Plasma-enhanced Atomic Layer Deposition Process Research Articles

Plasma enhanced atomic layer deposition of silicon nitride using magnetized very high frequency plasma

To obtain high-quality SiN x films applicable to an extensive range of processes, such as gate spacers in fin field-effect transistors (FinFETs), the self-aligned quadruple patterning process, etc, a study of plasma with higher plasma density and lower plasma damage is crucial in addition to study on novel precursors for SiN x plasma-enhanced atomic layer deposition (PEALD) processes. In this study, a novel magnetized PEALD process was developed for depositing high-quality SiN x films using di(isopropylamino)silane (DIPAS) and magnetized N2 plasma at a low substrate temperature of 200 °C. The properties of the deposited SiN x films were analyzed and compared with those obtained by the PEALD process using a non-magnetized N2 plasma source under the same conditions. The PEALD SiN x film, produced using an external magnetic field (ranging from 0 to 100 G) during the plasma exposure step, exhibited a higher growth rate (∼1 Å/cycle) due to the increased plasma density. Additionally, it showed lower surface roughness, higher film density, and enhanced wet etch resistance compared to films deposited using the PEALD process with non-magnetized plasmas. This improvement can be attributed to the higher ion flux and lower ion energy of the magnetized plasma. The electrical characteristics, such as interface trap density and breakdown voltage, were also enhanced when the magnetized plasma was used for the PEALD process. Furthermore, when SiN x films were deposited on high-aspect-ratio (30:1) trench patterns using the magnetized PEALD process, an improved step coverage of over 98% was achieved, in contrast to the conformality of SiN x deposited using non-magnetized plasma. This enhancement is possibly a result of deeper radical penetration enabled by the magnetized plasma.

Investigation of atomic layer deposition methods of Al2O3 on n-GaN

In this work, three atomic layer deposition (ALD) approaches are used to deposit an Al2O3 gate insulator on n-GaN for application in vertical GaN power switches: thermal ALD (ThALD), plasma-enhanced ALD (PEALD), and their stacked combination. The latter is a novel method to yield the most ideal insulating layer. Also, the influence of an in situ NH3 or H2 plasma pre-treatment is studied. Planar MIS capacitors are used to investigate the electrical properties and robustness of the gate insulators. In vacuo x-ray photoelectron spectroscopy (XPS) is used to study the changes in chemical composition after every surface treatment. XPS shows that all plasma pre-treatments efficiently remove all carbon contamination from the surface, but only NH3 plasma is observed to additionally remove the native oxide from the n-GaN surface. The water precursor step in the ThALD process does not completely remove the CH3 ligands of the trimethylaluminum precursor step, which might electrically be associated with a reduced forward bias robustness. The O2 plasma step in the PEALD process is associated with the removal of carbon and a tremendous increase of the O content in the GaN surface region. Electrically, this strongly correlates to an enhanced forward bias robustness and an increased forward bias hysteresis, respectively. The ThALD/PEALD stack method mitigates the shortcomings of both ALD processes while maintaining its advantages. Electrical measurements indicate that the stack method alongside NH3 plasma pretreatment provides the best characteristics in terms of hysteresis, threshold voltage, forward bias robustness, and interface trap density of states.

Suppressing substrate oxidation during plasma-enhanced atomic layer deposition on semiconductor surfaces

