Properties Of Photoresist Research Articles

Preparation and characterization of SU8–carbon nanotube composites

AbstractSU8–carbon nanotube composites have been produced to enhance the mechanical, electrical, and thermal properties of SU8 photoresists. Homogeneous composites materials have been obtained when multiwalled carbon nanotubes (MWCNTs) functionalized with COOH groups were used. Indeed, COOH groups can react with the epoxy ring of the SU8 molecule yielding an improved interaction between carbon nanotubes (CNTs) and the polymer matrix. Impedance spectroscopy was used to study the conducting percolation path in the composites, that is the quality of the nanotube dispersion in the epoxy matrix. It turns out that propylene glycol methyl ether acetate (PGMEA) as well as gamma‐butyrolacton (GBL) are very suitable solvent to prepare SU8‐MWCNTs composites of good homogeneity.

Dynamic thermal mechanical characterization of Epoclad negative photoresist for micro mechanical structures

Dynamic thermal mechanical properties of Epoclad negative photoresist have been studied. These experiments are part of the mechanical characterization of several photo definable polymers which can be used as a permanent, active and, or structural layer in a MEMS. This paper reports on the visco-elastic properties such as the loss modulus, the storage modulus and the glass transition temperature.

Contributions to the photochemistry of poly(4-vinylpyridine) and its ionic derivatives in the presence of water

Films of poly(4-vinylpyridine), poly(N-carboxyethyl-4-vinylpyridine) and poly(N-allyl-4-vinylpyridine) chloride were exposed at a radiation spreading between about 250 and 270 nm, and the photochemical processes were monitored by spectroscopic methods. Reaction mechanisms considering: (i) a double role of the water molecule, to form water–pyridine ring hydrogen bonds and to accept hydrogen atoms, (ii) the scission of C H methine bonds in units with photoexcited pyridine rings, (iii) the scission of N + C bonds in betaine units, and (iv) crosslinks appearing by recombination of carbon macroradicals or by the addition of methine groups to allyl groups, were found to explain the photocrosslinking of the three polymers. Their properties of crosslinking photoresists were observed by AFM and the best ones were found for the polymer with N-allyl-pyridinium chloride units.

Non-linear dissolution of amorphous arsenic sulfide-selenide photoresist films

The properties of non-linear inorganic chalcogenide photoresists fabricated by co-evaporation of Ag with amorphous arsenic sulfide-selenide materials are considered in detail. The influence of several factors, including Ag concentration, irradiation wavelength and composition of the developer on the photoresists characteristics was studied. Superlinear dissolution characteristics of the photoresists are explained in the frame of the so-called “percolation approach”. The advantages of superlinear photoresists, especially for the case of maskless photolithography, are briefly discussed.

Chalcogenide glassy photoresists: History of development, properties, and applications

The history of the development of photoresists based on the photostructural transformations in chalcogenide glassy semiconductors is discussed in this paper. The properties of such photoresists including the possibility of an essential increase of their photosensitivity and also applications are examined. Together with the photoresists, the chalcogenide glassy roentgen-, electron beam-, and plasma-resists are briefly considered.

Plasma-assisted supercritical carbon dioxide removal process for photoresist stripping applications

Because of increasing interest in environmentally benign fabrication process, the use of dry cleaning processes to remove residues of metal, photoresists, organic moieties and particles from surfaces has grown as a research area. In this study, we designed series of systematic approaches to understand the properties of the hard-baked photoresist on glass substrates. We focused on the effects of de-bonding photoresists on the surface by using a plasma-assisted supercritical carbon dioxide removal process with various control parameters. Changes in the surface morphology of plasma de-bonded photoresists were observed and analyzed. A weight-loss method was used to evaluate quantitatively the efficiency of photoresist stripping by SCCO 2. Compared to the blank experiment (SCCO 2 process only), the photoresist residue reduces to 14.7% from 76.3%. This study demonstrates the possibility of incorporating plasma pretreatment into the supercritical carbon dioxide removal process for photoresist stripping applications.

