Quantitative electron probe microanalysis of highly insulating materials is a complicated problem... more Quantitative electron probe microanalysis of highly insulating materials is a complicated problem, partially solved by coating samples with grounded thin conductive layers or using novel scanning electron microscopy (SEM) techniques, such as lowvoltage and=or variable pressure SEM. In this work, some problems of quantitative X-ray microanalysis of thin HfO 2 films, in particular the possibility to determine mass thickness correlated to the density of the layer material, are discussed. For comparison, Al 2 O 3 , Ta 2 O 5 and TiO 2 films grown onto both semiconductive Si and insulating quartz substrates were also analysed. All the films studied were synthesized by atomic layer deposition method.
Carbon nanoparticles were synthesized from 5-methylresorcinol and formaldehyde via base catalysed... more Carbon nanoparticles were synthesized from 5-methylresorcinol and formaldehyde via base catalysed polycondensation reaction and distributed over silicon oxide wafers and aluminium oxide thin films. These particles essentially possessed monocrystalline graphite structure. The particles were covered by hafnium oxide thin films in metal chloride based atomic layer deposition process carried out at 300°C. Upon deposition of HfO 2 , thin crystalline metal oxide layer containing mostly cubic phase was formed. At the same time, deposition of the metal oxide caused reduction of the sizes of graphite particles and essential increase in the disorder in carbon.
Atomic layer deposition of ZrO 2 films from tris(dimethylamino)cyclopentadienylzirconium CpZr(NMe... more Atomic layer deposition of ZrO 2 films from tris(dimethylamino)cyclopentadienylzirconium CpZr(NMe 2 ) 3 and H 2 O, was investigated using real-time characterization of the growth process and post-growth measurements of the films. Self-limited nature of the deposition process was observed at substrate temperatures ranging from 120 to 350°C. In this temperature range growth rate of 0.08-0.1 nm per cycle was obtained on silicon substrates. The films deposited on silicon substrates at 200°C and higher temperatures contained tetragonal and monoclinic phases of ZrO 2 . The phase composition of the films depended on the deposition temperature as well as on the film thickness. The concentration of carbon residues decreased with increasing deposition temperature and did not exceed 0.9 at.% in the films deposited at 250°C and higher temperatures. The refractive indices and densities of films grown from CpZr(NMe 2 ) 3 and H 2 O at 250-350°C ranged from 2.15 to 2.20 (at a wavelength of 633 nm) and 5.6 to 6.0 g/cm 3 , respectively, being close to the highest values obtained for films deposited from ZrCl 4 and H 2 O. The former process ensured, however, more uniform nucleation of ZrO 2 on graphene than the latter process did.
This work explores the electrical properties of Al 2 O 3 films formed by atomic layer deposition ... more This work explores the electrical properties of Al 2 O 3 films formed by atomic layer deposition (ALD) using different oxygen sources (water and ozone) and trimethylaluminium (TMA). The as-deposited Al 2 O 3 layers were used as blocking oxides in metal (Pt)-alumina-nitride-oxide-silicon memory capacitors. The capacitance-voltage characteristics of the devices with Al 2 O 3 deposited with the ozone-TMA and water-TMA processes showed almost identical capacitance equivalent thicknesses in accordance with transmission electron microscopy imaging which revealed similar dielectric layer thicknesses between the two gate stacks. At high negative gate voltages the water-TMA devices exhibited higher leakage currents than the ozone-TMA devices. This effect had a direct impact on the attainable memory window, due to the limited erase performance of the capacitors and the extended erase-saturation effect. These findings indicate that the ALD chemistry and in particular the oxygen source is a crucial factor which determines the electrical behavior of the as-deposited Al 2 O 3 films, and therefore the performance of the memory stacks. These differences are attributed to the different trap distributions either in space or energy within the Al 2 O 3 layers.
