TABLE OF CONTENTS We discussed earlier that SiP means different things to different people. A similar situation occurs for the IPN. This section will focus on silicon and GaAs small integrated passive networks. However, a simple resistor attenuator comprising three resistors in one part can be considered an integrated passive network by strict definition [17]. Others have used Al 2O 3 as a base material instead of silicon or GaAs with similar processing steps and results as the silicon and GaAs approaches [18].
The advantages of silicon and GaAs substrates are the fine features, small size, and capacitor density. The line widths and spacing can be reduced to 10 m, and the capacitor density is 550 pF/mm 2 [19]. The metal type and thickness as well as the bulk silicon material have plagued attempts to adapt this technology in the past. Pure silicon has a high resistivity of 250,000 ?cm, which is very good for passive networks. Unfortunately, it has a large temperature coefficient of 73,000 ppm/ C and also varies dramatically with impurities [20]. A 25- m-thick silicon dioxide layer that confines the electromagnetic fields within this low loss dielectric layer has been added for implementing passive RF circuits [21]. In addition, the metal systems have moved from aluminum to copper, and the thickness has increased to 10 m. This allows for passive networks with similar performance to LTCC and laminate.
Capacitors are made through a thin layer of silicon nitride. Although silicon nitride has...
