Pressure Chemical Vapor Deposition Process Research Articles

Improvement of warpage and leakage for 3D NAND flash memory

GLS (Gate line split) filling is a very important process in 3D NAND flash memory (3D NAND) fabrication. Filling materials in the GLS should have threefold properties, such as warpage tunability, leakage-free and low resistance. In this paper, the effects of different GLS filling materials (SiO2, W, amorphous silicon: A-Si) on F-attack, warpage and resistance were studied. GLS filled with A-Si shows best performance on warpage and F-attack. For 3D NAND, the number of stacked layers is predicted as a function of the wafer warpage, and the wafer warpage difference between GLS filled with A-Si and W was compared. With the same number of stacking layers, the wafer warpage post GLS filled with A-Si is smaller than that filled with W. Meanwhile, A-Si is produced by the decomposition of SiH4 by low pressure chemical vapor deposition (LPCVD) process, F-related by-product in the GLS filling material and consequent ACS (array common source) to WL (Word line) leakage by F-attack are avoided. A-Si is the best choice for GLS filling. This work provides an efficient method to solve the warpage and leakage problem in 3D NAND flash memory fabrication.

Simulation and optimization of polysilicon thin film deposition in a 3000 mm tubular LPCVD reactor

The high photoelectric conversion efficiency of tunnel oxide passivating contacts (TOPCon) photovoltaic (PV) cells and their process compatibility are increasingly recognized by the industry, making it of growing importance to develop deposition process technologies for high-capacity polysilicon thin films. Currently, the size of LPCVD reactors for preparing polysilicon thin films in the industry is getting enlarged, which directly leads to the degradation of axial uniformity of polysilicon thin films. In this paper, a coupled multi-physics field model is established to simulate the polysilicon thin-film Low Pressure Chemical Vapor Deposition (LPCVD) process based on COMSOL Multiphysics platform, and the validity of the model is verified by comparing experimental data with simulation results. By investigating the flow field, thermal field, chemical reaction field and surface reaction field, the effects of the process parameters such as chamber temperature and pressure are investigated, as well as characteristics of the polysilicon thin films deposition. The results show that the uniformity of thin films decreases with increasing temperature and pressure, and the deposition rate of thin films increases as temperature and pressure increase. With the help of optimized the process parameters, the deposition rate of polysilicon thin films was increased by 13.0% and the uniformity of thin films was controlled above 96%. The uniformity of the films can be further improved to 96.7% by optimizing the temperature zone parameters and adopting the wafers placement strategy.

Wafer-Scale Production of Transition Metal Dichalcogenides and Alloy Monolayers by Nanocrystal Conversion for Large-Scale Ultrathin Flexible Electronics.

Two-dimensional (2D) transition metal dichalcogenide (TMD) layers are unit-cell thick materials with tunable physical properties according to their size, morphology, and chemical composition. Their transition of lab-scale research to industrial-scale applications requires process development for the wafer-scale growth and scalable device fabrication. Herein, we report on a new type of atmospheric pressure chemical vapor deposition (APCVD) process that utilizes colloidal nanoparticles as process-scalable precursors for the wafer-scale production of TMD monolayers. Facile uniform distribution of nanoparticle precursors on the entire substrate leads to the wafer-scale uniform synthesis of TMD monolayers with the controlled size and morphology. Composition-controlled TMD alloy monolayers with tunable bandgaps can be produced by simply mixing dual nanoparticle precursor solutions in the desired ratio. We also demonstrate the fabrication of ultrathin field-effect transistors and flexible electronics with uniformly controlled performance by using TMD monolayers.

CVD Synthesis of 3D-Shaped 3D Graphene Using a 3D-Printed Nickel-PLGA Catalyst Precursor.

