Ti Underlayer Research Articles

Effect of the underlayer on the microstructure and surface evolution in Al-0.5wt.%Cu polycrystalline thin films

The effects of the Ti underlayer on the evolution of grain morphology, crystallographic texture, and surface roughness of Al-0.5wt.%Cu thin films during sputter deposition have been characterized. In comparison to SiO2 substrates, Ti underlayers reduce the AlCu thickness at which film continuity is reached, reduce the AlCu columnar grain size, and allow exact Al (111) fiber texture development. The AlCu films on both Ti and SiO2 are primarily randomly oriented at early stages of deposition. A near-(111) Al fiber texture in AlCu/SiO2 films initiates during the preferential growth of ≈5° offset islands prior to film continuity, seeding the near Al (111) texture as film continuity is reached. The exact Al (111) fiber orientation in AlCu/Ti films develops after film continuity. The near-(111) and exact (111) fiber textures strengthen with further deposition due to combined normal and abnormal grain growth. Film coalescence and grain growth lead to a significant smoothing effect during the early stages of deposition.

高垂直抗磁力Ｃｏ‐Ｃｒ‐Ｐｔ薄膜の薄層化

Effects of intermediate layer and sputtering condition on magnetic properties were studied in Co-Cr-Pt film with high coercivity (HC⊥), large squareness (SQ⊥), and large nucleation field (HN). An ultrathin Cr intermediate layer was effective in reducing the Co-Cr-Pt film thickness while maintaining high HC⊥. HC⊥ as high as 5000 Oe was obtained by low power sputtering at a low substrate temperature. This method is effective in reducing both Co-Cr-Pt film thickness and Ti underlayer thickness.

Effects of deposition conditions of Al and Ti underlayer on electromigration reliability for deep-submicron interconnect metallization

We have studied the effects of Ti underlayer (collimated Ti vs. standard Ti) and Al deposition power (12 KW vs. 6 KW) on the electromigration (EM) lifetime of bottom-Ti/Al-0.5wt.%Cu/Ti/TiN-top stack. The (002) texture of standard Ti (s-Ti) was stronger than that of collimated Ti (c-Ti). The Al stack prepared with s-Ti underlayer, which had the stronger Al (111) texture and more uniform grain size distribution, showed better EM lifetime than the same with c-Ti underlayer, independent of the Al deposition power. The Al stack prepared with an Al deposition power of 6 KW was also found to show better EM lifetime than the same with a 12 KW deposition power, independent of the type of Ti underlayer. Longer deposition time for low power sputtering resulted in the stronger Al (111) texture, larger median grain size, and more uniform Ti−Al reaction layer. Finally, the effects of Ti underlayer and Al deposition power on the EM lifetime of Al-0.5%Cu films could be well explained by the grain size distribution and Al (111) texture, which is closely related to the underlying-Ti (002) texture.

Package-and wafer-level electromigration tests on Al−Cu interconnect with Ti and TiN underlayers

The effect of A1 underlayer between Ti and TiN on the electromigration (EM) lifetime of Al stack film were compared with package-level and conventional wafer-level EM tests. The higher EM resistance of the Al stacks prepared with Ti underlayer can be best explained by their better Al (111) texture and grain size distribution than those with TiN underlayer. The surface roughness of the underlayer is related to the grain size distribution and surface roughness of Al film. The conventional wafer-level EM test results showed a similar trend with respect to Ti and TiN underlayers with less accuracy than those from package-level EM test results.

Effects of Ti and TiN underlayers on electromigration reliability of Al–Cu interconnects

The effects of Al underlayer between Ti and TiN on the electromigration (EM) reliability of Al stack film were compared. And both package-level and conventional wafer-level EM tests were performed. Microstructures of underlayer and Al films were characterized to understand the EM results. The surface roughness of the underlayer was related to the grain size distribution and surface roughness of Al film. The higher EM resistance of the Al stacks prepared with Ti underlayer can be best explained by their better Al (111) texture and grain size distribution than those with TiN underlayer.

Structural effects of Ti underlayer on CoCrPt magnetic films.

The effects of long-range and short-range orders of Ti underlayer thickness on the magnetic properties of sputtered Co72 Cr21 Pt7 films were investigated using synchrotron X-ray scattering and X-ray absorption near-edge structure spectroscopy. The results were consistent with that of magnetic measurements and X-ray photoelectron spectroscopy. For thin Ti underlayers (10 nm), the oxidation of Ti and significant mixing of other elements within this underlayer did not promote texture development, further resulting in poor texturing of magnetic films and undesirable magnetic properties. Increased crystallinity and texture of metallic Ti in thicker underlayers enhanced the magnetic peak alignment and its properties.

