Plasma Chemical Vapor Deposition System Research Articles

Strain‐Engineered Unified SiNx Deposition for Device Passivation and Capacitance Dielectric in GaN Monolithic Microwave Integrated Circuit

Silicon nitride (SiNx) is used for device passivation and capacitance dielectric in GaN monolithic microwave integrated circuits. However, this is a conflicting requirement as passivation requires SiNx to cause tensile strain, and capacitance dielectric primarily demands a high breakdown voltage and large dielectric constant for SiNx, leading to a damaged AlGaN surface during deposition. Two independent SiNx depositions under two different conditions (silicon‐ and nitrogen‐rich) are usually carried out to meet both requirements. Herein, a solution for a unified deposition through interfacial strain analysis on an AlGaN/GaN heterostructure grown on 6H‐SiC imposed by thin film silicon nitride (SiNx), deposited using inductively coupled plasma chemical vapor deposition system is proposed. The strain analysis is done using Raman spectroscopy. The surface morphology of the SiNx is studied using atomic force microscopy. The breakdown characteristics are ascertained from measurements on high electron mobility transistors and metal–insulator–metal capacitors.

Improving Trace Detection of Methylene Blue by Designing Nanowire Array on Boron-Doped Diamond as Electrochemical Electrode

In this study, a boron-doped diamond nanowire array (BDD-NWA)-based electrode is prepared by using a microwave plasma chemical vapor deposition system and treated with inductively coupled plasma reactive ion etching. The BDD-NWA electrode is used for trace detection of methylene blue, which has a wide linear range of 0.04–10 μM and a low detection limit of 0.72 nM. Both the superhydrophilicity (contact angle ~0°) and the dense nanowire array’s structure after the etching process improve the sensitivity of the electrochemical detection compared to the pristine BDD. In addition, the electrode shows great repeatability (peak current fluctuation range of −3.3% to 2.9% for five detection/cleaning cycles) and stability (peak current fluctuation range of −5.3% to 6.3% after boiling) due to the unique properties of diamonds (mechanical and chemical stability). Moreover, the BDD-NWA electrode achieves satisfactory recoveries (93.8%–107.5%) and real-time monitoring in tap water.

Enhanced field emission characteristics of WS2 nano-films by diamond film and Mo film

WS2 is a type of transition metal chalcogenide materials (TMDCs) that exhibits exceptional photoelectric properties. Due to its atomically sharp edges, WS2 has the capability to enhance the electric field around its edges, thus presenting significant potential in field emission applications. In this study, the electron beam vapor deposition (EBVD) system and microwave plasma chemical vapor deposition (MPCVD) system were used to prepare a series of single-layer WS2 films，single-layer diamond films and diamond/WS2 nano-composite films on N-type highly doped Si substrate, and Mo/WS2 nano-composite films were prepared on Al2O3 ceramic substrate. Based on the characterization and analysis of the microstructure and chemical composition of each thin film layer in the above film devices, the field emission (FE) characteristics of each thin film device are compared and studied. The results demonstrate that the maximum FE current density of diamond/WS2 nano-composite film device is 912 μA/cm2, which is 2.7 times of the maximum FE current density of Mo/WS2 nano-composite film device 330 μA/cm2, and 3.4 times of the maximum FE current density of the single-layer diamond thin film device 267 μA/cm2. The single layer WS2 film did not exhibit measurable FE performance. The working principles of thin film field emission devices with various structures are introduced. It is considered that the diamond layer plays the role of electron accelerating layer, which not only effectively improves the FE characteristics of diamond/WS2 nanocomposite film, but also improves the repeatability and long-term stability of diamond/WS2 nanocomposite film FE devices.

Electrochemical detection of phenacetin with graphite/boron-doped diamond electrode grown at high methane concentration

We have developed a composite electrode containing boron-doped diamond and high graphite content (HGBDD) by microwave plasma chemical vapor deposition system at high methane concentration. The electrode is applied to test the trace level of phenacetin. Scanning rate studies have exhibited that electrochemical oxidation is controlled by adsorption with scanning speed ranging from 20 to 100 mV s−1, while at a higher scanning rate, electrochemical oxidation is controlled by diffusion process. Voltammetry of phenacetin researched on the HGBDD electrode reveals the redox mechanism of phenacetin, the HGBDD has a high current response with a sensitive detection limit of 0.058 μM and a wide linear detection range of 0.5 μM - 400 μM. The high performance could be attributed to the presence of a higher carrier concentration for HGBDD electrode. Based on the density functional theory caculations, the graphite on the diamond surface could adsorb phenacetin strongly and provide more active sites for the redox reaction. Due to the unique properties of diamond, the electrode shows stability, repeatability, and accuracy for detecting phenacetin.

