Albena Paskaleva - Academia.edu (original) (raw)
Papers by Albena Paskaleva
Journal of Physics D: Applied Physics, May 18, 2011
The electrical behaviour of Al-doped Ta2O5 films on nitrided silicon and implemented in Al-gated ... more The electrical behaviour of Al-doped Ta2O5 films on nitrided silicon and implemented in Al-gated MIS capacitors has been studied. The dopant was introduced into the Ta2O5 through its surface by deposing a thin Al layer on the top of Ta2O5 followed by an annealing process. The HRTEM images reveal that the initial double-layer structure of the stacks composed of doped Ta2O5 and interfacial SiON layer undergoes changes during the formation of the Al gate and transforms into a three-layer structure with an additional layer ...
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2013
Microelectronics Reliability, 2005
Electrical behavior of high-k HfxTiySizO layers with different Hf:Ti ratios in the film have been... more Electrical behavior of high-k HfxTiySizO layers with different Hf:Ti ratios in the film have been investigated. The films are prepared by MOCVD using novel single-source precursors chemistry. Oxide and interface charges, leakage currents and conduction mechanisms are found to be a strong function of the film composition. The films with lower Hf content show lower level of oxide and interface
Journal of Applied Physics, 2009
The capacitance behavior of metal insulator metal (MIM) structures with Zr1−xAlxO2 dielectrics an... more The capacitance behavior of metal insulator metal (MIM) structures with Zr1−xAlxO2 dielectrics and TiN metal electrodes is analyzed. The capacitance nonlinearity, the dielectric relaxation, and the loss phenomena are found to depend strongly on the Al content, the dielectric thickness, and the amorphous/crystalline phase of the dielectric layer. Two different kinds of phenomena—crystallization-related and interface-related, are considered to explain the
Vacuum, 2000
The leakage current and the conduction mechanisms in Ta O layers on silicon with thickness in the... more The leakage current and the conduction mechanisms in Ta O layers on silicon with thickness in the range of 20}80 nm, obtained by reactive sputtering of Ta in an Ar/O mixture have been investigated. Some dielectric and electrical properties, important for the application of the layers as storage capacitors in high-density dynamic random access memories (DRAM) and as a gate dielectric in metal oxide silicon transistors (MOSTs) are also considered. The results show that for as-deposited layers the leakage currents are higher for samples obtained at higher deposition temperature. The e!ect of postdeposition oxygen annealing depends on the thickness of Ta O layers. For thicker layers (40 nm), the leakage current after annealing increases and the e!ect is stronger for layers deposited at T "493 K. It has been established that for thinner oxides (25 nm) the annealing strongly improves the leakage currents (the density of leakage current is 10\ A/cm at applied "elds of about 1 MV/cm, which is low enough to satisfy the demands of 64 and 256 Mbit DRAM). For as-deposited samples the conduction mechanism is Poole Frenkel. After annealing depending on the "eld strength, di!erent types of conduction mechanisms occur: for electric "elds in the range 0.8}1.3 MV/cm, the conduction mechanism is dominated by electrode limited Schottky emission and for higher "elds ('1.5 MV/cm) it is bulk limited Poole Frenkel emission. The results are discussed in terms of bulk traps in the initial Ta O and their modi"cation after oxygen annealing.
ACS Applied Materials & Interfaces, 2015
In this work dielectric and electrical properties of Al-doped HfO2 layers deposited by plasma-enh... more In this work dielectric and electrical properties of Al-doped HfO2 layers deposited by plasma-enhanced atomic layer deposition in dependence on the thickness and the added Al amount in the films have been investigated. Special attention is dedicated to C-V and I-V hysteresis analysis as a measure for trapping phenomena in the films. A detailed study of conduction mechanisms in dependence on the composition of the layers has also been performed. The densities and spatial and energy positions of traps have been examined. It is found that only a small amount of Al-doping decreases the trapping which is assigned to a reduction of oxygen vacancy-related traps in HfO2. On the contrary, higher amounts of Al introduced in HfO2 films increase the trapping ability of the stacks which is due to the introduction of deeper Al2O3-related traps. The results imply that by adding a proper amount of Al into HfO2 it is possible to tailor dielectric and electrical properties of high-k layers toward meeting the criteria for particular applications.