Earlier, various attempts to develop graphene structures using chemical and nonchemical routes were reported. Being efficient, scalable, and repeatable, 3D printing of graphene-based polymer inks and aerogels seems attractive; however, the produced structures highly rely on a binder or an ice support to stay intact. The presence of a binder or graphene oxide hinders the translation of the excellent graphene properties to the 3D structure. In this communication, we report our efforts to synthesize a 3D-shaped 3D graphene (3D2G) with good quality, desirable shape, and structure control by combining 3D printing with the atmospheric pressure chemical vapor deposition (CVD) process. Direct ink writing has been used in this work as a 3D-printing technique to print nickel powder–PLGA slurry into various shapes. The latter has been employed as a catalyst for graphene growth via CVD. Porous 3D2G with high purity was obtained after etching out the nickel substrate. The conducted micro CT and 2D Raman study of pristine 3D2G revealed important features of this new material. The interconnected porous nature of the obtained 3D2G combined with its good electrical conductivity (about 17 S/cm) and promising electrochemical properties invites applications for energy storage electrodes, where fast electron transfer and intimate contact with the active material and with the electrolyte are critically important. By changing the printing design, one can manipulate the electrical, electrochemical, and mechanical properties, including the structural porosity, without any requirement for additional doping or chemical postprocessing. The obtained binder-free 3D2G showed a very good thermal stability, tested by thermo-gravimetric analysis in air up to 500 °C. This work brings together two advanced manufacturing approaches, CVD and 3D printing, thus enabling the synthesis of high-quality, binder-free 3D2G structures with a tailored design that appeared to be suitable for multiple applications.

MoSe2 monolayer crystallinity improvement and phase engineering for ultrasensitive SERS detection

Alkali metal halides (AMHs) interaction with metal oxide precursors has been demonstrated to be an exciting and reliable method in the deposition of several atomically thin layered materials since the reaction rate is considerably enhanced. Using three different AMHs (KBr, NaCl, and KCl), we assisted the synthesis of MoSe2 monolayers (MLs) in the atmospheric pressure chemical vapor deposition (APCVD) process in demonstrating that it is possible to improve the crystallinity of the MoSe2 flakes and to induce the formation of 1T domains in the 2H MoSe2 lattice that can be used to perform ultrahigh sensitive surface-enhanced Raman spectroscopy (SERS) detection. We observed that even though NaCl promotes the growth of large-sized MoSe2 MLs, we found critical photoluminescence (PL) quenching originated from forming a Na-O layer underneath the MoSe2 crystals. On the other hand, resonant Raman measurements show a prominent peak around 255 cm−1 only in KBr-MoSe2 single crystals originated from a double-resonant Raman process involving the ZA acoustic phonon and the C exciton, indicating optoelectronic-grade crystalline quality, thus explicating the higher PL emission in comparison with the other two AMH-assisted samples. KCl-MoSe2 X-ray photoelectron spectroscopy (XPS) and Raman spectra display features matching the structural properties of 1T-MoSe2 polyphase, confirming the existence of 1T domains embedded in the 2H-MoSe2 lattice. Moreover, thermogravimetric analysis (TGA) measurements show that the KCl-MoO2 mixture induces different sublimation processes compared with pure MoO2, probably producing potassium-rich eutectic compounds that could stabilize the 1T-MoSe2 domains. Finally, we demonstrate that the 1T-2H MoSe2 monolayers synthesized at 750 °C showed a significant surface enhance Raman scattering activity towards the Rhodamine 6G and Methylene blue, with a detection limit comparable with plasmonic surfaces.

Phosphorus-doped polysilicon passivating contacts deposited by atmospheric pressure chemical vapor deposition

In this work, we present a high quality tunnel oxide passivating, electron-selective contact that is formed using an in-situ phosphorus-doped polycrystalline silicon (poly-Si) layer deposited using an in-line atmospheric pressure chemical vapor deposition (APCVD) process. In-line APCVD is a single-sided deposition process that does not require vacuum systems and is well suited for high volume manufacturing. To fabricate this tunnel oxide passivating contact (TOPCon), we deposit an amorphous silicon (a-Si) layer on silicon oxide (SiO) passivated n-type crystalline silicon (c-Si) followed by an annealing step at around 910 ∘C, which provides solid phase crystallization. The contact shows an excellent surface passivation quality with an effective minority carrier lifetime of ≈4.2 ms and an implied open circuit voltage (iV ) of ≈717 mV after annealing without any additional hydrogenation process. Saturation current density (J ) of ≈18 fA cm−2 is recorded for this contact. Contact resistivity () of ≈50 mΩ·cm−2 and junction resistivity of ≈0.24 Ω·cm−2 are realized with e-beam evaporated aluminium (Al) metal contact.

