Characterization of the electronic structure and thermal stability of HfO2/SiO2/Si gate dielectric stack

X‐ray photoelectron spectroscopy was used to investigate thermal stability of HfO₂ on SiO₂/Si substrate prepared by atomic layer deposition, followed by annealing at different temperature. Hf silicate and Hf silicide are formed at the interface of HfO₂ and SiO₂ during deposition. The Hf silicide disappears, while the amount of the Hf silicate is intensified after post‐deposition annealing treatment at 400 °C. Phase separation of the Hf silicate layer occurs when the annealing temperature is over 400 °C, resulting in the Hf silicate decomposition into Si and Hf oxides. Moreover, crystallization at high temperature leads to grain boundaries formation, which deteriorates the gate leakage current, as observed by the electrical measurements. The similar annealing temperature dependence of both internal electric field and the amount of Hf silicate implies that the Hf silicate plays a key role in building up the internal electric field, which is attributed to generation of oxygen vacancies (V_o) in the Hf silicate layer. Copyright © 2017 John Wiley & Sons, Ltd.     

Interfacial properties of thermally oxidized Ta2Si on Si

Many refractory metal silicides have received great attention due to their potential for innovative developments in the silicon‐based microelectronic industry. However, tantalum silicide, Ta₂Si, has remained practically unnoticed since its successful application in silicon carbide technology as a simple route for a high‐k dielectric formation. The thermal oxidation of Ta₂Si produces high‐k dielectric layers, (O? Ta₂Si)‐based on a combination of Ta₂O₅ and SiO₂. In this work, we investigate the interfacial properties of thermally oxidized (850–1050 °C) Ta₂Si on commercial silicon substrates. The implications of diffusion processes in the dielectric properties of an oxidized layer are analyzed. In particular, we observe migration of tantalum pentoxide nanocrystals into the substrate with increasing oxidation temperature. An estimation of the insulator charge and interfacial O? Ta₂Si/Si trap density is also presented. Copyright © 2008 John Wiley & Sons, Ltd.     

Darstellung und Struktur von U2Ta6O19, einer neuen Verbindung mit „Jahnberg‐Struktur”︁, sowie Anmerkungen zu den ersten Oxidchloriden in den Systemen Th/Nb/O/Cl und Th/Zr(Hf)/Nb/O/Cl

Synthesis and Crystal Structure of U₂Ta₆O₁₉, a New Compound with “Jahnberg‐Structure” and a Note to the First Oxide Chlorides in the Systems Th/Nb/O/Cl and Th/Zr(Hf)/Nb/O/Cl Black crystals of U₂Ta₆O₁₉ with hexagonal shape were obtained (at T₁) by chemical transport using HCl (p (HCl, 298 K) = 1 atm; silica tube) as transport agent in a temperature gradient (T₂ → T₁; 1000 °C → 950 °C) and using a mixture of UO₂, Ta₂O₅, and HfO₂ (or ZrO₂) (1 : 2 : 2) as starting materials (at T₂). For the structure determination the best result was achieved in space group P6₃/mcm (No. 193, a = 6.26(2) Å, c = 19.86(6) Å). U₂Ta₆O₁₉ is isotypical to Th₂Ta₆O₁₉. In the crystal structure each uranium atom is surrounded by oxygen atoms like a bi‐capped trigonal antiprism and tantalum atoms like a pentagonal bipyramid (CN = 7). Like the “Jahnberg Structures” both coordination polyhedra arrange themselves in separate layers (U–O‐polyhedra, in o‐, Ta–O‐polyhedra in p‐layers) so that in the direction of the c‐axis the sequence of layers is p‐p‐o. Using chemical transport it was possible to prepare the compounds Th₁₂Nb₁₆O₆₃Cl₂ and Th₈M₄Nb₁₆O₆₃Cl₂ (M = Zr, Hf), which are the first quaternary and quinquinary examples in these systems. They crystallize isotypically.     