ACS applied materials & interfaces, Jan 12, 2015
In this work dielectric and electrical properties of Al-doped HfO2 layers deposited by plasma-enh... more In this work dielectric and electrical properties of Al-doped HfO2 layers deposited by plasma-enhanced atomic layer deposition in dependence on the thickness and the added Al amount in the films have been investigated. Special attention is dedicated to C-V and I-V hysteresis analysis as a measure for trapping phenomena in the films. A detailed study of conduction mechanisms in dependence on the composition of the layers has also been performed. The densities and spatial and energy positions of traps have been examined. It is found that only a small amount of Al-doping decreases the trapping which is assigned to a reduction of oxygen vacancy-related traps in HfO2. On the contrary, higher amounts of Al introduced in HfO2 films increase the trapping ability of the stacks which is due to the introduction of deeper Al2O3-related traps. The results imply that by adding a proper amount of Al into HfO2 it is possible to tailor dielectric and electrical properties of high-k layers toward mee...
Journal of IMAB - Annual Proceeding (Scientific Papers), 2010
2008 International Conference on Advanced Semiconductor Devices and Microsystems, 2008
Electrical properties of metal-oxide-semiconductor structures composed of MOCVD grown Ru or RuO2 ... more Electrical properties of metal-oxide-semiconductor structures composed of MOCVD grown Ru or RuO2 metal gates, rf sputtered Ta2O5 oxide layers, and nitrided Si was investigated. The dielectric constant of Ta2O5 as extracted from capacitance-voltage characteristics was found to be 24 and 28 for Ru and RuO2 gated structures, respectively. Interfacial SiO2-like layer with a thickness of ~2 nm was observed from
Microelectronics Reliability, 2005
... Martin Lemberger a , Corresponding Author Contact Information , E-mail The Corresponding Auth... more ... Martin Lemberger a , Corresponding Author Contact Information , E-mail The Corresponding Author , Albena Paskaleva b , Stefan Zürcher c , Anton J. Bauer b , Lothar Frey a , b and Heiner Ryssel a , b. ... (c) FowlerNordheim plot of obtained JV traces. ...
Solid-State Electronics, 2002
The effect of oxygen annealing at high temperature (873, 1123 K; 30 min) on the insulating proper... more The effect of oxygen annealing at high temperature (873, 1123 K; 30 min) on the insulating properties and conduction mechanism of rf sputtered Ta 2 O 5 (25-80 nm) on Si has been investigated. It is found that the oxygen heating significantly reduces the oxide charge (Q f < 10 10 cm À2 ) and improves the breakdown characteristics (the effect is more pronounced for the higher annealing temperature). It is accompanied by an increase of the effective dielectric constant (up to 37 after 1123 K treatment). It is established that the influence of the oxygen treatment on the leakage current is different depending on the film thickness, namely: a beneficial effect for the thinner and a deterioration of leakage characteristics for thicker (80 nm) films. A leakage current density as low as 10 À7 A/cm 2 at 1 MV/cm applied field for 26 nm annealed layers has been obtained. The current reduction is considered to be due to a removal by annealing of certain structural nonperfections present in the initial layers. Generally, the results are discussed in terms of simultaneous action of two opposite and competing processes taking place at high temperatures--a real annealing of defects and an appearance of a crystal phase and/or a neutral traps generation. The contribution of the neutral traps also is involved to explain the observed weaker charge trapping in the as-fabricated films compared to the annealed ones.
