The Research On Key Technologies Of High-density 2.5D TSV Interposer

The 2.5D through silicon via(TSV)interposer process technology based on vertical through-via interconnection,redistribution layer(RDL),micro-bump and other processes is currently defined as the clearest,mature and recognized means to surpass Moore's Law due to its advantages of short global interconnection,small delay,low power consumption,high broadband,high integration,etc.It is expected to achieve the"overtaking"of domestic advanced process IC manufacturing.The 2.5D and 3D integration of homogeneous or heterogeneous chips and passive devices through 2.5D TSV silicon interposer can greatly reduce the size and weight of products,increase the transmission rate and bandwidth,and meet the requirements of"smaller,stronger,and smarter"electronic systems.Therefore,it has become the key direction of research on IC packaging at home and abroad.However,due to the complex preparation process,high manufacturing cost and low product yield,a unified preparation process for the product has not yet been formed;moreover,for the manufacturing of high-density TSV interposer,the key process technology is more difficult,which seriously affects the integration process yield of microsystem products based on 2.5D TSV interposers.This paper takes the 2.5D TSV interposer for high performance processor products as the research object,and thoroughly investigates the design,packaging,and testing methods in the integration process.The electrical and thermal characteristics of high-performance processors based on 2.5D TSV interposer technology are theoretically studied and simulated,and compared and analyzed with actual test results.Then,we focus on the critical packaging process of 2.5D TSV interposer and proposea series of modification methods,and then carry out follow-up tests on the packaging reliability.Through a combination of theoretical analysis and process modification,the microfabrication process and test methods of 2.5D TSV interposer products are integrated,providing an important theoretical foundation and research method for the improvement of the yield of the back-end package process.The research in this paper plays a crucial role in further promoting the scale manufacturing and application of microsystem products based on 2.5D TSVinterposer.The main research contents and innovation points of this thesis are as follows:(1)The electrical and thermodynamic characteristics of 2.5D TSV interposer based on high-performance microsystem products are investigated by means of simulation analysis.The single-ended transmission line and differential transmission line characteristics of the2.5D TSV interposer are obtained,and the mechanism of the manufacturing process on the electrical characteristics of the product,such as process error,dielectric material characteristics,material roughness,etched shape,and test PAD thickness,is analyzed in conjunction with the actual production process.Through the design anlysis,the thickness of RDL was set to 5?m and the thickness o f th e PI was set to 8?m.Then,the power integrity of the 2.5D TSV interposer is simulated and analyzed,concentrating on the influence rule of DC voltage loss,which is optimized through simulation to ensure that the maximum current density is less than 800A/mm² and theminim vccint core voltage is0.9979V.(2)An experimental study of the 2.5D TSV interposermanufacturing process has been carried out,focusing on the principles of the key processes involved and innovative improvements to several processes.The specific modifications are as follows:In the wafer through-via etching process,a composite dielectric mask method of"organic adhesive+inorganic layer"is proposed for masking before wafer etching,which solves the problem of"drilling"in the etching process.In the wafer through-via insulation preparation process,a combined"thermal oxygen+plasma enhanced chemical vapor deposition(PECVD)"method of Si O₂ dielectric deposition is proposed,which solves the problem of low via wall step coverage in the conventional PECVD process and also enhance the denseness of the Si O₂layer structure;in the wafer through-via copper filling process development,by adding vacuum and dithering in the wafer plating pre-treatment,the solution exchange capability in the via is improved,and the problems of insufficient filling at the bottom and hollow in the middle are solved.(3)In the integration of 2.5D TSV interposer process,the difficult problems in the integration process were studied by adding process means.After the Cu chemical mechanical polishing(CMP)on the wafer surface,the annealing process is added to solve the problem of the polyimide(PI)adhesive being topped and cracked by the Cu pillar in the expanded via due to the subsequent high temperature process,with a curing annealing temperature of 300°C and a curing time of 30min.In response to the difficulty of debonding temporary bonded wafers after high temperature,acid,alkali vacuum and otherenvironment,an innovative wafer etching process is proposed,whereby the edge silicon etching is removed,thus circumventing the problem of difficult debonding of bonding adhesives in the edge area of bonded wafers due to denaturation and realising the debonding process of glass carriers and wafers.Finally,the small batch processing of TSV interposer with RDLwidth/line spacing of 10?m/10?m,TSV of 5?m and repection ratio of 10:1 is realized(4)The test method of 2.5D TSV interposer is investigated,including optical testing tenchnology and electrical tesing technology,and a special test area is reserved on the 2.5D TSV interposer wafer by referring to the method of PCM area in the front-end manufacturing process,and the performance of the 2.5D TSV interposer is characterized by testing the test area pattern.The test structure for characterizing 2.5D TSV interposer performance is systematically studied,and a standard test area pattern and test method are developed.The performance of 2.5D TSV interposer can be characterized relatively accurately by comparing the measured results.(5)For the assembly process of large size and thin 2.5D TSV interposer,the key processes such as flip-chip welding,bottom filling and laser balling on the back of interposer were studied.we propose a ball placement method based on a single 2.5D TSV interposer die using laser fused balls.Compared with the traditional printing method,it not only improves the accuracy of ball placement,but also saves the cost by eliminating the tooling such as printing leakage plate.Through the above research,a complete serialof high-density 2.5D TSV interposer design,manufacturing,packaging and testing methods for high-performance microsystem products was established in this research.The research has unlocked the vital technologies in the product implementation process and realized the large-scale integrated manufacturing of 2.5D TSV interposer,overcoming the major barriers to the integrated application of microsystems and providing novel technical support for the widespread application of high-density 2.5D TSV interposer in microsystems.