Substrate Holders Research Articles

Large-scale fabrication of thulium iron garnet film with perpendicular magnetic anisotropy using RF magnetron sputtering

Large-scale fabrication of thulium iron garnet (TmIG) films on gadolinium gallium garnet (GGG) substrates, with a total area of 25 cm2, has been demonstrated by rotating substrate holders during on-axis sputtering. By optimizing the growth parameters based on the pressure and flow rate of the oxygen ratio, a Tm/Fe ratio of 0.65 was obtained, which is close to the stoichiometry of TmIG. The increase in post-annealing temperature has induced the growth of the TmIG structure by the strain of the lattice constant mechanism. At the highest post-annealing temperature, the crystal structure of TmIG (444) and the perpendicular magnetic anisotropy (PMA) were obtained. This result demonstrates the potential method for large-scale fabrication of TmIG film with PMA.

Ultra‐Inclined Nanocolumnar ZnO Films Sputtered Using a Novel Masking Configuration Providing Controlled and Restricted Oblique Angle Deposition for Enhanced Sensing Platforms

AbstractOblique angle deposition (OAD) of inclined thin films is mainly performed using electron beam evaporation due to its accurate point source control over the incoming evaporated flux angle α, leading to thin films with a nanocolumnar inclination angle β. However, the utilization of magnetron sputtering (MS) with an extended source for OAD is not extensively studied and reported. This work presents a thorough analysis of ZnO inclined thin films deposited by a novel restricted DC‐reactive MS‐OAD technique. OAD‐inclined films are deposited at α ranged 60°‐88°, where incoming flux is restricted using a patented masking configuration enabling tunable control of deposited nanocolumn angular range. The described technique provides accurate control over the resulting β (99.5% reproducibility), allowing demonstrated βmax of 47.3°, close to theoretical limits predicted for ZnO. The approach discussed here probes enhanced control of β comparable to that observed in evaporation, however using an extended source, resulting in high‐quality reproducible nanocolumnar‐inclined films. The mentioned improvements result from the exploration of operational parameters such as magnetron power, working pressure, and chamber temperature, as well as the design of the restricting configuration and substrate holders and their influence on the resulting inclined thin film crystallinity, and morphology.

Difference in the structure and morphology of CVD diamond films grown on negatively charged and grounded substrate holders: Optical study

Microcrystalline diamond films were grown by plasma-enhanced chemical vapor deposition from a CH4/H2 gas mixture on Si single-crystalline substrates placed on negatively charged and grounded substrate holders. The obtained diamond films had the (100) predominant faceting of microcrystals. The film structure and morphology were analyzed by scanning electron microscopy, photoluminescence, Raman and FTIR spectroscopies. The main physical factor causing the difference in the structure of the diamond films grown on the grounded and charged substrate holders was found to be the flow of low-energy (up to 200 eV) Si+, N2+, H, O ions in the latter holder. These ions predominantly embedded into the structure of the diamond films grown on the charged substrate holder leading to appearance of residual mechanical stress up to 2 GPa. Ion bombardment led to increase in the volume fraction of non-diamond carbon component in the film grain boundaries, decrease in sp3-bonded carbon fraction and reduction of the diamond microcrystals lateral size. Larger amount of grain boundaries in the diamond films grown on the charged substrate holder promoted diffusion of Si atoms from the substrate to the plasma and growing film surface, inducing formation of SiV centers in the diamond microcrystals even in the 150…200 μm thick films. The concentration of Si-related defects was much smaller in the films grown using the grounded substrate holder. These films had substantially smaller volume fraction of graphite-like carbon in the grain boundaries and were more homogeneous.