In this work, we examine the influence of hafnium and zirconium oxides ALD precursor chemistry on... more In this work, we examine the influence of hafnium and zirconium oxides ALD precursor chemistry on the memory properties of SiO 2 /Si 3 N 4 /ZrO 2 and SiO 2 /Si 3 N 4 /HfO 2 non-volatile gate memory stacks. Approximately 10 nm thick ZrO 2 and HfO 2 layers were deposited on top of a SiO 2 /Si 3 N 4 structure, functioning as blocking oxides. Both metal oxides were deposited using either alkylamides or cyclopentadienyls as metal precursors, and ozone as the oxygen source. In the case of the ZrO 2 gate stacks a memory window of 6 V was determined, comprised of 4 V write window and 2 V erase window. Although no dramatic/major differences were evident between the ZrO 2 layers, ZrO 2 grown from alkylamide provided structures with higher dielectric strength. The memory structures with HfO 2 blocking layers indicate that the memory window and the dielectric strength are significantly affected by the precursor. The structures with the HfO 2 formed from alkylamide showed a write window of 7 V, while the films grown from cyclopentadienyl possessed window of 5 V. Comparison between the memory windows obtained using ZrO 2 and HfO 2 as control oxides reveals that the former provides memory structures with higher electron trapping efficiency.
In this work we report the performance of the SiO 2 /Si 3 N 4 /HfO 2 and SiO 2 /Si 3 N 4 /ZrO 2 s... more In this work we report the performance of the SiO 2 /Si 3 N 4 /HfO 2 and SiO 2 /Si 3 N 4 /ZrO 2 stacks with emphasis on the influence of atomic layer deposition chemistry used for forming the HfO 2 and ZrO 2 blocking layers. Two Hf precursors were employed -tetrakis(ethylmethylamino)hafnium (TEMAH) and bis(methylcyclopentadienyl)methoxymethyl hafnium (HfD-04). For ZrO 2 , tetrakis(ethylmethylamino)zirconium (TEMAZ) and bis(methylcyclopentadienyl)methoxymethyl zirconium (ZrD-04) were used as metal precursors. Ozone was used as the oxygen source. The structural characteristics of the stacks were examined by transmission electron microscopy and grazing incidence X-ray diffraction. The electrical properties of the stacks were studied using platinum-gated capacitor structures. The memory performance of the stacks was evaluated by write/erase (W/E) measurements, endurance and retention testing. Endurance measurements revealed the most important difference between the stacks. The films grown from TEMAH and TEMAZ could withstand a significantly higher number of W/E pulses (>3 Â 10 5 in the 10 V/À11 V, 10 ms regime), in comparison to the stacks made from HfD-04 and ZrD-04 precursors (<5 Â 10 3 W/E cycles). This difference in endurance characteristics is attributed mainly to the different deposition temperatures suited for these two precursors and the nature of the layer formed at the Si 3 N 4 /HfO 2 and the Si 3 N 4 /ZrO 2 interfaces.
In this work we report the performance of the SiO 2 /Si 3 N 4 /HfO 2 and SiO 2 /Si 3 N 4 /ZrO 2 s... more In this work we report the performance of the SiO 2 /Si 3 N 4 /HfO 2 and SiO 2 /Si 3 N 4 /ZrO 2 stacks with emphasis on the influence of atomic layer deposition chemistry used for forming the HfO 2 and ZrO 2 blocking layers. Two Hf precursors were employed -tetrakis(ethylmethylamino)hafnium (TEMAH) and bis(methylcyclopentadienyl)methoxymethyl hafnium (HfD-04). For ZrO 2 , tetrakis(ethylmethylamino)zirconium (TEMAZ) and bis(methylcyclopentadienyl)methoxymethyl zirconium (ZrD-04) were used as metal precursors. Ozone was used as the oxygen source. The structural characteristics of the stacks were examined by transmission electron microscopy and grazing incidence X-ray diffraction. The electrical properties of the stacks were studied using platinum-gated capacitor structures. The memory performance of the stacks was evaluated by write/erase (W/E) measurements, endurance and retention testing. Endurance measurements revealed the most important difference between the stacks. The films grown from TEMAH and TEMAZ could withstand a significantly higher number of W/E pulses (>3 Â 10 5 in the 10 V/À11 V, 10 ms regime), in comparison to the stacks made from HfD-04 and ZrD-04 precursors (<5 Â 10 3 W/E cycles). This difference in endurance characteristics is attributed mainly to the different deposition temperatures suited for these two precursors and the nature of the layer formed at the Si 3 N 4 /HfO 2 and the Si 3 N 4 /ZrO 2 interfaces.
