Changes in the photoresist inhibitor distribution after ion irradiation and thermal treatment (original) (raw)
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Thermal stability of He irradiated photoresist films
Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions With Materials and Atoms, 1999
In this contribution we investigate the thermal stability of irradiated AZ-1350J novolac-diazoquinone photoresist ®lms, as a function of the¯uence for 380 keV He ions in the range from 10 13 to 10 15 He cm À2 . The techniques of RBS, NRA, ERDA, FTIR and solubility tests are used to study in detail the composition and chemical structure of the ®lms before and after the irradiations, and after isothermal heat treatments at 350°C during 6 h. Our results show that 10 15 He cm À2 at 380 keV, transferring an average electronic energy density of 2.0 eV/ # A 3 to the whole volume of the photoresist, is sucient to produce an eective crosslinking, without a signi®cant damage to the polymer, and promoting a substantial improvement in the thermal stability of the photoresist at 350°C. For lower¯uences the ®lms are not stable at this temperature. Ó
Diffusion and Distribution Studies of Photoacid Generators. Ion Beam Analysis in Lithograpy
Journal of Photopolymer Science and Technology, 1999
As the resolution of photoresists is being pushed to its limits, it becomes critical to understand the fundamental mechanisms and interactions among the various components in a photoresist. Chemically amplified photoresist systems have added components such as photoacid generators and dissolution inhibitors. Understanding their diffusion characteristics and distribution within the resist thin film becomes important in the design of effective photoresist formulations capable of better imaging performance. We have used Rutherford Backscattering Spectrometry (RBS) as a tool for investigating the diffusion and distribution characteristics of selected photoacid generators and additives in photoresists.
Degradation of 248 nm Deep UV Photoresist by Ion Implantation
Journal of The Electrochemical Society, 2011
Wet processes are gaining a renewed interest for removal of high dose ion implanted photoresist (II-PR) in front-end-of-line semiconductor manufacturing because of their excellent selectivity towards the wafer substrate and gate materials. The selection of wet chemistries is supported by an insight into the resist degradation by ion implantation. In this work, different analytical techniques have been applied for in-depth characterization of the chemical changes in 248 nm DUV PR after arsenic implantation. A radical mechanism of resist degradation is proposed involving cross-linking and chain scission reactions. The cross-linking of the resist is dominant especially for high doses and energies. It leads to significant depletion of hydrogen and formation of carbon macroradicals that recombine to form C-C cross-linked crust. Moreover, formation of ab-unsaturated ketonic and/or quinonoid structures by cross-linking reactions is suggested. In addition, the dopant species may provide rigid points in the PR matrix by chemical bonding with the resist. For higher doses and energies further dehydrogenation occurs, which leads to formation of triple bonds in the crust. Different p-conjugated structures are formed in the crust by cross-linking and dehydrogenation reactions. No presence of amorphous carbon in the crust is revealed.
Effect of microstructure on deprotection kinetics in photoresist
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2008
This article describes the result of predictions based on a novel continuum model for the effect of microstructure on deprotection reaction kinetics during postexposure bake ͑PEB͒. The effect of neighboring blocking groups is incorporated in a continuum PEB model. Provided blocking groups with neighbors react at a slower rate than isolated blocking groups, an up to 8% improvement in latent image contrast is predicted. In addition, a first principles calculation of the equilibrium structure for poly͑methyl methacrylate-cot -butyl methyl methacrylate͒ copolymer with acid present is reported. Hybrid quantum mechanics/molecular mechanics ͑QC/MM͒ results indicate that a strong hydrogen bond forms between blocked and unblocked neighbor sites in the presence of acid. The QC/MM prediction provides evidence confirming the rate constant for deprotection reaction with a neighboring blocked site is reduced relative to isolated blocking groups. The new PEB model form is shown to improve the fit to kinetic Fourier transform infrared data over conventional deprotection kinetics for those resists that contain carboxyl group deprotection chemistry. The new model also explains the difference in reaction rate between resists with otherwise identical deprotection chemistry by altering only neighboring blocked site content. Finally, a 50% greater lithographic advantage in development rate contrast is demonstrated for microstructure with increased neighboring blocked sites.
