{"title":"Enhanced plasma etching using nonlinear parameter evolution","authors":"Arjun Moothedath, Zhong Ren","doi":"10.1016/j.mne.2024.100288","DOIUrl":"10.1016/j.mne.2024.100288","url":null,"abstract":"<div><div>This study explores the development and characterization of plasma etching for sub-micron features using a nonlinear evolution of parameter in a three-step cyclic Bosch process. Comparing this nonlinear approach with traditional linear parameter evolution, we aimed to address issues such as bowing at the top of the features and narrowing at the bottom. Constant parameter etching produced tapered profiles, undercutting, and non-uniform scallops due to particle deflection. Linear parameter evolution partially mitigated these problems by balancing etch and deposition cycles and gradually increasing radio frequency power, achieving high selectivity to the photoresist. One nonlinear exponential evolution method resulted in a higher etch rate but caused slight damage to the top-side wall, while the etch depth was reduced. The other nonlinear method balanced the etch and deposition steps more effectively, achieving a comparable etch rate and selectivity to the linear method. Further optimization of this second method led to improved vertical profiles and controlled scallops, achieving greater depth, smoother sidewalls, and higher etch rates. This optimized technique successfully fabricated high aspect ratio periodic sub-micron structures with excellent uniformity across the wafer, demonstrating its potential for achieving even higher aspect ratios with thicker masks.</div></div>","PeriodicalId":37111,"journal":{"name":"Micro and Nano Engineering","volume":"25 ","pages":"Article 100288"},"PeriodicalIF":2.8,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142573318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rahul Singh, Christian Vinther Bertelsen, Maria Dimaki, Winnie Edith Svendsen
{"title":"Dry etch performance of Novolak-based negative e-beam resist","authors":"Rahul Singh, Christian Vinther Bertelsen, Maria Dimaki, Winnie Edith Svendsen","doi":"10.1016/j.mne.2024.100284","DOIUrl":"10.1016/j.mne.2024.100284","url":null,"abstract":"<div><p>Electron beam lithography (EBL) is pivotal for micro- and nanoscale fabrication, offering sub-micron precision. This study explores the utilization of the Novolac-based negative resist AR-N 7520 for EBL and its potential as an etch mask for reactive ion etching (RIE) of silicon. Recent comparisons of negative EBL resists have revealed promising results for AR-N 7520 in terms of resolution and adaptability with other lithography techniques. In this article, we conduct an exploration of patterning of AR-N 7520 (new) for EBL, addressing key parameters in achieving optimal patterning fidelity. Furthermore, we investigate its compatibility with RIE processes, aiming to provide insights into its effectiveness as an etch mask for creating sub-micron silicon structures. Experimental results show that optimal e-beam dose with 100 kV exposure is 300–350 μC/cm<sup>2</sup>. Selectivity of around 9:1 can be achieved by optimizing etching parameters for a continuous etch and higher than 14:1 for a cyclic etch process.</p></div>","PeriodicalId":37111,"journal":{"name":"Micro and Nano Engineering","volume":"25 ","pages":"Article 100284"},"PeriodicalIF":2.8,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2590007224000479/pdfft?md5=1916c605ea23c988a5ccc6c279b435e4&pid=1-s2.0-S2590007224000479-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142158141","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T.M. van den Berg, A. Bosseboeuf, P. Coste, L. Vincent
{"title":"In situ measurements of thermal and pressure dependent stress in SOG films by phase shifting interferometry","authors":"T.M. van den Berg, A. Bosseboeuf, P. Coste, L. Vincent","doi":"10.1016/j.mne.2024.100292","DOIUrl":"10.1016/j.mne.2024.100292","url":null,"abstract":"<div><div>Hydrogen silsesquioxane (HSQ) and Medusa are spin-on-glasses used for several applications and more specifically for electron-beam lithography. To characterize the thermal densification of these resists on silicon, the mean resist film stress was measured in situ as function of temperature up to 600 °C in a vacuum chamber by the curvature method. The curvature was evaluated from 3D profiles of uncoated and coated dies measured by full field phase shifting interferometry. Three resists were investigated: FOx-15, FOx-25 and Medusa-82. The initial resist stress at room temperature after spin coating and baking is slightly tensile and becomes highly tensile above a certain temperature dependent on the resist. This variation is mainly attributed to resists densification. FOx-15 and FOx-25 start densifying at 500 °C, and FOx-25 densifies more than FOx-15. Medusa-82 is densifying around 300 °C and has the highest tensile stress but the film relaxes beyond 405 °C. In the case of FOx-15, it was found that vacuum annealing prevents densification. Finally, we evaluated the in-plane average coefficient of thermal expansion of the resists from stress measurements during cooling to room temperature. For FOx-15, a CTE equal to 1.5 ppm/K is found, while it is close to 0.0±0.2 ppm/K for FOx-25 and 1.3 ppm/K for Medusa-82.