Plasma-enhanced atomic layer deposition (PE-ALD) is widely employed in microelectronics, energy, and sensing applications. Typically, PE-ALD processes for metal oxides utilize remote inductively coupled plasmas operated at powers of >200 W, ensuring a sufficient flux of oxygen radicals to the growth surface. However, this approach often leads to significant oxidation of chemically sensitive substrates, including most technological semiconductors. Here, we demonstrate that plasma powers as low as 5 W can effectively suppress substrate oxidation while maintaining the structural, optical, and electronic quality of the films. Specifically, we investigate the growth of titanium oxide (TiOx) using two commonly used metalorganic precursors, titanium isopropoxide and tetrakis(dimethylamino)titanium. Films deposited with 5 and 300 W oxygen plasma power are nearly indiscernible from one another, exhibiting significantly lower defect concentrations than those obtained from thermal ALD with H2O. The low plasma power process preserves desired physical characteristics of PE-ALD films, including large optical constants (n > 2.45 at 589 nm), negligible defect-induced sub-bandgap optical absorption (α < 102 cm−1), and high electrical resistivity (>105 Ω cm). Similar behavior, including suppressed interface oxidation and low defect content, is observed on both Si and InP substrates. As an example application of this approach, the assessment of InP/TiOx photocathodes and Si/TiOx photoanodes reveals a significant improvement in the photocurrent onset potential in both cases, enabled by suppressed substrate oxidation during low power PE-ALD. Overall, low power PE-ALD represents a generally applicable strategy for producing high quality metal oxide thin films while minimizing detrimental substrate reactions.

Plasma‐Enhanced Atomic Layer Deposition of Amorphous Tantalum Thin Films for Copper Interconnects Using an Organometallic Precursor

AbstractAs integrated circuits continue to shrink in size, the demand for high‐quality adhesive layers in copper Damascene interconnects has increased. However, tantalum (Ta) films, used as liners, prepared by atomic layer deposition (ALD) from metal halide precursors, are prone to corrosion and exhibit issues such as low film density and unstable performance. In this study, Ta films are successfully fabricated using a plasma‐enhanced ALD (PEALD) process with an organometallic precursor of Ta(NtBu)(NEt2)3 (TBTDET). The study of the growth conditions reveals that introducing 10% Ar in Ar‐H2 mixed gas leads to continuous high‐quality Ta films. The deposited Ta films are free of halogen impurities, which can avoid the detrimental impact on the stability of the Cu interconnects. Although the films contain some carbon and nitrogen impurities, they do not affect the film adhesive properties. Transmission electron microscopy shows that the Ta films are amorphous, and the amorphous Ta films exhibit superior barrier properties. Moreover, highly uniform Ta films can be conformally deposited into narrow interconnect structures using this PEALD process. These findings suggest that the Ta films prepared by the organometallic precursor can offer a promising solution to address the issues related to the halogen elements in the adhesive layer preparation.

Multi-Scale Simulations of Gas-Phase Particles Generated in Plasma Enhanced Atomic Layer Deposition Processes