Effects of Sputtering Metal Deposition Parameters in the Photoresist used as a Sacrificial Layer in Micro-electromechanical System Devices

ABSTRACTThe present letter describes a reliability study of the micro-electromechanical system fabrication with a photoresist layer used as sacrificial layer with an aluminum beam deposited by means of RF sputtering method. This work reports changes of the roughness and planarity of the sacrificial layer beneath the aluminum film following the sputtering deposition. Such changes may be attributed to the alteration of the photoresist properties due principally to the outgassing of hydrogen by decomposition of C-H bonds under argon plasma. A safe deposition parameters area was identified where the photoresist layer keeps its properties and may be used as sacrificial layer.

Tuning of resist slope with hard-baking parameters and release methods of extra hard photoresist for RF MEMS switches

We have studied the properties of photoresist (resist) as a sacrificial material for fabricating suspended metal bridges and developed a process to release RF MEMS switches by dissolving thermal cross-linked extra hard photoresist. At the edges of the patterned photoresist, the contact angle with the substrate can be tuned using hard-baking parameters. From the experiment we have found that the resist angle reduces both with baking temperature and time. The baking temperature has a stronger effect on resist slope than the baking time has. It is also observed that at a certain baking temperature, and after a certain time, the resist angle does not reduce further. The RF MEMS switch with photoresist as the sacrificial layer can be released by plasma ashing to strip the initial resist skin, followed by dissolution of the bulk resist in Microposit 1165 solution with heating. The heating of the Microposit 1165 solution accelerates and improves the dissolving process. The Piranha solution is also very effective in dissolving hard resist for releasing RF MEMS switches.

Surface graft polymerization of SU-8 for bio-MEMS applications

There is currently increasing interest in using SU-8 photoresist to build microstructures for micro-electro-mechanical systems (MEMS). This report describes an effective bench-top method to modify the surface properties of SU-8 photoresist. This strategy relies on the residual epoxide groups present on the surface of SU-8 following fabrication. These epoxide groups are converted into hydroxyl groups by oxidation with a high concentration of cerium(IV) ammonium nitrate (CAN) and nitric acid. Subsequently the surface hydroxyl groups are used as initiation sites for graft polymerization catalyzed by CAN in the presence of acid. A number of water-soluble polymers including poly(acrylic acid), poly(acrylamide), poly(ethylene glycol) were successfully grafted onto SU-8. The presence of surface-linked polymers was confirmed by contact angle measurements, attenuated total reflection-Fourier transform infrared spectroscopy and toluidine blue adsorption. This method was particularly useful for tailoring the surface properties of complex or enclosed microstructures, for example, microfluidic channels. In addition the grafted polymers could serve as sites for high density protein immobilization or cell attachment on Bio-MEMS.

High‐Density Arrays of Germanium Nanowire Photoresistors

The photoresistive properties and dynamics of ordered high-density arrays of germanium nanowire photoresistors is presented. Individual nanowires demonstrate a sufficient photocurrent to be used in the detection of high illumination intensity. The figure illustrates the photoconductivity measurement assembly. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2089/2006/c0213_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

The Features of DVD-RAM Stamper Studies via Laser Energy Adjustment

To enhance the validity of signal and optical reflectivity on DVD-RAM, in this study we performed variable laser recording power experiments, and established the theoretical model for simulating the features that of the groove/land and header on a DVD-RAM stamper. This is the first work showing the features of the groove/land and header on a DVD-RAM stamper, that is, the geometry of a stamper, are mainly governed by laser recording power, recording speed, wavelength, photoresist film thickness, and photoresist properties. At a constant photoresist thickness, a difference in laser recording power is caused by the radius of the embossed area. The theoretically predicted results agree with the measurements of the features of the groove/land and header on a DVD-RAM stamper. At a fixed recording speed, recording power, when increased, can significantly increase the width of the groove/land and the length of the header.

