• Journal of Industrial Technology
• /
• v.21 no.A
• /
• pp.221-229
• /
• 2001

The effect of Mo underlayer on the magnetic properties of CoCrTa/Cr films deposited on glass substrates were investigated. The coercivity increased and the coercivity squareness decreased by introducing Mo underlayer. The coercivity increase was attributed to the increase of in-plane c-axis orientation and magnetic isolation of Co grains deposited on Cr/Mo underlayer. The decrease of coercivity squarenesses seemed to be caused by the increase of magnetic isolation. The increase of magnetic isolation of Co grains was attributed to the diffusion of Mo atoms into grain boundaries of Co films and the physical isolation of Co grains. The coercivity of CoCrTa/Cr/Mo showed maximum values at Mo thickness of $400{\AA}$. The appearance of the maximum coercivity at that thickness was attributed to the development of strong $Co(10{\bar{1}}0)$ and $Co(10{\bar{1}}1)$ preferred orientation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.208-211
• /
• 2000

We prepared Co-Cr-Ta and Co-Cr-Ta/Ti thin film for perpendicular magnetic recording media by facing targets sputtering system (FTS system). Ti underlayer effects on crystallographic and magnetic characteristics of Co-Cr-Ta perpendicular magnetic recording media have been investigated. Crystallgraphic and magnetic characteristic of prepared thin films were evaluated by x-ray diffractometry(XRD), vibrating sample magnetometer(VSM) and kerr hysteresis loop measurement. The coercivity and anisotropy field increase by introduced Ti underlayer when substrate temperature is higher than 150$^{\circ}C$. The c-axis dispersion angle and grain size of Co-Cr-Ta/Ti thin film is decrease than Co-Cr-Ta when substrate temperature is higher than 100$^{\circ}C$. Consequently, the use of a Ti underlayer highly orientated can be improved crystallographic and magnetic characteristics of Co-Cr -Ta perpendicular media layer.

• Journal of the Korean Magnetics Society
• /
• v.5 no.5
• /
• pp.614-617
• /
• 1995

Thin CoCrTa/Cr films were deposited on glass substrates at $280^{\circ}C$ with or without Al underlayer. The coercivity of CoCrTa increased considerably by introducing an Al underlayer. The grain size of Cr thin film deposited on Al underlayer became smaller than that of Cr thin film deposited on glass substrate. The grain size of CoCrTa thin film was determined by Cr grain size. The cause of the coercivity increase seems to be associated with the refinement and uniform distribution of CoCrTa grains.

• Journal of the Korean Magnetics Society
• /
• v.9 no.4
• /
• pp.203-209
• /
• 1999

Effects of Mo and Si addition in Cr underlayer on magnetic properties of CoCrTa/CrMo and CoCrTa/Si thin films media were investigated. Thin films were prepared with DC magnetron sputtering system. The thickness of CoCrTa magnetic layer and Cr underlayer were fixed at 300 $\AA$ and 700 $\AA$, respectively. The substrate heating temperature was kept constant at 26$0^{\circ}C$ for both magnetic layer and underlayer preparation. The coercivity increase of CoCrTa film was realized due to Mo addition in Cr underlayer. Si addition made a small decrease in coercivity. Coercivity increase seems to be attributed by the improvement of preferred orientation of Cr(200) plane. It is found that lattice fit between Cr(200) and CoCrTa(1120) of CrMo underlayer is better than that of CrSi underlayer. This small misfit may also contribute coercivity increase.

• Journal of Magnetics
• /
• v.9 no.4
• /
• pp.116-120
• /
• 2004

Hexagonal barium-ferrite ($BaFe_{12}O_{19}$, magnetoplumbite structure; BaM) film with perpendicularly c-axis orientation was successfully deposited on (100) silicon substrates with an MgO (111) underlayer by rf diode sputtering and in-situ heating at $920^{\circ}C$. The magnetic and structural properties of 0.27 ${\mu}m$ thick BaM films on MgO (111) underlayers were compared to films of the same thickness deposited onto single-crystal MgO (111) and c-plane ($000{\ell}$) sapphire ($Al_2O_3$) substrates by vibrating sample magnetometry (VSM), x-ray diffractometer (XRD), and atomic force microscopy (AFM). The thickness dependence of MgO (111) underlayers on silicon wafer was found to have a large effect on both magnetic and structural properties of the BaM film. The thickness of 15 nm MgO (111) underlayers produced BaM films with almost identical magnetic and structural properties as the single-crystal substrates; this can be explained by the lower surface roughness for thinner underlayer thicknesses. The magnetization saturation ($M_s$) and the ratio $H_{cII}/H_{c{\bot}}$ for the BaM film with a 15 nm MgO (111) underlayer is 217 emu/cc and 0.24, respectively. This is similar to the results for the BaM films deposited on the single-crystal MgO (111) and sapphire substrates of 197 emu/cc and 0.10, 200 emu/cc and 0.12, respectively. Therefore, the proposed MgO (111) underlayer can be used in many applications to promote c-axis orientation without the cost of expensive substrates.

