Fabrication And Investigation Of Co₂Z Type Ferrite Films For High-frequency Applications

With the development of semiconductor technology and the emergence of integrated circuits in the 20th century, making miniaturization of electronic devices and the plane is necessary to carry into the traditional three-dimensional because of the bulk powder materials can not meet the requirements of new technologies, thin films materials has gradually become the mainstream use of electronic devices. Inductor is a kind of common electronic devices in integrated electronic systems, the electronic device could be small and plane with the emergence of thin films inductor, but thin films inductors are mainly using metal and alloy materials now. Metal and alloy thin films inductors with high electrical conductivity makes them a serious skin effect and eddy current losses, thereby affects the frequency range of its application, the ferrite materials are tracking much attentions of researchers because of their high resistivity and excellent reliability.Co2Z hexagonal ferrite thin films have good soft magnetic performance at high frequency, and reletively high resisitivity, so they can work at a frequency up to GHz range. It has been calculated that Co2Z type ferrite materials'the resonance frequency f can up to 3.4 GHz, making it a high-frequency chip inductor and ultra-high frequency resistance EMI countermeasure components of an ideal microwave material.We investigate the magnetic properties and structures of Co2Z type hexagonal ferrite thin films, the main conclusions are:1. Influence of thickness:We studied the film thickness from 100 nm to 1000 nm, the 100 nm thickness was found to be the best in terms of its magnetic properties, the saturation magnetization Ms is 250 emu/cc, the coercivity Hc is 180 Oe.2. Influence of oxygen pressure:We studied the partial pressure of oxygen which is from 0% to 20%, we found the sample in the pressure of oxygen of 20% has the best magnetic properties, and the saturation magnetization Ms is 289 emu/cc, coercivity Hc is 139 Oe.3. Influence of sputtering pressure:in the range of sputtering pressure, from 0.5 to 1.3 Pa, we found only in 1.0 Pa of sputtering pressure has the largest value of saturation magnetization Ms,250emu/cc and the lowest value of coercivity Hc,180 Oe.4. Influence of Barium content:We prepared ferrite thin films with different contents of Ba by either two-target alternate sputtering or single-target sputtering. Samples prepared by using two-target sputtering have larger saturation magnetization value Ms and the lower coercivity Hc than ones of single-target sputtering, and the crystal orientation is more obvious.5. Influence of sintering temperature:We sintering the samples from 800℃to 1280℃. It was found that samples sintered at 1280℃have the best magnetic properties, and formed a main peak of (1106) Z-phase. Thin films begin to form disordered strip crystals at 800℃. with the increasing sintering temperature, the crystal growth direction changed from perpendicular to the substrate surface, and caused the good growth of vertical flat hexagonal crystals at 1280℃.