Remote Plasma Atomic Layer Deposition Research Articles

Substrate Biasing during Plasma-Assisted ALD for Crystalline Phase-Control of TiO2 Thin Films

Substrate biasing has been implemented in a remote plasma atomic layer deposition (ALD) reactor, enabling control of the ion energy up to 260 eV. For TiO2 films deposited from Ti(CpMe)(NMe2)3 and O2 plasma it is demonstrated that the crystalline phase can be tailored by tuning the ion energy. Rutile TiO2 was obtained at 200 and 300°C, typically yielding amorphous and anatase films without biasing. Aspects such as film mass density, [O]/[Ti] ratio and growth per cycle under biased conditions are addressed. The results demonstrate that substrate biasing is a viable method for ALD to tailor ultra-thin film properties.

Remote Plasma ALD of SrTiO3 Using Cyclopentadienlyl-Based Ti and Sr Precursors

Remote plasma atomic layer deposition (ALD) of films with different ratios is reported, employing Star-Ti [(pentamethylcyclopentadienyl)trimethoxy-titanium, ] and Hyper-Sr [bis(trisisopropylcyclopentadienyl)-strontium with 1,2-dimethoxyethane adduct, ] precursors and plasma. The as-deposited films were amorphous, but crystallized after post-deposition anneal above . For annealed films with and a thickness of , a high dielectric constant and low leakage current of at were obtained. It is demonstrated that changes in the composition and microstructure are apparent in the optical dielectric function of the films, as obtained by spectroscopic ellipsometry.

The effects of RF power on the interfacial property between Al2O3 and Si3N4 and on the memory property in a MANOS structure

The interface stability and memory properties of an Al2O3 blocking oxide deposited using remote plasma atomic layer deposition (RPALD) at various RF powers were investigated. The plasma density increased with an increase in radio frequency (RF) power from 50 to 300 W due to increased neutral impact excitation rate. Based on x-ray photoelectron spectroscopy and auger electron spectroscopy, an oxygen-deficient interfacial layer was formed for Al2O3 film deposition at 50 W. In addition, increased migrations of Si and N atoms were observed at low power due to the formation of fewer oxygen radicals. While reduced migrations of Si and N atoms from Si3N4 to Al2O3 were observed when the RF power was sufficient due to the sufficient oxygen radicals. Therefore, the interfacial reaction between Al2O3 and Si3N4 is dependent on the RF power. After applying 18 V, the program speed of Al2O3 with 100 W, 200 W and 300 W were 10−2 s, 10−5 s and 10−6 s, respectively.

Effect of DC Bias on the Plasma Properties in Remote Plasma Atomic Layer Deposition and Its Application to HfO2 Thin Films

Direct current biased remote plasma atomic layer deposition (RPALD) was developed and applied to deposit films, and these results were compared with those of RPALD. DC biased RPALD system exhibits effective features that allow the plasma density to be controlled by dc bias. When dc bias was applied to the radio frequency (RF) plasma, the amount of free radicals and ions were increased. The electrical properties of , such as the effective oxide thickness (EOT) and the breakdown voltage, were improved by dc bias when compared to those of RPALD. This is due to the relatively high amount of free radicals controlled by dc bias.

(Invited) DC Biased Remote Plasma Atomic Layer Deposition and Its Applications

To enhance thin film quality by increasing the plasma density and minimizing plasma-induced damage, we introduced a new direct current (DC) biased remote plasma atomic layer deposition (RPALD) method as one of the variants of RPALD. With this new deposition method, HfO2 dielectric films were deposited and characterized to examine the effect of DC-bias on grown films. The plasma properties were investigated by using the optical emission spectroscopy (OES) and floating harmonic method. When DC biased was applied to the RF plasma, the amount of free radicals and ions were increased by the collisions between electrons and metastable atoms or molecules. The electrical properties of high-k materials, such as the effective oxide thickness (EOT) and the breakdown voltage, were improved by the DC biased RPALD when compared to those of RPALD.