ABSTRACT Ruthenium thin films were grown by atomic layer deposition from -dimethyl-1-ruthenocenyl... more ABSTRACT Ruthenium thin films were grown by atomic layer deposition from -dimethyl-1-ruthenocenylethylamine precursor. The growth was examined in the substrate temperature range of . The growth rate increased with the substrate temperature but was quite stable between 400 and . The films typically consisted of polycrystalline hexagonal ruthenium metal with a resistivity in the range of when the film thickness was 10 nm and above. A resistivity of could be achieved in the film as thin as 4 nm. Measurements on metal-insulator-metal (MIM) capacitors with Ru films as metal electrodes revealed a capacitive voltage behavior typical of MIM structures and appreciably high breakdown voltages.
The atomic layer deposition growth of tungsten nitride films was demonstrated using the precursor... more The atomic layer deposition growth of tungsten nitride films was demonstrated using the precursors W 2 (NMe 2) 6 and ammonia with substrate temperatures between 150 and 250 C. At 180 C, surface saturative growth was achieved with W 2 (NMe 2) 6 pulse lengths of ...
Stoichiometric HfO films were atomic layer deposited from HfI and HfCl at 300 8C on p-Si substrat... more Stoichiometric HfO films were atomic layer deposited from HfI and HfCl at 300 8C on p-Si substrates. Water was in 2 4 4 both cases used as an oxygen precursor. The films consisted dominantly of monoclinic HfO phase. Additional tetragonal HfO 2 2 could be detected only in the films grown from HfCl . Effective permittivities were frequency-independent and varied in the 4 range of 12-14, without clear dependence on the precursor used. Oxide rechargeable trap densities were relatively high for the films grown from HfCl . The films grown from HfI were more resistant against breakdown. The films grown from either 4 4
In this work we report the performance of the SiO 2 /Si 3 N 4 /HfO 2 and SiO 2 /Si 3 N 4 /ZrO 2 s... more In this work we report the performance of the SiO 2 /Si 3 N 4 /HfO 2 and SiO 2 /Si 3 N 4 /ZrO 2 stacks with emphasis on the influence of atomic layer deposition chemistry used for forming the HfO 2 and ZrO 2 blocking layers. Two Hf precursors were employed -tetrakis(ethylmethylamino)hafnium (TEMAH) and bis(methylcyclopentadienyl)methoxymethyl hafnium (HfD-04). For ZrO 2 , tetrakis(ethylmethylamino)zirconium (TEMAZ) and bis(methylcyclopentadienyl)methoxymethyl zirconium (ZrD-04) were used as metal precursors. Ozone was used as the oxygen source. The structural characteristics of the stacks were examined by transmission electron microscopy and grazing incidence X-ray diffraction. The electrical properties of the stacks were studied using platinum-gated capacitor structures. The memory performance of the stacks was evaluated by write/erase (W/E) measurements, endurance and retention testing. Endurance measurements revealed the most important difference between the stacks. The films grown from TEMAH and TEMAZ could withstand a significantly higher number of W/E pulses (>3 Â 10 5 in the 10 V/À11 V, 10 ms regime), in comparison to the stacks made from HfD-04 and ZrD-04 precursors (<5 Â 10 3 W/E cycles). This difference in endurance characteristics is attributed mainly to the different deposition temperatures suited for these two precursors and the nature of the layer formed at the Si 3 N 4 /HfO 2 and the Si 3 N 4 /ZrO 2 interfaces.
Schottky diodes were built on different polycrystalline diamond films grown by Microwave Plasma a... more Schottky diodes were built on different polycrystalline diamond films grown by Microwave Plasma and Hot Filament Chemical Vapor Deposition and their electrical properties were studied. The barrier height increased with the diamond film quality and the corresponding ideality factor decreased. Even though the lower-quality HFCVD film displayed poor rectifying properties, it was found to be much less sensitive to variations in the operating conditions (air vs. vacuum). The activation energies of the films depend on morphological parameters, as preferable grain size or orientation. The bulk conduction also depends on the quality of the deposited films, changing from ohmic to trap-free or shallow trap SCLC and SCLC with an exponential distribution of traps. The hypothesis of using the electrical measurements as an indicator for film quality has been discussed. D
HfO 2 thin films were atomic-layer deposited using different-precursor partial pressures and at d... more HfO 2 thin films were atomic-layer deposited using different-precursor partial pressures and at different growth temperatures on n-and p-type silicon substrates. The effect of processing parameters and film thickness on the electrical quality of the oxide-semiconductor interface was studied. Deep-level-transient spectroscopy and conductance-transient techniques revealed 3-10 × 10 11 cm −2 eV −1 interface trap densities, somewhat dependent on the processing conditions. Charge trapping took place mainly between the semiconductor and defects located at energies close to the majority-carrier-semiconductor-band edge.
