From Sand to Silicon - Rock, Furnace, Wafer, Fab

3.0 What this chapter gives you#

1. You will be able to say where the silicon in a chip comes from, naming the rock and the furnace.
2. You will be able to explain why 99 percent pure is useless here.
3. You will be able to describe how a single crystal is grown, and why the whole ingot must be one unbroken lattice.
4. You will be able to walk from a 265 kilogram crystal to a 775 micrometer polished wafer, naming every cut.
5. You will be able to explain photolithography, and why shorter wavelength light gives smaller features.
6. You will be able to explain how extreme ultraviolet light is made from a falling tin droplet.
7. You will be able to explain doping, deposition, the copper wiring stack, testing, dicing and packaging.
8. You will be able to say honestly what “3 nm” means in 2026.
9. You will be able to explain why leading-edge chip making sits in a handful of buildings on Earth.

3.1 Where silicon comes from#

PLAIN3.1.1 in simple words#

1. Silicon is a chemical element, a basic building block of matter, like iron or oxygen.
2. About 28 percent of the mass of the Earth’s rocky shell is silicon. Only oxygen is more common.
3. But you will never dig up a lump of pure silicon anywhere on Earth.
4. Every silicon atom in the ground is already bound to oxygen, tightly.
5. Silicon plus oxygen makes silica. Silica plus metals makes the silicate minerals, which is most rock.
6. So the job is not to find silicon. The job is to tear the oxygen off it.
7. The purest common form of silica is the mineral quartz. That is what we mine.

PLAIN3.1.2 a picture in your head#

1. Think of silicon as a person already holding hands with two oxygen partners, and refusing to let go.
2. Rock is that crowd, frozen solid. No silicon atom stands alone.
3. Quartz is the tidiest part of the crowd. Beach sand is a messier part, with shell and iron mixed through.
4. Where this comparison breaks: atoms do not want anything. The real fact is that the silicon-oxygen bond is strong, near 800 kilojoules per mole.

PLAIN3.1.3 a worked example#

1. Take a kilogram of average continental crust and sort it by mass.

2. So that kilogram holds roughly 277 grams of silicon, and none of it is loose.
3. Typical beach sand runs 90 to 99 percent silica. Chip-grade quartzite runs above 99.5 percent.
4. That gap of a few percent is why we mine specific rock instead of a beach.

PLAIN3.1.4 what is really happening inside#

1. Silica is silicon dioxide: one silicon atom joined to two oxygen atoms, in an endless solid network.
2. In quartz that network is a regular crystal with little else mixed in.
3. In granite and clay the same units combine with sodium, potassium, aluminum, iron and magnesium. Those are silicates.
4. Iron is the enemy. Iron atoms inside silicon later act as traps that ruin the electrical behaviour we want.
5. So mining is really sorting. We look for rock where nature already sorted for us.
6. The ore must also be lumpy, because the furnace needs gas to flow up through the charge. Powder would choke it.

TECHNICAL3.1.5 the engineer’s version#

1. Silicon, atomic number 14, is the second most abundant crustal element at about 27.7 percent by mass, after oxygen.
2. It does not occur natively, only as silicon dioxide and as the silicate mineral families.
3. Feedstock is lump quartz or quartzite, sized roughly 10 to 100 millimetres, specified above 99 percent silicon dioxide.
4. Limits are set on iron, aluminum, calcium, titanium, boron and phosphorus.
5. Boron and phosphorus matter most. They are dopants, and they resist later chemical removal.
6. Producing regions include Norway, Spain, Turkey, Brazil, China, Russia and the United States.

7. The honest version: Spruce Pine quartz, in North Carolina, is famous, but it is not usually the feedstock that becomes the chip.
8. It is mainly melted into the fused-quartz crucibles used later in crystal growth. Do not repeat the claim that chips start as Spruce Pine sand.

WORDS3.1.6 remember these#

1. Silica — silicon joined to oxygen — silicon dioxide, SiO2, the network solid forming quartz.
2. Silicate — silica with metals mixed in — a mineral family built on silicon-oxygen tetrahedra.
3. Quartz — the clean crystal form of silica — crystalline SiO2, the preferred carbothermic feedstock.
4. Quartzite — hard rock made mostly of quartz — metamorphosed sandstone supplied as graded lump ore.

3.2 First refining: the submerged-arc furnace#

PLAIN3.2.1 in simple words#

1. We have crushed quartz. Now we pull the oxygen off, using carbon and a very large amount of heat.
2. Carbon takes oxygen readily. Hot enough, it strips oxygen from silicon and leaves as carbon monoxide gas.
3. The machine is a submerged-arc furnace: a huge lined bowl with thick carbon rods pushed into the charge.
4. Electricity arcs through the material and heats it to around 1,900 degrees Celsius, hotter than lava.
5. Molten silicon collects at the bottom and is drained through a tap hole.
6. What comes out is metallurgical-grade silicon, about 98 to 99.5 percent pure.
7. That sounds excellent. For a chip it is hopelessly dirty.

PLAIN3.2.2 a picture in your head#

1. Picture a stone pot several metres across, filled with gravel, coal and wood chips.
2. Three carbon rods, each as thick as a tree trunk, are pushed down into the mixture.
3. Where the current jumps it makes an arc, and that arc sits buried inside the charge. That is “submerged arc”.
4. Where this comparison breaks: nothing is cooking. This is a chemical reduction reactor, with reactions stacked in temperature zones.

PLAIN3.2.3 a worked example#

1. Here is the overall reaction, written the simple way.

SiO2   +   2 C    ->    Si     +   2 CO
quartz     carbon       silicon    carbon monoxide

2. Silicon dioxide is near 60 grams per mole; silicon is near 28. So 60 kilograms of quartz gives at most 28 kilograms of silicon.
3. Real furnaces recover roughly 80 to 90 percent. Some silicon escapes as silicon monoxide gas.
4. Energy cost is roughly 11 to 13 kilowatt hours per kilogram of product.
5. A large furnace runs at 20 to 40 megawatts, continuously, for years. It is never switched off if that can be avoided.

PLAIN3.2.4 what is really happening inside#

1. The charge is quartz plus carbon sources: coal, charcoal, petroleum coke and wood chips.
2. Wood chips are added for a physical reason. They keep the charge porous so gas can escape.
3. In the hot lower zone, around the arc, silicon dioxide is reduced to liquid silicon.
4. In the cooler upper zone, escaping silicon monoxide reacts with carbon to form silicon carbide, which sinks and reacts further.
5. That recycling is why the process works. Without it, far too much silicon would leave as gas.
6. The honest version: the tidy equation is a summary, not a description. It is a coupled set of reactions across a temperature gradient.
7. Impurities stay with the metal. Iron, aluminum and calcium dissolve in the liquid silicon.

TECHNICAL3.2.5 the engineer’s version#

1. This is carbothermic reduction of silicon dioxide in a three-phase submerged-arc furnace, with Soderberg or prebaked graphite electrodes.
2. Arc temperature is around 1,900 to 2,000 degrees Celsius. Silicon melts at 1,414 degrees Celsius, so the product is liquid.
3. The dominant intermediate is silicon carbide.
4. Output is metallurgical-grade silicon, written MG-Si, at 98 to 99.5 percent.
5. Ladle refining with oxygen and slag additions removes some aluminum and calcium. It does not remove boron or phosphorus.

6. World output is millions of tonnes per year. Only a small share reaches semiconductor purity.
7. Silica fume, the dust caught from the offgas, is sold as a concrete additive. It is a revenue stream, not waste.

