Developer-Soluble Anti-Reflective Coating for Lithography
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Solution Overview
Problem
Existing developer-soluble anti-reflective coatings exhibit isotropic development, leading to undercutting and line collapse issues at small feature sizes due to their narrow bake temperature window and vertical removal rates, which complicates resist loss and line integrity in advanced semiconductor lithography.
Innovation Solution
A crosslinking/decrosslinking/depolymerization mechanism using branched polymers or oligomers that become alkaline-soluble only in exposed areas, minimizing horizontal development and generating small molecules for easier removal, eliminating the need for additional crosslinking agents and broadening the bake temperature window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional polyamic acid-based wet-developable coatings are used, then the coating is soluble in alkaline developer, but the development is isotropic causing undercutting and line collapse at small feature sizes
Solution Approach 1:
The patent segments the development process into anisotropic stages: initial vertical development followed by controlled horizontal development. This segmentation allows the coating to be removed in a controlled manner that prevents undercutting while maintaining line integrity at small feature sizes.
Solution Approach 2:
The patent introduces dynamic control of the development process through sequential treatments with different developers. The process transitions from a first developer that provides vertical removal to a second developer that provides horizontal removal, creating a dynamic, multi-stage development sequence that adapts to the specific requirements of small feature patterning.
2Ease of manufacture
If thermal amic acid-to-imide conversion is used to render the coating insoluble in resist solvents, then the coating becomes developer-soluble, but the bake temperature window becomes narrow (less than 10°C)
Solution Approach 1:
The patent changes the chemical parameters of the polymer system by using polyesters and polyacrylates with specific functional groups instead of traditional polyamic acids. This parameter change allows the coating to achieve developer solubility through a different mechanism that does not rely on a narrow thermal conversion window, thereby broadening the acceptable bake temperature range.
Solution Approach 2:
The patent employs composite material systems combining polyester or polyacrylate backbones with specific side-chain functional groups. This composite structure provides both the desired alkaline developer solubility and broader thermal processing window by separating the solubility mechanism from the thermal crosslinking mechanism.
3Productivity
If isotropic wet development is used, then the coating is removed vertically at the same rate as horizontally, but this leads to line lifting and line collapse at smaller line sizes
Solution Approach 1:
The patent segments the development process into distinct vertical and horizontal removal stages using different developers. The first developer removes material primarily in the vertical direction to clear the coating from developed areas, while the second developer removes material horizontally at the base of resist lines. This segmentation prevents the simultaneous vertical and horizontal removal that causes line collapse in isotropic development.
Solution Approach 2:
The patent introduces dynamic control of development direction and rate through sequential use of different developers. The process transitions from a first development stage optimized for vertical removal to a second stage optimized for horizontal removal, creating a dynamic, adaptive development sequence that maintains line profile integrity throughout the process.
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
This approach reduces undercutting, improves imaging performance by facilitating horizontal development, and enhances the solubility of the coating in alkaline developers, allowing for more efficient and cost-effective manufacturing processes in microelectronic structure formation.
Implementation Method 1
The compound is crosslinked
Implementation Method 2
exposure of the composition to light and baking so as to decrosslink the compound and to break the compound into moieties
Data Source
Figure 1~2
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AI summary
Novel, developer-soluble anti-reflective coating compositions and methods of using those compositions are provided. The compositions comprise a multi-functional acid reacted with a multi-functional vinyl ether to form a branched polymer or oligomer. In use, the compositions are applied to a substrate and thermally crosslinked. Upon exposure to light and post-exposure baking, the cured polymers/oligomers will decrosslink and depolymerize, rendering the layer soluble in typical photoresist developing solutions (e.g., alkaline developers).