What does it take to build a chip fab, and why does it take years and so much money?

What the news calls "building a new fab" is a long chain of work: choosing a site, designing it, putting up a very steady building, installing the utilities, certifying the cleanroom, moving in and hooking up hundreds of tools, tuning each one until it works, and finally letting the first products' yield climb. That's why "construction begins" and "volume production starts" are often several years apart. Most of the money goes into the tools.

A chip fab is a wafer fabrication plant (What is a fab in semiconductors?). Below, step by step: what happens, why, and what goes wrong if you skip it.

Building a fab, step by step: what has to happen?

Step 1: Choose a site

• What: plenty of water and power, and both steady; stable ground with little vibration nearby; engineers and technicians to hire; roads that tools and chemicals can come in on. Before construction there are permits to apply for and an assessment of the effect on the environment.
• Why: a fab uses large amounts of water and power all year round (Why do semiconductor fabs use so much electricity?, How pure is ultrapure water?).
• If not: once a fab is built it can't move. Finding out afterwards that the water falls short or the power is unsteady is very hard to fix.

Step 2: Design it in layers

• What: the cleanroom, where the chips are made, is the middle level. Below it is the subfab, with the tools' vacuum pumps, exhaust treatment and piping. Above the ceiling is the air supply space: rows of fans and filters blow clean air down, and it flows back out through the perforated floor. Where each tool goes, and where its water, power and gas come up from, is drawn now too.
• Why: the cleanest level is kept for wafers and tools; things that shake or might leak go downstairs, where pipes can come straight up to the tool on the shortest path.
• If not: changing it after it's built often means tearing it out and starting again.

Step 3: Put up the building, with a very steady floor

• What: the cleanroom's floor slab is often thick, heavy concrete, full of square holes so the air can flow down through it. The columns under it stand close together, and some fabs sink very deep piles. Pumps and fans that vibrate are placed farther away or on vibration-isolating mounts. Earthquakes count too: the building is designed to withstand them, and tools are anchored to the floor.
• Why: a scanner has to line up each layer's pattern very precisely with the layer below (overlay), and a floor that shakes can knock the print out of line. In the strictest areas, the vibration allowed is many times smaller than what a person can feel.
• If not: patterns that don't line up mean wafers have to go back and be redone, and chips may fail.

Step 4: Install the utilities

• What: power, ultrapure water, gases, chemicals, air handling, exhaust, wastewater treatment and cooling water. The main lines run to each tool's planned spot and end in connection points. All of this belongs to Facilities (What does a fab facilities engineer do?, What gases does a chip fab use?).
• Why: everything a tool needs to run comes in through these systems.
• If not: tools that arrive can only sit and wait.

Step 5: Test the cleanroom first

• What: before the tools arrive, count the particles in the air, measure airflow and pressure differences, and check the filters for leaks. Once tools are in and people start work, it's measured again (How clean is a cleanroom?).
• Why: an empty room is the easiest place to find problems.
• If not: you find the leak when dust lands on the first wafers.

Step 6: Move in the tools, hook them up, check them out

• What: a fab holds several hundred tools. Crates are opened outside and each tool is wiped clean, then it comes in through two doors that never open at the same time. Once it's in place, its water, power, gases and exhaust are connected one line at a time from a connection list: this is hook-up. New gas lines get a pressure test and a leak check. After power-on, the tool is tested item by item against conditions the buyer and the seller agreed on in advance, and only when everything passes is it accepted.
• Why: one wrong connection or one loose fitting can let a toxic gas escape, or damage the tool.
• If not: the problem shows up only once wafers are running, when it's much harder to find.

Step 7: Tune every step with test wafers

• What: each tool first runs wafers that aren't product (What are monitor wafers and dummy wafers?). Engineers measure film thickness, line width and how many particles were added, and adjust until it's within spec. Then several steps in a row are run together, and finally the whole flow from start to finish.
• Why: a chip goes through hundreds of steps (How are computer chips made?); if one step is off, everything after it is off too.
• If not: trying it out on real product means weeks to months of wafers wasted when it goes wrong (How long does a wafer take to make?).

