High Perfprmance On Chip Spiral Inductors Research Base On Thick Cu Process

The spiral inductor is one of the Key components in RF device. Theresearch on the silicon (Si)-based spiral inductor has drawn more and moreattention in past several years. Adopting the advanced standard Si-basedCopper (Cu) interconnection technology provides the opportunity to meetthe needs of manufacturing low cost and total integration RF device andcircuit. This study developed a thick Cu process based on the singledamascene Cu interconnection technology, designed and taped-out a seriesof on-chip inductor based on the thick Copper process, tested and analyzedthe single-loop inductor and differential inductor, completed the parameterextraction and simulation model building for differential inductor using theself-inductance parameter method, and fulfilled the customer requirementsof RF integration circuit.This dissertation has achieved the followings:Based on the electromagnetic field theory, the study systematicallyanalyzed the deterioration mechanism of the on-chip spiral inductor andthe inductor quality factor “Q” Value of multiple structure parameters,employed the3-D high frequency simulation tool HFSS and simulatedmultiple inductors with a variety of fabrication processes and structureparameters, verified the importance of the thick Cu technology forimproving the performance of advanced on-chip inductor, and designed aseries of inductors for evaluation. Based on the0.13μm Cuback-end-of-line (BEOL) single damascene process, this dissertationdeveloped the key etch and chemical Mechanical Polishing (CMP)processes for deep trenches with high aspect ratio, built-up the thick Cu process flow for manufacturing spiral inductors, fabricated3μm thick topmetal lines on200mm wafer. The sheet resistance (Rs) of the thick metalachieved6milliohms, realized the goal of manufacturing highperformance inductors.Test analysis and Model extraction. The dissertation employed theon-chip high frequency test system and tested large amount of on-chipspiral inductors made using the thick Cu process. The test results match thedesign specifications. The test results show that the on-chip inductor withthe inductance L of2.2nH achieves the “Q” value of16.6under theworking frequency of2.2GHz. Its performance is much better than theAluminum inductor.This dissertation completed the parameter extraction and simulationmodel building for differential inductors. The study employed aphysics-based, completed, and proportionally variable inductor model. The3-D variable model is able to precisely predict low frequencycharacteristics and contains corrected amended skin effect and proximityeffect. By comparing the difference of the simulation results and themeasurement data of the asymmetric inductor model, the model can lowerthe Q value and the L value error to less than10%for most inductors, wellmeets the requirements of the industry.