Resist Underlayer Composition for Accurate Staircase Pattern Transfer
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Solution Overview
Problem
Current pattern forming methods for 3D NAND flash memories face challenges in achieving accurate staircase-shaped patterns with excellent dry-etching resistance and film formability, particularly due to issues with thick resist underlayer films, such as cracking and insufficient adhesion to the substrate.
Innovation Solution
A pattern forming method using a composition for the resist underlayer film containing a resin with a specific constitutional unit, where the phenolic hydroxyl group proportion is adjusted to balance flowability and adhesion, along with the inclusion of an organic solvent and optional additives like base generators, crosslinking agents, and surfactants, to enhance film formability and etching resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick resist underlayer film is used to increase dry-etching resistance, then etching resistance is improved, but film formability deteriorates due to cracking and insufficient adhesion
Solution Approach 1:
The patent changes the chemical composition parameters of the resist underlayer film by incorporating specific resins with phenolic hydroxyl groups and controlling the proportion of modified phenolic hydroxyl groups (5-50%). This compositional parameter change enables the film to achieve both high dry-etching resistance and good film formability without cracking or adhesion issues
Solution Approach 2:
The patent creates a composite resist underlayer material by combining multiple resin components including phenolic resins, modified phenolic resins, and other auxiliary resins in specific proportions. This composite structure provides synergistic effects that simultaneously improve etching resistance and film formation reliability
2Strength
If the phenolic hydroxyl group proportion is increased to improve adhesion, then substrate adhesion is improved, but flowability deteriorates due to increased complex viscosity
Solution Approach 1:
The patent precisely controls the proportion of modified phenolic hydroxyl groups within 5-50% to optimize the balance between adhesion and flowability. This parameter optimization ensures sufficient substrate adhesion while maintaining adequate flowability for uniform film formation
Solution Approach 2:
The patent formulates a composite resin system that combines phenolic resins with modified phenolic resins and other auxiliary resins. This composite approach allows the material to exhibit both strong adhesion properties and adequate flowability that cannot be achieved with single-component resins
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
The method enables the accurate transfer of staircase-shaped patterns to the substrate with improved film formability, adhesion, and dry-etching resistance, suitable for high-aspect-ratio structures and complex patterns in 3D NAND flash memory fabrication.
Implementation Method 1
a base generator (C) which generates a base by thermal decomposition
Implementation Method 2
a crosslinking agent (D) which promotes crosslinking reaction upon generation of the base
Implementation Method 3
applying a composition for forming a resist underlayer film on a substrate to be processed and thereafter performing heat treatment to form a resist underlayer film
Data Source
AI summary
The present invention is a pattern forming method includes steps of: forming a resist underlayer film by using a composition for forming a resist underlayer film on a substrate to be processed; forming a resist middle layer film on the resist underlayer film; forming a resist upper layer film on the resist middle layer film; forming a pattern in the resist upper layer film; transferring the pattern to the resist middle layer film; transferring the pattern to the resist underlayer film; forming the pattern in the substrate to be processed; trimming the resist underlayer film; and forming a staircase-shaped pattern in the substrate to be processed. The composition for forming a resist underlayer film contains a resin and an organic solvent. The resin represented by the following formula (1) is used. This provides: a pattern forming method capable of accurately forming a staircase-shaped pattern by using a composition for forming a resist underlayer film having excellent dry-etching resistance over conventional KrF resists and having excellent film formability and substrate adhesion.