Synthesis of alicyclic polymers and characterization of chemical amplified positive photoresists having the same

AbstractTo investigate the effects of cyclic structures of polymers on the physical properties of photoresist, a series of copolymers consisting of various comonomers selected from 3,6‐endo,oxo‐1,2,3,6‐tetrahydrophthalic anhydride (THPA), bornyl methacrylate (BMA), methacrylic acid (MA), t‐butyl methacrylate (t‐BMA), and 2‐norborene (NB) was synthesized. The molecular weight, glass transition temperature, and the components of the synthesized copolymers were estimated. Photoresists consisting of the synthesized polymers and photoacid generator were prepared. The dependence of the molecular structures on the developers was investigated. The exposure characteristic curves of the photoresists were studied. The existence of the alicyclic comonomers was clearly found to increase the plasma resistance of the photoresist. The sensitivity, contrast, and exposed real image of the prepared photoresists were all investigated. The results obtained suggest that the alicyclic polymers synthesized in this investigation could be used as positive tone photoresists. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1505–1514, 2005

Direct emissive pattern formation in PPV-type polymer with built-in photoresist properties and the application to light emitting devices

The principle of photobleaching in the conjugated polymer material didodecylstilbenevinylene (didodecyl-PSV) was used as a built-in photoresist property to control the extent of the emissive layer in polymer light emitting devices (PLEDs). Illumination of thin films of the conjugated polymer material on optically transparent conducting substrates through a positive mask with short exposure times (20–60 s) using a 150 W Xenon lamp and subsequent application of the and the second electrode enabled the formation of an electroluminescent image of the mask. We demonstrate a direct method where no photoresist, intermediate steps or mechanical manipulation is required to generate a complex emissive pattern employing a homogenous film and homogenous electrodes. The fluorescence of the film showed complex lifetime decays. We found that the lifetime increased with emission wavelength indicating the presence of energetically disordered excitons. The fine structure observed in the solution emission is absent in the film emission. However, after photobleaching the film emission becomes very similar to the solution emission. The appearance of fine structure could indicate that only one state became responsible for the photoluminescence spectrum. Infrared spectroscopy was used to confirm the presence of a degradation route similar to that reported for dialkoxypolyphenylenevinylene materials where the vinylene bonds are react with molecular oxygen and form carboxylic acid groups. Finally the effect of using different electrode metals was established and a comparison made between the photoluminescence and electroluminescence properties. The electroluminescence emission maximum (580 nm) of didodecyl-PSV light emitting devices was found to be redshifted by 20 nm compared to the photoluminescence, exhibited turn-on voltages below 3 V and reached a luminance of 100 cd m −2 at current densities below 10 mA cm −2.

A two-dimensional model of the deformation of photoresist structures using elastoplastic polymer properties

A model was developed for predicting the collapse behavior of photoresist structures due to the drying of rinse liquids during wet chemical processing. The magnitude of the capillary forces was estimated using the classical thermodynamics of surface tension, and the deformation of the structure was modeled using beam bending mechanics that accounts for both elastic and plastic modes of deformation. The two-dimensional model can predict the critical beam height of collapse as a function of the wetting behavior of the rinse liquid on the beam, the elastic and plastic mechanical properties of the polymeric photoresist, and the beam dimensions. Collapse behavior was predicted for polymer nanostructures with elastoplastic mechanical properties similar to those of bulk poly(methyl methacrylate). We have compared the collapse predictions from our model with the results of models that account only for elastic or plastic deformation behavior. Regimes in the elastic-plastic mechanical property space for which it is necessary to use the developed beam bending model have been highlighted. It is shown that in some cases the inclusion of both elastic and plastic mechanical properties is necessary for modeling the collapse behavior of polymer beams fabricated using the lithographic process.

Optical Properties of Acrylate-Based Negative-Type Photoresist and Its Application to Optical Waveguide Fabrication

In this article, we present some of the optical properties of a polymeric acrylate-based photoresist material called PNME, by its principal components, which are pentaerythritol triacrylate, n-methyldiethanolamine, and eosin. The refractive index and absorption spectra were measured. Because of the low absorption of PNME in the datacom and telecom regions, PNME was studied with respect to its suitability for the fabrication of a channel waveguide and/or an optical fiber. A multimode optical waveguide was fabricated using a cold UV stamping fabrication method, and propagation losses at 1.3 µm were measured. An optical fiber core was fabricated using a light-induced self-writing fabrication method. In our study, it was found that optical waveguides made from PNME have low propagation losses due to smooth sidewalls and the low absorption of PNME. An optical waveguide with a corrugated core was also fabricated.

