Aledia Touts MicroLED Chip Progress

Abstract

FRENCH STARTUP FIRM ALEDIA SAYS IT HAS MANUFACtured the first microLED chips using 300-millimeter (mm), or 12-in., silicon wafers. This development could pave the way for more widespread use of microLED technology in smartphones and televisions by leveraging established silicon foundry technology. Traditional LED chips have been produced using 100- and 150-mm (4- and 6-in.) sapphire wafers, upon which flat layers of gallium-nitride (GaN) crystal are deposited. Aledia, which was spun out of the French government-backed research institute CEA-Leti [Laboratoire d'électronique des technologies de l'information] in Grenoble in 2012, has spent the past eight years developing microLED technology for large-area silicon such as 200-mm (8-in.) silicon wafers. It recently used CEA-Leti's pilot lines to make the leap to 300-mm (12-in.) wafers. Aledia says its 3D nanowire technology grows GaN nanowires (GaN crystals of submicron diameter) on top of large-area silicon. According to the company, this doesn't create the stresses seen with the traditional flat-layer approach, as the wafer size is increased. That means its technology could be used to mass-produce microLEDs with the same 200- and 300-mm wafers used by high-yield silicon foundries today to make smartphone and computer processing chips. This also yields cost-effective integration with smaller-node electronics in the process. Volume chip manufacturing is essential for microLED's long-term success, where each pixel in the display is created by a microscopic LED. “We believe producing microLEDs on large-area 300-mm silicon wafers is a world's first, and opens this technology to huge potential-volume-manufacturing capabilities,” Aledia CEO and cofounder Giorgio Anania says in a press release. “The larger size allows 60 to 100 smartphone displays to be made on a single 300-mm wafer, versus approximately four-to-six using the present LED industry-standard, 4-in. sapphire substrate. Thanks to Aledia's unique nanowire LED technology [3D LED], this can be done with commercially available processes and equipment, since it uses standard-thickness [780 micrometer, or μm] silicon wafers.” Aledia has attracted big investors, including Intel Capital, and in 2019 it reached a process-development partnership with Israeli silicon foundry TowerJazz to commercialize its technology. Last fall, it raised $97 million for building its own microLED plant in Grenoble, which it aims to have operational by mid-2022. Aledia is certainly in a strong financial position, but may still be years away from mass-producing microLEDs on 12-in. wafers, says Yole Développement Senior Industry Analyst Eric Virey. He notes the company's development with TowerJazz to date has been confined to 8-in.-wafers and that Aledia worked with CEA-Leti researchers and used the institute's pilot line for the 12-in.-project, which he describes as being more in the research and development stage. microLED Chip WireLED on 300 mm (12 in.) silicon wafer. Source: Aledia However, one of the biggest roadblocks for microLED is cost, says Virey, and one way to address that is to reduce the LED chip's cost. So even moving to 8-in.-silicon production over smaller-format sapphire wafers would have a tangible benefit. “This opens the door to a vast amount of battle-tested 8-in. [complementary metal-oxide semiconductor] tools and CMOS fabs,” he says. “There are a lot of tools developed, more than anything for LED, and there are a lot of used tools for the grab. It would be a brave new world for microLED to get into the world of 8-in. silicon.” Overall, Virey forecasts a slow rollout for microLEDs in TV displays. Samsung has introduced a commercial 110-in. TV, but with a price tag of around $150,000, it's far from a mainstream consumer product. He says that if development goes well, we might see microLED TVs in the same price range as high-end OLED TVs in five or six years. “The goal of the industry for TV is they need to cut costs by a factor of 10 to 20,” says Virey. “There is a credible path to get there, but nobody is saying it's an easy path, and right now OLED and the other technologies are moving targets.” However, microLED looks more feasible for smaller displays. Virey notes that in 2021, Vuzix is commercializing the first augmented reality (AR) glasses that will use microLED, where its brightness is a big advantage. He expects Apple to start making its own microLED displays for the Apple Watch in late 2022, with commercial introduction probably coming in 2023. “They're only now in the process of building a real pilot line, and a lot will depend on the pilot line,” says Virey. “But that would be a serious disruption for the industry, if [Apple] would start making their own displays.” —By Glen Dickson