[Layout] Metal and other layers

Hello All,

I know there are Metal layers in the Layout... Should they be used for the routing?

What are other layers (besides GND and Power)? How many do exist?

When people say "7-layers design", do they mean "a design with 7 metal layers"?

When layout people say "mask", what do they mean?

Thank you!

Should they be used for the routing? - Yes, they must be used for routing.

What are other layers (besides GND and Power)? - No such layers as GND and Power. there are such nets/wires/straps/rails with names as GND or Power. and these objects are in metal layers (and in diffusion layers and in some others)

How many do exist? - the common layers are NWell, Diffusion, Poly, Via and some more (simple transistor = Nwell+Diff+Poly). For example, for 90nm the standard layer mask set for 9 metal layers is equal to 38 layers.

When people say "7-layers design", do they mean "a design with 7 metal layers"? - Yes. Still sometime it may refer to 1 poly + 6 metal.

When layout people say "mask", what do they mean? - they mean IC photomask, which is used for chip fabrication. For example, mask layer will be transformed to metal mask, while some other mask will be derived from several layers. It depends from foundry.

oratie,

nets/wires/straps/rails

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Could you explain please what's straps and rails?

No such layers as GND and Power

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Someone told me that the topper layer is a Power Layer... Is it not correct?

As for the Analog Signals, should them be routed in a separate Layers (separate from Digital signals)?

Thank you for your great comments!

Could you explain please what's straps and rails? - just a name for power/ground straigth wires.

Someone told me that the topper layer is a Power Layer... Is it not correct? - the topper layer usually used for power/ground, but also and for other critical wires (like clock).

As for the Analog Signals, should them be routed in a separate Layers (separate from Digital signals)? - no, we use the same layers for digital and analog. Sometimes, analog wires may require special routing rules (like non-minimum wire width, non-minimum spacing between wires, some kind of shielding).

Could you explain please what's straps and rails? - just a name for power/ground straight wires.

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Straps are GND and rails are POWER or vice versa?

No, rails are horizontal lines in Metal1 both Power and Ground (and std. cells are placed on them and connected to them). And straps are in higher metals (also both Power and Ground), they may be horizontal and vertical, thay may be in several layers, and they are needed to transmit and distribute regularly external chip supply from I/O cell (pads) to rails and to other macro cells (like embedded memories).