A chemical approach to atomic layer deposition (ALD) of oxide thin films is reported here. Instea... more A chemical approach to atomic layer deposition (ALD) of oxide thin films is reported here. Instead of using water or other compounds for an oxygen source, oxygen is obtained from a metal alkoxide, which serves as both an oxygen and a metal source when it reacts with another metal compound such as a metal chloride or a metal alkyl. These reactions generally enable deposition of oxides of many metals. With this approach, an alumina film has been deposited on silicon without creating an interfacial silicon oxide layer that otherwise forms easily. This finding adds to the other benefits of the ALD method, especially the atomic-level thickness control and excellent uniformity, and takes a major step toward the scientifically challenging and technologically important task of replacing silica as the gate dielectric in the future generations of metal oxide semiconductor field effect transistors.
Crystallization of hafnia and zirconia and their alloys with silica and lanthana was studied in b... more Crystallization of hafnia and zirconia and their alloys with silica and lanthana was studied in bulk and thin film samples by thermal analysis, X-ray diffraction and electron microscopy. Crystallization temperatures of hafnia and zirconia increase by more than 300 °C with increase of surface/interface area of the amorphous phase. Crystallization temperatures of zirconia and hafnia alloys with silica and lanthana increase with dopant content and exceed 900 °C for 50 mol% SiO 2 and LaO 1.5 . Energies for tetragonal HfO 2 and ZrO 2 interfaces with amorphous silica were derived from their crystallization enthalpies from silicates as 0.25 ± 0.08 and 0.13 ± 0.07 J/m 2 , respectively. The crystallization pathways in bulk powders and films of zirconia and hafnia can be interpreted as resulting from thermodynamic stabilization by the surface energy term of tetragonal and amorphous phases over monoclinic.
Conformal ZrO 2 and HfO 2 thin films were grown by atomic layer deposition using novel liquid cyc... more Conformal ZrO 2 and HfO 2 thin films were grown by atomic layer deposition using novel liquid cyclopentadienyl precursors at 300 °C or 350 °C on planar Si wafers and deep trenched Si with an aspect ratio of 60:1. The crystal growth and phase content in as-deposited films depended on the precursor, film thickness, and the material grown. The structural and electrical behaviour of the films were somewhat precursor-dependent, revealing better insulating properties in the films grown from oxygen-containing precursors. Also the HfO 2 films showed lower leakage compared to ZrO 2 .
HfO 2 films were grown by atomic layer deposition from HfCl 4 and H 2 O on atomic layer deposited... more HfO 2 films were grown by atomic layer deposition from HfCl 4 and H 2 O on atomic layer deposited metal (Pt, Ir, Ru) films with rate exceeding that on SiO 2 /Si substrates. The phase formed at any growth stages on metals was monoclinic HfO 2 without essential contribution from amorphous or metastable phases. The latter phases were prominent in the films on Si substrates functionalized with alcohol groups. The growth rate of amorphous HfO 2 from HfCl 4 or Hf[N(CH 3 ) 2 ] 4 and H 2 O on functionalized Si was comparable to that on SiO 2 and higher than that commonly obtained on H-terminated Si surface. Instabilities in dielectric properties of HfO 2 could be reduced by post-deposition annealing. The Si surface functionalized with propanol groups promoted slightly more intense crystallization upon annealing, compared to butanol-functionalized surface
Hf-Si-O mixture films were fabricated by atomic layer deposition at 400 • C on Si(1 0 0) substrat... more Hf-Si-O mixture films were fabricated by atomic layer deposition at 400 • C on Si(1 0 0) substrates. The deposition sequence for one hafnium silicon oxide submonolayer comprises surface reactions between Si(OC 2 H 5 ) 4 and HfCl 4 , followed by the hydrolysis step in order to effectively remove the residual ligands. The effective permittivity, leakage current, and capacitance-voltage behavior depended on the hafnium/silicon ratio and on the oxide/silicon interface quality. The dielectric quality can be modulated for various configurations of stacked layers with different hafnium to silicon ratios.
