Define Embedded Memory

By Linh Hong, Kilopass Technologies Inc.

Nonvolatile memory (NVM) isn’t a term that easily rolls off the tongue—or one, perhaps, that offers an easy explanation. Even so, it’s an important component of almost all systems-on-a-chip (SoCs) in use today. We estimate that the serviceable, addressable market for embedded NVM will be $500 million by 2015. You’ll find NVM in automotive, analog/mixed-signal, and consumer devices as well as media processors and industrial and mobile –– both handheld and home baseband –– electronic products. High-security applications, such as mobile banking and conditional access, are adopting NVM too. What’s more, embedded NVM is silicon proven at process technologies ranging from 350- to 40-nm and beyond.

Think of NVM as an on-chip code-storage locker. After all, it’s used for firmware and security code storage, calibration data, and other application-critical information—not just the ID of older memory technology.

Advancements in embedded-memory technology are expanding the market for serviceable, addressable embedded NVM. Innovation is enabling large-capacity solutions to store firmware and boot code that were traditionally stored in external discrete memory—including serial EEPROM and NOR Flash. Embedded NVM is fast replacing popular and widely used memory chips because it can be integrated on chip, providing both savings and greater protection from unauthorized access.

That’s right. By integrating embedded memory into an SoC, memory intellectual property (IP) eliminates the cost, power consumption, and space of external memory—all the while helping to reduce bill-of-material costs. Consider that an estimated 30% of the $6-billion worth of EEPROM and serial-Flash chips shipped in 2010 was used in applications that required capacity to 4 Mbits.

Imagine what a designer could do with an extra 4 Mbits of NVM. With embedded memory, he or she could easily increase performance by 8X over a discrete solution without sacrificing power or area due to an increased I/O pin count.

Poor scalability and reliability from one process technology to the next is a thing of the past and a limitation of traditional embedded memory. Embedded nonvolatile memory easily integrates into an SoC using standard CMOS process technology—a key reason for its widening adoption. New NVM uses standard CMOS manufacturing processes and scales to meet embedded-memory size and complexity challenges, which are growing exponentially as SoCs migrate to 28 and 20 nm. Reliability can be achieved without additional wafer bakes to guarantee 10-year data retention. Gone, too, are capacity limitations below 128 kb.

A few different embedded-NVM technologies are available today including mask ROM, floating gate, electrical fuse, and antifuse. Mask ROM is the lowest-cost and highest-performance solution. But the content needs to be known before manufacturing, limiting the content that can be stored in a ROM.

Floating-gate technology is the most flexible with potentially up to 10,000 cycles of endurance. But it’s also the most costly solution. Unless you need NVM that consumes 30% to 50% of your die, it doesn’t make sense to eat the 30% to 40% cost adder associated with floating-gate technologies.

Electrical fuse is readily available from the foundry. But these memories are only suitable for low-capacity solutions, as they’re available to 1 to 4 kb. Also, electrical fuse isn’t portable from one foundry to another. As a result, it isn’t well suited for the multi-foundry strategies deployed for high-volume products.

Antifuse—a one-time-programmable (OTP) memory technology—has been in the market for several decades. Additional process steps were required, however, to create the memory element or bitcell. Kilopass was able to implement antifuse technology in standard CMOS in 2001 without additional mask or process steps. The technology scales with process and is portable from foundry to foundry because no special process steps are required.

Reliability and flexibility are hallmarks of embedded memory. Such aspects help design teams differentiate their products while allowing them to quickly adapt to market changes. By integrating embedded memory into the SoC, design teams worldwide also have found that they’re eliminating the cost, power consumption, and 4 Mbits of space taken up by external memory.



Linh Hong is vice president of marketing at Kilopass, and has 13 years of semiconductor industry experience. She began her career as a component engineer at Sun Microsystems. Hong holds a bachelor of science degree with honors in physics and a master of science degree in electrical engineering—both from University of California, Davis.