Design And Fabrication Of MEMS Vertical Probe

Wafer testing is an important part of the semiconductor manufacturing industry.It can not only check manufacturing defects and process yield,but also avoid packaging waste.The probe used in wafer testing is an important component between the tester and the die under test for communication.To solve the matter of testing I/O pads with smaller pitch and higher density,it is important to study the MEMS vertical probe.This thesis designed a vertical probe made of composite materials and fabricated by MEMS technology.The research mainly includes:Aimed at requirements for testing in advanced packaging conditions such as 3D packaging,under which pads or bumps are with fine pitch,high density and small size,a MEMS vertical probe structure with stable needle marks and flexibility in vertical direction was designed by analyzing vertical probe testing principles and comparing different MEMS probe structures.Faced with long life and low maintenance requirements,a metal composite material for MEMS vertical probes with high conductivity,high hardness and easy cleaning characteristics was proposed.The performance of the material was tested after subsequent probe fabrication.Young's modulus of the material is 64.54 GPa.The Poisson's ratio is0.44.The tensile strength is 1132MPa.The electrical resistivity is 3.13×10^-9?·m and the electrical conductivity is 3.19×10⁸ S/m.Analyzed and optimized probe's geometry by finite element method.The final design of the MEMS vertical probe structure was simulated by finite element analysis software for its mechanical and electrical properties.The maximum surface equivalent stress of the probe is 846.1MPa and the maximum contact force is 4.76gf under the overdrive of 0¹27?m.Under conservative estimates,the fatigue life of the final structure was 135,000 times.The electrical characteristics of the structure were analyzed under ideal conditions.The structure has an average electrical resistance of about 5.33 m?and has excellent electrical characteristics.The designed MEMS vertical probe was fabricated by UV-LIGA technology.The process optimizations were carried out to solve problems of the gap of size,the surface quality and the internal stress of the structure.After the probe was fabricated,the properties of the composite was tested.A mechanical test platform was built to test the contact and cycle life of the fabricated MEMS vertical probe structure.It was verified that the designed MEMS vertical probe can work normally in the 76.2?m over drive and can reach 200,000 cycle life in this working over drive.The cross-sectional side length of the designed MEMS vertical probe is less than50?m.According to the results of mechanical experiments,the working over drive of the MEMS vertical probe is 76.2?m,and the contact force is 5.14gf at this time.The service life of the MEMS vertical probe is about 200,000 times within the working over drive.