Fabrication of high frequency DC-DC converter using Ti/FeTaN film inductor

We fabricated a planar-type film inductor with good high frequency characteristics using a FeTaN soft magnetic film. While FeTaN films inherently show good soft magnetic properties and high saturation magnetization, addition of Ti underlayer with a combination of magnetic field annealing leads to an increase of anisotropy field (H/sub k/), thus improving high frequency characteristics. Planar-type spiral inductors using Ti/FeTaN films exhibit an inductance of /spl sim/1 /spl mu/H, resistance of /spl sim/2 ohm, and Q factor of 2.3 at 2 MHz. We also fabricated a hybrid ZVS-CV buck converter using the film inductor. The converter shows about 80% of the conversion efficiency at 1.2 MHz, which withstands a load current up to 300 mA.

Effects of texture and grain structure on electromigration lifetime of Al−Cu interconnects

The effects of Ti underlayer (collimated Ti vs. standard Ti) and Al deposition power (12 KW vs. 6 KW) on the electromigration (EM) lifetime of Ti/Al-0.5 wt. %Cu/Ti/TiN stack films were investigated The. (002) texture of standard Ti (s-Ti) was stronger than that of collimated Ti (c-Ti), and the Al (111) texture, grain size distribution, and EM lifetime of Al stack prepared with s-Ti underlayer were also better than those with c-Ti underlayer independent of the Al deposition power. The low power (6 KW) deposition led to better Al (111) texture, larger median grain size, and longer EM lifetime than did high power (12 KW) deposition independent of the type of Ti underlayer. Longer deposition time for low power sputtering allowed more time for the deposited Al atoms to be rearranged at more stable sites and to react with Ti, which resulted in a stronger Al (111) texture, larger median grain size, and a more uniform Ti−Al reaction layer. The (002) texture of the Ti underlayer is closely related to the Al (111) texture which is a major factor affecting EM lifetime.

Quantitative assessment of new high-speed steel substrate and PVD wear-resistant coatings

The paper presents the results of a quantitative evaluation of the carbide phases in a new high-speed steel (HSS) substrate and coatings deposited by a physical vapour deposition (PVD) method. The carbides were characterized using light (LM) and scanning electron microscopy (SEM) techniques, energy dispersive X-ray spectroscopy analysis and automatic image analysis, selective evaluation being possible due to differences in the gray level of the carbides' secondary electron images as well as in the shape and chemical composition of MC-, M 6C- and M 23C 6-type carbide particles. Gray images of pure TiN and TiN with titanium underlayer coatings were subjected to detection, morphological operations and measurements with original Met-Ilo software. It was found that TiN layers are of uniform thickness, while Ti underlayers are less regular.

Comparative Study on Wafer-Level and Package-Level Electromigration Reliability for Sub-Quarter Micron Logic Devices

ABSTRACTThe effects of Al underlayer between Ti and TiN on the electromigration (EM) lifetime of Al stack film were compared by the package-level and conventional wafer-level EM tests. The higher EM resistance of the Al stacks prepared with Ti underlayer can be best explained by their better Al (111) texture and grain size distribution than those with TiN underlayer. The surface roughness of the underlayer is related to the grain size distribution and surface roughness of Al film.

Formation of hillocks in Pt/Ti electrodes and their effects on short phenomena of PZT films deposited by reactive sputtering

The formation of hillocks was examined in various Pt/Ti electrodes with similar thermal histories, which were annealed prior to PZT film deposition by the sputtering method. The Pt electrode with no Ti underlayer did not exhibit hillocks. An increase of the Ti thickness or a decrease of the Pt thickness in the Pt/Ti electrodes were found to result in an increase in hillock density and the reduction of hillock size. A pre-annealing in Ar reduced the oxidation rate of Ti during the subsequent oxygen annealing, resulting in the reduction in density as well as the size of hillocks. The density and the size of hillocks were also reduced by a decrease of oxygen partial pressure during oxygen annealing. Hillocks in Pt/Ti electrodes are formed to relieve the compressive stress of the Pt films, which is mainly developed by the volume expansion of the Pt layer, due to the oxidation of diffused Ti along the Pt grain boundaries. A comparison of the short probabilities of the PZT films with the observed hillocks suggests that the electrical short of the PZT capacitors should not depend on the density, but on the size of hillocks.

