Para-substituted benzenes, such as 1,4-benzene dithiol and 1,4-phenyl diisocyanide, have been observed to oligomerize on the Au(111) surface by incorporating gold adatoms extracted from the substrate. This work investigates if oligomerization occurs for an analogous but asymmetric linker, 4-isocyanophenyl disulfide (ICPD) on Au(111). This molecule is comprised of both disulfide and isocyanide terminal groups attached to the phenyl ring. The resulting surface structures formed on Au(111) following exposure to ICPD are studied using scanning tunneling microscopy (STM). 1,4-isocyanophenyl thiolate (ICPT), formed through scission of ICPD’s disulfide bond, was also found to oligomerize on the surface, and potential oligomer structures and binding geometries are proposed with the aid of density functional theory (DFT) calculations, along with simulated STM images of the resulting structures. It is observed in this work that ICPT forms oligomeric structures that cover large sections of the substrate and appear to create etch pits resulting from gold atom extraction. Numerous potential binding geometries are investigated based on the distances between substrate gold atom adsorption sites compared to the monomer length. Selected structural candidates were optimized using DFT and were used to generate simulated STM images using the Tersoff–Hamann method to compare with experiment. It has been shown previously that the isocyanide- and thiol-connected oligomers conduct electrons, suggesting the possibility that the asymmetric oligomers found here might form the basis for fabricating molecular diodes.
{"title":"Self-assembled oligomeric structures of an asymmetric molecular linker; 4-isocyanophenyl disulfide on Au(111)","authors":"Robert Bavisotto, Dustin Olson, W. Tysoe","doi":"10.1116/6.0003603","DOIUrl":"https://doi.org/10.1116/6.0003603","url":null,"abstract":"Para-substituted benzenes, such as 1,4-benzene dithiol and 1,4-phenyl diisocyanide, have been observed to oligomerize on the Au(111) surface by incorporating gold adatoms extracted from the substrate. This work investigates if oligomerization occurs for an analogous but asymmetric linker, 4-isocyanophenyl disulfide (ICPD) on Au(111). This molecule is comprised of both disulfide and isocyanide terminal groups attached to the phenyl ring. The resulting surface structures formed on Au(111) following exposure to ICPD are studied using scanning tunneling microscopy (STM). 1,4-isocyanophenyl thiolate (ICPT), formed through scission of ICPD’s disulfide bond, was also found to oligomerize on the surface, and potential oligomer structures and binding geometries are proposed with the aid of density functional theory (DFT) calculations, along with simulated STM images of the resulting structures. It is observed in this work that ICPT forms oligomeric structures that cover large sections of the substrate and appear to create etch pits resulting from gold atom extraction. Numerous potential binding geometries are investigated based on the distances between substrate gold atom adsorption sites compared to the monomer length. Selected structural candidates were optimized using DFT and were used to generate simulated STM images using the Tersoff–Hamann method to compare with experiment. It has been shown previously that the isocyanide- and thiol-connected oligomers conduct electrons, suggesting the possibility that the asymmetric oligomers found here might form the basis for fabricating molecular diodes.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"43 15","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141709749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sudipto Saha, Lingyu Meng, D. Yu, A. F. M. Anhar Uddin Bhuiyan, Hongping Zhao, U. Singisetti
We report on the growth of Si-doped homoepitaxial β-Ga2O3 thin films on (010) Ga2O3 substrates via metal-organic chemical vapor deposition (MOCVD) utilizing triethylgallium (TEGa) and trimethylgallium (TMGa) precursors. The epitaxial growth achieved an impressive 9.5 μm thickness at 3 μm/h using TMGa, a significant advance in material growth for electronic device fabrication. This paper systematically studies the Schottky barrier diodes fabricated on the three MOCVD-grown films, each exhibiting variations in the epilayer thickness, doping levels, and growth rates. The diode from the 2 μm thick Ga2O3 epilayer with TEGa precursor demonstrates promising forward current densities, the lowest specific on-resistance, and the lowest ideality factor, endorsing TEGa’s potential for MOCVD growth. Conversely, the diode from the 9.5 μm thick Ga2O3 layer with TMGa precursor exhibits excellent characteristics in terms of lowest leakage current, highest on-off ratio, and highest reverse breakdown voltage of −510 V without any electric field management, emphasizing TMGa’s suitability for achieving high growth rates in Ga2O3 epilayers for vertical power electronic devices.