WORDS3.2.6 remember these#

1. Carbothermic reduction — using carbon and heat to strip oxygen — carbon as the reducing agent at high temperature.
2. Submerged-arc furnace — a furnace whose arc is buried in the material — a three-phase electrode furnace.
3. Metallurgical-grade silicon — first-pass silicon metal — MG-Si at 98 to 99.5 percent, the input to chemical purification.
4. Silica fume — fine dust caught from the exhaust — amorphous silicon dioxide sold as a concrete admixture.

3.3 Getting to nine nines#

PLAIN3.3.1 in simple words#

1. Silicon at 99 percent has one foreign atom in every hundred.
2. For a chip we need roughly one foreign atom in every billion, and for some impurities far fewer.
3. You cannot get there by melting and skimming. You need chemistry.
4. The trick is to turn solid silicon into a liquid chemical, clean it, then turn it back into solid silicon.
5. The chemical is trichlorosilane. It boils just under 32 degrees Celsius, so we can distil it.
6. Then we pipe the cleaned vapour over hot silicon rods, and silicon grows back onto them, atom by atom.
7. The result is polysilicon, at nine nines purity or better: 99.9999999 percent.

PLAIN3.3.2 a picture in your head#

1. Imagine a bucket of mixed salt and sand, and you want pure salt.
2. You dissolve what you can, filter out what will not dissolve, then boil the water away. The salt comes back clean.
3. Making trichlorosilane is the dissolving step. Distillation is the filtering step. Growing rods is the boiling-dry step.
4. Where this comparison breaks: salt water separates in one pass. Nine nines needs columns in series, some tens of metres tall, plus days of deposition.

PLAIN3.3.3 a worked example#

1. Purity numbers are hard to feel, so convert them into countable things.

2. That stack of 100 billion cards would stand about 15,000 kilometres tall, with exactly one wrong card in it.
3. Now the humbling part. A cubic centimetre of silicon holds about 5 times 10 to the power 22 atoms.
4. So even at nine nines, that cubic centimetre still holds around 50 thousand billion foreign atoms.
5. Nine nines is not “no impurities”. It is “impurities below the level where they change the behaviour we care about”.

PLAIN3.3.4 what is really happening inside#

1. Step one. Ground metallurgical silicon meets hydrogen chloride gas at around 300 degrees Celsius in a fluidized bed.
2. Out comes trichlorosilane. Impurities come along as their own chlorides, with their own boiling points.
3. Step two. The mixture goes through distillation columns. Boron and phosphorus compounds are hardest to strip and set the final purity.
4. Step three. The cleaned liquid is vaporized, mixed with hydrogen, and fed into a sealed bell-jar reactor.
5. Inside stand thin silicon filaments heated to about 1,100 degrees Celsius. The gas breaks down there, silicon sticks, hydrogen chloride leaves.
6. Over two to four days the filaments grow into grey rods 15 to 20 centimetres across, which are broken into chunks.
7. This is polysilicon: extremely pure, but made of many small crystals pointing in random directions. We fix that next.

TECHNICAL3.3.5 the engineer’s version#

1. The dominant route is the Siemens process, developed by Siemens in Germany in the late 1950s and still the workhorse in 2026.
2. Hydrochlorination runs at roughly 300 to 350 degrees Celsius. Trichlorosilane boils at 31.8 degrees Celsius, making distillation practical.
3. Deposition is chemical vapour deposition onto filaments at about 1,100 to 1,150 degrees Celsius inside a water-cooled bell jar.
4. Conversion per pass is low, near 20 percent, so unreacted gas and silicon tetrachloride are recycled.

5. The main alternative is the fluidized bed reactor route, fed with monosilane, giving granular polysilicon at roughly one tenth of the heating electricity.
6. The honest version: “eleven nines” is a bulk metallic-impurity figure, not a statement about every element.
7. Dopants such as boron and phosphorus are specified separately, in parts per billion atomic or as resistivity. Carbon and oxygen are separate again.
8. Metrology includes glow discharge mass spectrometry, inductively coupled plasma mass spectrometry, and photoluminescence.

WORDS3.3.6 remember these#

1. Trichlorosilane — the liquid we clean instead of the metal — SiHCl3, boiling point 31.8 degrees Celsius.
2. Siemens process — growing pure silicon back onto hot rods — CVD from trichlorosilane and hydrogen at about 1,100 degrees Celsius.
3. Polysilicon — very pure silicon made of many small crystals — electronic-grade polycrystalline silicon, the feedstock for crystal growth.
4. Nine nines — 99.9999999 percent pure — 9N, one foreign atom per billion by the stated metric.

3.4 Growing a single crystal#

PLAIN3.4.1 in simple words#

1. Our polysilicon chunks are pure, but their internal arrangement is a mess.
2. They are many small crystals at random angles. Where two meet there is a seam called a grain boundary.
3. Electrons behave badly at those seams. A chip needs one repeating pattern across the whole piece, with no seams.
4. So we melt the polysilicon completely and grow it back as one single crystal.
5. We dip a small perfect seed crystal into the melt and slowly pull it upward while turning it.
6. Liquid silicon freezes onto the seed and copies its arrangement exactly.
7. Keep pulling for a day or more and you get a cylinder of one crystal, called a boule or ingot.
8. A 300 millimetre boule is about 2 metres long and weighs about 265 kilograms.

PLAIN3.4.2 a picture in your head#

1. Think of pulling hot toffee slowly out of a pan so it stretches into a smooth rod instead of breaking.
2. Now add one rule: it can only harden by copying the pattern already above it. The seed is that template.
3. Pull too fast and the pattern breaks. Pull too slow and the rod grows fat. Spinning keeps the heat even all round.
4. Where this comparison breaks: toffee just cools. Each silicon atom must find one site in a repeating three-dimensional lattice. And the crucible slowly dissolves into the melt.

PLAIN3.4.3 a worked example#

1. Here is a full run for a 300 millimetre crystal.

Charge polysilicon into crucible   about 250 to 450 kg
Melt down under argon              melts at 1414 deg C
Dip the seed crystal               seed a few mm across
Neck: pull thin and fast           neck about 3 mm wide
Grow the crown, widen out          out to 300 mm across
Grow the body                      about 2 m of cylinder
Taper the tail and lift clear      whole run 1 to 3 days

2. Pull rate through the body is around 0.5 to 1.5 millimetres per minute.
3. Crucible and crystal rotate in opposite directions, a few turns per minute each.
4. The neck stage looks wasteful but is essential. Pulling thin and fast forces line defects out to the surface, where they vanish.
5. That trick came from William Dash at General Electric around 1958. It is why modern crystals can be dislocation-free.

PLAIN3.4.4 what is really happening inside#

1. The polysilicon sits in a fused-quartz crucible inside a graphite support, under argon so no air gets in.
2. Heaters bring everything above 1,414 degrees Celsius, the melting point of silicon.
3. A measured amount of boron or phosphorus goes into the melt now. This is the first doping step.
4. As the seed rises, liquid at the interface freezes, and each atom locks into the position dictated by the seed.
5. The seed’s lattice direction therefore sets the direction of the whole boule. That is crystal orientation.
6. Impurities prefer to stay liquid, so the crystal purifies itself as it grows. That is segregation, and it leaves the tail dirtier than the head.
7. The quartz crucible slowly dissolves, so oxygen enters the melt and ends up in the crystal. This is unavoidable here.

