Design Of Vertical Interconnect Structure In Millimeter Wave Wafer Level Packaging

With the rapid development of modern electronic packaging technology,the overall development is along the direction of higher integration,higher performance,higher compatibility,higher reliability and more functions.In recent years,with the further increase in user demand and the further increase in system integration,the reduction of the minimum feature size of transistors has become slower and slower,which makes the development of integrated circuits posed a higher challenge.The Through Silicon Via(TSV)technology in the three-dimensional integration technology can reduce the length of the signal connection in the structure;increase the transmission bandwidth;reduce the volume of the device and improve the integration;realize the integration of heterogeneous devices,so industrial The industry and academia generally believe that: TSV can achieve high-density integrated packaging,and can be used as a way to continue Moore's Law.In the production process of TSV interposer boards,the process is often limited.When making TSV vias with large aspect ratios,in addition to the increase in process cost,they are also easy to fill incorrectly,which affects the microwave transmission performance of interposer boards.Based on the study of vertical interconnection and wafer bonding,this paper analyzes the microwave characteristics and bonding mechanism of the transition structure,and finally designs a vertical interconnection structure to solve the low loss of inter-layer signal interconnection during micro-system three-dimensional integration.Transmission problem.In this paper,a vertical interconnection structure based on TSV interposer board and Cu/Sn bonding is designed and prepared.First,this paper studies the transmission line theory and the structure of vertical vias,analyzes the equivalent circuit of vias and the factors affecting TSV transmission performance,and finally uses two TSV quasi-coaxial structures to make vertical interconnections on two layers of high-resistance silicon.And use HFSS to model and simulate TSV quasi-coaxial structure,vertical interconnection structure and vertical interconnection structure with embedded chips.Secondly,considering that it is more difficult to directly make TSV vias with high aspect ratio,and there is a risk of incorrect filling,according to the limitations of actual process conditions,this article chooses to prepare two TSV adapters with an aspect ratio of 5:1.The board is made into a whole through Cu/Sn bonding.This article focuses on TSV through-hole process,coplanar waveguide and pad manufacturing process,and Cu/Sn bonding process.Some of the process steps are compared with other solutions.Finally,a complete process is designed to make the transfer board.The prepared samples were packaged on an LTCC substrate and tested for connectivity and performance.It was concluded that the input and output standing waves were less than 1.2 in the 1-40 GHz frequency band.Finally,in order to verify the integration,a four-channel transmitter module was designed.The real object is processed,tested and analyzed,and the transmission gain of the channel meets expectations within the working frequency range.The test results verify that the designed vertical interconnection structure has good microwave transmission performance and can be integrated into a microwave integrated circuit module.