Die metallreiche Schichtstruktur von Ta6STe3

The Metal‐rich Layer Structure of Ta₆STe₃ Ta₆S_1+xTe_3–x was prepared from an appropriate mixture of 2 H–Ta_1.3S₂, TaTe₂, and Ta in a fused tantalum tube at 1273 K within 3 d. The results of a X‐ray single crystal structure analysis for a phase near the Te‐rich limit of the homogeneity range are reported. Ta₆S_1.00Te_3.00(1) crystallizes in the triclinic space group P1, a = 993.14(8) pm, b = 1032.18(8) pm, c = 1378.78(11) pm, α = 79.32(1)°, β = 81.36(1)°, γ = 85.74(1)°, Z = 6, Pearson symbol aP60, 6048 I_o > 2σ (I_o), 286 variables, wR₂ = 0.067. The metal‐rich layer structure of Ta₆STe₃ comprises distorted icosahedral Ta₁₃ clusters and related deltahedral cluster fragments complemented by chalcogen atoms. The centred clusters consist of 11, 12, 13, 14, or 16 atoms. They interpenetrate into lamellae in which the tantalum and chalcogen atoms are spatially segregated according to [Q–Ta₃–Q]. The signature of the structure is a lenticular heptagonal antiprismatic Ta₃₀ cluster which seems to be excised from the pentagonal antiprismatic columnar structure of Ta₆S. The Ta₃₀ clusters and distorted icosahedral Ta₁₃ clusters are connected and fused into puckered layers. The rest of the tantalum valences are used for heteronuclear bonding. The chalcogen atoms having three to six next tantalum atoms coat the corrugated, tetrahedrally close‐packed layers. Ta₆STe₃ is a moderate metallic conductor (ρ_{293 K} = 3 × 10^–4 Ωcm) exhibiting typical temperature independent paramagnetic properties.     

Simplified Synthesis and Structural Study of { Ta6Br12} Clusters

Direct reaction of stoichiometric amounts of KBr, tantalum and bromine at 720 °C, followed by extraction and crystallization gives Ta₆Br₁₄ · 7H₂O (1) . This compound slowly aquates into [(Ta₆Br₁₂)(H₂O)₆]²⁺, which crystallized as mixed Cs⁺/Br^– ( 2 ), Cl^– ( 3 ) and SO₄^2– ( 4 ) salts. In Bu₄NBr melt, 1 undergoes oxidation into (Bu₄N)₂[(Ta₆Br₁₂)Br₆] ( 5 ). Reaction of 1 with dimethylsulfoxide also induces oxidation of the { Ta₆Br₁₂} ²⁺ core into { Ta₆Br₁₂} ⁴⁺, and the corresponding complex [(Ta₆Br₁₂)(dmso)₂Cl₄] · iPrOH · 4.8H₂O ( 6 ) was isolated and structurally characterized. Molecular and crystal structures for 2 – 6 were determined.     

Depth profiles of Ta2O5/SiO2/Si structures: a combined X-ray photoemission, Auger electron, and secondary ion mass spectroscopic study

Summary We prepared thin films of tantalum oxide on SiO₂/Si substrates by thermal oxidation of tantalum. The different oxide layers and their interfaces were characterized by SIMS, AES, and XPS. Characteristic structures were obtained after different oxidation procedures. The comparative discussion of AES and SIMS depth profiles makes possible an unequivocal characterization of the reactive interfaces between the oxides of Ta and Si. The Ta₂O₅/SiO₂ interface in particular shows non-stoichiometries which depend on the oxidation procedures and which determine the performance characteristics of pH-sensitive Ta₂O₅ field-effect transistors.

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Tiefenprofile von Ta₂O₃/SiO₂/Si-Strukturen: Eine kombinierte Untersuchung mit Röntgen-Photoemissions-, Auger-Elektronen- und Sekundär-Ionen-Massen-Spektrometrie

     

Interface characterization of a metal‐oxide‐semiconductor structure by biased X‐ray photoelectron spectroscopy

X‐ray photoelectron spectroscopy (XPS) measurements of a Pt/HfO₂(SiO₂)/Si metal‐oxide‐semiconductor (MOS) structure under a bias voltage applied between the gate metal and the silicon substrate were studied. The binding energy shifts of Pt 4f, Hf 4f, O 1s and Si 2p according to the applied voltage were investigated using the MOS structure. After the influence of measurements on the results was carefully examined under various conditions, the amount of the shifts was analyzed from a viewpoint of band alignment. Based on the experimental results, a new way of interpreting the deviation of the electric properties from the ideal ones in a band diagram was proposed. It was demonstrated that the biased XPS is a very powerful method to understand the origin of the electric properties of MOS. Copyright © 2010 John Wiley & Sons, Ltd.     