Recently, Plasma Enhanced Atomic Layer Deposition (PEALD) has been investigated as an advanced semiconductor deposition method to expand the number and variety of materials other than those available in thermal ALD. The high reactivity of the plasma species at the deposition surface during PEALD has the advantage of increasing the degree of freedom of processing conditions and enabling a wider range of material properties. PEALD consists of four steps in the order of feed, 1st purge, reaction, and 2nd purge. In this reaction step, the secondary gas-phase reaction is important because the properties of the thin film vary greatly depending on the particles that arrive on the growing surface. Therefore, the particle distribution in the gas phase before arrival on the surface should be accurately predicted to estimate the film quality. Generally, the DSMC (Direct Simulation Monte Carlo) method is a commonly used method for analyzing particle distribution in the gas phase. The DSMC method requires reaction and scattering models that simulate the behavior between molecules. Variable Hard Sphere and Variable Soft Sphere are often used as the model in DSMC. These models are about molecular transport, such as molecular diffusion, and cannot deal with molecular reactions. The total collision energy model is determined for molecular reactions, but it may not accurately describe molecular reactions in non-equilibrium flow. The purpose of the study is to develop a new reaction-scattering model in non-equilibrium flow in the DSMC method for determining the particle distribution in the gas phase in the PEALD processes. Here, we focus on ammonia plasma used in the reaction step of boron nitride nanomaterial films, which are used in various applications, such as semiconductors and fine ceramics with two-dimensional and three-dimensional structures. This study focused on neutral and ionic molecules, NH3 and NH4 +, which can be the main collisional species in secondary gas-phase reactions.A molecular dynamics simulation with a reactive force field (ReaxFF) was performed. The left figure shows the simulation system of NH3 and NH4 + collisions. The periodic boundary conditions were applied to the simulation box for all directions in the size of 100 Å × 100 Å × 100 Å. Randomly oriented NH3 and NH4 + were placed in a line at an initial distance of 15 Å. NH4 + was given an electric charge of –0.22892 on N and 0.30723 on H. The initial translational energy of NH4 + was set at 5-60 eV, and the difference in the vertical coordinate at 0.1-5.0 Å. The collisions were sampled 2000 times.The right figure shows the calculated collision cross section, which determines whether a collision occurs or not. The collision coefficient bcoll represents the difference in the maximum vertical coordinate at which the absolute value of the scattering angle is greater than 1 degree. The collision cross section decreases as the translational energy increases because the negligible attraction-force act on NH3 and NH4 + at a long distance. When the translational energy exceeds 40 eV, the collisional cross-section no longer decreases and becomes asymptotic. The reason can be considered as follows. As the cross-section approaches 40 Å2, the collision cross section asymptotically approaches 40 Å2, regardless of the translational energy, because the attractive and repulsive forces are balanced. We compared our results with a reference model in grey color. In the reference model, Etr, 0 represents the minimum translational energy, σT,0 is the collision cross section at the minimum, Etr is the translational energy, and ω is a fitting parameter. Here, ω was set at –3.1. The reference model shows a good agreement with our results. However, the collision cross section is asymptotic above 40 eV, which may affect the results when the DSMC simulations are performed. We will apply the reaction scattering model to the DSMC method and analyze the gas-phase reaction of PEALD, including a comparison of the results of existing models. Figure 1

Structural and electrical correlation in aluminum nitride thin films grown by plasma enhanced atomic layer deposition as interface insulating layers on silicon carbide (4H-SiC)

(0001) oriented aluminum nitride (AlN) thin films have been grown by plasma enhanced atomic layer deposition (PE-ALD) on silicon carbide (4H-SiC) substrates. During different PE-ALD processes, the ammonia (NH3) plasma pulsing time has been varied and its effect on the microstructure and on the orientation degree of the AlN layers has been monitored. Structural characterization by Transmission Electron Microscopy (TEM) showed that the crystalline structure of the deposited films was strongly dependent on the NH3-plasma pulsing, so that different polymorphic structures were observed. In particular, both processes resulted in wurtzite AlN structure for few nanometers at the interface with the 4H-SiC substrate, while upon increasing thickness a poly-crystalline wurtzite phase was obtained by short-pulse NH3-plasma, whereas longer plasma exposure resulted in a mixture of wurtzite and zincblende defective phases. Phase formation mechanism were discussed and electrical nanoscopic characterization by conductive atomic force microscopy showed a clear correlation between the different AlN crystalline phases and the insulating properties.

Plasma-enhanced atomic layer deposition of crystalline Ga2S3 thin films

Gallium (III) sulfide is a frontrunner for many energy storage and optoelectronic applications, which demand a deposition technique that offers a high level of control over thickness, composition, and conformality. Atomic layer deposition (ALD) is a potential technique in this regard. However, the state-of-the-art ALD processes for depositing Ga2S3 often lead to films that are amorphous and nonstoichiometric, and contain significant contaminations. Herein, we present a new plasma-enhanced atomic layer deposition (PE-ALD) process using the hexakis(dimethylamido)digallium precursor and H2S plasma coreactant to deposit high-quality Ga2S3 sulfide thin films and compare it to the thermal ALD process using the same reactants. While both cases exhibit typical ALD characteristics, substantial disparity is observed in the material properties. The PE-ALD process deposits crystalline Ga2S3 sulfide thin films at a temperature as low as 125 °C with a growth per cycle of 1.71 Å/cycle. Additionally, the PE-ALD process results in smooth and stoichiometric Ga2S3 films without any detectable carbon and oxygen contamination. Grazing incidence wide-angle x-ray scattering analysis indicates that the as-deposited Ga2S3 film crystallizes in a cubic structure with a preferred orientation along the [111] direction. The Ga2S3 film exhibits a transmittance of 70% and a bandgap of 3.2 eV with a direct transition.