{"title":"High growth rate metal organic chemical vapor deposition grown Ga2O3 (010) Schottky diodes","authors":"Sudipto Saha, Lingyu Meng, D. Yu, A. F. M. Anhar Uddin Bhuiyan, Hongping Zhao, U. Singisetti","doi":"10.1116/6.0003533","DOIUrl":"https://doi.org/10.1116/6.0003533","url":null,"abstract":"We report on the growth of Si-doped homoepitaxial β-Ga2O3 thin films on (010) Ga2O3 substrates via metal-organic chemical vapor deposition (MOCVD) utilizing triethylgallium (TEGa) and trimethylgallium (TMGa) precursors. The epitaxial growth achieved an impressive 9.5 μm thickness at 3 μm/h using TMGa, a significant advance in material growth for electronic device fabrication. This paper systematically studies the Schottky barrier diodes fabricated on the three MOCVD-grown films, each exhibiting variations in the epilayer thickness, doping levels, and growth rates. The diode from the 2 μm thick Ga2O3 epilayer with TEGa precursor demonstrates promising forward current densities, the lowest specific on-resistance, and the lowest ideality factor, endorsing TEGa’s potential for MOCVD growth. Conversely, the diode from the 9.5 μm thick Ga2O3 layer with TMGa precursor exhibits excellent characteristics in terms of lowest leakage current, highest on-off ratio, and highest reverse breakdown voltage of −510 V without any electric field management, emphasizing TMGa’s suitability for achieving high growth rates in Ga2O3 epilayers for vertical power electronic devices.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"222 18","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141692466","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Despite its reputation for being nonquantitative, the TOF-SIMS technique is quite capable of providing quantifiable results. Static and near static SIMS measurements are never chaotic (that is subject to large changes due to small variations in the sample), and the instruments can be well controlled to provide highly reproducible results. These results can be replicated by different teams using similar instruments and even reproduced via correlation studies with data from substantially different tools. It is true that absolute concentrations cannot be calculated but must be derived via the use of standards produced by other techniques. Where accuracy (the correctness of the results) is what is needed, this is the approach that must be taken. Furthermore, the results can be nonlinear (especially when the differences in the surfaces being measured are at the atomic percent range and larger, a result of the “matrix effect”) and in these cases, enough standards must be obtained to determine the shape of the function that relates the SIMS results to actual quantities. In most cases, however, relative quantification obtained with sufficient precision (sufficiently narrow distribution of results on identical samples) is most important and key to the ability to evaluate and improve materials and processes. For relative comparisons, TOF-SIMS is usually an excellent analytical method. As with any technique as sophisticated as TOF-SIMS, attention to detail is required to obtain the reproducibility of which the technique is capable. This paper describes many of the details to which an analyst needs to attend to successfully produce repeatable and, therefore, quantifiable results via TOF-SIMS.
{"title":"Best practices for performing quantitative TOF-SIMS analyses","authors":"Alan M. Spool, Lorie Finney","doi":"10.1116/6.0003660","DOIUrl":"https://doi.org/10.1116/6.0003660","url":null,"abstract":"Despite its reputation for being nonquantitative, the TOF-SIMS technique is quite capable of providing quantifiable results. Static and near static SIMS measurements are never chaotic (that is subject to large changes due to small variations in the sample), and the instruments can be well controlled to provide highly reproducible results. These results can be replicated by different teams using similar instruments and even reproduced via correlation studies with data from substantially different tools. It is true that absolute concentrations cannot be calculated but must be derived via the use of standards produced by other techniques. Where accuracy (the correctness of the results) is what is needed, this is the approach that must be taken. Furthermore, the results can be nonlinear (especially when the differences in the surfaces being measured are at the atomic percent range and larger, a result of the “matrix effect”) and in these cases, enough standards must be obtained to determine the shape of the function that relates the SIMS results to actual quantities. In most cases, however, relative quantification obtained with sufficient precision (sufficiently narrow distribution of results on identical samples) is most important and key to the ability to evaluate and improve materials and processes. For relative comparisons, TOF-SIMS is usually an excellent analytical method. As with any technique as sophisticated as TOF-SIMS, attention to detail is required to obtain the reproducibility of which the technique is capable. This paper describes many of the details to which an analyst needs to attend to successfully produce repeatable and, therefore, quantifiable results via TOF-SIMS.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"86 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141714733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hollow cathodes are a common type of vacuum ultraviolet (VUV) light source with a wide range of design and application. We determined the VUV (58.4 nm) intensity distribution of a hollow cathode as a function of current and pressure. Our model describes the intensity distribution of a McPherson 629-like hollow cathode helium plasma within the range of 0.50–1.00 A and 0.50–1.00 Torr as a ring with a center peak. We found that for all pressures and currents considered, the ring emits more VUV light than the center peak. We also found that the center peak has a minimum VUV light emission near 0.9 Torr.
