Properties Of Photoresist Research Articles

Recent Advances in Metal-Oxide-Based Photoresists for EUV Lithography.

Extreme ultraviolet lithography (EUVL) is a leading technology in semiconductor manufacturing, enabling the creation of high-resolution patterns essential for advanced microelectronics. This review highlights recent progress in inorganic metal-oxide-based photoresists, with a focus on their applications in EUVL. The unique properties of zinc-based, tin-oxygen, and IVB group inorganic photoresists are examined, showcasing their enhanced chemical reactivity and precise patterning capabilities. Key advancements include the development of zinc oxide and tin oxide nanoparticles, which demonstrate significant improvements in photon absorption and solubility under extreme ultraviolet exposure. Additionally, the review delves into the photochemical reactions of tin-oxygen clusters and the influence of various ligands on film density and cross-linking. The findings suggest that these inorganic photoresists not only improve photolithographic performance but also hold potential for broader applications, such as pyroelectric infrared sensors and 3D printing. Future research directions are outlined, including the optimization of process parameters, the exploration of new ligand and metal combinations, and the evaluation of the environmental benefits of inorganic photoresists over traditional organic ones. These advancements are poised to further enhance the resolution and patterning capabilities required for next-generation semiconductor devices.

Influences of two sizes of nano-Fe3O4 on stereolithography 3D printing properties of gel photoresist for photothermal-responsive hydrogel

Nanocomposite hydrogels enable augmented properties, functions, and responsive behaviors. In the field of stereolithography 3D printing of the photothermal responsive nanocomposite hydrogel, the influence of the size of nano-Fe3O4 on 3D printing properties is significant due to the sedimentation, but the relevant research is rare. In this study, for the fabrication of photothermal responsive hybrid hydrogel, poly(N-isopropylacrylamide-acrylamide)/nano-Fe3O4 [P(NIPAM-AM)/nano-Fe3O4] gel photoresist was prepared and digital light processing (DLP)-based 3D printing as one of the popular stereolithography 3D printing technology was utilized. The influences of two sizes of Fe3O4 nanoparticles (10 and 50 nm) denoted as nano-Fe3O4(10) and nano-Fe3O4(50) on DLP 3D printing properties of the gel photoresist were investigated in detail. The results reveal that the gel photoresist with nano-Fe3O4(10) obtained long exposure time for the basic prototype, low overcuring degree (Od), and good uniformity of nanoparticles in hybrid hydrogels, while those with nano-Fe3O4(50) had the merits of printing high 3D sample due to the low release fore. Unfortunately, the gel photoresist with a high content of nano-Fe3O4 such as 3.11 wt% failed in 3D printing of a high and uniform gel cylinder. A strategy of preparing P(NIPAM-AM)/nano-Fe3O4 gel photoresist with mixed nano-Fe3O4(10) and (50) for 3D printing was proposed. Using the gel photoresist (nano-Fe3O4 content: 3.11 wt%) with two sizes of nano-Fe3O4 mixed with 50% each and the exposure time of 8 s, a gel cylinder with a height of 1 cm was successfully printed with uniform nano-Fe3O4 distribution and low Od values (≤ 1.17%). Further, a biomimetic hydrogel octopus was 3D printed by using the gel photoresist with mixed nano-Fe3O4 and thereafter a near-infrared-light-driven waving motion of octopus tentacle was achieved successfully.

Refractive index measurement of IP-S and IP-Dip photoresists at THz frequencies and validation via 3D photonic metamaterials made by direct laser writing

Direct laser writing (DLW) is widely used to fabricate complex metamaterials (MMs) and photonic devices for nanoscale applications across the electromagnetic frequency spectrum. While the optical properties of conventional photoresists used in DLW are well studied in the visible and infrared range, it is still unclear how they behave at lower frequencies. Here, we measure the refractive index and absorption of IP-S and IP-Dip photoresists within the THz range of the electromagnetic spectrum. Further, we utilize THz time-domain spectroscopy (THz-TDS) to experimentally measure the laser-processed three-dimensional (3D) MM structures. We conduct full-wave electromagnetic simulations using the measured refractive index values to validate our experiments. The THz-TDS measurements are in excellent agreement with the theoretical predictions verifying the validity of our refractive index measurements. This study aims to support and lead future investigations utilizing standard DLW photoresists for photonic applications in the THz range.

