Microscopic view of an Intel i486

hello and welcome to micrographia an exploration of everyday items at the micro and nanoscale in the last episode we looked at the natural beauty of the common fruit fly compound eyes constructed from hundreds of segments claws that are sharper than hypodermic needles there's always a sense of awe when viewing the complexity of organisms at the microscopic level but nature isn't the only one to create beautiful microscopic structures we humans have gotten pretty good at it too while nature stitches together amino acids and creates phospholipid cells converting chemical energy into motion intent and purpose humanity has taken a more inorganic approach we grow ultra pure silicon crystals etch nanoscale features and evaporate heavy metals we stack these layers like an inorganic lasagna and feed our creations with a steady diet of electrons i'm talking of course about integrated circuits microchips and processors these little silicon marvels have transformed the world in just under 100 years today we are looking at an intel 486 processor the cpu was introduced in 1985 at a price of 950 in exchange for your hard earned wages you received a hefty piece of ceramics studded with tiny gold pins if you were to remove the protective metal cover as we are today you'd find a sliver of silicon no larger than a postage stamp and on that wafer over a million tiny transistors when viewed with a normal optical microscope you can see a vast array of lines snaking across the wafer these are aluminum interconnects microscale wires that serve as a global highway to information and power flowing across the wafer in between the aluminum are splashes of vibrant color this is light diffracting off the surface of the wafer or rather diffracting off the complicated stack of silicon oxides and thin metal films together these layers diffract light into a rainbow of colors that you see along the periphery are blobs of gold attached to delicate bonding wires these serve to move data and power onto and off the silicon wafer communicating with the outside world we can use a different instrument an atomic force microscope to understand how tall these aluminum interconnects really are this instrument scans a tiny probe across the surface collecting height information which can be converted into a three-dimensional model from this data we can see that the features are only about two microns tall and about four microns wide popular science media likes to use the width of a human hair as a size comparison but at around 80 microns i'm afraid we are well past that being a useful metric a human hair is just too large in comparison to these features a more appropriate metric would be the size of a bacteria which are just a few microns wide earlier i mentioned that integrated chips are stacked in multiple layers we move over to the scanning electron microscope we can begin to see some of that structure you might notice that the underlying layers influence those above it the surface is wavy where one trace passes over the other this seems counter-intuitive you'd expect the surface of a precision device like a silicon wafer to be ultra flat [Music] but in reality as layers are deposited one on top of the other the surface becomes increasingly rough as each subsequent layer distorts the surface a little bit more modern ships deal with this by polishing the surface periodically throughout the fabrication process but older chips did not require this as much as they're a lot less complicated the small circles you see scattered around are vias vertical plugs of metal that connect different layers together and while all the features feel very geometric and mechanical once you zoom in enough everything is slightly rounded and surprisingly organic feeling the truth of the matter is that it's just hard to manufacture precise right angles at the scale and everything starts to get a bit rounded we can switch to a different detector on the scanning electron microscope that allows us to peer beneath the surface a little better this allows us to see and map the underlying layers in better detail the 486 only has a handful of layers but modern cpus might have dozens stacked on top of each other i wanted to see if we could view the transistors themselves which would be buried at the very bottom of the stack but the only way to access this layer is by cutting the chip apart and grinding off the upper layers to get at the lower layer despite my best efforts the polishing process looks pretty crude at the microscopic level but crude attempt aside we can see some of the layers starting to emerge likewise a cross section shows some interesting details to help understand what's going on here we can enable a detector that identifies different atomic elements in our sample at the bottom is the silicon wafer as you'd expect but do you see how there is a dark area and a lighter area above it if we enable the oxygen layer we can see that it overlaps with the lighter silicon this is silicon dioxide two oxygens for every silicon oxide layers are used as an insulating layer in transistors because they're easy to grow on silicon enabling the aluminum overview shows the interconnects much more clearly finally there's a small amount of titanium if you look closely you can see that it shows up underneath the aluminum in a few different locations it sticks well to oxide and other metals like to stick to it so a thin layer of titanium is often deposited to help other metals stay in place or stick to surfaces they wouldn't normally like alternatively it may be a protective layer you see aluminum interconnects like to diffuse into the silicon layer over time which as you can probably guess is bad for your integrated chip to prevent this from happening a variety of different materials can be used as a sort of protective coating titanium is one such material although not very common nowadays so the jury's still out as to what the titanium is being used for here i wish we could have seen the transistors themselves but i'm afraid my polishing process is just not sophisticated enough to preserve them perhaps in a future video we'll get a chance to glimpse a transistor in its native habitat so that's the semiconductor process from 1985 is it as beautiful as a fruit fly i think so although in a very different manner it's a testament to scientific advancement and remarkable engineering skills developed by thousands of hard-working and brilliant individuals and to think this chip is over 30 years old i'm sure it looks almost childlike compared to modern integrated chips if you enjoyed this look at the microscopic world please consider subscribing or sharing the video with a friend if you have suggestions for future subjects to investigate let me know in the comments down below if you're an expert in 80 microchips please leave any corrections or interesting observations in the comments and i'll compile them into an addendum and as always thanks for watching

Channel: Breaking Taps

Views: 1,828,434

Keywords: intel, intel 486, i486, micrograph monday, micrographia, afm, sem, atomic force microscope, scanning electron microscope, micrograph

Id: U885cIhOXBM

Length: 8min 19sec (499 seconds)

Published: Sun Aug 15 2021

Reddit Comments

[u/schimmelA]

Oooh lovely microns, how expensive are these microscopes?