High efficiency of boron doping and fast growth realized with a novel gas inlet structure in diamond microwave plasma chemical vapor deposition system

High efficiency of boron doping and fast growth realized with a novel gas inlet structure in diamond microwave plasma chemical vapor deposition system

Artificial-Neural-Network-Driven Innovations in Time-Varying Process Diagnosis of Low-K Oxide Deposition.

To address the challenges in real-time process diagnosis within the semiconductor manufacturing industry, this paper presents a novel machine learning approach for analyzing the time-varying 10th harmonics during the deposition of low-k oxide (SiOF) on a 600 Å undoped silicate glass thin liner using a high-density plasma chemical vapor deposition system. The 10th harmonics, which are high-frequency components 10 times the fundamental frequency, are generated in the plasma sheath because of their nonlinear nature. An artificial neural network with a three-hidden-layer architecture was applied and optimized using k-fold cross-validation to analyze the harmonics generated in the plasma sheath during the deposition process. The model exhibited a binary cross-entropy loss of 0.1277 and achieved an accuracy of 0.9461. This approach enables the accurate prediction of process performance, resulting in significant cost reduction and enhancement of semiconductor manufacturing processes. This model has the potential to improve defect control and yield, thereby benefiting the semiconductor industry. Despite the limitations imposed by the limited dataset, the model demonstrated promising results, and further performance improvements are anticipated with the inclusion of additional data in future studies.

Investigation on the preparation of large area diamond films with 150–200 mm in diameter using 915 MHz MPCVD system

In this work, the diamond films with 150 mm in diameter were prepared in our home-made 915 MHz microwave plasma chemical vapor deposition (MPCVD) system. The appropriate height of the pocketed substrate holder was researched in order to reduce the edge effect as much as possible. And the diamond thin films which were deposited in the designed substrate holder present relative high uniformity which demonstrated the feasibility of the structure of the substrate holder. Furthermore, the φ 150 mm diamond thick film was deposited using relative higher gas mixture flow rate and microwave power. The thickness variation of the diamond thick film is about 13.4% and the full width at half maximum (FWHM) of the diamond peak increases from 5.78 cm−1 to 7.23 cm−1 with the distance to the center of the diamond film increasing from 0 mm to 70 mm. The I(C2)/I(Hα) across the plasma shows a relative uniform distribution which was kept in the range of 2.9–3.4 in our experiments. Besides that, the φ 200 mm diamond film was attempt to synthesis which illustrates the feasibility of depositing the diamond films with the diameter more than 150 mm, although some improvements on the plasma environment should be considered.

Facile Preparation of Porous Diamond Films via Microwave Plasma Based on Metal Particles Heterogeneous Catalysis Etching

The porous diamond film was fabricated via a self-developed microwave plasma chemical vapor deposition (MPCVD) system in H2/Ar plasma by utilizing micrometer-sized diamond films coated with nickel as starting material. SEM and Raman spectroscopy were used to evaluate the evolution of the morphology and sp3 phase of porous diamond with changes in the surface treatment process parameters, including the etching temperature and time. The results indicate that once the etching temperature exceeds 700 °C, the pitting etching phenomenon can be observed on the surface of diamond film. In a certain range, increasing the etching time increases the depth of surface holes on diamond film, whereas the microporous density exhibits an inverted parabolic change pattern. The porous diamond films with uniform pores structure can be obtained by adopting optimal etching process parameter when the H2/Ar plasma temperature is determined at 900 °C for 30 min. The porous formation mechanism of diamond film is attributed to the nickel particles’ heterogeneous catalysis behavior, which promotes the transition route from diamond phase to graphite phase, followed by the preferential etching of graphite phase by H2/Ar plasma.

Green Reflector with Predicted Chromatic Coordinates

The color reflector with multiple-layer thin film scheme has attracted much attention because of the potential for massive production by wafer-scale deposition and the possibility to integrate with photonics (semiconductor) devices. Here, an angle-insensitive green reflector with a simple multilayer dielectric thin film structure was reported, with predicted chromatic coordinates based on CIE 1931 standard. The SiN/SiO2 multilayer thin film stack, including a special silicon-rich nitride material with ultrahigh refractive index, was grown alternatively by an inductively coupled plasma chemical vapor deposition (ICPCVD) system at a low stage temperature of 80 °C. The green reflector showed a maximum reflectivity of 73% around 561 nm with a full width at half maximum (FWHM) of 87 nm in the visible wavelength range, which contributed significantly to its color appearance. The measurement by an angle-resolved spectrometer under the illumination of p/s-polarized light wave with a variable angle of incidence indicated that the reflectance spectrum blue-shifted slightly with the increasing of incident angle such that the green color could be kept.

