Introduction of Development and Application Technology of Organic Additives for Acid Copper Electroplating

Abstract

Acid copper electroplating is one of the key technologies in buildup multilayer PCB (BUM-PCB) manufacture process and the most important technique to achieve electrical interconnection between any layer and high-density interconnection in a substrate. This article introduces the research focus of organic additives used in acid copper electroplating, and developing different kinds of micro-via filling copper electroplating technique applied in various scenarios, and some other technical problems from applications. First of all, according to the chronopotentiometric (CP) experiment results, the levelers with different polymeric molecular structures exhibited various responses of cupric deposition potential along with their increased concentrations, which is the critical information for studying the absorption and desorption behaviors of organic additives, and provides reasonable advices for additives formula design. Linear sweeping voltammetric (LSV) study is very helpful for studying the absorption behavior of organic additives under different potentials and quantitatively describing the degree of current change because of potential polarization that helps evaluate the stability of micro-via filling performance of particular additive formular. Secondly, with the use of gel permeation chromatography (GPC) we have widely studied polymer molecular structure in the aspect of molecular weight and polydispersity, which includes carrier and leveler. The precise information of polymeric molecular structure obtained from experiments can greatly enhance comprehension of the absorption mechanism of polymer additives. Corresponding electrochemical experiment results show that there is obvious correlation between molecular weight of carrier and its suppression effect. Examples of polymerization reaction of some levelers with novel molecular structure are presented, which aims at studying the influence of steric hindrance on electrochemical or electroplating performance by adjusting the length of carbon chain between two aminos and the number of heteroatom, like oxygen atom. Thirdly, different kinds of micro-via filling copper electroplating technique applied in various scenarios have been developed, which includes high-speed micro-via filling copper electroplating technique, ultrathin thickness controlled micro-via filling copper electroplating technique, highly uniform pattern line and micro-via filling copper electroplating technique, through hole and micro-via filling copper electroplating technique and through hole filling copper electroplating technique. Finally, technical problems from application of additives are simply introduced here. Copper plating equipment is the workplace for plating solution and its structure design and process parameters will profoundly affect the micro-via filling performance in the aspect of flow field and electric field. Large void is very easy to be formed inside micro-via under improper convection and deposition velocity. Virgin make-up solution (VMS) components also affect micro-via filling performance obviously in coordination with organic additives by changing overpotential of cupric reduction reaction. Precise determination of organic additives in aged plating solution is very challengeable because byproducts accumulated during manufacture have completely different absorption mechanisms compared to fresh plating solution.

Keywords

build up multilayer printed circuit board / acid copper electroplating / via filling / leveler / competitive adsorption / electrochemistry

References

[1] Xiang J, Wang C, Chen Y M, Wang S X, Hong Y, Zhang H W, Gong L J, He W. Improving wettability of photo-re-sistive film surface with plasma surface modification for coplanar copper pillar plating of IC substrates[J]. Appl. Surf. Sci., 2017, 411: 82-90.

[2] Chen Y M, He W, Chen X M, Wang C, Tao Z H, Wang S X, Zhou G Y, Moshrefi-Torbati M. Plating uniformity of bottom-up copper pillars and patterns for IC substrates with additive-assisted electrodeposition[J]. Electrochim. Acta, 2014, 120: 293-301.

[3] Moffat T P, Josell D. Electrochemical processing of inter-connects[J]. J. Electrochem. Soc., 2013, 160(12): Y7-Y10.

[4] Dou W P, Yen M Y, Liao S Z, Chiu Y D, Huang H C. Fill-ing mechanism in microvia metallization by copper elec-troplating[J]. Electrochim. Acta, 2008, 53: 8228-8237.

[5] Moffat T P, Wheeler D, Kim S K, Josell D. Curvature en-hanced adsorbate coverage model for electrodeposition[J]. J. Electrochem. Soc., 2006, 153(2): C127-C132.

[6] Yang S D, Thacker Z, Allison E, Bennett M, Cole N, Pin-hero P J. Electrodeposition of copper for three-dimensional metamaterial fabrication[J]. ACS Appl. Mater. Interfaces, 2017, 9(46): 40921-40929.

[7] Mendez J, Akolkar R, Landau U. Polyether suppressors enabling copper metallization of high aspect ratio intercon-nects[J]. J. Electrochem. Soc., 2009, 156(11): D474-D479.

[8] Yang H, Krause R, Scheunert C, Liske R, Uhlig B, Preusse A, Dianat A, Bobeth M, Cuniberti G. Copper electroplat-ing with polyethylene glycol: Part II. experimental analysis and determination of model parameters[J]. J. Electrochem. Soc., 2018, 165(2): D13-D22.

[9] Gallaway J W, West A C. PEG, PPG, and their triblock copolymers as suppressors in copper electroplating[J]. J. Electrochem. Soc., 2008, 155(10): D632-D639.

[10] Lee M H, Lee Y, Oh J H, Kim Y G, Cho S K, Kim J J. Microvia filling with copper electroplated with quaternary ammonium-based leveler: the evaluation of convection-dependent adsorption behavior of the leveler[J]. J. Ele-ctrochem. Soc., 2017, 164(14): D1051-D1055.

