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#sky130
Title
# sky130
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Matthew Guthaus

08/05/2021, 2:24 AM
Does anyone know what material is LI made from? Is it a silicide poly? The resistance is closer to poly (1/4 of it) than m1 (100x more)...
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Rodrigo Wuerdig

08/05/2021, 11:27 AM
Hey! I've found this presentation online and it says that LI is made out of TiN http://ef.content.s3.amazonaws.com/FOSS_Stine_SoC_Final.pdf
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Matthew Guthaus

08/05/2021, 4:16 PM
@James Stine do you have any more reference or info on the TiN layer? I'm more interested in just understanding the manufacturing details
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Rodrigo Wuerdig

08/05/2021, 4:23 PM
Unfortunately, not. but I would like to know more about too.
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Matthew Guthaus

08/05/2021, 4:35 PM
James made that presentation, so I tagged him. He may know more...
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James Stine

08/05/2021, 4:37 PM
sure…will try to communicate more on it - still stuck away so will try to give more information. Will get back to you shortly.
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Rodrigo Wuerdig

08/05/2021, 4:37 PM
I didn't paid attention that you tagged him. Sorry
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James Stine

08/05/2021, 4:37 PM
np @Rodrigo Wuerdig
li or local interconnection is TiN - rest are Al. The li1 is 97.6x more resistance per square ohm than m1. My Ph.D. student @Teo Ene figured much of this out. We tried to avoid it due to this feature and got better performance on our cells. We avoided it by putting an obstruction in the LEF layer. That is, we provided all cell in/out pins on metal1 and prevent routing on li1.
better said - not an obstruction but just labeled li as a non-routing layer.
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Matthew Guthaus

08/05/2021, 4:43 PM
Yeah, I understand that (it was in my question). The question is about the processing of it.
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James Stine

08/05/2021, 4:43 PM
From what I understood, its left over from the previous process. Not sure about the processing other than TiN is an alloy
let me know if you were looking for something else - I probably missed something (sorry)
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Matthew Guthaus

08/05/2021, 4:45 PM
Yeah, I was more wondering if it is a TiN layer on top of poly or ... something else
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James Stine

08/05/2021, 4:45 PM
I think it even pre-dates the SKW acquisition
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Matthew Guthaus

08/05/2021, 4:45 PM
This is a purely processing question
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James Stine

08/05/2021, 4:46 PM
gotcha
As far as I know its an actual layer above poly - hold on I think have something on it somewhere
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Matthew Guthaus

08/05/2021, 4:46 PM
It could be a second poly with a different silicide (the TiN?)
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Rodrigo Wuerdig

08/05/2021, 4:47 PM
On slide 33 of that presentation there's a diagram. It's above poly
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Matthew Guthaus

08/05/2021, 4:47 PM
It's definitely above poly, yes
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James Stine

08/05/2021, 4:47 PM
I know I have something on it - will find
its a great question 🙂
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Matthew Guthaus

08/05/2021, 4:51 PM
I believe it is the same layer that IBM used to have "submetal" or "metal zero"?
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Rodrigo Wuerdig

08/05/2021, 4:52 PM
Sorry to interrupt the ongoing question. But what is the purpose of this layer actually (I am more familiar with other pdks)? Is it meant to avoid going M2 while doing intracell routing?
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Matthew Guthaus

08/05/2021, 4:53 PM
It's meant to be used in the local interconnect inside SRAM bitcells
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so that M1 and M2 can be used for wordlines and bitlines
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James Stine

08/05/2021, 4:56 PM
okay found it
so the TiN process is been around for a while - its typically used for high-precision metal element since its abundant. And, in the past its typically used for good analog designs which really defeats our purpose for digital. So, that’s one of the reasons I avoided
Ti is a great getter of oxygen so you can use it with TiO2 and TiN as a barrier
I believe some of my literature has this item being used for last 40 years
hope that’s what you were looking for - sorry it took a while
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Matthew Guthaus

08/05/2021, 4:58 PM
yeah, that's more useful
thanks
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James Stine

08/05/2021, 4:59 PM
np; always happy to help 😉
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Luis Henrique Rodovalho

08/07/2021, 2:34 AM
@Leonardo Gomes Read this thread. This explains the locali Ti layer.
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