The effects of ultrasonic agitation on supercritical CO2 copper electroplating

Abstract

Applying ultrasound to the electroplating process can improve mechanical properties and surface roughness of the coating. Supercritical electroplating process can refine grain to improve the surface roughness and hardness. However, so far there is no research combining the above two processes to explore its effect on the coating. This study aims to use ultrasound (42kHz) in supercritical CO (SC-CO) electroplating process to investigate the effect of ultrasonic powers and supercritical pressures on the properties of copper films. From the results it was clear that higher ultrasonic irradiation resulted in higher current efficiency, grain refinement, higher hardness, better surface roughness and higher internal stress. SEM was also presented to verify the correctness of the measured data. The optimal parameters were set to obtain the deposit at pressure of 2000psi and ultrasonic irradiation of 0.157W/cm. Compared with SC-CO electroplating process, the current efficiency can be increased from 77.57% to 93.4%, the grain size decreases from 24.34nm to 22.45nm, the hardness increases from 92.87Hv to 174.18Hv, and the surface roughness decreases from 0.83μm to 0.28μm. Therefore, this study has successfully integrated advantages of ultrasound and SC-CO electroplating, and proved that applied ultrasound to SC-CO electroplating process can significantly improve the mechanical properties of the coating.

Influence of ultrasonic combined supercritical-CO2 electrodeposition process on copper film fabrication: Electrochemical evaluation

“…Notably, the observed diffraction pattern in US-SC-CO 2 -15 W cm −2 displays the most significant full width at half maximum (FWHM), which indicated that ultrasonic agitation would lead to the smallest grain size [16] , [23] , [24] . Similar to the previous reports, the grain sizes are calculated from the Scherrer equation [38] , [39] , [40] , [41] , [42] . The calculated average grain size values are presented in Fig.…”

“…The observed result confirms that ultrasonic power utilization enhances the electrocatalytic activity due to reducing the diffusion layer’s thickness and raising mass-transport of electroactive substances to the electrode surface. The combination of ultrasonic agitation with SC-CO 2 further accelerates the metal ions in the electrolyte through the soft cavitation behavior, resulting in a homogenous distribution of ions and increased active site species on the grain boundary [38] , [39] . In contrast, a further increase in the ultrasonic power (30 W cm −2 ) reduces the Cu film’s electrocatalytic performance.…”

“…They also influence surface morphologies, grain refinement, lower surface roughness, higher coating hardness, etc. The synergetic effect from ultrasonic agitation aided the supercritical carbon-dioxide (US-SC-CO 2 ) process succeeding a more effectual emulsification effect and an attenuated cavitation behavior called “soft cavitation” [34] , [35] , [36] , [37] , [38] , [39] , [40] . Thus, in the present work, we have performed a detailed study of two different ultrasonic powers’ (15 and 30 W cm −2 ) under the SC-CO 2 condition and the influence on the Cu film’s electrodeposition process.…”

Thermal treatment of (TiZr)N coatings on CO2‐controlled atmosphere

“…This increase could be due to that the particles coming from the CO 2 arrive on the surface, and it is acting as a coalescence point for larger grain growth (grain refinement effect). 43 At sample S4, a changed abrupt is presented; the roughness increases approximately 15.7 times concerning the S1 and S2 samples. These could be because the CO 2 gases produce microbubbles on the surface.…”

“…Meanwhile that in the S3 sample, the roughness increases two times (3.14 nm) concerning the S1 and S2 samples. This increase could be due to that the particles coming from the CO 2 arrive on the surface, and it is acting as a coalescence point for larger grain growth (grain refinement effect) 43 . At sample S4, a changed abrupt is presented; the roughness increases approximately 15.7 times concerning the S1 and S2 samples.…”