EUV Optics

Glancing to normal incidence optics for 13.5 nm (EUV)

EUVL is used extensively in high-volume manufacturing of memory and logic integrated circuits. Mo/Si multilayers, optimized for EUV, with protective cap layers of various designs are available from Rigaku for use in collection, beam conditioning pre-reticle for scanners and beam conditioning pre-sample and imaging post-sample for metrology.

Grazing to normal incidence optics for 6.x nm (BEUV)

Beyond EUV (BEUV) is based on current development of new X-ray sources and associated multilayer optics. Today, we offer the highest-performance optics available for BEUV.

Examples of EUV optics

EUV technologies and capabilities

RIT has proven expertise & capability to address any application or design requirement, with customized multilayer designs to meet the unique requirements of the optical system. RIT is a global provider of EUV Collectors, Illumination and Imaging optics with demonstrated world-class results in nearly every class of EUV optics.

Capabilities

Various off-axis coatings
Uniform coating

MoSi performance benchmarks

In order for EUV multilayers to be of practical use, they must have ultra-low roughness on the nanometer scale, measurable only with the use of an atomic force microscope (AFM). A typical Molybdenum-Silicon (MoSi) multilayer will contain 80 individual thin layers of 2.5 nm – 4 nm thickness, where the roughness of each interface must be less than 0.2 nm. Putting this in perspective, the radius of an individual Mo atom is 0.14 nm!

Rigaku repeatedly demonstrates capability to produce world-class EUV multilayer performance. Some of our achievements and benchmarks are shown below.

Champion MoSi multilayer

With the use of optimized interfacial-stabilization layers, the champion performance for Rigaku with MoSi is 69.2% peak reflectivity for normal incidence. Compared to Rigaku’s routine performance of 66.5% for 40-layer ML and 67.5% for 60-period ML, this champion performance would produce up to +60% more total power in a 12-optic lithography system.

High-temperature Mo/X/Si multilayers

With the use of interface-stabilization layers optimized for temperature stability, Rigaku produces EUV multilayers with excellent temperature stability, capable of retaining high reflectivity and minimal peak shift when subjected to vacuum annealing at high temperatures.

EUV high-selectivity multilayers

In addition to standard MoSi multilayers with ~4% bandpass, Rigaku developed multilayers for specialized applications requiring high-selectivity. The multilayer below narrows the bandpass to 1.1% using SiC and Si layers.

EUV success stories

Example 1: Illumination system

In 2013, Rigaku completed a 5-optic illumination system, later linked to the 2016 delivery of a >400mm diameter collector. In addition to providing all multilayers, Rigaku was instrumental in the optical design analysis using such tools as Zemax, to optimize the optical scheme, optic shapes and multilayer designs.

The collector optic was a focusing ellipsoid of revolution, and had a surface grating that would reject unwanted infra-red (IR) radiation with minimal impact to the reflection of 13.5 nm EUV source. *Example 1, courtesy of “The Recent Study of Resist Outgassing in the Hydrogen Environment,” Eishi Shiobara et. al., 2016 International Symposium on Extreme Ultraviolet Lithography, International Sematech, Hiroshima, Japan, 2016.

The collector delivered the EUV light to a trio of paraboloid-shaped optics which created two separate beams of designed illumination, redirected via a pair of EUV 45° incidence flats.

Example 2: Illumination + imaging system

In 2012, Rigaku completed a multi-optic system for high-precision imaging. The first two optics were precision ellipsoid surfaces, with Rigaku-designed kinematic mounting systems, that delivered light into a Schwarzschild imaging system, a pair of aspherical optics. These illumination optics required complex 2-dimensional multilayer gradients to efficiently deliver EUV photons.

The imaging optics were deposited ultra-precisely with radial symmetry to minimize distortions to the near-perfect surface of the optics. Multilayer contributions to figure error were below 200 picometers. *Example 2, courtesy of “Defect Review Capability Enhancement for Actinic Blank Inspection Tool,” Kiwamu Takehisa et. al., 2016 International Symposium on Extreme Ultraviolet Lithography, International Sematech, Hiroshima, Japan, 2016.

Example 3: Illumination + imaging system

In 2005, Rigaku completed a multioptic Reticle Imaging System, that was composed of four illumination optics (C1-C4) and a pair of imaging optics (M1-M2). Precise and complex multilayer gradients were required to ensure uniform illumination, as well as ultra-low added distortions to the imaging field. *Example 3, image courtesy of private communications, reference material of 2006 EUVL Symposium, Proc. SPIE 6151, Emerging Lithographic Technologies X, (March 24, 2006)