Post Exposure Bake Research Articles

Resist image quality control via acid diffusion constant and/or photodecomposable quencher concentration in the fabrication of 11 nm half-pitch line-and-space patterns using extreme-ultraviolet lithography

Extreme-ultraviolet (EUV) lithography will be applied to the high-volume production of semiconductor devices with 16 nm half-pitch resolution and is expected to be extended to that of devices with 11 nm half-pitch resolution. With the reduction in the feature sizes, the control of acid diffusion becomes a significant concern. In this study, the dependence of resist image quality on TPEBDacid and photodecomposable quencher concentration was investigated by the Monte Carlo method on the basis of the sensitization and reaction mechanisms of chemically amplified EUV resists. Here, TPEB and Dacid are the postexposure baking (PEB) time and the acid diffusion constant, respectively. The resist image quality of 11 nm line-and-space patterns is discussed in terms of line edge roughness (LER) and stochastic defect generation. For the minimization of LER, it is necessary to design and control not only the photodecomposable quencher concentration but also TPEBDacid. In this case, Dacid should be adjusted to be 0.3–1.5 nm2 s−1 for a PEB time of 60 s with optimization of the balance among LER and stochastic pinching and bridging. Even if it is difficult to decrease Dacid to the range of 0.3–1.5 nm2 s−1, the image quality can still be controlled via only the photodecomposable quencher concentration, although LER and stochastic pinching and bridging are slightly increased. In this case, accurate control of the photodecomposable quencher concentration and the reduction in the initial standard deviation of the number of protected units are required.

Fabrication of SU-8 Based Three-Dimensional Carbon Microelectrodes Array As Anode Material for Lithium Ion Batteries

Introduction The development of three-dimensional (3D) microelectrodes is essential not only to achieve high energy and power density Li-ion batteries but also to minimize the ohmic losses and therefore achieve better performance. In this work, we used SU-8, an epoxy based negative photoresist which yields hard carbon upon pyrolysis for fabricating 3D micro-post arrays as electrodes1. The SU-8 derived 3D carbon microelectrodes on Silicon (Si) wafer has been reported earlier in literature, however the capacity values were quite moderate2. This is due to the high resistance offered by Si wafer used as a collector. Our group reported recently that the gravimetric reversible capacity value may be almost doubled when SU-8 derived carbon film was prepared on stainless steel (SS) wafer as compared to Si wafer. This inspires us further to fabricate 3D carbon microelectrodes array on SS wafer and to test their electrochemical performance. Experimental SU-8 2100 was spin coated on cleaned SS wafer. Prebaking, UV exposure and post-exposure baking conditions were optimized to prepare SU-8 based 3D micropillars with an aspect ratio of 2 (50µm height and 25µm diameter), and 35µm spacing using photolithography. As-obtained micropillars were then pyrolysed under the controlled N2 atmosphere in a tubular furnace at 900ºC to obtain 3D carbon microelectrode arrays. As-fabricated, 3D carbon microelectrode array on SS wafer was used as working electrode while lithium foil as the counter electrode in Swagelok half-cell assembly to test their electrochemical performance using potentiostat/galvanostat. Results and discussions Figure 1a shows the optical profiler image of SU-8 derived 3D carbon microelectrode array. It was observed that the 3D cylindrical morphology was retained after carbonization however there was nearly 50% shrinkage. As-obtained 3D carbon microelectrode arrays were found to have 26µm height, 16µm diameter, and 40µm spacing. Galvanostatic charge-discharge experiments were carried out at 37.2 mA/g current density. These 3D carbon microelectrode arrays have shown a high discharge capacity (~600 mAh/g) even after 165 continuous charge/discharge cycles (Figure 1b). This is significantly higher than the reported values for 3D carbon micropillars on Si wafer2. A comparison of volumetric capacity was also made. Further detailed characterization of these carbon microelectrodes and their electrochemical performance with cyclic voltammetry results will be presented during the conference.

