Query: Plasma enhanced phase change memory

title: Control of carbon content in amorphous GeTe films deposited by plasma enhanced chemical vapor deposition (PE MOCVD) for phase change random access memory applications
abstract: Amorphous and smooth GeTe thin films are deposited on 200 mm silicon substrates by plasma enhanced metal organic chemical vapor deposition (PE MOCVD) using the commercial organometallic precursors TDMAGe and DIPTe as Ge and Te precursors, respectively. X ray photoelectron spectroscopy (XPS) measurements show a stoichiometric composition of the deposited GeTe films but with high carbon contamination. Using information collected by Optical Emission Spectroscopy (OES) and XPS, the origin of carbon contamination is determined and the dissociation mechanisms of Ge and Te precursors in H2 Ar plasma are proposed. As a result, carbon level is properly controlled by varying operating parameters such as plasma radio frequency power, pressure and H2 rate. Finally, GeTe films with carbon level as low as 5 at. are obtained.

title: Fast and scalable phase change materials Ti Sb Te deposited by plasma enhanced atomic layer deposition
abstract: Current features of phase change memory (PCM) based on Ge 2 Sb 2 Te 5 (GST) as a non volatile memory is insufficient to meet the needs of storage class memory (SCM) such as extremely high density, ultra fast operating speed and long life cycle. In this study, Ti 0.28 Sb 2 Te 3 (TST) device was fabricated based on atomic layer deposition (ALD) method and used as a phase change material. Due to the fast crystallization and low melting temperature of TST, the set speed can be reduced to 6 ns while the reset voltage can be decreased by 20% compared with GST based device with the same cell structure. In addition, the ALD deposited TST alloy showed a good gap fill capability. These results indicate that the ALD deposited TST film is a fast and scalable phase change material applied to SCM.

title: Plasma Enhanced Chemical Vapor Deposition of Conformal GeTe Layer for Phase Change Memory Applications
abstract: Phase change memory is one of the most promising technologies for the future non volatile memories generation and the synthesis of highly conformal active material is one of the main challenges. Herein, we report the successful chemical vapor deposition of phase change materials conducted using original plasma enhanced pulsed liquid injection system. Smooth, conformal and amorphous as well crystalline GeTe layers were grown on large surfaces. Their phase change characteristics present fast switch from amorphous to crystalline phases with high optical contrast between the two states. These properties are similar to those of sputtered films used in electronic devices. Moreover, thanks to appropriate process tuning, material structure and phase change properties can be tuned.

title: Phase change properties of GeSbTe thin films deposited by plasma enchanced atomic layer depositon
abstract: Phase change access memory (PCM) appears to be the strongest candidate for next generation high density nonvolatile memory. The fabrication of ultrahigh density PCM depends heavily on the thin film growth technique for the phase changing chalcogenide material. In this study, Ge2Sb2Te5 (GST) and GeSb8Te thin films were deposited by plasma enhanced atomic layer deposition (ALD) method using Ge (CH3)2 N]4, Sb (CH3)2 N]3, Te(C4H9)2 as precursors and plasma activated H2 gas as reducing agent of the metallorganic precursors. Compared with GST based device, GeSb8Te based device exhibits a faster switching speed and reduced reset voltage, which is attributed to the growth dominated crystallization mechanism of the Sb rich GeSb8Te films. These results show that ALD is an attractive method for preparation of phase change materials.

title: Phase change memory cell using Ge2Sb2Te5 and softly broken down TiO2 films for multilevel operation
abstract: A phase change memory cell was fabricated by stacking plasma enhanced cyclic chemical vapor deposited Ge2Sb2Te5 (GST) and atomic layer deposited TiO2 thin films. Different pairs of resistance states were obtained by controlling the current flow, which can be used to achieve higher memory density by multilevel operation. The multiresistance states of the stacked cell were explained by the resistance switching phenomena of TiO2 and the thermoelectric phase change properties of GST. The phase change characteristics of GST could be altered by controlling the degree of filament formation in the TiO2 layer, which eventually changed the phase change volume in the GST.

title: Electrical Characteristics of Magnesium Doped a IGZO RRAM: Chemical Vapor Deposition using Enhanced Atmospheric Pressure Plasma
abstract: Since the first floating gate memory was introduced in 1968, Non Volatile Memory (NVM) has been widely investigated and developed for permanent data storage. The progress of metal oxide semiconductor field effect transistor (MOSFET) technology even makes the memory scalable. The scale down of the memories faces other issues. The thinner oxide layer induces a higher leakage current and worse electrical characteristics. There are promising NVMs such as ferroelectric (FeRAM) phase change (PCRAM) magneto resistive (MRAM) and resistive (RRAM).In this study, RRAM devices with a metal insulator metal (MIM) structure are investigated. Amorphous indium gallium zinc oxide (a IGZO) is deposited with atmosphere pressure plasma enhanced chemical vapor deposition (AP PECVD) The resistivity of an a IGZO insulator is dominated by oxygen vacancy, and the electrical characteristics of RRAM devices are crucially influenced by the insulator layer. Magnesium (Mg) is doped into an a IGZO insulator layer to modulate the RRAM device's electrical characteristics. The results show that 1% of Mg doping makes the stability progress on devices set and read process. If more Mg is doped into a IGZO insulator layer, Mg occupies more oxygen vacancies, and RRAM devices become more unstable and unreliable.