Combinatorial methodologies offer potential for rapid research of photoresist materials and formulations

A combinatorial research methodology is outlined with the potential to investigate material factors in photoresist formulations more rapidly than with traditional experimental design. The approach involves generating a gradient of processing variables in the photoresist film and using a set of analysis tools to “map” the photoresist properties as a function of the gradient variables. While high-throughput strategies have proven useful for empirical optimization of photoresist processing conditions, they have not been fully exploited to probe the complex array of material issues in projection lithography. Of primary importance in combinatorial methodologies is the generation of variable gradients. The focus of this article is to illustrate techniques to generate a gradient in bake temperature and bake time in the polymer films, and to illustrate that these gradient techniques can be used to probe fundamental properties of lithographic materials, such as deprotection kinetics. These gradient techniques were applied to rapidly probe the deprotection behavior of a poly(tertbutyloxy-carbonyloxy-styrene). The deprotection data, obtained by applying the combinatorial gradients, agrees well with previous literature, validating the accuracy of these high throughput methods. The advantage of the combinatorial research strategies lies in the potential to investigate fundamental lithographic phenomena more rapidly than with traditional experimentation.

Preparation and characterization of copolymers containing (+)‐bornyl methacrylate and their racemate for positive‐tone photoresist

AbstractThis study investigated the chemical behavior of polymers bearing cycloaliphatic bornyl units along with the steric difference of the chiral (+)‐bornyl methacrylate [(+)‐BMA] and racemic (±)‐BMA, expressed in the physical properties of the copolymers and the resist characteristics. To do this, a series of copolymers containing (+)‐bornyl methacrylate [(+)‐BMA] and (±)‐BMA] units was synthesized. Comonomers of tert‐butyl methacrylate (TBMA), methyl methacrylate (MMA), and maleic anhydride (MA) were used. The thermogravimetric curves, glass‐transition temperature (Tg), and molecular weight (MW) of the copolymers were evaluated. Exposure characteristics of chemical‐amplified positive photoresists comprising various copolymers were investigated. It was found that copolymers bearing (±)‐BMA have higher Tg and better thermostability than those of copolymers containing (+)‐BMA units. The copolymers with (±)‐BMA units, however, revealed an inert photochemical behavior on the positive‐tone photoresist. The patterning properties of the positive photoresist, composed of copolymers bearing (+)‐BMA and (±)‐BMA, and the photoacid generator (PAG) were also investigated. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3538–3544, 2001

Photosensitivity and physicochemical properties of the two-layer photoresist based on naphthoquinone diazide and cyclorubber

The possibility was examined of preparing a model of a two-layer photoresist based on a photo-sensitive layer of naphthoquinone diazide (FP-383), a planarizing layer of cyclorubber (FN-11), enhancing the photosensitivity and physicochemical resistance of FN-11 films after irradiation through thenaphthoquinone diazide layer and its removal by development in KOH.

Structure and properties of ion-beam sputtered As xS 1 − x films

As x S 1 − x films with x from 0.33 to 0.57 were prepared by ion-beam sputtering of glassy and crystalline targets. All as-deposited films were amorphous even if the molecular crystals, As 4S 4 and As 4S 3, were sputtered. The film structure was investigated by IR spectroscopy. In comparison with thermally evaporated films, as-deposited ion-beam sputtered (IBS) ones do not contain any As 4S 4- and As 4S 3-like molecular fragments. As 4S 4 and As 4S 3 are formed in films containing As more than 40 at.% as a result of illumination or annealing. Photobleaching was obtained in all as-deposited films without any photocrystallization. Photoresistive properties of films were investigated. It was found that the best selectivity of etching in amine solutions is obtained for As 4S 3 amorphous films.

Photoprocessable copolyimides with carbazole groups

This paper describes copolymers from maleimides and methylvinyl isocyanate, which combine the properties of photoresists with those of semiconducting polymers. The maleimide unit is functionalized with t-BOC groups. The isocyanate group can - in principle - be reacted with various hole or electron transporting units as shown - in a first example - for carbazoles. A photopatterning of these polymers is possible by adding a photoacid generator. The photochemically generated protons splitt off the t-BOC groups by chemical amplification. The difference in solubility thus achieved allows photopatterning.