TECHNICAL3.4.5 the engineer’s version#

1. The method is the Czochralski process, named for Jan Czochralski, the Polish chemist who described the pulling technique in 1916.
2. It was adapted to semiconductors at Bell Telephone Laboratories by Gordon Teal and John Little around 1950.
3. Orientation is given by Miller indices. The two common wafer orientations are (100) and (111).
4. (100) dominates for modern CMOS logic, because the silicon to silicon-dioxide interface has lower trapped charge on that plane.
5. Resistivity is set by melt doping: boron gives p-type; phosphorus, arsenic or antimony give n-type.
6. Interstitial oxygen lands near 10 to 20 parts per million atomic. It gives internal gettering, which traps metals away from the device region.

7. The alternative is float-zone growth. A radio-frequency coil melts a narrow band passed along a rod, with no crucible touching the melt.
8. Float-zone silicon has far lower oxygen and much higher resistivity, so it suits power devices, radiation detectors and some radio-frequency parts.
9. It is limited to about 200 millimetres and costs more, so almost all logic and memory wafers are Czochralski.
10. The honest version: a Czochralski crystal is dislocation-free, not defect free. Point defects, vacancy clusters and dissolved oxygen remain.

WORDS3.4.6 remember these#

1. Single crystal — one unbroken repeating pattern of atoms — a monocrystalline solid with no grain boundaries.
2. Grain boundary — the seam where two crystals meet — a planar defect that scatters carriers and traps charge.
3. Boule — the big grown cylinder — the as-grown single-crystal ingot before machining.
4. Czochralski — the dip-and-pull growth method — crucible-based melt pulling, the dominant industrial route.
5. Float zone — crucible-free growth by a moving molten band — FZ silicon, low oxygen, high resistivity, limited diameter.

3.5 From boule to wafer#

PLAIN3.5.1 in simple words#

1. We have a two-metre crystal cylinder. Chips are built on thin flat slices of it.
2. First the cone-shaped ends are cut off and thrown back into the melt pot.
3. Then the cylinder is ground on the outside to exactly the right diameter all the way along.
4. A small notch is ground into the side. It tells every later machine which way the crystal pattern faces.
5. Then the cylinder is sliced, using one very long wire coated with cutting grit.
6. Sawing leaves slices rough and damaged, so they are ground flat, etched in acid, and polished.
7. The result is a wafer: a disc about three quarters of a millimetre thick, with a mirror surface.

PLAIN3.5.2 a picture in your head#

1. Think of a very long, expensive salami sliced into perfect discs by a machine that never wobbles.
2. Except the slicer is not a blade. It is one wire, hundreds of kilometres long, wound across grooved rollers.
3. The wire runs at speed carrying hard particles, cutting the whole ingot into hundreds of slices in one pass.
4. Where this comparison breaks: salami only needs to look right. A wafer must be flat to a fraction of a wavelength of light, or the printing step goes out of focus.

PLAIN3.5.3 a worked example#

1. Follow one 300 millimetre boule through the shop.

Boule 2 m, 265 kg
  -> crop the ends       lose about 10 to 20 pct
  -> grind to 300.0 mm   lose a few mm of radius
  -> grind the notch     one small notch on the edge
  -> wire saw            about 900 to 1200 wafers
  -> lap and edge-round  remove the saw damage
  -> acid etch           remove more damage
  -> CMP one side        mirror finish
  -> clean and pack      sealed cassettes

2. Slicing loses material as kerf, the width of the cut. Diamond wire kerf is roughly 100 to 150 micrometers.
3. A finished 300 millimetre wafer is 775 micrometers thick, plus or minus about 25. That is standardized, not a guess.
4. So each wafer plus kerf uses close to 0.9 millimetres of boule, giving around one thousand wafers from 2 metres.
5. A blank polished 300 millimetre prime wafer sells for very roughly 100 to 150 US dollars in volume.

PLAIN3.5.4 what is really happening inside#

1. Cropping removes the crown and tail, where diameter is wrong and impurity levels are off.
2. The notch is ground after an X-ray measurement finds the true crystal direction.
3. Older small wafers used a straight flat on the edge. Modern 200 and 300 millimetre wafers use a notch, which wastes less area.
4. In wire sawing the wire does not cut. The abrasive does. Sawing leaves a damaged layer tens of micrometers deep, full of microcracks.
5. Lapping presses wafers between plates with slurry to make both faces parallel and flat. Edge rounding stops chipping and particle shedding.
6. Acid etching removes the crushed layer. Chemical-mechanical polishing then finishes one face with a soft pad and an alkaline silica slurry.
7. Final cleaning ends with drying in filtered air. From here the wafer never touches ordinary air again.

TECHNICAL3.5.5 the engineer’s version#

1. Wafer geometry is set by SEMI standards: diameter, thickness, flatness, edge profile and notch dimensions.

2. Thickness rises with diameter for stiffness. A thin 300 millimetre wafer would sag and crack under its own weight.
3. Going from 200 to 300 millimetres multiplies usable area by about 2.25 for less than 2.25 times the cost. That is the case for larger wafers.
4. The 450 millimetre transition stalled. The Global 450 Consortium, based in Albany, New York, effectively collapsed around 2016 and 2017.
5. Reported reasons: huge tool redevelopment cost, EUV absorbing the industry’s capital, and reluctance to fund a change helping mainly the largest players.
6. As of 2026 there is no credible 450 millimetre roadmap.
7. Processed wafer prices at leading nodes, reported by analysts in early 2026. These are negotiated and vary by customer.

8. The honest version: the raw silicon disc is a rounding error. At the 2 nanometre class it is well under 1 percent of the finished wafer price.
9. When people say “sand is cheap, so chips should be cheap”, this table is the answer. The material is cheap. The processing is not.

WORDS3.5.6 remember these#

1. Kerf — the material lost to the cut — the saw slot width, roughly 100 to 150 micrometers with diamond wire.
2. Notch — the alignment mark on the wafer edge — a SEMI-specified notch replacing the older primary flat.
3. CMP — polishing with chemistry and rubbing together — chemical-mechanical planarization, using a pad and reactive slurry.
4. Prime wafer — the best grade sold — a polished wafer meeting full flatness, particle and defect specification.

3.6 The cleanroom#

PLAIN3.6.1 in simple words#

1. The features on a modern chip are far smaller than a speck of dust.
2. One particle in the wrong place can short two wires or block a printing step, and kill that chip.
3. So chip factories are built inside rooms far cleaner than an operating theatre.
4. Air is pushed down through ceiling filters, constantly, and pulled out through the floor.
5. The dirtiest thing in the room is the human. People wear sealed suits, called bunny suits, that keep skin flakes and breath in.
6. The building must be still, because even small vibrations blur the printing step.
7. The rinse water is purer than drinking water by an enormous margin.
8. All of this is why a leading-edge fab costs billions before it makes a single chip.

PLAIN3.6.2 a picture in your head#

1. Picture an operating theatre, made a hundred times cleaner, inside a concrete box the size of several football pitches.
2. The whole ceiling is a filter. Air falls straight down like an invisible waterfall, sweeping particles to the floor.
3. Wafers do not ride through the open room. They travel in sealed pods on overhead rails and dock onto machines.
4. Where this comparison breaks: a theatre worries about living germs. A fab does not care whether a particle is alive. It cares about size.

PLAIN3.6.3 a worked example#

1. Suppose one chip is 1 square centimetre, and the process leaves 0.1 killer defects per square centimetre.
2. A simple model gives a good fraction of e to the power of minus 0.1, about 0.90. So 90 percent survive.
3. Now make the chip ten times bigger, 10 square centimetres, like a large graphics processor.
4. The same defect density gives e to the power of minus 1, about 0.37. Only 37 percent survive.
5. Same factory, same wafer. Bigger chips are punished brutally, which drives the move to chiplets in section 3.10.

