VUV Curing for DSA Block Copolymer Etch Selectivity
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Solution Overview
Problem
Current methods for directed self-assembly (DSA) patterning face challenges in selectively etching one block copolymer while leaving another intact, particularly due to poor etch selectivity and pattern degradation caused by conventional wet etch processes, which result in ineffective pattern transfer.
Innovation Solution
The use of vacuum ultraviolet (VUV) light exposure in a plasma processing system to selectively harden one block copolymer and weaken another, prior to an etch process, increases etch selectivity and results in improved pattern quality with better line edge roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional wet etch process is used to remove block copolymer, then etching can be performed, but pattern collapse occurs due to high capillary forces
Solution Approach 1:
The patent replaces the conventional wet etch process (liquid chemistry) with a vapor-phase etch process. This substitution eliminates the capillary forces that cause pattern collapse during wet etching, as the vapor phase does not generate the same meniscus formation and associated capillary pressures within the nanoscale line-space patterns.
Solution Approach 2:
The patent changes the physical state parameter of the etchant from liquid (wet etch) to vapor (vapor-phase etch). This parameter change fundamentally alters the etching mechanism to avoid capillary force-induced pattern collapse while maintaining effective polymer removal capability.
2Reliability
If conventional dry etching is used to remove block copolymer, then pattern collapse is avoided, but etch selectivity between different copolymer domains is poor
Solution Approach 1:
The patent applies a preliminary oxygen plasma treatment step before the main etch process. This preliminary action selectively modifies the surface properties of the block copolymer domains, enhancing the etch selectivity between different copolymer types (e.g., PS vs. PMMA) by creating differential surface energies or chemical states that respond differently to subsequent etching.
Solution Approach 2:
The patent employs multiple plasma processing parameters including oxygen flow rate, RF power, and pressure control to optimize etch selectivity. By adjusting these parameters, the etching process can be tuned to preferentially remove one block copolymer domain while preserving another, achieving the required manufacturing precision.
3Ease of manufacture
If photoresist pattern dimensions are used directly, then patterning is simple, but critical dimensions are too large to meet design specifications
Solution Approach 1:
The patent uses directed self-assembly of block copolymers to segment the photoresist pattern into finer features. The block copolymer system naturally separates into alternating domains at the nanoscale, effectively dividing the larger photoresist features into multiple smaller lines or cylinders, thereby achieving the required critical dimensions while maintaining a relatively simple overall patterning approach.
Solution Approach 2:
The patent introduces block copolymers as an intermediary material between the photoresist pattern and the final target structure. The block copolymers self-assemble into nanoscale patterns that are transferred to the underlying layers, serving as a mediating step that enables transition from micrometer-scale photoresist features to nanometer-scale critical dimensions.
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 enables more effective etching and stronger patterns with improved line edge roughness, overcoming the limitations of conventional DSA patterning techniques.
Implementation Method 1
The substrate is irradiated with vacuum ultra violet radiation originating from plasma generated using the first process gas such that a first block copolymer increases in hardness and a second block copolymer decreases in hardness
Implementation Method 2
An etch process is executed that exposes the substrate to plasma products generated from the second process gas such that at least a portion of the second block copolymer is etched and removed from the substrate
Data Source
AI summary
Techniques disclosed herein include methods for DSA patterning and curing of DSA patterns. Techniques include curing phase-separated block copolymers using vacuum ultraviolet (VUV) light exposure at wavelengths from about 100 nanometers to 170 nanometers. VUV light can be generated using a plasma process system and from energizing various VUV-generating process gasses. A VUV curing step is executed (fully or partially) prior to executing an etch process to etch away one of the block copolymers. Such VUV exposure can selectively harden one block copolymer while weakening another block copolymer. This hardening and weakening increases etch selectivity enabling more effective etching and results in better patterns.