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Metal in unidirectional????

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Hello

Can anyone pls tell me, with reference to drawing layouts, wat do you mean by metal1 or any metal in unidirectional or bi directional??.. Does that mean that metal if defined unidirectional(eg. horizontal) can make a connection only in the horizontal direction ????


Thanks in advance

BB
 

Hi,

Assume that you have 2 metals layers available, let's say M1 and M2.
You have 3 solutions to route your design:
1: M1 bi directional and M2 bi directional (looks lije a 2-sided PCB !)
2: M1H and M2V : it means that M1 path will be ONLY horizontal and M2 paths only vertical, with vias at interconnections. To connect 2 points, several segment of M1 and M2 may be necessary.
3: M1V and M2H : it means that M1 path will be ONLY vertical and M2 paths only horizontal, with vias at interconnections, idem

This is very used in hierarchical analog design and in digital : when you integrate a sub-cell in a larger design, you know what metal to use according to the position of point to join.
 
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Thanks gag2000.. so u mean to say dat..if suppose metal1 is uni in horizontal.. to make a connection its possible only if i put a via wid me1 in horizontal direction?? ..
 

Have a look to the example. M1 is blue (H) and M2 is yellow (V).
To connect A to B, you need 3 paths: M1_1, via, M2_1, via and M1_2 M1H_M2V.png
 
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How do u know if a metal is set for uni or bi directional?
 

That is your choice (wrt to the choices of the whole design team) if there is no specification in design rules.
 
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thanks gag2000!! ... i have another question..it wud be great if u could help me!... can u explain how to placea poly between the grids and some other metals on vertical grid or horizontal???

Thanks in advance

BB
 

I'm not sure to understand your question...
In general, I avoid using poly as routing layer due to high capacitance to substrate and high resistivity. When I exceptionally use it for routing, I do not care about H or V, it is just for local interconnection. But you can imagine (if your design is compatible with and if transistor orientation allow it etc.) having Poly in H, M1 in V, etc.
 

The only time I've seen reference to "directionality" in relation
to metal, is its current-flow profile and choosing electromigration
current density limits appropriately.

The metal itself is nohow directional. Your choice about how to
assign routing channels / axes, might be.
 

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