In search of higher density mim capacitor for GaAs RF power applications

Investigation and characterization have been performed on methods of obtaining higher density MIM capacitors for GaAs RF power applications in order to reduce die size. Single MIM capacitors using thin Si 3 N 4 as the dielectric material have been fabricated resulting in relatively high capacitance density, and which was further increased by fabricating the capacitor in a stacked configuration. When Ta 2 O 5 was used, the capacitance density is significantly increased. However, each of these methods has limitations and drawbacks. A stacked MIM capacitor can lead to higher defect density, and depending on the layout configuration and placement in the design, it can also lead to a lower capacitance density, inferior RF characteristics, and a larger total layout area. Even though Ta 2 O 5 has much higher capacitance density than Si 3 N 4 , the film has low breakdown field and high leakage current, and cannot be used in many GaAs RF power devices, where low leakage current and higher breakdown voltage are required. All the above, in addition to the manufacturability and reliability of these capacitors, need to be investigated before making any decision of what capacitor type and material to use.