I-line photoresist composed of multifunctional acrylate, photo initiator, and photo acid generator, which can be patterned after g-line photo-crosslinking

A positive-tone photoresist which can be patterned after photo-crosslinking was prepared. The photoresist is mainly composed of a multifunctional acrylate having a tertiary ester structure, a photo radical initiator, and a photo-acid generator (PAG). Photolysis of the initiator induces crosslink of the acrylate, and acid generated from the PAG catalyzes decomposition of the crosslinked acrylate. By loading the acrylate with both the initiator, that is sensitive to g-line, and the PAG, that is sensitive to i-line, the crosslink of the coating was promoted by g-line exposure. The subsequent i-line photolithography yielded the patterns of the resulting crosslinked film. Photolithography of both conventional negative- and positive-tone photoresists was performed on the crosslinked films. The patterned film stacks could be removed after additional i-line exposure followed by post-exposure bake and development.

Fabrication of flexible organic thin-film transistors based on negative acting photosensitive novolak polymer as an organic gate insulator

ABSTRACTA diazonaphthoquinone (DNQ)-based cross-linkable photo-sensitive cresol novolak resin through acid-catalyzed condensation with melamine molecules is presented as an organic gate insulator (OGI) for the fabrication of poly(3-hexylthiophene) thin-film transistors. This novolak OGI exhibits a remarkably smooth surface of Ra 1.0 nm and RMS 0.3 nm and shows excellent chemical resistance against common process solvents upon a post exposure bake ≥150°C. The corresponding metal-insulator-metal diode incorporated with a 200 nm thick OGI demonstrates remarkable low leakage current level of 10 pA/cm2 @3 MV/cm. Bottom-contact poly(3-hexylthiophene) (P3HT) transistors with novolak OGI on both rigid glass and flexible polyethylene terephthalate (PET) plastic substrates are further demonstrated, suggesting that novolak polymer is a promising candidate for realizing a high performance OGI at low processing temperature.

Fabricating method of SU-8 photoresist conical nozzle for inkjet printhead

ABSTRACTA novel conical nozzle fabrication method for piezoelectric inkjet printhead is proposed based on the microelectromechanical system technology. By optimizing the exposure gap, exposure dose, postexposure bake (PEB), and development time, the SU-8 conical nozzle was fabricated. After thermal bonding with an open chamber, the piezoelectric inkjet printhead chamber was formed. The results show that the optimum SU-8 conical nozzle can be fabricated by applying exposure dose of 105 mJ/cm2, exposure gap of 50 µm, PEB temperature of 65°C, PEB time of 10 min, and development time of 210 s. The final size of optimum conical nozzle is the large aperture of 30.46 ± 1.17 µm, small aperture of 20.34 ± 1.42 µm, and nozzle height of 45.38 ± 1.02 µm.

(Invited) Structural Evolution of Hafnium Methacrylate Nanoclusters Following Electron-Beam Irradiation from in Situ ir Spectroscopy

High absorption metal and main group oxide nanoclusters have recently become the subject of intense investigation due to their potential as alternatives to conventional organic chemically amplified photoresists for negative tone patterning in the extreme ultraviolet (EUV) range. It is believed that the low energy secondary electrons generated from photoionization of the nanoclusters are responsible for the chemistry that occurs following irradiation. Despite their potential, little is known about many aspects of their function as resist materials; in particular, the role of high absorption elements in the absorption/photoionization process, the role of electrons of different energies, the formation of radicals and chemically reactive species and the overall structural changes that occur at each stage of processing. Thus, the precise atomic mechanism underlying solubility switching upon irradiation remains unknown. We have investigated one such class of materials: nanoclusters based on a hafnium oxide core decorated with methacrylic acid ligands (HfMAA) , using a combination of in situ infrared (IR) spectroscopy and x-ray photoemission spectroscopy (XPS). Thin films (10-30 nm) of the HfMAA nanoclusters deposited onto SiO2 from solution are characterized by XPS and IR spectroscopy in conjunction with density functional calculations. The mechanisms of solubility switching following EUV exposure are investigated using irradiation with low energy electrons to emulate the photoexcited carriers generated in the EUV absorption process. Using in situ IR spectroscopy, we are able to monitor the structural evolution of the nanoclusters at each stage of processing, beginning from the initial deposition to post application bake (PAB), electron irradiation, post exposure bake (PEB) and development. Monochromatic electron beams with energies ranging from 5 eV up to the typical EUV wavelength of 92 eV enable a correlation between the role of secondary electron energy with chemistry and functional character. In conjunction with XPS analysis, these measurements detail the structural evolution of the films under typical processing conditions, providing insight into the solubility switching mechanism of this emerging class of inorganic photoresists.

