Part 3, The Integrated Circuit: A Revolution in Electronics

In the “oxidation” step, an oxide layer (SiO₂) is formed on the surface of a wafer of silicon, the most important material to the semiconductor process. Now that the surface is protected from impurities, it’s time to draw in the semiconductor circuit design. What do the circuits look like in a semiconductor chip no larger or thicker than a human fingernail? This time, we’ll be learning about integrated circuits (ICs).

The inside of a tiny semiconductor chip is packed with thousands to millions of electronic components (diodes, transistors, capacitors, resistors). How did semiconductor integrated circuits come about?

Transistors: Where evolution began

In 1947, researchers at Bell Labs, the central R&D institute for American Telephone & Telegraph (AT&T), America’s largest telecommunications company, discovered that making a semiconductor grid come in contact with an electric wire (used for electric current) amplifies electric signals.

From left to right: John Bardeen, William Bradford Shockley, and Walter Houser Brattain of Bell Labs

The invention was first called an amplifier and was later renamed the transistor.

The transistor soon became a core component of electronics. But as technology progressed, electronic products took on more and more functions. This led to an exponential increase in components that needed to be connected, from transistors and resistors to diodes and capacitors. These contact points were also responsible for most product malfunctions. In 1958, engineer Jack Kilby at Texas Instruments in the U.S. developed a solution. Complex electronic components would be downsized, then printed onto a small surface as a circuit. These circuits would be stacked one on top of the other. The integrated circuit (IC) was born.

The Integrated Circuit (IC): A Revolution in Electronics

The transistors, resistors, diodes and capacitors populating a semiconductor integrated circuit (IC) are interconnected to compute and store electrical signals. Let’s take a closer look at the role of each class of component. Transistors act a switch that turn power on and off, while capacitors build up and store electrical charge. Resistors regulate current flow, and diodes keep the size of the signal uniform. A semiconductor integrated circuit is manufactured by integrating all the elements in a circuit into a fine and intricate multi-layer pattern. These fine circuits are impossible to draw in manually, so instead a method similar to that used when developing photos is used. We’ll get to that in Part 4, where we’ll discuss photoresist.

The development of the integrated circuit (IC) spurred the progress of the semiconductor industry. Switching from manually connecting individual components to integrated circuits meant smaller product form factors and lower power consumption while achieving faster data processing. Use of photograph developing techniques meant semiconductor ICs were reliable and conducive to mass production. In the 1960s, the late Korean-American engineer Dr. Dawon Kahng and Martin Atalla at Bell Labs developed the “MOS-FET” (Metal Oxide Semiconductor Field Effect Transistor). From this point on the integrated circuit truly shone. The MOS-FET was a solution addressing the limitations of the conventional bipolar junction transistors, which were hard to manufacture and consumed large amounts of electricity. In the span of 60 years, semiconductors have come from transistors to integrated circuits (ICs) and MOS-FETs. It’ll be exciting to see what further innovations the future will bring. Stay tuned for Part 4, where we will learn how these intricately designed circuits are drawn onto wafers.