sức đề kháng của các plug kim loại. Việc so sánh giữa mô hình lỗ thông qua và các dữ liệu đo của bộ, thể hiện trong hình 9,12, cho thấy một mối tương quan tuyệt vời. Bảng 9,2 Thông qua lỗ nhúng trong TRL tiêu chuẩn và mô hình (b) của một lỗ thông qua. | 400 Lumped Elements for RF and Microwave Circuits and Ta Au for hybrid MICs and Cr Au and Ti Au for MMICs. The selection of the conductors is determined by compatibility with other materials required in the circuit and the process required. A typical adhesion layer may have a surface resistivity ranging from 500 to 1 000 V square but does not contribute to any loss because of its extremely small thickness. Dielectric Materials Dielectric films in MICs are used as insulators for capacitors protective layers for active devices and insulating layers for passive circuits. The desirable properties of these dielectric materials are reproducibility high-breakdown field low-loss tangent and the ability to undergo processing without developing pinholes 7 . Table shows some of the properties of commonly used dielectric films in MICs. SiO is not very stable and can be used in noncritical applications such as bypass and dc blocking capacitors. A quality factor Q of more than 100 can be obtained for capacitors using SiO2 Si3N4 and Ta2O5 materials. These materials can be deposited by sputtering or plasma-enhanced chemical vapor deposition CVD . For high-power applications a breakdown voltage in excess of 200V is required. Such capacitors can be obtained with fairly thick dielectric films 1 mm that have a low probability of pinholes. Resistive Films Resistive films in MICs are required for fabricating resistors for terminations and attenuators and for bias networks. The properties required for a resistive material are good stability a low TCR and sheet resistance in the range of 10 to 2 000 V square 7 8 . Table lists some of the thin-film resistive materials used in MICs. Evaporated nichrome and tantalum nitride are the most commonly used materials. Table Properties of Dielectric Films for MICs Material Method of Deposition Relative Dielectric Constant e Dielectric Strength V cm Microwave Q SiO Evaporation 6-8 4 X 105 30 SiO Deposition 4 107 100-1
