Arai, “ A new 1 MHz-9 GHz thin-film permeameter using a side-open tem cell and a planar shielded-loop coil,” Trans. equation reminds us that μ r ′ = M s/ H k, in a static and low-frequency magnetic field as well as f F M R = ( γ / 2 π ) × ( M s H k / μ 0 ) 1 / 2 and μ r ′ × f F M R 2 = c o n s t a n t for a magnetic film with uniaxial anisotropy. A magnetic material with high M s and H k high is essential to realize higher f FMR. Where ω r is the angular FMR frequency, M s is the saturation magnetization, H k is the anisotropic magnetic field, γ is the gyro-magnetism constant, α is the Gilbert damping constant. gives the formulas of frequency-dependent permeability as follows: μ r ′ = 4 π M s H k ω r 2 ( ω r 2 − ω 2 ) ω r 2 ( ω r 2 − ω 2 ) 2 + ( 4 π λ ω ) 2 + 1 Fukunaga, “ Jisei zairyo (magnetic material),” Koudansha Sci. The Landau-Lifschitz-Gilbert (L.L.G.) equation 6 6. The physical description of the permeability consists of real and imaginary parts, μ r′ and μ r″, respectively μ r = μ ′ / μ 0 ′ = μ r ′ − j μ r ″ it was estimated that the degree of transmission loss decrease at 16 GHz would be 5 %.įrequency dispersion of permeability gives the basis of magnetic thin-film applications in the RF range. in order to meet high throughput mass productivity requirements. Yamaguchi, “ Skin effect suppression for cu/cozrnb multilayered inductor,” J. Endo, “ Skin effect suppression in multi-layer thin-film spiral inductor taking advantage of negative permeability of magnetic film beyond fmr frequency,” in Proc. Burghart, “ Magnetic-multilayered interconnects featuring skin effect suppression,” IEEE Electron Device Lett. proposed a electroplated Cu/NiFe multi-layer, instead of sputter-deposited thin film in literature, 3–5 3. Nakayama et al., “ Skin effect suppressed ni-fe/cu electroplated multilayer wiring for high data-rate and low delay-time i/o interface board,” IEEE Trans. proposed a design to set the volume average of permeability to be 0 in an alternately multi-layered structure of metal/magnetic thin film, taking advantage of negative permeability beyond the FMR frequency. Vroubel, “ Suppression of skin effect in metal/ferromagnet superlattice conductors,” J. As a technique for suppressing skin effect loss, a multilayer transmission line using a negative permeability material, which has negative permeability because the response of the magnetic moment inside the material is delayed with respect to the magnetic field cange at high-frequency, is proposed. Therefore, it degrades the device performance. The skin effect, which is known as the current crowding to the surface of a conductor, raises up ac resistance by reducing the effective area flowing the current. The skin effect loss is a problem because the loss increases at high frequency. Compared with Cu conductor, the top and bottom surface current densities become low, and depth center current density becomes slightly high for the multi-layer, showing the skin effect is suppressed.Ī loss reduction in a high-frequency transmission line is needed for high-speed and low-delay I/O board. By offsetting the phase change of current density, a lower loss structure could be determined. Compared to conventional thickness by a constant ratio 1), in our proposal 2), we estimated that the loss would dropped to 92% in optimal thickness. 2) Optimal stacking determined by changing the thickness of each layer.
1) Total number of layers was 33 and total thickness was 12.67 μm by a constant ratio, Cu: t N = 0.51 μm and NiFe: t F = 0.25 μm. The loss suppression was compared under the following conditions. The top and bottom surface layers are Cu layers. The Cu and NiFe films are alternately stacked to form the multi-layer. Cu and NiFe were selected as metal conductor material and negative permeability magnetic material, respectively. Also it is expanded to low loss design technology.
A major challenge in this paper is to propose an electromagnetic field calculation theory for rectangular multi-layer transmission line, verify it under the same conditions, clarify a lower loss structure by changing thickness of each layer. In previous research, it was demonstrated that suppression of the skin effect by electroplated conductor/magnetic multi-layer, and estimated that the degree of transmission loss decrease at 16 GHz would be 5 %. This proposal will overcome the difficulty of further reducing the transmission losses on the I/O board with vert >vert 50 Gb/s data rate. This paper proposes a new application of skin effect suppression technology for long wiring on high-speed & low-delay I/O board.
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