PLAIN3.6.4 what is really happening inside#

1. Cleanliness is measured by counting particles in a fixed volume of air, at a fixed particle size.
2. The cleanest areas allow about ten particles of 0.1 micrometer or larger in a whole cubic metre of air.
3. To hold that, room air is replaced hundreds of times per hour, needing enormous fan power running permanently.
4. Not all of the fab is equally clean. The tightest classes apply where wafers are exposed, especially at the lithography tools.
5. Water is purified until it barely conducts, then deoxygenated and filtered again just before use. A big fab uses millions of litres a day.
6. Vibration matters because the printing tool must hold alignment to a few nanometres while a heavy stage moves fast.
7. So the lithography bay sits on an isolated slab with active dampers, and the fab is not built next to a railway line.

TECHNICAL3.6.5 the engineer’s version#

1. Air cleanliness is classified by ISO 14644-1. The older United States standard, Federal Standard 209E, was withdrawn in 2001.

2. ISO 3 corresponds roughly to the old Class 1, and ISO 5 to the old Class 100.
3. Modern practice is a mini-environment strategy. The bay runs at ISO 5 or 6 while the wafer sees ISO 1 inside a sealed pod and inside the tool.
4. Wafers travel in a Front Opening Unified Pod, a SEMI-standard carrier, moved by an overhead hoist transport system.
5. Ultrapure water is specified at 18.2 megaohm-centimetre at 25 degrees Celsius, the theoretical maximum for pure water.
6. Molecular contamination is controlled too. Ammonia poisons chemically amplified photoresist, so lithography bays use chemical filtration.
7. Vibration is specified against generic vibration criteria curves. Advanced lithography demands VC-E or better, near 3 micrometres per second RMS.
8. TSMC stated in 2025 and 2026 that a 2 nanometre fab module of about 20,000 wafer starts per month costs roughly 25 to 35 billion US dollars.
9. TSMC guided 2026 capital spending to roughly 60 to 64 billion US dollars. Most of that is tools; a single EUV scanner can exceed 200 million dollars.
10. Standard, convention or implementation detail: ISO 14644-1 is a standard, the bunny suit is a convention, and each bay’s class is an implementation detail of that fab.

WORDS3.6.6 remember these#

1. Cleanroom — a room with almost no dust — a controlled environment classified by ISO 14644-1 particle limits.
2. Bunny suit — the full-body coverall — a cleanroom garment containing human-generated particles and fibres.
3. FOUP — the sealed wafer box — Front Opening Unified Pod, the standard 300 millimetre carrier.
4. Ultrapure water — water with nothing else in it — UPW at 18.2 megaohm-centimetre at 25 degrees Celsius.
5. Defect density — how many killer flaws per area — D0 in defects per square centimetre, the main input to yield models.

3.7 Photolithography, the heart of it#

PLAIN3.7.1 in simple words#

1. A chip is a stack of patterned layers. Photolithography puts the pattern on each layer.
2. It is printing with light, and it is the most important step in the factory.
3. First we coat the wafer with a liquid that hardens into a thin film and reacts to light. That is photoresist.
4. We spin the wafer very fast so the liquid spreads into an even layer, much thinner than a hair.
5. Then we shine light through a patterned plate, called a mask or reticle, onto the resist.
6. Where light lands, the resist changes chemically. A developer washes away either the lit parts or the unlit parts.
7. We etch through the holes left behind, then strip the remaining resist off.
8. That is one layer. A modern chip repeats this cycle, with different masks, many dozens of times.

PLAIN3.7.2 a picture in your head#

1. Think of spray painting a wall through a cardboard stencil. The mask is the stencil; the resist records where the spray hit.
2. Now change two things. The stencil is four times bigger than the pattern you want, and a lens shrinks the image on the way down.
3. And the stencil covers only one small rectangle. The machine prints it, steps sideways, prints again, and repeats across the wafer.
4. That is why the tool is a stepper, or a scanner when it sweeps rather than flashes.
5. Where this comparison breaks: paint stays where it lands. Photoresist never becomes part of the chip. It is destroyed and removed on every layer.

PLAIN3.7.3 a worked example#

1. Here is one complete layer cycle, in order.

1  clean and prime      make surface accept resist
2  spin coat resist     3000 rpm, film 30 to 200 nm
3  soft bake            drive off solvent
4  align to previous    match marks already on wafer
5  expose               light through the reticle
6  post-exposure bake   drive the resist chemistry
7  develop              wash away the soluble parts
8  inspect and measure  check width and overlay
9  etch                 cut into the layer below
10 strip resist         remove the mask and clean

2. Now the print-and-repeat step. A standard exposure field is 26 by 33 millimetres, which is 858 square millimetres.
3. A 300 millimetre wafer is about 70,700 square millimetres, so the machine prints roughly 80 fields to cover one wafer.
4. If each field holds four dies of about 200 square millimetres, one wafer carries about 320 dies for that layer.
5. Then it does the whole thing again for the next layer. And again.

PLAIN3.7.4 what is really happening inside#

1. The resist is not a simple dye. In modern deep ultraviolet resists, light creates a small amount of acid inside the film.
2. The bake after exposure lets that acid move and trigger a chain reaction, changing the solubility of the polymer around it.
3. That amplification is why modest light flips a whole film. It is also why stray ammonia in the air ruins the pattern.
4. Alignment is separate and just as hard. Each new layer must line up with the layers already there, to a few nanometres.
5. The machine reads marks already on the wafer and adjusts stage position, rotation and scale before printing. The error left over is overlay.
6. Etching transfers the pattern downward. Wet etching uses liquids and eats sideways as well as down.
7. Dry etching uses a plasma, an electrically excited gas, and cuts almost straight down. That is why small features need it.

TECHNICAL3.7.5 the engineer’s version#

1. Resolution follows the Rayleigh criterion.

CD  = k1 * wavelength / NA
DOF = k2 * wavelength / (NA * NA)

CD  = smallest printable half-pitch
NA  = numerical aperture of the lens
k1  = process factor, hard physical floor at 0.25
DOF = depth of focus, the focus error allowed

2. Three levers exist: shorter wavelength, higher numerical aperture, lower k1.
3. Single exposure cannot go below k1 of 0.25. That physical limit is the reason multi-patterning exists.
4. Note the second formula. Numerical aperture costs depth of focus quadratically, which is why wafer flatness is specified so tightly.
5. Reticles are typically 4x reduction, so 60 nanometres on the mask prints at 15 nanometres on the wafer.
6. Optical proximity correction distorts the mask shapes so the printed result is correct. Sub-resolution assist features help their neighbours print.
7. The honest version: the mask is not a picture of the chip. It is the computed input that yields the chip after diffraction.
8. History: the first commercial wafer stepper was the GCA DSW4800, introduced in 1978. Step-and-scan replaced steppers at advanced nodes in the 1990s.
9. A leading-node mask set is commonly quoted at 10 to 30 million US dollars. That is the main barrier to low-volume advanced chips.

WORDS3.7.6 remember these#

1. Photoresist — light-sensitive coating — a polymer film whose solubility changes on exposure, via a photoacid generator.
2. Reticle — the patterned plate — a quartz plate with an absorber pattern, imaged at 4x reduction onto the wafer.
3. Stepper and scanner — print-and-repeat machines — step-and-repeat or step-and-scan exposure tools working field by field.
4. Numerical aperture — how widely the lens gathers light — NA, appearing in the Rayleigh resolution and depth of focus equations.
5. Overlay — how well layers line up — registration error between a printed layer and the layers beneath it.
6. OPC — deliberately distorting the mask — optical proximity correction, a computational step applied before mask writing.