• Journal of the Korean Magnetics Society
• /
• v.18 no.3
• /
• pp.94-97
• /
• 2008

We investigated how the magnetic anisotropy in $[Co(2\;{\AA})/Ni(8\;{\AA})]{\times}N$ multilayers varied with the type and thickness of an underlayer. The magnetic measurements clearly showed that the perpendicular magnetic anisotropy could be developed in the Co/Ni multilayer by adopting an underlayer with [111] texture. The coercivity of the Co/Ni multilayer increased from 99 Oe to 430 Oe as the thickness of an Au underlayer increased from $50\;{\AA}$ to $500\;{\AA}$. The increase in coercivity is ascribed to the development of the stronger [111] texture in the Co/Ni multilayer as an Au underlayer gets thicker.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.10 no.1
• /
• pp.17-22
• /
• 2000

A quaternary alloy film of $CoCr_{16.2}Pt_{10.8}Ta_4$was investigated for its magnetic properties and c-axis orientation with and without Ti underlayer. Additional elements such as Ta, Pt have been frequently introduced in CoCr alloy film for perpendicular recording as a means of improving magnetic performance. It has been reported that the addition of Pt and Ta in CoCr increase the coercivity and the magnetic isolation of columnar grains, respectively. However, CoCrPtTa perpendicular magnetic layer should be more increased its perpendicular magnetic anisotropy than at present for the application of ultrahigh recording density. The improvement of underlayers and substrate materials is one of the promised schemes to intensify the perpendicular magnetic anisotropy. In this study, the insertion of Ti underlayer shows the remarkable improvement of c-axis orientation compare with the direct deposition on the bare glass. The mechanism about this effect of Ti underlayer on CoCrPtTa is not to be clarified yet. Meanwhile, it is found that the magnetic domain of CoCrPtTa on 20 nm Ti underlayer has the continuous stripe pattern but the one of CoCrPtTa on 90 nm Ti underlayer shows the discrete mass type from the results of MFM investigation. This phenomenon is to be a distinct evidence that the improvement of perpendicular anisotropy by the adoption of Ti underlayer is originated from the reinforcement of the grain boundary segregation in CoCrPtTa alloy. Moreover, the transition of the M-H hysteresis pattern with the thickness of Ti underlayer indicates that the major contribution of Ti underlayer is not the magnetocrystalline anisotropy but the shape anisotropy due to the formation of uniform columnar grains by the nonmagnetic alloy segregation.

• Journal of the Korean Magnetics Society
• /
• v.15 no.4
• /
• pp.226-230
• /
• 2005

In this research, magnetic properties and annealing effects of the spin valve structures were investigated, which have Ta underlayer deposited with Ar and $N_2$ gas mixture. Also, TaN underlayer as a diffusion barrier and the substrate were investigated. The structure of the spin valve was Si($SiO_2$)/Ta(TaN)/NiFe/CoFe/Cu/CoFe/FeMn/Ta. Deposition rate was decreased and resistivity and roughness of the TaN films were increased as the $N_2$ gas flow was increased. The XRD results after high temperature annealing showed that Silicides were created in Si/Ta layer, but not in Si/TaN layer. Magnetoresistance ratio (MR) and exchange coupling field ($H_{ex}$) were decreased when the $N_2$ gas flow was increased over 4.0 sccm. The MR of the spin valves with Ta and TaN films deposited with up to 4.0 sccm of $N_2$ gas flow was increased about $0.5\%$ until the annealing temperature of up to $200^{\circ}C$ and then, decreased. TaN film deposited with 8.0 sccm of $N_2$ gas flow showed twice the adhesion of the Ta film. The above results indicate that with 3.0 sccm of $N_2$ gas flow during the Ta underlayer deposition, the magnetic properties of the spin valves are maintained, while the underlayer may be used as a diffusion barrier and the adhesion between the Si substrate and the underlayer is increased.

• Journal of the Korean Vacuum Society
• /
• v.8 no.1
• /
• pp.31-35
• /
• 1999

In this paper, the lifetime dependence as a function of the line length of Al-1%Si thin film interconnections due to electromigration in semiconductor devices was studied. Al-1%Si thin film interconnections with a pattern of straight type were formed by using a standard photolithography process. The test patterns manufactured have line lengths in the range of 100 to 1600 $mu extrm{m}$. Al-1%Si thin film interconnections with Ti underlayers showed longer lifetime than those without Ti underlayers. Ti underlayers are believed to improve electromigration resistance resulting in a longer lifetime in Al-1%Si thin film interconnections. The dependence of lifetime on the line length in Al-1%Si/Ti thin film interconnections shows a saturation tendency near 800 $\mu\textrm{m}$ line length.

• Journal of the Korean Magnetics Society
• /
• v.12 no.3
• /
• pp.94-98
• /
• 2002

Sputtering conditions and various underlayer such as Al, Cu, Ni, Cr, Ag, Mg, Fe, Co, Pd, Au, Pt, Mo and Hf were investigated for coercivity enhancement of 20 nm Ti/CoCrPt thin films in order to increase the coercivity of the films thinner than 20 nm. Among them, Ag and Mg were effective to increase the coercivity. Particularly 2 nm Ag was very effective to increase the coercivity and nucleation field as well as to reduce ${\alpha}$ value in CoCrPt thin film such that the coercivity of 2 nm Ag/18 nm Ti/10 nm CoCrPt film was 2200 Oe. However, it seemed that other coercivity enhancement mechanism operated in CoCrPt films because Ti (002) preferred texture was not developed with Ag underlayer contrary to a general expectation. And the coercivity and nucleation field were decreased when glass substrate with rougher surface was used.