Nobuya Miyoshi, Kazunori Shinoda, Hiroyuki Kobayashi, M. Kurihara, Yutaka Kouzuma, M. Izawa
Atomic layer etching (ALE) is usually classified into ion-driven anisotropic etching or thermally driven isotropic etching. In this work, we present a thermal ALE process for Si3N4 with high selectivity to SiO2 and poly-Si. This ALE process consists of exposure to a CH2F2/O2/Ar downstream plasma to form an (NH4)2SiF6-based surface-modified layer, followed by infrared (IR) annealing to remove the modified layer. CH2F2-based chemistry was adopted to achieve high selectivity to SiO2 and poly-Si. This chemistry was expected to reduce the number density of F atoms (radicals), which contributes to decreasing the etching rate of SiO2 and poly-Si films. X-ray photoelectron spectroscopy analysis confirmed the formation of an (NH4)2SiF6-based modified layer on the surface of the Si3N4 after exposure to the plasma and subsequent removal of the modified layer using IR annealing. An in situ ellipsometry measurement revealed that the etch per cycle of the ALE process saturated with respect to the radical exposure time at 0.9 nm/cycle, demonstrating the self-limiting nature of this etching process. In addition, no etching was observed on SiO2 and poly-Si films, successfully demonstrating the high selectivity of this ALE process. This high selectivity to SiO2 and poly-Si is attributed to the fact that the spontaneous etching rates of these films are negligibly small and that there is no surface reaction to etch these films during the IR annealing step.
{"title":"Atomic layer etching of Si3N4 with high selectivity to SiO2 and poly-Si","authors":"Nobuya Miyoshi, Kazunori Shinoda, Hiroyuki Kobayashi, M. Kurihara, Yutaka Kouzuma, M. Izawa","doi":"10.1116/6.0001179","DOIUrl":"https://doi.org/10.1116/6.0001179","url":null,"abstract":"Atomic layer etching (ALE) is usually classified into ion-driven anisotropic etching or thermally driven isotropic etching. In this work, we present a thermal ALE process for Si3N4 with high selectivity to SiO2 and poly-Si. This ALE process consists of exposure to a CH2F2/O2/Ar downstream plasma to form an (NH4)2SiF6-based surface-modified layer, followed by infrared (IR) annealing to remove the modified layer. CH2F2-based chemistry was adopted to achieve high selectivity to SiO2 and poly-Si. This chemistry was expected to reduce the number density of F atoms (radicals), which contributes to decreasing the etching rate of SiO2 and poly-Si films. X-ray photoelectron spectroscopy analysis confirmed the formation of an (NH4)2SiF6-based modified layer on the surface of the Si3N4 after exposure to the plasma and subsequent removal of the modified layer using IR annealing. An in situ ellipsometry measurement revealed that the etch per cycle of the ALE process saturated with respect to the radical exposure time at 0.9 nm/cycle, demonstrating the self-limiting nature of this etching process. In addition, no etching was observed on SiO2 and poly-Si films, successfully demonstrating the high selectivity of this ALE process. This high selectivity to SiO2 and poly-Si is attributed to the fact that the spontaneous etching rates of these films are negligibly small and that there is no surface reaction to etch these films during the IR annealing step.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"50 1","pages":"052601"},"PeriodicalIF":0.0,"publicationDate":"2021-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81405107","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}
Abdulrahman H. Basher, M. Krstić, K. Fink, Tomoko Ito, K. Karahashi, W. Wenzel, S. Hamaguchi
{"title":"Erratum: “Formation and desorption of nickel hexafluoroacetylacetonate Ni(hfac)2 on a nickel oxide surface in atomic layer etching processes” [J. Vac. Sci. Technol. A 38, 052602 (2020)]","authors":"Abdulrahman H. Basher, M. Krstić, K. Fink, Tomoko Ito, K. Karahashi, W. Wenzel, S. Hamaguchi","doi":"10.1116/6.0001319","DOIUrl":"https://doi.org/10.1116/6.0001319","url":null,"abstract":"","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"13 1","pages":"057001"},"PeriodicalIF":0.0,"publicationDate":"2021-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77891440","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}
C. Frye, S. Donald, C. Reinhardt, L. Voss, S. Harrison
The choice of carrier wafer was found to significantly influence etch rates, selectivity, and morphology in GaN micropillar etching in a Cl2-Ar high-density inductively coupled plasma. 7 × 7 mm2 GaN on sapphire chips with a plasma-enhanced chemical vapor deposition SiO2 hard mask was etched on top of 4-in. fused silica, silicon carbide, silicon, sapphire, aluminum nitride, and high purity aluminum carriers. Silicon and silicon carbide carriers reduced GaN:SiO2 selectivity because incidental SiClx and CClx etch products from the carriers attack the SiO2 mask. Aluminum nitride and high-purity aluminum carriers yielded the highest GaN:SiO2 selectivities due to the deposition of Al-based etched by-products, while the highest GaN etch rate was achieved using the sapphire carrier since it was the most inert carrier and did not sink any Cl2. Results indicate that SiO2 and Al may be used as passivation materials during GaN etching, as vertical profiles were achieved when SiO2 or Al is redeposited from the fused silica and aluminum carriers, respectively. Floor pitting, trenching, sidewall roughness, and faceting were all influenced by carrier wafer type and will be discussed.
