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#sky130
Title
# sky130
k

Kevin Dai

11/09/2021, 6:44 AM
Does anyone know where the layout for
sky130_fd_bs_flash__special_sonosfet_star
is located? I've seen references to it in a project from MPW1
h

htamas

11/09/2021, 9:24 AM
I was also looking for that one. It seems to me that the flash cells were not open sourced yet. If they are like memory cells that can only go in their own build space, we'll have to follow https://github.com/google/skywater-pdk/issues/4.
I have the feeling that if the technology allows for flash cells, we should also be able to design things like a simple nonvolatile latch or flip-flop that's less effective but doesn't need its own build space. I wonder if there is enough publicly available info to do so.
t

Tim Edwards

11/09/2021, 2:30 PM
There is a device generator for the SONOS transistor in magic. It is just a normal nMOS FET device with a SONOS implant layer. The main issue we have is the lack of a library of cells for programming the SONOS, or any information on programming voltages, times, limits, etc. I happen to have a complete layout of a RAM block of SONOS that I obtained from SkyWater under NDA. It still does not come with documentation, but I should be able to reverse-engineer it enough to make some educated guesses.
The MPW-1 project used magic to generate the SONOS, but only had a couple of devices all wired out to pads so that they could reverse engineer the device by direct experimentation.
👍 1
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Kevin Dai

11/09/2021, 6:20 PM
Ah thank you, that makes sense! So I assume the "SONOS cells" section of "Device Details" in the PDK docs is not applicable. I have a random question about the tunm.5 rule "(poly and diff) may not straddle tunm" but I found the following layout below in MPW1. Not sure if I interpreted the rule correctly.