A Static RAM Says Goodbye to Data Errors

The immunity comes from two extra capacitors in each memory cell

3 min read

When a neutron, alpha particle, or some other ionizing particle strikes a solid-state memory chip, it can do a good deal of mischief by changing the data stored in a memory cell. Stray ionizing particles can come from cosmic radiation or from minuscule amounts of radioactive impurities in the material used to make the chip. Their random appearance can lead to system malfunction or even failure if critical erroneous data or instructions are sent to the processor. But such events never do permanent damage to the memory: when new data is written into the same cell, it will work just fine. For this reason, errors caused by ionizing particles are called "soft."

Fifteen years ago, soft errors emerged as a problem for dynamic RAMs, which store data in a single capacitor. But static RAMs, which store data in more complicated and sturdy six-transistor cells, were not especially vulnerable. However, as transistors have become smaller and smaller, soft errors have become a concern even for SRAMs.

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Emily Cooper
Green

Perhaps the most far-reaching technological achievement over the last 50 years has been the steady march toward ever smaller transistors, fitting them more tightly together, and reducing their power consumption. And yet, ever since the two of us started our careers at Intel more than 20 years ago, we’ve been hearing the alarms that the descent into the infinitesimal was about to end. Yet year after year, brilliant new innovations continue to propel the semiconductor industry further.

Along this journey, we engineers had to change the transistor’s architecture as we continued to scale down area and power consumption while boosting performance. The “planar” transistor designs that took us through the last half of the 20th century gave way to 3D fin-shaped devices by the first half of the 2010s. Now, these too have an end date in sight, with a new gate-all-around (GAA) structure rolling into production soon. But we have to look even further ahead because our ability to scale down even this new transistor architecture, which we call RibbonFET, has its limits.

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