Interplay of Precursor and Plasma for The Deposition of HfO2 via PEALD: Film Growth and Dielectric Properties

AbstractHfO2 thin films are appealing for microelectronic applications such as high‐κ dielectric layers, memristors, and ferroelectric memory devices. To fulfill the different requirements of each application, the properties of the deposited material need to be tuned accordingly. In this context, plasma‐enhanced atomic layer deposition (PEALD) is a powerful processing route to tailor the properties of HfO2 thin films, especially at low temperatures. Herein, a comprehensive bottom‐up approach is presented, ranging from the synthesis of molecularly engineered Hf precursors to the development of a HfO2 PEALD process and a detailed evaluation where plasma can be exploited to tune the dielectric properties. With the example of the newly synthesized bis‐(dialkylamido)‐bis‐(formamidinato) Hf(IV) precursor, [Hf{η2‐(iPrN)2CH}2(NMe2)2] which is reactive, thermally robust and volatile, successful implementation in a PEALD process for HfO2 at low temperatures is demonstrated. The typical atomic layer deposition (ALD) characteristics of precursor saturation, linearity, and ALD temperature window are demonstrated with constant growth of 0.7 Å per cycle from 125 to 200 °C, yielding high‐purity layers. The effect of plasma pulse duration on the chemical composition alongside structural, topographical, as well as dielectric properties of the films is investigated. For the latter, the films are incorporated in metal‐insulator semiconductor (MIS) structures.

Effect of atomic layer annealing in plasma-enhanced atomic layer deposition of aluminum nitride on silicon

The effect of adding an atomic layer annealing step to a plasma-enhanced atomic layer deposition process of aluminum nitride was investigated with commonly available materials. The refractive index, crystallinity, stoichiometry, and impurity concentrations were studied from films grown from trimethylaluminum and ammonia precursors at 300°C on Si(111) substrates. Additional energy provided by the atomic layer annealing step during each deposition cycle was found to enhance the crystallinity and stoichiometry and increase the refractive index and film density. A polycrystalline hexagonal film with a weak c-axis orientation was obtained on substrates with and without native oxide, which is promising for applications that require high quality films at low temperatures.

Scrutinizing pre- and post-device fabrication properties of atomic layer deposition WS2 thin films

In this work, we investigate the physical and electrical properties of WS2 thin films grown by a plasma-enhanced atomic layer deposition process, both before and after device fabrication. The WS2 films were deposited on thermally oxidized silicon substrates using the W(NMe2)2(NtBu)2 precursor and a H2S plasma at 450 °C. The WS2 films were approximately 8 nm thick, measured from high-resolution cross-sectional transmission electron imaging, and generally exhibited the desired horizontal basal-plane orientation of the WS2 layers to the SiO2 surface. Hall analysis revealed a p-type behavior with a carrier concentration of 1.31 × 1017 cm−3. Temperature-dependent electrical analysis of circular transfer length method test structures, with Ni/Au contacts, yielded the activation energy (Ea) of both the specific contact resistivity and the WS2 resistivity as 100 and 91 meV, respectively. The similarity of these two values indicates that the characteristics of both are dominated by the temperature dependence of the WS2 hole concentration. Change in the material, such as in sheet resistance, due to device fabrication is attributed to the chemicals and thermal treatments associated with resist spinning and baking, ambient and UV exposure, metal deposition, and metal lift off for contact pad formation.

