Question: What is a soft error (SE)? How do SEs affect semiconductor devices? What are the causes of SEs?
An SE is a random, non-recurring change of state or transient in microelectronic circuits due to energetic nuclear particles interacting with the silicon. When a high-energy particle hits the silicon substrate, the kinetic energy of the particle generates electron-hole pairs as it passes through the p-n junctions. Some of the deposited charge will recombine to form a very short-duration current pulse, which causes an SE. In memory elements, these current pulses can cause bit flips (i.e., data ‘1’ becoming data ‘0’ or vice versa).
An SE may result in a single-bit upset (SBU) or in a multi-bit upset (MBU). An SBU is a type of radiation-induced upset identified when a flipped bit is physically isolated from other possible events and the physical separation from any other flipped bit is at least two memory cells. An MBU is a type of radiation-induced upset identified when two or more flipped bits are physically adjacent or have a separation of, at most, one non-failing bit.
The major causes of soft errors in semiconductor devices are thermal neutrons, alpha particles, and high-energy neutrons:
For more information, refer to the following KBAs: