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Internet search finds single vs double sided memory, here discussions are about Printed Circuit Boards (PCBs) for singe vs double sided. I'm interested to know if e.g. Intel processors, as they are printed on 2D die and AFAIK they are not 3D IC, do they have in-die wires only on one side (and hence the design should have no intersecting on 2D projection wires) or both?

P.S. I understand die is for fabrication, probably it does not have any wires at the time it is still called a die.

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  • \$\begingroup\$ the complexity of the circuit dictates that it has to be multi-layer \$\endgroup\$
    – jsotola
    Commented Oct 6, 2021 at 0:12
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    \$\begingroup\$ They're only on one side, but there are loads of layers of them. \$\endgroup\$
    – Hearth
    Commented Oct 6, 2021 at 0:25

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do they have in-die wires only on one side

Wires are only on one side of the die, but are layered one on top of another into a 3D stack:

Wikipedia BEOL article (taken from: https://en.wikipedia.org/wiki/Back_end_of_line )

In Intel's current 10nm process for example, there are 13 total metal layers interconnecting transistors. This article provides a detailed overview:

https://www.anandtech.com/show/13405/intel-10nm-cannon-lake-and-core-i3-8121u-deep-dive-review/3

The table "Intel's 10nm Metal Stack" is relevant.

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  • \$\begingroup\$ thank you. could you tell what is the value of 3D IC (wiki link in the qustion) if manufacturing already can make many layers on one die? I mean in wiki wires are called in-dei vs 3D wires so are this on your picture in-die, why can't more silicon layers be stacked same way as metal layers? \$\endgroup\$
    – Martian2020
    Commented Oct 6, 2021 at 1:37
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    \$\begingroup\$ @Martian2020 You're limited to essentially silicon transistors with metal layers on top of them. Stacking multiple dies lets you put arbitrary layers together, and the layer don't have to be made on the same semiconductor process. One of the main applications of stacking is putting memory chips on top of non-memory chips, which is useful since memory is made on special processes. \$\endgroup\$
    – user1850479
    Commented Oct 6, 2021 at 1:53
  • \$\begingroup\$ From what you written I understand metal layers are not part of original die, but added in the process even as they are called in-die? And that current stacking tech allows to add metal only? (otherwise why can't silicon layers be added same as metal...) \$\endgroup\$
    – Martian2020
    Commented Oct 6, 2021 at 2:30
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    \$\begingroup\$ @Martian2020 The die is made of silicon, while the metal layers are made of metal, so the metal layers have to be added on top (which is distinct from stacking). Growing silicon crystals on top of metal is very hard, so they start with the silicon already in place and then deposit other materials on top of silicon. \$\endgroup\$
    – user1850479
    Commented Oct 6, 2021 at 2:44
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    \$\begingroup\$ @Martian2020 I made the link explicit and rather than just saying Wikipedia. Not sure I've heard "in-die" used much, but the meaning seems clear enough. \$\endgroup\$
    – user1850479
    Commented Oct 6, 2021 at 3:04

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