Atomic Layer Deposition of Ultra-Thin Crystalline Electron Channels for Heterointerface Polarization at Two-Dimensional Metal-Semiconductor Heterojunctions

Atomic layer deposition (ALD) has emerged as a promising technology for the development of the next generation of low-power semiconductor electronics. The wafer-scaled growth of two-dimensional (2D) crystalline nanostructures is a fundamental step toward the development of advanced nanofabrication technologies. Ga2O3 is an ultra-wide bandgap metal oxide semiconductor for application in electronic devices. The polymorphous Ga2O3 with its unique electronic characteristics and doping capabilities is a functional option for heterointerface engineering at metal-semiconductor 2D heterojunctions for application in nanofabrication technology. Plasma-enhanced atomic layer deposition (PE-ALD) enabled the deposition of ultra-thin nanostructures at low-growth temperatures. The present study used the PE-ALD process for the deposition of atomically thin crystalline ß-Ga2O3 films for heterointerface engineering at 2D metal-semiconductor heterojunctions. Via the control of plasma gas composition and ALD temperature, the wafer-scaled deposition of ~5.0 nm thick crystalline ß-Ga2O3 at Au/Ga2O3-TiO2 heterointerfaces was achieved. Material characterization techniques showed the effects of plasma composition and ALD temperature on the properties and structure of Ga2O3 films. The following study on the electronic characteristics of Au/Ga2O3-TiO2 2D heterojunctions confirmed the tunability of this metal/semiconductor polarized junction, which works as functional electron channel layer developed based on tunable p-n junctions at 2D metal/semiconductor interfaces.

Plasma enhanced atomic layer deposition of manganese nitride thin film from manganese amidinate and ammonia plasma

Manganese nitride films have been successfully fabricated by the technique of plasma enhanced atomic layer deposition (PEALD). The process employed bis(N,N'-di-tert-butylacetamidinate)manganese [Mn(amd)2] as manganese precursor and ammonia plasma as a coreactant. With a typical PEALD process cycle of 5 s Mn(amd)2 pulse, 10 s Ar purge pulse, 10 s NH3 plasma exposure, 10 s Ar purge pulse, 80 °C deposition temperature, and 60 W input power, the deposited film is continuous and smooth with a growth rate is 0.037 nm/cycle. Based on x-ray diffraction measurement, the film is determined to be η-Mn3N2 crystal structure. The primary deposition mechanism has been investigated by in situ optical emission spectroscopy and quartz crystal microbalance. The deposited manganese nitride film shows an excellent barrier performance against copper diffusion at insulator/copper interface.

Microkinetic based growth and property modeling of plasma enhanced atomic layer deposition silicon nitride thin film

We demonstrate a microkinetic modeling framework which is a first principle-based surface reaction thermodynamics modeling methodology to describe the plasma-enhanced atomic layer deposition process of silicon nitride thin film formation. The results illustrating the relationship between silicon nitride growth per cycle (GPC) and quasi self-limiting behavior on both dichlorosilane precursor dose amount and plasma nitridation time are consistent with the experiment. Ultimately, GPC is limited to the equivalent of a half monolayer of a Si3N4 crystalline structure. Importantly, we have observed a strong correlation between subsurface NH terminated Si group concentration and HF wet etch rate by an experiment, which varies with substrate temperature.

Study on temperature-dependent growth characteristics of germanium oxide film by plasma-enhanced atomic layer deposition

Germanium oxide (GeOx) films were grown by plasma-enhanced atomic layer deposition (PE-ALD) at 70, 130, 190 and 250 °C, using tetrakis (dimethylamino)-germanium as a precursor and O2 plasma as a reactant. For GeOx film grown at 250 °C, a relatively low growth-per-cycle (GPC) of 0.55 Å/cycle and high refractive index of 1.73 was observed as compared to the GPC and refractive index for the films grown at 70, 130, and 190 °C.Meanwhile, the areal portion of the germanium monoxide (GeO) peak to germanium dioxide (GeO2) in the Ge 3d core-level spectra of X-ray photoelectron spectroscopy increased proportional to the refractive index of the film. When estimating the mean molar mass of the GeOx films from the Lorentz-Lorenz equation, low molar mass was obtained from the GeOx film grown at 250 °C indicating germanium monoxide bond formation in the film.As the PE-ALD grown GeOx films exhibited high densities of about 3.5 g/cm3 almost close to the typical density value (3.6 ∼ 3.7 g/cm3) of germanium oxide film, low water-etch rates of 5 ∼ 10 nm/s were achieved for the PE-ALD grown GeOx films, compared to the reported etch rates of 60 ∼ 100 nm/s for germanium dioxide films. In summary, PE-ALD process for growing GeOx films has the advantage of obtaining high film density with controllable water-etch rate.