3.8 The light#

PLAIN3.8.1 in simple words#

1. The smallest thing you can print depends on the wavelength of your light. Shorter waves draw finer lines.
2. Chip making has therefore been a long march toward shorter wavelengths.
3. It started with mercury lamps giving ultraviolet light at 436 and then 365 nanometres.
4. Then came gas lasers at 248 nanometres, then 193 nanometres. These are deep ultraviolet.
5. Progress stalled at 193, so engineers filled the gap between lens and wafer with water.
6. Water bends light more than air, which shrinks the effective wavelength in the gap. That is immersion lithography.
7. When that ran out, they printed one layer more than once with offset patterns. That is multi-patterning.
8. Finally came extreme ultraviolet at 13.5 nanometres, fourteen times shorter than 193.

PLAIN3.8.2 a picture in your head#

1. Imagine drawing with a marker pen. A thick pen cannot draw thin lines, no matter how steady your hand.
2. Wavelength is the thickness of the pen tip. To draw finer, you need a finer tip.
3. Immersion is like drawing underwater, where the ink spreads less. You get a finer line from the same pen.
4. Multi-patterning is drawing every second line, letting it dry, then going back for the ones in between.
5. Extreme ultraviolet is not a finer pen. It is a different tool entirely, which no glass lens can focus.
6. Where this comparison breaks: a pen deposits ink. Light deposits nothing. The limit comes from diffraction, how waves spread past an edge.

PLAIN3.8.3 a worked example#

1. Put real numbers into the Rayleigh formula from section 3.7: half-pitch equals k1 times wavelength divided by numerical aperture.
2. Dry 193 nanometre tool, numerical aperture 0.93, k1 of 0.30: about 62 nanometres.
3. Immersion 193 nanometre tool in water, numerical aperture 1.35, since water has refractive index near 1.44 here: about 43 nanometres.
4. EUV at 13.5 nanometres, numerical aperture 0.33: about 12 nanometres. High numerical aperture EUV at 0.55: about 7 nanometres.
5. Notice the jump. Moving to EUV bought more resolution in one step than the previous twenty years of optical improvement.

PLAIN3.8.4 what is really happening inside#

1. Here is how EUV light is actually made. It is not a lamp and not a normal laser.

tin droplet generator
   |  drops of molten tin, about 25 um across
   |  released about 50,000 times per second
   v
[ pre-pulse laser ]  -> flattens the drop into a disc
   |
   v
[ main pulse laser ] -> vaporizes it into hot plasma
   |
   v
plasma over 200,000 degrees emits 13.5 nm light
   |
   v
collector mirror -> multilayer mirrors -> reticle
   |
   v
more mirrors -> wafer

2. A carbon dioxide laser of over ten kilowatts average power fires twice at each falling droplet.
3. The first shot squashes the sphere flat. The second turns it into plasma, an extremely hot ionized gas radiating at 13.5 nanometres.
4. Everything absorbs this light. Air absorbs it, glass absorbs it. So there are no lenses, and the path must be in vacuum.
5. Instead the machine uses mirrors of about forty to fifty alternating pairs of molybdenum and silicon, each layer a few nanometres thick.
6. Even those reflect only around 70 percent. After ten bounces most of the light is gone, which is why source power is such a struggle.
7. The reticle is a mirror too, not a transparent plate. That is a fundamental break from all earlier lithography.
8. Tin debris coats the collector and shortens its life, so hydrogen gas is flowed through to clean it.

TECHNICAL3.8.5 the engineer’s version#

1. The 157 nanometre fluorine laser generation was researched hard and abandoned around 2003, because 193 immersion proved cheaper and better.
2. Immersion entered volume production around 2007, with water enabling numerical apertures up to 1.35.
3. EUV entered high-volume manufacturing in 2019, first at Samsung and TSMC for 7 nanometre class layers.
4. Low numerical aperture tools such as the ASML TWINSCAN NXE:3800E have numerical aperture 0.33 and are reported at 180 to 220 million US dollars.
5. High numerical aperture EUV, the TWINSCAN EXE:5200 family, has numerical aperture 0.55 and is reported at about 380 million US dollars per tool.
6. Anamorphic means the reduction differs by axis, 4x one way and 8x the other. The field halves to about 26 by 16.5 millimetres, so large dies are stitched.
7. ASML of Veldhoven, the Netherlands, is the only supplier of EUV scanners.
8. Zeiss SMT supplies the optics and TRUMPF the carbon dioxide laser, both of Germany. The tin source traces to Cymer, now part of ASML.
9. Where experts disagree: whether High-NA EUV beats low-NA plus double patterning on cost per layer. Intel has pushed High-NA; some analysts disagree. As of 2026 this is unsettled.
10. Established fact: EUV works and is in volume production. Active research: higher source power and dry resists. Marketing claim: any statement that a named node “requires” High-NA today.

WORDS3.8.6 remember these#

1. Deep ultraviolet — the 248 and 193 nanometre light — DUV from krypton fluoride and argon fluoride excimer lasers.
2. Immersion lithography — printing through water — a water film between final lens and wafer, raising NA above 1.
3. Multi-patterning — printing one layer in several passes — LELE, SADP and SAQP decomposition of a dense layer.
4. Extreme ultraviolet — 13.5 nanometre light — EUV, in the soft X-ray region, needing vacuum and reflective multilayer optics.
5. Laser-produced plasma — light made by vaporizing tin — LPP source, a dual carbon dioxide laser pulse at 50 kilohertz.
6. High-NA — the next EUV generation — numerical aperture 0.55 anamorphic optics with a halved exposure field.

3.9 The other steps#

PLAIN3.9.1 in simple words#

1. Printing patterns is half the story. We also add and change material.
2. Doping means adding a tiny controlled amount of a foreign element to change how the silicon conducts.
3. The main method is ion implantation. We turn the dopant into charged atoms, accelerate them, and fire them into the wafer.
4. That smashes the crystal, so afterwards we heat the wafer briefly. The lattice repairs and the dopants settle into place.
5. Oxidation means growing a glass layer by heating silicon in oxygen. The wafer rusts, in a useful and controlled way.
6. Then three ways of laying material on top: chemical deposition, physical deposition, and one-atomic-layer-at-a-time deposition.
7. Finally the transistors are wired together, in a stack of copper layers above them, fifteen or more.
8. A modern chip goes through many hundreds of process steps and spends about three months inside the fab.

PLAIN3.9.2 a picture in your head#

1. Think of building a city on a plain, where you may only work from above and must finish each floor before the next.
2. Doping is changing the soil chemistry in specific plots so buildings there behave differently.
3. Chemical vapour deposition is a fine mist that reacts and settles everywhere, even inside narrow trenches.
4. Physical vapour deposition is shot-blasting from one direction. It coats what it can see and struggles down deep holes.
5. Atomic layer deposition is placing one tile at a time across the whole city. Very slow, very exact.
6. The metal stack is the road network built above the buildings, with vertical lifts between levels.
7. Where this comparison breaks: a city is built once. Wafer layers are built, partly cut away and rebuilt, and nothing buried is reachable again.