Vacuum, 2003
Vacuum-deposited polyimide (PI) thin films have been prepared by co-deposition of precursor pyrom... more Vacuum-deposited polyimide (PI) thin films have been prepared by co-deposition of precursor pyromellitic dianhydride (PMDA) and 4,4 0 -oxydianiline (ODA) followed by thermal treatment. The dependency of the optical and electrical properties, chemical resistivity and mechanical stability on the composition (ODA:PMDA) and the degree of imidization of the PI layers have been investigated and discussed. The experimental results have yielded possibilities to microstructure the vacuum-deposited PI films by excimer laser irradiation or reactive ion etching in gas mixture CF 4 /O 2 .
Dielectrics for Nanosystems 4: Materials Science, Processing, Reliability, and Manufacturing, 2010
ABSTRACT The use of scanning probe microscopy (SPM) techniques for the electrical characterizatio... more ABSTRACT The use of scanning probe microscopy (SPM) techniques for the electrical characterization of high-k dielectric layers is reviewed, focusing on conductive atomic force microscopy (cAFM) and scanning capacitance microscopy (SCM). It is demonstrated exemplarily for ZrO2 high-k layer stacks that cAFM enables a detailed analysis of the morphological and electrical layer characteristics. Film morphologies can be determined even for surfaces where topography mapping can not detect distinct surface roughness like grain structures. For as-deposited amorphous layers, the current distribution is random whereas increased leakage currents at grain boundaries can be observed for nano-crystalline samples. The dominant current mechanisms through the layers can be determined from current voltage curves at distinct local points. Comparison with conventional techniques proofs the findings by cAFM. The quantitative interpretation of SCM measurement results often suffers from parasitic capacitances and light induced effects. Local thickness variation of dielectrics, however, can be detected very sensitively.
Facta universitatis - series: Electronics and Energetics, 2014
A compact model of a MOS capacitor with high-k HfO2-Ta2O5 mixed layer stack is developed in Matla... more A compact model of a MOS capacitor with high-k HfO2-Ta2O5 mixed layer stack is developed in Matlab. Model equations are based on the surface potential description of PSP model. After fitting the C-V characteristics in Matlab the model is coded in Verilog-A hardware description language to interface with Spectre circuit simulator within Cadence CAD system. The results are validated against experimental measurements of high-k dielectric structure.
Vacuum, 1996
The development of modern microelectronics produces a need to develop materials with a relative d... more The development of modern microelectronics produces a need to develop materials with a relative dielectric constant ϵr, lower than that of silicon dioxide for intermetal applications. Lower permittivities mean lower capacitances and therefore shorter RC delay, faster device speeds, less crosstalk and less power dissipation. A promising “tailor made” candidate is the evaporated polymer-polyimide. The dielectric properties of evaporated polyimide
Thin Solid Films, 2008
Ti-doped Ta 2 O 5 (∼10; 30 nm) obtained by sputtering was studied with respect to their dielectri... more Ti-doped Ta 2 O 5 (∼10; 30 nm) obtained by sputtering was studied with respect to their dielectric and electrical properties. The incorporation of Ti was performed by two original methodssurface doping where Ti layer was deposited on the top of Ta 2 O 5 and bulk doping where the layer was embedded inside the Ta 2 O 5 . The surface doping is worthy for thin-and the bulk doping is more beneficial for thick film stacks, (the current lowers with ∼1-2 orders of magnitude). In the context of advanced high-k dielectrics (thinner layers) the surface-doped Ta 2 O 5 has better potential. The incorporation of Ti into Ta 2 O 5 causes generation of negative oxide charge. The mechanism of current reduction is considered to be due to Ti-induced compensation of existing oxygen vacancies.