{"title":"Impact of carrier wafer on etch rate, selectivity, morphology, and passivation during GaN plasma etching","authors":"C. Frye, S. Donald, C. Reinhardt, L. Voss, S. Harrison","doi":"10.1116/6.0001123","DOIUrl":"https://doi.org/10.1116/6.0001123","url":null,"abstract":"The choice of carrier wafer was found to significantly influence etch rates, selectivity, and morphology in GaN micropillar etching in a Cl2-Ar high-density inductively coupled plasma. 7 × 7 mm2 GaN on sapphire chips with a plasma-enhanced chemical vapor deposition SiO2 hard mask was etched on top of 4-in. fused silica, silicon carbide, silicon, sapphire, aluminum nitride, and high purity aluminum carriers. Silicon and silicon carbide carriers reduced GaN:SiO2 selectivity because incidental SiClx and CClx etch products from the carriers attack the SiO2 mask. Aluminum nitride and high-purity aluminum carriers yielded the highest GaN:SiO2 selectivities due to the deposition of Al-based etched by-products, while the highest GaN etch rate was achieved using the sapphire carrier since it was the most inert carrier and did not sink any Cl2. Results indicate that SiO2 and Al may be used as passivation materials during GaN etching, as vertical profiles were achieved when SiO2 or Al is redeposited from the fused silica and aluminum carriers, respectively. Floor pitting, trenching, sidewall roughness, and faceting were all influenced by carrier wafer type and will be discussed.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"113 1","pages":"053002"},"PeriodicalIF":0.0,"publicationDate":"2021-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90667382","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 energy distributions of secondary ions for the ion beam sputtering of a Ga 2O 3 target using O 2+ and Ar + ions are measured in dependence on various process parameters using energy-selective mass spectrometry. The process parameters include sputtering geometry (ion incidence angle α, polar emission angle β, scattering angle γ), the energy of incident ions Eion, and the background pressure of O 2. The main secondary ion species are identified to be Ga +, O +, O 2+, and, when argon is used as a process gas, Ar +. The changes in the sputtering geometry and the primary ion energy have the most impact on the energy distributions of secondary Ga + and O + ions, giving control over the high-energy tail, which is attributed to anisotropy effects in sputtering. The formation of O 2+ ions is attributed to collisions with background gas molecules, as their energy distributions are not influenced by the sputtering geometry or the primary ion energy. The increase of the O 2 pressure leads to a minor decrease of the energy of Ga + ions due to collisions with the background gas particles. The use of primary Ar + ions with O 2 background pressure does not show any specific effect on energy distributions of Ga +, O +, and O 2+ ions except for the case without additional O 2 background. In the latter case, much fewer O + and O 2+ ions are produced indicative of oxygen depletion of the surface due to preferential sputtering of oxygen. At all considered O 2 pressures, the energy distributions of Ar + ions have a high-energy peak, attributed to direct scattering events. The trends in experimental data show qualitative agreement to simulations using the Monte Carlo code SDTrimSP.