Surface hardening of extreme ultraviolet(EUV) photoresist by CS2 plasma for highly selective and low damage patterning

Extreme ultraviolet (EUV) lithography has the advantage of implementing a finer pattern by using a wavelength of 13.5 nm light source with a higher resolution value than the existing ArF light source. However, there are several issues regarding EUV photoresist (PR), such as low etch resistance due to thin thickness and pattern mismatch during subsequent processing/deterioration of electrical characteristics of the device due to increase in line edge roughness (LER). In this study, the effect of CS2 plasma treatment and/or followed annealing at 80 °C on the EUV PR properties was investigated to improve PR characteristics such as LER, etch resistance, etc. during the etching by CF4 plasma. The CS2 plasma treatment and followed annealing improved the PR characteristics such as decreased ΔLER, decreased ΔCritical dimension, and decreased ΔThickness of the PR after the etching compared to the reference and/or annealed PR. Especially, the PR treated by CS2 plasma + annealing showed the improvement of etch resistance of ∼ 70 % compared to the reference PR. The X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy showed that the improvement of EUV PR properties were related to the formation of CS, OS bonds on the surface of PR by the CS2 plasma treatment + annealing.

Photocatalytic and Antibacterial Properties of Doped TiO2 Nanopowders Synthesized by Sol-Gel Method.

For environmental applications, nanosized TiO2-based materials are known as the most important photocatalyst and are intensively studied for their advantages such as their higher activity, lower price, and chemical and photoresist properties. Zn or Cu doped TiO2 nanoparticles with anatase crystalline structure were synthesized by sol−gel process. Titanium (IV) butoxide was used as a TiO2 precursor, with parental alcohol as a solvent, and a hydrolysing agent (ammonia-containing water) was added to obtain a solution with pH 10. The gels were characterized by TG/DTA analysis, SEM, and XPS. Based on TG/DTA results, the temperature of 500 °C was chosen for processing the powders in air. The structure of the samples thermally treated at 500 °C was analysed by XRD and the patterns show crystallization in a single phase of TiO2 (anatase). The surface of the samples and the oxidation states was investigated by XPS, confirming the presence of Ti, O, Zn and Cu. The antibacterial activity of the nanoparticle powder samples was verified using the gram−positive bacterium Staphylococcus aureus. The photocatalytic efficiency of the doped TiO2 nanopowders for degradation of methyl orange (MO) is here examined in order to evaluate the potential applications of these materials for environmental remediation.

STRENGTH PROPERTIES OF PHOTORESISTS FOR EXPLOSIVE LITHOGRAPHY

The adhesion and strength properties of NFR 016b4 photoresist (PR) films for explosive lithography deposited on the surface of KDB-10 single-crystal silicon wafers by centrifugation have been studied. It has been found that they behave like brittle materials. The FR microhardness measured at low loads was ~0,3 GPa, decreasing slightly with increasing film thickness. The crack resistance parameters (fracture toughness coefficient K1С and effective fracture energy γ) at low loads do not depend on the film thickness. With increasing load, the crack resistance of a thin film increased faster than that of a thick one. The specific peeling energy G under normal loading was ~1,2 J/m2 for thick and ~0,7 J/m2 for thin films. The higher values of G for thick films are most likely due to the compensation of elastic stress fields arising at the photoresist/silicon interface. The strength properties of NFR 016b4 explosive lithography photoresist and FP9120 positive diazoquinone-novolac photoresist are compared.

Enhancement of Mechanical and Thermal Properties of SU-8 Photoresist with Multilayer Woven Glass Fabric Based on Micromachining Technology

SU-8 photoresist has been more and more widely used as a structural material in micro electromechanical system (MEMS) because of its low cost and excellent biocompatibility. However, the inferior mechanical and thermal performances immensely impinge the reliability of the MEMS device based SU-8 and accordingly restrict its application. Here we report the mechanical and thermal performance of SU-8 reinforced by the multilayer glass fabric with the MEMS technology. The finite element simulation and specific experiment are conducted, which confirm that the reinforced SU-8 composites have a 281% increase in Young's modulus and a 64% decrease in coefficient of thermal expansion (CTE) compared with pure SU-8. Additionally, the improved mechanism has also been analyzed, including the excellent interface bonding between the SU-8 and glass fabric, and the high-bond energy of Si–O-Si chain structures in glass fabric. Furthermore, the glass fabric reinforced SU-8 could still possess a high light transmittance to maintain the ability of lithography patterning. Therefore, it is believed that the strategy proposed here may satisfy higher requirements of MEMS devices, which guarantees its practical applications in the functional microstructures.

