Topic 3 - Integrated Circuits and Semiconductors

Introduction to integrated circuits, and how semiconductors like silicon are used in CPUs.

What is a semiconductor?

a material that can act as both a conductor and an insulator, allowing control over when and how electricity flows.

How do conductors, insulators, and semiconductors differ?

Conductors allow electricity to flow freely

Insulators block it completely

semiconductors can switch between conducting and insulating states.

Why is silicon commonly used as a semiconductor material?

Silicon is abundant (found in sand), cheap, stable, durable, and easy to modify using doping, making it ideal for electronics and CPUs.

What is doping?

Doping is the process of adding small amounts of other elements to silicon to change its electrical properties and improve conductivity.

What is n-type semiconductor material?

N-type silicon is doped with elements like phosphorus or arsenic that add extra electrons (negative charge carriers), increasing conductivity.

What is p-type semiconductor material?

P-type silicon is doped with elements like boron that create “holes” (positive charge carriers) where electrons can move, allowing current flow.

What happens when n-type and p-type silicon are joined together?

They form a PN junction, which allows current to flow in only one direction — the basis for diodes and transistors.

What is an integrated circuit (IC)?

a tiny chip made from silicon that contains thousands or millions of transistors and other components connected together to perform tasks.

Why are integrated circuits important in CPUs?

They allow complex circuits to be Shortened, making CPUs faster, smaller, and more efficient while containing billions of transistors on one chip.

What are the main steps in making a silicon CPU?

1. Melt and purify silicon into wafers.
2. Use photolithography to etch circuit patterns.
3. Dope selected areas to create n-type and p-type regions.
4. Add metal layers to connect transistors.
5. Cut, wire, and package the final chip.

What is photolithography?

A process using light to print circuit patterns onto a silicon wafer during chip manufacturing.

What does the PN junction do in a transistor?

It acts like a switch, controlling the flow of electrons and allowing or blocking current depending on the applied voltage.

How does doping affect the electrical conductivity of silicon?

Doping increases conductivity by adding free charge carriers — electrons in n-type and holes in p-type material.

How do transistors use semiconductors to perform logic?

Transistors act as electrical switches that turn on (1) or off (0), forming the binary logic that CPUs use to process data.

Why are semiconductors essential for modern computing?

Because they can both conduct and insulate electricity, allowing transistors to switch states quickly and efficiently to represent binary data.

What would happen if CPUs were made only from conductors?

Electricity would always flow, meaning transistors could never turn off — the CPU wouldn’t be able to represent binary logic.

What would happen if CPUs were made only from insulators?

Electricity could never flow, so no signals or operations could occur — the CPU wouldn’t function at all.

How are semiconductors connected to binary logic in CPUs?

Semiconductors enable transistors to act as on/off switches that represent 1s and 0s, forming the basis of binary logic and computation.