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How can I know the exact No. of transistors in my chip before fabrication and after fabrication? It is possible to count transistors using LVS (Layout Vs. Schematic), but its valid for Final Layout or netlist. How to count/examine the same after fabrication.

Answers will be appreciated.

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    \$\begingroup\$ Even if it was possible, it's not really practical. There can be billions of transistors in a single IC. \$\endgroup\$ – DerStrom8 Nov 20 '17 at 12:10
  • \$\begingroup\$ Yes, But What if I could count to make it signature? I can use it for any purpose. \$\endgroup\$ – Qazi Arbab Nov 20 '17 at 12:14
  • \$\begingroup\$ I'm not sure I understand what you're asking....? \$\endgroup\$ – DerStrom8 Nov 20 '17 at 12:17
  • \$\begingroup\$ What do you mean by "your" chip? \$\endgroup\$ – Finbarr Nov 20 '17 at 12:24
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    \$\begingroup\$ What do you mean by "make it signature". Normally IC designers include some text to identify the chip. Number of transistors is also vague. If I have a large NMOS split in 10 fingers, is that one transitor or 10? And if I have another one in parallel does that make for 1, 2, or 20 transistors? \$\endgroup\$ – Bimpelrekkie Nov 20 '17 at 12:37
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It sort of depends on what you mean by 'layout' - for example you could extract rectangles where poly layers cover P or N diffusion

For example in the nand gate example here the green over yellow and green over pink rectangles are each a transistor

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  • \$\begingroup\$ Yes, But for an adder 's layout. I want to have signature, just to check how many transistors are there so that I can compare, once the chip is fabricated. \$\endgroup\$ – Qazi Arbab Nov 20 '17 at 12:40
  • \$\begingroup\$ check how many transistors are there so that I can compare, once the chip is fabricated Explain WHY that would be needed. I have designed ICs for 25 years and never have I done that or seen anyone else doing that. Do you think the fab secretly adds/removes transistors? You check your design through LVS (Layout vs Schematic) and that's it. Once you have the chip, you measure functionality. The number of transistors will be equal to how many you designed to be there. \$\endgroup\$ – Bimpelrekkie Nov 20 '17 at 13:29
  • \$\begingroup\$ Yes, the idea is the same, what if Fab adds/or removes transistors? Also, if the functionality remains the same, but the alteration could effect later on . i.e reliability? LVS is to check before fabrication, but after fabrication, how should I know the same? \$\endgroup\$ – Qazi Arbab Nov 20 '17 at 13:45
  • \$\begingroup\$ what if Fab adds/or removes transistors? So you expect them to mess with your design? Suppose you (or your company) spends 1 Million US$ on a maskset, chips are made, the design comes back and doesn't work because the Fab removed some transistors. Who's to blame? You or the Fab ? So guess what: The Fab will NEVER change your design. They might require you to make changes but they will not do it for you. If they would they also take responsibility for the design, which is your design. They would be stupid to touch it. \$\endgroup\$ – Bimpelrekkie Nov 21 '17 at 19:46
  • \$\begingroup\$ All the Fab does is make chips from your design. Nothing more, nothing less. So your checks for number of transistors is pointless as your design is how you made the layout and that's it. The number of transistors or how they're connected will not be changed by the Fab. \$\endgroup\$ – Bimpelrekkie Nov 21 '17 at 19:49

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