Can you help to use M0 or V0?

[selldream2]

Patrick,

I may do M1 usage as M0. However, it would be more convinient to use M0 layer.

Can you help to release Metal layer constraint to need metal 1 as bottom layer, like allow M0 or V0?

Sincerely

billy

[patrickschulz]

Hi Billy,

why do you need this? generics.metal(1) is not M1, it is the first metal. So in your case generics.metal(1) is M0. The whole point is to have an abstraction over the process-dependent stack.

Kind regards,
Patrick

[selldream2]

Thanks. But as you know, M0 and V0 are the popular description. Already, I try to use M1 as M0 in via file, but it looks not consistent with the existing documents like design rule. also I do not recognize you define M1 is 'first metal'. First metal can be M0.

[patrickschulz]

Hm, I don't know that M0 and V0 are the popular description. The nodes I know start with M1 or even something else (MET1 for instance). Furthermore, several nodes I know even deviate from the Mx names and use entirely different names, say GB for a metal. This means that this is a perfectly valid (and necessary) layer mapping:

M3 = {
    name = "GB",
    layer = {
        gds = { layer = 42, purpose = 0 },
    },
}

The via to this metal might be called XF (I'm making up random names), but the via definition still needs to read be viaM2M3. This is the way it is.

Please note that I do not define M1 as first metal, I define generics.metal(1) as first metal. Yes, in the layer map file this falls back to M1, but that might be subject to changes in the future, perhaps the mapping need to be defined as generics.metal(1) = { ... }. I don't know yet. But this should not be a problem. Ideally, you define your technology mapping, perhaps tweak them a little in the beginning and then don't change them anymore.