Negative tone photolithography with photo-sensitised polymethyl methacrylate (PMMA)

We describe the science and technology of negative tone photolithography using polymethyl methacrylate (PMMA), photo-sensitised with the addition of the commercial photoinitiator – Irgacure 651. This versatile two-active-ingredient resist system is shown to enable negative tone photolithography which can be customised to application requirements by adjusting the ratio of the two ingredients. This study describes the complete lithographic process – from resist preparation to pattern transfer – in considerable detail. Furthermore, we also elucidate the mechanism of resist action through exploration of the effects of such parameters as the molecular weight of PMMA, exposure wavelength, post-exposure bake conditions and resist development temperature, among others. This work also demonstrates that photo-cross-linkable resists can be made resistant to dry etching by a post-development blanket UV exposure step. Finally, we also show example structures fabricated using both additive and subtractive techniques, with the use of this resist system.

Comparison of Conventional and Variable Frequency Microwave Curing of SU8 Photoresist: Effects on the Dielectric, Thermal, and Morphological Properties

Variable Frequency Microwave (VFM) is known to be a rapid, volumetric, and selective form of heating which has shown potential as an alternative technique for the processing of negative-tone SU8 photoresist in the Micro-Electro-Mechanical System (MEMS) industry. A comparison of thermal properties of the films cured during the softbake and post exposure bake process using different techniques, i.e. conventional thermal curing, VFM curing, and a combination of both (referred to as hybrid, HY), was investigated using a Differential Scanning Calorimeter (DSC) and Thermogravimetric Analysis (TGA). A significant increase on the degree of cure (between 13-23%) was observed using the VFM over the hybrid and hotplate curing which means that SU8 curing at lower temperatures or rapid curing is possible. The increase in cure rates can be attributed to a combination of heat transfer and the unique capability of microwave to couple with the sample (selective heating). The improvement in curing at the same processing temperatures has important implications for processing thick films. It was found that regardless of curing methods, crosslink densities increased as the baking temperature increased, resulting in lower dielectric properties. Despite higher crosslinking contents, VFM cured samples decomposed at 2-4°C lower temperatures. In addition to better thermal properties, VFM offered satisfactory microstructure at lower curing temperatures; however, high processing temperatures could result in film cracking.

Analysis of stochastic effects in chemically amplified poly(4-hydroxystyrene-co-t-butyl methacrylate) resist

Understanding of stochastic phenomena is essential to the development of a highly sensitive resist for nanofabrication. In this study, we investigated the stochastic effects in a chemically amplified resist consisting of poly(4-hydroxystyrene-co-t-butyl methacrylate), triphenylsulfonium nonafluorobutanesulfonate (acid generator), and tri-n-octylamine (quencher). Scanning electron microscopy (SEM) images of resist patterns were analyzed by Monte Carlo simulation on the basis of the sensitization and reaction mechanisms of chemically amplified extreme ultraviolet resists. It was estimated that a ±0.82σ fluctuation of the number of protected units per polymer molecule led to line edge roughness formation. Here, σ is the standard deviation of the number of protected units per polymer molecule after postexposure baking (PEB). The threshold for the elimination of stochastic bridge generation was 4.38σ (the difference between the average number of protected units after PEB and the dissolution point). The threshold for the elimination of stochastic pinching was 2.16σ.

