Combining microstructures of different dimensions benefits from hybrid manufacturing strategies that use nanoimprint for generating regular large area structures and laser lithography for larger grayscale topography. While the individual processes are straightforward, due to the thermoplastic property of the positive resist used for grayscale lithography, diffraction on surface gratings and degradation of photoactive substances require a careful choice of the order of process steps, and balance of process, temperatures, and dimensions.
{"title":"Hybrid structures by direct write lithography—Tuning the contrast and surface topography of grayscale photoresist with nanoimprint","authors":"Sijia Xie, J. Erjawetz, C. Schuster, H. Schift","doi":"10.1116/6.0001206","DOIUrl":"https://doi.org/10.1116/6.0001206","url":null,"abstract":"Combining microstructures of different dimensions benefits from hybrid manufacturing strategies that use nanoimprint for generating regular large area structures and laser lithography for larger grayscale topography. While the individual processes are straightforward, due to the thermoplastic property of the positive resist used for grayscale lithography, diffraction on surface gratings and degradation of photoactive substances require a careful choice of the order of process steps, and balance of process, temperatures, and dimensions.","PeriodicalId":17495,"journal":{"name":"Journal of Vacuum Science & Technology B","volume":"18 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81206520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Evaluations of electron current output from tungsten emitter arrays with Cs and CsI coatings are carried out. The approach is based on first-principles calculations of the material physics including evaluation of the internal potentials, electronic wavefunctions, tunneling probabilities, and work function to predict field emission currents. This is coupled to time-dependent kinetic simulations for the assessment of emitter array currents with an inclusion of many-body Coulomb contributions from the electron swarm, geometric field enhancements with shielding based on a line charge model and dynamic screening from the swarm. Our numerical evaluations for arrays with a hexagonal lattice show the expected role of field screening with reductions in emitter separation. For scaling with emitter number, the results indicate nearest neighbor separations of more than 2.5 times the emitter height, in keeping with previous reports.
{"title":"Evaluation of electron currents from cesium-coated tungsten emitter arrays with inclusion of space charge effects, workfunction changes, and screening","authors":"D. Guo, S. Sami, L. Diaz, M. Sanati, R. Joshi","doi":"10.1116/6.0001185","DOIUrl":"https://doi.org/10.1116/6.0001185","url":null,"abstract":"Evaluations of electron current output from tungsten emitter arrays with Cs and CsI coatings are carried out. The approach is based on first-principles calculations of the material physics including evaluation of the internal potentials, electronic wavefunctions, tunneling probabilities, and work function to predict field emission currents. This is coupled to time-dependent kinetic simulations for the assessment of emitter array currents with an inclusion of many-body Coulomb contributions from the electron swarm, geometric field enhancements with shielding based on a line charge model and dynamic screening from the swarm. Our numerical evaluations for arrays with a hexagonal lattice show the expected role of field screening with reductions in emitter separation. For scaling with emitter number, the results indicate nearest neighbor separations of more than 2.5 times the emitter height, in keeping with previous reports.","PeriodicalId":17495,"journal":{"name":"Journal of Vacuum Science & Technology B","volume":"86 1","pages":"054201"},"PeriodicalIF":1.4,"publicationDate":"2021-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83455306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhaoxian Liu, D. Meng, G. Ren, Xiao Zhang, Yan Han, Lina Wang, Wei Sun, Lichen Sun, R. Yan
Graphene containing intrinsic pores with molecular dimensions is a highly promising material for standard leak elements because of its minimal and stable gas flow. However, the etching of polymethyl methacrylate (PMMA) during the typical graphene transfer process can cause the rupture of graphene on the porous substrate due to the surface tension as the etchant solution dries out. In this article, we simplified the typical graphene transfer process that enabled the transfer of a PMMA/graphene composite membrane onto a macroporous Cu gasket as the leak element and tested the leak rate, time stability, and response time of the composite membrane. The membrane permeation area depends on the pore size of the Cu substrate, which can be controlled by laser ablation or computer numerical control milling. To ensure the accuracy of time stability, the entire test lasted 60 days. The conductance results for two devices with a permeation size of 50 and 500 μm were about 10−17 and 10−14 m3 s−1, and the maximum variation of conductance in 60 days was 14% and 2.6%, respectively. Accordingly, the permeance of the composite membrane for helium can be calculated as 4.17 × 10−12–1.09 × 10−11 Pa m3 (cm2 s Pa)−1. Moreover, the composite membrane has been proven to have a rapid response of about 2 s to the upstream pressure.
