The first stage is the filling of the bottom half of the vias, which proceeds by the U-shape model the top half of the vias are filled in the second stage, following the bottom-up model. Therefore, with the single inhibitor SH110, the TSVs were filled according to different models at different stages in the filling process. To understand how SH110 affects the TSV filling mechanism, molecular dynamics (MD) simulations and quantum chemical calculations were used to analyse the configuration and electronic structure of SH110 and its interactions with the copper surface, in comparison with a common accelerator, SPS. Linear sweep voltammetry (LSV) was performed to determine the electrochemical properties of additives in the deposition process for TSV filling. In this study, a single inhibitor, 3-(2-(4,5-dihydrothiazol-2-yl)disulfanyl)propane-1-sulfonic acid (SH110), was found to possess the ability to fill the TSV without introducing voids. Thus far, only one report, by Tang and co-workers, has demonstrated a single-component additive (Janus Green B) that could provide void-free filled-in micro-vias 11.
Therefore, a single inhibitor that accomplishes void-free TSV filling is needed in order to reduce the time and cost of the optimisation process. However, it takes numerous experiments to optimise the concentrations of each component in this complex additive system. These additives accelerate the via bottom deposition rate and suppress the via mouth deposition rate, to obtain bottom-up filling. Polyethylene glycol (PEG), polypropylene glycol (PPG), and co-polymers thereof are commonly used as suppressor additives 9, 10. The typical leveller employed is an organic monomer containing positively charged nitrogen, such as pyridinium, imidazolium, or ammonium 7, 8. At present, the most commonly used accelerator is sodium 3,3′-dithiodipropane sulfonate (SPS) 6, where the sulfur S–S bonds and sulfonic acid or sulfonate groups (SO 3H or SO 3 –) are thought to be the key structures responsible for acceleration effects. To accomplish void-free TSV filling, an accelerator, suppressor, and leveller are commonly added to the plating solution. However, voids often occur upon filling, which must be overcome for reliable TSV fabrication 4, 5. TSV copper filling is one of the key techniques used for TSV fabrication, as it costs ~ 40% less than conventional integration technologies. Three-dimensional (3D) integration with through-silicon vias (TSVs) is a promising technology for use in electronic systems, as TSVs can provide extremely short vertical interconnections that can improve performance, increase operating speed, and reduce the volume of devices when compared with conventional integration technologies 1, 2, 3. SH110 is an excellent additive exhibiting both the acceleration and the suppression necessary for achieving void-free TSV filling. Quantum chemistry calculations showed that DHT provides an inhibitory effect for TSV filling, while MPS acts as an accelerator for SH110. MD simulations indicated that the adsorption of the coplanar MPS moiety is the main factor governing acceleration. SH110 adsorbs to the Cu surface by both 4,5-dihydrothiazole (DHT) and 3-mercaptopropane sulfonate (MPS) moieties, while SPS is adsorbed only by MPS moieties. The interactions between the Cu surface and additives were simulated by molecular dynamics (MD) analysis using Materials Studio software, and quantum chemistry calculations were conducted using GAUSSIAN 09W. To understand how the additives affect the filling mechanism, linear sweep voltammetry of the plating solutions was carried out. SH110 resulted in void-free filling, whereas large keyhole voids were found for SPS. Sodium 3,3′-dithiodipropane sulfonate (SPS) and SH110 were used as additives for TSV electroplating copper filling. To avoid this, a single-component additive was developed: 3-(2-(4,5-dihydrothiazol-2-yl) disulfanyl) propane-1-sulfonic acid/sulfonate (SH110). However, optimising the additive concentrations is an expensive process.
Three-component additives are commonly used for void-free TSV filling. Three-dimensional integration with through-silicon vias (TSVs) is a promising microelectronic interconnection technology.
0 kommentar(er)