Thick SU8 microstructures prepared by broadband UV lithography and the applications in MEMS devices

Thick SU8 microstructures with high aspect ratio and good side wall quality were fabricated by ultraviolet (UV) lithography, and the processing parameters were comprehensively studied. It proves that the adhesion of SU8 on silicon (Si) substrates is influenced by Si-OH on the surface, and can be improved by the HF treatment. Cracks and delamination are caused by large internal stress during fabrication process, and are significantly influenced by soft bake and post-exposure bake processes. The internal stress is reduced by a low post-exposure bake exposure temperature of 85 °C for 40 min. A three-step soft bake enhances the reflowing of SU8 photoresist, and results in uniform surface and less air bubbles. The vertical side wall is obtained with the optimized exposure dose of 800 mJ/cm2 for the thickness of 160 μm. Using the optimized fabrication process combined with a proper structure design, dense SU8 micro pillars are achieved with the aspect ratio of 10 and the taper angle of 89.86°. Finally, some possible applications of SU8 in micro-electromechanical system (MEMS) device are developed and demonstrated.

Pyrolytic 3D Carbon Microelectrodes for Electrochemistry

This work presents the fabrication and characterization of multi-layered three-dimensional (3D) pyrolysed carbon microelectrodes for electrochemical applications. For this purpose, an optimized UV photolithography and pyrolysis process with the negative tone photoresist SU-8 has been developed. The fabricated three electrode electrochemical cell is characterized with cyclic voltammetry (CV) using the standard potassium ferri-ferrocyanide redox probe. Carbon materials have several attractive characteristics as microelectrodes for electrochemical applications, such as wide potential window, good electrochemical activity, chemical stability, and ease in surface functionalization [1]. The most common carbon microfabrication techniques (i.e. screen printing) produce two-dimensional (2D) electrodes, which limit the detection sensitivity. Hence several 3D microfabrication techniques have been explored in recent years amongst which the carbon MEMS (C-MEMS) technique is the most promising one. C-MEMS is a simple and cost-effective method for carbon electrode fabrication, where a patterned polymer template treated at high temperature (~900°C) in inert atmosphere (N2 or Ar) is transformed into pyrolysed carbon [2]. This process enables fabrication of 2D and 3D electrodes with possibility for tailoring ad-hoc designs and unique sensitivities for specific applications. Due to this, pyrolysed carbon is becoming increasingly attractive for numerous applications, such as novel sensors and scaffolds for cell analysis [3]. However fabrication of a conducting 3D microstructure with feature sizes in the micron-range still remains a challenge. In this work an optimized UV photolithography and pyrolysis process for SU-8 based on highly controlled exposure dose and modified baking time is presented to obtain multi-layered 3D carbon microelectrodes for electrochemistry (figure 1.A). SU-8 2005 (5.6µm) is spin coated on a Si/SiO2 wafer, soft baked (SB) at 50ᵒC for 30min followed by UV exposure (E1 – 210mJ cm-2) and post exposure bake (PEB) at 50ᵒC for 1h (figure 1.A.a). A second thick layer of SU-8 2075 (76µm) is spin coated, SB at 50ᵒC for 6h and UV exposed (E2 – 149mJ cm-2) (figure 1.A.b). A second partial exposure E3 – 28mJ cm-2 is performed to obtain a suspended layer followed by a PEB at 50ᵒC for 8h (figure 1.A.c). The partial exposure dose at wavelength 365nm and the low temperature (50ᵒC) baking steps plays a critical role in fabricating suspended layer. Non cross-linked SU-8 is developed in propylene glycol monomethyl ether acetate (PGMEA) for 30min (figure 1.A.d). The obtained SU-8 polymer templates are then pyrolysed at 900ᵒC for 1h in an N2 environment to obtain suspended 3D pyrolysed carbon microelectrodes (figure.1.A.e). By sequentially repeating the steps shown in figure 1.A. b, c and d followed by a final development step, a multi-layered polymer template can be obtained which can be pyrolysed to produce 3D carbon microelectrodes (figure 1.A.f). The height of the singe carbon layer (figure 1.A.e) is 21.10µm which includes a suspended layer of 2.25µm. The diameter of circles in the suspended layer is 11.50µm. The small carbon microstructures are shown in figure 1.B with structures of 4µm (mesh) and 18µm (mesh boundaries). Depending on the desired application, different 3D carbon microelectrodes can be fabricated (figure 1.B). Figure 1.C shows the electrochemical characterization of a three electrodes system, comparing planar and 3D carbon working electrodes. The cyclic voltammograms performed in 10mM ferri-ferrocyanide show higher peak current (2 folds higher) for the 3D microelectrodes compared to the 2D ones (figure 1.C). The 3D microelectrodes potentially increase the overall sensitivity in amperometric monitoring of cell response due to the increase surface area and enhanced interaction with cells [3]. Reference: [1] R. L. McCreery, “Advanced carbon electrode materials for molecular electrochemistry,” Chem. Rev., vol. 108, no. 7, pp. 2646–2687, 2008. [2] R. Martinez-Duarte, “SU-8 Photolithography as a Toolbox for Carbon MEMS,” Micromachines, vol. 5, no. 3, pp. 766–782, 2014. [3] L. Amato, A. Heiskanen, C. Caviglia, F. Shah, K. Zór, M. Skolimowski, M. Madou, L. Gammelgaard, R. Hansen, E. G. Seiz, M. Ramos, T. R. Moreno, A. Martínez-Serrano, S. S. Keller, and J. Emnéus, “Pyrolysed 3D-Carbon Scaffolds Induce Spontaneous Differentiation of Human Neural Stem Cells and Facilitate Real-Time Dopamine Detection,” Adv. Funct. Mater., vol. 24, no. 44, pp. 7042–7052, 2014. Figure 1