Effects of an Al2O3 capping layer on La2O3 deposited by remote plasma atomic layer deposition

The physical and electrical properties of La2O3 with and without an Al2O3 capping layer deposited by remote plasma atomic layer deposition were investigated. The electrical properties of the La2O3 films degraded due to the formation of lanthanum hydroxide after being exposed to air. The results of x-ray photoemission spectroscopy showed that the quantity of OH groups absorbed increased after exposure to air. For La2O3 with an Al2O3 capping layer, however, the electrical properties of the film did not change substantially because the capping layer effectively suppressed the formation of lanthanum hydroxide. The capacitance of the La2O3 decreased more than 30% after exposure to air, while La2O3 with an Al2O3 capping layer decreased by only about 4%. The VFB value of the La2O3 with an Al2O3 capping layer was near zero, and the hysteresis was about 120 mV. The leakage current densities of the film were maintained below 5 × 10−7 A/cm2 up to −15 MV/cm and the effective breakdown field was about −23.5 MV/cm.

The Influence of Ions and Photons during Plasma-Assisted ALD of Metal Oxides

The influence of oxygen ions and photons during remote plasma atomic layer deposition (ALD) of metal oxide thin films was investigated for pressures of 0.5-3 Pa and plasma powers of 100-500 W. Ions have kinetic energies of ~15-35 eV and fluxes of ~10^13-10^14 cm^-2 s^-1 towards the substrate surface. The ion energy is low enough to prevent substantial ion-induced film damage, however the total energy flux provided to the substrate is sufficiently large to potentially stimulate the ALD surface reactions, e.g., through ligand desorption and adatom migration. Furthermore, it is demonstrated that the presence of VUV photons with energies of ~9.5 eV can deteriorate the electrical performance of electronic structures with ALD synthesized metal oxide films.

DC Biased Remote Plasma Atomic Layer Deposition and Its Applications

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Co3O4 as Anode Material for Thin Film μBatteries by Remote Plasma Atomic Layer Deposition

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The Effects of Annealing Ambient on the Characteristics of La2O3 Films Deposited by RPALD

We investigated the effects of different annealing ambients on the physical and electrical properties of lanthanum oxide films grown by remote plasma atomic layer deposition (RPALD). Rapid thermal annealing was carried out at for 1 min in , , and vacuum ambients. The chemical bonding states at the interface between the Si substrate and the films were analyzed using X-ray photoemission spectroscopy. The amount of OH groups that were absorbed from air in the films decreased after annealing at . and its interfacial layer were affected by the different annealing ambients. The electrical properties of the films were studied using capacitance–voltage and current–voltage plots. Without annealing treatment, the flatband voltage for the film was measured to be −0.31 eV. When was annealed at in and ambients, positive shifts of 0.16 and 0.64 eV, respectively, were observed.

Influence of annealing duration on optical property and surface morphology of ZnO thin film grown by atomic layer deposition

ZnO thin films were grown on p-Si (1 0 0) substrate by remote plasma atomic layer deposition (ALD) at 150 °C. Post-growth annealing was carried out on the ZnO thin films at 800 °C in N 2 ambient for different annealing duration. The optical property and surface morphology of annealed samples are improved significantly compared with as-grown ZnO thin film. In particularly, the ZnO thin film that annealed for 10 min has shown a great enhancement in near-band-edge emission in photoluminescence. The effect of the annealing treatment on the optical property and surface morphology of ZnO thin films were investigated by photoluminescence, atomic force microscopy and scanning electron microscopy.

Atomic Layer Deposition for All-Solid-State 3D-Integrated Batteries

All-solid-state 3D integrated batteries can reach the energy storage capacity required for future wireless devices by exploiting the third dimension. Conformal deposition techniques such as atomic layer deposition (ALD) are needed to deposit the battery materials. In this work, the current development of ALD processes for 3D integrated batteries is reviewed. We have developed both the TiN diffusion barrier and Pt cathode current collector processes. TiN showed good barrier properties in 3D, although a higher than expected charge density was observed, which could be attributed to a lower thickness and/or different material properties at the bottom of the 3D structures. The remote plasma ALD process for Pt showed fast growth initiation and good adhesion of the films. Furthermore, sufficient step coverage for the battery application was found. ALD is also potentially able to deposit the active battery layers, although the deposition of Li-containing materials is expected to be challenging.

