Thermal Stability of the Copper and the AZO Layer on Textured Silicon

Transparent conductive oxide (TCO) film is the most widely used front electrode in silicon heterojunction (SHJ) solar cells. A copper metallization scheme can be applied to the SHJ process. The abundance of zinc in the earth’s crust makes aluminum-doped zinc oxide (AZO) an attractive low-cost substitute for indium-based TCOs. No work has focused on the properties of the copper and AZO layers on the textured silicon for solar cells. This work deposited an aluminum-doped zinc oxide layer and copper metal layer on textured (001) silicon by a sputtering to form Cu/AZO/Si stacks. The structures of Cu/AZO/Si are characterized by scanning electron microscope (SEM), scanning transmission electron microscope (STEM), and energy-dispersive X-ray spectrometer (EDS). The results show that the copper thin film detached from AZO in the valley of the textured silicon substrate at a temperature of 400 °C. Additionally, the gap between the copper and AZO layers increases as temperature increases, and the 65 nm thickness AZO layer was found to be preserved up to 800 °C.

Influence of Alloying Elements on the Mechanical Properties of Anodized Aluminum and on the Adhesion of Copper Metallization

The active development of the power electronics market and a constant increase in the prices of components require new materials and approaches, including a power module packaging technology. The use of aluminum instead of copper in the power module baseplate is an interesting and promising solution. The insulated metal baseplate is one of the most extensively developed technologies nowadays. The object of this study is an insulated metal substrate based on anodized aluminum. The main goal of the article is the comparison of copper topology adhesion to an anodized aluminum oxide layer formed on different aluminum alloys with aluminum content of at least 99.3 wt %. Peel test and pull-off adhesions showed a twofold difference for both aluminum alloys. The high ordered defect-free anodized alumina formed on alloys with copper content of 0.06 wt % had a mean pull-off adhesion of 27 N/mm2 and hardness of 489 HV. In the case of the alloy with copper content of around 0.15 wt %, it had hardness of 295 HV and a mean pull-off adhesion of 12 N/mm2. The results of our microstructure investigation showed that anodized alumina based on alloys with copper content of around 0.15 wt % is fragile due to spherical holes. Summing up the results, it can be concluded that not all initial impurities are critical for anodized alumina, but some, specifically copper, dramatically decreased the mechanical properties of anodized alumina.

Laponite-Mediated Copper Metallization by Palladium Intercalation

An alternative catalytic method was employed using the reduction of Pd ions on the surface of cetyltrimethylammonium bromide (CTAB) treated laponite to initiate the electroless plating of copper; the deposition features of the Pd nanoparticles produced were investigated in detail. Results indicated intercalation and reduction of Pd nanoparticles occurred at room temperature and involved interaction between the laponite and the cetyltrimethylammonium cationic templates. Organic species and amount on laponite were optimized to adjust silicate platelet interlayer distances and platelet organophilic properties. Intercalation of Pd nanoparticles occurred between the magnesium silicate layers of laponite and this was dependent on pre-treatment and impregnation times. As impregnation is a method of producing heterogeneous catalysts, we considered Pd nanoparticles on laponite templates could catalyze the electroless deposition of Cu to initiate metallization. Cu films fabricated on laponite templates exhibited excellent surface roughness (˜1.7 nm) and low resistivity (˜3.42 μΩ). The devised approach enabled the facile formation of a network suitable for Cu metallization without causing substrate damage and produced metal surfaces with excellent flatness and resistivity.

Influence of the Low-Pressure Cold Spray Operation Parameters on Coating Properties in Metallization of Ceramic Substrates Using Copper and Aluminum Composite Powder

The low-pressure cold spray (LPCS) technique could be an attractive method for copper metallization of ceramic substrates to power module applications due to its one-step quick and lowtemperature process. However; manufacturing pure copper coating on a ceramic substrate by LPCS is still challenging due to its low deposition efficiency and poor adhesion strength. Our previous study successfully demonstrated the possibility of obtaining a zirconia substrate's metallization by using a feedstock powder mixture of copper and aluminum. However; the copper content in the coating was not high enough for power module applications. Therefore; in this study; we aim to improve the copper content in the coating layer composed of the composite powder deposited by LPCS on alumina and zirconia substrates. The influence of the gas pressure and standoff distance on the copper content and coating thickness are evaluated. The coating build-up with a high copper content and thickness is highly dependent on the kinetic energy of particles; enhanced by high gas pressure and short stand-off distance.

Warpage Behavior on Silicon Semiconductor Device: The Impact of Thick Copper Metallization

Electrochemical deposited (ECD) thick film copper on silicon substrate is one of the most challenging technological brick for semiconductor industry representing a relevant improvement from the state of art because of its excellent electrical and thermal conductivity compared with traditional materials, such as aluminum. The main technological factor that makes challenging the industrial implementation of thick copper layer is the severe wafer warpage induced by Cu annealing process, which negatively impacts the wafer manufacturability. The aim of presented work is the understanding of warpage variation during annealing process of ECD thick (20 μm) copper layer. Warpage is experimentally characterized at different temperature by means of Phase-Shift Moiré principle, according to different annealing profiles. Physical analysis is employed to correlated the macroscopic warpage behavior with microstructure modification. A linear Finite Element Model (FEM) is developed to predict the geometrically stress-curvature relation, comparing results with analytical models.