Additive chemistry and distributions in photoresist thin films

The lithographic performance of thin photoresist films is a function of the distribution of formulation components, such as photoacid generator (PAG) molecules, and how these components undergo chemical modification and migrate within the film during the lithography processing steps. Argon gas cluster ion beam – secondary ion mass spectrometry depth profiles were used to monitor the PAG and quencher base distributions before and after exposure and postexposure bake processing steps for different photoresist formulations. PAG and quencher base distributions were correlated to depth of focus lithographic performance results.

Characterization for the photomask fabrication based on a high-resolution technique with a non-chemically amplified resist and a post-exposure bake

A high-resolution technique has been developed for the fabrication of photomasks for 10nm logic nodes and beyond. Current mask manufacturing techniques use a chemically amplified resist (CAR) material that has a complex mechanism of acid generation; this complicates the criteria for selecting the polymer and the quencher for industrial purposes. It is therefore important to validate non-CAR materials as alternative solutions for mask fabrication. In this research, we used diluted ZEP520A as a non-CAR material in conjunction with a JBX9000 variable-shaped electron-beam (VSB) lithography tool. Additionally, a post-exposure bake (PEB), routinely used in mask fabrication, was also applied. We investigated the effects of the PEB temperature on the fabrication of masks from non-CAR resists, and we demonstrated the feasibility of using a PEB as a high-resolution technique. The critical dimensions (CDs) for 1:1 line-and-space, isolated space, and isolated line patterns on a diluted ZEP520A resist were measured and showed a shrinkage, an extension effect, and retention of the integrity of the shape after the PEB process, respectively. Furthermore, the line-edge roughness (LER) of the 1:1 line-and-space and isolated space CDs was improved by approximately 40% by optimizing the PEB temperature. We investigated the process characteristics of this PEB annealing effect by examining the hardness of the cured resist with and without exposure to PEB at various temperatures, with the aim of elucidating the underlying mechanism. Optimizing the PEB temperature of the non-CAR increased the resist contrast, annealing the resist and improving the LER. This permitted us to demonstrate an advanced fabrication technique capable of high resolutions of the order of 20nm. The insights gained from the optimization of the PEB process might be useful in advanced methods of fabricating masks of the next generation.

