| GaN materials have gradually occupied the strategic heights in communication,new energy electric vehicles,microwave medical imaging and other fields due to their advantages of wide bandgap,strong breakdown field and fast electron saturation drift.Device modeling is the core of device characterization and circuit design optimization,and accurate models are important for improving device and circuit performance and shortening development cycle.At present,the research on equivalent circuit model focuses on active devices GaN HEMT,but only the model of active devices is far from enough for the design of single-chip integrated circuits.In this thesis,the process development and equivalent circuit model of active and passive devices based on GaN process are studied,which lays a solid foundation for the simulation design of power amplifiers.First of all,based on the working principle and device structure of GaN device,the corresponding photolithography mask and complete process flow are designed.For the key process selection,secondary epitaxy and air bridge are experimentally developed,and obtains the circular arch air bridge by adjusting the parameters such as rotational speed of glue machine and baking temperature.And the DC performance and RF performance are tested by semiconductor analyzer and vector network analyzer to provide necessary data support for the subsequent equivalent circuit model.Then,the de-embedding parts used in on-chip de-embedding are designed and verified through simulation software,and the process and principle of on-chip de-embedding are elaborated.After analyzing the basic theory of transmission line,the equivalent circuit model of microstrip line is established by multi-stage cascade network,and the error of the model is less than 7 % in the range of 0.1-100 GHz.Combined with the process requirements and the basic equation of steady-state thermal flux,the physical size of thin-film resistor is quantitatively analyzed,and the corresponding "π" type equivalent circuit model is given.At the same time,the influence of medium thickness,air bridge length and air bridge width on MIM capacitance performance is simulated and analyzed,and the specific size of capacitance is determined.A double "T" type equivalent circuit model suitable for MIM capacitance in this thesis is proposed,and the model error is less than 5 %.Finally,by comparing the parameter fitting effect and frequency range of classic small signal equivalent circuit model,the appropriate small signal equivalent circuit model is selected.The parasitic parameters of the device are extracted by combining the test structure parameter extraction method,the multi-bias parameter extraction method and the algorithm optimization method.The model is verified by test data,the model error is less than 3.5 %. |