石墨烯含有具有分子尺寸的固有孔隙，由于其最小且稳定的气体流动，是一种非常有前途的标准泄漏元件材料。然而，在典型的石墨烯转移过程中，聚甲基丙烯酸甲酯(PMMA)的蚀刻会导致多孔基底上的石墨烯由于蚀刻液干燥时的表面张力而破裂。在本文中，我们简化了典型的石墨烯转移过程，将PMMA/石墨烯复合膜转移到大孔铜衬垫上作为泄漏元件，并测试了复合膜的泄漏率、时间稳定性和响应时间。膜的渗透面积取决于Cu衬底的孔径大小，可以通过激光烧蚀或计算机数控铣削来控制。为了保证时间的准确性和稳定性，整个测试持续了60天。在渗透尺寸为50 μm和500 μm时，两种器件的电导结果分别为10−17和10−14 m3 s−1,60 d内电导的最大变化分别为14%和2.6%。据此，复合膜对氦的透过率可计算为4.17 × 10−12-1.09 × 10−11 Pa m3 (cm2 s Pa)−1。此外，复合膜已被证明对上游压力有大约2s的快速响应。
{"title":"New leak elements for helium based on single-layer graphene composite membranes","authors":"Zhaoxian Liu, D. Meng, G. Ren, Xiao Zhang, Yan Han, Lina Wang, Wei Sun, Lichen Sun, R. Yan","doi":"10.1116/6.0001068","DOIUrl":"https://doi.org/10.1116/6.0001068","url":null,"abstract":"Graphene containing intrinsic pores with molecular dimensions is a highly promising material for standard leak elements because of its minimal and stable gas flow. However, the etching of polymethyl methacrylate (PMMA) during the typical graphene transfer process can cause the rupture of graphene on the porous substrate due to the surface tension as the etchant solution dries out. In this article, we simplified the typical graphene transfer process that enabled the transfer of a PMMA/graphene composite membrane onto a macroporous Cu gasket as the leak element and tested the leak rate, time stability, and response time of the composite membrane. The membrane permeation area depends on the pore size of the Cu substrate, which can be controlled by laser ablation or computer numerical control milling. To ensure the accuracy of time stability, the entire test lasted 60 days. The conductance results for two devices with a permeation size of 50 and 500 μm were about 10−17 and 10−14 m3 s−1, and the maximum variation of conductance in 60 days was 14% and 2.6%, respectively. Accordingly, the permeance of the composite membrane for helium can be calculated as 4.17 × 10−12–1.09 × 10−11 Pa m3 (cm2 s Pa)−1. Moreover, the composite membrane has been proven to have a rapid response of about 2 s to the upstream pressure.","PeriodicalId":17495,"journal":{"name":"Journal of Vacuum Science & Technology B","volume":"1 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88786526","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Riku Katamawari, K. Kawashita, T. Hizawa, Y. Ishikawa
Si-capping-induced surface roughening, accompanying Si–Ge alloying, is reported for strip structures of Ge selectively grown on Si via ultrahigh vacuum chemical vapor deposition. A 0.7-μm-wide strip structure of Ge running in the [110] direction, as well as a 100-μm-wide mesa structure, is selectively grown on an Si (001) surface exposed in an SiO2-masked Si substrate. In contrast to a wide mesa structure with a Ge thickness of 0.5 μm, composed of a (001) plane at the top and {113} facet planes at the sidewalls, the (001) top plane almost disappears for the narrow strip structure. The strip is mainly surrounded with inclined {113} planes near the top and adjacent {111} planes at the side, while the structure near the bottom edges depends on the growth temperature (600/700 °C). An Si cap layer with a thickness of 10 nm or larger is subsequently grown at 600 °C to protect the fragile Ge surface. The scanning electron microscopy observations reveal a roughened surface on the {113} planes, with depressions specifically induced near the boundary with the {111} planes. The Raman spectra indicate that an SiGe alloy is formed on the strip and the wide mesa sidewalls due to the Si–Ge interdiffusion. There is no such SiGe alloy on the (001) plane of the wide mesa top. The Si cap layer with a misfit strain probably works as a stressor for the underlying Ge, applying stress concentrated around the facet boundaries and inducing a mass transport alongside the Si–Ge interdiffusion for strain relaxation. In terms of the fabrication of practical devices, it is important to suppress the roughening and alloying significantly by decreasing the growth temperature for the Si cap layer from 600 to 530 °C.