One-step fabrication of submicrostructures by low one-photon absorption direct laser writing technique with local thermal effect

In this work, local thermal effect induced by a continuous-wave laser has been investigated and exploited to optimize the low one-photon absorption (LOPA) direct laser writing (DLW) technique for fabrication of polymer-based microstructures. It was demonstrated that the temperature of excited SU8 photoresist at the focusing area increases to above 100 °C due to high excitation intensity and becomes stable at that temperature thanks to the use of a continuous-wave laser at 532 nm-wavelength. This optically induced thermal effect immediately completes the crosslinking process at the photopolymerized region, allowing obtain desired structures without using the conventional post-exposure bake (PEB) step, which is usually realized after the exposure. Theoretical calculation of the temperature distribution induced by local optical excitation using finite element method confirmed the experimental results. LOPA-based DLW technique combined with optically induced thermal effect (local PEB) shows great advantages over the traditional PEB, such as simple, short fabrication time, high resolution. In particular, it allowed the overcoming of the accumulation effect inherently existed in optical lithography by one-photon absorption process, resulting in small and uniform structures with very short lattice constant.

Fabricating a high-resolution mask with improved line-edge roughness by using a nonchemically amplified resist and a postexposure bake.

The authors have developed a high-resolution technique for fabricating photomasks at the 10-nm half-pitch logic nodes and beyond. Current mask-manufacturing techniques use a chemically amplified resist (CAR) that has a complex mechanism of acid generation, complicating the criteria for selecting the polymer and the quencher for industrial purposes. Thus, it is important to study fabricating masks with non-CARs. The authors exposed a non-CAR, diluted ZEP520A, to variable-shaped electron-beam lithography and used a postexposure bake (PEB) to modify the resist. Studying how the PEB temperature affected the non-CAR and resultant masks, the authors demonstrate that their technique can produce high-resolution structures. By measuring the critical dimensions (CDs), the authors show that the PEB shrunk, enlarged, and retained the size of 1:1 line-and-space, isolated space, and isolated line patterns, respectively. By optimizing the PEB temperature, the authors improved the line-edge roughness (LER) of the 1:1 line-and-space and isolated space CDs by ∼40%. To understand how the PEB affected the resultant structures, the authors measured the hardness of cured resists with and without a PEB at various temperatures. Optimizing the PEB temperature of the non-CAR increased the resist contrast, annealing the resist and improving the LER. As such, their technique is capable of high resolutions on the order of 20 nm. The insights the authors gained from optimizing the PEB might be useful when fabricating next-generation masks.

High resolution spin-on electron beam lithography resist with exceptional dry etching resistance

Presently, no resist material has suitable properties to satisfy simultaneously all requirements on lateral resolution and plasma etching resistance for pattern transfer of high aspect ratio nano-structures.Herein, a recent innovative alumina spin-on material for use as both positive and negative high resolution resist for electron beam lithography (EBL) is presented. This system turns into an almost completely inorganic alumina system when exposed to the electron beam, showing exceptional selectivity (100:1), compared to even the most robust polymeric resist, when used as mask for dry etching of silicon in fluorinated plasmas, obviating the need for a hardmask layer deposition. A full characterization of the resist selective removal under different processing conditions, such as electrons acceleration voltage and post-exposure bake temperature and time, is presented. Owing to the high selectivity and high resolution, silicon nano-structures of size down to 11nm and high aspect ratio (up to 20) have been obtained for the first time in a one-step process.

