Investigation Of Fabrication And Porperties Of The Frame Thin-film Inductor Based On The Closed Magnetic Circuit

With the rapid development of electronic technology, the integration of circuit system is becoming more and more demanding. The inductors as one of the three passive components would tend toward miniaturization and high frequency, and the research focuses on improve the inductance. A special magnetic core inductor with closed magnetic circuit was designed to reduce the magnetic flux leakage. The two kinds of thin-film inductors, whole magnetic film inductor and sandwich inductor, were designed for the comparison. The inductors with different structure magnetic core consist of the lower magnetic core layer, the lower insulating layer (ingredients polyvinylidene chloride with thickness of 40 um), the coil and the magnetic film in the coil center, the upper insulating layer and the upper magnetic core layer. The two parts of research have been carried out. First, Co and Cu thin films were prepared by DC magnetron sputtering method and SiO2 thin film were prepared by RF magnetron sputtering method. The effect of deposition process on the microstructure and properties of Co, Cu and SiO2 thin film was researched. Second, three kinds of thin film inductors were prepared by magnetron sputtering method. The influence of the magnetic core structure and thin film deposition process on equivalent inductance, parasitic capacitance, and loss factor in 1-3 MHZ frequency range was researched. The results are as following.1. The resistivity of Co film deposited with 60-132W sputtering power for 20-100min also decreases with the increase of sputtering power and time. Co thin film deposited with 96 W sputtering power for 60 min has dense surface morphology, and grows in columnar shape with a thickness of 510 nm. Co/Polyvinylidene chloride composite film is of soft magnetic, Ms=8.47A·m2/Kg.2. The resistivity of Cu film deposited with 40-80W sputtering power for 5-15min decreases with the increase of sputtering power and time. Cu thin film deposited with 60W sputtering power for 10 min has dense surface morphology, and grows in columnar shape with a thickness of 600 nm.3. The ambience with 5:2 argon/oxygen ratio is beneficial to the growth of SiO2 films with more denser morphology and more fine particles. But its growth rate is too slow to form the insulation film which could completely cover conductive Cu film.4. Compared with the whole magnetic film inductor and the sandwich inductor, the special magnetic core inductor has higher equivalent inductance, smaller parasitic capacitance and bigger loss factor, but its higher resistance of core film is favorable to reduce the eddy current loss. And the coverage area of magnetic core film has influence on the electrical properties of coil film. The smaller the coverage area, the smaller the coil resistance. So the smallest resistance of the special magnetic core inductor coils favors to reduce the copper loss of inductance.5. The parasitic effect of inductors increases as increasing sputtering power of Cu and Co film, but the influence on that of the special magnetic core inductor is smaller. When raising sputtering deposition power of Co film, the loss factor of the thin-film inductor decreases. When increasing sputtering deposition power of Cu film, the loss factor had no significant change.