Investigating Pb diffusion across buried interfaces in Pb(Zr0.2Ti0.8)O3 thin films via time‐of‐flight secondary ion mass spectrometry depth profiling

The diffusion of Pb through Pb(Zr_0.2Ti_0.8)O₃(PZT)/Pt/Ti/SiO₂/Si thin film heterostructures is studied by using time‐of‐flight secondary ion mass spectrometry depth profiling. The as‐deposited films initially contained 10 mol% Pb excess and were thermally processed at temperatures ranging from 325 to 700°C to promote Pb diffusion. The time‐of‐flight secondary ion mass spectrometry depth profiles show that increasing processing temperature promoted Pb diffusion from the PZT top film into the buried heterostructure layers. After processing at low temperatures (eg, 325°C), Pb⁺ counts were low in the Pt region. After processing at elevated temperatures (eg, 700°C), significant Pb⁺ counts were seen throughout the Pt layer and into the Ti and SiO₂ layers. Intermediate processing temperatures (400, 475, and 500°C) resulted in Pb⁺ profiles consistent with this overall trend. Films processed at 400°C show a sharp peak in PtPb⁺ intensity at the PZT/Pt interface, consistent with prior reports of a Pt₃Pb phase at this interface after processing at similar temperatures.     

Synthese,Struktur und Eigenschaften der tantalreichen Silicidchalkogenide Ta15Si2QxTe10–x (Q = S,Se)

Synthesis, Structure, and Properties of the Tantalum‐rich Silicide Chalcogenides Ta₁₅Si₂Q_xTe_10–x (Q = S, Se) The quaternary tantalum silicide chalcogenides Ta₁₅Si₂Q_xTe_10–x (Q = S, Se) are accessible from proper, compacted mixtures of the respective dichalcogenides, silicon and elemental tantalum at 1770 K in sealed molybdenum tubes. The structures were determined from the strongest X‐ray intensities of fibrous crystals with cross sections of about 3 μm and confirmed by fitting the profile of single phase X‐ray diffractograms. The phases Ta₁₅Si₂S_3.5Te_6.5 and Ta₁₅Si₂Se_3.5Te_6.5 crystallize in the monoclinic space group C2/m with two formula units per unit cell, a = 2393.7(1) pm, b = 350.08(2) pm, c = 1601.2(1) pm, β = 124.700(4)°, and a = 2461.3(2) pm, b = 351.70(2) pm, c = 1601.7(1) pm, β = 124.363(5)°, respectively. Tri‐capped trigonal prismatic Ta₉Si clusters stabilized by encapsulated Si atoms can be seen as the characteristic unit of the structure. The clusters are fused into twin columns which are connected by additional Ta atoms, thus forming corrugated layers. The remaining valences at the surfaces of the layered Ta–Si substructure are saturated by those of chalcogen atoms which are coordinated only from one side by three, four or five Ta atoms. Few bridging covalent Ta–S–Ta and Ta–Se–Ta bonds and, otherwise, dispersive interactions between the Q atoms hold these nearly one nanometer wide slabs together. The phases are moderate metallic conductors. There is no evidence for any electronic instability within 10–310 K in spite of the high anisotropy of the structures.     

Effects of elastic scattering and analyzer‐acceptance angle on the analysis of angle‐resolved X‐ray photoelectron spectroscopy data

We have made calculations of N 1s, O 1s, Si(oxide) 2p, Hf 4f, and Si(substrate) 2p photoelectron intensities at selected emission angles for films of SiO_1.6N_0.4 and HfO_1.9N_0.1 of various thicknesses on silicon. These calculations were made with the National Institute of Standards and Technology (NIST) Database for Simulation of Electron Spectra for Surface Analysis (SESSA) to investigate effects of elastic scattering and analyzer‐acceptance angle that could be relevant in the analysis of angle‐resolved X‐ray photoelectron spectroscopy (ARXPS) experiments. The simulations were made for an XPS configuration with a fixed angle between the X‐ray source (i.e. for the sample‐tilting mode of ARXPS) and with Al and Cu Kα X‐ray sources. The no‐loss intensities changed appreciably as elastic scattering was switched ‘on’ and ‘off’, but changing the analyzer‐acceptance angle had a smaller effect. Ratios of intensities for each line from the overlayer film for the least realistic model condition (elastic scattering switched ‘off’, small analyzer‐acceptance angle) to those from the most realistic model condition (elastic scattering switched ‘on’, finite analyzer‐acceptance angle) changed relatively slowly with emission angle, but the corresponding intensity ratio for the Si(substrate) 2p line changed appreciably with emission angle. The latter changes, in particular, indicate that neglect of elastic‐scattering effects can lead to erroneous results in the analysis of measured ARXPS data. The elastic‐scattering effects were larger in HfO_1.9N_0.1 than in SiO_1.6N_0.4 (due to the larger average atomic number in the former compound) and were larger with the Al Kα X‐ray source than with the Cu Kα source because of the larger cross sections for elastic scattering at the lower photoelectron energies. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of post-deposition annealing temperature on RF-sputtered HfO2 thin film for advanced CMOS technology

