Renesas Electronics has developed a new circuit technology for automotive information devices using 16nm and more advanced process technologies. The company prototyped SRAM by using the new technology and Taiwan Semiconductor Manufacturing Co Ltd's 16nm FinFET process as cache memory for CPU cores of SoCs and real-time image processing blocks. And it confirmed that the SRAM operates at a speed of 641ps (picoseconds) with a voltage of 0.7V.
The japanese company developed a FinFET-compatible circuit technology that can stably read and write data with a low voltage.
A new circuit technology was developed using the "word line overdrive" method, which realizes high-speed reading and writing at the same time with a low voltage. As the process is scaled down, the lowest operating voltage deteriorates due to the variation of elements. As a result, an assist circuit is used to solve the problem. It improves operation stability at the time of reading data by slightly lowering the voltage of word lines.
However, with this method, the operation margin deteriorates at the time of writing data, and the reading speed lowers.
So Renesas developed an assist technology that takes advantage of the characteristics of FinFET and slightly increases the voltage of word lines so that the pulse width at the time of reading data becomes different from that at the time of writing data. As a result, it became possible to realize high-speed reading while ensuring an operation margin at the time of reading and writing data.
Second, Renesas developed a design technique in consideration of the variation of FinFET elements, which is different from the variation of the elements of planar MOSFET. For example, at the center and edges of an array of memory cells, an offset occurs to the bit line current at the time of reading data, generating a current difference. As a result, it becomes impossible to ensure a sense amplifier margin at the time of reading data, potentially making the device malfunction.
Renesas quantitatively measured the current offset with the prototyped chip. And, based on the measurement results, it enabled to finely adjust circuits and ensure an optimal operation margin. As a result, it becomes possible to realize a high reliability required for automotive information equipment, the company said.