Additives are essential for damascene copper electroplating to achieve defect-free deposition in nanoscale interconnect on chips. A hybrid additive named 1000EQ with capabilities of both suppressor and leveler has been synthesized and analyzed. The additive contains polyether segment and nitrogen cation which are typical functional groups of suppressor and leveler, respectively. Electrochemical measurements reveal that 1000EQ has strong inhibition toward copper deposition and is more resistant to the desorption of accelerator than traditional suppressor polyethylene glycol (PEG, Mw = 10,000). 1000EQ and bis-(sodium sulfopropyl)-disulfide (SPS) were used as additives to achieve a defect-free filling of features with 70 nm in width and an aspect ratio above 3. The ratio of copper film thickness over dense and sparse patterned area is close to 1 and the root mean square roughness (Rq) of the film is 9.4 nm, acting as a solid proof of its hybrid characteristic. The resistivity of the copper film is 1.80 ± 0.02 µΩ cm. The characterizations establish that 1000EQ is a promising candidate which can serve as both suppressor and leveler for damascene copper electrodeposition and is able to simplify the bath used in copper electrodeposition process.
Developing a highly efficient leveler in acid copper electroplating solution is one of the primary tasks necessary for achieving superconformal filling of microvias and interconnections in printed circuit boards (PCBs). Two triethylenediamine-based Gemini levelers, both with terminal quaternary ammonium groups, are synthesized and named as GL1(C8) after reaction of triethylenediamine with 1,8-dichlorooctane and GL2(C6 with two C–O linkages) after triethylenediamine with 1,2-bis(2-chloroethoxy) ethane. Electrochemical experiments indicate that at 100 rpm and 1000 rpm GL2combines with a suppressor and accelerator to exhibit greater potential difference of 23 mV than GL1in 9 mV for Cu2+reduction, demonstrating that GL2has a stronger synergistic convection-dependent adsorption (CDA) effect. Microvias copper electroplating experiments confirm that acid copper electroplating solution containing GL2achieve more effective superconformal void-free filling as it results in FP = 96.1%, while the solution containing GL1results in FP = 70%. Theoretical calculations indicate that adsorption energy of GL2is −1037.54 kJ·mol−1, which is lower than GL1(−1019.06 kJ·mol−1). GL2displays lower electron density compared to GL1, which facilitates its displacement by accelerator at the bottom. The lower adsorption energy of GL2suggests the weaker adsorption ability and the stronger CDA behavior.
Jiawei Zhang,Xin Chen,Chenhao Qian,Binbin Fan,Limin Wang
The design and synthesis of high-performance levelers remain a major challenge to date. Herein, a series of phenothiazine (PTZ) derivatives were designed and synthesized, and they had a butterfly conformation, and their adsorption capacities were easier to modulate. To check out the inhibition capabilities among these eight PTZ derivatives, electrochemical measurements and theoretical calculations were carried out, and PTZ-8 indicated the strongest inhibition capabilities among these PTZ derivatives. Besides, galvanostatic measurements were also carried out to evaluate the overall performance of the levelers. The results showed that PTZ-8 had a potential oscillation, but PTZ-6 had strong convection-dependent adsorption. Due to the potential oscillation of PTZ-8, PTZ-6 as the representative leveler was selected for through-hole electrodeposition. In addition, field-emission scanning electron microscope images and X-ray diffraction results displayed the surface morphology, which indicated that the addition of PTZ-6 could lead to a fine copper deposit and cause the preferential orientations of copper deposits to change from [220] to [111]. This study might lay the foundation for the design of high-performance levelers.
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