{"title":"Properties of secondary ions in ion beam sputtering of Ga2O3","authors":"D. Kalanov, A. Anders, C. Bundesmann","doi":"10.1116/6.0001204","DOIUrl":"https://doi.org/10.1116/6.0001204","url":null,"abstract":"The energy distributions of secondary ions for the ion beam sputtering of a Ga 2O 3 target using O 2+ and Ar + ions are measured in dependence on various process parameters using energy-selective mass spectrometry. The process parameters include sputtering geometry (ion incidence angle α, polar emission angle β, scattering angle γ), the energy of incident ions Eion, and the background pressure of O 2. The main secondary ion species are identified to be Ga +, O +, O 2+, and, when argon is used as a process gas, Ar +. The changes in the sputtering geometry and the primary ion energy have the most impact on the energy distributions of secondary Ga + and O + ions, giving control over the high-energy tail, which is attributed to anisotropy effects in sputtering. The formation of O 2+ ions is attributed to collisions with background gas molecules, as their energy distributions are not influenced by the sputtering geometry or the primary ion energy. The increase of the O 2 pressure leads to a minor decrease of the energy of Ga + ions due to collisions with the background gas particles. The use of primary Ar + ions with O 2 background pressure does not show any specific effect on energy distributions of Ga +, O +, and O 2+ ions except for the case without additional O 2 background. In the latter case, much fewer O + and O 2+ ions are produced indicative of oxygen depletion of the surface due to preferential sputtering of oxygen. At all considered O 2 pressures, the energy distributions of Ar + ions have a high-energy peak, attributed to direct scattering events. The trends in experimental data show qualitative agreement to simulations using the Monte Carlo code SDTrimSP.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"170 1","pages":"053409"},"PeriodicalIF":0.0,"publicationDate":"2021-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88287011","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}
Pavel Shapturenka, P. Gaillard, Lesley Chan, O. Polonskyi, M. Gordon
Hierarchical colloid-based lithography and two-step plasma etching involving mask reduction were used to probe and tune the wettability landscape of Si and GaN surfaces from the hydrophilic to superhydrophobic limits over cm length scales. Hydrophobicity, due to the classical Cassie–Baxter (CB) wetting effect, was observed on Si with surface pillars having pitches below 1 μm. Additional tuning of plasma processing conditions at this critical transition provided additional increases in hydrophobicity and led to a highly repellent, lotus leaf effect. Superhydrophobic surfaces were created within the CB wetting state by varying the extent and duration of plasma-based mask reduction and pattern transfer, achieving a maximum contact angle of 157°. Additional submicrometer topography (310 nm spacing) was added to a nominally Wenzel-impregnated, hydrophilic Si micropillar surface (a diameter of 6 μm) with a second lithography cycle, rendering the surface hydrophobic and robust to aging in ambient conditions. An increase in the contact angle with added hierarchy (46°–88°) was also observed for GaN surfaces, albeit diminished compared to Si owing to the relatively lower initial GaN-water contact angle. Overall, this approach has demonstrated a significant degree of wetting tunability in multiple semiconductor systems using colloidal-based nano- and micro-patterning.
{"title":"Hierarchical colloid-based lithography for wettability tuning of semiconductor surfaces","authors":"Pavel Shapturenka, P. Gaillard, Lesley Chan, O. Polonskyi, M. Gordon","doi":"10.1116/6.0001122","DOIUrl":"https://doi.org/10.1116/6.0001122","url":null,"abstract":"Hierarchical colloid-based lithography and two-step plasma etching involving mask reduction were used to probe and tune the wettability landscape of Si and GaN surfaces from the hydrophilic to superhydrophobic limits over cm length scales. Hydrophobicity, due to the classical Cassie–Baxter (CB) wetting effect, was observed on Si with surface pillars having pitches below 1 μm. Additional tuning of plasma processing conditions at this critical transition provided additional increases in hydrophobicity and led to a highly repellent, lotus leaf effect. Superhydrophobic surfaces were created within the CB wetting state by varying the extent and duration of plasma-based mask reduction and pattern transfer, achieving a maximum contact angle of 157°. Additional submicrometer topography (310 nm spacing) was added to a nominally Wenzel-impregnated, hydrophilic Si micropillar surface (a diameter of 6 μm) with a second lithography cycle, rendering the surface hydrophobic and robust to aging in ambient conditions. An increase in the contact angle with added hierarchy (46°–88°) was also observed for GaN surfaces, albeit diminished compared to Si owing to the relatively lower initial GaN-water contact angle. Overall, this approach has demonstrated a significant degree of wetting tunability in multiple semiconductor systems using colloidal-based nano- and micro-patterning.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"40 1","pages":"053209"},"PeriodicalIF":0.0,"publicationDate":"2021-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85530071","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}
O. Renault, HoKwon Kim, D. Dumcenco, D. Unuchek, N. Chevalier, A. Kis, N. Fairley
Vertical heterostructures of MoS2 and WSe2 layers are studied by spectroscopic photoemission electron microscopy as an effective technique for correlating chemical and electronic states at the micrometer scale. Element-specific, surface-sensitive images recorded at high lateral and energy resolution from core-level photoelectrons using different laboratory excitation sources are postprocessed to obtain laterally resolved maps of elemental composition and energy shifts in the Mo3d spectra of a few hundred meV. For monolayer MoS2, the method reveals substrate-dependent charge transfer properties within the narrow energy range of 360 meV, with MoS2 becoming more n-type after transfer onto WSe2. The band structure data from momentum microscopy taken over the same areas confirm the charge transfer from WSe2 to MoS2 by the shift of the K-bands away from the Fermi level and illustrates the layer-specific contributions to the electronic band structure of the heterostructure. From work function mapping, the reconstructed energy-level diagram reveals a type II heterostructure but with a very small conduction-band offset.