</div></div>","PeriodicalId":37111,"journal":{"name":"Micro and Nano Engineering","volume":"25 ","pages":"Article 100292"},"PeriodicalIF":2.8,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142747231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alexander J. Straub , Frank D. Scherag , Mark-Steven Steiner , Thomas Brandstetter , Jürgen Rühe
{"title":"Single cell separation in microplates through micro patterning of “clickable” hydrogels","authors":"Alexander J. Straub , Frank D. Scherag , Mark-Steven Steiner , Thomas Brandstetter , Jürgen Rühe","doi":"10.1016/j.mne.2024.100285","DOIUrl":"10.1016/j.mne.2024.100285","url":null,"abstract":"<div><p>In this study, we report a novel approach for separating microspheres or cells on microstructured surfaces. These structures consist of μ-structured hydrogel coatings fabricated by photolithography on the bottoms of standard plastic microplate wells. The process is based on the deposition and subsequent irradiation of copolymers containing a hydrophilic main component and benzophenone moieties that can react with C, H groups during UV exposure through a photomask, a process known as “C,H insertion crosslinking” (CHic). The photolithographic process is used to generate an egg-box-like topography of the coating. Gravity, Brownian motion, and physical surface interactions drive particles or cells pipetted onto the surfaces to distinct locations on this topography so that after a short time these locations contain only one single particles or cells. We show that the presented technique enables the separation of thousands of objects as different as polymer microparticles or biological cells by simply adding a suspension to the coated wells of the microplate and wait for a short time (a few minutes). This strategy is quite general and not specific to a certain type of cell or microparticle and thus allow effortless separation of particles or cells.</p></div>","PeriodicalId":37111,"journal":{"name":"Micro and Nano Engineering","volume":"25 ","pages":"Article 100285"},"PeriodicalIF":2.8,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2590007224000480/pdfft?md5=82c83607116a2e2bcbb15cedee173954&pid=1-s2.0-S2590007224000480-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142163459","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wiebke Gehlken , Sina Reede , Michael J. Vellekoop
{"title":"Removable support beams to improve the printing outcome of 2-photon-polymerized structures","authors":"Wiebke Gehlken , Sina Reede , Michael J. Vellekoop","doi":"10.1016/j.mne.2024.100283","DOIUrl":"10.1016/j.mne.2024.100283","url":null,"abstract":"<div><p>Using direct-laser writing, 3D microstructures of almost every shape can be fabricated. However, using liquid photoresists, the fabrication of free-floating structures is still challenging. To give stability to those structures during the printing process, support beams can be implemented which are usually not needed for direct-laser writing. With that, free-floating elements can be fixed and are not distorted due to unwanted movement during fabrication. In this work, the design, realization and characterization of support beams for the printing outcome of 2-photon polymerization processes is examined. The support beams described here connect the static and the rotating part of flap-like structures. Experimental results show that two thin cone-shaped support beams are sufficient to stabilize the flaps (typical size <span><math><mn>20</mn><mo>×</mo><mn>50</mn><mspace></mspace><mi>μ</mi><msup><mi>m</mi><mn>2</mn></msup></math></span>) so that they are not distorted during printing. After finishing the writing process, the support beams can be broken with a gentle nitrogen stream and the structures move freely. Structures like these can for example be implemented in microfluidic channels to work as flow direction pointers or self-closing cell traps.