PLAIN3.9.3 a worked example#

1. Here is the damascene method, which is how the copper wiring is made.

Start: a flat insulating layer over the transistors

1 etch a trench and a via hole into the insulator
2 line the hole with a thin barrier film (TaN/Ta)
3 sputter a thin copper seed layer
4 electroplate copper until it overflows the trench
5 polish the whole surface flat with CMP
6 the only copper left is inside the trench

Result: a wire buried in glass, top surface perfectly flat

2. Notice what did not happen. We never etched copper. Copper is hard to etch cleanly, so we cut the shape first and fill it.
3. That is damascene, named after the inlay metalwork of Damascus. Doing trench and vertical connection in one fill is dual damascene.
4. Repeat fifteen or more times, with wires getting wider and thicker as you go up.
5. Bottom layers carry signals inside one circuit block. Top layers are thick and carry power across the chip.

PLAIN3.9.4 what is really happening inside#

1. Ion implantation: a gas of boron, phosphorus or arsenic is ionized, sorted by mass with a magnet, then accelerated.
2. Energies run from under one thousand electron volts for shallow layers up to millions for deep wells.
3. Dose is counted as ions per square centimetre, typically ten to the twelve through ten to the sixteen, and is very repeatable.
4. Annealing: the wafer is heated in seconds, or milliseconds, to around 1,000 degrees Celsius, to repair damage and activate dopants.
5. It must be brief, because heat also makes dopants diffuse and smear the tiny features we just made.
6. Oxidation: heating silicon in oxygen or steam at 800 to 1,200 degrees Celsius grows silicon dioxide, consuming some silicon.
7. Chemical vapour deposition: gases decompose on the hot wafer. Physical vapour deposition: an argon plasma knocks atoms off a target onto the wafer.
8. Atomic layer deposition: two gases are fed alternately, never together. Each pulse adds at most one atomic layer, so thickness is counted in cycles.

TECHNICAL3.9.5 the engineer’s version#

1. The gate insulator was silicon dioxide for about forty years. Intel replaced it with hafnium-based high-k plus metal gates at 45 nanometres in 2007.
2. The honest version: since 2007 “gate oxide” is largely historical. The layer is a hafnium oxide film laid by atomic layer deposition.
3. Interconnect switched from aluminum to copper. IBM announced copper interconnect in 1997, using dual damascene with CMP.
4. Copper needs a barrier, historically tantalum nitride and tantalum, because copper diffuses into silicon and poisons devices.
5. Dielectrics moved from silicon dioxide, near 3.9, to carbon-doped low-k films near 2.5 to 3.0, to cut wire capacitance.
6. Advanced logic in 2026 uses 15 to 20 metal levels, from roughly 20 to 30 nanometre pitch at the bottom to micrometres at the top.
7. Backside power delivery is the current change. Intel calls its version PowerVia, shipped in 18A; TSMC’s equivalent arrives with A16.
8. Step counts: advanced logic is commonly described as more than 1,000 process steps with roughly 80 to 100 mask layers. Exact counts are confidential, so treat these as approximate.
9. Cycle time: a leading-edge logic wafer spends about 3 months in the fab, often quoted as 12 to 16 weeks. With packaging and test, four to five months.

WORDS3.9.6 remember these#

1. Doping — adding a trace element to change conduction — introducing acceptors or donors to set carrier type and concentration.
2. Ion implantation — firing dopant atoms into the wafer — mass-analyzed ion beam implantation, dose in ions per square centimetre.
3. Annealing — a short hot step to repair and settle — rapid thermal, spike, flash or laser anneal for damage repair and activation.
4. ALD — one atomic layer per cycle — atomic layer deposition, self-limiting surface reactions giving exact conformal thickness.
5. Damascene — cut the shape then fill it — trench-first copper metallization finished by CMP, in single and dual forms.
6. High-k — a better gate insulator than glass — a high permittivity dielectric, usually hafnium based, in use since 2007.

3.10 Testing, dicing, packaging#

PLAIN3.10.1 in simple words#

1. At the end of the fab, the wafer holds hundreds of finished chips, still joined in one disc. Some are broken.
2. So we test every one, while they are still attached.
3. A machine lowers a head with hundreds of fine needles onto each chip, sends in signals, and checks the answers.
4. Bad chips are marked for scrap. Good chips are sorted by how well they performed, which is called binning.
5. The same design, from the same wafer, can sell as an expensive fast part or a cheaper slow part.
6. Then the wafer is cut into individual chips. Each is glued into a package, connected electrically, and covered.
7. The package is not just protection. It carries power in, carries heat out, and fans tiny pads out to board-sized contacts.

PLAIN3.10.2 a picture in your head#

1. Think of biscuits baked as one sheet, which must be checked, graded, cut and boxed.
2. Testing is tasting each one before cutting. Cheaper than boxing a bad one and finding out later.
3. Binning is grading: perfect ones in the premium box, uneven ones in the value box, from the same recipe.
4. Modern high-end products do not use one big biscuit. They use several smaller ones side by side, connected together.
5. Where this comparison breaks: biscuits need not line up to a micrometer, and none needs 1,000 watts of heat carried off a postage stamp.

PLAIN3.10.3 a worked example#

1. Take a 300 millimetre wafer, about 70,700 square millimetres, and a die of 100 square millimetres.
2. A circle cannot be tiled perfectly by rectangles, so you get about 600 full dies, not 707.
3. Apply defects at 0.1 per square centimetre and about 90 percent are good, so about 540 good dies.
4. If the processed wafer cost 18,500 US dollars, that is about 34 US dollars per good die.

5. Doubling die area more than doubles cost per working chip. You lose twice over: fewer dies and worse yield.
6. That table, and nothing else, explains why the industry moved to chiplets.

PLAIN3.10.4 what is really happening inside#

1. Wafer probe, or wafer sort, is the first electrical test. A probe card with hundreds of needles contacts the pads, often at several voltages and temperatures.
2. Dicing separates the dies. A diamond blade saw is traditional. Laser stealth dicing makes a weak plane inside the silicon, then the wafer is stretched and splits.
3. Die attach fixes the die down, face up on a pad or face down onto a substrate.
4. Wire bonding joins the die pads to the package with fine gold or copper wires, welded by heat and ultrasound. Cheap and mature.
5. Flip-chip turns the die upside down and connects through solder bumps across the whole face, allowing many more connections and shorter power paths.
6. Above the die goes a lid or heat spreader, joined by a thermal interface material: a paste, a pad, or soldered metal.
7. Underneath sits the substrate, a small multilayer board fanning fine connections out to larger solder balls or pins.
8. Chiplets change the picture. Several dies sit on a shared carrier and behave as one product.

TECHNICAL3.10.5 the engineer’s version#

1. Yield is modelled from defect density. Two standard forms are used.

Poisson: Y = exp(-A * D0)
Murphy:  Y = ((1 - exp(-A * D0)) / (A * D0)) ^ 2

A  = die area in square centimetres
D0 = defect density per square centimetre

2. Murphy’s model is usually closer to reality, because defects cluster rather than spreading evenly.
3. Mature high-volume nodes run D0 near 0.05 to 0.1 per square centimetre. A new node starts far worse and improves over quarters.
4. Reported N2 test-chip yields in early 2026 were about 70 to 80 percent for TSMC, with Intel and Samsung lower. These are press reports, not disclosure.
5. Binning sorts by maximum stable frequency, leakage, and functional core count. Fusing off a defective core is normal and deliberate.
6. The reticle limit sets the largest single die at about 26 by 33 millimetres, 858 square millimetres, at low numerical aperture EUV.
7. 2.5D packaging places multiple dies on a silicon interposer. TSMC’s platform is CoWoS, introduced in 2012; Intel’s bridge alternative is EMIB.
8. 3D packaging stacks dies with through-silicon vias. Examples are Intel Foveros, announced 2018, and TSMC SoIC.
9. High Bandwidth Memory is a JEDEC standard: stacked DRAM joined by through-silicon vias, placed beside the logic die. HBM4 was standardized in 2025.