Integrated CVD-PVD Al Plug Process for Sub-Quarter Micron Devices: Effects of Underlayer on the Via Filling and the Microstructure of the Al Film

AbstractThe integrated CVD-PVD Al plug process was successfully applied to a sub-quarter micron device for the simultaneous formation of plugs and wires. The effects of the underlayer on the via filling and the microstructure of the CVD-PVD Al films were investigated. Three types of underlayers were examined in this work: the Ti film deposited by the ionized PVD (I-PVD) method, the MOCVD TiN film stacked on the I-PVD Ti film, and the PVD Al film deposited on the I-PVD Ti film. Excellent via filling was achieved by employing the MOCVD TiN/I-PVD Ti or the PVD Al/I-PVD Ti as an underlayer. When only I-PVD Ti film was used as an underlayer, complete via filling was not obtained, because the CVD Al film sealed the top of vias. The CVD-PVD Al film deposited on the PVD Al/I-PVD Ti underlayer also showed excellent crystallographic texture of Al <111> and surface morphology, which is superior to those of the CVD-PVD Al film deposited on the MOCVD TiN/I-PVD Ti underlayer.

Ｎｉ系合金面内記録層を有する垂直面内複合型媒体の作製

Perpendicular/longitudinal composite media having a Ni(-Cr) alloy as a longitudinal magnetic underlayer were prepared by dc-magnetron sputtering. All the diffraction peaks observed in XRD experiments were Ni(111) and Co(002), indicating that composite media without an intermediate layer were successfully prepared. To obtain a higher S/N value, it was revealed that it is effective to decrease the thickness and saturation magnetization of the Ni alloy longitudinal magnetic layer. However, using a Ti underlayer caused higher medium noise.

ホローカソード方式イオンプレーティング法で作製したＴｉ／ＴｉＮ多層皮膜の耐食・耐摩耗性

Attempts have been made to reveal a desirable design for a Ti/TiN multilayer as a protector for corrosion and wear at-tacks. Multilayers of Ti/TiN were deposited on two types of chromium molybdenum steels and on a high speed tool steel by switching on and off a reactive gas feed valve. Layer thicknesses were determined by scanning electron microscopy and also estimated from Ti depth profiles obtained by grow discharge atomic emission spectrometry (GD-AES). Corrosion resisitance was evaluated by two types of tests : one is the method where the coated steels were exposed to the gas generated through hydrolyzing a resin mixture of ABS and PVC at 443 K under a pressure of 2.87 MPa, and the other is the critical passivation current density method where a deaerated solution of 0.5 kmol/m3H2SO4-0.05 kmol/m3KSCN was used as an electrolyte. Ttribology tests were carried out under unlubricated conditions with a reciprocating type testing apparatus. Substrate current is a fairly useful indicator for precise control of layer thickness. GD-AES offers an exact estmation of layer thickness in the matter of minutes, for example, only within 0.4 ks for a multilayer of 56 μm in total thickness. Corrosion tests show that TiN coatings with a thicker Ti underlayer are more protective and that the multilayer coatings possess a better protective function when the ratio of cumulative thickness of Ti layers to that of TiN layers, ∑XTi to ∑XTiN, is within 1 to 2. It is possible that an increase in thickness of the outer TiN layer brings about reduction of protection performance. With an increase in intrinsic compressive stress in the TiN layer, abrasive damage progresses more rapidly toward a substrate. The Ti layer contacting to the outer TiN layer suppressed the progression; for multilayers, therefore decreasing the thickness of the outer TiN layer resulted in a decrease in wear loss.

Co-Cr-Ta perpendicular magnetic recording media using Pt seed layer

Co/sub 77/Cr/sub 20/Ta/sub 3/ films were deposited on a Pt seed layer, and their crystallographic and magnetic characteristics were investigated. The Co-Cr-Ta/Pt bilayered films deposited at the substrate temperature of 250/spl deg/C revealed excellent c-axis orientation and exhibited high perpendicular coercivity. For the Co-Cr-Ta/Pt/Ti trilayered films, Ti underlayer promoted fine granulation in the Pt layer and improved magnetic characteristics of the ultra-thin Co-Cr-Ta recording layer. Media noise level of the Co-Cr-Ta/Pt disk was small at high recording density range. The Co-Cr-Ta/Pt bilayered films are useful for fabrication of perpendicular magnetic recording media.

