Embedded chip developers are facing a major challenge. Non-volatile flash memory no longer scales below 28nm, and there is no established alternative. For many years, this didn’t matter.
But now the development of in memory computing and neuromorphic AI architecture is driving significantly higher demand for memory on leading edge process technologies, Coby Hanoch, CEO of Weebit Nano tells Nick Flaherty of eeNews Europe.
One technology proposed for next generation microcontrollers is resistive RAM (ReRAM), which for Weebit has been in development for nearly a decade using technology from French research lab CEA-Leti.
“The world is going through a transformation that you can see with TSMC in a very clear way,” Hanoch tells eeNews Europe, which first covered the company back in 2016 when it licensed the technology from Leti.
“TSMC for a long time was pushing MRAM very strongly but they are converting to ReRAM. Out of six projects one is MRAM and the rest are ReRAM as they realise the customers don’t want MRAM. Even GlobalFoundries are getting more customers who are telling them they don’t like MRAM and TSMC is leading the camp.”
Weebit has been showing its technology on a GF wafer but last year signed a key deal with DB HiTek in Korea. The key is that the silicon oxide memory technology sits between the metal traces on the top of the chip and can be applied in the back end of line (BEOL) during assembly, making it much more cost effective than a process that needs to happen in a leading edge fab.
But this needs process development kits (PDKs) for those leading edge processes and implementations to demonstrate the reliability and performance of the devices as well as detailed integration of the materials with the chip making processes. “We have several PDKs at the FinFET level and we have demonstrated between 10 and 20nm and we actually can have good results,” he said.
This has been shown by the tape out of a demonstration chip on a 130nm bipolar process at DB HiTek in Korea. The highly integrated demo chips will be used for testing and qualification ahead of customer production.
The chip was completed on-schedule as part of the technology transfer process following a deal last October and the two companies aim to have the technology qualified and ready for production by this time next year on a 130nm BCD process for analog, mixed-signal and high-voltage designs in applications such as consumer, industrial, and IoT devices.
“This milestone confirms we are proceeding towards qualification of our ReRAM in DB HiTek’s BCD process on schedule, making the technology available to this leading foundry’s extensive customer base,” said Hanoch. “We’re already in early adopter discussions with several DB HiTek customers who are interested in integrating ReRAM in their SoCs. One area of interest is smart power management integrated circuits (PMICs), where integrating the PMIC with the microcontroller on one die can lead to performance, security, power and cost advantages.”
The RISC-V demo chip includes a 1Mb ReRAM module that can be scaled to other densities as needed. This fully-integrated module also includes all necessary control logic, smart algorithms, decoders, IOs (Input/Output communication elements) and error correcting code. The module is designed with specialist analog and digital circuitry running smart algorithms that significantly enhance the memory array’s technical parameters and the chip integrates a full sub-system for embedded applications, including the Weebit ReRAM module, a RISC-V MCU, SRAM, peripherals and system interfaces including SPI, UART, JTAG and GPIO.
Once qualified, DB HiTek will add Weebit’s memory module to its BCD 130nm Process Design Kit (PDK). DB HiTek customers can use the standard modules in the PDK or have modules customized for their needs. But it is the larger foundries that Weebit needs to persuade.
“GlobalFoundries are not offering our technology to customers and they are working on a different ReRAM, CBRAM, but we are manufacturing on their wafers.” GF is also working with Fraunhofer IPMS in Germany to investigate new embedded technologies, including Resistive RAM.
“It’s something that is very standard working with a new foundry,” he said. “Transferring the technology to them can take nine months or so, and we are doing it now with DB Hitek, The first phase of testing is making the wafers, Leti adds the ReRAM and then resat it for evaluation. They are not the only fab that they are doing it with.”
“Many foundries are big companies with internal politics and a million different considerations. They are trying to get their own to work and that’s a very big dfiffernce in the ReRAM space.”
“My job is to bring them customers that will ask for Weebit. We are trying to convince them to move forward to an agreement.
ReRAM for AI chip architectures
“There is a lot of work now on in-memory computing and neuromorphic computing and I think we have a great solution for it. You start off by replacing the SRAM with the ReRAM and you can throw away the flash. The next phase will be neuromorphic for people who want to do inference at the edge.”
“We have an 8Mbit chip on the GF 22FDX process and we know we can go up to 64Mbit very easily and we don’t see a limitation to 128Mbit on 12 or 14nm FinFET. We are using a 1T1R (one transistor, one resistor) architecture and its bit addressable.”
Larger memory arrays need a different architecture that can select lines of data.
“We are developing new selector technology and it will take some time to get it working but once we have a new selector technology we might be more efficient, we are working on several and I don’t know which one will win. Some disengage from the transistor and theoretically allow you to go 3D. Right now though Weebit is so focussed on getting the 1T1R process with foundries. We are working on it in parallel but the top priority is anything that can bring agreements and revenue with the foundries, with the IDMs.”
The company is also working with eFabless in the US to use the ReRAM technology at Skywater, tapping into funding from the US CHIPS Act. “We have also applied for a US Chips Act with Skywater with a customer,” said Hanoch. “If we win it, we will manufacture at Skywater. We are expecting to hear before the end of the year.
