Antireflective Coating Composition for EUV Lithography
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Solution Overview
Problem
In microlithography, existing antireflective coatings fail to adequately address back reflection issues from highly reflective substrates, leading to thin film interference and reflective notching, which distort image uniformity and cause line width variations, especially in extreme ultraviolet (EUV) lithographic processes.
Innovation Solution
A novel antireflective coating composition comprising a crosslinkable polymer with a backbone containing phenyl, hydroxybiphenyl, and fused aromatic units, which forms a high carbon content, self-crosslinking film that reduces reflections and enhances pattern transfer, used as a hard mask under a silicon antireflective coating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional antireflective coatings are used on highly reflective substrates, then back reflection is reduced, but thin film interference and reflective notching occur causing line width variations
Solution Approach 1:
The patent employs a composite antireflective coating system consisting of multiple layers with different materials and properties. The bottom antireflective coating layer (BARC) is formulated with specific polymers containing aromatic rings and hydroxy groups, while a top antireflective coating layer is applied above it. This multi-layer composite structure addresses back reflection through combined absorption and interference mechanisms, preventing both thin film interference and reflective notching effects that plague single-layer coatings.
Solution Approach 2:
The invention applies different material compositions and thicknesses to different layers of the antireflective coating system. The bottom layer is specifically designed with high carbon content polymers for maximum absorption, while the top layer is optimized for etch resistance and pattern fidelity. Each layer performs a specialized function, with the bottom layer primarily absorbing reflections and the top layer providing mechanical stability and etch mask properties, thereby achieving uniform line width control.
2Measurement precision
If the photoresist layer is made thinner to achieve higher resolution, then imaging precision improves, but the photoresist becomes more susceptible to reflective notching and loses etch resistance
Solution Approach 1:
The patent introduces an intermediary bottom antireflective coating layer positioned between the photoresist and the reflective substrate. This intermediate layer serves multiple functions: it absorbs back reflections before they can cause notching in the thin photoresist, provides additional etch resistance to protect the delicate high-resolution pattern, and prevents direct interaction between the photoresist and substrate. This mediator layer enables the use of thinner photoresist for high-resolution imaging without sacrificing etch resistance.
Solution Approach 2:
The invention changes the optical and physical parameters of the coating system by introducing a bottom antireflective layer with specific absorption characteristics (high carbon content, aromatic ring structures). This parameter change in the underlying layer compensates for the reduced thickness of the photoresist, maintaining sufficient etch resistance and protecting against reflective notching while allowing the photoresist to be optimized for high-resolution imaging.
3Object-affected harmful factors
If a thicker antireflective coating is applied to improve absorption, then back reflection is better suppressed, but the coating becomes more prone to intermixing with photoresist during processing
Solution Approach 1:
The patent divides the antireflective coating into segmented layers: a bottom antireflective coating layer (BARC) and a top antireflective coating layer. The bottom layer is formulated with high carbon content polymers for superior absorption of back reflections, while the top layer is designed with enhanced etch resistance and compositional stability. This segmentation allows the bottom layer to be thicker for maximum absorption without compromising overall coating integrity, as the top layer protects against intermixing with the photoresist during subsequent processing steps.
Solution Approach 2:
The invention changes the compositional parameters of the antireflective coating system by using distinct polymer formulations in different layers. The bottom layer employs polymers with high aromatic ring content and specific hydroxy groups for optimal absorption, while the top layer uses polymers optimized for thermal and chemical stability during photoresist processing. This parameter differentiation across layers enables thick bottom layers for absorption without intermixing issues.
4Manufacturing precision
If multiple antireflective layers are used to overcome limitations, then lithographic performance improves, but the process complexity and number of steps increase
Solution Approach 1:
The patent designs the bottom antireflective coating layer to perform multiple functions simultaneously: it absorbs back reflections, provides etch resistance, prevents reflective notching, and serves as an adhesion promoter between the substrate and photoresist. The top antireflective layer similarly provides both optical performance and mechanical protection. This multi-functionality reduces the need for additional separate layers or process steps, achieving improved lithographic performance without proportionally increasing process complexity.
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 composition achieves high resolution image transfer with high aspect ratio, reduces intermixing with the photoresist, and maintains high carbon content even after baking, thereby improving lithographic performance and preventing pattern distortion during plasma etching.
Implementation Method 1
The present invention relates to an absorbing hard mask antireflective coating composition comprising a polymer, where the polymer comprises in the backbone of the polymer at least one phenyl unit, at least one hydroxybiphenyl unit, and at least one substituted or unsubstituted fused aromatic ring
Implementation Method 2
a crosslinkable polymer capable of being crosslinked with the crosslinker, where the polymer comprises at least one unit with a phenyl group in the backbone of the polymer, at least one unit with fused aromatic rings in the backbone of the polymer, and at least one unit with hydroxybiphenyl
Data Source
Figure 1
AI summary
The invention relates to an antireflective coating composition comprising a crosslinker and a crosslinkable polymer capable of being crosslinked by the crosslinker, where the crosslinkable polymer comprises a unit represented by structure (1 ), where A is a fused aromatic ring, B has a structure (2), and C is a hydroxybiphenyl of structure (3), (2) and (3) where R1 is C1-C4alkyl and R2 is C1-C4alkyl. The invention further relates to a process for forming an image using the composition.