Embedded Non-Volatile memory modules for low voltage and high temperature applications

The existing embedded nonvolatile memory technologies have failed to deliver a cost effective solution for SoC applications. The major reason has been that most of these technologies were not designed specifically for the embedded applications. There have been two approaches for the embedded nonvolatile memories. One is to take the high density stand alone memory technology and use it for embedded applications and the other is to use the basic logic technology and make a nonvolatile element on it without adding additional masks. Both these approaches have their pros and cons. The first approach gives a very small cell size, but it has high cost, low yield, and compatibility with base CMOS process problems, while the other approach gives a very large cell which can not satisfy the density requirements. The embedded nonvolatile memory technology and modules described in this paper are designed from ground up by keeping the embedded applications and their requirements. Two (4K times 16) synchronous and asynchronous embedded nonvolatile memory modules have been developed using a simple p-channel E
²
PROM cell and technology. The module size is 1.22 mm times 1.12 mm and the cell size is 2.925 mum times 1.95 mum. The E
²
PROM cell is designed for very high reliability with more than 80% coupling ratio. High sort yields, high data retention, high endurance and simple process were the goals for this work. This technology is capable of delivering both the flash as well as the E
²
PROM memory architectures. The module functionality has been verified from -55degC up to 180degC. Consistent yields of more than 97% have been seen on several lots