An employee walks past the headquarters of ASML, a Dutch company that is currently the largest supplier in the world of semiconductor manufacturing machines via photolithography systems, in Veldhoven on April 17, 2018. Photo: AFP / Emmanuel Dunand
Canon has announced a new nanoimprint lithography system that it says can transfer circuit patterns equivalent to those created by 5nm EUV photolithography. Furthermore, it claims that with the improvements it anticipates in mask technology, the transfer of 2nm-equivalent circuit patterns should be possible.
If this can be done economically, it would be a direct challenge to ASML, which has a monopoly on the EUV (extreme ultraviolet) photolithography equipment used by Taiwan Semiconductor Manufacturing Company (TSMC) to make the most advanced integrated circuits (ICs) designed by Apple, Nvidia and Intel.
In contrast to photolithography, in which light from a scanner passes through a photomask to transfer circuit pattens to a wafer coated with a photosensitive resist, nanoimprint lithography is a miniature mold and stamping process. In nanoimprint lithography, the mask is a mold.
According to Canon, its FPA-1200NZ2C nanoimprint system features new environmental control technology that significantly reduces the number of defects caused by fine particles created during the manufacturing process. Defect reduction has been a major challenge for Canon in its efforts to commercialize nanoimprint IC lithography.
How to precisely align mold and wafer has been another difficult problem, but Canon’s announcement indicates that it is being solved, at least for relatively simple devices without too many layers that need to be aligned. It is not clear where the physical limits to nanoimprint technology are, but 2 nanometers is the smallest semiconductor production process likely to be commercialized within the next few years.
Because it does not require expensive light sources and lens arrays, nanoimprint lithography could in theory offer a 90% reduction in power consumption, a 40% reduction in overall processing cost, and equipment priced at a fraction of ASML’s EUV scanners – an order of magnitude cheaper according to Canon chairman and chief executive officer Fujio Mitarai.
EUV lithography systems can cost US$150 million or more, and Intel reportedly paid more than $340 million for one ASML’s next-generation high-NA (numerical aperture) models. These prices are so high that only the biggest semiconductor makers can afford to use EUV. Because of the difference in price and curiosity about the technology, Canon has received numerous inquiries about nanoimprint lithography from potential customers.
In practice, nanoimprint lithography also has an issue with throughput. Canon says that “complex two- or three-dimensional circuit patterns can be formed in a single imprint, which may reduce the cost of ownership,” but nanoimprint is basically a stamp-and-repeat process while photolithography can scan an entire wafer or large parts of a wafer to make multiple copies of the same design.
For this reason, some industry experts believe that nanolithography will first be used to make relatively simple memory chips, not the complex logic chips fabricated by TSMC. This may explain Canon’s long-standing partnership with Kioxia, which is the second-largest producer of NAND flash memory after Samsung Electronics. Kioxia was formerly a division of Toshiba.
China sales unlikely
Canon is building a new factory north of Tokyo that is scheduled to start producing nanoimprint lithography equipment in 2025. After nearly a decade of development, Kioxia reportedly plans to start using nanoimprint lithography in mass production of NAND flash memory that same year.
There has been speculation that Canon might export nanolithography equipment to China, but that seems unlikely.
Nanoimprint lithography was invented and patented by Japanese researcher Susumu Fujimori in 1979 while he was working at Nippon Telegraph and Telephone Public Corporation (NTT, Japan’s national telecommunications company). Canon entered the nanoimprint business in 2014 with the acquisition of Molecular Imprints, a spinout from the University of Texas.
Molecular Imprints – now called Canon Nanotechnologies – has been awarded more than 170 patents covering imprint tools, materials, masks, process technology and imprint-specific device designs. Neither the US nor the Japanese government is likely to allow this technology to be sold to China.
On the other hand, Canon sells older KrF and i-line type IC lithography systems – and flat-panel-display lithography systems – to Chinese customers, along with cameras, printers and other products. If it were allowed, Chinese NAND-flash memory maker Yangtze Memory Technologies Corporation (YMTC) might buy its nanolithography systems.
But as things stand now, the most likely second customer appears to be SK Hynix of South Korea, which also makes NAND flash memory. Like Toshiba/Kioxia, SK Hynix has acquired nanolithography test equipment from Canon.
Canon doesn’t make the more advanced ArF DUV (deep ultraviolet) lithography systems that have recently been included in the sanctions imposed on China’s semiconductor industry by the US, the Netherlands and Japan. Nikon does, but runs a distant second to ASML in production capacity and market share. Exports of EUV lithography systems to China were banned in 2019.
Almost as an afterthought, Canon’s press release points out that its nanoimprint lithography equipment can also be used to make meta-lenses (flat lenses etched on silicon) and other optical components. In fact, the primary use of nanoimprint lithography at present is to make optical components. The main competitors in this field are EVG, SUSS MicroTec and Obducat, all of which are European.
EVG’s nanoimprint equipment is used to make optical waveguides, wire grid polarizers and other optical elements used in displays, 3D sensing, biometrics and photonics, with precision down to at least 40nm. According to the company, the lifespan of its master templates is comparable to that of photomasks used in photolithography.
SUSS MicroTec’s micro- and nanoimprint mask aligner equipment is designed for the production of optical elements and MEMS/NEMS (micro- and nano-electro-mechanical systems), high-brightness LEDs (light-emitting diodes), and VCELS (vertical-cavity surface-emitting lasers) used in laser printers, computer mice and fiber optics.
Obducat’s nanoimprint technology is used to make a variety of products including biomedical devices, semiconductor lasers and GaN (gallium nitride) substrates for power electronics.
In China, Suzhou Guangduo Micro Nano Devices (GDNANO) develops and manufactures micro- and nanoimprint equipment for semiconductor, photonics, MEMS and other applications. Founded in 2011, its newest machine is designed for mass production of patterned sapphire substrates for LEDs. GDNANO is not yet a technology leader, but it is a company to be watched.
Canon’s nanoimprint technology threatens ASML’s absolute monopoly on 5nm and smaller process node lithography, but it is not a serious threat to its business now and probably won’t be for at least several more years.
But it does demonstrate that there is more than one way to make semiconductors and suggests that the predictable cycle of ever smaller design rules enabled by the next generation of equipment from a few key suppliers may be starting to break down.
