E. Valamontes

Tailoring the surface topography and wetting properties of oxygen-plasma treated polydimethylsiloxane

In this work, we address the issue of controlled modification of the surface topography of polydimethylsiloxane (PDMS) when subjected to oxygen-based plasma treatments, and we investigate the resulting enhanced surface area as a means of controlling the surface wetting properties. We fabricate wavy structures of controllable nanoscale amplitude and periodicity in the range 50–300nm, spontaneously formed on PDMS surfaces, by means of appropriate plasma processing conditions and radiation pretreatment. Such structures are desirable for applications in sensor microdevices, the development of biocompatible materials, and micro- and nanosystems in general. Ordered structures fabricated on polydimethylsiloxane of relatively high amplitude and small periodicity are chosen as appropriate surfaces for the enhancement of the surface wetting properties, which can be tuned from highly hydrophilic to hydrophobic when combined with a hydrophobic coating applied on the rich surface nanotexture. This fact underlines the ...

Surface and line-edge roughness in solution and plasma developed negative tone resists: Experiment and simulation

A methodology is described for the experimental and theoretical study of surface roughness (SR) and line-edge roughness (LER) and their relation for solution and plasma developed resist schemes. Experimental results for a negative-tone nonchemically amplified siloxane bilayer resist scheme are shown. In addition, a molecular-type simulation of SR and LER is presented. The simulator can follow the appearance of SR and LER after each process step and predict the roughness dependence on material properties and process conditions. The simulation results are compared with SR experimental data for a negative-tone chemically amplified epoxy resist.

Etching behavior of Si-containing polymers as resist materials for bilayer lithography: The case of poly-dimethyl siloxane

This work is focused on the plasma development of siloxanes investigated as model Si-containing photoresist components that show a promise for bilayer lithography at 157 nm and other Next Generation Lithography technologies. In such lithography, the image is developed in the top photosensitive polymer and transferred to the (usually thick) organic underlayer by means of O2-based plasma etching. In this work particularly, the issue of line edge roughness (LER) induced by transfer etching and its reduction by means of plasma processing optimization is addressed. The experimental results reveal that low values of line-edge roughness are obtained in a high-density plasma reactor, if an F- but not O-containing etching first step is used in appropriate plasma conditions. The effect of different etching chemistries and processing conditions on imaging layer roughness formation is demonstrated with the aid of scanning electron microscopy images and image analysis for quantifying LER, and atomic force microscopy (...

Characterization and simulation of surface and line-edge roughness in photoresists

The problem of surface and line-edge roughness characterization and prediction is discussed. Different roughness parameters, such as the root mean square deviation (rms or σ), the fractal dimension, and the Fourier spectrum, are presented and compared. These roughness parameters for three negative tone resists (wet and plasma developed) are analyzed versus exposure dose, photoacid generator concentration, and plasma development conditions. Finally, a molecular type simulator is used to predict the experimental roughness behavior.

Surface modification of Si-containing polymers during etching for bilayer lithography

Abstract Surface modification of polydimethylsiloxane (PDMS) under O 2 plasma exposure is studied by XPS and real time ellipsometry. Results show the conversion of the PDMS surface into a SiO x -like material. Total layer thickness and extension of the SiO x layer are controlled by the sample bias. We suggest that surface and line edge roughness defects occurring when using PDMS as top layer in bilayer lithography are intimately related to the rapid kinetics of conversion and to the formation of SiO x hard micromasks on the surface.

Roughness characterization in positive and negative resists

Abstract Different roughness parameters, such as the root mean square deviation (rms or σ), the correlation length Lcor, the fractal dimension D and the Fourier spectrum, are presented and compared. The scaling behavior of σ determining the Lcor as well as the dependence of σ and D on the exposure dose for two negative tone (wet- and plasma-developed) and one positive tone resist are investigated. The experimental analysis reveals an interesting interrelation (inverse behavior) between σ and D which is not predicted by theory, and elucidates the dependence of Lcor on the exposure dose.

Electron beam lithography simulation for high resolution and high-density patterns

Abstract A fast simulator for electron beam lithography, called SELID TM , is applied for the simulation and prediction of the resist profile of high-resolution patterns in the case of homogeneous and multilayer substrates. For exposure simulation, an analytical solution based on the Boltzmann transport equation (where all important scattering phenomena have been taken into account) for a wide range of e-beam energies is used. The case of substrates consisting of more than one layer (multilayer) is considered in depth as it is of great importance in e-beam patterning. By combining the energy deposition data from simulation with analytical functions describing the resist development (for the conventional positive-resist PMMA), complete simulation of dense layouts in the sub-quarter-micron range has been carried out. Additionally, the simulation results are compared with experimental ones for dense patterns in the sub-quarter-micron region. By using SELID TM , forecast of resist profile with considerable accuracy for a wide range of resists, substrates and energies is possible, reducing in that way the cost of process development. Additionally, proximity effect parameters are extracted easily for use in any proximity correction package.

Surface roughness induced by plasma etching of Si-containing polymers *

Interfacial properties of polymers and their control become important at submicrometer scales, as polymers find widespread applications in industries ranging from micro- and nanoelectronics to optoelectronics and others fields. In this work, we address the issue of controlled modification of surface topography of Si-containing polymers when subjected to oxygen-based plasma treatments. Treated surfaces were examined by atomic force microscopy to obtain surface topography and roughness of plasma-treated surfaces. Our experimental results indicate that an appropriate optimization of plasma chemistry and processing conditions allows, on one hand, small values of surface roughness, a result crucial for the potential use of these polymers for sub-100 nm lithography, and, on the other hand, desirable topography, applicable for example in sensor devices. Plasma processing conditions can be modified to result either in smooth surfaces (rms roughness < 1 nm) or in periodic structures of controlled roughness size and periodicity.

Dissolution properties of ultrathin photoresist films with multiwavelength interferometry

According to the ITRS, a significant decrease in lateral resolution and thickness of resists is anticipated for the forthcoming decade. In order to study in-situ the dissolution of thin resist films, a set-up based on multiwavelength interferometry was developed. Using this setup and an appropriate fitting algorithm, based on the interference function, the resist thickness vs. time is calculated. In the present work, the dissolution of PMMA in a 20-300 nm thickness range is studied. First results showed that in the case of ultra thin films of high molecular weights, dissolution proceeds smoothly after an initial surface inhibition period while thicker films present a more complex dissolution curve. In the case of low molecular weight (15K) the surface inhibition period is negligible and dissolution proceeds smoothly for the whole thickness range examined. PMMA films exposed with various DUV doses exhibit similar behavior with the unexposed films in terms of dissolution inhibition.

Simulation of roughness in chemically amplified resists using percolation theory

A simulator for e-beam exposure and development (SELID) is combined with molecular modeling in order to investigate the various side effects of the gelation process in the case of chemically amplified resists (CARs). The procedure is demonstrated in the case of the negative tone epoxy resist but the method is equally applicable for other resist systems (positive and negative tone) and development mechanisms. A conventional resist simulator is not sufficient for the description of characteristics related to the detailed gel structure of the resist film and it needs to be combined with a molecular model. Molecular modeling is a suitable method for the simulation of the microscopic changes occurring during the post-exposure bake and development processes in the case of CARs. Macroscopic feature changes such as free volume size, cluster formation, and surface roughness can be effectively described using percolation theory. In order to construct a molecular model of a complex resist system a 3D square lattice ...