Sidense NVM Scores Qualification on GLOBALFOUNDRIES 28nm SLP and HPP

A tremendous number of chips being designed for today’s products require some sort of onboard data storage. The size of these needs range from a handful of bytes, for trim and calibration storage, to something much more substantial like boot code storage. In both of these examples the storage ideally should be nonvolatile, with the option of writing during test and calibration, and possibly several more times over the life of the product. Furthermore, this capability should come with no additional process changes such as special layers or masks.

Design teams have several choices for their on-chip storage requirements. The simplest is mask ROM, but it sacrifices several of the useful traits called for above. First off, it must be made part of the mask when the chip is designed. This limits its use for calibration, unique ID’s or for microcode that might require updates. On the plus side, its useful life is extremely long, eliminating concerns about reliability.

At the other end of the spectrum is NAND flash memory. It often gets ruled out for on-chip uses firstly because it requires modifications to the process and adds additional masks. Also because its ability to retain data relies on storage of a charge in a floating gate, it is prone to errors after repeated writing or even reading. Therefore, for applications that require high reliability NAND flash memory can be a concern.

Because of these and other reasons another type of memory is used for frequently for on-chip storage. One time programmable (OTP) nonvolatile memory (NVM) offers many advantages for storing trim and calibration data, unique hardware addresses, encryption keys, and microcode. By using antifuse technology that selectively breaks down gate oxide, it avoids the potential localized physical damage issues that come from ‘blowing’ fuses in conventional fuse technology. They have fast read times that can make them suitable for code execution use. And, the available storage can be managed to provide the functionality of “few times programmable”. Of course they cannot compete with the re-write levels of NAND flash.

Even though OTP NVM uses conventional CMOS process layers and masks, it needs to be qualified for a given process to ensure the antifuse devices work with during the program and read operations.Sidense, a leading supplier of OTP NVM, has just announced that their SHF family is now qualified on GLOBALFOUNDRIES’s 28nm SLP and HPP processes. 28nm is fast becoming one of the most versatile and widely used process nodes. This is due to its low relative cost and flexibility. The 28nm node is being used for a broad range of products, including networking, wireless, automotive and IoT.

Sidense says their SHF family is available on a wide selection of processes in sizes from 1 Kbit to over 1 Mbit. This makes it suitable for calibration data, encryption keys, ID tags and code storage. This family uses a so called 1T, or one transistor, bit cell to save space and simplify design. SIdense points to the SHF family adoption for use in HTDV processors, PMIC’s, wireless chip sets, and communications and network processors.

Qualification of OTP NVM architectures on a specific node is a significant undertaking that involves cooperation between the foundry and OTP vendor, in this case, GLOBALFOUNDRIES and Sidense. After the design of the bit cell, all the other OTP NVM supporting IP needs be implemented on the target node. This includes the integrated power supply (IPS) that helps eliminate the needs for external supply pins and routing for the programing voltage by generating the necessary voltage internally using the chip supply. On top of this there are addressing and interface blocks in RTL that support the OTP memory core.

Test chips were run at GLOBALFOUNDRIES and then characterized for performance and reliability. After silicon results verified performance of the Sidense SHF family OTP NVP, the two companies announced completion of the qualification process. OTP NVM is one of those things that by itself does not garner a lot of attention. However it is a key enabling technology for many of the growing applications of semiconductor products. Having OTP NVM available on new nodes is ultimately critical to the advancement of many end user products.