Investigation of Nitrogen Heterocyclic Compounds as Levelers for Electroplating Cu Filling by Electrochemical Method and Quantum Chemical Calculation

Abstract

A series of nitrogen heterocyclic compounds (NHCs) bearing different functional groups were investigated as levelers for electroplating Cu microvia filling. The cathodic potential decreased with an injection of 4-amino-6-hydroxy-2-mercapto-pyrimidine (AHMP), 4-hydroxy-2-mercapto-6-methyl-pyrimidine (HMMP), 6-dimethyl-2-pyrimidinethiol (DPT), or 2-mercaptopyridine (2-MP), whlie the cathodic potential increased with an addition of 2-MPD. To evaluate filling performance of a plating solution on an addition of the leveler, the relationship between the super filling capability (SFC) of the plating solution and the Cu stripping quantity was proposed. The SFC was positively associated with the filling performance of the microvias, and the high SFC value was conducive to improve the filling performance of microvia and to reduce thickness of plated Cu film on the surface. Furthermore, the adsorption ability and active functional groups of NHCs were analyzed by quantum chemical calculations. Different from the conventional nitrogen active sites in quaternary ammoniums, the -SH and = S groups in the NHCs were the most active reaction sites for surface adsorption on Cu surface and the adsorption ability of NHCs was negative correlation with energy gap ( E). In addition, scanning electron microscope and X-ray diffraction results indicated that the uniformity and brightness of the electroplated Cu film were improved by an addition of AHMP, HMMP, DPT, and 2-MP due to a significant change of the Cu crystalline orientation in plating deposition.

4,6-Dimethyl-2-mercaptopyrimidine as a potential leveler for microvia filling with electroplating copper

“…1,2 In order to meet the demands of electronic products with multifunctions, high frequency, and high-speed performance, 3 the microvias should be entirely lled by electroplating copper without seams or voids; i.e., so-called "superlling" or "bottom-up lling". 4 However, according to reported literature, 5 superlling cannot be achieved due to uneven local current density contributions unless some particular additives are used which have signicant inuence on performance and orientation of the copper deposition. 6 To meet industrial requirements, several additives, such as an accelerator, a suppressor, and a leveler, must be simultaneously added to the electroplating copper solution.…”

“…10 This was demonstrated in a large number of studies which showed that interactions among the additives in this system played a very signicant role in the bottom-up lling. 5 Dow et al 11 reported that ABPV can spontaneously adjust interaction between the accelerator and the suppressor from a bad lling pattern to a perfect pattern at low chloride ion concentrations. Moffat et al 9 proposed that dodecyltrimethylammonium chloride (DTAC) can deactivate the adsorbed SPS accelerator due to ion-pair interaction between the cationic head group of the DTAC and the anionic tail group of the adsorbed SPS accelerator.…”

“…Another paper has reported DMP is an effective leveler, but it has no detailed research. 5 Therefore, the purpose of the present work is to study lling performance in detail and electrochemical behaviors of different formulas with or without DMP, plus surface morphology, crystalline structure, thermal shock, and thermal cycle tests aer copper plating. It has been proven that plating formulas containing DMP can completely meet requirements for PCB application reliability.…”

Advances in mechanistic understanding of additives for copper electroplating in high-end electronics manufacture

“…恰当的添加剂 配方可以改变电极表面的极化电位, 调控孔内外不 同区域铜沉积的速率, 从而实现无孔隙的超级填充 (Superfilling), 科学上将这一类的现象归纳为电镀 铜填盲孔的问题 [11] (图 2). [12][13][14][15][16][17][18] , 聚乙烯亚胺(PEI) 、聚乙烯吡咯烷酮(PVP)等含氮 聚合物 [19][20][21][22] 、以及十二烷基三甲基氯化铵(DTAC) 等季铵盐类表面活性剂 [23,24] , 能够起到抑制消除镀 层上方的凸起(Bump)的形成的作用. 针对不同的电 镀铜应用场景, 产业界需要优化出特定配方和施镀 条件, 而这绝非易事.…”

A novel viewpoint of an imidazole derivative ionic liquid as an additive for cobalt and nickel electrodeposition

“…54 Nitrogen atoms among the nitrogen heterocyclic compounds were preferred active sites for accepting electrons from Cu substrate. 55 The inhibitory effect of the Im-IL molecule can also be attributed to the specic adsorption of iodide ions on the cathode surface, as reported in ref. 40.…”