Semiconductors
Extreme Ultraviolet Lithography (EUV): The Physics of Patterning Chips with 13.5 nm Light
Extreme ultraviolet lithography is the photolithography technique used to print the smallest features on advanced semiconductor chips. It exposes wafers with light at a wavelength of 13.5 nm, generated by vaporizing tin droplets into a plasma with a high-power laser. Because no material is transparent at that wavelength, the entire optical system is built from reflective multilayer mirrors operating in a vacuum rather than glass lenses. EUV became necessary below the 7 nm node, where older 193 nm light required ever more complex multi-patterning. ASML is the only company that builds production EUV machines.
ASML: The Dutch Monopoly on EUV Lithography Machines
ASML is the only company in the world that manufactures working extreme ultraviolet lithography machines at production scale, making it the single chokepoint for leading-edge chip manufacturing. Each high-NA EUV system costs roughly 350 million euros and is required to fabricate chips at 3nm, 2nm, and smaller nodes.
Gallium Nitride (GaN): The Wide-Bandgap Semiconductor Behind Blue LEDs and Fast Chargers
{{Gallium nitride}} (GaN) is a {{wide-bandgap semiconductor}} (~3.4 eV direct bandgap) that enabled the {{blue LED}} and now powers compact fast chargers and high-frequency {{RF}} amplifiers. Its high electron mobility and breakdown field let GaN devices switch faster and run hotter than {{silicon}}.
Wide-Bandgap Semiconductors: The Third-Generation Materials for Power and RF
{{Wide-bandgap semiconductors}} have bandgaps above ~2 eV (versus {{silicon}}'s ~1.1 eV), letting them operate at higher voltages, temperatures, and frequencies. Examples include {{silicon carbide}}, {{gallium nitride}}, diamond, and gallium oxide; SiC and GaN dominate today's power and RF electronics.
Silicon Carbide (SiC): The Wide-Bandgap Semiconductor for Power Electronics
{{Silicon carbide}} (SiC) is a {{wide-bandgap semiconductor}} (about 3.2 eV in the common 4H polytype) prized for power electronics because it tolerates higher voltages, temperatures, and switching speeds than {{silicon}}. It is the workhorse of EV traction inverters and exists naturally as the rare mineral {{moissanite}}.
EUV Mirrors: The Smoothest Objects Ever Manufactured
Because 13.5nm extreme ultraviolet light is absorbed by virtually all materials including glass, ASML's EUV lithography machines use reflective optics built from 40-80 alternating molybdenum-silicon layers that achieve roughly 70% reflectivity via Bragg interference. Surface roughness is specified at 2.3 silicon atoms average bump height, making them the smoothest macroscopic objects ever made.
Graphene: The Single-Atom-Thick Carbon Sheet With No Bandgap
{{Graphene}} is a single layer of carbon atoms in a honeycomb lattice, isolated in 2004 by Geim and Novoselov (2010 Nobel Prize). It has extraordinarily high carrier mobility, strength, and thermal conductivity, but as a zero-{{bandgap}} semimetal it cannot be switched fully off, limiting its use in digital logic.
EUV Light Source: How ASML Makes 13.5nm Light from Tin Plasma
ASML's EUV lithography machines generate 13.5-nanometer extreme ultraviolet light by vaporizing molten tin droplets with a 20,000-watt CO2 laser, producing plasma at roughly 220,000 Kelvin — about 40 times hotter than the surface of the Sun. The system hits 50,000 droplets per second with three laser pulses each, never missing.
Transition Metal Dichalcogenides (TMDs): Atomically Thin 2D Semiconductors
{{Transition metal dichalcogenides}} (TMDs) are 2D materials of the form MX2 (e.g., MoS2, WSe2) just a few atoms thick. Unlike {{graphene}}, monolayer TMDs have a real, often direct {{bandgap}} (~1.5-1.9 eV), making them strong candidates for transistors that scale past {{silicon}}'s size limits.
No Single Successor to Silicon: The Heterogeneous Future of Chip Materials
There is no anointed replacement for {{silicon}} as a chip material. Instead, several materials are advancing for different niches: {{silicon carbide}} and {{gallium nitride}} are already winning in power electronics, while {{graphene}} and {{transition metal dichalcogenides}} are research bets for logic and continued miniaturization. The likely outcome is heterogeneous integration rather than wholesale replacement.
EUV Origin Story: From a 1986 Japanese Rejection to ASML's 2015 Korea Demo
Extreme ultraviolet lithography took three decades from first demonstration to commercial production, surviving a 1996 US government funding cut, a 250 million dollar industry rescue by Intel, AMD, and Motorola, and a 5.4 billion dollar customer co-investment that bought equity in ASML to keep R&D alive through the low point of 2012-2013.