{"title":"Si-capping-induced surface roughening on the strip structures of Ge selectively grown on an Si substrate","authors":"Riku Katamawari, K. Kawashita, T. Hizawa, Y. Ishikawa","doi":"10.1116/6.0001142","DOIUrl":"https://doi.org/10.1116/6.0001142","url":null,"abstract":"Si-capping-induced surface roughening, accompanying Si–Ge alloying, is reported for strip structures of Ge selectively grown on Si via ultrahigh vacuum chemical vapor deposition. A 0.7-μm-wide strip structure of Ge running in the [110] direction, as well as a 100-μm-wide mesa structure, is selectively grown on an Si (001) surface exposed in an SiO2-masked Si substrate. In contrast to a wide mesa structure with a Ge thickness of 0.5 μm, composed of a (001) plane at the top and {113} facet planes at the sidewalls, the (001) top plane almost disappears for the narrow strip structure. The strip is mainly surrounded with inclined {113} planes near the top and adjacent {111} planes at the side, while the structure near the bottom edges depends on the growth temperature (600/700 °C). An Si cap layer with a thickness of 10 nm or larger is subsequently grown at 600 °C to protect the fragile Ge surface. The scanning electron microscopy observations reveal a roughened surface on the {113} planes, with depressions specifically induced near the boundary with the {111} planes. The Raman spectra indicate that an SiGe alloy is formed on the strip and the wide mesa sidewalls due to the Si–Ge interdiffusion. There is no such SiGe alloy on the (001) plane of the wide mesa top. The Si cap layer with a misfit strain probably works as a stressor for the underlying Ge, applying stress concentrated around the facet boundaries and inducing a mass transport alongside the Si–Ge interdiffusion for strain relaxation. In terms of the fabrication of practical devices, it is important to suppress the roughening and alloying significantly by decreasing the growth temperature for the Si cap layer from 600 to 530 °C.","PeriodicalId":17495,"journal":{"name":"Journal of Vacuum Science & Technology B","volume":"1 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88866165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. J. C. Tinacba, Tomoko Ito, K. Karahashi, M. Isobe, S. Hamaguchi
Silicon (Si)-based materials such as Si and silicon dioxide ( SiO 2) are commonly used as basic components of advanced semiconductor devices. For example, alternating stacks of poly-Si and SiO 2 layers are used in three-dimensional (3D) NAND flash memory devices. Fabrication of high-aspect-ratio deep holes through such stacked materials by plasma etching may be achieved by highly energetic and chemically reactive ion injections to the surface. Etching by sulfur hexafluoride ( SF 6) plasmas can produce ions carrying multiple fluorine (F) atoms and therefore exhibit high etch rates for both Si and SiO 2. In this study, reactive ion etching of Si and SiO 2 materials by SF 5 + ions was examined with the use of molecular dynamics (MD) simulation. For this purpose, a simplified interatomic potential functions model for sulfur (S) was developed that approximately represents molecular moieties or molecules SF n ( n ≤ 6) based on density-functional-theory (DFT) calculations. The etching yields of Si and SiO 2 by SF 5 + ions evaluated by MD simulations with these new potential functions were found to be in good agreement with those obtained from multibeam injection system experiments, which implies that the etching process is essentially due to sputtering enhanced by chemical reactions of F atoms with the surface materials. Analyses of the depth profiles of atomic concentrations of etched surfaces and desorbed species obtained from MD simulations also indicate that the presence of excess F atoms on the surface enhances the etching yield of Si and SiO 2 significantly over corresponding physical sputtering.