Structural and Mechanical Analysis of APCVD Deposited Diamond-Like Carbon Thin Films

In this study, diamond-like Carbon (DLC) thin film coatings are deposited by atmospheric pressure chemical vapour deposition (APCVD) process by using C2H2 and H2 as precursor gases on SiO2 substrates. The morphological, structural, mechanical and composition of the DLC thin film coatings are studied by using field emission scanning electron microscopy (FESEM), Raman spectroscopy, nanoindentation, Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Irrespective of the varying H2 flow rate, smooth surfaces of the thin film coatings are observed in the FESEM images. The Young’s modulus (E) and hardness (H) of the DLC coating increases with an increase in H2 flow rate and the maximum E and H are observed as 193.97 GPa and 22.46 GPa respectively. Due to the SiO2 buffer layer, the residual stress (σ) of the film significantly decreased to a minimum of 1.05 GPa which is much less as compared to the DLC film deposited over the Si substrate. The percentage of sp3 can be calculated from the XPS and it is 58.68% and 70% for the flow rate of H2 of 0 and 80 sccm respectively. The effect of H2 flow rate on the morphology, structural, mechanical and composition of the DLC thin film coatings are analyzed and discussed thoroughly along with mechanics behind it.

Fluid-Guided CVD Growth for Large-Scale Monolayer Two-Dimensional Materials.

Atmospheric pressure chemical vapor deposition (APCVD) has been used extensively for synthesizing two-dimensional (2D) materials because of its low cost and promise for high-quality monolayer crystal synthesis. However, the understanding of the reaction mechanism and the key parameters affecting the APCVD processes is still in its embryonic stage. Hence, the scalability of the APCVD method in achieving large-scale continuous film remains very poor. Here, we use MoSe2 as a model system and present a fluid guided growth strategy for understanding and controlling the growth of 2D materials. Through the integration of experiment and computational fluid dynamics (CFD) analysis in the full-reactor scale, we identified three key parameters, precursor mixing, fluid velocity, and shear stress, which play a critical role in the APCVD process. By modifying the geometry of the growth setup to enhance precursor mixing and decrease nearby velocity shear rate and adjusting flow direction, we have successfully obtained inch-scale monolayer MoSe2. This unprecedented success of achieving scalable 2D materials through fluidic design lays the foundation for designing new CVD systems to achieve the scalable synthesis of nanomaterials.

Effect of Bipolar Charging of SiH4 on the Growth Rate and Crystallinity of Silicon Films Grown in the Atmospheric Pressure Chemical Vapor Deposition Process

Increasing the growth rate of thin films and enhancing the film quality have been an issue in the semiconductor manufacturing process. To improve those properties, conventionally the deposition temperature in reactor was increased or a catalyst was added to decompose precursors at low temperature. Here, a new technology utilizing a bipolar carbon fiber ionizer (CFI) was used to achieve a high growth rate and quality of silicon films. The deposition behavior of atmospheric pressure chemical vapor deposition silicon films deposited with and without the bipolar CFI system was compared. The growth rate of silicon films deposited at 450 °C, 500 °C, 700 °C, 900 °C and 1100 °C with the bipolar CFI system was 3.4, 5.6, 3.2, 3.3 and 1.3 times higher than deposited silicon film without the bipolar CFI system. The bipolar CFI system could also improve the crystallinity of the silicon film deposited at 900 °C.

Numerical model of carbon chemical vapor deposition at internal surfaces

The objective of this study is to obtain the rate of Carbon deposition by low pressure chemical vapor deposition process (LPCVD) at internal surfaces to verify that large aspect ratio features can be filled. The mathematical model of LPCVD from reactor-scale to millimeter-scale channels is developed by using Computational Fluid Dynamics software ANSYS/FLUENT. To mimic voids in fibers’ structure, the CVD rate is obtained along each drilled channel in the parallelepiped sample hanged along the reactor axis. The role of heating of feedstock gas in reactor is discussed. Numerical modeling shows that vortices are generated near entrances of each channel. These vortices partially block the flow of feedstock gas from entering into the channel. Because of higher growth rate of carbon near the entrances of channels and partial blockage of the flow toward the centers of channels, the centers of channels have less exposure to CVD reactants; therefore, the channels can be blocked before completion of CVD that might create voids in CVD-manufactured materials.