{"title":"Empirical analysis of a hollow cathode’s intensity distribution in the vacuum ultraviolet range","authors":"S. C. Olsen, D. D. Allred, R. R. Vanfleet","doi":"10.1116/6.0003633","DOIUrl":"https://doi.org/10.1116/6.0003633","url":null,"abstract":"Hollow cathodes are a common type of vacuum ultraviolet (VUV) light source with a wide range of design and application. We determined the VUV (58.4 nm) intensity distribution of a hollow cathode as a function of current and pressure. Our model describes the intensity distribution of a McPherson 629-like hollow cathode helium plasma within the range of 0.50–1.00 A and 0.50–1.00 Torr as a ring with a center peak. We found that for all pressures and currents considered, the ring emits more VUV light than the center peak. We also found that the center peak has a minimum VUV light emission near 0.9 Torr.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"50 22","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141345136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Joseph R. Vella, M. A. I. Elgarhy, Qinzhen Hao, Vincent M. Donnelly, David B. Graves
This work complements our previous manuscript [J. Vac. Sci. Technol. A41, 062602 (2023)] where predictions from molecular dynamics (MD) simulations of silicon–chlorine–argon (Si–Cl2–Ar) atomic layer etching (ALE) are compared to experiments. When etch product distributions for atomic chlorine (Cl) and silicon chlorides were initially compared to optical emission spectroscopy (OES) signals, it appeared that there was a discrepancy between the MD predictions and experimental results at higher ion fluences. Experiments showed a relatively long period of nearly constant Cl-containing etch products released from the ion-bombarded surface (referred to as the “plateau”) but this effect was not observed in MD simulations. In this report, we demonstrate that the “plateau” observed in the OES signals is most likely due to the desorption of Cl-containing etch products from the walls of the reactor and subsequent adsorption on the Si substrate. Experiments varying the gas residence time in the chamber while keeping incoming gas concentrations and pressure constant support this interpretation. We also conducted experiments with an additional Ar-only flow in the chamber to reduce the concentration of Cl-containing species on the chamber walls. For both sets of flow modification experiments, we observe results consistent with the hypothesis that Cl-containing species desorbing from chamber walls are a significant cause of the observed discrepancy between MD predictions and experimental observations. If the measured OES signals are corrected for this “additional” source of Cl-containing species at the surface, the MD predictions and measured OES signals are in excellent agreement. This further supports the predictive capability of MD simulations to accurately capture the relevant physical and chemical processes in plasma-assisted ALE processes. We provide an order of magnitude estimate of the required density of Cl-containing species that would account for the additional etch products observed. Finally, we discuss the implications of this effect on ALE in plasma nanofabrication.
