Effect of Compressive Stress on Copper Bonding Quality and Bonding Mechanisms in Advanced Packaging

The thermal expansion behavior of Cu plays a critical role in the bonding mechanism of Cu/SiO2 hybrid joints. In this study, artificial voids, which were observed to evolve using a focused ion beam, were introduced at the bonded interfaces to investigate the influence of compressive stress on bonding quality and mechanisms at elevated temperatures of 250 °C and 300 °C. The evolution of interfacial voids serves as a key indicator for assessing bonding quality. We quantified the bonding fraction and void fraction to characterize the bonding interface and found a notable increase in the bonding fraction and a corresponding decrease in the void fraction with increasing compressive stress levels. This is primarily attributed to the Cu film exhibiting greater creep/elastic deformation under higher compressive stress conditions. Furthermore, these experimental findings are supported by the surface diffusion creep model. Therefore, our study confirms that compressive stress affects the Cu–Cu bonding interface, emphasizing the need to consider the depth of Cu joints during process design

High-efficient thin-film GaN LEDs fabricated by the technique of nanorod template and selective electroplating

[[conferencetype]]國際[[iscallforpapers]]Y[[conferencelocation]]Sanya, Chin

Investigation of GaN Films Grown on Liquid-Phase Deposited SiO 2 Nanopatterned Sapphire Substrates

A simple, easy and relatively inexpensive liquid phase deposition (LPD) method was used to introduce nano SiO 2 on sapphire substrates to fabricate nanoscale patterned sapphire substrates (PSS). Two kinds of nanoscale PSS were used to grow GaN, namely "NPOS" which is nano-pattern oxide on sapphire substrate and "NPSS" which is nano-patterned sapphire substrate. It was found that upper region of NPSS-GaN had the best quality. This is because as the growth time increased, laterally-grown GaN caused the threading dislocations to bend toward the patterns. Besides, voids formed on the NPSS pattern sidewalls caused more threading dislocation bending toward these voids. © 2012 The Electrochemical Society. [DOI: 10.1149/2.007202jss] All rights reserved. Manuscript submitted February 15, 2012; revised manuscript received April 17, 2012. Published July 20, 2012 High-brightness GaN-based light-emitting diodes (LEDs) have been highly demanded in various fields. For the purpose of nextgeneration application of solid-state lighting, LEDs with higher internal and external quantum efficiency are required. Among many methods, lots of efforts have been invested on patterned sapphire substrates (PSS) to improve the quality of GaN film and light extraction efficiency. 1 As a result, the internal quantum efficiency and the leakage current of GaN-based LEDs were improved. Experimental Two kinds of nanoscale PSS were used to grow GaN. Samples designated as "NPOS" are nano-pattern oxide on sapphire substrate, while samples designated as "NPSS" are nano-patterned sapphire substrate. Two-inch c-plane sapphire substrate was used in this study. LPD was used to fabricate NPOS. Sapphire substrate was first immersed in mixed solution of H 2 SiF 6 saturated with silica gel and H 3 BO 3 (0.01 mol/l) for 60 min. The related LPD reaction equations on sapphire substrate were listed as follows: SiO 2 can be formed after the dehydration of OH-bonded siloxane oligomer [SiF m (OH) 4−m ] by catalytic reaction. 12 These substrates were then annealed at 900 • C in N 2 ambient for 30 minutes to improve SiO 2 quality. To fabricate the NPSS, NPOS was etched in hot H 3 PO 4 -based solutions. Then, samples were dipped into 1% diluted hydrogen fluoride (DHF) solution to remove the LPD-SiO 2 . 16 * Electrochemical Society Active Member. z E-mail: [email protected] After the cleaning process, GaN-based LED structures were grown by metal-organic chemical vapor deposition (MOCVD) on both substrates. For the purpose of comparison, LED structures were also grown on unpatterned sapphire substrate and denoted as FLAT. The crystal quality and optical performance of GaN were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron-microscopy (TEM), X-ray diffraction (XRD), monochromated cathodoluminescence (CL) and photoluminescence (PL). Results and Discussion The nature of GaN crystal qualities on sapphire substrates was first analyzed by XRD rocking curves. Both symmetric (002) and asymmetric (102) reflections were measured as shown in The CL spectra intensities collected around the lower and upper regions are summarized i