Advances in Resist Technology and Processing XXI, 2004
The performance of chemically amplified photoresists, including next generation thin film 157 nm fluorinated copolymers and blends, is affected by such phenomena as polymer/substrate and polymer/air interfacial (surface energy) effects, blend miscibility, small molecule diffusion in thin films, permeability of airborne contaminants, and interactions with products from the deprotection reaction. Using near edge x-ray absorption fine structure (NEXAFS) spectroscopy, it is possible to simultaneously probe the surface and bulk chemistry of chemically amplified photoresists to determine possible causes of pattern degradation, including post exposure delay induced material failure, blend component and small molecule diffusion/segregation to the photoresist surface, and interactions between components of the photoresist formulation and developer. The surface and bulk chemistry of model photoresists were analyzed in the NEXAFS vacuum chamber, equipped with in situ processing capabilities for exposure, controlled dosing of a model contaminant gas (NMP or water vapor), and heating, to quantify component segregation and identify surface phenomena that may be responsible for pattern degradation. For model 157 nm blend films, it was found that there is segregation of one component to the surface of the photoresist film, in excess of the composition of that component in the blend. For polymer blends the more hydrophobic or lower surface tension species will typically wet the film surface when heated in air. Segregation of photo-acid generator has also been demonstrated and the effect of reducing film thickness investigated. As photoresist film thickness continually decreases and the photoresists become increasingly sensitive to environmental contaminants, the interfacial and surface regions dominate the behavior of the material and it is crucial to understand both their physical and chemical nature.
Advancements in photoinitiators—Opening up new applications for radiation curing
Progress in Organic Coatings, 2007
The development of new photoinitiators which provide additional value to the curing efficiency is reported. These include compounds with low migration and volatility properties avoiding the leaking of chemicals into the environment, initiators that provide a high photosensitivity to black formulations and novel photolatent bases which allow the curing of formulation hitherto not available for radiation curing. These novel photoinitiators expand the use of radiation curing technology into new applications.
Evaluation of chemical kinetics in positive photoresists using laser desorption ionization
European Polymer Journal, 2014
Positive photoresists are photosensitive materials widely used in lithographic processes in microelectronics and optics for component relief manufacturing. When exposed to ultraviolet radiation, chemical reactions are induced that modify their physical-chemical properties. This work describes a novel technique to determine the kinetic rates of molecular structure changes of the positive AZ series photoresists after exposure to mercury arc lamp radiation. These positive photoresists consist of a photoactive compound (PAC), known as diazonaphthoquinone (DNQ), and a matrix material, which is a thick base resin. This positive AZ series photoresist was chosen because its technical information is well known while presenting potential for many applications. In the present work, we investigate these processes using laser desorption ionization (LDI) by a pulsed ultraviolet laser coupled to a high resolution time-of-flight mass spectrometer (ToF-MS). The LDI-ToF mass spectra present different relative intensities for some of the characteristic negative molecular ions of the positive photoresist after different exposure energies to the mercury arc lamp radiation. For measurement of the chemical kinetic mechanism, LDI-ToF mass spectrometry was used for the first time to obtain the fractional decay rate of the DNQ per unit of exposure radiation intensity. These results provide a novel use of LDI-ToF-MS to study the chemical kinetics of photosensitive materials.
2010
A soft-contact film transfer method was developed to prepare multilayer photoresist thin films that enable high-resolution spectroscopic and reflectivity measurements for determining the reaction-diffusion kinetic parameters and photoacid diffusion length. Infrared reflectance absorption spectroscopy was applied to follow, quantitatively, the reaction-diffusion kinetics during the post-exposure bake (PEB) step; the time evolution of the average deprotection level across a bilayer film with model photoresists is described by a kinetics model with three parameters: a reaction rate constant (k P), the phenomenological photoacid trapping constant (k T), and the photoacid diffusion constant (D H). A polymeric and molecular resist for next-generation extreme ultraviolet (EUV) lithography with chemically analogous structure was studied with this methodology. The three kinetic parameters follow an Arrhenius dependence but show quantitative differences between these two photoresists at a given PEB temperature. Further it was demonstrated that the photoacid diffusion length is not a simple function of diffusion coefficient; instead, it is dictated by all three kinetics parameters jointly in addition to the deprotection level at which the resist becomes soluble in an aqueous developer solution. These observations qualitatively explain the experimentally observed shorter photoacid diffusion length of the molecular resist in comparison to its polymeric counterpart.
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2007
The effects of amine base quencher on the photoacid catalyzed deprotection reaction-diffusion front in model photoresists were measured by combination of neutron reflectivity and Fourier transform infrared spectroscopy. Modulation in the location of the base with respect to the diffusing photoacid catalyst changes the spatial reaction extent and illuminates the complex role of the base on the shape of the reaction-diffusion front. Despite similar total extents of reaction, a comparison between uniform base and model photodegradable base distributions demonstrates distinct reaction time and base concentration effects on the deprotection profile shape. These differences arise from the modification of the initial deprotection extent due to both the neutralization of the photoacid and the influence of the changing photoresist composition on the reaction-diffusion process. The use of the model photodegradable base results in a sharper front due to these effects. Lastly, aqueous hydroxide development of these latent images demonstrates a limit to the improvement in feature quality obtained from sharpening of the deprotection profile with base additives.