[11] Zheng L, He W, Zhu K, Wang C, Wang S X, Hong Y, Chen Y M, Zhou G Y, Miao H, Zhou J Q, Investigation of poly (1-vinyl imidazole co 1, 4-butanediol diglycidyl ether) as a leveler for copper electroplating of through-hole[J]. Electrochim. Acta, 2018, 283: 560-567.

[12] Braun T M, John J, Jayaraju N, Josell D, Moffat T P. Simu-lating the influence of supporting electrolyte concentra-tion on copper electrodeposition in microvias[J]. J. Elec-trochem. Soc., 2022, 169(1): 012502.

[13] Huang S M, Liu C W, Dou W P, Effect of convection-de-pendent adsorption of additives on microvia filling in an acidic copper plating solution[J]. J. Electrochem. Soc., 2012, 159(3): D135-D141.

[14] Walker M L, Richter L J, Moffat T P. Potential dependence of competitive adsorption of PEG, Cl-, and SPS/MPS on Cu[J]. J. Electrochem. Soc., 2007, 154(5): D277-D282.

[15] Cao H Y, Hang T, Ling H Q, Gao L M, Li M. Linear sweep voltammetric study on the copper electrodeposition of though-silicon-vias[J]. J. Electrochem. Soc., 2014, 161(6): D349-D352.

[16] Xiao N, Pang K N, Wang Z W, Li D Y, Li N. Structural effect of polymers on their microvia filling performance as suppressors during the copper electroplating[J]. Int. J. Electrochem. Sci., 2017, 12: 1453-1462.

[17] Chen T C, Tsai Y L, Hsu C F, Dow W P, Hashimoto Y. Effects of brighteners in a copper plating bath on throw-ing power and thermal reliability of plated through holes[J]. Electrochim. Acta, 2016. 212: 572-582.

[18] Feng K S, DeCesare B, Yu M, DeSalvo D, Watkowski J. Electroplated copper filling of through holes on vary-ing substrate thickness[J]. IEEE, 2014, Catalog Number: CFP1459B-ART.

[19] Lefebvre M, Barstad L, Gomez L. Copper electroplating for HDI and IC substrate through hole fill[C]. IEEE, 2010:1-4.

[20] de Maubeuge H L. Influence of geometric variables on the current distribution uniformity at the edge of parallel plate electrodes[J]. Electrochim. Acta, 2011, 56 (28): 10603-10611.

[21] Liske R, Wehner S, Preusse A, Kuecher P, Bartha J W, Influence of additive coadsorption on copper superfill behavior[J]. J. Electrochem. Soc., 2009, 156(12): H955-H960.

[22] Dou W P, Huang H S, Yen M Y, Chen H H. Roles of chloride ion in microvia filling by copper electrodeposi-tion[J]. J. Electrochem. Soc., 2005, 152(2): C77-C88.

[23] Nagy Z, Blaudeau J P, Hung N C, Curtiss L A, Zurawski D J. Chloride ion catalysis of the copper deposition reac-tion[J]. J. Electrochem. Soc., 1995, 142(6): L84-L89.

[24] Garcia-Cardona E, Wong E H, Barkey D P. NMR spectral studies of interactions between the accelerants SPS and MPS and copper chlorides[J]. J. Electrochem. Soc., 2011, 158(3): D143-D148.

[25] Hayashi T, Matsuura S, Kondo K, Kataoka K, Nishimura K, Yokoi M, Saito T, Okamoto N. Role of cuprous ion in copper electrodeposition acceleration[J]. J. Electrochem. Soc., 2015, 162(6): D199-D203.

[26] Choe S, Kim M J, Kim H C, Cho S K, Ahn S H, Kim S K, Kim J J. Degradation of bis(3-sulfopropyl) disulfide and its influence on copper electrodeposition for feature filling[J]. J. Electrochem. Soc., 2013, 160(12): D3179-D3185.

[27] Frank A, Bard A J. The decomposition of the sulfonate additive sulfopropyl sulfonate in acid copper electroplating chemistries[J]. J. Electrochem. Soc., 2003, 150(4): C244-C250.

[28] Park D J, Han M, Park M J, Lee J Y, Choe S. Brightener breakdown at the insoluble anode by active chlorine species during Cu electrodeposition[J]. J. Ind. Eng. Chem., 2022, 106: 198-204.

[29] West M J, Wang Q, Bailey T H. Advanced metrology and control of copper electrochemical deposition I: The decomposition chemistry of the accelerator SPS[J]. ECS Transactions, 2007, 2(6): 131-148.

[30] Gabrielli C, Mocoteguy P, Perrot H, Zdunek A, Nieto-Sanz D. Influence of the anode on the degradation of the additives in the damascene process for copper deposition[J]. J. Electrochem. Soc., 2007, 154(3): D163-D169.

[31] Moçotéguy P, Gabrielli C, Perrot H, Zdunek A, Sanz D N. Influence of the anode and the accelerator on copper bath aging in the damascene process[J]. J. Electrochem. Soc., 2006, 153(12): G1086-G1098.