Acceptor-Substituted EUV PAGs for Higher Acid Formation Efficiency
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Solution Overview
Problem
Existing chemically amplified resists for EUV lithography face inefficiencies in acid formation due to electron/hole recombination during exposure, leading to reduced sensitivity and increased stochastic effects on line width roughness.
Innovation Solution
Development of acceptor-substituted iodonium salts with higher electron affinity as photoacid generators (PAGs) to enhance electron capture efficiency, thereby increasing acid formation per EUV photon and improving photospeed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional PAGs are used in EUV lithography, then the resist can be exposed, but electron/hole recombination reduces acid formation efficiency and sensitivity
Solution Approach 1:
The patent modifies the electronic structure parameters of the PAG by introducing acceptor substituents (nitro, cyano, or alkylsulfonyl groups) at specific positions on the phenyl rings of the iodonium salt. This changes the electron affinity and HOMO/LUMO energy levels, optimizing the PAG's ability to capture electrons and form photoacids under EUV exposure, thereby reducing electron/hole recombination losses and improving acid formation efficiency.
2Productivity
If acceptor-substituted iodonium salts with higher electron affinity are used, then electron capture efficiency and acid formation increase, but the molecular structure becomes more complex
Solution Approach 1:
The patent applies local quality by introducing acceptor substituents at specific localized positions (2-, 3-, or 4-positions) on the phenyl rings of the iodonium salt rather than modifying the entire molecule uniformly. This targeted substitution at critical locations optimizes electron capture efficiency and photospeed while minimizing overall molecular complexity and maintaining synthetic feasibility.
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 use of acceptor-substituted iodonium salts increases photoresist sensitivity, reduces stochastic effects, and enhances throughput by increasing the number of catalytic acids formed, leading to higher resolution and reduced line width roughness.
Implementation Method 1
the direct absorption of a photon by the PAG is no longer the primary mechanism of photoacid generation. During the exposure, the EUV photon absorption generates a steady state of electrons and holes, with the electrons losing energy in successive collisions until they have reached energies near the thermal equilibrium, or they have recombined with a hole. The PAG comes into play again at the lower energies in the electron cascade when its cation can capture an electron, leading to the formation of a free radical.
Implementation Method 2
At this wavelength, the absorption of the photon leads to a primary ionization event in which an electron is ejected from an atom at high energy. This electron then collides with other atoms, leading to further ionization events which generate secondary electrons.
Implementation Method 3
The photoacid then catalyzes a chemical reaction which leads to the solubility change of the photoresist, for example, making the exposed areas more soluble in a developer for the case of a positive-tone photoresist.
Data Source
AI summary
Compounds of structure (I) are described wherein, R1, R2, R1a and R2a are independently selected from H, nitro, cyano, and an alkylsulfonyl, wherein at least two of R1, R2, R1a and R2a are independently selected from nitro, cyano, and an alkylsulfonyl, and X− is not a halide, tosylate, trifluoromethylsulfonate, tetrafluoroborate, an aryl-substituted borates, hexafluorophosphate, hexafluoroarsenate, acetate, trifluoroacetate, methane sulfonate, C-2 to C-20 linear unsubstituted alkyl sulfonates, naphthalenesulfonate, and camphorsulfonate. Also described are EUV negative and positive chemically amplified photoresist compostions containing said compound and the process of using these photoresist to pattern a substrate.