Evaluation of Decomposition Property of Photoresist by Oxygen Radicals Using Helium-Oxygen Mixtures

Evaluation of Decomposition Property of Photoresist by Oxygen Radicals Using Helium-Oxygen Mixtures

Utilizing photosensitive polymers to evaluate UV radiation exposures in different plasma chamber configurations

Monitoring vacuum ultraviolet (UV/VUV) emission in plasma systems is challenging as it requires specialized diagnostic systems or sensors to be compatible with these devices. This study addresses different reactor configurations and plasma chemistries with various levels of UV emission and their effects on a known set of polymers. First, the effect of He plasma treatment of organic underlayer (NFC-1400) and e-beam resist (hydrogen silsesquioxane) on line-space patterning of polysilicon at sub-100 nm pitch was investigated. By applying He plasma exposure, both before and after patterning of the optical underlayer, a significant improvement in line edge roughness (LER) from 2.5 to 1.4 nm was observed. To understand the plasma treatment mechanisms, polymers were exposed to synchrotron VUV light at 62 nm (or 20.0 eV), which coincides with the He VUV emission range (50–60 nm), followed by etching of poly-Si, and were found to have similar LER results. The refraction index measurements for both the optical underlayer and the e-beam resist revealed the key finding that the polymers absorption maxima corresponded exactly to the wavelength of ∼60 nm. Second, the impact of inductively coupled and microwave plasma configurations on etch rates and chemical properties of photoresists were investigated. Identifying specific photon-induced modifications on polymers can help detect UV/VUV emission in the plasma and decouple ion and photon effects on materials. Poly(methyl methacrylate) and poly(4-vinylphenol)-based photoresists were exposed to argon (Ar) and nitrogen (N2) plasmas. Surface and elemental analyses confirmed that plasma effects on chemical modifications, surface roughness, and etch rate were significantly higher for poly(methyl methacrylate) compared to poly(4-vinylphenol)-based photoresists. Detailed elemental and molecular structure analyses of these polymers showed relatively higher damage to both species caused from the inductively coupled plasma, which is ultimately correlated with a higher UV/VUV emission.

Computational modeling of carbon nanotubes for photoresistor applications

In this paper, photoresistive properties in pristine and homogeneously boron and nitrogen doped semiconducting single-walled carbon nanotubes is studied. The calculations are based on density functional theory in combination with Non-Equilibrium Greens Function formalism. The resistance in the SWCNT models is found to decrease with the increasing flux levels. At low electrode voltages, nitrogen doped model shows more photoresistive effect while at high electrode voltages, the most significant photoresistive effect is found in boron doped model. The study reveals that the resistance of the proposed SWCNT systems is dependent on the light intensity, and the conventional boron and nitrogen doping increases the photoresistance by manifold. The models are promising for wide range of applications in the future electronic industry.

Single photomask lithography for shape modulation of micropatterns

Photolithography has been used to fabricate various micropatterns; however, recent efforts have focused on the scaling-down process to reduce the feature sizes of the desired patterns and not redefining existing micropatterns. Here, we describe single-mask photolithography method for the shape modulation of designed patterns with a single-mask that utilizes the intrinsic properties of a monolithic photoresist. Our novel approach can achieve various micropatterns with different open areas by adjusting a few fabrication parameters. To create the modulated micropatterns, the material and physical parameters (e.g., soft-bake temperature and exposure dose) were altered and successfully produced modulated shapes. This approach can produce well-controlled micropatterns with desired shapes over a large area with high throughput. Furthermore, our new approach enables access to numerous varieties of micropatterns and can be expandable to two dimensional (2D) and thre dimensional (3D) multiscale architectures.

Optical properties of photoresists for femtosecond 3D printing: refractive index, extinction, luminescence-dose dependence, aging, heat treatment and comparison between 1-photon and 2-photon exposure

Femtosecond 3D printing has emerged as an important technology for manufacturing nano- and microscopic optical devices and elements. Detailed knowledge of the dispersion in the visible and near-infrared spectral range is crucial for the design of these optical elements. Here we provide refractive index measurements for different UV-doses, aging times, heat treatment and 2-photon exposed structures for the photoresists IP-S, IP-Dip, IP-L, OrmoComp, IP-Visio, and PO4. We use a modified and automized Pulfrich refractometer setup, utilizing critical angles of total internal reflection with an accuracy of 5·10−4 in the visible and near-infrared spectral range. We compare Cauchy and Sellmeier fits to the dispersion curves. We also give Abbe numbers and Schott Catalog numbers of the almost entirely polymerized resists. Additionally, we provide quantitative extinction and luminescence measurements for all photoresists.

