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Antenna Diodes in the Pentium Processor

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Re: Antenna Diodes in the Pentium Processor

#11

Post by kens »

anonymous_user9 wrote: post #8
pclmulqdq wrote: post #7

Fun fact about "antennas" in chip manufacturing: They have nothing to do with actual antennas. Charge can build up on long wires during manufacturing because the chemicals involved are not neutral and have some interactions with exposed wires. That charge needs to go somewhere to protect the rest of the circuits. There's nothing RF about this. Later technologies (28 nm and below) have extensive design rules around pr…

I think that’s incorrect. The article and the Wikipedia page on the antenna effect say antenna effects are caused by plasma etching, which uses RF to create the plasma.

It's a bit confusing. The plasma is created by RF, but the RF doesn't cause the antenna effect (nor do "chemicals"). The charged ions and electrons in the plasma are what cause the charge buildup. The wire acts as an antenna in a metaphorical sense, not a literal sense, as I mentioned in Footnote 3.

Re: Antenna Diodes in the Pentium Processor

#12

Post by iakov »

kens wrote: post #2

Author here: I know this is a very obscure topic, but hopefully it will be interesting to some. Let me know if there are any questions...

Your pictures give insight into such a small world, individual freaking transistors on a CPU chip! Reading textbooks and wiki is one thing, but seeing silicon spliced up and photographed up close is another. Very interesting read, and very well presented too, thank you.

Re: Antenna Diodes in the Pentium Processor

#13

Post by lizknope »

I was following this discussion on the /r/chipdesign subreddit when Ken posted there a few days ago. Nice to see that he gave credit and linked to that thread.

I'm a physical design engineer that uses software from Cadence and Synopsys to do chip layout of blocks with billions of standard cells. Our flow automatically puts antenna diodes in for all block input pins. Then the tools are usually good enough to breakup internal nets with layer jumping to avoid antennas.

Some of the charge also comes from the CMP process. Modern chips have about 20 layers of metal but there are lots of other via layers in between those and then all the base layers with the actual transistors. You want the wafer to be flat before building the next layer.

https://en.wikipedia.org/wiki/Chemical-mechanical_polishing

Re: Antenna Diodes in the Pentium Processor

#14

Post by beenBoutIT »

iakov wrote: post #12
kens wrote: post #2

Author here: I know this is a very obscure topic, but hopefully it will be interesting to some. Let me know if there are any questions...

Your pictures give insight into such a small world, individual freaking transistors on a CPU chip! Reading textbooks and wiki is one thing, but seeing silicon spliced up and photographed up close is another. Very interesting read, and very well presented too, thank you.

It'd be interesting to see how big a CPU chip scaled up to be big enough for a human to fit in (were it hollowed out) would end up being.

Re: Antenna Diodes in the Pentium Processor

#15

Post by accrual »

Very cool that this would be on the front page after I picked up a Pentium-75 from my local recycler today, it's an SX969. I can hold this chip in my hand and look up to see Ken's die shots. So cool! The ceramic package these Pentiums came in are pretty unique as well - it kind of sounds like setting a piece of glass down when I set the CPU on my desk.

Re: Antenna Diodes in the Pentium Processor

#17

Post by emmelaich »

danecek099 wrote: post #16

I'm fascinated by the fact that we study this 31 year old technology and are amazed by the complexity

Indeed! A thought experiment I have some times is to imagine that every machine on the earth was destroyed overnight. We still have mines, people, books. How long would it take to get back to the level of industrialisation and science that would allow us to make (in this case) a 3 million transistor chip?

The vast majority of people have little idea of how much intellectual effort has gone into the current state of technology.

Re: Antenna Diodes in the Pentium Processor

#18

Post by namibj »

beenBoutIT wrote: post #14
iakov wrote: post #12

Earlier quoted context omitted.

Your pictures give insight into such a small world, individual freaking transistors on a CPU chip! Reading textbooks and wiki is one thing, but seeing silicon spliced up and photographed up close is another. Very interesting read, and very well presented too, thank you.

It'd be interesting to see how big a CPU chip scaled up to be big enough for a human to fit in (were it hollowed out) would end up being.

They're usually 150μm thick. Humans fit in about 300mm thick spaces, so you need 2000x linear scale.

Re: Antenna Diodes in the Pentium Processor

#19

Post by emmelaich »

beenBoutIT wrote: post #14
iakov wrote: post #12

Earlier quoted context omitted.

Your pictures give insight into such a small world, individual freaking transistors on a CPU chip! Reading textbooks and wiki is one thing, but seeing silicon spliced up and photographed up close is another. Very interesting read, and very well presented too, thank you.

It'd be interesting to see how big a CPU chip scaled up to be big enough for a human to fit in (were it hollowed out) would end up being.

Not to answer your question exactly but ...

Chips seem to be around 25mm sq, and the smallest features around 10nm. If you scaled up so the smallest feature is one mm then the chip would be around 2.5km square. (over 1.5 miles on each side)

If the smallest feature was about the width of human hair then divide the above by 100.

Re: Antenna Diodes in the Pentium Processor

#20

Post by accrual »

kens wrote: post #2

Author here: I know this is a very obscure topic, but hopefully it will be interesting to some. Let me know if there are any questions...

Hi Ken! Your work is extremely interesting to me and I admire the effort your pour into these articles. It's been very cool to see your die analyses ramp up to more and more complex chips over the years. The Pentium is an especially neat target since it represents a major shift in the x86 architecture towards the modern chips we have today. Never a dull moment when I see a righto link!
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