The Okinawa Institute of Science and Technology (OIST) has announced a revolutionary Extreme Ultraviolet (EUV) lithography technology that transcends the standard limits of semiconductor manufacturing. This cutting-edge design allows for the use of significantly smaller EUV light sources, with power consumption reduced to less than one-tenth of traditional EUV lithography machines. This advancement not only lowers costs but also greatly enhances the reliability and lifespan of the equipment.
In conventional optical systems, such as cameras, telescopes, and traditional ultraviolet lithography, optical elements like apertures and lenses are aligned axially. This method, however, is unsuitable for EUV rays due to their extremely short wavelengths, which are largely absorbed by materials. Instead, EUV light is guided using crescent-shaped mirrors, which unfortunately cause light to deviate from the central axis, compromising optical performance.
The new lithography technology addresses this issue by arranging two axially symmetric mirrors with tiny central apertures in a straight line, achieving the necessary optical properties. Given the high absorption rate of EUV light—where energy diminishes by 40% with each reflection—industry standards typically allow only about 1% of the EUV source energy to reach the wafer through ten mirrors. By limiting the number of reflecting mirrors to just four, the new technology enables more than 10% of the energy to penetrate the wafer, significantly reducing power consumption.
The core projection system of this new EUV lithography technology transfers the light mask image onto the silicon wafer using two mirrors, akin to an astronomical telescope. This configuration is notably simpler than traditional systems, which require at least six mirrors. Achieving this simplicity involved rethinking optical aberration correction theories, with performance validated by optical simulation software to meet advanced semiconductor production requirements. The team has also developed a new illumination optical method called "Double-Line Field," which uses EUV light to illuminate the plane mirror mask from the front without disrupting the optical path.
This seemingly simple solution to a complex problem is truly remarkable. Imagine holding two flashlights and aiming them at a mirror at the same angle; the light from one flashlight would continually shine on the other. In lithography, this would be unacceptable. However, by moving the flashlights outward while maintaining the same angle, the light can reflect properly without colliding with the opposite flashlight’s beam. This ingenious technology, now patented, is poised to deliver significant economic benefits to the global EUV lithography market.
