Nanotwinned metallic thin films offer a promising route to simultaneously achieve high strength and excellent electrical conductivity, making them attractive for electronic applications and advanced packaging. However, the microstructural characteristics and properties of nanotwinned films in alloy systems remain insufficiently explored. In this study, Ag-Cu alloy thin films with high-density nanotwinned structures were successfully fabricated via magnetron cosputtering. Microstructure and underlying mechanisms were investigated using x-ray diffraction (XRD), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), focused ion beam (FIB), and atomic force microscopy (AFM). The results reveal that Ag-Cu alloying leads to a reduction in stacking fault energy, which in turn facilitates the formation of high-density nanotwins with reduced twin spacing and refined grains. The Ag-Cu alloy nanotwinned films exhibit a strong (111) preferred orientation, reaching up to 98.1

The growth of p-type thin film materials with enhanced performance is a promising way to fabricate various optoelectronic devices. The low deposition rate of the high-power impulse magnetron sputtering (HiPIMS) considerably limits the real-time device fabrication process. In this work, the 100 nm thick CuxO films were deposited using a superimposed HiPIMS system, which can contribute to sustainable manufacturing. It is found that when the oxygen flow ratio (fO2) is lower (fO2 = 10 %), the films exhibit n-type conduction due to their copper-rich composition, resulting in very low transmittance and a relatively low optical energy gap. When the fO2 increased, the transition region was observed between 12 % and 15 % in the conduction type due to the quantities of the phases of Cu and Cu2O being considerably similar. When the fO2 exceeds 17.5 %, the films exhibited p-type conduction was achieved and were predominantly composed of the Cu2O phase. The crystallinity of the Cu2O films improved significantly as the fO2 continued to rise. The photoluminescence (PL) spectrum shows that, as the fO2 increases from 17.5 % to 25 %, the p-type conduction of the Cu2O films is mainly caused by copper vacancies (Vcu). The crystallinity of the films was primarily influenced by the Vcu concentration. When the films possessed a lower Vcuconcentration, their crystallinity increased, leading to a significant enhancement in transmittance and a broadening of the optical energy gap, which was observed in a higher fO2 range (beyond 20 %). This study revealed that the CuxO films can be converted from n-type to p-type conduction using an easy way by the O2 flow ratio tuning in superimposed HiPIMS technique.

Ag sintering has become a preferred die bonding method for power IC packages due to its exceptional thermal, mechanical, and electrical properties. While it is widely recognized for its potential in high-power semiconductor applications, few research efforts have emerged that consider how the backside metallization films of the IC can enhance the sintering layer’s properties. This research focused on the enhancement of silver sintering for bonding of Cr/Ni/Ag and Cr/nanotwinned Ag-metallized film on silicon carbide (SiC) chips to direct bonded copper (DBC) substrates to investigate the beneficial effects of (111)-textured Ag nanotwinned films on the bonding strength increase and porosity reduction. Results reveal that the nanotwinned Ag films significantly reduce porosity and enhance bonding strength compared to conventional Cr/Ni/Ag films, under both pressurized and pressureless conditions. Implications for the improvements in reducing porosity and increasing bonding strength due to the nanotwin structure and further research are also discussed, opening new possibilities for advanced power electronic packaging technology.

Silver paste sintering is a promising die attachment technology for power electronic devices due to its high thermal and electrical conductivities, as well as superior mechanical properties. This study presents the silver sintered die bonding of SiC/DBC power modules with traditional Ti/Ni/Ag backside metallization and Ti/Ag nanotwinned metallization with a high-density (111) orientation. Cross-sectional analyses of the sintered die bonding joints of Ti/Ag nanotwinned metallized SiC chip with DBC substrate indicate minimal porosity at the interface, leading to increased shear strength. Additionally, fractographic analysis highlights the effective bonding between the silver sintering paste and the nanotwinned film. An innovative “Green channel model” is proposed that the interface between the silver sintered layer and nanotwinned thin film with (111) orientation provides a rapid path for the silver atoms supplied by the silver sintered particles to be transported to the gaps of Ag powders, leading to the effective reduction of sintering porosity and increase of die bonding strength. The high diffusivity of nanotwins effectively promotes silver-sintered die bonding, particularly at lower temperatures, indicating the potential of applications in electronic packaging of power modules.

