Dual Mask Etch Process for Semiconductor Critical Dimension Control
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Solution Overview
Problem
Current photolithography methods face challenges in achieving precise critical dimensions for semiconductor devices due to the resolution limits of optical exposure tools, particularly as IC size decreases and density increases, leading to issues with feature size consistency and the presence of ghost features.
Innovation Solution
A dual print/dual etch process flow using two masking layers, where the first mask layer patterns initial features, and the second mask layer trims or grows these features, allowing for the removal of ghost features and enabling tighter pitches and smaller structures by exploiting different physical characteristics and etching processes of each mask layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single mask layer is used for patterning, then the process is simple and fast, but the critical dimension control is poor and feature size variation is high
Solution Approach 1:
The single mask layer is segmented into two distinct mask layers with different compositions (inorganic and organic). Each mask layer performs a specific function: the first mask layer defines the initial feature pattern, while the second mask layer trims or grows the features to achieve precise critical dimensions. This segmentation allows independent optimization of each mask's properties and functions, resolving the contradiction between precision and complexity.
Solution Approach 2:
The patent employs composite masking by combining two mask layers with different material compositions (inorganic and organic materials). This composite approach leverages the complementary properties of each material type to achieve superior critical dimension control that cannot be obtained with a single material, directly addressing the precision-complexity tradeoff.
2Manufacturing precision
If optical exposure tools are used with current resolution limits, then the equipment is readily available, but the minimum feature size is constrained
Solution Approach 1:
The first mask layer performs preliminary patterning to define the initial feature locations and rough dimensions. This preliminary action allows the subsequent second mask layer to focus specifically on fine-tuning the critical dimensions through trimming or growth, thereby achieving minimum feature sizes below the direct optical resolution limit while using conventional exposure tools.
Solution Approach 2:
The patent changes the physical and chemical parameters of the masking system by introducing two mask layers with different compositions and etching characteristics. This parameter change enables the system to achieve finer feature dimensions than the optical resolution limit would suggest, as the dual-mask approach allows for more precise control over the etching process and feature formation.
3Productivity
If tighter pitches and smaller structures are patterned, then device density increases, but ghost features and dimension variation worsen
Solution Approach 1:
The first mask layer acts as an intermediary structure that defines the initial pattern framework. This intermediary pattern allows the second mask layer to precisely control the final feature dimensions through trimming or growth operations, thereby maintaining feature size consistency even as device density increases and pitches tighten. The intermediary mask mediates between the optical exposure limitations and the final precise feature requirements.
Data Source
AI summary
In accordance with the invention, there are methods of making an integrated circuit, an integrated circuit device, and a computer readable medium. A method can comprise forming a first layer over a semiconductor substrate, forming a first mask layer over the semiconductor substrate, and using the first mask layer to pattern first features. The method can also include forming a second mask layer over the first features, using the second mask layer to pattern portions of the first features, removing the second mask layer, and removing the first mask layer.