Imaging Of Chip Surface Structure And Microwave Field Based On Atomic Force Microscopy

With the rapid development of microelectronics technology,microwave integrated circuits（IC）are widely used in mobile communications,millimeter wave radar,navigation and other fields.With the continuous progress of integrated circuit design and fabrication process,the scale of integrated circuits is shrinking,the circuit layers are increasing,and the functions are becoming increasingly complex,which puts forward new requirements for EMC detection and fault analysis of integrated circuits.The existing microwave near-field imaging technology has the disadvantages of low spatial resolution and narrow operating band,which can no longer meet the current requirements for target detection.Atomic Force Microscope（AFM）is an instrument that can be used to obtain the surface morphology of a sample by the interaction force between the probe and the sample,and can be used to characterize parameters at the atomic level.The chip circuit can be directly measured by combining AFM and microwave technology to obtain near-field scanning microwave imaging,which can help verify the correctness of the design and improve the reliability and stability of the chip.In this paper,we propose to develop a microwave near-field imaging system for in-situ,high-power,non-damaging measurements using AFM technology and apply it to microwave devices such as microwave integrated circuits.The details of the paper are as follows:1.In this paper,the working principle of AFM is studied in detail,and combined with microwave technology,the chip surface structure and microwave field imaging method is proposed.By using the different reflection coefficients of microwaves on different materials,we can achieve point-by-point detection of the test area with AFM and characterize the sample morphology from S₁₁ amplitude.Combined with the microwave coupling principle,we use the value of S₁₁ peaks generated by the coupling of two microwave signals with close frequencies to realize the characterization of the microwave field on the sample surface.2.In this paper,we study the near-field scanning microwave imaging system based on AFM and build a set of experimental stage that can be used for chip surface structure and microwave field imaging.Using the light deflection principle to obtain the placement angle and position of the laser and the four-quadrant detector,and then designing the photoelectric detection module to achieve the detection of the probe position.By analyzing the characteristics of the piezoelectric ceramic tube,the length of the required scanning tube is calculated according to the preset scanning range and combined with the fast convergence motor to form the sample scanner.The photoelectric detection module,scanner module and software control are developed in this paper to complete the integration of the whole imaging system.3.Conduct imaging experiments of chip surface structure and microwave field using the imaging system built independently.Analyze and compare the chip surface structure field imaging before and after data synchronization to verify that the imaging system test results data are stable and not shifted.Surface microwave field imaging of microwave array chip,combined with the results obtained from simulation,to verify that this imaging system can be applied to chip surface microwave field inspection.By comparing the difference between the chip radiation microwave magnetic field test results and simulation results at different power of the input signal,it is verified that the imaging system can be applied to high power chip surface microwave field detection.This project intends to build a microwave near-field imaging system based on AFM as the core,and test it high power microwave near-field imaging effect on multiple chips to provide a new method for EMC testing and failure analysis.