{"title":"Correlating chemical and electronic states from quantitative photoemission electron microscopy of transition-metal dichalcogenide heterostructures","authors":"O. Renault, HoKwon Kim, D. Dumcenco, D. Unuchek, N. Chevalier, A. Kis, N. Fairley","doi":"10.1116/6.0001135","DOIUrl":"https://doi.org/10.1116/6.0001135","url":null,"abstract":"Vertical heterostructures of MoS2 and WSe2 layers are studied by spectroscopic photoemission electron microscopy as an effective technique for correlating chemical and electronic states at the micrometer scale. Element-specific, surface-sensitive images recorded at high lateral and energy resolution from core-level photoelectrons using different laboratory excitation sources are postprocessed to obtain laterally resolved maps of elemental composition and energy shifts in the Mo3d spectra of a few hundred meV. For monolayer MoS2, the method reveals substrate-dependent charge transfer properties within the narrow energy range of 360 meV, with MoS2 becoming more n-type after transfer onto WSe2. The band structure data from momentum microscopy taken over the same areas confirm the charge transfer from WSe2 to MoS2 by the shift of the K-bands away from the Fermi level and illustrates the layer-specific contributions to the electronic band structure of the heterostructure. From work function mapping, the reconstructed energy-level diagram reveals a type II heterostructure but with a very small conduction-band offset.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"22 1","pages":"053210"},"PeriodicalIF":0.0,"publicationDate":"2021-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87940291","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}
Cellulosic nanomaterials can improve the performance of various products and can be renewably sourced. In this study, nanocellulosic paper (nanopapers) is chemically and physically altered with simple gas-phase processing to achieve enhanced mechanical performance. Cellulosic nanofibril paper is exposed to single cycles of trimethylaluminum (TMA) and water to modify the surface and subsurface chemistry with small quantities of aluminum oxide. Precursor exposure times are found to significantly influence the amount of inorganic deposited within the cellulosic structure and its crystallinity. This result differs from the common assumption that exposing cellulose to TMA will lead to an “atomic layer deposition (ALD)” type of process in which self-limited surface saturation is quickly achieved. These results suggest that with extended exposure times, the TMA precursor finds new pathways to chemically or physically alter the cellulosic material. Through the x-ray photoelectron spectroscopy analysis, we find that cellulose undergoes a decomposition process during the TMA exposure and/or subsequent reaction with H2O, creating at least one additional pathway to inorganic uptake. Interestingly, uniaxial tensile strength measurements reveal that longer TMA exposure times significantly increase the nanopaper's elongation at break and ultimate tensile strength, with only a modest loss in Young's modulus. While similar inorganic loading can be achieved with multiple ALD cycles, mechanical toughness exhibits significantly less change than for the increased TMA exposure times. X-ray diffraction suggests that the TMA exposures are transforming crystalline portions of the nanocellulose into amorphous structures. These amorphous regions lead to crazing, which increases the strain to break and toughness of the nanopaper.
