Uncovering the Silicon: Demystifying How Chips are Built and How They Work

hi my name is Wendell Oski I'm here with my friends at Maker Faire Chuck John McMaster Ken sure if Eric slipper and Lenore Edmond and we have a project that's called uncovering the silicon in this project what we're doing is taking a very simple old integrated circuit we're gonna walk you through the entire process of understanding how it works by looking under the microscope and relating it back to the macroscopic behavior of the chip so let's start with the chip this is a part produced by Fairchild in about the late 1960s early 1970s it's a dual dual to input nor chip it's a little octopus looking can with eight legs got pins one and two hooked up to these buttons these are inputs my press it the input goes high and I press either one of these or both of these the output goes low does this is an or gate we also have a second or gate on here and the pins are numbered around in a circle one two three four five six seven eight we have pins one and two are the inputs a and pins three and five are input speed in 6 and seven are outputs and power and ground are pins 8 and 4 respectively so our collaborator John McMaster took one of these chips and with great effort and skill D capped it remove the epoxy from the top so that we can now look at it under the microscope the actual piece of silicon inside is about one millimeter square we have it under higher magnification here so the purpose of our project is to take this image that you're seeing on the microscope and ask the question what are those parts and how does that relate to the macroscopic behavior how do we get from this image that you see on the microscope here to that nor gate behavior so let's start with a still image from the microscope this will be a little easier to see because it's holding still this structure up here is an individual transistor it's an NPN bipolar transistor and I have a little acrylic model of it here in my hands this has three parts a base emitter and collector and if I put on a little lead frame that connects to them you can see with a label which those parts are so the base drawn here in yellow the emitter is in red the collector is also red the emitter is embedded into the top of the base and if you look at this sideways it's actually a little more accurate because this is a planar device that's really NPN top to bottom at the bottom we have the collector here in red a gap and then we have the base here in yellow and perhaps you can see it but the emitter is embedded into the top of the base and doesn't go all the way through so now that you can identify one transistor let's look at what the entire chip looks like this is an acrylic model of the entire chip and you can recognize that one transistor that I was pointing at before but there's also a lot of other stuff going on first of all there are the wire bonds which is how this connects to the outside world these are our pins 1 2 3 4 5 6 7 8 and if I take off the wiring and the metal layer you can see the silicon underneath here's that transistor but if we look carefully we can see more of these there's 1 2 3 4 5 6 transistors the only other component found in this type of IC is actually a resistor this here this little dog cone shape that's one of the resistors it's a piece of slightly conductive silicon and if you were to imagine wiring up wires to either end of it it would conduct but not great which is why it's a resistor so now that we can identify those two parts let's put the lid back on and trace how this thing works in one again one of my inputs goes to this resistor and that goes to the yellow thing to the base of my transistor into goes through another resistor and then to the base of a second transistor and if you trace the wiring from there you'd find that the two emitters a little embedded red part the two emitters of these two chips are wired together and that those are wired further to pin 4 which are ground pin on the other side our collectors of these suit transistors are wired together here and those we can trace out to pin 7 we write down a circuit diagram of that it looks a bit like this that's this part of the chip that I've just shown you right here there's two inputs each of which goes to a resistor and then each of those goes to the base of a transistor and on those two transistors the two emitters are wired together and to ground the two collectors are wired together and that's to the output so in loose hand-waving terms when you apply a voltage to either of these two input transistors it turns on that transistor and pulls down this point the collector to ground and that's our output so if either input is high our output is low and that's how this nor gate works and our hope is once you've been through that once you trace that you can go back and look at this microscope picture and you can trace this on your own because you now know what you're looking at

Channel: HACKADAY

Views: 196,831

Rating: 4.9652214 out of 5

Keywords: Maker Faire Bay Area, Integrated Circuits, Silicon design, chip design

Id: VNzkhZBjo5k

Length: 5min 25sec (325 seconds)

Published: Mon May 20 2019

Reddit Comments

[u/EasyFixed]

This was great, though I'm left feeling the need for much more information. Anyone know of any other great videos that are along this vein?

[u/elocmj]

I've learned nothing

[u/---E]

Interesting, but a bit too engaged for a meal time video imo. It requires too much attention.

[u/DeathPunchRonaldo]

I thought you just had to fry a tortilla and put some ingredients and cut it into triangles

[u/letsgocrazy]

Sorry, but there were just some massive gaps in what he was explaining.

• What is a NOR gate?
• Why does sending in some signals and getting other signals out matter?
• What are those collectors doing?

I totally got that that circuit board was a bunch of resistors and transistors that are doing something with electrical signals - but what? and why?

How is that like a computer?

[u/marsmedia]

OK, I see: actuating the norgate attenuates the inductive flow of electrons through a conductor causing a surge of radiant particle flow through a semiconductive/semiresistive medium reticulum benzoate formula adjunct perfunctory systematic colonic martyrdom bombastic seizmotic sephamorical transmisionator.

[u/Spooms2010]

That was a bit of a chalk to understand but I think I can see what he means...I think. I’d have to ask a number of questions first but thanks for this anyway.

[u/[deleted]]

I think the key thing to understand is that those square things stop the current from magically crossing over to the other side of the glass if they're activated. And I don't think resistors actually do anything, just the union requires they be put in.