这项工作是对我们以前的手稿[J. Vac. Sci. Technol. A41, 062602 (2023)]的补充，其中将硅-氯-氩（Si-Cl2-Ar）原子层刻蚀（ALE）的分子动力学（MD）模拟预测与实验进行了比较。最初将原子氯（Cl）和硅氯化物的蚀刻产物分布与光学发射光谱（OES）信号进行比较时发现，在较高离子通量下，MD 预测与实验结果之间存在差异。实验结果表明，离子轰击表面释放的含 Cl 蚀刻产物（称为 "高原"）在一段相对较长的时间内几乎保持不变，但在 MD 模拟中却没有观察到这种效应。在本报告中，我们证明了在 OES 信号中观察到的 "高原 "很可能是由于含 Cl 的蚀刻产物从反应器壁上解吸并随后吸附在硅基底上造成的。在保持输入气体浓度和压力不变的情况下，改变气体在反应室中的停留时间的实验支持了这一解释。我们还进行了实验，在反应室中增加了仅含 Ar 的气流，以降低反应室壁上含 Cl 物种的浓度。在这两组流量调节实验中，我们观察到的结果与假设一致，即从腔室壁上解吸的含 Cl 物种是造成 MD 预测值与实验观测值之间差异的重要原因。如果根据表面含 Cl 物种的 "额外 "来源对测量的 OES 信号进行校正，则 MD 预测结果和测量的 OES 信号非常一致。这进一步证明了 MD 模拟的预测能力，可以准确捕捉等离子体辅助 ALE 过程中的相关物理和化学过程。我们提供了含 Cl 物种所需密度的数量级估计值，以解释所观察到的额外蚀刻产物。最后，我们讨论了这种效应对等离子纳米制造中 ALE 的影响。
{"title":"Reactor wall effects in Si–Cl2–Ar atomic layer etching","authors":"Joseph R. Vella, M. A. I. Elgarhy, Qinzhen Hao, Vincent M. Donnelly, David B. Graves","doi":"10.1116/6.0003651","DOIUrl":"https://doi.org/10.1116/6.0003651","url":null,"abstract":"This work complements our previous manuscript [J. Vac. Sci. Technol. A41, 062602 (2023)] where predictions from molecular dynamics (MD) simulations of silicon–chlorine–argon (Si–Cl2–Ar) atomic layer etching (ALE) are compared to experiments. When etch product distributions for atomic chlorine (Cl) and silicon chlorides were initially compared to optical emission spectroscopy (OES) signals, it appeared that there was a discrepancy between the MD predictions and experimental results at higher ion fluences. Experiments showed a relatively long period of nearly constant Cl-containing etch products released from the ion-bombarded surface (referred to as the “plateau”) but this effect was not observed in MD simulations. In this report, we demonstrate that the “plateau” observed in the OES signals is most likely due to the desorption of Cl-containing etch products from the walls of the reactor and subsequent adsorption on the Si substrate. Experiments varying the gas residence time in the chamber while keeping incoming gas concentrations and pressure constant support this interpretation. We also conducted experiments with an additional Ar-only flow in the chamber to reduce the concentration of Cl-containing species on the chamber walls. For both sets of flow modification experiments, we observe results consistent with the hypothesis that Cl-containing species desorbing from chamber walls are a significant cause of the observed discrepancy between MD predictions and experimental observations. If the measured OES signals are corrected for this “additional” source of Cl-containing species at the surface, the MD predictions and measured OES signals are in excellent agreement. This further supports the predictive capability of MD simulations to accurately capture the relevant physical and chemical processes in plasma-assisted ALE processes. We provide an order of magnitude estimate of the required density of Cl-containing species that would account for the additional etch products observed. Finally, we discuss the implications of this effect on ALE in plasma nanofabrication.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"33 49","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141354229","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The cyclic two-step process, comprised of energetic H2 plasma followed by HF wet clean or in situ NF3 plasma, demonstrates Si3N4 layer-by-layer removal capability exceeding 10 nm per cycle, surpassing typical atomic layer etch methods by an order of magnitude. In this paper, we investigated the surface reaction mechanisms via first principle density functional theory simulations and surface analysis. The results unveiled that energetic H2 plasma, in the first step, selectively removes nitrogen (N) in preference to silicon (Si), generating ammonia (NHx) and transforming Si3N4 into SiON upon exposure to air, which becomes removable by HF wet clean in the second step. For the second step employing in situ NF3 plasma, it further leverages H-passivated surfaces to enhance NF3 dissociation and provide alternative reaction pathways to yield volatile byproducts such as SiHF3 and SiFx, thereby significantly improving nitride removal efficiency.