Maasi: A 3D printed spin coater with touchscreen

Spin coaters are widely used to apply thin films of a material uniformly over a flat substrate. Despite the simplicity of this technique the entry price for such machines might be prohibitive, ranging from few hundreds to thousands of Euros. Here we present Maasi, an affordable alternative that is easy to build and has all functional key features to be used in a wide range of applications. Our design has a price of less than hundred Euros and an assembly time of only two hours. One of the key design principles was to use only 3D printed parts in combination with affordable Commercial Off-The-Shelf (COTS) components [1]. Reducing the complexity we use an electronic speed controller (ESC) with telemetry, to eliminate the need for a rotor position sensor [2]. A touchscreen further improves its usability, thus setting a perfect startpoint for the design of other affordable lab tools. The Maasi project includes different 3D printable substrate holders allowing treatment of formats up to 80 mm in diameter. We furthermore validate the Maasi spin coater by measuring its speed accuracy and performance for coating polydimethylsiloxane (PDMS) on glass coverslips for mechanobiological assays.

VACUUM UNIT WITH ELECTRON-BEAM EVAPORATOR AND VACUUM LOADING OF GROUP SUBSTRATE HOLDERS, "Электронная техника. Серия 3. Микроэлектроника"

A new vacuum unit (ELU TM 1Sh) with mult-crucible electron beam evaporation (EBE) and lock loading of group substrate holders for 100-150 mm wafers has been developed. The unit is intended mainly for deposition of single-layer or multilayer films in explosive photolithography technology.

Effective cooling of substrates with low thermal conductivity under conditions of gas-jet MPCVD diamond synthesis

The paper presents the results of an experimental study of heating molybdenum and silicon substrates under the conditions of gas-jet deposition of diamond structures using the precursor gases of a microwave discharge to activate. A cooled substrate holder using a metal melt to improve heat removal by reducing the thermal resistance between the substrate and the substrate holder has been developed. The use of the melt allowed lowering the temperature of the silicon substrate under the conditions of gas-jet deposition to a level that ensures the preservation of its structure. The developed substrate holders were used to carry out gas-jet synthesis of diamond structures on molybdenum and silicon substrates.

Correction of thickness uniformity of multilayer fluoride coatings on steep spherical substrates using shadowing mask combinations in planetary rotation systems.

In this study, the deposition angle parameter was introduced into the traditional deposition model to eliminate the coating thickness errors caused by large deposition angles and differences in the microstructures of coatings from the expected values. Based on the different thickness distributions of MgF2 and LaF3 coatings, a method that involves switching shadowing masks and a stepwise numerical optimization algorithm were proposed to control each coating thickness distribution accurately. When designing shadowing masks for a multilayer antireflective (AR) coating with a wide incident angle range, the correlation between the thickness distributions of the MgF2 and LaF3 layers was added to the merit function to ensure consistency in the two distributions. Two-layer deep-ultraviolet (DUV) AR fluoride coatings and a six-layer DUV low-polarization antireflection fluoride coating at 193 nm were fabricated on spherical substrate holders using thermal evaporation. In the experiment, when the ratio of the clear aperture to the radius of curvature was increased from -1.68 to 1.63, the thickness uniformities of the MgF2 and LaF3 layers of the two-layer DUV AR coatings on the fused silica substrates increased to a minimum of 98.49%. Owing to the transmission spectra and the incidence angle-resolved transmission, uniform optical performance and low-variation polarization transmittance were also achieved for the 193 nm AR coating deposited on the fused silica substrates.

Tuning Hybrid Nano-semiconductor-glass Via High Intensity Laser

Conceptually, the high intensity laser represents the simplest thin film deposition techniques that consists of both a target and a substrate holders housed in a vacuum chamber with a high powered pulsed laser as the external energy source for evaporation of target material (Semiconductor Glass). Using deposit thin laser films three ranges of frequencies were produced: (0-15,000 mJ/cm2) as a result tuning of semiconductor was satisfying condition, while the second, 0-33,000 mJ/cm2 as a result tuning of semiconductor had a stable condition and the last 0-100,000 mJ/cm2 as a result tuning of semiconductor was unstable condition. The results demonstrate a decrease in resistance due to charging the semiconductor glass by high intensity laser as well as a superior charge efficiency and lifetime of semiconductor glass coated cells compared to high intensity laser. The current increase in the charge appeared proportional with extra energy stored of the semiconductor glass coated electrodes at 2Co (>23%) in comparison with control. It is concluded that an increase in the capacity of semiconductor glass may address the main difficulty for utilizing the high intensity laser chemistry for future demands.