</p></div>","PeriodicalId":37111,"journal":{"name":"Micro and Nano Engineering","volume":"24 ","pages":"Article 100283"},"PeriodicalIF":2.8,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2590007224000467/pdfft?md5=3ace89fb3eb57c8c72b28de638ded657&pid=1-s2.0-S2590007224000467-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142130226","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Fabrication Techniques for a Tuneable Room Temperature Hybrid Single-electron Transistor and Field-effect Transistor","authors":"Kai-Lin Chu, Wenkun He, Faris Abualnaja , Mervyn Jones, Zahid Durrani","doi":"10.1016/j.mne.2024.100275","DOIUrl":"10.1016/j.mne.2024.100275","url":null,"abstract":"<div><p>Hybrid room-temperature (RT) silicon single-electron – field effect transistors (SET-FETs) provide a means to switch between ‘classical’, high current FET, and low-power SET operation, using a gate voltage. While operating as a SET, charge on a silicon quantum dot (QD) within the current channel, can be controlled at the one-electron level using the Coulomb blockade effect. This paper investigates nanofabrication methods for sub-10 nm ‘fin’ channel hybrid RT SET-FETs, and their influence on the energy band diagram, and formation of tunnel barriers and QDs, along the channel. Devices are fabricated in heavily <em>n</em>-doped SOI material using electron beam lithography, with thermal oxidation to reduce the as-defined fin width. Effective channel dimensions, following oxidation and excluding Si/SiO<sub>2</sub> interface dopant deactivation, are ∼2.4 nm <span><math><mo>×</mo></math></span> 32 nm <span><math><mo>×</mo></math></span> 20 nm. Dopant disorder, fin width variation at the nanometre scale, and quantum confinement effects are considered as mechanisms for the formation of tunnel barriers and QDs, with dopant disorder the most likely reason. Arrhenius plots of <em>I</em><sub><em>ds</em></sub> vs. 1/<em>T</em> allow extraction of a potential barrier energy ∼0.2 eV along the fin channel. For 180devices fabricated on four chips, 37% show RT SET-FET operation, ∼3 times higher than the corresponding yield observed in previous work on point-contact silicon SETs.</p></div>","PeriodicalId":37111,"journal":{"name":"Micro and Nano Engineering","volume":"24 ","pages":"Article 100275"},"PeriodicalIF":2.8,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2590007224000388/pdfft?md5=f6127414bf77e2409195f5406588ec29&pid=1-s2.0-S2590007224000388-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141852580","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Daniel Fan , Carlas S. Smith , Ranjith R. Unnithan , Sejeong Kim
{"title":"3D printed diffractive optical elements for rapid prototyping","authors":"Daniel Fan , Carlas S. Smith , Ranjith R. Unnithan , Sejeong Kim","doi":"10.1016/j.mne.2024.100270","DOIUrl":"https://doi.org/10.1016/j.mne.2024.100270","url":null,"abstract":"<div><p>A rapid and robust method to fabricate transmission diffractive optical elements in the visible wavelengths is presented. By additive manufacturing of a polymeric photo-resin using 2-photon lithography followed by encasing of the structure in another resin with similar refractive index, the height of the structure can be made much larger, thus trading-off fabrication height for refractive index difference of the two materials. After adjusting for resin shrinkage, different diffractive optical element designs including an m = 1 vortex plate, and Laguerre-Gaussian beams with azimuthal and radial indices of (1,1), (1,2), and (2,1) were demonstrated. Experimental results show intensity patterns matching that of simulations, including size and features, although some aberration was observed, possibly due to fabrication tolerance errors or beam misalignment. This technique adds to the toolkit of micro-optics fabrication methods using additive manufacturing and 3D printing, and it would be beneficial for rapid prototyping and integration with miniaturised systems.</p></div>","PeriodicalId":37111,"journal":{"name":"Micro and Nano Engineering","volume":"24 ","pages":"Article 100270"},"PeriodicalIF":2.8,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2590007224000339/pdfft?md5=634c39b0d7fb887009b196d90e86e226&pid=1-s2.0-S2590007224000339-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141583269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Superhydrophobic and oleophobic Nylon, PES and PVDF membranes using plasma nanotexturing: Empowering membrane distillation and contributing to PFAS free hydrophobic membranes","authors":"Eleftherios Manouras , Dimosthenis Ioannou , Angelos Zeniou , Andreas Sapalidis , Evangelos Gogolides","doi":"10.1016/j.mne.2024.100269","DOIUrl":"https://doi.org/10.1016/j.mne.2024.100269","url":null,"abstract":"<div><p>As freshwater demand is constantly increasing, water purification via membrane distillation (MD) emerges as a promising water production technology, especially when combined with the use of superhydrophobic membranes. Here, following our previous work [1] we extend our universal, environmentally friendly, plasma nanotexturing and hydrophobization technology for rendering practically any type of membrane superhydrophobic and oleophobic. Thus, we render three commercial porous membranes superhydrophobic, namely, polyvinylidene (PVDF 0.45 μm) (initially hydrophobic), polyethersulfone (PES 1.20 