{"title":"Mechanism study of H2-plasma assisted Si3N4 layered etch","authors":"Ying Rui, Sumeet Pandey, Chenmeng Hsie, Lan Li","doi":"10.1116/6.0003653","DOIUrl":"https://doi.org/10.1116/6.0003653","url":null,"abstract":"The cyclic two-step process, comprised of energetic H2 plasma followed by HF wet clean or in situ NF3 plasma, demonstrates Si3N4 layer-by-layer removal capability exceeding 10 nm per cycle, surpassing typical atomic layer etch methods by an order of magnitude. In this paper, we investigated the surface reaction mechanisms via first principle density functional theory simulations and surface analysis. The results unveiled that energetic H2 plasma, in the first step, selectively removes nitrogen (N) in preference to silicon (Si), generating ammonia (NHx) and transforming Si3N4 into SiON upon exposure to air, which becomes removable by HF wet clean in the second step. For the second step employing in situ NF3 plasma, it further leverages H-passivated surfaces to enhance NF3 dissociation and provide alternative reaction pathways to yield volatile byproducts such as SiHF3 and SiFx, thereby significantly improving nitride removal efficiency.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"60 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141360137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
High Aspect Ratio Contact (HARC) hole etch is one of the most challenging processes that require many efforts to optimize etch condition. As the aspect ratio increases, novel issues, such as “distortion” and “twisting,” have been highlighted. Since they cause nonaxisymmetric features along the hole axis, it is difficult to understand the etch mechanism correctly, and therefore, taking a 3D profile image is essential to evaluate the exact etch profile. In this study, we created the models for HARC etch with a cell-based Particle Monte Carlo topography simulator by fitting both vertical and horizontal cross-sectional profiles carefully to the experimental results. Moreover, we attempted to apply a model optimization algorithm. By collaboration of human and the algorithm, modeling engineers can minimize a try-and-error approach, and a precise 3D simulation model can be created much faster than before. As a result, the distortion and twisting profiles were reproduced very well on the simulator, and thus, it is expected that the simulator can be utilized as a practical tool for an assistance of process optimization.
高纵横比接触（HARC）孔蚀刻是最具挑战性的工艺之一，需要付出许多努力来优化蚀刻条件。随着高宽比的增加，"变形 "和 "扭曲 "等新问题凸显出来。由于它们会导致沿孔轴线的非轴对称特征，因此很难正确理解蚀刻机制，因此，拍摄三维剖面图像对于评估准确的蚀刻剖面至关重要。在本研究中，我们使用基于单元的粒子蒙特卡洛形貌模拟器创建了 HARC 刻蚀模型，将垂直和水平截面轮廓与实验结果进行了仔细拟合。此外，我们还尝试应用模型优化算法。通过人与算法的协作，建模工程师可以最大限度地减少试错方法，比以前更快地创建精确的三维仿真模型。结果，模拟器很好地再现了变形和扭曲轮廓，因此，该模拟器有望成为协助工艺优化的实用工具。
{"title":"Precise and practical 3D topography simulation of high aspect ratio contact hole etch by using model optimization algorithm","authors":"Tetsuya Nishizuka, Ryo Igosawa, Takahiro Yokoyama, Kaoru Sako, Hironori Moki, M. Honda","doi":"10.1116/6.0003515","DOIUrl":"https://doi.org/10.1116/6.0003515","url":null,"abstract":"High Aspect Ratio Contact (HARC) hole etch is one of the most challenging processes that require many efforts to optimize etch condition. As the aspect ratio increases, novel issues, such as “distortion” and “twisting,” have been highlighted. Since they cause nonaxisymmetric features along the hole axis, it is difficult to understand the etch mechanism correctly, and therefore, taking a 3D profile image is essential to evaluate the exact etch profile. In this study, we created the models for HARC etch with a cell-based Particle Monte Carlo topography simulator by fitting both vertical and horizontal cross-sectional profiles carefully to the experimental results. Moreover, we attempted to apply a model optimization algorithm. By collaboration of human and the algorithm, modeling engineers can minimize a try-and-error approach, and a precise 3D simulation model can be created much faster than before. As a result, the distortion and twisting profiles were reproduced very well on the simulator, and thus, it is expected that the simulator can be utilized as a practical tool for an assistance of process optimization.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"109 51","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141360978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nicholas McDowell, Ritchie Scott-McCabe, Phuc N. Phan, Hiroyuki Kobayashi, Nobuya Miyoshi