{"title":"Impact of trimethylaluminum exposure time on the mechanical properties of single-cycle atomic layer deposition modified cellulosic nanopaper","authors":"Yi Li, M. Losego","doi":"10.1116/6.0001198","DOIUrl":"https://doi.org/10.1116/6.0001198","url":null,"abstract":"Cellulosic nanomaterials can improve the performance of various products and can be renewably sourced. In this study, nanocellulosic paper (nanopapers) is chemically and physically altered with simple gas-phase processing to achieve enhanced mechanical performance. Cellulosic nanofibril paper is exposed to single cycles of trimethylaluminum (TMA) and water to modify the surface and subsurface chemistry with small quantities of aluminum oxide. Precursor exposure times are found to significantly influence the amount of inorganic deposited within the cellulosic structure and its crystallinity. This result differs from the common assumption that exposing cellulose to TMA will lead to an “atomic layer deposition (ALD)” type of process in which self-limited surface saturation is quickly achieved. These results suggest that with extended exposure times, the TMA precursor finds new pathways to chemically or physically alter the cellulosic material. Through the x-ray photoelectron spectroscopy analysis, we find that cellulose undergoes a decomposition process during the TMA exposure and/or subsequent reaction with H2O, creating at least one additional pathway to inorganic uptake. Interestingly, uniaxial tensile strength measurements reveal that longer TMA exposure times significantly increase the nanopaper's elongation at break and ultimate tensile strength, with only a modest loss in Young's modulus. While similar inorganic loading can be achieved with multiple ALD cycles, mechanical toughness exhibits significantly less change than for the increased TMA exposure times. X-ray diffraction suggests that the TMA exposures are transforming crystalline portions of the nanocellulose into amorphous structures. These amorphous regions lead to crazing, which increases the strain to break and toughness of the nanopaper.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"16 1","pages":"052407"},"PeriodicalIF":0.0,"publicationDate":"2021-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81705059","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}
Md. Istiaque Chowdhury, M. Sowa, Kylie E. Van Meter, T. Babuska, Tomas Grejtak, A. Kozen, B. Krick, N. Strandwitz
In this work, TiMoN thin films were deposited by plasma-enhanced atomic layer deposition with an equal number of Ti and Mo precursor exposures at a substrate temperature of 250 °C. Tetrakis(dimethylamido) titanium and bis(tert-butylimido)bis(dimethylamido) molybdenum were used as sources for Ti and Mo, respectively. N2 and N2/H2 plasma were used, respectively, for TiN and MoN cycles as a source for N. Negative RF substrate bias voltage of magnitude, |Vbias|, of 0, 31, 62, 125, and 188 V were applied during the plasma half cycle. Nanocrystalline rock salt crystal structures were found by x-ray diffraction for films deposited on single-crystal Si and Si-thermal oxide substrates. Applying |Vbias| generated voids by the bombardment of high-energy ions, lowering the density. Further increase of |Vbias| caused the annihilation of voids and a slight increase in density. Four-point probe measurement showed increased electrical resistivity due to a reduction in grain size caused by continuous renucleation during growth. High-energy ions at high |Vbias| sputtered away the films resulting in low growth rates. Stripe test revealed inferior wear rates and coefficients of friction at higher |Vbias| due to low-density porous films. Epitaxial films deposited on c-plane sapphire had (111) orientation and considerable mosaicity with twinned domains rotated at 60° to each other.
{"title":"Plasma-enhanced atomic layer deposition of titanium molybdenum nitride: Influence of RF bias and substrate structure","authors":"Md. Istiaque Chowdhury, M. Sowa, Kylie E. Van Meter, T. Babuska, Tomas Grejtak, A. Kozen, B. Krick, N. Strandwitz","doi":"10.1116/6.0001175","DOIUrl":"https://doi.org/10.1116/6.0001175","url":null,"abstract":"In this work, TiMoN thin films were deposited by plasma-enhanced atomic layer deposition with an equal number of Ti and Mo precursor exposures at a substrate temperature of 250 °C. Tetrakis(dimethylamido) titanium and bis(tert-butylimido)bis(dimethylamido) molybdenum were used as sources for Ti and Mo, respectively. N2 and N2/H2 plasma were used, respectively, for TiN and MoN cycles as a source for N. Negative RF substrate bias voltage of magnitude, |Vbias|, of 0, 31, 62, 125, and 188 V were applied during the plasma half cycle. Nanocrystalline rock salt crystal structures were found by x-ray