硅(Si)基材料，如硅和二氧化硅(sio2)，通常用作先进半导体器件的基本组件。例如，在三维(3D) NAND闪存设备中使用多晶硅和二氧化硅层的交替堆叠。等离子体刻蚀可以通过向表面注入高能量和化学反应性离子来制造高纵横比深孔。六氟化硫(sf6)等离子体蚀刻可以产生携带多个氟(F)原子的离子，因此对Si和sio2都表现出很高的蚀刻速率。本研究采用分子动力学(MD)模拟方法研究了sf5 +离子对Si和sio2材料的反应性离子蚀刻。为此，基于密度泛函理论(DFT)计算，建立了硫(S)的简化原子间势函数模型，该模型近似表示分子段或分子SF n (n≤6)。利用这些新的势函数对SF - 5 +离子对Si和sio2的蚀刻产率进行了MD模拟，结果与多束注入系统实验结果一致，表明蚀刻过程本质上是由F原子与表面材料的化学反应增强的溅射引起的。对刻蚀表面的原子浓度深度分布和MD模拟得到的解吸物质的分析也表明，在表面上存在多余的F原子比相应的物理溅射显著提高了Si和sio2的刻蚀收率。
{"title":"Molecular dynamics simulation for reactive ion etching of Si and SiO2 by SF 5 + ions","authors":"E. J. C. Tinacba, Tomoko Ito, K. Karahashi, M. Isobe, S. Hamaguchi","doi":"10.1116/6.0001230","DOIUrl":"https://doi.org/10.1116/6.0001230","url":null,"abstract":"Silicon (Si)-based materials such as Si and silicon dioxide ( SiO 2) are commonly used as basic components of advanced semiconductor devices. For example, alternating stacks of poly-Si and SiO 2 layers are used in three-dimensional (3D) NAND flash memory devices. Fabrication of high-aspect-ratio deep holes through such stacked materials by plasma etching may be achieved by highly energetic and chemically reactive ion injections to the surface. Etching by sulfur hexafluoride ( SF 6) plasmas can produce ions carrying multiple fluorine (F) atoms and therefore exhibit high etch rates for both Si and SiO 2. In this study, reactive ion etching of Si and SiO 2 materials by SF 5 + ions was examined with the use of molecular dynamics (MD) simulation. For this purpose, a simplified interatomic potential functions model for sulfur (S) was developed that approximately represents molecular moieties or molecules SF n ( n ≤ 6) based on density-functional-theory (DFT) calculations. The etching yields of Si and SiO 2 by SF 5 + ions evaluated by MD simulations with these new potential functions were found to be in good agreement with those obtained from multibeam injection system experiments, which implies that the etching process is essentially due to sputtering enhanced by chemical reactions of F atoms with the surface materials. Analyses of the depth profiles of atomic concentrations of etched surfaces and desorbed species obtained from MD simulations also indicate that the presence of excess F atoms on the surface enhances the etching yield of Si and SiO 2 significantly over corresponding physical sputtering.","PeriodicalId":17495,"journal":{"name":"Journal of Vacuum Science & Technology B","volume":"22 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74136150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
William W. Hernández-Montero, A. Itzmoyotl-Toxqui, C. Zuñiga-Islas
This work reports an experimental study on the synthesis of hydrogenated amorphous silicon-carbon (a-SiC:H) films with improved antireflective and photo-luminescent characteristics. These films were prepared by plasma-enhanced chemical vapor deposition at a radio frequency of 13.56 MHz, varying the thermodynamic parameters of pressure, gas flows, and temperature. Silane (SiH 4), methane (CH 4), and hydrogen (H 2) were the precursor gases. In a first experiment, composition in gas phase was varied and correlated to the composition in solid phase. Absorption spectra, conductivity, refractive index, optical gap, and photoluminescence (PL) were analyzed. Optical gap and fraction of carbon in gas phase showed a linear dependence with the atomic fraction of carbon in solid phase. Results indicated that the Si 0.4C 0.6 alloy exhibited a high PL as well as an optimal combination of optical gap and refractive index to be applied as antireflective coating. The subsequent optimization of PL was carried out by a fractional experiment, by varying pressure, H 2 flow, and temperature. Results revealed that PL can be improved at high pressure, without H 2 flow, and low temperature during glow discharge. Enhancement of PL was correlated to the proper concentration of silicon and carbon in the films, low dark conductivity, negative AM 1.5 conductivity, fluctuating current at low voltage, the increment of Si − H 2, C − H 2, and C = C bonds, along with vibrational energies in the range of 3190–3585 cm − 1.