Dense fully 111-textured TiN diffusion barriers: Enhanced lifetime through microstructure control during layer growth

Low-temperature deposition of TiN by reactive evaporation or sputter deposition onto amorphous substrates leads to highly underdense layers which develop mixed 111/002 orientations through competitive growth. In contrast, we demonstrate here the growth of low-temperature (450 °C) fully dense polycrystalline TiN layers with complete 111 texture. This was achieved by reactive magnetron sputter deposition using a combination of: (1) highly oriented 25-nm-thick 0002 Ti underlayers to provide 111 TiN orientation through texture inheritance (local epitaxy) and (2) high flux (JN2+/JTi=14), low-energy (EN2+≃20 eV), N2+ ion irradiation in a magnetically unbalanced mode to provide enhanced adatom diffusion leading to densification during TiN deposition. The Ti underlayers were also grown in a magnetically unbalanced mode, in this case with an incident Ar+/Ti flux ratio of 2 and EAr+≃11 eV. All TiN films were slightly overstoichiometric with a N/Ti ratio of 1.02±0.03. In order to assess the diffusion-barrier properties of dense 111-textured TiN, Al overlayers were deposited without breaking vacuum at 100 °C. Al/TiN bilayers were then annealed at a constant ramp rate of 3 °C s−1 to 650 °C s−1 and the interfacial reaction between Al and TiN was monitored by in situ synchrotron x-ray diffraction measurements. As a reference point, we find that interfacial Al3Ti formation is observed at 450 °C in Al/TiN bilayers in which the TiN layer is deposited directly on SiO2 in a conventional magnetically balanced mode and, hence, is underdense with a mixed 111/002 orientation. However, the onset temperature for interfacial reaction was increased to 610 °C in bilayers with fully dense TiN exhibiting complete 111 preferred orientation.

Microstructure and crystallographic texture of reactively sputtered FeTaN films

X-ray pole figure analysis is used to measure the crystallographic texture of FeTaN as a function of nitrogen content. The pole figures are used to semi-quantitatively describe the texture with the use of the orientation distribution function. The grain structure and texture is further analyzed with cross-sectional transmission electron microscopy. The preferred crystallographic orientations are found to be mostly randomly oriented, except for fiber textures that range from a (111) for FeTa to a weak (110) for FeTaN. The effect of a Ti underlayer is also described which greatly enhances the (110) fiber texture in all of the films studied.

(Ti,Cr)N and Ti/TiN PVD coatings on 304 stainless steel substrates: wear-corrosion behaviour

When hard nitrides coatings work in aggressive environments, wear phenomena occur in conjunction with corrosion processes; hence the characterisation of wear and corrosion resistance, considered as two distinct aspects, cannot be regarded as representative of the real degradation process, where the interactions between the two phenomena become extremely important. In this work wear-corrosion tests were performed by means of a laboratory-made apparatus, where the electrochemical characterization can be easily carried out. TiN coatings (with and without the presence of a Ti underlayer) and (Ti,Cr)N coatings were tested under different wear conditions in a sodium chloride solution. The results were compared and the different behaviour was interpreted in terms of film texture and residual stresses due to the PVD process. The (Ti,Cr)N deposits, which have the best intrinsic corrosion resistance, turned out to be the less resistant coatings to the wear-corrosion process, probably because residual stress was much higher than in TiN, making the coating more brittle and poorly adherent to the substrate. The TiN/Ti samples showed the best behaviour under wear-corrosion, which can be explained by a better adhesion of the coating, enhanced by the titanium underlayer. Moreover, the presence of the Ti underlayer proved to be effective in reducing the residual stresses in the TiN layer.

Role of a paramagnetic amorphous CoZr seed layer in CoCrPt/Ti perpendicular recording media

A fresh CoZr45 paramagnetic amorphous layer of 20 nm thickness is introduced as a seed layer prior to the Ti underlayer deposition on glass substrate in CoCrPt/Ti perpendicular recording media. By the fresh layer introduction, the thickness of Ti underlayer could be reduced to 100 Å to obtain good perpendicular magnetic properties. The cause of this reduction of the critical Ti underlayer thickness is the formation of a more smooth and absorbed impurity free surface by the CoZr layer deposition. This ensures better aligned and finer Ti grain formation at an early stage. Details of the improvements of magnetic properties are discussed. In the second half, we are reporting high Ku behaviors of the CoCrPt/Ti films when the magnetic layers are thinner than 200 Å. The high Ku behavior was associated with the (10.0) lattice expansion of the Co alloy to maintain coherency with (10.0) lattice of the Ti film at the interfaces. These will be discussed.

Enhancement of magnetic anisotropy of nanocrystalline FeTaN films by Ti underlayers and magnetic field annealing

Evolution of magnetic anisotropy in a FeTaN film was investigated as a function of annealing temperature, induction of magnetic field, and the addition of a Ti underlayer. The Fe78.8Ta8.5N12.7 films studied in this work are deposited as amorphous, and their soft magnetic properties evolve through the crystallization during postdeposition annealing. The films show a strong isotropy at all annealing temperatures with and without magnetic field induction. Employment of a Ti underlayer greatly enhances the uniaxial anisotropy when combined with a magnetic field annealing. The enhanced anisotropy leads to a significant improvement of high frequency response through an increased ferromagnetic resonance frequency.