Semiconductor Science and Technology, 2010
Leakage conduction mechanisms in Ru/Ta2O5/SiON/Si structures with rf-sputtered Ta2O5 with thickne... more Leakage conduction mechanisms in Ru/Ta2O5/SiON/Si structures with rf-sputtered Ta2O5 with thicknesses ranging from 13.5 to 1.8 nm were systematically studied. Notable reaction at the Ru/Ta2O5 interface was revealed by capacitance-voltage measurements. Temperature-dependent current-voltage characteristics suggest the bulk-limited conduction mechanism in all metal-oxide-semiconductor structures. Under gate injection, Poole-Frenkel emission was identified as a dominant mechanism for 13.5 nm thick Ta2O5. With
Semiconductor Science and Technology, 2005
Abstract. Dielectric properties, including leakage currents of stacked structures composed of rf ... more Abstract. Dielectric properties, including leakage currents of stacked structures composed of rf sputtered Ta 2 O 5 and ultrathin SiO x N y grown by rapid thermal nitridation (RTN) in N 2 O or NH 3 ambient, have been investigated. It was previously established that the leakage current in the structures is controlled by both hopping conduction and tunnelling in the SiO x N y layer and Poole-Frenkel emission in Ta 2 O 5. The analysis shows that the RTN in N 2 O gives higher barriers, lower SiO x N y layer thickness and lower permittivity than in NH 3. It ...
Microelectronics Reliability, 2007
The effect of various electrodes (Al, W, TiN) deposited by evaporation (Al) and sputtering (W, Ti... more The effect of various electrodes (Al, W, TiN) deposited by evaporation (Al) and sputtering (W, TiN) on the electrical characteristics of Ta 2 O 5 stack capacitors has been investigated. The leakage currents, breakdown fields, mechanism of conductivity and dielectric constant are discussed in the terms of possible reactions between Ta 2 O 5 and electrode material as well as electrode-deposition-process-induced defects acting as electrically active centers. During deposition of TiN and Al a reaction that worsens the properties of Ta 2 O 5 occurs while there is not an indication for detectable reduction of Ta 2 O 5 when top electrode is W. The sputtered W top electrode is a good candidate as a gate of storage capacitors in DRAMs, but sputtering technique is less suitable for deposition of TiN due to the introduction of radiation defects causing deterioration of leakage current. Although some reaction between Al and Ta 2 O 5 occurs, the resulting electrical properties of the capacitors are still acceptable.
Journal of Physics D: Applied Physics, May 18, 2011
The electrical behaviour of Al-doped Ta2O5 films on nitrided silicon and implemented in Al-gated ... more The electrical behaviour of Al-doped Ta2O5 films on nitrided silicon and implemented in Al-gated MIS capacitors has been studied. The dopant was introduced into the Ta2O5 through its surface by deposing a thin Al layer on the top of Ta2O5 followed by an annealing process. The HRTEM images reveal that the initial double-layer structure of the stacks composed of doped Ta2O5 and interfacial SiON layer undergoes changes during the formation of the Al gate and transforms into a three-layer structure with an additional layer ...
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2013
Microelectronics Reliability, 2005
Electrical behavior of high-k HfxTiySizO layers with different Hf:Ti ratios in the film have been... more Electrical behavior of high-k HfxTiySizO layers with different Hf:Ti ratios in the film have been investigated. The films are prepared by MOCVD using novel single-source precursors chemistry. Oxide and interface charges, leakage currents and conduction mechanisms are found to be a strong function of the film composition. The films with lower Hf content show lower level of oxide and interface
Journal of Applied Physics, 2009
The capacitance behavior of metal insulator metal (MIM) structures with Zr1−xAlxO2 dielectrics an... more The capacitance behavior of metal insulator metal (MIM) structures with Zr1−xAlxO2 dielectrics and TiN metal electrodes is analyzed. The capacitance nonlinearity, the dielectric relaxation, and the loss phenomena are found to depend strongly on the Al content, the dielectric thickness, and the amorphous/crystalline phase of the dielectric layer. Two different kinds of phenomena—crystallization-related and interface-related, are considered to explain the
Vacuum, 2000