Structural and electrical properties of HfO₂ gate-dielectric metal-oxide-semiconductor (MOS) capacitors deposited by sputtering are investigated. The HfO₂ high-k thin films have been deposited on p-type <100> silicon wafer using RF-Magnetron sputtering technique. The Ellipsometric, FTIR and AFM characterizations have been done. The thickness of the as deposited film is measured to be 35.38 nm. Post deposition annealing in N₂ ambient is carried out at 350, 550, 750 °C. The chemical bonding and surface morphology of the film is verified using FTIR and AFM respectively. The structural characterization confirmed that the thin film was free of physical defects and root mean square surface roughness decreased as the annealing temperature increased. The smooth surface HfO₂ thin films were used for Al/HfO₂/p-Si MOS structures fabrication. The fabricated Al/HfO₂/p-Si structure had been used for extracting electrical properties such as dielectric constant, EOT, interface trap density and leakage current density through capacitance voltage and current voltage measurements. The interface state density extracted from the G–V measurement using Hill Coleman method. Sample annealed at 750 °C showed the lowest interface trap density (3.48 × 10¹¹ eV⁻¹ cm⁻²), effective oxide charge (1.33 × 10¹² cm⁻²) and low leakage current density (3.39 × 10⁻⁹ A cm⁻²) at 1.5 V.     

Synthesis and Crystal Structure of Rb6Ta4S22: The First Tantalum Polysulfide Composed of the Dimeric Complex Anion [Ta4S22]6–

The reaction of Rb₂S₃, Ta and S in a 1.3 : 1 : 5.6 molar ratio at 400 °C yields red‐orange crystals of the new ternary compound Rb₆Ta₄S₂₂ being the first tantalum polysulfide containing the dimeric complex anion [Ta₄S₂₂]^6–. The polysulfide anions are composed of two Ta₂S₁₁ subunits which are linked to Ta₄S₂₂ units via terminal sulfur ligands. The Ta⁵⁺ centers are coordinated by S₂^2– and S^2– ligands according to [(Ta₂(μ₂‐η²,η¹‐S₂)₃(η²‐S₂)(S)₂)₂(μ₂‐η¹,η¹‐S₂)]^6–. Every Ta⁵⁺ ion is surrounded by seven sulfur ions forming a strongly distorted pentagonal bipyramid. In the crystal structure the discrete [Ta₄S₂₂]^6– anions are stacked parallel to the crystallographic b‐axis. The Rb⁺ cations are located between these stacks. Rb₆Ta₄S₂₂ crystallizes in the monoclinic space group P2₁/c (No. 14) with a = 11.8253(9) Å, b = 7.9665(4) Å, c = 19.174(2) Å, β = 104.215(9)°, V = 1751.0(2) ų, Z = 2.     

Structure and dielectric properties of HfO<Subscript>2</Subscript> films prepared by a sol–gel route

Mono- and multilayer HfO₂ sol–gel thin films have been deposited on silicon wafers by dip-coating technique using a solution based on hafnium ethoxide as precursor. The densification/crystallization process was achieved by classical annealing between 400 and 600 °C for 0.5 h (after drying at 100 °C). Systematic TEM studies were performed to observe the evolution of the thin film structure depending on the annealing temperature. The overall density of the films was determined from RBS spectrometry correlated with cross section (XTEM) thickness measurements. After annealing at 450 °C the films are amorphous with a nanoporous structure showing also some incipient crystallization. After annealing at 550 °C the films are totally crystallized. The HfO₂ grains grow in colonies having the same crystalline orientation with respect to the film plane, including faceted nanopores. During annealing a nanometric SiO₂ layer is formed at the interface with the silicon substrate; the thickness of this layer increases with the annealing temperature. Capacitive measurements allowed determining the value of the dielectric constant as 25 for four layer films, i.e. very close to the value for the bulk material.     

