Sanghyun Woo

Pt Nanocrystals Embedded in Remote Plasma Atomic-Layer-Deposited HfO2 for Nonvolatile Memory Devices

Pt nanocrystals using HfO 2 as tunneling and control layers were investigated for nonvolatile memory application. A Pt layer was deposited by electron-beam evaporation and transformed into well-separated nanocrystals by rapid thermal annealing at 700°C. The fabricated Pt nanocrystals had a density of 2.1 × 10 12 cm -2 and an average size of 3.7 nm. The capacitance-voltage measurements demonstrate that the nonvolatile memory with Pt nanocrystals had a memory effect with ∼ 0.9 V flatband voltage shift under a gate voltage of 5 V. The device showed a competitive retention characteristic with a charge loss rate of 20% after 10 4 s.

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 (La 2 O 3 ) films grown by remote plasma atomic layer deposition (RPALD). Rapid thermal annealing was carried out at 800°C for 1 min in O 2 , N 2 , and vacuum ambients. The chemical bonding states at the interface between the Si substrate and the La 2 O 3 films were analyzed using X-ray photoemission spectroscopy. The amount of OH groups that were absorbed from air in the La 2 O 3 films decreased after annealing at 800°C. La 2 O 3 and its interfacial layer were affected by the different annealing ambients. The electrical properties of the La 2 O 3 films were studied using capacitance-voltage and current-voltage plots. Without annealing treatment, the flatband voltage (V FB ) for the La 2 O 3 film was measured to be -0.31 eV. When La 2 O 3 was annealed at 800°C in N 2 and O 2 ambients, positive shifts of 0.16 and 0.64 eV, respectively, were observed.

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

This work was supported by the National Program for Tera-Level Nanodevices of the Ministry of Science and Technology of Korea as one of the 21st Century Frontier Programs.

Effect of Buffer Layer for HfO2 Gate Dielectrics Grown by Remote Plasma Atomic Layer Deposition

Three different buffer layers on a Si substrate were grown to investigate the interfacial layer effect during HfO 2 deposition and thermal annealing. The three different buffer layers were the very thin Al 2 O 3 , remote plasma nitridation (RPN)-treated Al 2 O 3 , and RPN-treated HfO 2 films. HfO 2 films were then grown on these three different buffer layers by a remote plasma atomic layer deposition method. The HfO 2 films with RPN-treated buffer layers retarded silicate formation or growth of an interfacial layer more effectively than those without RPN treatment. The HfO 2 films with an RPN-treated HfO 2 buffer layer showed the lowest effective oxide thickness and those with an RPN-treated buffer layer exhibited low leakage current density. The effective fixed-oxide charge density of the HfO 2 film with an RPN-treated HfO 2 buffer layer showed the lowest value of 3.60 X 10 11 /cm 2 compared to the other films. As the annealing temperature increased, the flatband voltage (V FB ) for the HfO 2 films was shifted and became close to the ideal V FB . The interface stability of HfO 2 with a nitrided buffer layer formed by RPN treatments resulted in the improvement of the electrical properties of HfO 2 films.

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

The physical and electrical properties of La 2 O 3 with and without an Al 2 O 3 capping layer deposited by remote plasma atomic layer deposition were investigated. The electrical properties of the La 2 O 3 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 La 2 O 3 with an Al 2 O 3 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 La 2 O 3 decreased more than 30% after exposure to air, while La 2 O 3 with an Al 2 O 3 capping layer decreased by only about 4%. The V FB value of the La 2 O 3 with an Al 2 O 3 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/cm 2 up to −15 MV/cm and the effective breakdown field was about −23.5 MV/cm.

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

HfSixOyNz 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 H...

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.

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.

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 N 2 and N 2 O plasma treatments. The Hf-silicate film was created by remote-plasma atomic layer deposition using Hf[N(CH 3 )C 2 H 5 ] 4 and Si[N(CH 3 )] 3 H as source gases and O 2 plasma as the oxidant. After rapid thermal annealing in N 2 ambient, the Hf silicate crystallized at 800°C, while Hf-silicate films after the N 2 and N 2 O plasma treatments remained amorphous after annealing at 800°C. 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 N 2 O plasma treatment than after N 2 plasma treatment. The accumulation capacitances of an as-grown Hf-silicate metal-oxide-semiconductor structure after N 2 plasma treatment show that it has a better capacitance density (280 pF) than the same structure after N 2 O plasma treatment (235 pF). The equivalent oxide thickness values for the Hf-silicate films after N 2 and N 2 O plasma treatments are 3.36 and 3.8 nm, respectively.

Low Resistive and Uniform CoSi2 Formation with Ti Capping Layer

We have examined the interface morphologies CoSi2 layer after Co films deposition with and without Ti capping layer followed by RTA. In the case of Co film without Ti capping layer, the interface between CoSi2 and Si substrate exhibited significantly rough and wavy morphology. On the other hand, CoSi2 layer with Ti capping layer, showed a relatively smooth and uniform surface and interface morphologies. Therefore, the surface and interface roughness of CoSi2 layer were improved by Ti capping layer. This smooth CoSi2 layer can improve the contact resistance and the thermal stability for applications in ultra‐large‐scale integration (ULSI) devices.