Expansion of intertidal mussel beds following disease-driven reduction of a keystone predator

Disease shapes community composition by removing species with strong interactions. To test whether the absence of keystone predation due to disease produced changes to the species composition of rocky intertidal communities, we leverage a natural experiment involving mass mortality of the keystone predator Pisaster ochraceus from Sea Star Wasting Syndrome. Over four years, we measured dimensions of mussel beds, sizes of Mytilus californianus, mussel recruitment, and species composition on vertical rock walls at six rocky intertidal sites on the central California coast. We also assessed the relationship between changes in mussel cover and changes in sea star density across 33 sites along the North American Pacific coast using data from long-term monitoring. After four years, the lower boundary of the central California mussel beds shifted downward toward the water 18.7 ± 15.8 cm (SD) on the rock and 11.7 ± 11.0 cm in elevation, while the upper boundary remained unchanged. In central California, downward expansion and total area of the mussel bed were positively correlated with mussel recruitment but were not correlated with pre-disease sea star density or biomass. At a multi-region scale, changes in mussel percent cover were positively correlated with pre-disease sea star densities but not change in densities. Species composition of primary substrate holders and epibionts below the mussel bed remained similar across years. Extirpation of the community below the bed did not occur. Instead, this community became limited to a smaller spatial extent while the mussel bed expanded.

Targeting improved reproducibility in surface-enhanced Raman spectroscopy with planar substrates using 3D printed alignment holders.

Drop-casting is frequently used to deliver a sample for surface-enhanced Raman spectroscopy (SERS) and can result in inhomogeneous sample distribution during solvent evaporation. While soaking can provide better analyte homogeneity, it may require more sample than is available. Failure to optically sample analyte-rich substrate locations can compromise measurement outcomes. We developed and tested 3D printed SERS substrate holders that provided spatial registry of the dried sample droplet center for subsequent optical measurements. We found that deliberate and controlled spatial offsets (0-900 µm) between the analyte drop center and the laser excitation prevented signal intensity drops of as much as ∼3× and improved reproducibility. Thus, the use of offset-controlled 3D printed holders provided a quick and inexpensive way to improve the reliability of SERS measurements when using the convenient and popular choice of sample drop-casting.

Impact of CVD-synthesis parameters and film thickness on growth rate of single-crystal diamond

The widespread use of CVD-reactors of various constructions and the influence of many factors on the formation of energy-saturated reaction zone has led to the fact of significant difference of technological parameters optimal for each reactor even of one brand. An economically important parameter, in addition to the quality of the obtained single-crystal diamond layer, is the growth rate, which depends on many factors: the flow rate and chemical composition of gases, pressure in the reaction chamber, substrate temperature, the shape of the formed plasma cloud, dimensions and shape of molybdenum substrate holders and et al. This work is devoted to the experimental determination of the single-crystal CVD-diamonds growth rate across various synthesis conditions on Ardis 300. In research, we shown the effect of the thickness of the synthesized diamond layer on the rate of formation of subsequent diamond layers, which is associated with a change in the degree of misorientation between the crystallographic plane (100) and direction [100]. Also, this can be associated with an increase in the roughness of the growing surface, leading to an increase in the specific number of active centers thermodynamically favorable for carbon deposition during the formation of the crystal structure of diamond.