Nanotwinned face-centered-cubic (FCC) metals have gained significant attention recently due to their exceptional mechanical and electrical properties. Among all the FCC metals, Ag has the lowest stacking fault energy, which allows twin formation to easily occur. In this study, Ag films with a thickness of 4 µm were deposited on Si (100) substrates pre-coated with Ti adhesion layers by electron beam evaporation. With ion beam assistance during the evaporation process, highly (111)-textured and high-density nanotwinned Ag films with excellent properties were produced. Both x-ray diffraction (XRD) and electron backscatter diffraction (EBSD) analyses indicate that the Ag film possesses a strong (111) preferred orientation. In addition, statistical measurements from transmission electron microscopy (TEM) images show that the average twin spacing in nanotwinned Ag films with a deposition rate of 1.8 nm/s is only 6.1 nm. However, conventional models based on thermodynamics are insufficient to describe the formation of growth twins in an ion beam-assisted deposition system. Therefore, an ion bombardment stress model is introduced in this work. The results of the mechanism of deformation twinning are also discussed.

The nanotwinned structure has been attracting a great deal of attention due to its excellent mechanical and electrical properties.In this study, ultra-thin nanotwinned Cu (nt-Cu) films with a thickness of 1.5 μm were fabricated by DC magnetron sputtering with moderate substrate bias.Within these films, an equiaxed-grain transition layer only 100-400 nm thick formed between the nanotwinned region and Si substrate and was observed by focused ion beam (FIB).The XRD and EBSD analyses indicated that the as-deposited nanotwinned films had a strong (111) preferred orientation.The surface roughness of the films, as measured with an atomic force microscope (AFM), was below 10 nm, which was sufficiently smooth for chip bonding at low temperature with minor pressure.Direct bonding of Si chips sputtered with such ultra-thin nt-Cu films with a (111) preferred orientation has been evidenced to yield a sound interface, and this bonding method can be applied for the manufacturing of 3D-IC packages.

Ultrasonic ribbon bonding has gained much attention due to the endeavor of achieving higher module performance in power electronic packaging. Among all the ribbon materials, Ag ribbon is a promising candidate due to its superior electrical properties. However, research which has reported the bonding of the ribbon on chip side is scant. Thus, in this study, the authors carried out bonding of the Ag ribbon on various types of metallized wafers to examine the feasibility of Ag ribbon, simulating the bonding scenario on the chip side in power modules. Results revealed that bonding of the Ag ribbon is feasible on those wafers metallized Ag on top. The authors also discussed the implications for the bondability of Ag ribbon with different types of metallization layers.

Epitaxial Ag nanotwinned films with highly (111)preferred orientation were deposited by magnetron sputtering onto germanium substrates, some with the addition of a Ti layer and application of negative substrate bias.A high density of Ag nanotwins with an average twin spacing of 2.18 nm formed in the Ag columnar structures.Twin boundaries formed along the direction perpendicular to the growth direction of the film.The influences of the Ti interlayer and negative substrate bias on the formation of Ag nanotwins were also examined.The highly (111)-textured thin films had an impressive film surface roughness, as low as 11.2 nm.The (111)-oriented nanotwins provided higher surface diffusivity than did other orientations.The electrical resistivity decreased significantly as more ( 111)oriented nanotwinned structures formed.The bonding experiment was also performed at 200 ℃ for 60 min at a bonding pressure of 20 MPa, and extremely rare voids appeared at the bonding interface.The combination of low surface roughness, rapid diffusivity on the (111)-planes, and lower electrical resistivity present a high possibility of reliable interconnections for future microelectronic technology via direct bonding.