{"title":"Effect of thermodynamic parameters on properties of silicon-carbon films prepared by radio-frequency plasma-enhanced chemical vapor deposition for anti-reflective and photo-luminescent coatings","authors":"William W. Hernández-Montero, A. Itzmoyotl-Toxqui, C. Zuñiga-Islas","doi":"10.1116/6.0001052","DOIUrl":"https://doi.org/10.1116/6.0001052","url":null,"abstract":"This work reports an experimental study on the synthesis of hydrogenated amorphous silicon-carbon (a-SiC:H) films with improved antireflective and photo-luminescent characteristics. These films were prepared by plasma-enhanced chemical vapor deposition at a radio frequency of 13.56 MHz, varying the thermodynamic parameters of pressure, gas flows, and temperature. Silane (SiH 4), methane (CH 4), and hydrogen (H 2) were the precursor gases. In a first experiment, composition in gas phase was varied and correlated to the composition in solid phase. Absorption spectra, conductivity, refractive index, optical gap, and photoluminescence (PL) were analyzed. Optical gap and fraction of carbon in gas phase showed a linear dependence with the atomic fraction of carbon in solid phase. Results indicated that the Si 0.4C 0.6 alloy exhibited a high PL as well as an optimal combination of optical gap and refractive index to be applied as antireflective coating. The subsequent optimization of PL was carried out by a fractional experiment, by varying pressure, H 2 flow, and temperature. Results revealed that PL can be improved at high pressure, without H 2 flow, and low temperature during glow discharge. Enhancement of PL was correlated to the proper concentration of silicon and carbon in the films, low dark conductivity, negative AM 1.5 conductivity, fluctuating current at low voltage, the increment of Si − H 2, C − H 2, and C = C bonds, along with vibrational energies in the range of 3190–3585 cm − 1.","PeriodicalId":17495,"journal":{"name":"Journal of Vacuum Science & Technology B","volume":"15 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72927991","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We demonstrate the fabrication of metal and dielectric nanostructures using interference lithography with extreme ultraviolet (EUV) and soft x-ray synchrotron radiation down to a 2.5 nm wavelength. These specific wavelengths are chosen because of the industrial relevance for EUV lithography and because they are in the vicinity of the oxygen absorption edge of the high-resolution hydrogen silsesquioxane photoresist, allowing for the exposure of thick layers. We investigate the requirements to fabricate such structures and demonstrate that tall metal nanostructures with aspect ratios up to 7 could be achieved by EUV interference lithography and subsequent electroplating. We use the unique depth-of-focus-free property of interference and achromatic Talbot lithography to fabricate uniformly tilted dielectric nanostructures.
{"title":"Fabrication of high aspect ratio and tilted nanostructures using extreme ultraviolet and soft x-ray interference lithography","authors":"N. Mojarad, D. Kazazis, Y. Ekinci","doi":"10.1116/6.0001089","DOIUrl":"https://doi.org/10.1116/6.0001089","url":null,"abstract":"We demonstrate the fabrication of metal and dielectric nanostructures using interference lithography with extreme ultraviolet (EUV) and soft x-ray synchrotron radiation down to a 2.5 nm wavelength. These specific wavelengths are chosen because of the industrial relevance for EUV lithography and because they are in the vicinity of the oxygen absorption edge of the high-resolution hydrogen silsesquioxane photoresist, allowing for the exposure of thick layers. We investigate the requirements to fabricate such structures and demonstrate that tall metal nanostructures with aspect ratios up to 7 could be achieved by EUV interference lithography and subsequent electroplating. We use the unique depth-of-focus-free property of interference and achromatic Talbot lithography to fabricate uniformly tilted dielectric nanostructures.","PeriodicalId":17495,"journal":{"name":"Journal of Vacuum Science & Technology B","volume":"15 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82866240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Xiang, A. Singhal, R. Divan, L. Stan, Yuzi Liu, I. Paprotny
This paper describes the theory and results for a new class of low-cost chemoresistive gas sensors designed for selective hydrocarbon gas detection. The sensors utilize a multiwalled carbon nanotube (MWCNT) backbone functionalized with metal oxide nanocrystals. Specifically, nanoparticles were grown on the surface of the MWCNTs using atomic layer deposition. The crystallinity of the ZnO-MWCNTs’ heterostructure was examined by using a high-resolution transmission electron microscope. The structure of the ZnO/MWCNTs was analyzed using a scanning electron microscope and energy dispersive x ray. The Hall effect measurement shows p-type characteristics of the MWCNTs, supporting the typical PN junction formation with n-type ZnO nanocrystals. The electron-donating ability of ZnO provided a strong response to the ppm levels of toluene at room temperature (25 °C) and showed strong selectivity with other volatile organic compound gases such as benzene, methane, and formaldehyde.
