Directed Self Assembly Lithography Hard Mask
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Solution Overview
Problem
Conventional Directed Self Assembly (DSA) lithography processes face challenges in maintaining pattern integrity and etching selectivity due to the adverse effects of high temperature annealing on photo resist and limited pitch of PS strips, which affects the precision and quality of patterned features.
Innovation Solution
The process involves forming a hard mask layer and a Bulk Co-Polymer (BCP) coating comprising PS and PMMA, with phase separation guided by a neutralized layer or chemical treatment, allowing for selective etching of PMMA strips and using the remaining PS strips as an etching mask to pattern the underlying layer, thereby avoiding the limitations of photo resist degradation and enhancing pattern precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high temperature annealing is used to cause phase separation in BCP, then the PS and PMMA separate into parallel strips, but the photo resist degrades and pattern integrity is lost
Solution Approach 1:
The patent introduces an inorganic membrane layer as an intermediary between the photo resist and the BCP coating. This membrane layer serves as a thermal buffer that protects the photo resist from direct exposure to high annealing temperatures while still allowing the BCP phase separation to occur. The membrane layer absorbs or blocks harmful thermal effects, enabling the annealing process to proceed without degrading the photo resist pattern.
Solution Approach 2:
The patent segments the structure into distinct functional layers: photo resist layer, inorganic membrane layer, and BCP coating layer. This segmentation allows each layer to perform its specific function independently - the photo resist defines the initial pattern, the inorganic membrane protects during thermal processing, and the BCP forms the final self-assembled structure. This layered segmentation resolves the contradiction by isolating the photo resist from harmful thermal effects.
2Manufacturing precision
If conventional DSA process is used with photo resist, then lithography patterning is achieved, but the pitch of PS strips is limited affecting precision
Solution Approach 1:
The patent employs self-service by allowing the BCP coating to self-assemble into periodic strip patterns through phase separation driven by thermodynamic forces. The inorganic membrane layer provides a controlled environment that enables this self-organization to occur with high precision. The system uses its own internal energy and material properties to achieve the desired pattern without requiring external intervention for each patterning step, thereby achieving both precision and flexibility.
Solution Approach 2:
The patent changes key parameters of the system - specifically using an inorganic membrane layer with specific thermal and surface properties that enable the BCP to undergo phase separation at controlled temperatures and form strips with adjustable pitch. By modifying the membrane layer composition, thickness, and surface energy, the pitch of the resulting PS strips can be precisely controlled, overcoming the limitations of conventional photo resist-based approaches.
3Stability of the object's composition
If annealing temperature is increased to improve phase separation, then strip formation is enhanced, but photo resist integrity deteriorates
Solution Approach 1:
The inorganic membrane layer acts as a thermal intermediary that decouples the annealing temperature required for good phase separation from the temperature tolerance of the photo resist. The membrane layer has thermal properties that allow it to withstand high temperatures while protecting the underlying photo resist, enabling the system to achieve both high phase separation quality and photo resist stability simultaneously.
Solution Approach 2:
The patent applies beforehand cushioning by placing the heat-resistant inorganic membrane layer between the photo resist and the BCP coating before the annealing process. This pre-positioned protective layer cushions the photo resist against thermal shock and sustained high-temperature exposure, allowing the subsequent annealing to proceed at temperatures that optimize phase separation without compromising photo resist integrity.
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 maintains pattern precision and etching selectivity, reducing the adverse effects of high temperature annealing and allowing for closer spaced, high precision features suitable for advanced semiconductor structures like FinFETs, while ensuring the hard mask layer sustains the annealing temperature without deformation.
Implementation Method 1
An anneal step is then performed to cause a phase separation in the BCP, so that the PS and PMMA are separated into parallel strips
Implementation Method 2
phase separation is achieved using chemicals or UV light
Data Source
AI summary
A method includes forming a patterned hard mask layer, with a trench formed in the patterned hard mask layer, dispensing a Bulk Co-Polymer (BCP) coating in the trench, wherein the BCP coating comprises a mix of a first material and a second material different from the first material. The method further includes treating the BCP coating with a chemical to form a first plurality of strips of the first material and a second plurality of strips of the second material, with the first plurality of strips and the second plurality of strips allocated in an alternating layout. The second plurality of strips is selectively etched, and the first plurality of strips is left in the trench.