Fabrication and Properties of AlN Film on GaN Substrate by Using Remote Plasma Atomic Layer Deposition Method

AlN films on n-type GaN (0001) were prepared using a remote-plasma atomic-layer-deposition (RPALD) technique with a trimethylaluminum(TMA) precursor and nitrogen/hydrogen, argon/hydrogen radicals ranging in temperature from room temperature (RT) to 500°C. The growth rate per cycle was varied with the substrate temperature from 2.3 A/ cycle at R. T. to 0.9 A/cycle at 500°C. X-ray diffraction results showed that the as-grown AlN films on GaN substrates had amorphous phase structures. The estimated interface trap density measured was about 2.4 × 10 /cm eV at 1.08 eV below the conduction band edge. The leakage current densities measured at room temperature was about 5 × 10 A/cm under a field of 1 MV/cm.

산화알루미늄 박막의 두께 및 열처리 온도에 따른 Al2O3/GaN MIS 구조의 전기적 특성 변화

We deposited <TEX>$Al_2O_3$</TEX> thin films on GaN by remote plasma atomic layer deposition (RPALD) technique, trimethylaluminum(TMA) and oxygen were used as precursors, at fixed process condition, the number of cycle were changed. Growth rate per cycle was <TEX>$1.2\;{\AA}$</TEX>/cycle. and Growth rate was in proportion to a number of cycle, the GaN MIS capacitors that <TEX>$Al_2O_3$</TEX> thin film were deposited above 12 nm, have excellent electrical properties, a low electrical leakage current density(<TEX>${\sim}10^{-10}\;A/cm^2$</TEX> at 1.5 MV), but below 12 nm, we can see the degradation of the leakage current density. After post deposition annealing, Dielectric constant was estimated by 1 MHz high-frequency C-V method, it was varied with the anealing temperature from 6.9 at no post anealed to 7.6 at <TEX>$800^{\circ}C$</TEX>, and we can see a improvement of the leakage current density and breakdown voltage by post deposition anealing below <TEX>$700^{\circ}C$</TEX>, but, after anealed at <TEX>$800^{\circ}C$</TEX>, we can see the degradation of the leakage current density and breakdown voltage.

원격 플라즈마 원자층 증착법을 이용한 Al2O3/GaN MIS 구조의 제작 및 전기적 특성

thin films were deposited on GaN(0001) by using a Remote Plasma Atomic Layer Deposition(RPALD) technique with a trimethylaluminum(TMA) precursor and oxygen radicals in the temperature range of . The growth rate per cycle was varied with the substrate temperature from /cycle at to /cycle at . The chemical structure of the thin films was studied using X-ray photoelectron spectroscopy(XPS). The electrical properties of /GaN Metal-Insulator-Semiconductor (MIS) capacitor grown at a process temperature were excellent, a low electrical leakage current density( at 1 MV) at room temperature and a high dielectric constant of about 7.2 with a thinner oxide thickness of 12 nm. The interface trap density() was estimated using a high-frequency C-V method measured at . These results show that the RPALD technique is an excellent choice for depositing high-quality as a Sate dielectric in GaN-based devices.

Remote Plasma ALD of Platinum and Platinum Oxide Films

Platinum and platinum oxide films were deposited by remote plasma atomic layer deposition (ALD) from the combination of (methylcyclopentadienyl)trimethylplatinum precursor and plasma. A short plasma exposure (0.5 s) resulted in low resistivity , high density , cubic Pt films, whereas a longer plasma exposure (5 s) resulted in semiconductive films. In situ spectroscopic ellipsometry studies revealed no significant nucleation delay, different from the thermal ALD process with gas which was used as a benchmark. A broad temperature window for remote plasma ALD of Pt and was demonstrated.