Thermal atomic layer etching (ALE) is one promising method to achieve atomic level precision and high conformality over three-dimensional structures that can further enable the manufacturing of gate-all-around devices. Initially, an ALE process using CF4/NH3/Ar remote plasma exposure followed by infrared (IR) annealing was studied on SiCO films. The process showed self-limiting behavior and achieved an etch per cycle (EPC) of 0.2 nm/cycle. To increase the EPC, an O2 remote plasma exposure step was added before the CF4/NH3/Ar plasma exposure step in the ALE cycle. The process achieved an EPC of 1.0 nm/cycle. Measurements of the EPC of the SiCO film showed self-limiting behavior in both the O2 and CF4/NH3/Ar steps. X-ray photoelectron spectroscopy results showed an increase in atomic concentration (AC) of oxygen while the AC of carbon decreased following the exposure of the film to an O2 remote plasma. The results indicate that methyl groups (-CH3) in the top layers of the film are being replaced by hydroxyl (-OH) groups and Si-O-Si bonding. The N1s spectrum showed the formation of an ammonium fluorosilicate (NH4)2SiF6-based surface-modified layer following exposure to a CF4/NH3/Ar remote plasma. IR annealing of the film showed desorption of the ammonium fluorosilicate surface-modified layer and the return to an as grown SiCO film surface composition.
{"title":"Atomic layer etching of SiCO films with surface modification by O2 and CF4/NH3/Ar plasmas and desorption by IR annealing","authors":"Nicholas McDowell, Ritchie Scott-McCabe, Phuc N. Phan, Hiroyuki Kobayashi, Nobuya Miyoshi","doi":"10.1116/6.0003596","DOIUrl":"https://doi.org/10.1116/6.0003596","url":null,"abstract":"Thermal atomic layer etching (ALE) is one promising method to achieve atomic level precision and high conformality over three-dimensional structures that can further enable the manufacturing of gate-all-around devices. Initially, an ALE process using CF4/NH3/Ar remote plasma exposure followed by infrared (IR) annealing was studied on SiCO films. The process showed self-limiting behavior and achieved an etch per cycle (EPC) of 0.2 nm/cycle. To increase the EPC, an O2 remote plasma exposure step was added before the CF4/NH3/Ar plasma exposure step in the ALE cycle. The process achieved an EPC of 1.0 nm/cycle. Measurements of the EPC of the SiCO film showed self-limiting behavior in both the O2 and CF4/NH3/Ar steps. X-ray photoelectron spectroscopy results showed an increase in atomic concentration (AC) of oxygen while the AC of carbon decreased following the exposure of the film to an O2 remote plasma. The results indicate that methyl groups (-CH3) in the top layers of the film are being replaced by hydroxyl (-OH) groups and Si-O-Si bonding. The N1s spectrum showed the formation of an ammonium fluorosilicate (NH4)2SiF6-based surface-modified layer following exposure to a CF4/NH3/Ar remote plasma. IR annealing of the film showed desorption of the ammonium fluorosilicate surface-modified layer and the return to an as grown SiCO film surface composition.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":" 35","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141372573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Pokhrel, Joseph Anthony Duncan, Bryson Krause, T. B. Hoang, S. D. Pollard
Tungsten disulfide (WS2) is a promising two-dimensional material owing to its remarkable optical, electronic, and electrocatalytic behavior. However, morphology of this material varies significantly with growth conditions. In this work, we use salt-assisted low-pressure chemical vapor deposition (LP-CVD) to grow WS2 crystals of a few layers reaching over 50 μm in size on SiO2/Si substrates. We observe a transition from large, dendritic to triangular growth by systematically varying the amount of the NaCl promotor material as well as the presence of intermediate Wx+ states for low NaCl amounts. The transition from dendritic to triangular growth is discussed in the context of diffusion limited aggregation, with the transformation likely being the result of reduced formation energy, owing to increasing concentrations of transition metal oxyhalides for given precursor quantities. These results help to clarify the role of effects of the NaCl precursor in salt-assisted LP-CVD of WS2 and provide a new means to tune the morphology of this material.