diffraction for films deposited on single-crystal Si and Si-thermal oxide substrates. Applying |Vbias| generated voids by the bombardment of high-energy ions, lowering the density. Further increase of |Vbias| caused the annihilation of voids and a slight increase in density. Four-point probe measurement showed increased electrical resistivity due to a reduction in grain size caused by continuous renucleation during growth. High-energy ions at high |Vbias| sputtered away the films resulting in low growth rates. Stripe test revealed inferior wear rates and coefficients of friction at higher |Vbias| due to low-density porous films. Epitaxial films deposited on c-plane sapphire had (111) orientation and considerable mosaicity with twinned domains rotated at 60° to each other.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"32 1","pages":"053408"},"PeriodicalIF":0.0,"publicationDate":"2021-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90862047","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}
Paul Dill, Florian Pachel, Christian Militzer, A. Held, G. Puchas, Stefan Knohl, W. Krenkel, C. Tegenkamp, W. Goedel
High temperature-resistant fabrics can be used as a reinforcement structure in ceramic matrix composites. They often need a coating for oxidation protection and mechanical decoupling from the matrix. Atomic layer deposition (ALD) provides very thin conformal coatings even deep down into complex or porous structures and thus might be a suitable technique for this purpose. Carbon fiber fabrics (size 300 mm × 80 mm) and SiC fiber fabrics (size 400 mm × 80 mm) were coated using ALD with a multilayer system: a first layer made of 320 cycles of alumina (Al2O3) deposition, a second layer made of 142 cycles of titania-furfuryl alcohol hybrid (TiO2-FFA), and a third layer made of 360 cycles of titanium phosphate (TixPOy). Scanning electron microscopy reveals that the coatings are uniform and that the thickness of each layer is almost independent of the place in the reactor while coating. Appearance and thickness do not show any dependence on the type of fiber used as a substrate. Energy dispersive x-ray spectroscopy confirmed the expected elemental composition of each layer. Thermogravimetric analysis under oxidizing environment revealed that the first layer increases the onset temperature of fiber oxidation significantly, while the following two layers improve the oxidative protection only to a much smaller degree. Varying the geometry and size of the sample holder and especially the stacking of several fabric specimens on top of each other allowed increasing the total area of coated fabric up to 560 cm2 per batch. It was demonstrated that four-layered fiber coatings could be obtained with high uniformity even on these much more complicated geometries.
耐高温织物可作为陶瓷基复合材料的增强结构。它们通常需要一层氧化保护和与基体机械解耦的涂层。原子层沉积(ALD)提供非常薄的适形涂层，甚至深入到复杂或多孔结构中，因此可能是用于此目的的合适技术。碳纤维织物(尺寸为300 mm × 80 mm)和SiC纤维织物(尺寸为400 mm × 80 mm)采用ALD进行多层涂层:第一层由320次氧化铝(Al2O3)沉积制成，第二层由142次钛-糠醇杂化物(TiO2-FFA)制成，第三层由360次磷酸钛(TixPOy)制成。扫描电镜显示，涂层是均匀的，每层的厚度几乎与涂层在反应器中的位置无关。外观和厚度与用作衬底的纤维类型没有任何关系。能量色散x射线光谱学证实了每一层预期的元素组成。氧化环境下的热重分析表明，第一层显著提高了纤维的氧化起始温度，而后两层对纤维的氧化保护作用的提高程度要小得多。改变样品架的几何形状和尺寸，特别是将几个织物样品堆叠在一起，可以将每批涂层织物的总面积增加到560平方厘米。结果表明，即使在这些更复杂的几何形状上，也可以获得高度均匀的四层纤维涂层。
{"title":"Atomic layer deposition onto fabrics of carbon and silicon carbide fibers : Preparation of multilayers comprising alumina, titania-furfuryl alcohol hybrid, and titanium phosphate","authors":"Paul Dill, Florian Pachel, Christian Militzer, A. Held, G. Puchas, Stefan Knohl, W. Krenkel, C. Tegenkamp, W. Goedel","doi":"10.1116/6.0001193","DOIUrl":"https://doi.org/10.1116/6.0001193","url":null,"abstract":"High temperature-resistant fabrics can be used as a reinforcement structure in ceramic matrix composites. They often need a coating for oxidation protection and mechanical decoupling from the matrix. Atomic layer deposition (ALD) provides very thin conformal coatings even deep down into complex or porous structures and thus might be a suitable technique for this purpose. Carbon fiber fabrics (size 300 mm × 80 mm) and SiC fiber fabrics (size 400 mm × 80 mm) were coated using ALD with a multilayer system: a first layer made of 320 cycles of alumina (Al2O3) deposition, a second layer made of 142 cycles of titania-furfuryl alcohol hybrid (TiO2-FFA), and a third layer made of 360 cycles of titanium phosphate (TixPOy). Scanning electron microscopy reveals that the coatings are uniform and that the thickness of each layer is almost independent of the place in the reactor while coating. Appearance and thickness do not show any dependence on the type of fiber used as a substrate. Energy dispersive x-ray spectroscopy confirmed the expected elemental composition of each layer. Thermogravimetric analysis under oxidizing environment revealed that the first layer increases the onset temperature of fiber oxidation significantly, while the following two layers improve the oxidative protection only to a much smaller degree. Varying the geometry and size of the sample holder and especially the stacking of several fabric specimens on top of each other allowed increasing the total area of coated fabric up to 560 cm2 per batch. It was demonstrated that four-layered fiber coatings could be obtained with high uniformity even on these much more complicated geometries.