Resist Composition Acid Diffusion Control
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Solution Overview
Problem
Current chemically amplified resist compositions face challenges in achieving high resolution and sensitivity while minimizing line edge roughness (LER) and preventing electrostatic charging during electron beam (EB) image writing, especially as feature sizes approach 45 nm and below, where acid diffusion and sensitivity issues become pronounced.
Innovation Solution
A resist composition comprising a polymer with acid labile group-substituted recurring units and a metal salt or complex of a mono- to tetra-functional C1-C20 carboxylic acid or β-diketone, selected from sodium, magnesium, chromium, manganese, iron, cobalt, nickel, copper, zinc, silver, cadmium, indium, tin, antimony, cesium, zirconium, and hafnium, which enhances acid diffusion control, sensitivity, and electro-conductive properties to prevent charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the accelerating voltage of the electron beam is increased to improve resolution and reduce forward scattering, then the contrast of electron image writing energy is improved, but the sensitivity of the resist film decreases as electrons pass straightforward through the film
Solution Approach 1:
The patent employs a composite resist system combining polyhydroxystyrene base resin with metal carboxylate salts (such as zinc, cadmium, or barium carboxylates) and chemically amplified resist components. This composite structure enables the resist to simultaneously achieve high resolution through controlled electron scattering and maintained sensitivity via chemical amplification mechanisms, resolving the contradiction between resolution improvement and sensitivity loss at high accelerating voltages.
Solution Approach 2:
The patent modifies the chemical composition parameters of the resist film by incorporating specific metal carboxylate salts and acid generators in optimized concentrations. These parameter changes enhance the resist's interaction with high-energy electron beams, improving both the contrast response and sensitivity without requiring a reduction in accelerating voltage, thus resolving the resolution-sensitivity trade-off.
2Length of moving object
If the thickness of the resist film is reduced below 100 nm to enable processing at 45 nm node and below, then the adhesion strength to substrate and structural strength are maintained, but the line edge roughness (LER) is substantially exacerbated
Solution Approach 1:
The patent uses a composite resist formulation combining polyhydroxystyrene with metal carboxylate salts and chemically amplified resist components. This composite structure provides enhanced film uniformity and controlled chemical amplification that suppresses LER even in thin films below 100 nm thickness, enabling sub-45 nm processing while maintaining manufacturing precision.
Solution Approach 2:
The patent introduces metal carboxylate salts that create localized chemical environments within the resist film structure. These localized modifications improve the uniformity of the resist response during exposure and development, reducing variations at the pattern edges and thereby minimizing line edge roughness in thin film structures.
3Productivity
If chemically amplified resist compositions are used to improve sensitivity and contrast, then the resolution is enhanced, but acid diffusion occurs which degrades line edge roughness
Solution Approach 1:
The patent introduces metal carboxylate salts (zinc, cadmium, or barium carboxylates) as intermediary components that modulate acid diffusion in the chemically amplified resist system. These metal salts act as diffusion barriers or sinks, controlling the spread of generated acids while preserving the sensitivity and contrast benefits of chemical amplification, thereby reducing line edge roughness.
Solution Approach 2:
The patent optimizes the concentration and type of metal carboxylate salts in the resist composition to control acid diffusion length scales. By adjusting these compositional parameters, the system maintains high sensitivity from chemical amplification while limiting acid spread that would otherwise degrade line edge roughness, achieving both improved productivity and manufacturing precision.
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 resist composition achieves high resolution, high sensitivity, and minimal LER, effectively addressing the challenges of acid diffusion and electrostatic charging, making it suitable for micropatterning in VLSIs and photomasks, particularly in EB and EUV lithography.
Implementation Method 1
acid diffusion control
Implementation Method 2
electro-conductive properties to prevent charging
Implementation Method 3
chemically amplified positive resist composition
Data Source
AI summary
A resist composition is provided comprising a (co)polymer comprising recurring units of acid labile group-substituted (meth)acrylic acid, styrenecarboxylic acid or vinylnaphthalenecarboxylic acid and/or recurring units having an acid labile group-substituted phenolic hydroxyl group, an acid generator, and a metal salt of carboxylic acid or a metal complex of β-diketone. Due to a high contrast of alkaline dissolution rate before and after exposure, high resolution, high sensitivity, and controlled acid diffusion rate, the composition forms a pattern with satisfactory profile and minimal LER.