{"title":"Selective volatile organic compound gas sensor based on carbon nanotubes functionalized with ZnO nanoparticles","authors":"J. Xiang, A. Singhal, R. Divan, L. Stan, Yuzi Liu, I. Paprotny","doi":"10.1116/6.0000992","DOIUrl":"https://doi.org/10.1116/6.0000992","url":null,"abstract":"This paper describes the theory and results for a new class of low-cost chemoresistive gas sensors designed for selective hydrocarbon gas detection. The sensors utilize a multiwalled carbon nanotube (MWCNT) backbone functionalized with metal oxide nanocrystals. Specifically, nanoparticles were grown on the surface of the MWCNTs using atomic layer deposition. The crystallinity of the ZnO-MWCNTs’ heterostructure was examined by using a high-resolution transmission electron microscope. The structure of the ZnO/MWCNTs was analyzed using a scanning electron microscope and energy dispersive x ray. The Hall effect measurement shows p-type characteristics of the MWCNTs, supporting the typical PN junction formation with n-type ZnO nanocrystals. The electron-donating ability of ZnO provided a strong response to the ppm levels of toluene at room temperature (25 °C) and showed strong selectivity with other volatile organic compound gases such as benzene, methane, and formaldehyde.","PeriodicalId":17495,"journal":{"name":"Journal of Vacuum Science & Technology B","volume":"39 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86600412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Levko, Chandrasekhar Shukla, R. Upadhyay, L. Raja
Plasma etching continues to play a central role in microelectronics manufacturing. As the semiconductor industry continues to shrink critical feature sizes and improves device performance, etch challenges continue to increase due to the requirement of processing smaller features along with new device structures. With their high density and high-aspect ratio features, these structures are challenging to manufacture and have required innovation in multiple areas of wafer processing. Innovations in this technology are increasingly reliant on comprehensive physical and chemical models of plasma etch processes. In the present paper, we develop a new mechanism of plasma chemical reactions for a low-pressure CF4/O2 plasma. We validate this mechanism against available experimental data using the self-consistent axisymmetric fluid model of inductively coupled plasma discharge. We show that this mechanism is in reasonable agreement with the results of experiments both quantitively and qualitatively. Using this mechanism, we analyze the influence of oxygen fraction in the feed gas mixture on the kinetics of the ion species and the fluorine and oxygen atom yield.
