Query: Ion Diffusion in Chemically Amplified Resists

Candidate papers:

abstract: The acid catalyzed deprotection of glassy polymer resins is an important process in semiconductor lithography. Studies have shown that the reaction kinetics in these materials is controlled by slow.
author_names: Christopher M Bottoms

Tanguy Terlier

Gila E Stein

Manolis Doxastakis
title: Ion Diffusion in Chemically Amplified Resists
year: 2021

abstract: Catalyst diffusion is a critical component of the pattern formation process in chemically amplified resists (CARs) In this study, we used a concerted experimental and modeling effort to examine diffusion of an inert catalyst analogue (sodium triflate) in a hydroxystyrene based ESCAP terpolymer resin. First, atomistic simulations at high temperatures reveal an order of magnitude enhancement of the Fickian diffusivity in the protected reactant versus the fully deprotected product, while time of flight secondary ion mass spectrometry (TOF SIMS) measurements at temperatures near the glass transition show no appreciable differences. The data from simulations and experiments conform to a unified curve, enabling estimates of the Fickian diffusivity at relevant post exposure bake (PEB) temperatures through extrapolation. Second, acid catalyzed reaction kinetics were measured with Fourier transform infrared spectroscopy and compared with reaction diffusion models based on the estimated Fickian diffusivities. The initial kinetics in experiments is orders of magnitude faster than predictions, demonstrating that models of catalyst transport should capture effects beyond Fickian diffusion. Finally, the simulations examined ion ion and polymer ion interactions at the atomistic level, features that are difficult to probe by experimental investigations. These data show that ion pair clustering in the protected and deprotected materials is similar as temperature is reduced, and ion pair dynamics in both materials is dominated by interactions with hydroxystyrene repeat units. These trends explain the experimental observations that ion diffusion is similar in the protected and deprotected polymers.
author_names: Christopher M Bottoms

Tanguy Terlier

Gila E Stein

Manolis Doxastakis
title: Probing ion diffusion in chemically amplified resists through experiments and atomistic simulations
venue: Advanced Lithography
year: 2021

abstract: Acid diffusion plays an important role in chemically amplified resists. Acids are generated from acid generators upon deep ultraviolet light (DUV) irradiation. Physically, what the DUV illumination creates is an electrolyte solution in a nonequilibrium state. In addition to the force due to the concentration gradient, a charged particle undergoing diffusion motion experiences a dielectric friction force from the medium and the Coulomb force created by the surrounding charged particles. The Coulomb force between charged particles can be very important in a medium with a low dielectric constant. In such a case, the diffusivity of the counter ion can have a great impact on the "effective diffusivity" of the acid. The diffusion of acid and its counter ion are correlated strongly. Besides the Coulomb interaction, the acid base chemical equilibrium also affects acid diffusion. In this article, a simple model of acid diffusion including the effects of acid base equilibrium and Coulomb interaction is proposed. The theory proposed here shows that the "effective" acid diffusivity is mainly determined by the diffusivity of its counter ion, which can account for the acid generator size effect on acid diffusion observed in experiments.Acid diffusion plays an important role in chemically amplified resists. Acids are generated from acid generators upon deep ultraviolet light (DUV) irradiation. Physically, what the DUV illumination creates is an electrolyte solution in a nonequilibrium state. In addition to the force due to the concentration gradient, a charged particle undergoing diffusion motion experiences a dielectric friction force from the medium and the Coulomb force created by the surrounding charged particles. The Coulomb force between charged particles can be very important in a medium with a low dielectric constant. In such a case, the diffusivity of the counter ion can have a great impact on the "effective diffusivity" of the acid. The diffusion of acid and its counter ion are correlated strongly. Besides the Coulomb interaction, the acid base chemical equilibrium also affects acid diffusion. In this article, a simple model of acid diffusion including the effects of acid base equilibrium and Coulomb interaction is proposed. Th.
author_names: Xuelong Shi
title: Effect of Coulomb interaction and pKa on acid diffusion in chemically amplified resists
year: 1999