Theoretical study of fabrication of line-and-space patterns with 7 nm quarter-pitch using electron beam lithography with chemically amplified resist process: III. Post exposure baking on quartz substrates

Electron beam (EB) lithography is a key technology for the fabrication of photomasks for ArF immersion and extreme ultraviolet (EUV) lithography and molds for nanoimprint lithography. In this study, the temporal change in the chemical gradient of line-and-space patterns with a 7 nm quarter-pitch (7 nm space width and 21 nm line width) was calculated until it became constant, independently of postexposure baking (PEB) time, to clarify the feasibility of single nano patterning on quartz substrates using EB lithography with chemically amplified resist processes. When the quencher diffusion constant is the same as the acid diffusion constant, the maximum chemical gradient of the line-and-space pattern with a 7 nm quarter-pitch did not differ much from that with a 14 nm half-pitch under the condition described above. Also, from the viewpoint of process control, a low quencher diffusion constant is considered to be preferable for the fabrication of line-and-space patterns with a 7 nm quarter-pitch on quartz substrates.

In situ SU-8 silver nanocomposites.

Nanocomposite materials containing metal nanoparticles are of considerable interest in photonics and optoelectronics applications. However, device fabrication of such materials always encounters the challenge of incorporation of preformed nanoparticles into photoresist materials. As a solution to this problem, an easy new method of fabricating silver nanocomposites by an in situ reduction of precursors within the epoxy-based photoresist SU-8 has been developed. AgNO3 dissolved in acetonitrile and mixed with the epoxy-based photoresist SU-8 forms silver nanoparticles primarily during the pre- and post-exposure soft bake steps at 95 °C. A further high-temperature treatment at 300 °C resulted in the formation of densely homogeneously distributed silver nanoparticles in the photoresist matrix. No particle growth or agglomeration of nanoparticles is observed at this point. The reported new in situ silver nanocomposite materials can be spin coated as homogeneous thin films and structured by using UV lithography. A resolution of 5 µm is achieved in the lithographic process. The UV exposure time is found to be independent of the nanoparticle concentration. The fabricated silver nanocomposites exhibit high plasmonic responses suitable for the development of new optoelectronic and optical sensing devices.

Fabrication of a high-resolution mask by using variable-shaped electron beam lithography with a non-chemically amplified resist and a post-exposure bake

A high-resolution technique was developed for fabrication of photomasks for 10-nm-technology nodes and beyond. Current mask manufacturing techniques use a chemically amplified resist (CAR) photoresist material that has a complex mechanism of acid generation that obscures the criteria for selecting the polymer, quencher, and crosslinker for industrial purposes. It is therefore important to validate non-CAR materials as alternative solutions for mask fabrication. In this research, diluted ZEP520A was used as a non-CAR material in conjunction with a JBX9000 electron-beam lithography (EBL) tool. Additionally, a post-exposure bake (PEB) is normally used in mask fabrication. The PEB method was also used in this research, and we investigated its temperature dependence. Critical dimensions (CDs) of 1:1 line-and-space, isolated space, and isolated line patterns on a diluted ZEP520A resist were measured and showed CD shrinkage, an extension effect, and retention of the integrity of the shape after the PEB process. A resolution of the order of 20nm was attained and the insights gained from optimization of the PEB process might be usefully applied in advanced methods for fabricating masks of the next generation.

Optimization on Conventional Photolithography Process of 0.98 μm Gap Design for Micro Gap Biosensor Application

.Pattern design transfer is the most crucial step in fabrication. Even a small mistake in fabrication can result in device damage or poor performance. To ensure the device performs perfectly, exact design and dimension pattern should be perfectly transferred onto wafer substrate. In this paper, optimization of conventional photolithography process of 0.98μm gap design for micro gap biosensor application is presented. The micro gap pattern on chrome mask is used and the effect of coating profile, UV light, and Post Exposure Bake (PEB) process are investigated. The conventional photolithography process (using a micro gap mask) starts after the silicon oxide, polysilicon and aluminium have been deposited on top of the substrate. Each set of experiment conducted by pairing the element investigated coating profile, UV light, and PEB, with the normal specification of photolithography process. It was observed that 0.98μm gap size can be achieved by choosing suitable process parameters i.e. thickness of coating profile, time and temperature used for UV light and PEB.