The leakage current and the conduction mechanisms in Ta O layers on silicon with thickness in the... more The leakage current and the conduction mechanisms in Ta O layers on silicon with thickness in the range of 20}80 nm, obtained by reactive sputtering of Ta in an Ar/O mixture have been investigated. Some dielectric and electrical properties, important for the application of the layers as storage capacitors in high-density dynamic random access memories (DRAM) and as a gate dielectric in metal oxide silicon transistors (MOSTs) are also considered. The results show that for as-deposited layers the leakage currents are higher for samples obtained at higher deposition temperature. The e!ect of postdeposition oxygen annealing depends on the thickness of Ta O layers. For thicker layers (40 nm), the leakage current after annealing increases and the e!ect is stronger for layers deposited at T "493 K. It has been established that for thinner oxides (25 nm) the annealing strongly improves the leakage currents (the density of leakage current is 10\ A/cm at applied "elds of about 1 MV/cm, which is low enough to satisfy the demands of 64 and 256 Mbit DRAM). For as-deposited samples the conduction mechanism is Poole Frenkel. After annealing depending on the "eld strength, di!erent types of conduction mechanisms occur: for electric "elds in the range 0.8}1.3 MV/cm, the conduction mechanism is dominated by electrode limited Schottky emission and for higher "elds ('1.5 MV/cm) it is bulk limited Poole Frenkel emission. The results are discussed in terms of bulk traps in the initial Ta O and their modi"cation after oxygen annealing.
ACS Applied Materials & Interfaces, 2015
In this work dielectric and electrical properties of Al-doped HfO2 layers deposited by plasma-enh... more In this work dielectric and electrical properties of Al-doped HfO2 layers deposited by plasma-enhanced atomic layer deposition in dependence on the thickness and the added Al amount in the films have been investigated. Special attention is dedicated to C-V and I-V hysteresis analysis as a measure for trapping phenomena in the films. A detailed study of conduction mechanisms in dependence on the composition of the layers has also been performed. The densities and spatial and energy positions of traps have been examined. It is found that only a small amount of Al-doping decreases the trapping which is assigned to a reduction of oxygen vacancy-related traps in HfO2. On the contrary, higher amounts of Al introduced in HfO2 films increase the trapping ability of the stacks which is due to the introduction of deeper Al2O3-related traps. The results imply that by adding a proper amount of Al into HfO2 it is possible to tailor dielectric and electrical properties of high-k layers toward meeting the criteria for particular applications.
ACS applied materials & interfaces, Jan 12, 2015
In this work dielectric and electrical properties of Al-doped HfO2 layers deposited by plasma-enh... more In this work dielectric and electrical properties of Al-doped HfO2 layers deposited by plasma-enhanced atomic layer deposition in dependence on the thickness and the added Al amount in the films have been investigated. Special attention is dedicated to C-V and I-V hysteresis analysis as a measure for trapping phenomena in the films. A detailed study of conduction mechanisms in dependence on the composition of the layers has also been performed. The densities and spatial and energy positions of traps have been examined. It is found that only a small amount of Al-doping decreases the trapping which is assigned to a reduction of oxygen vacancy-related traps in HfO2. On the contrary, higher amounts of Al introduced in HfO2 films increase the trapping ability of the stacks which is due to the introduction of deeper Al2O3-related traps. The results imply that by adding a proper amount of Al into HfO2 it is possible to tailor dielectric and electrical properties of high-k layers toward mee...
Journal of IMAB - Annual Proceeding (Scientific Papers), 2010
2008 International Conference on Advanced Semiconductor Devices and Microsystems, 2008
Electrical properties of metal-oxide-semiconductor structures composed of MOCVD grown Ru or RuO2 ... more Electrical properties of metal-oxide-semiconductor structures composed of MOCVD grown Ru or RuO2 metal gates, rf sputtered Ta2O5 oxide layers, and nitrided Si was investigated. The dielectric constant of Ta2O5 as extracted from capacitance-voltage characteristics was found to be 24 and 28 for Ru and RuO2 gated structures, respectively. Interfacial SiO2-like layer with a thickness of ~2 nm was observed from
Microelectronics Reliability, 2005
... Martin Lemberger a , Corresponding Author Contact Information , E-mail The Corresponding Auth... more ... Martin Lemberger a , Corresponding Author Contact Information , E-mail The Corresponding Author , Albena Paskaleva b , Stefan Zürcher c , Anton J. Bauer b , Lothar Frey a , b and Heiner Ryssel a , b. ... (c) FowlerNordheim plot of obtained JV traces. ...