abstract: In chemically amplified resists, acids are generated upon DUV illumination. What DUV illumination really creates is an electrolyte solution with non uniform acid distribution. Since H+ carries a charge, its diffusion behavior is quite different from that of a neutral particle. The long range Coulomb interaction between charged particles can be very important in a medium with low dielectric constant such as resist. The diffusion of acid and its counter ion are strongly correlated, leading to a decrease of the effective diffussivity of acid. Detailed theoretical analysis shows that the diffusion coefficient that determines the critical dimensional change caused by acid diffusion is the effective acid diffusion coefficient Da equals 2Dx, which is determined by the diffusivity of the counter ion. The diffusion coefficient that is related to chemical amplification is the acid intrinsic diffusion coefficient DH+ The charge carried by H+ also makes its evaporation difficult due to large energy barrier created by electric potential difference between two phases and the 'image force' when H+ crosses over the resist/air rate depends on the acid diffusivity, acid strength and acid equilibrium vapor pressure at the post exposure bake temperature from the kinetic theory.
author_names: Xuelong Santa Clara Shi
title: Role of acid charge in chemically amplified resists
venue: Advanced Lithography
year: 1999

abstract: The photoacid bulkiness effect on dissolution characteristics was investigated in a three component chemically amplified deep ultraviolet positive resist system. The resist consisted of a tert butoxycarbonyl (t BOC) protected polystyrene, benzenesulfonic acid derivative photoacid generator and an additional dissolution inhibitor (t BOC protected bisphenol A) For the benzenesulfonic acid photoacid generator, four types of substituents; 4 fluoro, 4 chloro, 2,4 dimethyl, and 4 tert butyl, were studied. Dissolution contrast (Rmax/Rmin) increased and the pattern profiles became rectangular with increasing substituent bulkiness. The reason for this is that bulky substituents such as 2,4 dimethyl and 4 tert butyl increased resist hydrophobic strength in both bulk and surface regions, thereby strengthening the surface inhibition effect. Next, in order to investigate the bulkiness effect on acid mobility, diffusion length during postexposure bake time was determined by means of the ion conductivity method. Diffus.
author_names: Toshiro Itani

Hiroshi Yoshino

Masashi Fujimoto

Kunihiko Kasama
title: Photoacid bulkiness effect on dissolution kinetics in chemically amplified deep ultraviolet resists
year: 1995

abstract: We conducted line edge roughness (LER) measurements on resists with various sensitivities, exposed with a 75 keV 1:1 masked ion beam lithography tool. The critical dimension measurement data were treated with an algorithm for separation of mask induced roughness from random LER. The scaling analysis approach provided the correlation length and the roughness exponent. The results indicate that for exposure doses <2.5 uC/cm2 LER is not governed by shot noise but by the resist material properties (sensitivity, molecular weight, acid diffusion length) and development conditions.
author_names: Stefan Eder-Kapl

Hans Loeschner

M Zeininger

Wolfgang Fallmann

Oliver Kirch

George P Patsis

Vassilios Constantoudis

Evangelos Gogolides
title: Line edge roughness investigation on chemically amplified resist materials with masked Helium ion beam lithography
year: 2004

abstract: A series of single component chemically amplified molecular resists were made using an onium salt cation core of tris(4 (tert butoxycarbonyloxy) 3,5 dimethylphenyl)sulfonium (TAS) with five different acid anions: chloride (Cl) hexafluoroantimonate (SbF"6) triflate (Tf) nonaflate (Nf) and tosylate (Ts) The counter ion had a large effect on both the performance and physical characteristics of the resists. TAS SbF"6 and TAS Tf imaged as positive tone resists with good LER, but suffered from acid diffusion problems which limited resolution. TAS Ts and TAS Cl had high water solubility that prevented their use as positive tone resists. TAS Nf had poor wetting and adhesion that prevented it from being spin coated into films. Using onium salts as single molecule resists places great restriction on the choice of anion used because of the large effect it has on the properties of the resist. Using extreme ultraviolet lithography, TAS SbF"6, the best performing derivative, was able to resolve 50nm 1:1 line/space patterns with LER [email protected] of 5.2nm.
author_names: Richard A Lawson