LiF film enhanced high brightness blue electroluminescence of diamond /CeF3 composite film

Diamond/CeF3 composite film (DCCF) and diamond/CeF3/LiF composite film (DCLCF) electroluminescent(EL)devices were deposited on n-type heavy-doped silicon substrates by using microwave plasma chemical vapor deposition system (MPCVD) and vacuum electron beam vapor deposition system (EBVD). A series of corresponding tests characterized the composition, microstructure, and EL characteristics of the devices. The experimental results show that the LiF layer can effectively enhance the blue light emission intensity of the composite film device. Blue light emission can be observed in the two types of devices when the forward bias is applied, and the EL spectra of both devices show a strong wide peak at 440 nm. Meanwhile there is no significant difference in the maximum luminous intensity between them. However, when the reverse bias voltage is applied to the two devices, it is found that DCCF device hardly observes visible light emission, while the blue light emission of DCLCF device is very strong. And the EL spectrum of DCLCF device still shows a strong wide peak at 440 nm, and the blue light emission can reach the maximum at 350 V reverse bias voltage. Its maximum luminous intensity is 3.5 times that of DCCF devices, and its brightness can reach 35 cd/m2.

Effects of TiMoTa nano-crystalline interlayer on nucleation, adhesion and tribological behaviors of diamond coating

To investigate the influence of the transition layer on diamond nucleation and growth, the TiMoTa multi-alloy interlayers were firstly prepared on WC-6%Co cemented carbide by double glow plasma surface alloying technique, and diamond was then deposited using microwave plasma chemical vapor deposition system. The thickness of the TiMoTa interlayers increased from 1.2 μm to 2.7 μm with the deposition temperature increasing from 800 to 900 °C. Due to the formation of nano-crystalline structure and hard phase, the as-prepared TiMoTa interlayer exhibited high micro-hardness. In the diamond deposition process, the nano-carbide particles preferentially formed at the TiMoTa interlayers can effectively prevent the further diffusion of C, so the surface carbon concentration rapidly accumulates to the critical value required for the nucleation and growth of diamond microcrystals. Finally, a microscale wear-resistant diamond coating with good adhesion was grown on the transition layer, the crack propagation radius of the diamond coating is ∼162 μm, and can reach Hf 2–3 grade. Therefore, our prepared TiMoTa nano-crystalline interlayer provides a new path for the development of a high-quality diamond coating with good adhesion on cemented carbide.

Effect of argon flow rate and direct current bias on the growth of boron nitride coating in low-temperature plasma

A microwave plasma chemical vapor deposition system was used to synthesize cubic boron nitride (cBN) coatings on diamond seeded silicon substrates using direct current (DC) bias. Effects of the argon (Ar) flow rate and bias voltage on the growth of the cBN coatings were investigated. Hydrogen (H2), argon (Ar), a mixture of diborane in H2 (95% H2, 5% B2H6), and N2 were used in the feed gas. A DC bias system was used for external biasing of the sample, which facilitates the goal of achieving sp3 bonded cBN. Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) revealed the existence of sp3-bonded BN in the produced samples. With increasing Ar flow, the cBN content in the coating increases and reaches a maximum at the maximum Ar flow of 400 SCCM used in this study. High-resolution XPS scans for B1s and N1s indicate that the deposited coating contains more than 70% cBN. This study demonstrates that energetic argon ions generated in a microwave-induced plasma significantly increase cBN content in the coating.

Growth of diamond-like carbon films with significant nanocrystalline phases in a low-pressure high-density CH4 plasma in ICP-CVD: Effect of negative dc substrate bias

Working at relatively low-temperature and low-pressure, the development and optimization of diamond-like carbon (DLC) films with significant nanodiamond components on inexpensive glass substrates, without conventional pre-treatment by diamond powders, is the main objective of the present work. Using the most familiar CH4-precursors diluted by Ar in a high-density plasma triggered at high rf power (900 W) in a planar inductively-coupled plasma chemical vapour deposition (ICP-CVD) system, DLC thin-films are prepared via optimization in the flow rate of the precursor gas at 30 mTorr (∼4 Pa) pressure and 450 °C substrate temperature and, further by applying negative dc-bias to the substrates. The optimized samples obtained with negative substrate-bias possess good crystalline properties. From Raman results, the most crystalline sample is obtained with characteristic minimum ID/IG ratio reduced from 0.75 to 0.61, maximum IDia/ID enhanced from 0.94 to 1.09, and the sp3 hybridized CC bonds increased from 44% to ∼64% at a substrate-bias of –40 V. The residual stress, and the optical band gap were calculated from Raman analysis. The optimized DLC film exhibits a high optical band gap (3.71 eV) as calculated from Tauc’s plot analysis of the UV–Vis data. The well-identified 〈111〉 crystallographic planes in the TEM micrograph demonstrate a significant fraction of nanocrystalline diamond component in the optimum DLC film.