Characteristics of Thin Hf-Silicate Gate Dielectrics after Remote N2 and N2O Plasma Post-Treatments

We investigated the thermal stability and physical properties of nitrided Hf-silicate after applying and plasma treatments. The Hf-silicate film was created by remote-plasma atomic layer deposition using and as source gases and plasma as the oxidant. After rapid thermal annealing in ambient, the Hf silicate crystallized at , while Hf-silicate films after the and plasma treatments remained amorphous after annealing at . Remote-plasma treatment of Hf-silicate resulted in a shift of the O 1s peaks to a lower binding energy. The increase in peak intensities of the Si–O–N, Si–O–Hf, and Si–O bonds at the interface after annealing was higher after plasma treatment than after plasma treatment. The accumulation capacitances of an as-grown Hf-silicate metal-oxide-semiconductor structure after plasma treatment show that it has a better capacitance density than the same structure after plasma treatment . The equivalent oxide thickness values for the Hf-silicate films after and plasma treatments are 3.36 and , respectively.

Deposition of TiN and TaN by Remote Plasma ALD for Cu and Li Diffusion Barrier Applications

TaN and TiN films were deposited by remote plasma atomic layer deposition (ALD) using the combinations of precursor with plasma and precursor with plasma, respectively. Both the TaN and TiN films had a cubic phase composition with a relatively low resistivity (TaN: ; TiN: ). Dissimilar from the TiN properties, the material properties of the TaN films were found to depend strongly on the plasma exposure time. Preliminary tests on planar substrates were carried out revealing the potential of the TaN and TiN films as Cu and Li diffusion barriers in through-silicon via and silicon-integrated thin-film battery applications, respectively. For the specific films studied, it was found that TiN showed better barrier properties than TaN for both application areas. The TiN films were an effective barrier to Cu diffusion and had no Cu diffusion for anneal temperatures up to . The TiN films showed low Li intercalation during electrochemical charging and discharging.

Characteristics of Metal–Oxide–Semiconductor Field-Effect Transistors with HfO2/SiO2/Si and HfO2/SiOxNy/Si Stack Structures Formed by Remote Plasma Technique

Thin SiO2 and SiOxNy layers were grown on Si substrates using remote plasma oxidation and nitridation, respectively, to use as buffer layers prior to HfO2 deposition. Subsequently, HfO2 films were grown on these buffer layers by remote plasma atomic layer deposition (RPALD). The SiO2 and SiOxNy buffer layers suppressed the growth of Hf silicate at the interface during HfO2 deposition, suppressed the increase in total oxide capacitance, and induced the decrease in effective fixed oxide charge density. Metal–oxide–semiconductor field-effect transistors (MOSFETs) with buffer layers exhibited a higher drain current (Id) and effective carrier mobility (µeff) than those without buffer layers. The incorporated N atoms in SiO2 buffer layer reduced both Id and µeff of MOSFETs due to the increase of defect charge in the interfacial region, compared to SiO2 buffer layer including no N atom.

Atomic layer deposited HfO2/HfSixOyNz stacked gate dielectrics for metal-oxide-semiconductor structures

HfSi x O y N z layers were grown on Si substrates prior to HfO2 growth in order to investigate the growth of an interfacial layer between HfO2 and Si substrate and the chemical composition changes at the interfacial region. The effects of the HfSixOyNz buffer layers were also investigated. The HfSixOyNz and HfO2 films were grown by remote plasma atomic layer deposition using N2/O2 plasma and O2 plasma, respectively. The HfSixOyNz films were grown using a TDEAH precursor and N2/O2 mixed plasma. The Hf-N and N-O bonds of the HfSixOyNz layers were easily broken by annealing at 800 °C in N2 ambient because their bonds were relatively weak. The peak intensities of the Si-O-N, Hf-O-Si, and Si-O bonds at the interfacial region increased after annealing. The excess N atoms due to the breaking of the Hf-N and N-O bonds can form bonds with Si atoms in the interfacial region and cause the growth of SiOxNy or SiNx. The excess Hf and O atoms can grow HfSixOy or SiO2 due to interactions with Si atoms. The formation of the HfSixOyNz layer can suppress the growth of Hf silicate or an interfacial layer. The formation of a thick HfSixOyNz layer enhanced the thermal stability of the interfacial layer of the HfO2 film as it had a larger amount of effective fixed oxide charges than a thin HfSixOyNz layer.