Microring resonators on a suspended membrane circuit for atom–light interactions

We describe the design and fabrication of a scalable atom-light photonic interface based on a silicon nitride microring resonator on a transparent silicon dioxide-nitride multi-layer membrane. This new photonic platform is fully compatible with freespace cold atom laser cooling, stable trapping, and sorting at around $100~$nm from the microring surface, permitting the formation of an organized, strongly interacting atom-photonic hybrid lattice. We demonstrate small radius ($R\sim$16$\mu$m) microring and racetrack resonators with a high quality factor $Q=3.2\times 10^5$, projecting a single atom cooperativity parameter of $C=25$ and a vacuum Rabi frequency of $2g= 2\pi\times 340~$MHz for trapped cesium atoms interacting with a microring resonator mode. We show that the quality factor is currently limited by the surface roughness of the multi-layer membrane, grown using low pressure chemical vapor deposition (LPCVD) processes. We discuss possible further improvements to a quality factor above $Q>5\times10^6$, potentially achieving single atom cooperativity parameter of $C > 500$ for strong single atom-photon coupling.

Development of Bifacial n‐Type Front‐and‐Back Contact Cells with Phosphorus Back Surface Field via Mask‐Free Approaches

Industrial bifacial n‐type front‐and‐back contact (nFAB) solar cells consist of a boron‐doped p+ emitter and a phosphorus‐doped n+ back surface field (BSF). A conventional BSF formation method with tube‐based POCl3 diffusion typically requires the use of a masking layer to protect the front emitter against cross doping or two wet‐chemical etching steps. Herein, two alternative mask‐free BSF formation approaches are investigated, either via phosphorus ion implantation or atmospheric pressure chemical vapor deposition (APCVD) of phosphosilicate glass (PSG). The fabricated cells indicate comparable efficiencies achievable by mask‐free methods, as compared with conventional tube‐based POCl3 diffusion. In addition, the APCVD process is further improved by optimizing the phosphorus contents in the PSG layer. Cell performances with different phosphorus contents and thus different BSF sheet resistances are studied. A lower phosphorus content (higher BSF's sheet resistance) improves cells' Jsc, whereas a higher phosphorous content results in high fill factor (FF) due to better rear contact resistance and low BSF sheet resistance. The optimized condition results in nFAB cell with a peak efficiency of 21.4% and FF values over 81.0%.

Microstructure, mechanical properties and cutting performances of TiSiCN super-hard nanocomposite coatings deposited using CVD method under the guidance of thermodynamic calculations

A general strategy for the development of TiSiCN super-hard nanocomposite coatings was proposed in the present work. Subsequently, TiSiCN coatings with promising industrial applications for cutting tools were prepared from gaseous mixtures of TiCl4, SiCl4, CH3CN, NH3/N2 and H2 by a low pressure chemical vapor deposition (CVD) process under the guidance of established phase diagrams. The chemical compositions, microstructure, mechanical properties and cutting performances of TiSiCN coatings were investigated. No Si was doped into MT (moderate temperature)-Ti(C,N) with N2 addition while higher Si contents (2.87–6.43 at.%) were obtained by using NH3. The measured compositions and phase assemblages of TiSiCN coatings were reasonably described by thermodynamic calculations. TiSiCN coatings showed nanocomposite structures consisting of nanocrystalline TiCxNy and amorphous SiCxNy. A maximum hardness (44.9 ± 0.9 GPa), ratios of H/E⁎ and H3/E⁎2 (H-hardness, E*-effective elastic modulus) were obtained for TiSiCN coating with a Si content of 2.87 at.% and a grain size of 37.7 nm, indicating enhanced mechanical properties to those of the previous works. TiSiCN displayed a superior cutting performance compared to MT-Ti(C,N) during continuous wet turning of nodular cast iron (DIN GGG40). It also exhibits a better wear resistance than state-of-the-art thicker MT-Ti(C,N) + Al2O3 multilayer coating during dry milling of the same material. TiSiCN coatings with better performances could be designed with the aid of the CVD phase diagrams in this work.