This article presents a method of enhancing the performance of sputtered Cu nanotwinned films on Ti pre-coated SiC substrate. Before deposition, the substrate was RF pre-sputtered by argon discharge at a bias of − 500 V for 30 min to remove the surface oxide layer and contamination, while simultaneously, the substrate was bombarded with argon ions. The results show that a nanotwinned structure with surface activation before sputtering has a thinner transition layer. In addition, the titanium adhesive layer and the Cu nanotwinned film have stronger (002) and (111) peaks, respectively. Cu nanotwinned film on Ti pre-coated SiC substrate with ion surface activation has a higher (111) orientation of 92.4

This study proposes a novel approach for applying the nanotwinned Ag thin films in CO2 reduction.We focus on optimizing the sputter deposition process of nanocrystalline Ag structures on n+Si chips and preparing nanotwinned silver catalysts with good structure, adhesion, and stability.The effects of twinned structure catalysts on the photocatalytic performance were investigated.In this research, the n+ Si/Gr/sputtered Ag structure was used as the photoelectrode for photoelectrochemical (PEC) CO2 reduction reaction (CO2RR) since the utilization of graphene can expedite carrier transport, thereby improving device stability and performance in electrolytes.Nanotwinned Ag films were successfully synthesized on graphene transferred n+Si substrates with DC magnetron sputtering.Focused ion beam analyses demonstrated that the addition of graphene did not diminish the nanotwin density; rather, it improved the quality of the sputtered Ag thin films, which leads the framework to a potential structure for PEC CO2RR.

Silicon carbide (SiC) has long been known for its potential to replace Si and has rapidly emerged as a new power device material that provides opportunities to extend the power, temperature, or frequency capabilities of power modules. In this study, an innovative method for the die bonding of SiC chips with DBC alumina substrates has been performed at 250 °C using (111) preferentially oriented Ag nanotwinned films. For this purpose, the optimized conditions for the deposition of such Ag nanotwins using magnetron sputtering and electron beam evaporation techniques were investigated. The results indicated amounts of 36.4 and 3.5

The mechanisms of the formation of nanotwinned structures have recently attracted attention due to the advantageous properties of the structures. This article describes the microstructural evolution of (111)-oriented nanotwins into huge (200)-oriented grains with grain sizes exceeding the film thickness. The results reveal that the initiation temperature for abnormal grain growth can be improved to nearly 300 °C by altering the microstructure of the nt-Ag films with the application of substrate bias during deposition. Densification of the nt-Ag films by substrate bias reduces the number of fine equiaxed grains in the transition layer and hence reduces the overall grain boundary energy of the nt-Ag film. The lower number of discontinuities that form within the nanotwinned layer retards the lateral growth of the columnar grains. The combination of the effects is conducive to the thermal stability of Ag nanotwinned films, implying promising future applications in microelectronics.

Present developing trends in the miniaturization and power escalation on electronic components have driven research interest in thermal interface materials (TIMs) to solve the fundamental issue of heat dissipation. Among the various TIMs, the In32.5Bi16.5Sn low melting alloy (LMA) has drawn much attention owing to its low melting point and great bondability, which could mitigate the warpage issue and provide very low thermal interface resistance. In this study, the Cu/In32.5Bi16.5Sn/Cu structure was used to simulate the practical conditions of the application of TIM in joining the substrate and heat sink. The thermal properties before and after an aging test at 80 degrees C were measured with a thermal tester, and the growth kinetics of the intermetallic compound (IMC) at the In32.5Bi16.5Sn/Cu interface were investigated. Without fast dissolution of Cu into the In32.5Bi16.5Sn alloy, the growth kinetics of the IMC at the interface were found to be diffusion-controlled at the temperature studied. It was found that the main change in the Cu/ In32.5Bi16.5Sn/Cu system after the aging test was the thickening of the IMC, and the interface was free of cracks. As the aging time increased, the thermal impedance increased to twice that of the initial value, showing parabolic degradation, which is relevant to the growth kinetics of the IMC at the interface. Implications for the degradation of the thermal performance and further research are also discussed.(c) 2022 Elsevier B.V. All rights reserved.