Effects of the electric field at the edge of a substrate to deposit a Ø100 mm uniform diamond film in a 2.45 GHz MPCVD system

In this study, uniform diamond films with a diameter of 100 mm were deposited in a 15 kW/2.45 GHz ellipsoidal microwave plasma chemical vapour deposition system. A phenomenological model previously developed by our group was used to simulate the distribution of the electric strength and electron density of plasma. Results indicate that the electric field in the cavity includes multiple modes, i.e. TM02 and TM03. When the gas pressure exceeds 10 kPa, the electron density of plasma increases and plasma volume decreases. A T-shaped substrate was developed to achieve uniform temperature, and the substrate was suspended in air from Ø70 to 100 mm, thus eliminating vertical heat dissipation. An edge electric field was added to the system after the introduction of the T-shaped substrate. Moreover, the plasma volume in this case was greater than that in the central electric field but smaller than that in the periphery electric field of the TM02 mode. This indicates that the electric field above and below the edge benefits the plasma volume rather than the periphery electric field of the TM02 mode. The quality, uniformity and surface morphology of the deposited diamond films were primarily investigated to maintain substrate temperature uniformity. When employing the improved substrate, the thickness unevenness of the Ø100 mm diamond film decreased from 22% to 7%.

Low-temperature synthesis of high-quality graphene by controlling the carbon-hydrogen ratio of the precursor

A furnace-free inductively coupled plasma chemical vapor deposition (ICP-PECVD) system, which does not require sample heating, was used to grow graphene at a temperature below 300 °C. This studies have found that under low-temperature PECVD growth conditions, liquid precursors are more suitable for preparing low-temperature graphene precursors than gaseous precursors.​​​​ Hence, benzene is used as a carbon precursor to obtain a sheet resistance of approximately 1.24 kΩ sq−1. In this research, it was discovered that the carbon-hydrogen ratio of the precursor molecule is an important factor while using PECVD to grow graphene. This factor affects the quality of graphene and the sheet resistance value —when the carbon–hydrogen ratio for the precursor molecule is 1:1, graphene has the high quality and lowest sheet resistance; when it is less than 1:2, the graphene that cannot be deposited has the worst quality and sheet resistance. Furthermore, we found that methane, a precursor often used to deposit graphene, will etch graphene under low-temperature conditions, and that acetylene can be used as a precursor to deposit graphene. It was further proven that the carbon–hydrogen ratio of the precursor molecules in the PECVD process caused the reduction in the graphene temperature.

Preparation and characterization of diamond-like carbon (DLC) film on 316L stainless steel by microwave plasma chemical vapor deposition (MPCVD)

The 316L stainless steel was widely used in medical, surgical instruments and human implant medical materials. The diamond-like carbon (DLC) films were deposited on 316L stainless steel by varying temperature, CH4:H2 flow rate, and deposition time in a microwave plasma chemical vapor deposition (MPCVD) system to improve their biocompatibility. The morphology and composition of deposited films were investigated using a scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscope. The results showed that with the increase in deposition temperature and the decrease in gas flow ratio, the structure of the film gradually became compact and smooth, and the graphite phase structure of the film tended to change to diamond phase. In addition, the island-like structure gradually grew into a sheet, and the defects in the films were reduced with the enhanced bonding force between the films and the stainless steel matrix. The optimum temperature and gas flow ratios were 900 °C and 10:190, respectively. Medical stainless steels containing DLC films had better bone-forming ability and biocompatibility than untreated.