Microstructure and Dielectric Property of 3D BNf/Si3N4 Fabricated by CVI Process

As potential wave-transparent materials applied at high temperatures, 3D BNf/Si3N4 ceramic matrix composites were prepared by low pressure chemical vapor infiltration or deposition (LPCVI/ CVD) process from SiCl4-NH3-H2-Ar gas precursor at 800 °C. The densification process, microstructure and dielectric properties of 3D BNf/Si3N4 composites were investigated. The results indicated that 3D BNf/ Si3N4 was successfully fabricated by LPCVI/CVD, with final open porosity of 2.37% and density of 1.89 g/ cm3. Densification kinetics of 3D BNf/Si3N4 is a typical exponential pattern. The Si3N4 matrix was uniformly infiltrated into porous BNf preform. The deposited Si3N4 matrix was amorphous by XRD analysis. Introduction of BN fiber into Si3N4 ceramic lowered the permittivity of Si3N4. The fabricated BNf/Si3N4 composites possess low permittivity of 3.68 and low dielectric loss of lower than 0.01, which are independent of temperature below 400 °C. Transmission coefficient of BNf/Si3N4 composite is 0.57 and keeps stable below 400 °C. BNf/Si3N4 can be fabricated at low temperature and may be candidates for the microwave transparent materials.

Edge-Epitaxial Growth of Graphene on Cu with a Hydrogen-Free Approach

We demonstrate a new concept of edge-epitaxial growth that enables the van der Waals (vdWs) epitaxial graphene growth on different Cu facets. This approach simply entails turning off hydrogen during the nucleation stage of the atmospheric pressure chemical vapor deposition process. Fundamentally, different from conventional vdWs growth, this new type of epitaxial growth benefits from the strong binding between the graphene edge and a metal step in a hydrogen-absent atmosphere. This interaction fixes the orientation of graphene grains in energetically preferable configurations at the early nucleation stage. Specifically, single-crystal graphene grains grown on Cu(111) have irregular shapes with rough edges and are misaligned slightly with respect to the Cu(111) lattice. Graphene grains form with two possible orientations that are rotated by ∼30° on the Cu(100) surface, and grains with three preferred orientations are observed on Cu(110). Density functional theory calculations further prove the enhanced edg...

Dual Silicon Oxycarbide Accelerated Growth of Well‐Ordered Graphitic Networks for Electronic and Thermal Applications

AbstractWhile effective in circumventing the transfer process of graphene films from metals to insulating substrates, graphene chemical vapor deposition (CVD) methods which grow directly on the surface of insulating substrates suffer from slow growth rates, lack of covalent bonding between both graphene layers within the film and the entire film and its substrate, and the inability to grow films beyond nanoscale thickness. An atmospheric pressure chemical vapor deposition (APCVD) process is described utilizing preplaced silicone rubber and continuously fed tetraethyl orthosilicate (TEOS) as dual silicon oxycarbide (SiOC) sources to facilitate fast surface coverage (30 s) and z‐thickness growth (136 nm min−1) of graphitic coatings consisting of a network of covalently bonded graphene layers directly on quartz while providing strong adhesion between the coating and the substrate via a semiconductive transition layer. This process can produce graphitic networks for a wide range of products including transparent conducting and semiconductive nanoscale graphene films, anisotropic micrometer‐scale coatings with in‐plane thermal conductivity >1000 W m−1 K−1 and standalone flakes with >40 µm thickness for thermal management applications.

Mechanical properties and oxidation resistance of chemically vapor deposited TiSiN nanocomposite coating with thermodynamically designed compositions