Solid-State Electronics, 2002
The effect of oxygen annealing at high temperature (873, 1123 K; 30 min) on the insulating proper... more The effect of oxygen annealing at high temperature (873, 1123 K; 30 min) on the insulating properties and conduction mechanism of rf sputtered Ta 2 O 5 (25-80 nm) on Si has been investigated. It is found that the oxygen heating significantly reduces the oxide charge (Q f < 10 10 cm À2 ) and improves the breakdown characteristics (the effect is more pronounced for the higher annealing temperature). It is accompanied by an increase of the effective dielectric constant (up to 37 after 1123 K treatment). It is established that the influence of the oxygen treatment on the leakage current is different depending on the film thickness, namely: a beneficial effect for the thinner and a deterioration of leakage characteristics for thicker (80 nm) films. A leakage current density as low as 10 À7 A/cm 2 at 1 MV/cm applied field for 26 nm annealed layers has been obtained. The current reduction is considered to be due to a removal by annealing of certain structural nonperfections present in the initial layers. Generally, the results are discussed in terms of simultaneous action of two opposite and competing processes taking place at high temperatures--a real annealing of defects and an appearance of a crystal phase and/or a neutral traps generation. The contribution of the neutral traps also is involved to explain the observed weaker charge trapping in the as-fabricated films compared to the annealed ones.
Vacuum, 2003
Vacuum-deposited polyimide (PI) thin films have been prepared by co-deposition of precursor pyrom... more Vacuum-deposited polyimide (PI) thin films have been prepared by co-deposition of precursor pyromellitic dianhydride (PMDA) and 4,4 0 -oxydianiline (ODA) followed by thermal treatment. The dependency of the optical and electrical properties, chemical resistivity and mechanical stability on the composition (ODA:PMDA) and the degree of imidization of the PI layers have been investigated and discussed. The experimental results have yielded possibilities to microstructure the vacuum-deposited PI films by excimer laser irradiation or reactive ion etching in gas mixture CF 4 /O 2 .
Dielectrics for Nanosystems 4: Materials Science, Processing, Reliability, and Manufacturing, 2010
ABSTRACT The use of scanning probe microscopy (SPM) techniques for the electrical characterizatio... more ABSTRACT The use of scanning probe microscopy (SPM) techniques for the electrical characterization of high-k dielectric layers is reviewed, focusing on conductive atomic force microscopy (cAFM) and scanning capacitance microscopy (SCM). It is demonstrated exemplarily for ZrO2 high-k layer stacks that cAFM enables a detailed analysis of the morphological and electrical layer characteristics. Film morphologies can be determined even for surfaces where topography mapping can not detect distinct surface roughness like grain structures. For as-deposited amorphous layers, the current distribution is random whereas increased leakage currents at grain boundaries can be observed for nano-crystalline samples. The dominant current mechanisms through the layers can be determined from current voltage curves at distinct local points. Comparison with conventional techniques proofs the findings by cAFM. The quantitative interpretation of SCM measurement results often suffers from parasitic capacitances and light induced effects. Local thickness variation of dielectrics, however, can be detected very sensitively.
Facta universitatis - series: Electronics and Energetics, 2014
A compact model of a MOS capacitor with high-k HfO2-Ta2O5 mixed layer stack is developed in Matla... more A compact model of a MOS capacitor with high-k HfO2-Ta2O5 mixed layer stack is developed in Matlab. Model equations are based on the surface potential description of PSP model. After fitting the C-V characteristics in Matlab the model is coded in Verilog-A hardware description language to interface with Spectre circuit simulator within Cadence CAD system. The results are validated against experimental measurements of high-k dielectric structure.