Methodology for Plasma Diagnosis and Accurate Virtual Measurement Modeling Using Optical Emission Spectroscopy

In this study, we diagnose and monitor the plasma process in real time using optical emission spectroscopy (OES). Notably, this method is inexpensive and can effectively diagnose the plasma state without plasma interference. The virtual metrology (VM) model based on machine learning can successfully predict the thickness of a ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> thin film deposited via plasma-enhanced atomic layer deposition (PE-ALD). The neural network model predicts the thickness by recording the emission light information generated during PE-ALD using OES. The prediction accuracy can be improved by including the maximum possible number of process variables, such as the radiofrequency power, pressure, and gas sensing data, in modeling. However, the complexity of the system may increase owing to the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">requirement</i> of physical knowledge on the system and result interpretation. Therefore, herein, we perform predictive modeling using variables with a high correlation and OES data, focusing on the importance of each process variable. Additionally, we use plasma data with minimized variability for variable optimization of the PE-ALD process. Consequently, we design an enhanced VM model with high prediction accuracy. The methodology adopted in this study is based on the PE-ALD process; however, it can also be extended to other processes using plasma.

Plasma-Enhanced Atomic Layer Deposition of Molybdenum Oxide Thin Films at Low Temperatures for Hydrogen Gas Sensing.

Molybdenum oxide thin films are very appealing for gas sensing applications due to their tunable material characteristics. Particularly, the growing demand for developing hydrogen sensors has triggered the exploration of functional materials such as molybdenum oxides (MoOx). Strategies to enhance the performance of MoOx-based gas sensors include nanostructured growth accompanied by precise control of composition and crystallinity. These features can be delivered by using atomic layer deposition (ALD) processing of thin films, where precursor chemistry plays an important role. Herein, we report a new plasma-enhanced ALD process for molybdenum oxide employing the molybdenum precursor [Mo(NtBu)2(tBu2DAD)] (DAD = diazadienyl) and oxygen plasma. Analysis of the film thickness reveals typical ALD characteristics such as linearity and surface saturation with a growth rate of 0.75 Å/cycle in a broad temperature window between 100 and 240 °C. While the films are amorphous at 100 °C, crystalline β-MoO3 is obtained at 240 °C. Compositional analysis reveals nearly stoichiometric and pure MoO3 films with oxygen vacancies present at the surface. Subsequently, hydrogen gas sensitivity of the molybdenum oxide thin films is demonstrated in a laboratory-scale chemiresistive hydrogen sensor setup at an operation temperature of 120 °C. Sensitivities of up to 18% are achieved for the film deposited at 240 °C, showing a strong correlation between crystallinity, oxygen vacancies at the surface, and hydrogen gas sensitivity.

InOx Doped SnO2 Nanostructure Deposited on MEMS Device by PE-ALD Process for Detection of NO2

The micro-electro-mechanical systems (MEMS) method makes the gas sensing element. The sensing layer uses RF Sputter and plasma-enhanced atomic layer deposition (PE-ALD) technology to deposit indium oxide (InOx) thin films on Tin oxide (SnO2) to form an n-n type double-layer structure. The results show that the response of SnO2-InOx and monolayer SnO2 is 153% and 55%, respectively, which is an improvement of 98% under exposure to 0.6 ppm NO2, and the sensor can obtain the best sensing at 200 °C (∼14 mW). In response, the lowest NO2 concentration was 0.2 ppm, and the selectivity test was carried out with four other gases, such as SO2, H2, CO, and NH3, and the test results showed the specificity for NO2.