Effect of Substrate Holder Design on Stress and Uniformity of Large-Area Polycrystalline Diamond Films Grown by Microwave Plasma-Assisted CVD

In this work, the substrate holders of three principal geometries (flat, pocket, and pedestal) were designed based on E-field simulations. They were fabricated and then tested in microwave plasma-assisted chemical vapor deposition process with the purpose of the homogeneous growth of 100-μm-thick, low-stress polycrystalline diamond film over 2-inch Si substrates with a thickness of 0.35 mm. The effectiveness of each holder design was estimated by the criteria of the PCD film quality, its homogeneity, stress, and the curvature of the resulting “diamond-on-Si” plates. The structure and phase composition of the synthesized samples were studied with scanning electron microscopy and Raman spectroscopy, the curvature was measured using white light interferometry, and the thermal conductivity was measured using the laser flash technique. The proposed pedestal design of the substrate holder could reduce the stress of the thick PCD film down to 1.1–1.4 GPa, which resulted in an extremely low value of displacement for the resulting “diamond-on-Si” plate of Δh = 50 μm. The obtained results may be used for the improvement of already existing, and the design of the novel-type, MPCVD reactors aimed at the growth of large-area thick homogeneous PCD layers and plates for electronic applications.

Improving the edge quality of single-crystal diamond growth by a substrate holder – An analysis

During the growth of a single-crystal diamond by MPCVD, polycrystalline diamonds are prone to grow in the edge regions. This substantially reduces the usable area of the grown diamond film. In addition, the inhomogeneous distribution of internal stress causes diamond to crack during continuous growth. In recent years, a series of experimental studies have been carried out to solve these problems and some achievements have been obtained. However, in order to understand fundamentally the growth mechanism of diamond, the relationship between growth quality and various influencing factors still needs to be quantitatively studied through integrated simulations and experiments. Electron number density and substrate temperature are important factors affecting diamond crystallization quality. In this paper, the growth conditions of the diamond were simulated and analyzed. Simulation results were compared with the experimental results. This evidences that the surface temperature distribution is relatively homogeneous, and that the significant electron number density gradient in the axial direction is the main reason for the formation of polycrystals in the edge regions. Therefore, substrate holders with different cavity depths were designed and the substrates grew in the same temperature range. The surface morphologies, crystalline qualities, and internal stress distributions of the grown diamonds were measured, and it was found that the quality of growth increased first and then decreased with the depth of the cavity, while the growth rate decreased with increasing the latter. These results are in good agreement with the simulation results. Finally, suggestions on the selection of the substrate holder for film growth with different thicknesses are proposed. Lors de la croissance d'un monocristal de diamant par MPCVD, des diamants polycristallins ont tendance à pousser sur les bords. Ceci réduit considérablement la surface utilisable du film de diamant obtenu. De plus, la distribution non homogène des contraintes internes provoque la fissuration du diamant au cours de sa croissance. Ces dernières années, plusieurs études expérimentales ont été menées pour résoudre ces problèmes, et des résultats ont été obtenus. Cependant, pour comprendre fondamentalement le mécanisme de croissance du diamant, la relation entre la qualité de la croissance et divers facteurs l'influençant doit encore être étudiée quantitativement au moyen de simulations et d'expériences intégrées. La densité du nombre d'électrons et la température du substrat sont des facteurs importants affectant la qualité de la cristallisation du diamant. Dans cet article, les conditions de croissance du diamant ont été simulées et analysées. Les résultats de la simulation ont été comparés aux résultats expérimentaux. Ceci montre que la distribution de la température de surface est relativement homogène et que le gradient significatif de densité numérique d'électrons dans la direction axiale est la raison principale de la formation de polycristaux sur les bords. Par conséquent, des supports de substrat avec des profondeurs de cavité différentes ont été conçus, et les substrats se sont développés dans la même plage de température. Les morphologies de surface, les qualités cristallines et la distribution des contraintes internes des diamants cultivés ont été mesurées, et on a constaté que la qualité de la croissance augmentait d'abord, puis diminuait avec la profondeur de la cavité, tandis que le taux de croissance diminuait avec l'augmentation de cette dernière. Ces résultats concordent bien avec les résultats de la simulation. Enfin, des suggestions quant au choix du support de substrat pour la croissance de films de différentes épaisseurs sont proposées.

