Hard Mask Directed Self Assembly Lithography
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Solution Overview
Problem
Conventional Directed Self Assembly (DSA) processes face issues with the photo resist being adversely affected by high annealing temperatures, leading to footing problems and limited pitch of PS strips due to the adverse profile of the photo resist, which restricts the directionality and precision of PS-PMMA strip formation.
Innovation Solution
The use of a hard mask layer that sustains high temperatures, guiding the direction of PS-PMMA strip formation and eliminating the adverse effects on the photo resist, with a BCP coating comprising PS and PMMA being annealed to form alternating strips, where PS strips are used as an etching mask for an underlying layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If photo resist is used to guide BCP coating during annealing, then the annealing step can be performed, but the photo resist is adversely affected by high temperatures leading to footing problems and limited pitch
Solution Approach 1:
The patent introduces a hard mask layer as an intermediary between the pattern definition layer and the BCP coating. This hard mask layer serves as the guiding structure during annealing instead of the photo resist, allowing high-temperature processing without damaging the photo resist profile. The hard mask layer withstands the thermal stress while maintaining the directional guidance for PS-PMMA strip formation.
2Device complexity
If photo resist is used as the guiding structure, then the process can be simplified, but the pitch of PS strips is limited due to adverse profile
Solution Approach 1:
The patent segments the guiding function from the photo resist by introducing a separate hard mask layer. This segmentation allows the photo resist to be used only for initial patterning while the hard mask layer provides the sustained guidance during high-temperature annealing, enabling better pitch control without significantly increasing overall process complexity.
3Stability of the object's composition
If high temperature annealing is performed, then phase separation in BCP is achieved, but photo resist footing problems occur
Solution Approach 1:
The hard mask layer acts as a thermal intermediary that protects the photo resist from direct exposure to high annealing temperatures. The hard mask layer absorbs and withstands the thermal stress, preventing the photo resist from experiencing footing problems while still allowing the BCP coating to undergo necessary phase separation for strip formation.
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 enhances the precision and directionality of PS-PMMA strip formation, reducing the adverse effects of high annealing temperatures on the photo resist and allowing for a wider pitch range of PS strips, thereby improving the lithography process's accuracy and efficiency.
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
Data Source
AI summary
A method includes forming a patterned hard mask layer, with a trench formed in the patterned hard mask layer. A Bulk Co-Polymer (BCP) coating is dispensed in the trench, wherein the BCP coating includes Poly-Styrele (PS) and Poly Methyl Metha Crylate (PMMA). An annealing is performed on the BCP coating to form a plurality of PS strips and a plurality of PMMA strips allocated in an alternating layout. The PMMA strips are selectively etched, with the PS strips left in the trench.