TiSiN coating with nanocrystallite surrounded by amorphous phase has attracted a broad interest because of its high hardness and excellent oxidation resistance desired for cutting tools. In the present work, TiSiN coatings were designed and prepared from a gaseous mixture of TiCl4, SiCl4, NH3 and H2 by low pressure chemical vapor deposition (CVD) process under the guidance of calculated CVD phase diagrams. The calculated compositions and phases in the deposited coatings agree well with the experimental ones. The deposited TiSiN coatings consist of nano-crystalline TiN and amorphous Si3N4 (a-Si3N4). A maximum hardness of about 2800 HV0.02 was obtained, corresponding to a minimum crystallite size of 17.7 nm and a-Si3N4 volume fraction of 13.3% for TiSiN coating deposited at 1123 K under 3.0 kPa. After oxidation at 973 K for 1 h, TiSiN coating kept intact while TiN was completely oxidized. TiSiN nanocomposite coating formed by Si incorporation to TiN displayed superior hardness and oxidation resistance in comparison with those of TiN. The correlation of TiSiN coating hardness with volume fraction of a-Si3N4 and TiN grain size was discussed. The present work demonstrates a novel strategy of thermodynamic calculations and key experiments to deposit CVD TiSiN coatings highly efficiently, which is equally valid for the design of other CVD hard coatings.

Impact of the manufacturing process on the reverse-bias characteristics of high-efficiency n-type bifacial silicon wafer solar cells

In this paper, bifacial n-type silicon wafer solar cells with a front boron-diffused emitter and a rear phosphorus-diffused back surface field are investigated. The cell structure is abbreviated as nFAB (n-type Front and Back Contact). Three different process flows are evaluated for the fabrication of nFAB cells: (1) process flow with a silicon nitride diffusion mask deposited by plasma-enhanced chemical vapour deposition (PECVD), (2) process flow with a silicon oxynitride diffusion mask also deposited by PECVD, and (3) process flow using single-sided atmospheric pressure chemical vapour deposition (APCVD), without diffusion masks. An average batch efficiency of 21.3% was measured (front side illumination only) for all three nFAB process flows. However, the reverse bias I-V characteristics are observed to be remarkably different and dependent on the process flow, especially with regards to the masking processes. For process flow 1 that uses a silicon nitride PECVD mask, the reverse bias I-V characteristics are poor with a severe breakdown occurring at − 5 V and a reverse current of 18 A at −10 V. Process flow 2 with a silicon oxynitride PECVD mask leads to significantly improved reverse characteristics with a reverse current of 1 A at −10 V. For the APCVD process flow without diffusion masks, excellent reverse bias characteristics are observed with a reverse current of only 3 mA at −10 V. Reverse-biased electroluminescence imaging is used to determine the breakdown regions of the cells for the different process flows and to analyse the impact of the diffusion masking step on the cells’ breakdown characteristics.

Enhanced photoresponse of Ge/Si nanostructures by combining amorphous silicon deposition and annealing

In order to inhibit high carrier recombination rates in Ge-on-Si nanostructures, GexSi1–x nanoislands were covered by a thin amorphous silicon layer via a low pressure CVD process. It is demonstrated that the surface photovoltage (SPV) signal in capped GexSi1–x/Si is increased by an order of magnitude compared to that of bare GexSi1–x islands, which can be due to the effective passivation of recombination centers at the a-Si/GexSi1–x interface. The effect is even more enhanced after subsequent annealing at 400 °C in an O2 ambient environment, with the signal increases ranging from 5 to 10 times. The observed increased photovoltage is accompanied by longer time decays in the SPV transients, being most increased after the annealing step. These results show that the photoexcited electron-hole pairs can be efficiently separated by the internal electric field at the a-Si/GexSi1–x/c-Si interfaces and can contribute to the photovoltage with decreasing recombination in GexSi1–x islands or at the interfaces. This work can facilitate the photovoltaic applications of Ge/Si heterostructures.

Conformal coating of amorphous silicon and germanium by high pressure chemical vapor deposition for photovoltaic fabrics

Conformally coating textured, high surface area substrates with high quality semiconductors is challenging. Here, we show that a high pressure chemical vapor deposition process can be employed to conformally coat the individual fibers of several types of flexible fabrics (cotton, carbon, steel) with electronically or optoelectronically active materials. The high pressure (∼30 MPa) significantly increases the deposition rate at low temperatures. As a result, it becomes possible to deposit technologically important hydrogenated amorphous silicon (a-Si:H) from silane by a simple and very practical pyrolysis process without the use of plasma, photochemical, hot-wire, or other forms of activation. By confining gas phase reactions in microscale reactors, we show that the formation of undesired particles is inhibited within the microscale spaces between the individual wires in the fabric structures. Such a conformal coating approach enables the direct fabrication of hydrogenated amorphous silicon-based Schottky ...