Развитие ионно-плазменных технологий на основе корончатых подложкодержателей

Развитие ионно-плазменных технологий на основе корончатых подложкодержателей

Nonlinear Optical Properties of Zinc Oxide Thin Films Produced by Pulsed Laser Deposition

Abstract In this work, the nonlinear optical properties of Zinc Oxide (ZnO) thin films produced on microscope slide glass substrates at room temperature (RT) using Pulsed Laser Deposition (PLD) method has been presented. PLD system consists of a vacuum chamber (pumped by a turbo molecular pump, backed with a rotary pump), rotating sample and substrate holders, optical thickness measurement system, infrared temperature measurement system and a nanosecond laser system. Previously deposition vacuum chamber evacuated down to ∼10-8 mbar and deposition was taken place about 1.3×10-1 mbar oxygen background gas pressure value. Morphological properties of thin films were obtained by Atomic Force Microscopy (AFM) that shows homogenous and smooth film structure. Thin films crystallinity were investigated by using X-Ray Diffraction (XRD) method and showed that polycrystalline ZnO structure with the largest peak corresponding to (002) orientation but some films contain Zn with (101) orientation . The thicknesses of the films were deduced from reflectance measurement using a fitting software and crosschecked with profilometer and AFM measurements. The thickness of the films ranged between 10 nm and 220 nm. Linear optical properties were obtained by using UV-VIS Spectrometer. Furthermore, we presented the nonlinear optical properties of the ZnO thin films that were obtained by the z-scan method

Fabrication and modal characterisation of large‐area polymer membranes for acoustic micro‐electromechanical systems devices

Bilayer polymer/metal suspended membranes made of poly(methyl methacrylate) (PMMA) and aluminium (Al) have been fabricated using a wet transfer technique where a polyelectrolyte (polydiallyldimethylammonium chloride - PDAC) has been employed as sacrificial layer to facilitate the detachment of the thin PMMA/Al layers from the substrate holders. In this way, free-standing PMMA/Al membranes with outstanding diameter (3.5 mm) to thickness (400 nm) ratios of ~10 4 have been obtained. The membranes have been actuated mechanically and electrothermally and their modal behaviour characterised using laser Doppler vibrometry. The first five modes of vibrations have been detected in the range of 2-25 kHz. The second and fifth degenerate modes have been seen to split, probably due to non-uniform tension or mass density. The membranes can achieve vibration amplitudes in the order of few tens of microns. When performing electro-thermal actuation, it has been observed that the amplitude of a single mode can be tuned by controlling the path of the electric current across the membrane.

Self-contained in-vacuum in situ thin film stress measurement tool.

A fully self-contained in-vacuum device for measuring thin film stress in situ is presented. The stress was measured by measuring the curvature of a cantilever on which the thin film was deposited. For this, a dual beam laser deflectometer was used. All optics and electronics needed to perform the measurement are placed inside a vacuum-compatible vessel with the form factor of the substrate holders of the deposition system used. The stand-alone nature of the setup allows the vessel to be moved inside a deposition system independently of optical or electronic feedthroughs while measuring continuously. A Mo/Si multilayer structure was analyzed to evaluate the performance of the setup. A radius of curvature resolution of 270 km was achieved. This allows small details of the stress development to be resolved, such as the interlayer formation between the layers and the amorphous-to-crystalline transition of the molybdenum which occurs at around 2 nm. The setup communicates with an external computer via a Wi-Fi connection. This wireless connection allows remote control over the acquisition and the live feedback of the measured stress. In principle, the vessel can act as a general metrology platform and add measurement capabilities to deposition setups with no modification to the deposition system.