Characteristics of High‐Crystallinity ZrO2 Thin Films Deposited Using Remote Plasma Atomic Layer Deposition

ZrO2 deposition using the plasma‐enhanced atomic layer deposition (PEALD) process with a cyclopentadienyl tris(dimethylamino) zirconium (CpZr(NMe2)3) precursor is investigated. The effect of deposition temperature and plasma power on ZrO2 thin films’ bonding and electrical properties is studied. CpZr(NMe2)3 is used for the deposition at 100 W and 200–400 °C and at 50–1000 W at 300 °C. When generating O2 plasma, Ar gas and O2 gas are used together to generate more radicals. It is found that CpZr(NMe2)3's PEALD process window is 200–300 °C and the film's crystallinity is strongly influenced by deposition temperature and plasma power. In both process conditions, only the tetragonal phase changes. As a result, the ZrO2 film deposited at 50 W and 300 °C has the highest dielectric constant. This is due to the higher O radical ratio that corresponds to lower plasma power. A high O radical ratio causes a chemical reaction rather than an ion bombardment.

Bottom-up plasma-enhanced atomic layer deposition of SiO2 by utilizing growth inhibition using NH3 plasma pre-treatment for seamless gap-fill process

The design-rule shrinkage in semiconductor devices is a challenge at every step of the integration process. In the gap-fill process for isolation, the seam and void formation cannot be suppressed by using a deposition process, which even has excellent step coverage. To achieve seamless gap fill in the high-aspect-ratio structure, which has a non-ideal etch profile such as a negative slope, the deposition process should be able to realize the “bottom-up growth” behavior. In this work, the bottom-up growth of a SiO2 plasma-enhanced atomic layer deposition (PE-ALD) process in a trench structure was investigated by using a growth inhibition process employing plasma treatment. N2 and NH3 plasma pre-treatments were employed to suppress the growth of the SiO2 PE-ALD process without any contamination, and the inhibition mechanism was investigated by performing surface chemistry analyses using X-ray photoelectron spectroscopy. Furthermore, the gap-fill characteristics of the SiO2 PE-ALD process were examined, depending on the process conditions of NH3 plasma pre-treatment, by performing cross-sectional field emission scanning electron microscopy measurements. Finally, a seamless gap-fill process in a high-aspect-ratio trench pattern was achieved by the bottom-up growth behavior of SiO2 PE-ALD using NH3 plasma pre-treatment.

Dopamine facilitates Al2O3 film growth on polyethylene terephthalate by low-temperature plasma-enhanced atomic layer deposition

Polymeric materials, including polyethylene terephthalate (PET), are widely used in various fields because of their beneficial properties. Functional films are deposited on these materials through different approaches, such as plasma-enhanced atomic layer deposition (PEALD), to enhance their performance and prolong their life span. However, the inert and thermally fragile nature of most polymers hinders deposition. We developed a strategy for the PEALD of nanoscale Al2O3 films on PET substrates. First, a PET substrate is subjected to alkali treatment, which gives it basic hydrophilicity for the subsequent dopamine modification. After 24 h of dopamine deposition, the substrate shows adequate active sites (phenolic hydroxyl groups), which can chemisorb large amounts of precursor during the initial deposition. The island growth mode was observed during the PEALD processes. We analyzed the detailed chemical components of Al2O3 on alkali-treated PET and dopamine-modified PET. After 100 cycles of deposition, the Al2O3 films on both samples contained much hydrogen. Benefitting from the more active sites, we observed more continuous Al2O3 film on dopamine-modified PET, which exhibited excellent water vapor blocking performance. Our findings suggest that dopamine could act as a ‘bridge’ between polymers and PEALD functional films.