Step 8: The first products, and yield slowly climbs

• What: the first product lots get their wafer start. At first, good chips are often few. Engineers find the most common way the chips fail, fix its cause, then move on to the next (Why do bigger chips have lower yield?), and the customer tries out samples (What is new product introduction (NPI)?). Only once things are steady do the wafer starts go up, lot by lot.
• Why: while yield is low, making more just makes more bad chips.
• If not: pushing volume before it's steady wastes both money and time.

Why does it take years?

Whatever can overlap does: when one area of the building is ready, tools move into that area first. But three things can't be rushed:

• Each step waits for the one before: no finished floor, no tools moving in; no utilities, no tools running; no checked-out tools, no product.
• Tools wait their turn: some take many months from order to delivery, and when everyone is expanding at once, the wait gets longer. And there are hundreds of them, each to be moved in, hooked up and checked.
• Yield takes time to climb: many changes only show their result once wafers have made a full trip through the fab, and each trip takes weeks to months.

General sources agree on roughly this scale: from groundbreaking to the first wafers often takes a year or two or more. Add the planning and permits before construction and the yield ramp after, and from the decision to build to volume shipments often takes several years. Every fab is different.

Why is it so expensive?

• Most of the money goes into the tools: there are hundreds of them, and many cost a lot each. The most advanced extreme ultraviolet scanner costs over a hundred million dollars on its own (What is extreme ultraviolet (EUV) light?). An industry association's worldwide figures show the same thing: in a year, far more is spent on fab equipment than on building new fabs.
• The building isn't cheap either: the steady floor, the cleanroom and the whole set of utilities are far more demanding than in an ordinary factory. And for years, money goes out with no chips to sell.

General sources put a leading-edge fab, built and fully equipped, at several billion to over ten billion dollars (Why are chips so expensive?); a fab for older generations of chips usually costs much less (The news says "mature nodes"). So once it's built, it has to stay fully booked all year (Why do chip fabs run 24 hours a day?). Fabs being slow and costly to build is also one reason chips swing from shortage to oversupply (What is the semiconductor cycle?).

Next time you see it in the news

• "Construction begins on a new fab": work on the building has started. No tools have arrived yet, and chips are still a long way off.
• "Tool move-in": the building and cleanroom are mostly ready, and tools are starting to be moved in, hooked up and checked out. News also calls this "equipment installation".
• "Trial production": the tools are tuned and the first products are being made; yield is still climbing and volumes are small.
• "Volume production": yield and output are steady, and large shipments begin. A new fab's capacity usually comes online in stages.

In fab24hr

The game doesn't show a whole fab being built. It shows the day one new tool moves in. Tap "Clock in", choose "A day in the fab", then on the "Your role today" card tap "Production fab", swipe to the Facilities engineer and tap "Gases & chemicals" under the name. The afternoon shift is "Move-In": the new tool's crates are opened outside and wiped down, and the two doors open in order; downstairs in the subfab you hook it up from the connection list; and the new gas line needs a pressure test. Run it to the end and the vendor waits an extra day to start the tool: your call. The other three Facilities areas spend the same afternoon on the other end of the same tool: the Power engineer connects its power, the Water engineer flushes its newly connected ultrapure water line clean, and the HVAC engineer watches the pressure difference at the move-in entrance and the tool's exhaust.

On the card, tap "R&D line" and swipe to the vendor field service engineer: you look after a new etch tool, ETCH-R1, at the customer's fab, from checkout to signed acceptance. The evening shift is the end of the quarter; your manager hopes the customer signs the final acceptance today, and the leak check reading sits right at the edge of the pass line.

The fabs, companies, people, tool numbers and times in the game are fictional. The steps, years and costs of building a fab come from public, general sources, given only at the scale those sources agree on. For other jargon, see Chip fab jargon in plain English.