Design and Implementation of High Precision and High Density Capacitor based on Silicon Integrated Passive Device Technology

Silicon-based integrated passive device (IPD) technology fabricates passive devices on the high resistivity silicon substrate by thin-film circuit process. Since IPD have unique advantages e.g. small size, good high frequency performance, high precision, high reliability and low cost, it is taking the place of traditional discrete passive device in electronic products application and has wide application in mainstream three-dimensional system integration in the future. In application, it is necessary to minimize the area occupied by the IPD in circuit layout in design and increase the electrical density of devices. Meanwhile, reducing the error between circuit design and real products to improve the precision of IPD is an important guarantee for engineering application. In this paper, three kinds of IPD capacitor (100pF, 10pF, 1pF) have been designed, simulated, fabricated, and measured by using high resistance silicon wafer as the substrate. A metal-isolation-metal (MIM) capacitor structure is used to obtain larger capacitance density and smaller component area. MIM capacitance is calculated through parallel plate capacitor equation approximately. The π type equivalent circuit model is used in the simulation of capacitor. Optimization design is proceeded to the geometric dimension, substrate conductance, metal conductance, dielectric layer’s dielectric constant and thickness of silicon-based IPD capacitor under limited conditions. The layouts of three kinds of capacitor (100pF, 10pF, 1pF) are designed and the corresponding EM simulation is performed. Real devices are fabricated by silicon-based IPD technology. The size of the real capacitor after incising is 1mm×1mm, which includes testing circuit. The capacitance value tested result shows that the measured capacitance value fit the designed value mainly. The errors between measured value and designed value of capacitor (100pF and 10pF) are within +2%, while the error between measured value and designed value of capacitor (1pF) is +8% which meet the requirement of design index. The capacitance density is about 550~577 pF/mm
²
which can satisfy the demand of engineering application. The design and implementation of high precision and high density capacitor based on silicon-based IPD technology lay the foundation for the integration of passive devices in system packaging.