{"title":"Transformation from dendritic to triangular growth of WS2 via NaCl assisted low-pressure chemical vapor deposition","authors":"H. Pokhrel, Joseph Anthony Duncan, Bryson Krause, T. B. Hoang, S. D. Pollard","doi":"10.1116/6.0003543","DOIUrl":"https://doi.org/10.1116/6.0003543","url":null,"abstract":"Tungsten disulfide (WS2) is a promising two-dimensional material owing to its remarkable optical, electronic, and electrocatalytic behavior. However, morphology of this material varies significantly with growth conditions. In this work, we use salt-assisted low-pressure chemical vapor deposition (LP-CVD) to grow WS2 crystals of a few layers reaching over 50 μm in size on SiO2/Si substrates. We observe a transition from large, dendritic to triangular growth by systematically varying the amount of the NaCl promotor material as well as the presence of intermediate Wx+ states for low NaCl amounts. The transition from dendritic to triangular growth is discussed in the context of diffusion limited aggregation, with the transformation likely being the result of reduced formation energy, owing to increasing concentrations of transition metal oxyhalides for given precursor quantities. These results help to clarify the role of effects of the NaCl precursor in salt-assisted LP-CVD of WS2 and provide a new means to tune the morphology of this material.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":" 0","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141372250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Qihang Li, Jinping Luo, Zaoyang Li, M. Rummeli, Lijun Liu
Chemical vapor deposition is an affordable method for producing high-quality graphene. Microscopic defects in graphene grown on copper substrates, such as five- and seven-membered rings, degrade the quality of graphene. Therefore, it is essential to study the growth process and factors affecting the quality of graphene on copper surfaces. In this study, first-principles calculations based on density functional theory show that the four-step dehydrogenation reaction of methane is endothermic, with the energy barrier for the last dehydrogenation step being relatively high. Additionally, CH forms dimers on the copper surface with a lower energy barrier and trimers with a higher energy barrier, indicating that carbon dimers are the primary precursor species for graphene growth in the early stages. Subsequently, in molecular dynamics simulations, the analytical bond-order potential based on quantum mechanics is employed. The results reveal that the growth of graphene on the copper surface involves the diffusion and gradual nucleation of carbon dimers in the early stages, the gradual enlargement of graphene domains in the intermediate stages, and the gradual merging of graphene domain boundaries in the later stages. Moreover, the growth of graphene on the copper substrate follows a self-limiting growth mode. Increasing the deposition interval of carbon atoms and reducing the carbon atom deposition velocity contribute to enhancing the quality of graphene grown on the copper substrate.
{"title":"Density functional theory and molecular dynamics study on the growth of graphene by chemical vapor deposition on copper substrate","authors":"Qihang Li, Jinping Luo, Zaoyang Li, M. Rummeli, Lijun Liu","doi":"10.1116/6.0003667","DOIUrl":"https://doi.org/10.1116/6.0003667","url":null,"abstract":"Chemical vapor deposition is an affordable method for producing high-quality graphene. Microscopic defects in graphene grown on copper substrates, such as five- and seven-membered rings, degrade the quality of graphene. Therefore, it is essential to study the growth process and factors affecting the quality of graphene on copper surfaces. In this study, first-principles calculations based on density functional theory show that the four-step dehydrogenation reaction of methane is endothermic, with the energy barrier for the last dehydrogenation step being relatively high. Additionally, CH forms dimers on the copper surface with a lower energy barrier and trimers with a higher energy barrier, indicating that carbon dimers are the primary precursor species for graphene growth in the early stages. Subsequently, in molecular dynamics simulations, the analytical bond-order potential based on quantum mechanics is employed. The results reveal that the growth of graphene on the copper surface involves the diffusion and gradual nucleation of carbon dimers in the early stages, the gradual enlargement of graphene domains in the intermediate stages, and the gradual merging of graphene domain boundaries in the later stages. Moreover, the growth of graphene on the copper substrate follows a self-limiting growth mode. Increasing the deposition interval of carbon atoms and reducing the carbon atom deposition velocity contribute to enhancing the quality of graphene grown on the copper substrate.","PeriodicalId":170900,"journal":{"name":"Journal of Vacuum Science & Technology A","volume":"47 38","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141384502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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