Quantitative electron probe microanalysis of highly insulating materials is a complicated problem... more Quantitative electron probe microanalysis of highly insulating materials is a complicated problem, partially solved by coating samples with grounded thin conductive layers or using novel scanning electron microscopy (SEM) techniques, such as lowvoltage and=or variable pressure SEM. In this work, some problems of quantitative X-ray microanalysis of thin HfO 2 films, in particular the possibility to determine mass thickness correlated to the density of the layer material, are discussed. For comparison, Al 2 O 3 , Ta 2 O 5 and TiO 2 films grown onto both semiconductive Si and insulating quartz substrates were also analysed. All the films studied were synthesized by atomic layer deposition method.
Carbon nanoparticles were synthesized from 5-methylresorcinol and formaldehyde via base catalysed... more Carbon nanoparticles were synthesized from 5-methylresorcinol and formaldehyde via base catalysed polycondensation reaction and distributed over silicon oxide wafers and aluminium oxide thin films. These particles essentially possessed monocrystalline graphite structure. The particles were covered by hafnium oxide thin films in metal chloride based atomic layer deposition process carried out at 300°C. Upon deposition of HfO 2 , thin crystalline metal oxide layer containing mostly cubic phase was formed. At the same time, deposition of the metal oxide caused reduction of the sizes of graphite particles and essential increase in the disorder in carbon.
Atomic layer deposition of ZrO 2 films from tris(dimethylamino)cyclopentadienylzirconium CpZr(NMe... more Atomic layer deposition of ZrO 2 films from tris(dimethylamino)cyclopentadienylzirconium CpZr(NMe 2 ) 3 and H 2 O, was investigated using real-time characterization of the growth process and post-growth measurements of the films. Self-limited nature of the deposition process was observed at substrate temperatures ranging from 120 to 350°C. In this temperature range growth rate of 0.08-0.1 nm per cycle was obtained on silicon substrates. The films deposited on silicon substrates at 200°C and higher temperatures contained tetragonal and monoclinic phases of ZrO 2 . The phase composition of the films depended on the deposition temperature as well as on the film thickness. The concentration of carbon residues decreased with increasing deposition temperature and did not exceed 0.9 at.% in the films deposited at 250°C and higher temperatures. The refractive indices and densities of films grown from CpZr(NMe 2 ) 3 and H 2 O at 250-350°C ranged from 2.15 to 2.20 (at a wavelength of 633 nm) and 5.6 to 6.0 g/cm 3 , respectively, being close to the highest values obtained for films deposited from ZrCl 4 and H 2 O. The former process ensured, however, more uniform nucleation of ZrO 2 on graphene than the latter process did.
This work explores the electrical properties of Al 2 O 3 films formed by atomic layer deposition ... more This work explores the electrical properties of Al 2 O 3 films formed by atomic layer deposition (ALD) using different oxygen sources (water and ozone) and trimethylaluminium (TMA). The as-deposited Al 2 O 3 layers were used as blocking oxides in metal (Pt)-alumina-nitride-oxide-silicon memory capacitors. The capacitance-voltage characteristics of the devices with Al 2 O 3 deposited with the ozone-TMA and water-TMA processes showed almost identical capacitance equivalent thicknesses in accordance with transmission electron microscopy imaging which revealed similar dielectric layer thicknesses between the two gate stacks. At high negative gate voltages the water-TMA devices exhibited higher leakage currents than the ozone-TMA devices. This effect had a direct impact on the attainable memory window, due to the limited erase performance of the capacitors and the extended erase-saturation effect. These findings indicate that the ALD chemistry and in particular the oxygen source is a crucial factor which determines the electrical behavior of the as-deposited Al 2 O 3 films, and therefore the performance of the memory stacks. These differences are attributed to the different trap distributions either in space or energy within the Al 2 O 3 layers.