title: New screened plasma enhanced atomic vapor deposition to improve trench covering ability of SbTe films
abstract: In this paper, a new screened plasma enhanced atomic vapor deposition technique was studied for increasing trench covering ability of Sb Te phase change film. Trench structure cells of phase change random access memory can lower thermal energy loss and thermal cross talk among adjacent memory cells. Using a plasma sheath effect with metallic mesh inside a reaction chamber, a step coverage was greatly increased in various experimental conditions. With consideration of a model of the plasma sheath, the trench covering ability of the films was evaluated and we expect this research to provide a new deposition method for the fine control of step coverage.

title: Role of hydrogen in Sb film deposition and characterization of Sb and GexSby films deposited by cyclic plasma enhanced chemical vapor deposition using metal organic precursors
abstract: To meet increasing demands for chemical vapor deposition methods for high performance phase change memory, cyclic plasma enhanced chemical vapor deposition of Sb and GexSby phase change films and characterization of their properties were performed. Two cycle sequences were designed to investigate the role of hydrogen gas as a reduction gas during Sb film deposition. Hydrogen gas was not introduced into the reaction chamber during the purge step in cycle sequence A and was introduced during the purge step for cycle sequence B. The role of hydrogen gas was investigated by comparing the results obtained from these two cycle sequences and was concluded to exert an effect by a combination of precursor decomposition, surface maintenance as a hydrogen termination agent, and surface etching. These roles of hydrogen gas are discussed through consideration of changes in deposition rates, the oxygen concentration on the surface of the Sb film, and observations of film surface morphology. Based on these results, GexSby phase change films were deposited with an adequate flow rate of hydrogen gas. The Ge and Sb composition of the film was controlled with the designed cycle sequences. A strong oxygen affinity for Ge was observed during the X ray photoelectron spectroscopy analysis of Sb 3d, Sb 4d, and Ge 3d orbitals. Based on the XPS results, the ratios of Ge to Sb were calculated to be Ge0.32Sb0.68, Ge0.38Sb0.62, Ge0.44Sb0.56, Ge0.51Sb0.49 and Ge0.67Sb0.33 for the G1S7, G1S3, G1S2, G1S1, and G2S1 cycles, respectively. Crystal structures of Sb, Ge, and the GeSb metastable phase were observed with various GexSby film compositions. Sb crystallinity decreased with respect to Ge crystallinity by increasing the Ge fraction. A current voltage curve was introduced, and an electro switching phenomenon was clearly generated at a typical voltage, Vth. Vth values increased in conjunction with an increased proportion of Ge. The Sb crystallinity decrease and Vth increase were explained via the bonding characteristics of each element.

title: A Te precursor, a Te including chalcogenide thin layer prepared by using the Te precursor, a method for preparing the thin layer and a phase change memory device
abstract: The invention tellurium (Te) containing N and Si low temperature deposition tellurium precursors, containing Te doped with N and Si produced by using this, a chalcogenide (chalcogenide) thin film, the manufacturing method and the phase change of the film It relates to a memory device. Low temperature deposition tellurium precursor according to this invention generally have the advantage of being a low temperature can be deposited during formation Te containing chalcogenide (chalcogenide) thin film doped with N and Si. In particular, wearing the tellurium precursor for low temperature deposition may utilize the PECVD (Plasma Enhanced Chemical Vapor Deposition) or PEALD (Plasma Enhanced Chemical Vapor Deposition) at low temperatures the deposition temperature. Bar, a memory device including the same that has the GST phase change film is a reduced reset current layer doped with N and Si formed using the low temperature deposition tellurium precursors become integration is possible, it is possible to high capacity and high speed operation. Tellurium precursors

title: Effect of surface temperature on GeSbTe damage formation during plasma processing
abstract: Phase Change Memory (PCM) materials can be damaged during plasma exposure leading to changes in phase transition behavior. Etch induced damage and crystallization properties of GeSbTe (GST) were evaluated as a function of substrate temperature, plasma chemistry, and plasma exposure time. Enhanced damage formation is related to selective elemental depletion and non volatilized etch residue retention in the near surface region. These experiments validate literature findings that crystallization time increases with reduction in film thickness for GST samples capped with a thin SiO2 film, indicating the presence of a modified layer which serves as an interface layer material. A direct comparison of passivating properties of hydrofluorocarbon and hydrocarbon on GST can be more conclusive with a fine tuning of film thickness and an evaluation of total residue retention with depth profiling.