10. The known good die problem is central. Stacking three good dies with one bad one wastes all four, so pre-assembly test coverage must be very high.
11. Advanced packaging capacity, not wafer capacity, has been the binding constraint on artificial intelligence accelerator supply since 2023.

WORDS3.10.6 remember these#

1. Wafer probe — testing chips before cutting — wafer sort using a probe card and automated test equipment.
2. Yield — the share of chips that work — good die over gross die, modelled from area and defect density.
3. Binning — sorting identical chips into product grades — speed, power and core-count sorting of one die design.
4. Flip-chip — die mounted face down on bumps — controlled collapse chip connection, giving area-array input and output.
5. Interposer — a carrier that wires dies together — a silicon or organic substrate with fine-pitch routing, the basis of 2.5D.
6. Chiplet — a small die that is part of a bigger product — a partitioned die assembled with others into one package.
7. HBM — stacked memory beside the processor — High Bandwidth Memory, a JEDEC standard using through-silicon-via DRAM stacks.

3.11 What “3 nm” actually means now#

PLAIN3.11.1 in simple words#

1. Chip generations have names like 7 nanometre, 5 nanometre, 3 nanometre, 2 nanometre.
2. Most people assume the number is the size of something on the chip. It is not, and has not been for over a decade.
3. Today it is a generation label meaning “our next, better process”, and each company picks its own numbers.
4. A silicon atom is about 0.2 nanometres across. Nothing useful can be three atoms wide and still work as a transistor.
5. On a real 3 nanometre process, the spacing between neighbouring gates is about 45 nanometres, fifteen times the name.
6. What did change, really and physically, is the shape of the transistor.
7. It went from flat, to a standing fin gripped on three sides, to stacked ribbons with the gate wrapped all the way around.
8. Those shape changes are real engineering. The numbers on the box are marketing.

PLAIN3.11.2 a picture in your head#

1. Think of a garden hose with a hand squeezing it. The hand is the gate; the water is the current.
2. Flat transistors are a hose on the ground with one hand pressing from the top. It works, but water leaks past.
3. A FinFET stands the hose on edge so the hand grips three sides. Much better control, much less leak.
4. Gate-all-around wraps the hand fully around the hose, with several thin hoses stacked above one another.
5. That is why the industry moved: at small sizes a flat gate simply stopped being able to turn the current off.
6. Where this comparison breaks: no water flows. Current is carried by electrons or holes, and “off” means suppressing quantum tunnelling and thermal leakage.

PLAIN3.11.3 a worked example#

1. Here is the growth in transistor count, with real parts and real years.

2. From 2,300 to 208 billion is a factor of about 90 million, in 53 years.
3. The honest version on the 4004: Intel has long quoted 2,300, and that is the number in most books. Careful die counts give about 2,250.
4. A second honesty note: Apple publishes no transistor count for every part. None was published for the A19 Pro of 2025, so the table uses the M4.
5. The Cerebras WSE-3 is a special case. It is not diced at all. It is one square cut from a wafer, about 46,225 square millimetres, with 900,000 cores.

PLAIN3.11.4 what is really happening inside#

1. Originally the node name did mean something. In the 1970s and 1980s it tracked the gate length.
2. Then it drifted to meaning half the spacing between the first metal wires.
3. Then, from roughly the 22 and 20 nanometre generations, it stopped tracking anything measurable.
4. Companies chose different numbering, so an Intel node and a TSMC node with the same name were not the same thing.
5. Intel renamed its own nodes in 2021 to line up with the competition, which is itself an admission that the numbers are labels.
6. Look instead at transistor density, in millions of transistors per square millimetre, plus the gate and metal pitches.
7. Even density is arguable, because it depends on which cell library you count and what mix of logic you assume.

TECHNICAL3.11.5 the engineer’s version#

1. Planar bulk MOSFET dominated from the 1960s to about 2011.
2. The FinFET concept was demonstrated as DELTA by Hisamoto and colleagues at Hitachi in 1989.
3. It was then developed and named FinFET at the University of California, Berkeley around 1999, by a team including Chenming Hu, Tsu-Jae King Liu and Jeffrey Bokor.
4. Intel put it into volume production first, as Tri-Gate at 22 nanometres, announced 2011 and shipping 2012.
5. Gate-all-around nanosheet reached mass production first at Samsung, with 3GAE in 2022.
6. TSMC moved to nanosheet at N2, starting mass production in late 2025 at Fab 20 in Hsinchu and ramping through 2026.
7. Reported N2 wafer price is about 30,000 US dollars, against roughly 20,000 to 25,000 for 3 nanometre class.
8. Intel 18A, with RibbonFET gate-all-around plus PowerVia backside power, entered high-volume manufacturing in 2025 with Panther Lake.
9. Where experts disagree: how to compare nodes fairly. Density metrics weighted across cell types are contested, and there is no neutral referee.
10. Established fact: nanosheet is in production in 2026. Active research: complementary FET, stacking n-type and p-type vertically, and two-dimensional channel materials. Marketing claim: node names as measurements.
11. The honest version: if someone says a 3 nanometre chip has 3 nanometre features, they are repeating a press release. Ask for gate pitch and density.

WORDS3.11.6 remember these#

1. Node — a process generation — a named technology offering, no longer tied to any physical dimension.
2. Gate length — how far current travels under the gate — the physical channel length, now decoupled from the node name.
3. Contacted poly pitch — spacing between transistor gates — CPP, a real comparable dimension, about 45 nanometres at TSMC N3.
4. FinFET — a transistor standing on edge — a fin channel with the gate on three sides, in production from 2011.
5. Gate-all-around — the gate wrapped fully around — GAA nanosheet or ribbon channels, in production from 2022.

3.12 Who makes chips and why it matters#

PLAIN3.12.1 in simple words#

1. Designing a chip and making a chip used to be the same business. Not any more.
2. Most chip companies do not own a factory. They design and pay someone else to build. That is the fabless model, and the builder is a foundry.
3. The largest foundry by far is TSMC, in Taiwan. It builds for companies that compete with each other and sells no branded chips.
4. Samsung, in South Korea, is both a foundry and a chip company of its own.
5. Intel, in the United States, historically built only its own chips, and is now trying to be a foundry for others too.
6. There is a second layer of licensing. ARM, in the United Kingdom, makes no chips. It designs instruction sets and cores, and licenses them.
7. RISC-V is a newer alternative, where the instruction set itself is open and free to use.
8. The important fact is concentration. Very few buildings on Earth can make the most advanced chips.

PLAIN3.12.2 a picture in your head#

1. Think of book publishing. An author writes, a printing plant prints, and a typeface company licenses the letterforms.
2. Fabless chip companies are the authors. Foundries are the printing plants, owning the expensive machines and printing for whoever pays.
3. ARM is the typeface company. Nobody buys a typeface alone, but almost every book uses one, and the fee is small per copy and huge in total.
4. RISC-V is a typeface released free for anyone to use and modify.
5. Where this comparison breaks: there are thousands of printing plants. There are fewer than five organizations that can print at the leading edge, and one supplier of the key machine.