Stress Analysis for a Substrate Holder Module and Thin Films Grown in an MOCVD Reactor

The aim of this work is, using finite element analysis, to study the effects of thermal load and rotation speed on the structural integrity of a substrate holder module in an MOCVD reactor. Several loading conditions are considered, including thermal load and rotational speeds of 0-1500 rpm. In addition, the wafer bow and residual stress of GaN film grown on silicon or sapphire wafer are systematically studied. Simulation results indicate the variation of critical stress with rotation speed in all of the components is small. Given a similar heat source in the MOCVD reactor, temperature of the upper components such as susceptor, substrate holders, and wafers is higher in the case of sapphire wafer than that in the case of silicon wafer. The temperature gradient of upper components is greater for the silicon wafer case. A greater temperature gradient in the film-substrate system generates a greater wafer bow and residual stress in the grown thin film. Therefore, temperature uniformity is an important parameter for the epitaxial process. The sign of residual stress is different between a GaN film grown on a sapphire wafer and a silicon wafer (compressive for sapphire wafer and tensile for silicon wafer). For growing a GaN thin film, sapphire wafer is better than silicon wafer in terms of lessening cracking in film.

CVD growth of monolayer MoS2: Role of growth zone configuration and precursors ratio

Single-layer, large-scale two-dimensional material growth is still a challenge for their wide-range usage. Therefore, we carried out a comprehensive study of monolayer MoS2 growth by CVD investigating the influence of growth zone configuration and precursors ratio. We first compared the two commonly used approaches regarding the relative substrate and precursor positions, namely, horizontal and face-down configurations where face-down approach is found to be more favorable to obtain larger flakes under identical growth conditions. Secondly, we used different types of substrate holders to investigate the influence of the Mo and S vapor confinement on the resulting diffusion environment. We suggest that local changes of the S to Mo vapor ratio in the growth zone is a key factor for the change of shape, size and uniformity of the resulting MoS2 formations, which is also confirmed by performing depositions under different precursor ratios. Therefore, to obtain continuous monolayer films, the S to Mo vapor ratio is needed to be kept within a certain range throughout the substrate. As a conclusion, we obtained monolayer triangles with a side length of 90 µm and circles with a diameter of 500 µm and continuous films with an area of 850 µm × 1 cm when the S-to-Mo vapor ratio is optimized.

MPACVD growth of single crystalline diamond substrates with PCD rimless and expanding surfaces

Single crystal diamond (SCD) growth was performed in optimized pocket substrate holders at a high pressure (240 Torr) and a high power density (∼1000 W/cm3). In an effort to overcome the challenges of growing large area SCD substrates without a corresponding polycrystalline diamond (PCD) rim, a growth recipe using these pocket holders was developed. This growth recipe controls the substrate temperature (Ts) and the incident microwave power (Pinc) in a prescribed function of growth time. Through this process, the feasibility to enlarge the SCD substrate in situ, i.e., during the growth itself is shown. By allowing the temperature to increase from ∼980 °C to 1040 °C, then reducing the temperature, and then allowing it to drift up again, the deposition process alternates between the fast growth of the different crystal directions (i.e., 〈110〉, 〈111〉, and 〈100〉) and a slow growth to smoothen the top surface. This leads to an increased lateral SCD growth. The slow growth of the crystal faces in turn leads to a smooth and enlarged top surface. Certain strategies such as the termination of the growth process at the appropriate time are critical in obtaining flat and smooth SCD surfaces without the formation of any PCD rim. The SCD substrates grown via this method have been analyzed by optical and scanning electron microscopies. The lateral SCD surface area increased between 1.7 and 2 times greater than the initial seed surface area during one continuous run. The deposited SCDs have high growth rates of ∼30 μm/h resulting in smooth, flat and rimless substrates, hence indicating the improvement in the quality and morphology of the deposited substrates.