Cheng-Tsung Lee

Laren M Tolbert

Clifford L Henderson
title: Effect of acid anion on the behavior of single component molecular resists incorporating ionic photoacid generators
year: 2009

abstract: Abstract Formulating high sensitivity and resolution in Extreme Ultraviolet (EUV) resists is a serious concern regarding the adaptation of EUV lithography. The incorporation of a high optical density Sn compound in MAPDST co ADSM (4 (methacryloyloxy)phenyl) dimethylsulfoniumtrifluoromethane sulfonate co acetyldibutylstannyl methacrylate, a non CAR photoresist, exhibits lithography resolution for sub 15 nm node when patterned under e beam and Helium ion irradiation. The synthesized resists were irradiated at 103.5 eV ~92 eV) using monochromatic synchrotron radiation. After EUV irradiation and oxidation, the resists were investigated using XPS, NEXAFS and by theoretical calculations (FEFF9 modeling program) It was observed significant changes in the labile CF3SO3 moiety, but interestingly its total dissociation or desorption was not observed after long exposure times. Bonds rearrangements of formation of SnO2 and new S C/C F functionalities after irradiation were detected. Those complex processes suggested the existence of important sinks for the high photon energy absorbed, which in turn increased the lithography resolution. The present results highlight the importance of the incorporation of a heavy metal covalently linked to the main polymer structure. The enhanced resolution observed in the MAPDST co ADSM resist formulation using standard processing conditions, establishes its potential candidature as a EUVL resist for rapid prototyping of semiconductor devices.
author_names: Guilherme Kretzmann Belmonte

Suelen Weimer Cendron

Pulikanti Guruprasad Reddy

Cleverson Alves da Silva Moura

Mohamad Ghulam Moinuddin

Jerome Peter

Satinder K Sharma

Gabriela Albara Lando

Marcelo Puiatti

Kenneth E Gonsalves

Daniel Eduardo Weibel
title: Mechanistic insights of Sn based non chemically amplified resists under EUV irradiation
year: 2020

abstract: Helium (He) ion lithography is being considered as one of the most promising and emerging technology for the manufacturing of next generation integrated circuits (ICs) at nanolevel. However, He ion active resists are rarely reported. In this context, we are introducing a new non chemically amplified hybrid resist (n CAR) MAPDSA MAPDST, for high resolution He ion beam lithography (HBL) applications. In the resist architecture, 2.15 antimony is incorporated as heavy metal in the form of antimonate. This newly developed resists has successfully used for patterning 20 nm negative tone features at a dose of 60 mC/cm2. The resist offered very low line edge roughness (1.27+ 0.31 nm) for 20 nm line features. To our knowledge, this is the first He ion active hybrid resist for nanopatterning. The contrast (g) and sensitivity (E0) of this resist were calculated from the contrast curve as 0.73 and 7.2 mC/cm2, respectively.
author_names: Pulikanti Guruprasad Reddy

Neha Thakur

Chien-Lin Lee

Sheng-Wei Chien

Chullikkattil P Pradeep

Subrata Kumar Ghosh

Kuen-Yu Tsai

Kenneth E Gonsalves
title: Heavy metal incorporated helium ion active hybrid non chemically amplified resists: Nano patterning with low line edge roughness
year: 2017

abstract: Chemically amplified resists with an acid generator, the anion of which is bound to the polymer through a covalent bond (anion bound resists) are promising materials for the 16 nm node and beyond. However, their reaction mechanism is unknown. In this study, we propose a proton diffusion model for anion bound resists. To examine the proton diffusion model, we carried out resist patterning experiments and a simulation. The calculated latent images corresponded well to the measured line width and estimated chemical gradient. This result suggests that protons diffuse under the electric field produced by anions and induce acid catalytic reactions in anion bound resists.
author_names: Takahiro Kozawa

Julius Joseph Santillan

Toshiro Itani
title: Modeling and Simulation of Acid Diffusion in Chemically Amplified Resists with Polymer Bound Acid Generator
year: 2012