Cree chooses to build it's Billion dollar plant near Utica NY and there's another near by.
22 October 2019
Odyssey acquires fab to allow small-scale production over 10,000 wafers/year Odyssey Semiconductor Technologies Inc, which is developing high-voltage power switching components and systems based on proprietary gallium nitride (GaN) processing technology, has completed the acquisition of an integrated semiconductor design, fabrication, test and packaging facility (as well as associated tooling) in Ithaca, NY, USA.
Complete with a mix of class 1000 and class 10,000 cleanroom space as well as tools for semiconductor development and production, the 10,000ft2 facility is suitable for compound semiconductor device development and small-scale production with a wafer capacity exceeding 10,000 wafers/year.
Lithography capabilities include i-line steppers adapted for handling small pieces up through 200mm-diameter wafers. High-throughput metal and dielectric deposition equipment and advanced etch and packaging tools should allow Odyssey to accelerate development of its proprietary >1000V GaN power-switching transistor technology. The facility will also expand Odyssey's existing device development and foundry service.
Odyssey has been developing its proprietary vertical-conduction GaN transistor technology at various user-facility labs. The firm reckons that, with the new facility, it can significantly accelerate the development of its GaN power-switching transistor products operating above 1000V.
“This acquisition dramatically improves our ability to design and manufacture our proprietary disruptive GaN-based high-voltage switching power-conversion devices and systems and should accelerate our timeline into prototype and commercial production,” says co-founder & CEO Dr Rick Brown.
Odyssey is currently developing its technology to produce GaN-based high-voltage switching power-conversion devices and systems, targeted at supplanting silicon carbide (SiC) as the dominant premium power-switching device material.
GaN-based systems outperform silicon- and SiC-based systems due to GaN’s superior material properties. To date, processing challenges have limited GaN devices to operating voltages below 1000V. Odyssey says that it has developed a novel technique that will allow GaN to be processed in a manner that, for the first time, will make production of high-voltage GaN power-switching devices operating above 1000V viable.
Currently dominated by silicon carbide, the premium power switching device market (i.e. applications where silicon systems perform insufficiently) is projected to exceed $3.5bn by 2025, driven largely by the rapid adoption of electric vehicles (EV) and hybrid electric vehicles (HEV) and the growing number of installations of renewables such as solar and wind power as well as increased demand for more efficient industrial motor drives.
Tags: SiC power devices
Visit: www.odysseysemi.com
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P.S.
18 October 2019
Vertical gallium nitride light-emitting diodes on 4-inch silicon wafers Researchers in China have integrated high-power, reliable vertical indium gallium nitride (InGaN) light-emitting diodes (LEDs) on 4-inch silicon substrates [Shengjun Zhou et al, Optics Express, vol27, pA1506, 2019]. The team from Wuhan University, Changchun Institute of Optics, Fine Mechanics and Physics, and Xiamen Changelight Co Ltd, used a number of measures to improve the performance of the final LEDs by reducing current crowding and protecting the device structure from humidity.
Figure 1: Vertical LED device layer MOCVD growth sequence.
The device layers were grown on patterned sapphire substrates using metal-organic chemical vapor deposition (MOCVD; see Figure 1). The LED fabrication began with inductively coupled plasma (ICP) etch into 1mmx1mm mesas for electrical isolation. A silicon dioxide (SiO2) current-blocking layer (CBL) was applied using plasma-enhanced CVD and patterning into 15µm-wide strips using photolithography and buffered-oxide wet etch (Figure 2).
Figure 2: Fabrication process of LEDs: (a) MOCVD growth; (b) defining SiO2 CBL; (c) metal deposition and bonding to Si wafer; (d) laser lift-off (LLO) removal of sapphire substrate; (e) ICP etch to n-GaN contact; (f) deposition of p- and n- electrodes. (g) Scanning electron microscope (SEM) image of exposed n-GaN surface with hemispherical dimples after LLO and ICP etching. (h) Cross-sectional SEM image of LEDs bonded to Si wafer. (i) Photograph of LEDs on 4-inch Si wafer; colors arise from thin-film interference effects.
Ion-beam sputtering applied a 100nm silver film as reflector, followed by titanium/tungsten as a diffusion barrier. After electron-beam deposition of a platinum/titanium cap, rapid thermal annealing at 600°C was used to improve the GaN/silver ohmic contact.
The 4-inch-diameter p-Si final device substrate was prepared by adding multi-layers of titanium/platinum/gold and a titanium/platinum cap. A 2.5µm layer of indium was applied to the p-Si substrate before thermal compression bonding at 230°C. One feature of the titanium adhesion layer was that it also acted as a barrier against poisoning of the p-Si with gold. Platinum contamination of the p-Si was also avoided, according to energy-dispersive x-ray analysis.
A 248nm krypton-fluoride excimer laser was used to perform lift-off separation of the sapphire growth substrate. This was followed by ICP etch down to the n-GaN contact layer.
The n-GaN was treated with potassium hydroxide (KOH) or phosphoric acid (H3PO4) solution to texture the surface for improved light extraction. Chromium/platinum/gold was used to form the p- and n-electrodes for the LED. The n-contact metals were formed into 12µm-wide fingers.
The SiO2 CBL around the opaque electrodes directed current away from this region and made for more uniform current density in the light-emitting areas, according to simulations. Along with the vertical structure, it was hoped the CBL would reduce self-heating, making for more efficient performance over lateral structure devices. Current crowding increase leading to self-heating is a major problem in conventional lateral structure LEDs.
The vertical LED structure enabled much lower forward voltages for a given current injection – 2.87V at 350mA, compared with 3.52V with a conventional lateral LED structure (Figure 3). Lower forward voltage indicates lower input power and hence higher power efficiency. The light output power (LOP) for a given current injection was also higher in the vertical LED: lateral LED output saturated at ~320mA, while the vertical device increased in light power up to 1300mA. “The absence of premature LOP saturation in V-LEDs was attributed to reduced current crowding and enhanced heat dissipating compared to L-LEDs,” the team writes.
Figure 3: (a) Current-voltage profiles of lateral (L-) and vertical (V-)LEDs. (b) Light output power-current characteristics.
With 350mA, the vertical LED output power was 501mW, beating a previous report of a GaN vertical blue LED of ~450mW at the same injection. The researchers comment: “The higher LOP demonstrated in this work confirmed that integrating the optimized metallization scheme, SiO2 CBL and surface texturing by KOH wet etching is an effective approach to higher-performance V-LEDs.”
[I get a crude output/input power efficiency value of 50% (501mW/(2.87Vx350mA).]
The researchers also developed a platinum/titanium protective wrap-around layer for the silver/titanium-tungsten alloy structure. The wrap-around structure protected the mirror contact from humidity degradation. Operation at 85°C and 85% relative humidity degrade the performance of LEDs without lateral wrap-around protection over 1000 hours. By contrast, the LEDs with wrap-around platinum/titanium showed “negligible optical degradation even after an aging time of 1008h,” according to the researchers.
Tags: Vertical InGaN LEDs InGaN LEDs MOCVD Silicon substrates
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