Intrinsic, P-doped and B-doped nanocrystalline silicon thin films grown at room temperature on flexible substrates for photovoltaic applications

Nanocrystalline silicon (nc-Si) thin films in its intrinsic (i-nc-Si), B-doped (p-nc-Si) and P-doped (n-nc-Si) configurations were developed on the flexible substrates at ambient temperature (∼30 °C), using no additional H2 dilution in planar inductively coupled plasma chemical vapour deposition (ICP-CVD) system. A superior crystallinity (∼81%) with electrical conductivity (σD ∼10-7 S cm−1) was achieved for the intrinsic Si thin film by the virtue of the presence of atomic-H in high density within ICP-CVD, which initiates nucleation even at room temperature on the flexible substrates. Substitution of boron (B) dopants at the crystalline Si lattice maintains a high crystallinity (∼80%) and results significantly high electrical conductivity (6 x10-1 S cm−1) in the p-nc-Si thin film. On the contrary, during the growth of n-nc-Si films, a substantial amount of phosphorous (P) dopants, residing at the interstitial position, results in a moderate crystallinity (∼73%) and relatively lesser conductivity (3 x10-1 S cm−1) than the p-nc-Si films. Finally, in the present work i-nc-Si, p-nc-Si and n-nc-Si thin films all are successfully prepared on the flexible substrates at room temperature, with ample crystallinity, wide optical band gap (∼1.9–1.80 eV) and significant electrical conductivity, which appear suitable for the low-cost fabrication of flexible p-i-n solar cells.

Surface Morphology and Microstructure Evolution of Single Crystal Diamond during Different Homoepitaxial Growth Stages.

Homoepitaxial growth of step-flow single crystal diamond was performed by microwave plasma chemical vapor deposition system on high-pressure high-temperature diamond substrate. A coarse surface morphology with isolated particles was firstly deposited on diamond substrate as an interlayer under hillock growth model. Then, the growth model was changed to step-flow growth model for growing step-flow single crystal diamond layer on this hillock interlayer. Furthermore, the surface morphology evolution, cross-section and surface microstructure, and crystal quality of grown diamond were evaluated by scanning electron microscopy, high-resolution transmission electron microcopy, and Raman and photoluminescence spectroscopy. It was found that the surface morphology varied with deposition time under step-flow growth parameters. The cross-section topography exhibited obvious inhomogeneity in crystal structure. Additionally, the diamond growth mechanism from the microscopic point of view was revealed to illustrate the morphological and structural evolution.

A Heat Transfer Model for Graphene Deposition on Ni and Cu Foils in a Roll-to-Roll Plasma Chemical Vapor Deposition System

Abstract High-throughput production is a major bottleneck for integration of graphene-based technologies in existing and future applications. Here, a semi-empirical heat transfer model is developed to optimize large-scale deposition of graphene on Ni and Cu foils in a roll-to-roll (R2R) plasma chemical vapor deposition (CVD) system. Temperature distributions in Ni and Cu foils during deposition are recorded with in situ temperature measurements using near-IR optical emission spectroscopy. The model indicates that foil movement significantly affects the temperature distribution and the cooling rate of the foil. Consequently, graphene growth on Cu is limited to lower web speeds for which the foil temperature is higher, and the residence time in the plasma is longer. On the other hand, graphene can be deposited on Ni at relatively higher web speeds due to moderately high diffusion rate of carbon in Ni and increased cooling rates up to 20 K/s with higher web speed. Critical limitations in the production rates of graphene using R2R CVD process exist due to significant effects of web speed on the temperature distribution of the substrate. The thermal analysis approach reported here is expected to aid in enhancing the throughput of graphene production in R2R CVD systems.

Plasma Polymerized SiCOH Films from Octamethylcyclotetrasiloxane by Dual Radio Frequency Inductively Coupled Plasma Chemical Vapor Deposition System.

We have fabricated porous plasma polymerized SiCOH (ppSiCOH) films with low-dielectric constants (low-k, less than 2.9), by applying dual radio frequency plasma in inductively coupled plasma chemical vapor deposition (ICP-CVD) system. We varied the power of the low radio frequency (LF) of 370 kHz from 0 to 65 W, while fixing the power of the radio frequency (RF) of 13.56 MHz. Although the ppSiCOH thin film without LF had the lowest k value, its mechanical strength is not high to stand the subsequent semiconductor processing. As the power of the LF was increased, the densities of ppSiCOH films became high, accordingly high in the hardness and elastic modulus, with quite satisfactory low-k value of 2.87. Especially, the ppSiCOH film, deposited at 35 W, exhibited the highest mechanical strength (hardness: 1.7 GPa, and elastic modulus: 9.7 GPa), which was explained by Fourier transform infrared spectroscopy. Since the low-k material is widely used as an inter-layer dielectric insulator, good mechanical properties are required to withstand chemical mechanical polishing damage. Therefore, we suggest that plasma polymerized process based on the dual frequency can be a good candidate for the deposition of low-k ppSiCOH films with enhanced mechanical strength.