Effect of Stirring on the Defect-Free Filling of Deep Through-Silicon Vias

Feng Wang,Jinzhi Liu,Ximei Liu

doi:10.1109/access.2020.2990918

Feng Wang, Jinzhi Liu + Show 1 more

Open Access

https://doi.org/10.1109/access.2020.2990918

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Abstract

Through-silicon-via (TSV) is an advanced 3D electronic integration technology. In order to achieve the defect-free filling of deep TSV, forced convection is commonly applied during TSV filling process. In this study, the interaction effect of forced convection and current density on deep TSV filling process is systemically investigated. The filling morphology of TSV electrodeposited with different stirring rate and different current density were observed by the scanning electron microscope (SEM). The phenomenon that forced convection reduces the TSV filling ratio at low current density but promotes the TSV filling ratio at high current density was discovered. Additionally, the influence of stirring rate on the TSV filling results was researched. In order to study the mechanism of forced convection at different current densities, electrochemical analysis and particle size measurement were carried out. The volt-ampere characteristic curves of the plating solution stirred at different speeds were analyzed. Furthermore, the effects of forced convection and current density on the crystal size of deposited copper were studied separately. Based on the experimental results, the mass transfer of additives and crystal nucleation of deposited copper were discussed to explain the interaction effect of forced convection and current density on deep TSV filling process.

Highlights

With the increasing demand for electronic devices with small size, light weight, superior performance and multifunctionality, the three-dimensional integrated circuit (3D IC), regarded as the promising candidate to overcome the limitations of Moore’s law, has received wide attention [1], [2]
By observing the TSV filling morphology, it could be found that forced convection promoted defect-free filling at high current density
Electrochemical analysis and particle size measurement were carried out to investigate the mechanism of these phenomena

Summary

INTRODUCTION

With the increasing demand for electronic devices with small size, light weight, superior performance and multifunctionality, the three-dimensional integrated circuit (3D IC), regarded as the promising candidate to overcome the limitations of Moore’s law, has received wide attention [1], [2]. Due to its high electrical conductance and low process costs, Cu has been the most commonly used metal for TSV filling [6] It is a great challenge in Cu electroplating to provide a void-free filling for deep TSV [7]. To promote the mass transfer of additives, pause pulse current and forced convection are often applied [15]–[21]. Pause pulse current provides time for additives diffusion, but reduces the filling efficiency. Few researches have been carried out on the interaction between forced convection and current density during deep TSV defect-free filling. We intended to systemically investigate the interaction effect of forced convection and current density on deep TSV filling process. The study result was expected to provide theoretical guidance for the process optimization of deep TSV defect-free filling

EXPERIMENTAL DETAILS

EFFECT OF FORCED CONVECTION AND CURRENT DENSITY ON THE TSV FILLING RESULTS

CONCLUSION