PLAIN3.12.3 a worked example#

1. Trace an Apple phone chip from idea to shipment.
2. Apple designs it in California, using an ARM instruction set under an architecture licence, then sends layout files to TSMC.
3. TSMC makes masks, then runs wafers in Taiwan on ASML machines from the Netherlands, with optics from Germany.
4. The blank wafers most likely came from Japan, where Shin-Etsu and SUMCO dominate 300 millimetre supply.
5. Finished wafers are tested, diced and packaged, often in Taiwan, then assembled into phones elsewhere in Asia.
6. Not one country in that chain could complete it alone. That is the point.

PLAIN3.12.4 what is really happening inside#

1. The reason for the split is cost. A leading-edge fab now costs 25 to 35 billion US dollars and must be upgraded every few years.
2. Only a company running many customers’ products can keep such a fab full enough to pay for itself.
3. So designers stopped buying fabs, and the surviving fab owners got larger and fewer.
4. This is not a conspiracy. It follows from rising fixed costs in a business that needs volume to cover them.
5. The same logic applies at ASML, where the research cost of EUV was so large that only one company saw it through.
6. Concentration then becomes a security problem, because one earthquake or export restriction can affect the whole world’s supply.
7. Governments responded with subsidy programmes, including the United States CHIPS and Science Act of 2022 and the European Chips Act of 2023.

TECHNICAL3.12.5 the engineer’s version#

1. TSMC was founded in 1987 by Morris Chang and created the pure-play foundry model. Before that, building for others was a side business.
2. Early fabless companies include Xilinx, founded 1984, Qualcomm, founded 1985, and NVIDIA, founded 1993.
3. ARM was founded in 1990 as Advanced RISC Machines, a joint venture of Acorn Computers, Apple and VLSI Technology.
4. ARM licences come in two tiers: core licences, where you use ARM’s design, and architecture licences, where you build your own compatible core. Apple holds the latter.
5. RISC-V began at the University of California, Berkeley in 2010. RISC-V International moved its legal home to Switzerland in 2020.
6. Important distinction: RISC-V being open does not make any particular RISC-V chip open. The instruction set is open; implementations may be proprietary.
7. Market share: TSMC held roughly 67 to 71 percent of the global foundry market in early 2026, depending on the analyst. Its leading-edge share is higher.
8. In materials, Shin-Etsu Chemical and SUMCO, both Japanese, supply most of the world’s 300 millimetre polished wafers.
9. TSMC’s Arizona site began 4 nanometre class production in 2024. The company has announced about 265 billion US dollars of United States investment.
10. Established fact: leading-edge capacity is concentrated in Taiwan and South Korea. Active development: Arizona, Japan and Dresden fabs ramping. Marketing claim: that any subsidy programme has already ended that concentration.
11. To see part of this chain yourself: on Linux, lscpu reports vendor and microarchitecture; on macOS, sysctl -n machdep.cpu.brand_string names the part.

WORDS3.12.6 remember these#

1. Fabless — designs chips, owns no factory — a company outsourcing all wafer manufacturing to a foundry.
2. Foundry — a factory that builds other people’s designs — a contract wafer manufacturer, pure-play if it sells no branded chips.
3. IDM — a company that designs and builds — integrated device manufacturer, the older model, as at Intel and Samsung.
4. Tape-out — sending the finished design to be made — release of final layout data to mask making.
5. RISC-V — an open, free instruction set — an open standard ISA governed by RISC-V International.

3.98 Common wrong ideas#

1. Wrong: chips are made from ordinary beach sand. Right: they are made from selected lump quartz or quartzite above 99 percent silica, chosen for low iron content.
2. Wrong: silicon is mined as a metal. Right: silicon never occurs pure. It is always bound to oxygen and must be reduced out with carbon at about 1,900 degrees Celsius.
3. Wrong: 99 percent pure is good enough. Right: that is one foreign atom in a hundred. Chips need nine to eleven nines, roughly one per billion or better.
4. Wrong: a wafer is just a slice of purified silicon. Right: it must be one single crystal with no grain boundaries, grown from a seed, with specified orientation and resistivity.
5. Wrong: the mask is a stencil shaped like the circuit. Right: it is a 4x enlarged plate of computed shapes, distorted by optical proximity correction so the printed result is correct.
6. Wrong: EUV is just a brighter ultraviolet lamp. Right: it is 13.5 nanometre soft X-ray light made by vaporizing tin droplets, absorbed by air and glass, so it needs vacuum and mirrors.
7. Wrong: a 3 nanometre chip has 3 nanometre features. Right: the node name is a marketing label. Gate pitch on a 3 nanometre class process is around 45 nanometres.
8. Wrong: sand is cheap, so chips should be cheap. Right: the blank wafer is well under 1 percent of a processed leading-edge wafer. The value is in more than a thousand process steps.
9. Wrong: a faster and a slower processor from one family are different designs. Right: they are frequently the same die, binned by measured performance, sometimes with defective parts fused off.
10. Wrong: making the chip is hard and packaging is trivial. Right: since 2023, advanced packaging capacity rather than wafer capacity has limited artificial intelligence accelerators.

3.99 Chapter summary in 20 lines#

1. Silicon is about 27.7 percent of the Earth’s crust by mass, second only to oxygen, and never occurs pure.
2. It is locked in silica and silicate minerals, and the cleanest common source is the mineral quartz.
3. Chip feedstock is lump quartz or quartzite above 99 percent silica, not beach sand, for both purity and particle size.
4. A submerged-arc furnace at about 1,900 degrees Celsius reduces quartz with carbon, giving metallurgical-grade silicon at 98 to 99.5 percent.
5. That silicon becomes trichlorosilane, is distilled, and is deposited back onto hot filaments by the Siemens process at about 1,100 degrees Celsius.
6. The result is polysilicon at nine to eleven nines purity, roughly one foreign atom per billion or fewer.
7. Polysilicon is melted and regrown as one single crystal by the Czochralski method, using a seed, a thin neck, and slow rotating pulling.
8. A 300 millimetre boule is about 2 metres long and weighs about 265 kilograms, with a defined orientation and dopant level.
9. Float-zone growth gives purer, higher-resistivity silicon without a crucible, but is limited in diameter and used for power and detector devices.
10. The boule is cropped, ground, notched, wire sawn, lapped, etched and polished into 775 micrometer mirror wafers.
11. 300 millimetres is the industry limit. The 450 millimetre transition stalled when its consortium collapsed around 2016 and 2017.
12. Fabs run at ISO 14644-1 cleanliness with hundreds of air changes per hour, ultrapure water at 18.2 megaohm-centimetre, and vibration isolation.
13. A 2 nanometre class fab module costs roughly 25 to 35 billion US dollars, most of it tools rather than building.
14. Photolithography prints one 26 by 33 millimetre field at a time through a 4x reticle, then steps across the wafer and repeats.
15. Resolution follows the Rayleigh criterion, so shorter wavelength and higher numerical aperture give smaller features, at the cost of depth of focus.
16. Light went from 436 and 365 nanometre mercury lamps, to 248 and 193 nanometre lasers, to 193 nanometre immersion, to 13.5 nanometre EUV.
17. EUV comes from tin droplets struck twice by a carbon dioxide laser, 50,000 times a second, focused by molybdenum-silicon mirrors in vacuum, and only ASML builds the machine.
18. Doping, annealing, oxidation, CVD, PVD, ALD and 15 or more copper damascene metal layers add up to over 1,000 process steps and about three months in the fab.
19. Wafers are probe tested, binned, diced and packaged, and defect density punishes large dies so hard that the industry moved to chiplets, interposers and stacked memory.
20. Node names are marketing labels, transistors went planar to FinFET to gate-all-around, and the ability to build at the leading edge sits in very few hands.