Copper Pumping Research Articles

Electrochemical Behavior of 2M5S and Its Influence on Reduction of Cu Pumping and Keep-Out Zone

Previously, we have reported the low thermal expansion copper electrodeposited in solution containing 2-Mercapto-5-benzimidazolesulfonic acid sodium salt dihydrate (2M5S). In this research, we investigated the electrochemical behavior 2M5S additive by CVS and LSV measurements. The 2M5S additive showed an inhibition effect during electrodeposition of copper, both in the absence and presence of Cl−. Using a combination of the 2M5S leveler with another SDDACC leveler and SPS accelerator, the thermal expansion of copper was reduced and the TSV was filled without defects. The SEM results showed that the copper pumping height of low TEC copper in PECVD SiO2 TSV was only 0.5 μm. Meanwhile, the copper pumping height of reference conventional copper in PECVD SiO2 TSV was about 2 μm. Furthermore, compared with thermal stress curve in Si around the conventional copper TSV, thermal stress curve in Si around the low TEC copper TSV was much lower and the KOZ also was reduced to about 1 μm.

Heating Rate Dependence of the Mechanisms of Copper Pumping in Through-Silicon Vias

In three-dimensional stacked-die packages, through-silicon vias (TSVs) are used to connect multiple adjacent dies through solder micro-bumps. During thermal cycling, the thermal expansion mismatch between the copper TSVs and the silicon dies creates large internal stresses in the hetero-structure, resulting in intrusion or protrusion of the TSV relative to the Si die. This phenomenon is commonly known as copper pumping and is a potential reliability concern as it impacts the stability of back-end-of-line structures. In this study, the copper-pumping phenomenon was investigated by thermally loading TSV structures via ex situ and in situ thermal cycling with various heating rates. The resulting TSV protrusion was characterized and it was revealed that copper pumping manifests itself via three distinct mechanisms: plasticity, grain boundary sliding, and interfacial sliding. Electron backscatter diffraction analysis revealed that grain boundary sliding occurs preferentially at incoherent sigma-3 boundaries, while coherent sigma-3 boundaries remain immobile. The operating conditions, including ambient temperature, heating rate and the microstructural features that influence these phenomena are discussed.

Influence of Copper Pumping on Integrity and Stress of Through-Silicon Vias

The influence of copper pumping on through-silicon vias (TSVs) under thermal loading was investigated using an in situ experimental technique. The morphology of the TSV and its evolution with temperature were observed by scanning electric microscopy, and the process of copper pumping and its damage to the integrity of the TSV were recorded. Some new failure modes were found. The maximum height of pumped copper was as high as $5~\mu \text{m}$ for a single thermal cycle and 25 $\mu \text{m}$ for multiple cycles. The thermal stress of the TSV and its evolution with temperature were then evaluated using a microinfrared photoelastic system. Full-field and real-time measurements were carried out. It was found that copper pumping at high temperature served to release stress and that this stress-free state of the TSV could be maintained. After cooling or annealing, however, the TSV stress again increased.

Experimental Stress Characterization and Numerical Simulation for Copper Pumping Analysis of Through-Silicon Vias

In this paper, a 3-D thermomechanical model of through-silicon vias (TSVs) has been analyzed and verified with in situ microscale strain measurements by synchrotron X-ray microdiffraction. Thereafter, a comprehensive stress/strain analysis on copper pumping and back-end-of-line (BEOL) cracking issues has been carried out. In addition, a design-of-experiments-based approach has been used to understand the effect of various parameters on copper pumping and BEOL stress. The results show that the smaller TSV diameter and thinner silicon die help reduce the copper pumping and thus mitigate BEOL stress.

Process Development and Optimization for 3 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> High Aspect Ratio Via-Middle Through-Silicon Vias at Wafer Level

This paper presents challenges encountered in the fabrication of high aspect ratio (AR) via middle, through-silicon vias (TSVs), of 3 ${\mu }\text{m}$ top entrant critical dimension and 50 ${\mu }\text{m}$ depth. Higher AR TSV integration is explored due to the lower stress and copper pumping influence of TSVs observed in adjacent CMOS devices. The key process improvements demonstrated in this paper include 3 ${\mu }\text{m}$ TSV etch, dielectric liner coverage, metal barrier and seed layer coverage, and copper electroplating.