In this work, we examine the influence of hafnium and zirconium oxides ALD precursor chemistry on... more In this work, we examine the influence of hafnium and zirconium oxides ALD precursor chemistry on the memory properties of SiO 2 /Si 3 N 4 /ZrO 2 and SiO 2 /Si 3 N 4 /HfO 2 non-volatile gate memory stacks. Approximately 10 nm thick ZrO 2 and HfO 2 layers were deposited on top of a SiO 2 /Si 3 N 4 structure, functioning as blocking oxides. Both metal oxides were deposited using either alkylamides or cyclopentadienyls as metal precursors, and ozone as the oxygen source. In the case of the ZrO 2 gate stacks a memory window of 6 V was determined, comprised of 4 V write window and 2 V erase window. Although no dramatic/major differences were evident between the ZrO 2 layers, ZrO 2 grown from alkylamide provided structures with higher dielectric strength. The memory structures with HfO 2 blocking layers indicate that the memory window and the dielectric strength are significantly affected by the precursor. The structures with the HfO 2 formed from alkylamide showed a write window of 7 V, while the films grown from cyclopentadienyl possessed window of 5 V. Comparison between the memory windows obtained using ZrO 2 and HfO 2 as control oxides reveals that the former provides memory structures with higher electron trapping efficiency.
In this work we report the performance of the SiO 2 /Si 3 N 4 /HfO 2 and SiO 2 /Si 3 N 4 /ZrO 2 s... more In this work we report the performance of the SiO 2 /Si 3 N 4 /HfO 2 and SiO 2 /Si 3 N 4 /ZrO 2 stacks with emphasis on the influence of atomic layer deposition chemistry used for forming the HfO 2 and ZrO 2 blocking layers. Two Hf precursors were employed -tetrakis(ethylmethylamino)hafnium (TEMAH) and bis(methylcyclopentadienyl)methoxymethyl hafnium (HfD-04). For ZrO 2 , tetrakis(ethylmethylamino)zirconium (TEMAZ) and bis(methylcyclopentadienyl)methoxymethyl zirconium (ZrD-04) were used as metal precursors. Ozone was used as the oxygen source. The structural characteristics of the stacks were examined by transmission electron microscopy and grazing incidence X-ray diffraction. The electrical properties of the stacks were studied using platinum-gated capacitor structures. The memory performance of the stacks was evaluated by write/erase (W/E) measurements, endurance and retention testing. Endurance measurements revealed the most important difference between the stacks. The films grown from TEMAH and TEMAZ could withstand a significantly higher number of W/E pulses (>3 Â 10 5 in the 10 V/À11 V, 10 ms regime), in comparison to the stacks made from HfD-04 and ZrD-04 precursors (<5 Â 10 3 W/E cycles). This difference in endurance characteristics is attributed mainly to the different deposition temperatures suited for these two precursors and the nature of the layer formed at the Si 3 N 4 /HfO 2 and the Si 3 N 4 /ZrO 2 interfaces.
In this work we report the performance of the SiO 2 /Si 3 N 4 /HfO 2 and SiO 2 /Si 3 N 4 /ZrO 2 s... more In this work we report the performance of the SiO 2 /Si 3 N 4 /HfO 2 and SiO 2 /Si 3 N 4 /ZrO 2 stacks with emphasis on the influence of atomic layer deposition chemistry used for forming the HfO 2 and ZrO 2 blocking layers. Two Hf precursors were employed -tetrakis(ethylmethylamino)hafnium (TEMAH) and bis(methylcyclopentadienyl)methoxymethyl hafnium (HfD-04). For ZrO 2 , tetrakis(ethylmethylamino)zirconium (TEMAZ) and bis(methylcyclopentadienyl)methoxymethyl zirconium (ZrD-04) were used as metal precursors. Ozone was used as the oxygen source. The structural characteristics of the stacks were examined by transmission electron microscopy and grazing incidence X-ray diffraction. The electrical properties of the stacks were studied using platinum-gated capacitor structures. The memory performance of the stacks was evaluated by write/erase (W/E) measurements, endurance and retention testing. Endurance measurements revealed the most important difference between the stacks. The films grown from TEMAH and TEMAZ could withstand a significantly higher number of W/E pulses (>3 Â 10 5 in the 10 V/À11 V, 10 ms regime), in comparison to the stacks made from HfD-04 and ZrD-04 precursors (<5 Â 10 3 W/E cycles). This difference in endurance characteristics is attributed mainly to the different deposition temperatures suited for these two precursors and the nature of the layer formed at the Si 3 N 4 /HfO 2 and the Si 3 N 4 /ZrO 2 interfaces.