Na0.74Ta3O6, ein niedervalentes Oxotantalat mit einer Ta–Ta‐Mehrfachbindung

Na_0.74Ta₃O₆, a Low‐Valent Oxotantalate with Multiple Ta–Ta Bonds The title compound was prepared in a sealed tantalum tube through the reaction of Ta₂O₅, tantalum and Na₂CO₃ in a NaCl flux at 1570 K within 5 d. The crystal structure of Na_0.74Ta₃O₆ (a = 713.5(1), b = 1027.4(2), c = 639.9(1) pm, Immm, Z = 4) was determined by single crystal X‐ray means. The structure is isomorphous with NaNb₃O₅F [1]. The characteristic structural units are triply bonded Ta1₂ dumb‐bells with eight square‐prismatically co‐ordinated O ligands. Four Ta2, each octahedrally surrounded by O atoms, are side‐on bonded weakly to the binuclear Ta₂O₈ complex, thus forming a Ta₆ propellane‐like cluster. The lattice parameters of three additional M_xTa₃O₆ phases, M = Li, Mn, and Yb, are reported.     

Toward accurate characterization of nitrogen depth profiles in ultrathin oxynitride films

Good accuracy in depth profile analyses of nitrogen in ultrathin oxynitride films is desirable for process development and routine process monitoring. Low energy SIMS is one of the techniques that has found success in the accurate characterization of thin oxynitride films. This work investigated the artifacts in a typical depth profile analysis of nitrogen with the current SIMS technique and the ways to improve the accuracy by selecting optimal analytical conditions. It was demonstrated that surface roughness developed rapidly in a SiO₂/Si stack when it was bombarded with an O₂⁺ beam at 250 eV and angle of incidence from 70 to 79° . The roughness caused distortion in the measured depth profiles of nitrogen and the major component elements. However, the above roughness and the distortion in the depth profiles can be eliminated by using a 250 eV O₂⁺ beam at an angle of incidence above 80° . Depth profile analyses with a 250 eV 83° O₂⁺ beam exhibited minimal surface roughening and insignificant variation in the secondary ion yield of SiN^? from SiO₂ bulk to the SiO₂/Si interface, facilitating an accurate analysis of nitrogen distribution in a SiO₂/Si stack. In addition, depth profiles of the major component elements such as ¹⁸O^? and ²⁸Si^? delivered clear information on the location of the SiO₂/Si interface. Using the new approach, we compared nitrogen distribution in thin SiNO films with the decoupled‐plasma nitridation (DPN) at various powers. Copyright © 2008 John Wiley & Sons, Ltd.     

[{(CH3)3Si}3C–Li–C{Si(CH3)3}3][Li · 3(OC4H8)] und {(CH3)3Si}3C–Li · O=C(Si(CH3)3)2, zwei neue Addukte des Lithium‐trisylmethanids

[{(CH₃)₃Si}₃C–Li–C{Si(CH₃)₃}₃][Li · 3(OC₄H₈)] and {(CH₃)₃Si}₃C–Li · O=C(Si(CH₃)₃)₂, two New Adducts of Lithium Trisylmethanide Sublimation of (Tsi–Li) · 2 THF (Tsi = –C(Si(CH₃)₃)₃) at 180 °C and 10^–4 hPa gives (Tsi–Li) · 1.5 THF in very low yield. The X‐ray structure determination shows an almost linear [Tsi–Li–Tsi]^– anion connected by short agostic Li…C contacts with the threefold THF‐coordinated Li‐cation. Base‐free Tsi–Li, solved in toluene is decomposed by oxygen, forming the strawberry‐colored ketone O=C(SiMe₃)₂, which forms an 1 : 1 adduct with undecomposed Tsi–Li. The X‐ray structure elucidation of this compound is also discussed.     

Sol–gel preparation of mesoporous Al2O3–SiO2 glasses: structural evolution monitored by solid state NMR

Glasses along the composition line 0.5Al₂O₃–xSiO₂ (1 ≤ x ≤ 6) were prepared via a novel sol–gel route using tetraethylorthosilicate and aluminum lactate as precursors. The structural evolution from solution to gel to glass is monitored by standard ²⁷Al and ²⁹Si nuclear magnetic resonance (NMR) spectroscopies, revealing important insights about molecular level mechanisms occurring at the various stages of glass formation. Under the experimental conditions reported, silica and alumina precursors undergo homoatomic condensation processes when the gel is heat treated at about 100 and 300 °C, respectively, and only little heteroatomic co-condensation occurs in this temperature range. The latter is promoted only upon elimination of the residual lactate and water ligands upon annealing the gels above 300 °C. Following calcination at 650 °C, mesoporous glasses are obtained, having average pore diameter of about 3 nm and a surface areas near 500 m²/g. Si–O–Al connectivities are detected by ²⁹Si magic angle spinning (MAS)-NMR. ²⁷Al MAS-NMR spectra reveal aluminum in four-, five- and six-coordination. The spectra differ significantly from those of other sol–gel derived Al₂O₃–SiO₂ materials prepared from different precursor routes, suggesting that the lactate route results in a higher degree of compositional homogeneity.     