Light-driven micron-scale 3D hydrogel actuator produced by two-photon polymerization microfabrication

Light-driven micro/nano-actuators are one of the most important topics in the biomedical micro-electromechanical systems (MEMS) field. Currently, their development is hampered due to the difficulties in designing and fabricating biocompatible light-driven microactuators with the dimensions less than one hundred micrometres and a response time in the order of seconds. In this work, gel photoresists were prepared by embedding photothermal surface-modified Fe3O4 nanoparticles (NPs) into a mixture that included a photoinitiator, photosensitizer, monomers, crosslinkers and solvents. Macroscopic poly(N-isopropylacrylamide) (PNIPAM)/nano-Fe3O4 hydrogels were prepared by ultraviolet photopolymerization of gel photoresists, which showed good temperature-responsive volume changes and light-triggered bending deformation. Then the two-photon polymerization (TPP) microfabrication properties of gel photoresists with 0, 0.48 and 0.95 wt% Fe3O4 NPs were investigated in detail. Importantly, after the TPP microfabrication and subsequent solvent-exchange procedure, a double-armed near-infrared (NIR)-light-driven three-dimensional (3D) hydrogel microcantilever with a size of ∼26 μm was successfully fabricated. The hydrogel microactuator had a fast response time of ∼0.033 s in water under NIR radiation and showed good reversibility. Furthermore, the distance between the two arms of the hydrogel microcantilever could be manipulated by controlling the laser focus and incident laser power.

Multiresolution layered manufacturing

Purpose Two-photon polymerization (TPP) has become one of the most popular techniques for stereolithography at very high resolutions. When printing relatively large structures at high resolutions, one of the main limiting factors is the printing time. The purpose of this paper is to present a new slicing algorithm to minimize printing times. Design/methodology/approach Typically, slicing algorithms used for TPP do not take into account the fact that TPP can print at a range of resolutions (i.e. with different heights and diameters) by varying parameters such as exposure time, laser power, photoresist properties and optical arrangements. This work presents multiresolution layered manufacturing (MLM), a novel slicing algorithm that processes 3D structures to separate parts manufacturable at low resolution from those that require a higher resolution. Findings MLM can significantly reduce the printing time of 3D structures at high resolutions. The maximum theoretical speed-up depends on the range of printing resolutions, but the effective speed-up also depends on the geometry of each 3D structure. Research limitations/implications MLM opens the possibility to significantly decrease printing times, potentially opening the use of TPP to new applications in many disciplines such as microfluidics, metamaterial research or wettability. Originality/value There are many instances of previous research on printing at several resolutions. However, in most cases, the toolpaths have to be manually arranged. In some cases, previous research also automates the generation of toolpaths, but they are limited in various ways. MLM is the first algorithm to comprehensively solve this problem for a wide range of true 3D structures.

Ultraviolet transmittance of SU-8 photoresist and its importance in multi-wavelength photolithography

The transmission properties of SU-8 photoresist in the ultraviolet (UV) range are reported for resist thicknesses between 1 and 150 μm in the soft-baked state prior to lithographic exposure. Multiple transmission wavelengths in the UV region between 200 and 400 nm are found to be suitable candidates for self-limiting exposure and thus polymerization depth. This enables a novel method to realize microarchitectures via standard photolithographic techniques. Examples of three dimensional hollow polymer microarchitectures are presented to demonstrate the advantages of this method. The coefficient of attenuation is calculated using Beer–Lambert’s principle for different resist thicknesses.

Magnetic-field-driven ultra-small 3D hydrogel microstructures: Preparation of gel photoresist and two-photon polymerization microfabrication

In the biomedical micro-electromechanical systems (MEMS) field, the fabrication of three-dimensional (3D) magnetic hydrogel microdevices and microactuators with sizes smaller than 100 μm is difficult. In this paper, magnetic-field-driven 3D hydrogel microstructures were fabricated through four steps: the synthesis of surface-modified Fe3O4 nanoparticles (Fe3O4 NPs), the preparation of a magnetic gel photoresist, two-photon polymerization microfabrication, and a solvent-exchange process. For the preparation of a stable magnetic gel photoresist, surface-modified Fe3O4 NPs with an average size of 7.8 nm were synthetized and well dispersed in gel photoresist. The magnetic gel photoresist exhibited a good UV photopolymerization effect, and a magnetic-field-driven macroscopic hydrogel was prepared. The two-photon polymerization properties of gel photoresists with various Fe3O4 NP contents were investigated in detail, and the minimum width of fabricated lines reached 106 nm for the photoresist with 0.32 wt% Fe3O4 NPs. Three hydrogel microstructures—the Qingdao University logo, a magnetically actuated micro-rod, and a magnetically actuated micro-nail—were successfully fabricated using a gel photoresist with 0.96 wt% Fe3O4 NPs. Importantly, obvious and reversible external-magnetic-field-driven bending behavior of the 3D hydrogel micro-nail with a size of 10 μm was observed.