The exceptional properties of nanotwinned structures have been a hot area of research in recent years.Silver (Ag) has the lowest stacking fault energy (SFE) among all FCC metals, which has a strong tendency to form a twin structure.Also, sapphire substrates are ideal for use in LED applications due to high-temperature resistance, high strength, good electrical insulations, and low dielectric loss.Depositing Ag nanotwinned films on sapphire substrates can serve as a perfect candidate for die bonding in LED manufacturing.In this study, both sputtering and evaporating methods had been demonstrated for the fabrication of high density (111)-textured Ag nanotwinned films on sapphire wafers.Microstructural analyses show that both the sputtered and evaporated Ag grains presented a high density of twin structure.The cross-sectional EBSD analysis of the sputtered Ag nanotwinned film indicated a highly (111)-preferred orientation to 34.6% of the overall grains.Further, the sputtering process allows the production of surface roughness of the Ag nanotwinned film up to 65.1 nm.The epitaxial growth of Ag nanotwinned films with (111)-preferred orientation can be utilized by both the deposition methods.

Epitaxial Ag nanotwinned films with highly (111)-preferred orientation were deposited by magnetron sputtering onto germanium substrates, some with the addition of a Ti layer and application of negative substrate bias.A high density of Ag nanotwins with an average twin spacing of 2.18 nm formed in the Ag columnar structures.Twin boundaries formed along the direction perpendicular to the growth direction of the film.The influences of the Ti interlayer and negative substrate bias on the formation of Ag nanotwins were also examined.The highly (111)-textured thin films had an impressive film surface roughness, as low as 11.2 nm.The (111)-oriented nanotwins provided higher surface diffusivity than did other orientations.The electrical resistivity decreased significantly as more (111)-oriented nanotwinned structures formed.The bonding experiment was also performed at 200℃ for 60 min at a bonding pressure of 20 MPa, and extremely rare voids appeared at the bonding interface.The combination of low surface roughness, rapid diffusivity on the (111)-planes, and lower electrical resistivity present a high possibility of reliable interconnections for future microelectronic technology via direct bonding.

Solar light is a renewable source of energy that can be used and transformed into electricity using clean energy technology. In this study, we used direct current magnetron sputtering (DCMS) to sputter p-type cuprous oxide (Cu2O) films with different oxygen flow rates (fO2) as hole-transport layers (HTLs) for perovskite solar cells (PSCs). The PSC device with the structure of ITO/Cu2O/perovskite/[6,6]-phenyl-C61-butyric acid methyl ester (PC61BM)/bathocuproine (BCP)/Ag showed a power conversion efficiency (PCE) of 7.91%. Subsequently, a high-power impulse magnetron sputtering (HiPIMS) Cu2O film was embedded and promoted the device performance to 10.29%. As HiPIMS has a high ionization rate, it can create higher density films with low surface roughness, which passivates surface/interface defects and reduces the leakage current of PSCs. We further applied the superimposed high-power impulse magnetron sputtering (superimposed HiPIMS) derived Cu2O as the HTL, and we observed PCEs of 15.20% under one sun (AM1.5G, 1000 Wm−2) and 25.09% under indoor illumination (TL-84, 1000 lux). In addition, this PSC device outperformed by demonstrating remarkable long-term stability via retaining 97.6% (dark, Ar) of its performance for over 2000 h.

This study focuses on the analyses of nano-twinned copper (Cu) films deposited through magnetron sputtering on silicon carbide (SiC) chips. The investigation encompasses the utilization of a chromium (Cr) adhesive layer coupled with varying voltage bias conditions. The goal is to comprehensively examine the influence of the adhesive layer and negative bias voltages, contributing to an enhanced understanding of materials engineering and bonding technologies for advanced applications. The formation of a nano-twinned structure and (111) surface orientation can be properly controlled by applied substrate bias. High-density nanotwinned structures were introduced into Cu films sputtered on SiC substrates with 82.3% of (111) orientation proportion at −150 V, much higher than the Cu film sputtered with another substrate bias. It is concluded that the sputtered Cu nanotwinned film formed with −150 V bias voltage has the potential to be employed as the interlayer for low-temperature direct bonding.