μm) and nylon (NY 1.20 μm) (both initially hydrophilic). We demonstrate superhydrophobic, superoleophobic (down to 40mn/m surface tension) and oleophobic properties (down to 30mN/m surface tension) for PVDF, PES and Nylon membranes thus paving the way for their use with low surface tension waste streams. Moreover, the technology presented herein not only improves existing hydrophobic membranes but may lead to elimination of the use of Teflon-like fluorinated hydrophobic membranes altogether in the future, thereby contributing to the PFAS (Per and Poly Fluoro Alkyl Substances) and Teflon-like membrane use reduction. We subsequently evaluated the performance of the treated membranes in direct contact membrane distillation (DCMD) for desalination of sea-like water (35 g/L NaCl). All membranes showed enhanced water flux with an increase of >13% compared to the pristine hydrophobic PVDF membranes for at least 2 h of continuous operation, with salt rejection exciding 99.99%.</p></div>","PeriodicalId":37111,"journal":{"name":"Micro and Nano Engineering","volume":"24 ","pages":"Article 100269"},"PeriodicalIF":2.8,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2590007224000327/pdfft?md5=6ce0a6f4fcb6a6ea7e031a7cd08bd887&pid=1-s2.0-S2590007224000327-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141592695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Ag-deposited nanostructured Boehmite substrates for the detection of explosives with surface enhanced Raman spectroscopy","authors":"Anastasios Dimitriou , Athina S. Kastania , Panagiotis Sarkiris , Vasyl Shvalya , Nikolaos Papanikolaou , Uros Cvelbar , Evangelos Gogolides","doi":"10.1016/j.mne.2024.100279","DOIUrl":"10.1016/j.mne.2024.100279","url":null,"abstract":"<div><p>We propose aluminum oxide (Boehmite) sputter-deposited with Ag substrates for Surface-Enhanced Raman Spectroscopy (SERS). These substrates are cost-effective and easily fabricated by heating aluminum in an aqueous environment to create Boehmite, followed by Ag sputtering. The metal deposition is optimized, resulting in random arrays of Ag nanostructures with a diameter of ∼100 nm and a spacing of <100 nm leading to significant enhancement of the Raman signal. The performance and sensitivity of the substrates are initially tested with the use of Crystal Violet analyte which results in limits of detection close to 10<sup>−10</sup>M. These substrates are used for the rapid detection of four different explosive compounds: Nitroglycerin (NG), Picric Acid (PA), Cyclotrimethylene trinitramine (RDX) and 2,4,6-Trinitrophenylmethylnitramine (Tetryl). A series of Raman spectra are collected for these four selected explosives on the fabricated substrates and principal component analysis (PCA) was used for proper evaluation and identification of the corresponding measured spectra.</p></div>","PeriodicalId":37111,"journal":{"name":"Micro and Nano Engineering","volume":"24 ","pages":"Article 100279"},"PeriodicalIF":2.8,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S259000722400042X/pdfft?md5=de10afe563b5ce1f74f89ab83ce3319b&pid=1-s2.0-S259000722400042X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141962774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Metallization of polyetherimide with 3D structures by supercritical carbon dioxide-assisted electroless NiP plating","authors":"Ami Iwasaki , Tomoyuki Kurioka , Po-Wei Cheng , Chun-Yi Chen , Tso-Fu Mark Chang , Kei Takase , Hiroshi Ishihata , Masato Sone","doi":"10.1016/j.mne.2024.100271","DOIUrl":"https://doi.org/10.1016/j.mne.2024.100271","url":null,"abstract":"<div><p>Polyetherimide (PEI) with 3-dimensional (3D) structures is a promising material for applications in electronic devices because of its numerous attractive properties. In the applications of PEI, the low electrical conductivity is often a shortcoming. The electrical conductivity can be improved by a metallization process. Electroless plating is a common metallization process for polymeric materials; however, conventional electroless plating process scarcely provides the metallized PEI. In this work, we overcome this limitation by a supercritical carbon dioxide (scCO<sub>2</sub>)-assisted electroless Ni<img>P plating process. This scCO<sub>2</sub>-assisted electroless Ni<img>P plating allows metallization of PEI with 3D structures and realizes a low electrical resistance suitable for practical use in the electronic devices.</p></div>","PeriodicalId":37111,"journal":{"name":"Micro and Nano Engineering","volume":"24 ","pages":"Article 100271"},"PeriodicalIF":2.8,"publicationDate":"2024-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2590007224000340/pdfft?md5=41872f2bcd2b04fdea495c5e3c930e06&pid=1-s2.0-S2590007224000340-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141583268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}