ABSTRACT Ruthenium thin films were grown by atomic layer deposition from -dimethyl-1-ruthenocenyl... more ABSTRACT Ruthenium thin films were grown by atomic layer deposition from -dimethyl-1-ruthenocenylethylamine precursor. The growth was examined in the substrate temperature range of . The growth rate increased with the substrate temperature but was quite stable between 400 and . The films typically consisted of polycrystalline hexagonal ruthenium metal with a resistivity in the range of when the film thickness was 10 nm and above. A resistivity of could be achieved in the film as thin as 4 nm. Measurements on metal-insulator-metal (MIM) capacitors with Ru films as metal electrodes revealed a capacitive voltage behavior typical of MIM structures and appreciably high breakdown voltages.
The atomic layer deposition growth of tungsten nitride films was demonstrated using the precursor... more The atomic layer deposition growth of tungsten nitride films was demonstrated using the precursors W 2 (NMe 2) 6 and ammonia with substrate temperatures between 150 and 250 C. At 180 C, surface saturative growth was achieved with W 2 (NMe 2) 6 pulse lengths of ...
Stoichiometric HfO films were atomic layer deposited from HfI and HfCl at 300 8C on p-Si substrat... more Stoichiometric HfO films were atomic layer deposited from HfI and HfCl at 300 8C on p-Si substrates. Water was in 2 4 4 both cases used as an oxygen precursor. The films consisted dominantly of monoclinic HfO phase. Additional tetragonal HfO 2 2 could be detected only in the films grown from HfCl . Effective permittivities were frequency-independent and varied in the 4 range of 12-14, without clear dependence on the precursor used. Oxide rechargeable trap densities were relatively high for the films grown from HfCl . The films grown from HfI were more resistant against breakdown. The films grown from either 4 4
In this work we report the performance of the SiO 2 /Si 3 N 4 /HfO 2 and SiO 2 /Si 3 N 4 /ZrO 2 s... more In this work we report the performance of the SiO 2 /Si 3 N 4 /HfO 2 and SiO 2 /Si 3 N 4 /ZrO 2 stacks with emphasis on the influence of atomic layer deposition chemistry used for forming the HfO 2 and ZrO 2 blocking layers. Two Hf precursors were employed -tetrakis(ethylmethylamino)hafnium (TEMAH) and bis(methylcyclopentadienyl)methoxymethyl hafnium (HfD-04). For ZrO 2 , tetrakis(ethylmethylamino)zirconium (TEMAZ) and bis(methylcyclopentadienyl)methoxymethyl zirconium (ZrD-04) were used as metal precursors. Ozone was used as the oxygen source. The structural characteristics of the stacks were examined by transmission electron microscopy and grazing incidence X-ray diffraction. The electrical properties of the stacks were studied using platinum-gated capacitor structures. The memory performance of the stacks was evaluated by write/erase (W/E) measurements, endurance and retention testing. Endurance measurements revealed the most important difference between the stacks. The films grown from TEMAH and TEMAZ could withstand a significantly higher number of W/E pulses (>3 Â 10 5 in the 10 V/À11 V, 10 ms regime), in comparison to the stacks made from HfD-04 and ZrD-04 precursors (<5 Â 10 3 W/E cycles). This difference in endurance characteristics is attributed mainly to the different deposition temperatures suited for these two precursors and the nature of the layer formed at the Si 3 N 4 /HfO 2 and the Si 3 N 4 /ZrO 2 interfaces.
Schottky diodes were built on different polycrystalline diamond films grown by Microwave Plasma a... more Schottky diodes were built on different polycrystalline diamond films grown by Microwave Plasma and Hot Filament Chemical Vapor Deposition and their electrical properties were studied. The barrier height increased with the diamond film quality and the corresponding ideality factor decreased. Even though the lower-quality HFCVD film displayed poor rectifying properties, it was found to be much less sensitive to variations in the operating conditions (air vs. vacuum). The activation energies of the films depend on morphological parameters, as preferable grain size or orientation. The bulk conduction also depends on the quality of the deposited films, changing from ohmic to trap-free or shallow trap SCLC and SCLC with an exponential distribution of traps. The hypothesis of using the electrical measurements as an indicator for film quality has been discussed. D
HfO 2 thin films were atomic-layer deposited using different-precursor partial pressures and at d... more HfO 2 thin films were atomic-layer deposited using different-precursor partial pressures and at different growth temperatures on n-and p-type silicon substrates. The effect of processing parameters and film thickness on the electrical quality of the oxide-semiconductor interface was studied. Deep-level-transient spectroscopy and conductance-transient techniques revealed 3-10 × 10 11 cm −2 eV −1 interface trap densities, somewhat dependent on the processing conditions. Charge trapping took place mainly between the semiconductor and defects located at energies close to the majority-carrier-semiconductor-band edge.
