A blue light emitting diode (LED) was prepared by a flip-chip (FC) LED and three-dimensional through-silicon via (3D-TSV) technique. The experimental results indicated that the diameter and length of the Si via were about 180 μm and 400 μm, respectively. The Cu was uniformly and high density filled in each TSV, and the average resistance was about 0.14 m . It was also found that the 96.43Sn-3.57at%Ag bumps were electroplated on the Cu plugged TSVs of a silicon substrate, and these were smoother at 250 • C. After reflow, a 3D blue light emitting diode was prepared by peak bonding at 250 The increasing use of light emitting diodes (LED) in products has promoted the development of higher power, greater density, and lower cost devices. Compared with conventional LED, flip-chip (FC) LED 1-3 have a number of advantages, such as about twice the light output of conventional LED. Flip-chip technology not only shortens the production process, but also significantly reduces thermal resistance and results in a greater heat dissipation rate than seen with the traditional gold wire bonded LED. Moreover, the direct contact of the electrodes or bumps with the package structure can substantially enhance the cooling effect. The flip-chip approach can also remove wire bonding and other wire frame processes, and so these LED can be used with high current drivers.4,5 Therefore, FC LED are attracting growing interest due to their greater heat dissipation, better light emission, higher reliability, and more efficient bonding processes than seen with traditional wire bonded LED.The typical bonding process recommended by chip companies for FC LED is Au/Sn eutectic bonding.6 However, eutectic Sn-Ag alloy is a promising candidate among the various Pb-free solder materials for use with FC LED, and the resulting Sn-Ag alloy bumps 7 can be easily obtained by annealing the Ag/Sn metal stack.There is also demand for new packaging processes for FC LED. 8The use of three-dimensional (3D) packaging through-silicon via (TSV) technology allows a high density of vertical interconnects, unlike 2D packing, as shown in Figure 1. 3D TSV ICs have the following advantages: (1) reduced connection lengths, and thus smaller parasitic capacitance, inductance, and resistance; (2) high-speed low-power interconnects; and (3) a combination of monolithic and multifunctional integration. In this study, a blue LED was prepared using an FC LED and the 3D-TSV technique. We thus propose a new method to achieve 3D LED packing. The detailed fabrication of the TSV and the electrooptical properties of the fabricated are also discussed. ExperimentalFigure 2 presents a schematic diagram of the fabrication process for the 3D LED. A P-type 400 μm thick Si wafer was used as the bottom substrate. Photolithography was used to make a mask for etching the Al layer. A positive type photoresist, AZ-1500, was spin-coated to a thickness of 2 μm with a rotation speed of 500 rpm for 15 s, followed by 3000 rpm for 30 s. The Al layer was etched by wet etching, after using acetone to remove...
A common cathode 3D RGB light emitting diode chip is produced using through silicon via (TSV) technology. The experimental results show that the diameter, the length and the depth of the Si via are about 140 μm, 50 nm and 320 μm, respectively. The Cu is uniform with a high density in each TSV and the average resistance is about 0.61 mΩ. The measurement of the thermal images shows that the temperature at which a 3D LED (105°C) operates is lower than that for a LED (120°C) when the two devices are injected with a 20 mA current. Using 20 mA current injections, the current-voltage (I-V) output for 3D RGB LED chips is on average 218.84 mW/W, 186.65 mW/W and 324.49 mW/W.
We demonstrate indium gallium nitride/gallium nitride/aluminum nitride (AlN/GaN/InGaN) multi-quantum-well (MQW) ultraviolet (UV) light-emitting diodes (LEDs) to improve light output power. Similar to conventional UV LEDs with AlGaN/InGaN MQWs, UV LEDs with AlN/GaN/InGaN MQWs have forward voltages (V(f)'s) ranging from 3.21 V to 3.29 V at 350 mA. Each emission peak wavelength of AlN/GaN/InGaN MQW UV LEDs presents 350 mA output power greater than that of the corresponding emission peak wavelength of AlGaN/InGaN MQW UV LEDs. The light output power at 350mA of AlN/GaN/InGaN MQWs UV LEDs with 375 nm emission wavelength can reach around 26.7% light output power enhancement in magnitude compared to the AlGaN/InGaN MQWs UV LEDs with same emission wavelength. But 350mA light output power of AlN/GaN/InGaN MQWs UV LEDs with emission wavelength of 395nm could only have light output power enhancement of 2.43% in magnitude compared with the same emission wavelength AlGaN/InGaN MQWs UV LEDs. Moreover, AlN/GaN/InGaN MQWs present better InGaN thickness uniformity, well/barrier interface quality and less large size pits than AlGaN/InGaN MQWs, causing AlN/GaN/InGaN MQW UV LEDs to have less reverse leakage currents at -20 V. Furthermore, AlN/GaN/InGaN MQW UV LEDs have the 2-kV human body mode (HBM) electrostatic discharge (ESD) pass yield of 85%, which is 15% more than the 2-kV HBM ESD pass yield of AlGaN/InGaN MQW UV LEDs of 70%.
Nitride-based large size (i.e. 1 mm  1 mm) indium-tin-oxide (ITO) light emitting diodes (LEDs) were successfully fabricated. In order to enhance the output intensity of power chips, Al reflector was deposited by e-beam evaporator on the chip backside. It was found that the 350 mA output power was 84.8 mW (W-P-E ¼ 7:2%) at 460 nm for the power chip with ITO as p-contacts and Al as back-side reflector. It was also found that ITO power chip with Al reflector was more reliable.
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