Hello, I am working on a design for the April 130n...
# sky130k
Kyle Castoria
02/17/2023, 7:10 PMHello, I am working on a design for the April 130nm tapeout (2304c). I was wondering if there is some way to know whether my design needs to conform to the aluminum or copper design specs. I was also wondering what the insulator material will be between the 5 metal layers. If this is the wrong channel for this question, please let me know and I will try again wherever I should be asking. Thank You!
j
Jecel Assumpção Jr
02/18/2023, 5:36 PMThe insulator material used in the fabrication of chips is SiO2 (glass). This was also used to implement the gates of the MOS transistors, but in more advanced nodes it got replaced by more exotic materials.
Jecel Assumpção Jr
02/18/2023, 5:40 PMAbout the "copper design specs", the thickness of each layer is due to how Skywater processes the wafers. It is the same everywhere on your chip and for all chips in a wafer - you have no control over that. How wide and how long the metal strips are depends on the GDS file you give Skywater, but there are rules about the minimum dimensions and the minimum spacing between the metal strips that you have to follow.
k
Kyle Castoria
02/18/2023, 7:35 PMThanks for the response, for our design, we must draw our own GDS file (and not use open lane or any hardening software). I see that the design rules are different depending on whether a flag is set to CU or AL. Maybe I am misunderstanding the use of that flag, but in the skywater documentation, there seems to be different limits for these two cases. That flag is set to AL by default so I have been using those constraints.
Kyle Castoria
02/18/2023, 7:43 PMhttps://skywater-pdk.readthedocs.io/en/main/rules/periphery.html#m2
I have been following these constraints, but for example there are two numbers listed for minimum gap length between Vias for via2.
j
Jecel Assumpção Jr
02/18/2023, 8:06 PMYou can't choose what material will be used for your metal layers. I think the Skywater 130 only uses copper while Skywater 90 uses copper for all but the top two layers:
https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhicsE_FrEV9hyy3wtzIhV-sw-tyzHzCW[…]AlK1XGTwrLkVTi_kjsApyH1_q/s856/Skywater%20Blog%202.png▾
🌍 1
k
Kyle Castoria
02/18/2023, 8:07 PMOkay thank you! I was not trying to choose which metal I use, I only wanted to be sure my drawing confirms to the correct design rules.
j
Jecel Assumpção Jr
02/18/2023, 8:09 PMNote that though both M2 and M3 are copper, in the link you gave you can see that M2 can have 0.140µm strips that must be at least 0.140µm apart while M3 can have 0.300µm strips that must be at least 0.300µm apart.
k
Kyle Castoria
02/18/2023, 9:37 PMI am a little confused. My link was to the skywater PDK (which I found by following the links from Efabless). It includes the attached drawing of the stack. The dimensions drawn here for layer thickness is different than in the picture you linked me above. Is my info not correct or out of date? If so, where can I find more accurate information?
j
Jecel Assumpção Jr
02/18/2023, 9:42 PMThis is the correct picture. The picture I gave the link to did not have the right proportions but was only showing the materials used.
k
Kyle Castoria
02/18/2023, 9:45 PMI see thank you very much