Crystal Quality and Light Output Power of GaN-Based LEDs Grown on Concave Patterned Sapphire Substrate

The crystal quality and light output power of GaN-based light-emitting diodes (LEDs) grown on concave patterned sapphire substrate (CPSS) were investigated. It was found that the crystal quality of GaN-based LEDs grown on CPSS improved with the decrease of the pattern space (percentage of c-plane). However, when the pattern space decreased to 0.41 μm (S0.41-GaN), the GaN crystallinity dropped. On the other hand, the light output power of GaN-based LEDs was increased with the decrease of the pattern space due to the change of the light extraction efficiency

Suppressing the Initial Growth of Sidewall GaN by Modifying Micron-Sized Patterned Sapphire Substrate with H₃PO₄-Based Etchant

Micron-sized patterned sapphire substrates (PSS) are used to improve the performance of GaN-based light-emitting diodes (LEDs). However, the growth of GaN is initiated not only from the bottom c-plane but also from the sidewall of the micron-sized patterns. Therefore, the coalescence of these GaN crystals creates irregular voids. In this study, two kinds of nucleation layers (NL)—ex-situ AlN NL and in-situ GaN NL—were used, and the growth of sidewall GaN was successfully suppressed in both systems by modifying the micron-sized PSS surface

Dependence of Photoresponsivity and On/Off Ratio on Quantum Dot Density in Quantum Dot Sensitized MoS2 Photodetector

Non-radiative energy transfer (NRET) from quantum dots (QDs) to monolayer MoS2 has been shown to greatly enhance the photoresponsivity of the MoS2 photodetector, lifting the limitations imposed by monolayer absorption thickness. Studies were often performed on a photodetector with a channel length of only a few μm and an active area of a few μm2. Here, we demonstrate a QD sensitized monolayer MoS2 photodetector with a large channel length of 40 μm and an active area of 0.13 mm2. The QD sensitizing coating greatly enhances photoresponsivity by 14-fold at 1.3 μW illumination power, as compared with a plain monolayer MoS2 photodetector without QD coating. The photoresponsivity enhancement increases as QD coating density increases. However, QD coating also causes dark current to increase due to charge doping from QD on MoS2. At low QD density, the increase of photocurrent is much larger than the increase of dark current, resulting in a significant enhancement of the signal on/off ratio. As QD density increases, the increase of photocurrent becomes slower than the increase of dark current. As a result, photoresponsivity increases, but the on/off ratio decreases. This inverse dependence on QD density is an important factor to consider in the QD sensitized photodetector design

Incorporation of Au Nanoparticles on ZnO/ZnS Core Shell Nanostructures for UV Light/Hydrogen Gas Dual Sensing Enhancement

ZnO/ZnS nanocomposite-based nanostructures exhibit dual light and gas sensing capabilities. To further boost the light/dual sensing properties, gold nanoparticles (Au NPs) were incorporated into the core-shell structures. Multiple material characterizations revealed that Au NPs were successfully well spread and decorated on ZnO/ZnS nanostructures. Furthermore, our findings show that the addition of Au NPs could enhance both 365 nm UV light sensing and hydrogen gas sensing in terms of light/gas sensitivity and light/gas response time. We postulate that the optimization of gas/light dual sensing capability may result from the induced electric field and inhabitation of electron-hole recombination. Owing to their compact size, simple fabrication, and stable response, ZnO/ZnS/Au NPs-based light/gas dual sensors are promising for future extreme environmental monitoring