Cs4K2CuSi2O8: Synthese,Kristallstruktur, UV‐Vis‐IR‐Daten

Cs₄K₂CuSi₂O₈: Synthesis, Crystal Structure, UV‐Vis‐IR Data Cs₄K₂CuSi₂O₈ may be obtained via a redox reaction of KCuO₂ in the presence of Cs₂O and SiO₂ with the container material (Cu) at 450 °C as blue single crystals which are sensitive to moisture. Powder samples were obtained by annealing intimate mixtures of the binary oxides under an inert gas atmosphere (Ar) in sealed Ag containers at 500 °C. The crystal structure contains isolated trimeric anions of [O₂SiO₂CuO₂SiO₂]^6–. Cu²⁺ in square‐planar coordination share trans‐edges with [SiO₄] tetrahedra. Spectroscopic investigations focus on the bonding situation of the [CuO₄] unit (AOM) and characteristic vibrational modes of the silicate.     

Pyrochlore and Perovskite Potassium Tantalate: Enthalpies of Formation and Phase Transformation

Alkali niobates and tantalates are currently important lead‐free functional oxides. The formation and decomposition energetics of potassium tantalum oxide compounds (K₂O?Ta₂O₅) were measured by high‐temperature oxide melt solution calorimetry. The enthalpies of formation from oxides of KTaO₃ perovskite and defect pyrochlores with K/Ta ratio of less than 1 stoichiometry—K_0.873Ta_2.226O₆, K_1.128Ta_2.175O₆, and K_1.291Ta_2.142O₆—were experimentally determined, and the values are (?203.63±2.92) kJ mol^?1 for KTaO₃ perovskite, and (?339.54±5.03) kJ mol^?1, (?369.71±4.84) kJ mol^?1, and (?364.78±4.24) kJ mol^?1, respectively, for non‐stoichiometric pyrochlores. That of stoichiometric defect K₂Ta₂O₆ pyrochlore, by extrapolation, is (?409.87±6.89) kJ mol^?1. Thus, the enthalpy of the stoichiometric pyrochlore and perovskite at K/Ta=1 stoichiometry are equal in energy within experimental error. By providing data on the thermodynamic stability of each phase, this work supplies knowledge on the phase‐formation process and phase stability within the K₂O?Ta₂O₅ system, thus assisting in the synthesis of materials with reproducible properties based on controlled processing. Additionally, the relation of stoichiometric and non‐stoichiometric pyrochlore with perovskite structure in potassium tantalum oxide system is discussed.     

Characterization of the interfacial structure and perpendicular magnetic anisotropy in CoFeB‐MgO structures with different buffer layers

In this study, we describe the deposition of Hf and Mo metal layers individually on Ta to compose new buffer layers, ie, Ta/Hf and Ta/Mo, where CoFeB/MgO stacks are deposited using magnetron sputtering. The synthesised Ta/Hf buffer has higher surface roughness, while the Ta/Mo buffer has lower surface roughness as compared with the Ta buffer. The surface roughness of the buffer appears to influence the interface of the subsequently deposited layers, resulting in rougher or smoother CoFeB/MgO interfaces. Additionally, we present a report on the magnetic properties of Ta, Ta/Hf, and Ta/Mo buffer samples. As the annealing temperature is below 200 °C, the saturation magnetisation (Ms) values for all buffer layers increase at similar rates, whereas the effective magnetic anisotropy energy (K_eff) values increase at varying rates. After annealing at 350 °C, K_eff reaches its maximum value for Ta/Hf and Ta/Mo buffer layers, whereas the CoFeB/MgO interface width decreases to a minimum value. The width increases as the annealing temperature is increased over 350 °C, and K_eff gradually decreases with increase in the annealing temperature. The CoFeB/MgO interface width is primarily dependent on the buffer/CoFeB interface width, which is a critical parameter to obtain high perpendicular magnetic anisotropy (PMA) and high‐quality films. This work provides perspectives for understanding and controlling PMA from the viewpoint of interfacial structure.