Mechanism And Application Of Copper Eletrodeposition For The Interconnection Structures In Package Substrate

The IC package substrate is a bridge between chip and external electrical interconnections including electronic circuits,electronic components and others,whose performance directly determines the realization of integrated circuit performance.The electrodeposited copper technology is brought to product interconnection metal structures of the package substrate.With a widespread attention,electrodeposited copper technology has an important part of the electronic circuit addition method.Currently,the relationship between the electrodeposited copper environment and the high-quality requirements is hotspot and difficulty in the world.Basing on the sputtering seed layer,the plating interconnection structure is one of the core technologies of coreless package substrates in the fabrication.The key is the growth rate and quality control of the copper electrodeposition.The electrodeposited copper of interconnected structure is a multiphysics coupling process including the electric field and the flow field.In this paper,numerical simulation,electrochemical test and other methods are used to explore the mechanism of electrodepositing copper and discuss the multi-physics effects of electrodeposited copper on micro-holes and microcircuits for package substrates.The research is focusing on the reaction mechanism of accelerators,the action mechanism of levelers and the electrodeposition uniformity of interconnect structures including lines,holes and copper pillars to obtain the relationship between the rate and quality of copper deposition and the additives,current density of the plating solution,and propose the relevant theoretical models.The results are applied in cooperative enterprises and obtain the better economic and social benefits.The main research is as follows:?1?Research on the mechanism and application of electrochemical copper deposition in the interconnect circuit of package substrate.With different pattern designs,current distribution and copper thickness distribution of the pattern plating are analyzed by numerical simulation technology in the aspect of the electrochemical copper deposition to propose an optimization scheme for the improvement of the thickness uniformity of the deposited copper layer with different exposed copper areas.The distribution trends of copper layer thickness between simulation results and actual factory production are compared to investigate the effect of the baffles and auxiliary cathode strips on copper electrodeposition.It is demonstrated that the baffles and auxiliary cathode strips have a great influence on the uniformity of pattern electrodeposition.Different pattern designs need different baffles and auxiliary cathode.In addition,the numerical simulation is higher accuracy and efficiency for predicting pattern electrodeposition.It solves the problem of uniformity electrodeposition of ultra-fine line with line width/line spacing of15?m/15?m in industrial production,and the yield of intermediate production is increased by 7.91%for this process.?2?Study on the action mechanism of accelerator during electrodeposition process for package substrate.Using cuprous oxide,sodium polysulfodipropyl-dissulfide?SPS?and 3-Mercapto-1-propanesulfonic acid sodium salt?MPS?as raw materials,the accelerators A and B are generated by mixing reaction.The characterization and simulation techniques are brought into verify that A and B are the same compound,whose molecular formula is MPS-2Cu?I?.Moreover,it is proved that SPS interacts with Cu?I?,and the S-S bond of SPS is broken to form MPS-2Cu?I?.The electrochemical tests,such as galvanostatic method?GM?and cyclic voltammetry?CV?,are used to discuss the influence of Cu?I?on the performance of electrodeposited copper for three electroplating systems,containing SPS,MPS and N-N-dimethylaminodithiocarbamoyl-1-propanesulphonic acid?DPS?to obtain the variation trends and special mechanisms of self-made accelerators.The experimental results show that Cu?I?has a great influence on the electrochemical performance for the plating solutions with SPS or MPS,and the surface morphology and copper grain orientation of the electroplated copper layer.For plating solution with DPS,the performance and surface morphology of the electroplated copper layer have no significant effect,but have a certain degree of influence on the orientation of the copper grains.?3?Study on the action mechanism and application of levelers in electrochemical copper deposition of package substrate.The relationship between the absolute potential difference????,the relative potential difference???_r?and the slope of the Tafer curve for electroplating solution are obtained by the GM and chronoamperometry test under different rotational speeds.Based on the relationship,the numerical simulation model of through-hole?TH?electroplating is established.The relationship between the potential differences of leveler and the throwing power?TP?of TH electroplating and the weights of the influence of potential differences on the TP of electrodeposited TH are analyzed by multiphysics coupling Technology.The correctness and reliability of multi-physics coupling results are verified by actual electrodeposited TH experiments.The results show that the TP value of the TH electroplating increases first and then becomes unchanged because of the negative shift of the potential differences.?4?Research on the mechanism and application of electrochemical copper deposition in the TH of package substrate.GM test and polarization curve test applied for investigating the variation of??and??_r.The electrochemicall tests combine with numerical simulation technology to observe the effects of the aspect ratios of the through-hole of the package substrate on the exchange of the plating solution and the distribution of the power line.Moreover,the relationship between the performance of the plating solution and plating TH with different aspect ratios is discussed.Finally,the theoretical model of the relationship between the TP value and the performance of the electroplating l solution is established.It is demonstrated that the plating solution with the more negative potential is suitable for the electrodeposited copper with the larger aspect ratio.?5?Study on the mechanism and application of electrodeposition copper pillar in package substrate.According to the process characteristics of coreless technology,the dry film surface is rebuilt by O₂-CF₄ plasma and atmospheric plasma.Attenuated total reflectance fourier transform infrared spectroscopy?ATR-FTIR?,X-ray photoelectron spectroscopy?XPS?,and X-ray energy spectrum analysis?EDS?are used to characterize the surface morphology,wettability,roughness,element composition and molecular structure of the dry film.The experimental results indicated that the surface of the dry film modified by atmospheric plasma treatment has the better surface wettability and better uniformity of electroplated copper pillar.It solves the problem of uniformity electrodeposition of copper pillar with diameter of 60?m and high of 45?m,and the yield of intermediate production is increased by 5.64%for this process.It got a satisfactory economic benefits.