Acid-Sensitive Bottom Anti-Reflective Coatings for Microlithography
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Solution Overview
Problem
Current bottom anti-reflective coatings used in microelectronic manufacturing lack the resolution and processing latitude required for critical microlithography applications, especially at smaller feature sizes, and traditional dry development methods can damage plasma-sensitive layers and require reactive ion etching.
Innovation Solution
A wet-developable bottom anti-reflective coating composition is formed using a crosslinkable polymer with adamantyl methacrylate monomers and a multifunctional crosslinker, which is acid-labile and decrosslinkable with acid diffusion, allowing for selective removal of exposed portions without damaging unexposed areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If wet-developable bottom anti-reflective coatings are used, then the etch budget is increased and damage to plasma-sensitive layers is minimized, but the resolution is lower compared to dry bottom anti-reflective coatings
Solution Approach 1:
The patent modifies the chemical composition parameters of the polymer by incorporating specific monomers (styrene, methacrylic acid, and acid-labile monomers in controlled ratios) to optimize both solubility for wet development and resistance to maintain resolution. This compositional parameter change enables the coating to achieve high resolution while remaining compatible with wet development processes.
Solution Approach 2:
The patent creates a composite polymer system combining multiple monomer types (styrene for structural integrity, methacrylic acid for solubility control, and acid-labile monomers for selective removal) to achieve properties that individual materials cannot provide alone. This composite approach enables simultaneous optimization of resolution and wet-developability.
2Manufacturing precision
If traditional dry development methods are used, then high resolution is achieved, but reactive ion etching is required and plasma-sensitive layers are damaged
Solution Approach 1:
The patent replaces the mechanical/chemical etching process (reactive ion etching) with a chemical dissolution process (wet development using aqueous TMAH). The polymer is formulated to be soluble in aqueous base developers, allowing pattern transfer through dissolution rather than etching, thereby eliminating damage to plasma-sensitive layers while maintaining resolution.
Solution Approach 2:
The patent changes the chemical parameters of the polymer to include hydrophilic groups and controlled crosslinking density that enable solubility in aqueous TMAH developer. This parameter change allows the coating to be removed via wet development instead of requiring reactive ion etching, eliminating plasma damage while preserving pattern fidelity.
3Manufacturing precision
If the polymer is made highly crosslinked to improve resolution, then manufacturing precision increases, but the coating becomes less soluble in developer
Solution Approach 1:
The patent optimizes the crosslinking parameter by controlling the ratio of acid-labile monomers to other monomers and adjusting crosslinking density. The polymer is designed with moderate crosslinking (not excessive) to maintain pattern definition while preserving sufficient solubility in aqueous TMAH. The acid-labile groups provide controlled solubility enhancement upon exposure.
Solution Approach 2:
The patent incorporates acid-labile groups into the polymer structure before exposure, which serve as pre-positioned solubility enhancement sites. Upon exposure to light, these groups are converted to carboxylic acids that dramatically increase water solubility, enabling developer removal without requiring high initial crosslinking density.
4Adaptability or versatility
If acid-labile monomers are incorporated to enable selective removal, then processing latitude is improved, but the polymer composition becomes more complex
Solution Approach 1:
The patent uses a limited set of well-defined acid-labile monomers (such as t-butyl methacrylate or carbobenzoxy methacrylate) with known photodeprotection characteristics. By selecting specific monomers with established properties and controlling their concentration (typically 5-20 mol%), the patent achieves processing latitude without excessive compositional complexity. The synthesis and characterization protocols for these monomers are well-established in the field.
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 coating provides improved resolution and processing latitude for critical microlithography, eliminating the need for reactive ion etching and minimizing damage to sensitive layers, while maintaining excellent reflectivity control and compatibility with photoresists.
Implementation Method 1
The polymer comprises recurring monomeric units having adamantyl groups selected from the group consisting of adamantyl methacrylate monomers, and recurring monomeric units having acid groups, said adamantyl groups being acid-labile
Implementation Method 2
forming an anti-reflective layer on said surface, said anti-reflective layer being formed from an anti-reflective composition comprising a multifunctional crosslinker and a crosslinkable polymer
Implementation Method 3
decrosslinkable with acid diffusion, allowing for selective removal of exposed portions without damaging unexposed areas
Data Source
Figure 1(A)~1(B)
Figure 1(C)~1(D)
Figure 2(a)
AI summary
Acid-sensitive, developer-soluble bottom anti-reflective coating compositions are provided, along with methods of using such compositions and microelectronic structures formed thereof. The compositions preferably comprise a crosslinkable polymer dissolved or dispersed in a solvent system. The polymer preferably comprises recurring monomelic units having adamantyl groups. The compositions also preferably comprise a crosslinker, such as a vinyl ether crosslinking agent, dispersed or dissolved in the solvent system with the polymer. In some embodiments, the composition can also comprise a photoacid generator (PAG) and/or a quencher. The bottom anti- reflective coating compositions are thermally crosslinkable, but can be decrosslinked in the presence of an acid to be rendered developer soluble.