How do they design/create chip with billions of small transistor?

Question

When we talk about a chip, we often think about it having a really complicated circuits, like the Apple M2 where it has 20 billions of transistors and etc. Back in the days, chip weren’t that complicated so I could digest that they could design it. But nowadays since they’re more complicated, do they really design it when they’re very small like nanometer level?

Ps: I’m not a computer engineering student but feel free to use some technical terms if needed since I take related course to this.

In: 13

Answer 1

There are varrying levels of ‘abstraction’ that VLSI engineers use to build these computers.

You start out at the device level, which is literally 1 transistor. You design it to have a specific width, area, etc to match some form of equivalent reisstence and current capability.

Then you move up a level and put that device into a circuit. The easiest of which is the CMOS inverter. Its 1 PMOS and 1 NMOS transistor tied together. Plenty of resources online to read up on, and I highly recomend you get started there. Its what most college courses use to introduce the CMOS concept.

Now you’ve made a small circuit that could represent a single AND, NOR, XOR, etc gate. You build a component using the abstact symbols for gates to build a component. Examples of these are adders, multipliers, flip flops, etc.

You then use these larger absteact symbols to build modules, such as the ALU, Cache, Control & Decoder units, etc.

Then you use these to build your larger system. Place cores, memory, etc and thats the schematic done. So schematic designers aren’t going in and placing individual transistors on their schematic, thats done for them using design tools.

The actual layout of the chip has many more factors to consider. How many layers are there, how many metals, how big of a chip, the package of the chip, what metals, what size node is there, etc etc. I’m also not a layout engineer, my experience is much more on the analysis side of things, so I can’t really give too much insight on that side of the fence, hopefully someone else chips in.