresist patterns before the final etching step. The upper hardmask pattern and reversible hardmask pattern are prepared in advance with specific shapes and sizes, ensuring that when etching occurs, the patterns are transferred with high precision to the underlying layer
Solution Approach 2:
Multiple hardmask layers and photoresist patterns serve as intermediary structures that facilitate the transfer of complex patterns to the final layer. These intermediary patterns act as templates that guide the etching process, ensuring precise pattern formation even for complex shapes and sizes
3Length of moving object
If feature size is reduced to increase integration, then device capacity increases, but process margin decreases and defects increase
Solution Approach 1:
The method transitions from two-dimensional planar patterning to three-dimensional multi-layer hardmask structures. By adding vertical dimension with multiple hardmask layers (lower hardmask layer, main hardmask layer, upper hardmask layer) and using reversible hardmask filling, the process achieves better control over small feature sizes while maintaining process margin
Data Source
AI summary
A method of forming a pattern includes forming an etch target layer over a substrate including a first area and a second area, forming a hardmask structure over the etch target layer, forming a photoresist pattern including a first photoresist pattern including an engraved pattern located in the first area and a second photoresist pattern including an embossed pattern located in the second area, forming an upper hardmask pattern including a plurality of openings, forming a reversible hardmask pattern filling the plurality of openings in the first area, and forming a feature pattern including a first pattern located in the first area and a second pattern located in the second area, wherein the first pattern includes a plurality of island patterns and a dam structure planarly surrounding the plurality of island patterns.