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"15 1","pages":"052406"},"PeriodicalIF":0.0,"publicationDate":"2021-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81826259","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}
Polyamide thin films, designated Nylon 2,6, were grown on flat and particle substrates using molecular layer deposition (MLD) in a custom-built isothermal enclosure containing a rotary reactor. The polyamide films were grown using sequential exposures of ethylene diamine and adipoyl chloride. The reactor and precursors were contained in a fiberglass oven to keep all reactor components at the same temperature. A growth rate of 4.0 A/cycle at 67 °C was determined on flat substrates with ex situ x-ray reflectivity and spectroscopic ellipsometry. The temperature dependence of the Nylon 2,6 displayed a peak growth rate at 67 °C with decreasing growth rates above and below this temperature. X-ray photoelectron spectroscopy of the polyamide film on flat substrates also revealed an elemental composition consistent with the Nylon 2,6 polymer with a small amount of chlorine in the film. The isothermal reactor allowed MLD to be performed consistently on high surface area particles at low temperatures. Transmission electron microscopy (TEM) images showed growth of the Nylon 2,6 films on ZrO2, cellulose, and metformin particles that was consistent with the growth on witness wafers. The growth of the Nylon 2,6 films was also linear versus the number of MLD cycles. The TEM images displayed reproducible MLD growth on particles of varying size and composition. Fourier transform infrared spectroscopy and energy dispersive spectroscopy were consistent with the expected characteristics of the Nylon 2,6 polyamide film. Nylon 2,6 MLD should find application when low-temperature MLD is needed to coat thermally sensitive substrates such as organic films or pharmaceutical powders.
{"title":"Molecular layer deposition of Nylon 2,6 polyamide polymer on flat and particle substrates in an isothermal enclosure containing a rotary reactor","authors":"Tyler J. Myers, S. George","doi":"10.1116/6.0001162","DOIUrl":"https://doi.org/10.1116/6.0001162","url":null,"abstract":"Polyamide thin films, designated Nylon 2,6, were grown on flat and particle substrates using molecular layer deposition (MLD) in a custom-built isothermal enclosure containing a rotary reactor. The polyamide films were grown using sequential exposures of ethylene diamine and adipoyl chloride. The reactor and precursors were contained in a fiberglass oven to keep all reactor components at the same temperature. A growth rate of 4.0 A/cycle at 67 °C was determined on flat substrates with ex situ x-ray reflectivity and spectroscopic ellipsometry. The temperature dependence of the Nylon 2,6 displayed a peak growth rate at 67 °C with decreasing growth rates above and below this temperature. X-ray photoelectron spectroscopy of the polyamide film on flat substrates also revealed an elemental composition consistent with the Nylon 2,6 polymer with a small amount of chlorine in the film. The isothermal reactor allowed MLD to be performed consistently on high surface area particles at low temperatures. Transmission electron microscopy (TEM) images showed growth of the Nylon 2,6 films on ZrO2, cellulose, and metformin particles that was consistent with the growth on witness wafers. The growth of the Nylon 2,6 films was also linear versus the number of MLD cycles. The TEM images displayed reproducible MLD growth on particles of varying size and composition. Fourier transform infrared spectroscopy and energy dispersive spectroscopy were consistent with the expected characteristics of the Nylon 2,6 polyamide film. Nylon 2,6 MLD should find application when low-temperature MLD is needed to coat thermally sensitive substrates such as organic films or pharmaceutical powders.","PeriodicalId":17571,"journal":{"name":"Journal of Vacuum Science and Technology","volume":"62 ","pages":"052405"},"PeriodicalIF":0.0,"publicationDate":"2021-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91455907","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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