A chemical approach to atomic layer deposition (ALD) of oxide thin films is reported here. Instea... more A chemical approach to atomic layer deposition (ALD) of oxide thin films is reported here. Instead of using water or other compounds for an oxygen source, oxygen is obtained from a metal alkoxide, which serves as both an oxygen and a metal source when it reacts with another metal compound such as a metal chloride or a metal alkyl. These reactions generally enable deposition of oxides of many metals. With this approach, an alumina film has been deposited on silicon without creating an interfacial silicon oxide layer that otherwise forms easily. This finding adds to the other benefits of the ALD method, especially the atomic-level thickness control and excellent uniformity, and takes a major step toward the scientifically challenging and technologically important task of replacing silica as the gate dielectric in the future generations of metal oxide semiconductor field effect transistors.
Crystallization of hafnia and zirconia and their alloys with silica and lanthana was studied in b... more Crystallization of hafnia and zirconia and their alloys with silica and lanthana was studied in bulk and thin film samples by thermal analysis, X-ray diffraction and electron microscopy. Crystallization temperatures of hafnia and zirconia increase by more than 300 °C with increase of surface/interface area of the amorphous phase. Crystallization temperatures of zirconia and hafnia alloys with silica and lanthana increase with dopant content and exceed 900 °C for 50 mol% SiO 2 and LaO 1.5 . Energies for tetragonal HfO 2 and ZrO 2 interfaces with amorphous silica were derived from their crystallization enthalpies from silicates as 0.25 ± 0.08 and 0.13 ± 0.07 J/m 2 , respectively. The crystallization pathways in bulk powders and films of zirconia and hafnia can be interpreted as resulting from thermodynamic stabilization by the surface energy term of tetragonal and amorphous phases over monoclinic.
Conformal ZrO 2 and HfO 2 thin films were grown by atomic layer deposition using novel liquid cyc... more Conformal ZrO 2 and HfO 2 thin films were grown by atomic layer deposition using novel liquid cyclopentadienyl precursors at 300 °C or 350 °C on planar Si wafers and deep trenched Si with an aspect ratio of 60:1. The crystal growth and phase content in as-deposited films depended on the precursor, film thickness, and the material grown. The structural and electrical behaviour of the films were somewhat precursor-dependent, revealing better insulating properties in the films grown from oxygen-containing precursors. Also the HfO 2 films showed lower leakage compared to ZrO 2 .
HfO 2 films were grown by atomic layer deposition from HfCl 4 and H 2 O on atomic layer deposited... more HfO 2 films were grown by atomic layer deposition from HfCl 4 and H 2 O on atomic layer deposited metal (Pt, Ir, Ru) films with rate exceeding that on SiO 2 /Si substrates. The phase formed at any growth stages on metals was monoclinic HfO 2 without essential contribution from amorphous or metastable phases. The latter phases were prominent in the films on Si substrates functionalized with alcohol groups. The growth rate of amorphous HfO 2 from HfCl 4 or Hf[N(CH 3 ) 2 ] 4 and H 2 O on functionalized Si was comparable to that on SiO 2 and higher than that commonly obtained on H-terminated Si surface. Instabilities in dielectric properties of HfO 2 could be reduced by post-deposition annealing. The Si surface functionalized with propanol groups promoted slightly more intense crystallization upon annealing, compared to butanol-functionalized surface
Hf-Si-O mixture films were fabricated by atomic layer deposition at 400 • C on Si(1 0 0) substrat... more Hf-Si-O mixture films were fabricated by atomic layer deposition at 400 • C on Si(1 0 0) substrates. The deposition sequence for one hafnium silicon oxide submonolayer comprises surface reactions between Si(OC 2 H 5 ) 4 and HfCl 4 , followed by the hydrolysis step in order to effectively remove the residual ligands. The effective permittivity, leakage current, and capacitance-voltage behavior depended on the hafnium/silicon ratio and on the oxide/silicon interface quality. The dielectric quality can be modulated for various configurations of stacked layers with different hafnium to silicon ratios.
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Papers by Kaupo Kukli