Influence of Annealing Condition on TSV Pumping and Microstructure Evolution

Stacking of ICs using three-dimensional (3D) integration technology helps in significantly reducing wiring lengths, interconnection latency, and power dissipation while enhancing performance. Through silicon vias (TSVs) are regarded as a key enabling technology for 3D IC integration which assists in the realization of highly miniaturized and complex next-generation systems. Due to the thermal expansion (CTE) mismatch between copper and silicon, the copper in silicon vias tends to pump up as a result of thermal-mechanical stress during the post fabrication processes and/or during the lifetime of chip usage. One way to minimize or get rid of copper pumping is through heat treatment, for instance annealing or aging. The TSV wafers could be annealed right after copper plating process, or after chemical mechanical polish (CMP) process, or both. The residual stress might be thoroughly released by repeating annealing and CMP processes several times, however, the cost for fabricating the TSVs is increasing drastically, which is mainly attributed to the use of expensive CMP. To lower down the cost and minimize the CMP steps is one of the concerns from industry. In this paper, we report the thermal mechanical assessment of Cu pumping treated at different annealing conditions. moreover, the impact of different integration approaches on the TSV pumping behavior is also investigated. The finite element analysis method, ANSYS, is used to model and simulate the copper pumping at different temperatures, as shown in Fig.1. The pumping is measured by optical profiler, BRUKER ContourGT-X3, as shown in Fig.2. It has been found out that the copper grain size increases with annealing temperature, which is potentially contributed to larger protrusion. The preliminary results show that the annealing after copper plating process affects the microstructure evolution and pumping of TSVs. Figure 1

Filling and Planarizing Deep Trenches with Polymeric Material for Through-Silicon Via Technology

A key driver for 3-D device integration has been through-silicon via (TSV) technology that enables through-chip communication between vertically integrated layers. The TSVs typically have an electrical isolation using a dielectric layer between the silicon and the interconnect metal (e.g., copper). Recently, polymers have been proposed for use as the dielectric isolation layer, and polymers have been shown to increase device reliability by reducing “copper pumping,' where copper pops out from the TSV holes during thermal cycling. Traditionally, spinor spray-coating techniques have been used to fill TSVs with polymer material. However, using those techniques to fill and planarize very deep trenches (∼ 400 μm) and high-aspect-ratio structures has many limitations and usually results in voids, nonplanar surfaces, and lack of polymer flow to the requisite depths. Here, we present a novel process and a tool to completely fill and planarize deep trenches with a polymeric material. We use a combination of a traditional spin-coating process together with a physical planarization and fill process using the contact planarization tool to evacuate the trenches or vias on the wafer and then force the polymeric material inside the features. Using this process, we successfully filled and planarized trenches and vias 180 μm deep with 50-μm wide patterns as well as 400-μm deep trenches with ∼ 400-μm wide patterns. Initial results show complete filling and planarization of the material in the trenches without any voids.

2P-080 銅イオン輸送性P-type ATPaseの機能解析と低分解能溶液構造(膜蛋白質,第47回日本生物物理学会年会)

2P-080 銅イオン輸送性P-type ATPaseの機能解析と低分解能溶液構造(膜蛋白質,第47回日本生物物理学会年会)

FET3P, ceruloplasmin, and the role of copper in iron metabolism

Publisher Summary The chapter focuses on the copper ferroxidases and discusses the role of copper in iron metabolism. The physiologic linkage between copper and iron is now well understood at the molecular level, in terms of the gene products that metabolically link these two essential metal nutrients. The central component in this linkage is a multicopper ferroxidase: ceruloplasmin, Fet3p, in mammals. However, each of these copper proteins relies on a copper ATPase found in the membrane of a specific vesicular compartment for the copper necessary for each protein's activation. The copper pumping that any one of these ATPases does may be, critical to copper homeostasis as well for copper excretion, for example. These pumps in turn rely on a protein, a copper chaperone that ferries the copper from the plasma membrane copper permease through the cytosol to this vesicular compartment. The permease relies on a plasma membrane cuprireductase to supply it with the Cu(I) as substrate for uptake. Nonetheless, irrespective of whether or how a defect in any one of these enzymes, transporters, chaperones, or pumps may contribute to a dysfunction in copper handling, there most certainly will be a direct impact on the copper incorporation into one or more of these ferroxidases leading to a secondary effect on iron homeostasis. The copper ferroxidases are central to this secondary nutritional, metabolic, essentially epistatic relationship between copper and iron in eukaryotes.

Copper pumping ATPases: Common concepts in bacteria and man

Recently, four genes encoding putative copper pumping ATPases have been cloned from widely different sources: two genes from Enterococcus hirae that are involved in copper metabolism and two human genes that are defective in the copper-related Wilson and Menkes disease. The predicted gene products are P-type ATPases. They exhibit extensive sequence similarity and appear to be members of a new class of ATP driven copper pumps involved in the regulation of cellular copper.