Semiconductors 101: what is a semiconductor, and what does a chip fab do?

A semiconductor is a material that conducts electricity better than an insulator but worse than a conductor, and whether it conducts is something people can control. The most common one is silicon. A small switch made from it and controlled by electricity is a transistor, and many transistors built together make a chip. When people say they "work in semiconductors" or talk about "a semiconductor plant", they usually mean the whole industry that makes chips: someone designs the chip, a fab builds it on a wafer, an assembly-and-test house tests it and packages it, and it ends up in phones, computers and cars. This article connects those pieces in plain English, then gives a free learning path you can follow with no background at all.

What is a semiconductor?

Think of electricity as water in a pipe. A conductor is a pipe that's always open, an insulator is a pipe that's blocked, and a semiconductor is a pipe with a valve whose opening can be adjusted. Add a tiny amount of another kind of atom to very pure silicon (doping), and you decide which small region conducts, and how well.

A switch built on this and controlled by electricity is a transistor: on is 1, off is 0. One chip can hold hundreds of millions, even tens of billions, of transistors. Taking a photo, finding a route, running AI on a phone all come down to them switching on and off.

To go a little further, read these three in order: What is a semiconductor?, What is a chip? and What is a transistor?.

What does the semiconductor industry do?

"Semiconductor" started as the name of a material and became the name of the business of making chips. So "what do semiconductors do?" can be two questions. If it's about the material, the answer is the section above. If it's about the industry, the answer is: design chips, make them, test and package them, and deliver them to the companies that build phones, computers, cars and appliances.

Which kinds of companies does a chip pass through?

Stage	What happens	Like
Design (IC design; IC is another word for chip)	Engineers design the circuit on computers and simulate and check it many times; when it's final, the design is handed over and turned into photomasks (the stencils used to print the circuit)	Drawing the blueprints
Manufacturing (the fab)	Wafers go through hundreds of steps, building up transistors and wiring layer by layer, over weeks to months	Building to the blueprints
Assembly and test	Every chip is tested on the wafer first, then the wafer is cut, each chip gets a package and leads, and it's tested again; only good ones ship	Inspecting, packing, shipping
Into a product	Soldered to a circuit board and built into a phone, computer or car	Into someone's hands

There are also companies that supply materials (silicon wafers, chemicals, specialty gases) and the tools. News stories often call design "upstream", manufacturing "midstream" and assembly and test "downstream", but not everyone divides it the same way, and some put materials and tools furthest upstream. When you see "upstream", check which stage the writer means.

These stages are often done by different companies: some only design and don't own a fab, some fabs make chips only for other companies, and some do everything from design to manufacturing themselves. For how they differ, read What is a foundry?; for the last stages, read What is chip packaging? and How are chips tested?.

So what actually happens inside a chip fab?

A fab does the middle stage: it turns a round, thin silicon wafer into a wafer covered edge to edge with chips.

Chips are built up layer by layer, and for every layer the wafer makes a loop through several process areas: litho (lithography) prints the pattern, etch cuts it in, thin film grows a new layer of material, CMP polishes the surface flat, the furnace grows oxide at high temperature and settles implanted atoms into place, ion implant shoots atoms into the silicon, and wet clean washes the surface, with measurements again and again in between to check that each step came out right. For what each area does, read What do the seven process areas of a chip fab do?; for one chip's whole journey from handed-over design to finished product, see The life of a chip.

All of this happens in a cleanroom, where the air is far cleaner than in an ordinary room and people wear full-body suits (How clean is a cleanroom?). The tools are expensive and a wafer takes weeks to months to finish, so the fab never stops and people work in shifts (Why do chip fabs run 24 hours a day?).

What do the people in a fab do all day?

Not everyone looks after a tool. Roughly:

• Process engineers own how one area does its steps, and its recipes. If what comes out of that area isn't right, they're the first to ask.
• Equipment engineers keep the tools running, and fix and maintain them.
• Process integration engineers follow one product from start to finish and decide whether a lot can move on.
• Manufacturing schedules the lots and chases progress so wafers keep moving from station to station on time.
• Facilities runs the water, power, air conditioning, gases and chemicals that keep the whole fab alive.
• Quality checks before shipping, and when something goes wrong, follows it until the cause is found and fixed.

For every kind of job across the industry, see What jobs are there in the semiconductor industry?. What each one in the fab does and how they differ: Who works in a chip fab, A day in the life of a fab engineer, and What's the difference between a process engineer and an equipment engineer?

Are semiconductors hard to understand?

It depends on how far you want to go. To understand how chips are made, what a fab does and who does what inside it, you don't need a physics or chemistry background: comparisons with water pipes, switches, printing and building a house get you through the whole flow. The hard part is the reasoning underneath (how electrons move in a solid) and the details of each step, which students in electrical engineering, physics, materials and chemical engineering spend years on. So understand the flow first, then dig deeper if you're curious.

Starting from zero: where do I begin?

A path that needs no background and costs nothing:

1. Read three articles, about fifteen minutes: what a semiconductor, a chip and a transistor are (the three linked above, right after this one in Chip basics).
2. See how one chip gets made: The life of a chip covers design, pilot run, mass production, test, packaging and shipping on one page.
3. Walk through a chip fab yourself: fab24hr is a free 3D web game. No install, no sign-in, and it runs on a phone. Follow the main story, The life of a chip, chapter by chapter, or pick a role in A day in the fab and work one shift, about 5 to 15 minutes. In the fab, tap a tool: 16 kinds have Take it apart, which shows how the tool is built, part by part, and See it work, which runs it step by step.
4. Tap any jargon for a plain explanation: every piece of jargon in the game can be tapped, and there's Chip fab jargon in plain English too.
5. To follow the news: read Chip news explained: 2 nanometers, yield, advanced packaging, foundries.
6. If you're thinking of working in a fab: start with What jobs are there in the semiconductor industry? and Is working in a semiconductor fab hard?, then the rest of Working in a fab.

Where else can I learn for free?

To go deeper, look for these:

• University open courses and public lecture notes: search for "semiconductor devices" or "introduction to semiconductor manufacturing". Many universities post free videos and notes, and they cover the physics and chemistry most thoroughly.
• Online beginner courses: some industry associations and universities offer free introductory courses for people without a science or engineering background.
• Textbooks: a "semiconductor devices" book explains why they work; a "semiconductor manufacturing" book explains how they're made.
• Science videos and 3D animations: for steps you can't see with your eyes, like lithography and etch, animation is the most intuitive.

A good order: understand the whole flow first (this article, The life of a chip, fab24hr), then pick the part you're curious about and go deeper. If you like physics, read about devices; if you like factories, read about process; if you're job hunting, read about what each role does.

In fab24hr

fab24hr's main story, The life of a chip, follows a fictional hearing-aid chip, Glowmere. In the prologue, Tape-out, the design is handed over to the fab. Act one is the pilot run on the R&D line, where chapter 2, Station by Station, goes through the seven process areas. Act two is the production fab, act three is the test-and-assembly house, where the chip is tested and packaged, and in the final chapter it goes into a hearing aid and into Mr. Shen's hands. You can go through every stage in this article in the game. The company, people, tool numbers and figures in the game are fictional; what a semiconductor is, how the work of making chips is split up and how a fab works follow public, general sources.