{"title":"Computational study of plasma dynamics and reactive chemistry in a low-pressure inductively coupled CF4/O2 plasma","authors":"D. Levko, Chandrasekhar Shukla, R. Upadhyay, L. Raja","doi":"10.1116/6.0001028","DOIUrl":"https://doi.org/10.1116/6.0001028","url":null,"abstract":"Plasma etching continues to play a central role in microelectronics manufacturing. As the semiconductor industry continues to shrink critical feature sizes and improves device performance, etch challenges continue to increase due to the requirement of processing smaller features along with new device structures. With their high density and high-aspect ratio features, these structures are challenging to manufacture and have required innovation in multiple areas of wafer processing. Innovations in this technology are increasingly reliant on comprehensive physical and chemical models of plasma etch processes. In the present paper, we develop a new mechanism of plasma chemical reactions for a low-pressure CF4/O2 plasma. We validate this mechanism against available experimental data using the self-consistent axisymmetric fluid model of inductively coupled plasma discharge. We show that this mechanism is in reasonable agreement with the results of experiments both quantitively and qualitatively. Using this mechanism, we analyze the influence of oxygen fraction in the feed gas mixture on the kinetics of the ion species and the fluorine and oxygen atom yield.","PeriodicalId":17495,"journal":{"name":"Journal of Vacuum Science & Technology B","volume":"56 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84575103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Silander, C. Forssén, J. Zakrisson, M. Zelan, O. Axner
By measuring the refractivity and the temperature of a gas, its pressure can be calculated from fundamental principles. The most sensitive instruments are currently based on Fabry–Perot cavities where a laser is used to probe the frequency of a cavity mode. However, for best accuracy, the realization of such systems requires exceptional mechanical stability. Gas modulation refractometry (GAMOR) has previously demonstrated an impressive ability to mitigate the influence of fluctuations and drifts whereby it can provide high-precision (sub-ppm, i.e., sub-parts-per-million or sub- 10 − 6) assessment of gas refractivity and pressure. In this work, two independent GAMOR-based refractometers are individually characterized, compared to each other, and finally compared to a calibrated dead weight piston gauge with respect to their abilities to assess pressure in the 4–25 kPa range. The first system, referred to as the stationary optical pascal (SOP), uses a miniature fixed point gallium cell to measure the temperature. The second system, denoted the transportable optical pascal (TOP), relies on calibrated Pt-100 sensors. The expanded uncertainty for assessment of pressure ( k = 2) was estimated to, for the SOP and TOP, [ ( 10 mPa ) 2 + ( 10 × 10 − 6 P ) 2 ] 1 / 2 and [ ( 16 mPa ) 2 + ( 28 × 10 − 6 P ) 2 ] 1 / 2, respectively. While the uncertainty of the SOP is mainly limited by the uncertainty in the molar polarizability of nitrogen (8 ppm), the uncertainty of the TOP is dominated by the temperature assessment (26 ppm). To verify the long-term stability, the systems were compared to each other over a period of 5 months. It was found that all measurements fell within the estimated expanded uncertainty ( k = 2) for comparative measurements (27 ppm). This verified that the estimated error budget for the uncorrelated errors holds over this extensive period of time.
{"title":"Optical realization of the pascal—Characterization of two gas modulated refractometers","authors":"I. Silander, C. Forssén, J. Zakrisson, M. Zelan, O. Axner","doi":"10.1116/6.0001042","DOIUrl":"https://doi.org/10.1116/6.0001042","url":null,"abstract":"By measuring the refractivity and the temperature of a gas, its pressure can be calculated from fundamental principles. The most sensitive instruments are currently based on Fabry–Perot cavities where a laser is used to probe the frequency of a cavity mode. However, for best accuracy, the realization of such systems requires exceptional mechanical stability. Gas modulation refractometry (GAMOR) has previously demonstrated an impressive ability to mitigate the influence of fluctuations and drifts whereby it can provide high-precision (sub-ppm, i.e., sub-parts-per-million or sub- 10 − 6) assessment of gas refractivity and pressure. In this work, two independent GAMOR-based refractometers are individually characterized, compared to each other, and finally compared to a calibrated dead weight piston gauge with respect to their abilities to assess pressure in the 4–25 kPa range. The first system, referred to as the stationary optical pascal (SOP), uses a miniature fixed point gallium cell to measure the temperature. The second system, denoted the transportable optical pascal (TOP), relies on calibrated Pt-100 sensors. The expanded uncertainty for assessment of pressure ( k = 2) was estimated to, for the SOP and TOP, [ ( 10 mPa ) 2 + ( 10 × 10 − 6 P ) 2 ] 1 / 2 and [ ( 16 mPa ) 2 + ( 28 × 10 − 6 P ) 2 ] 1 / 2, respectively. While the uncertainty of the SOP is mainly limited by the uncertainty in the molar polarizability of nitrogen (8 ppm), the uncertainty of the TOP is dominated by the temperature assessment (26 ppm). To verify the long-term stability, the systems were compared to each other over a period of 5 months. It was found that all measurements fell within the estimated expanded uncertainty ( k = 2) for comparative measurements (27 ppm). This verified that the estimated error budget for the uncorrelated errors holds over this extensive period of time.","PeriodicalId":17495,"journal":{"name":"Journal of Vacuum Science & Technology B","volume":"17 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2021-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81233417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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