Photoresist: Fabrication, Characterization and Its Sensitivity on the Exposures of X-Ray and Ultraviolet

The epoxy resin-based photoresist is fabricated by mixing of resin (polymer), sodium acetate trihydrate and ethanol in mass variation using heated magnetic stirrer at 100 rpm speed and temperature of 75 °C. Sodium acetate trihydrate and ethanol each play role as photoactive compound (PAC) and solvent, respectively. Photoresist thin films were grown through spin coating method in voltage 5 V during the 60 s and heating temperature of 150 °C for 15 min. To determine photoresist sensitivity, ultraviolet and X-ray were exposed on the photoresist surfaces. The fabricated photoresist properties are densities of 1 g·mL−1 to 1.23 g·mL−1, dynamic viscosities of 7 Cp to 22 Cp and kinematic viscosities of 7 Cst to 18 Cst. The absorbances of thin films are in the wavelength range of 350 nm to 1050 nm at the maximum absorbances of 0.2 to 0.5 in the wavelength g-line, h-line, and i-line. The generated maximum current achieved (1.84 × 10−8) A. The microstructures of epoxy-based photoresist seem homogeneous. The sensitivities of UV exposures show a photochemistry reaction on photoresist occurred, however for X-ray exposure no reaction found.

Enhanced mechanical properties of the high-resolution EUVL patterns of hybrid photoresists containing hexafluoroantimonate

The present study investigates the mechanical properties of hybrid photoresists in the context of their pattern-collapse behaviors. The mechanical properties such as the DMT (Derjaguin, Muller, Toropov) modulus and tip-sample adhesion forces of the high-resolution patterns obtained from two hybrid EUV photo-resists, 1.5% & 2.15%-MAPDSA-MAPDST bearing hexafluoroantimonate and triflate counter ion moieties have been investigated using peak force quantitative nano-mechanical mapping (PF-QNM) technique. The mechanical properties of the well resolved high-resolution 90–20 nm (L/5S) line patterns, 20–32 nm (L/2S-L/5S) lines patterns and nano-features such as line-elbow connections have been investigated and analyzed against the differences in their SbF6− composition. For the 1.5%- MAPDSA-MAPDST resist case the DMT modulus and tip-sample adhesion forces are found strong dependence on the resist line width and line spacing, as compared to 2.15%- MAPDSA-MAPDST resist. There is a significant improvement in the modulus value of 5 GPa for 2.15%-MAPDSA-MAPDST resist in contrary to the ~2.7 GPa for the 1.5%-MAPDSA-MAPDST resist for the 20 nm (L/2S) Line patterns. Similarly, the tip sample adhesion forces on resist surface are also found dependent on patterns aspect ratio as well as on SbF6− content in the resist composition. These studies revealed that an increase of the SbF6− content in the resist formulation, imparts cascading effects to the mechanical properties of their high-resolution nanopatterns, which in turns helps to reduce the pattern collapse resulting in superior patterning performances.

Effect of corona discharge on formation of holographic diffraction gratings in the Cu–As2Se3 thin-film structure

Application of negative corona discharge in the course of recording leads to an increase in the holographic sensitivity of the Cu–As2Se3 structure and diffraction efficiency of the recorded holographic gratings and the relief gratings fabricated with the aid of chemical etching. Positive corona discharge impedes the recording of holographic gratings in the Cu–As2Se3 structure. The Cu–As2Se3 structure exhibits the properties of a negative photoresist under irradiation in the presence of the negative corona discharge. In addition, the dissolution selectivity substantially increases due to the corona discharge.

Functional micro-concrete 3D hybrid structures fabricated by two-photon polymerization

Arbitrary micro-scale three-dimensional (3D) structures fabrication is a dream to achieve many exciting goals that have been pursued for a long time. Among all these applications, the direct 3D printing to fabricate human organs and integrated photonic circuits are extraordinary attractive as they can promote the current technology to a new level. Among all the 3D printing methods available, two-photon polymerization (2PP) is very competitive as it is the unique method to achieve sub-micron resolution to make any desired tiny structures. For the conventional 2PP, the building block is the photoresist. However, the requirement for the building block is different for different purposes. It is very necessary to investigate and improve the photoresist properties according to different requirements. In this paper, we presented one hybrid method to modify the mechanical strength and light trapping efficiency of the photoresist, which transfers the photoresist into the micro-concretes. The micro-concrete structure can achieve ±22% strength modification via a silica nano-particles doping. The structures doped with gold nano-particles show tunable plasmonic absorption. Dye doped hybrid structure shows great potential to fabricate 3D micro-chip laser.