Double Patterning Lithography for Semiconductor Feature Resolution
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Solution Overview
Problem
The semiconductor industry faces challenges in patterning small features due to diffraction effects and proximity effects during lithography, which affect resolution, depth of focus, and feature uniformity, leading to reduced process window and yield.
Innovation Solution
A double patterning process is employed, using two masks to pattern semiconductor devices, where the first mask creates device features and printing assist features, and the second mask removes these assist features to define separating structures, thereby improving process margin and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single mask is used in lithography to pattern small features, then the manufacturing process is simple, but diffraction effects and proximity effects degrade resolution and depth of focus
Solution Approach 1:
The patent divides the patterning process into two separate exposure steps using two different masks. The first mask patterns the main device features, while the second mask patterns the separating structures. This segmentation allows each mask to be optimized for its specific function, improving overall resolution and reducing the negative effects of diffraction and proximity effects that would occur in a single exposure process.
2Reliability
If printing assist features are added to improve pattern transfer, then lithography robustness increases, but unwanted features remain that affect device performance
Solution Approach 1:
The patent extracts and removes the printing assist features after they have served their purpose during the first exposure. The second mask is specifically designed to target and remove these assist features while preserving the main device features. This extraction eliminates the harmful effects of the assist features on device performance while maintaining the benefits they provided for pattern transfer robustness.
Solution Approach 2:
The patent applies different treatments to different regions of the patterned layer. The first exposure creates both device features and assist features with enhanced printing. The second exposure then selectively removes only the assist features while leaving the device features intact. This local differentiation allows the assist features to provide their beneficial effect during patterning while eliminating their harmful presence in the final structure.
3Productivity
If feature size is reduced to increase device performance, then more circuits can be integrated, but proximity effects worsen and reduce process window
Solution Approach 1:
By segmenting the patterning into two exposures, the patent can maintain larger, more uniform features in each step while achieving high integration density overall. The separating structures created by the second mask provide adequate spacing between closely packed device features, reducing proximity effects and improving feature uniformity even as integration density increases.
Data Source
AI summary
A method includes depositing a material layer over a semiconductor substrate and using a first mask in a first exposure/patterning process to pattern the material layer thereby forming a plurality of first and second features. The first features include patterns for the semiconductor device and the second features include printing assist features. The method includes using a second mask in a second exposure/patterning process to effectively remove the second features from the material layer and to define at least one separating structure between two first features.