Vacuum, 1996
The development of modern microelectronics produces a need to develop materials with a relative d... more The development of modern microelectronics produces a need to develop materials with a relative dielectric constant ϵr, lower than that of silicon dioxide for intermetal applications. Lower permittivities mean lower capacitances and therefore shorter RC delay, faster device speeds, less crosstalk and less power dissipation. A promising “tailor made” candidate is the evaporated polymer-polyimide. The dielectric properties of evaporated polyimide
Thin Solid Films, 2008
Ti-doped Ta 2 O 5 (∼10; 30 nm) obtained by sputtering was studied with respect to their dielectri... more Ti-doped Ta 2 O 5 (∼10; 30 nm) obtained by sputtering was studied with respect to their dielectric and electrical properties. The incorporation of Ti was performed by two original methodssurface doping where Ti layer was deposited on the top of Ta 2 O 5 and bulk doping where the layer was embedded inside the Ta 2 O 5 . The surface doping is worthy for thin-and the bulk doping is more beneficial for thick film stacks, (the current lowers with ∼1-2 orders of magnitude). In the context of advanced high-k dielectrics (thinner layers) the surface-doped Ta 2 O 5 has better potential. The incorporation of Ti into Ta 2 O 5 causes generation of negative oxide charge. The mechanism of current reduction is considered to be due to Ti-induced compensation of existing oxygen vacancies.
Semiconductor Science and Technology, 2010
Leakage conduction mechanisms in Ru/Ta2O5/SiON/Si structures with rf-sputtered Ta2O5 with thickne... more Leakage conduction mechanisms in Ru/Ta2O5/SiON/Si structures with rf-sputtered Ta2O5 with thicknesses ranging from 13.5 to 1.8 nm were systematically studied. Notable reaction at the Ru/Ta2O5 interface was revealed by capacitance-voltage measurements. Temperature-dependent current-voltage characteristics suggest the bulk-limited conduction mechanism in all metal-oxide-semiconductor structures. Under gate injection, Poole-Frenkel emission was identified as a dominant mechanism for 13.5 nm thick Ta2O5. With
Semiconductor Science and Technology, 2005
Abstract. Dielectric properties, including leakage currents of stacked structures composed of rf ... more Abstract. Dielectric properties, including leakage currents of stacked structures composed of rf sputtered Ta 2 O 5 and ultrathin SiO x N y grown by rapid thermal nitridation (RTN) in N 2 O or NH 3 ambient, have been investigated. It was previously established that the leakage current in the structures is controlled by both hopping conduction and tunnelling in the SiO x N y layer and Poole-Frenkel emission in Ta 2 O 5. The analysis shows that the RTN in N 2 O gives higher barriers, lower SiO x N y layer thickness and lower permittivity than in NH 3. It ...
Microelectronics Reliability, 2007
The effect of various electrodes (Al, W, TiN) deposited by evaporation (Al) and sputtering (W, Ti... more The effect of various electrodes (Al, W, TiN) deposited by evaporation (Al) and sputtering (W, TiN) on the electrical characteristics of Ta 2 O 5 stack capacitors has been investigated. The leakage currents, breakdown fields, mechanism of conductivity and dielectric constant are discussed in the terms of possible reactions between Ta 2 O 5 and electrode material as well as electrode-deposition-process-induced defects acting as electrically active centers. During deposition of TiN and Al a reaction that worsens the properties of Ta 2 O 5 occurs while there is not an indication for detectable reduction of Ta 2 O 5 when top electrode is W. The sputtered W top electrode is a good candidate as a gate of storage capacitors in DRAMs, but sputtering technique is less suitable for deposition of TiN due to the introduction of radiation defects causing deterioration of leakage current. Although some reaction between Al and Ta 2 O 5 occurs, the resulting electrical properties of the capacitors are still acceptable.