Investigation On Electrochemical Performance And Tuning Property Of The Organic-Additive-System For Copper Electrodeposition

Copper electrodeposition technology,as a basis technology of printed circuit board(PCB),package substrate and integrated circuit,is facing challenges than ever before.The two biggest problems in copper electrodeposition technology are: 1)how to maintain the reliability of the electrical interconnect structure with the increasing integration of PCB? 2)how to achieve high yield with the increasing production demand? The acid sulfate copper plating bath is the mainstream of copper electroplating technology nowadays,however,the quality of the copper coatings is not satisfactory without assistance of additives.Generally,a uniform coating is achieved through a synergistic effect of additives,nevertheless,the underlying mechanism of additives is still under debate because of the great varieties of additives and a lack of efficient methodology.Investigating the mechanism of additives and developing new additives are worldwide difficult nodes.Through hole(TH)is considered as one of the most important method to achieve electrical interconnect structure of PCB.The uniformity of TH is an important factor affecting the reliability of electronic products.This work aims to improve the uniformity of TH through developing different additive systems.Electrochemical,molecular dynamics(MD)and quantum chemistry methods are implemented for the purpose of investigating the mechanism of each additive system.The main contents are as follows:(1)Investigating of the synthesis and leveling properties of poly(1-vinyl imidazole co 1,4-butanediol diglycidyl ether,VIBDGE).VIBDGE was synthesized through a copolymerization of 1-vinyl imidazole and 1,4-butanediol diglycidyl ether,the chemical structure of VIBDGE was characterized by fourier transform infrared spectroscopy(FTIR)and gel permeation chromatography(GPC).The frontier orbitals of VIBDGE was calculated using density functional theory method which were used to predicate its leveling performance.The adsorption behavior of VIBDGE was simulated by MD method and a comparison of adsorption energy between VIBDGE and Janus green B(JGB)was carried out.Galvanostatic potential transient mesurments(GMs)and cyclic voltammetry(CV)tests were conducted to study the electrochemical behaviors of VIBDGE and the interaction among VIBDGE,Bis-(sodium sulfopropyl)-disulfide(SPS)and Polyethylene glycol(PEG).The results show VIBDGE has a strong polarization effect during copper electrodeposition and it has competitive adsorption both with SPS and PEG.Additionally,the competitive adsorption is a dynamically-controlled process.The leveling performance was characterized by panel electroplating.The throwing power(TP)of TH was increased from 46.38% to 90.00% with the addition of VIBDGE.(2)Investigation of the synthesis and leveling performance of nitrogen-containing heterocyclic levelers.In this chapter,the nitrogen-containing heterocyclic levelers were synthesized through a copolymerization of pyrimidine,pyridine,pyrazole,imidazole,and pyrrole with 1,4-butanediol diglycidyl ether,respectively.The chemical structures of the synthesized levelers were characterized by FT-IR and GPC.The adsorption behaviors and the quantum chemical parameters of the synthesized levelers were simulated and calculated.The frontier orbitals of the synthesized levelers predict pyrimidine and pyridine derived levelers have the highest chemical reactivity with copper,while pyrrole derived leveler owns the lowest chemical reactivity.Furthermore,pyrazole derived leveler possesses highest electrostatic potential which indicates it has potential to have an excellent leveling property at high current density.The leveling properties are characterized by GMs.As predicted before,pyrimidine and pyridine derived levelers have strongest polarization effect,however,pyrrole derived leveler has no polarization effect at all.By adjusting the concentration of the levelers,a positive potential difference between high and low convection intensity can be reached,therefore,the levelers are promising candidates to achieve a uniform coating of TH.The influence of levelers on TH's uniformity was characterized by panel electroplating,the result proved the addition of pyrimidine and pyridine derived levelers increased TP from 57.62% to 83.82% and 86.87% at 2 A/dm2,respectively.The increasing current density has little impact on the pyrazole derived leveler and the addition of pyrazole derived leveler increases TP from 38.00% to 72.37% at 3 A/dm2.(3)Development of a copper plating additive system for high rate copper electrodeposition.Traditional additive formulas are difficult to obtain a uniform and bright copper coating during high rate electrodeposition.Hydroquinone was found can improve the quality of copper coating during high rate electrodeposition.Various measurement methods were implemented to investigate the mechanism of hydroquinone during high rate copper electrodeposition.The result shows the addition of hydroquinone does not affect the electron transfer process and nucleation model during copper electrodeposition.Additionally,X-Ray diffraction(XRD),MD and Scanning electron microscope(SEM)results shows hydroquinone impacts on the nucleation growth through a selective modification process: hydroquinone selectively adsorbs on the(220)crystal planes and further inhibit its growth.This process leads to a shift of nucleus geometry,more specifically,from laminated structure to nanocubic particles.Additionally,hydroquinone,as a reductant,has function of stabilizing SPS during electroplating.Those two factors contribute to the good quality copper coating.Electroplating results show the addition of PEG-SPS-hydroquinone increases TP from 58.12% to 68.48% at 3.5 A/dm2 and the productivity increased by 75% at this current density compared with conventional plating conditions(2 A/dm2).(4)Development of an additive system for high aspect ratio TH plating.Fe3+/Fe2+ can effectively reduce copper thickness on the surface of TH and improve the uniformity of TH,however,Fe3+ will etch the deposited copper film which limits its application.To overcome this shortcoming,organic oxidation-reduction pairs were developed.The mechanism of organic oxidation-reduction pairs and its interactions with SPS,PEG and JGB were studied using anthraquinone-2-sulfonate as an example.The result shows anthraquinone-2-sulfonate occurs a reduction reaction in cathode and the reduction reaction will compete with the reduction reaction of the cupric ions.Additionally,the polarization effect induced by PEG and JGB and the depolarization effect caused by SPS were weakened because of the present of anthraquinone-2-sulfonate in plating bath.The influence of anthraquinone-2-sulfonate on the current efficiency and the morphology of copper coatings were studied.By adjusting the concentration of anthraquinone-2-sulfonate,the TP of TH with an aspect ratio of 10:1 increased from 62.61% to 82.76%.