Radiation-hardened memory element with multiple delay elements
View Patent ↗A radiation hardened memory element includes at least two delay elements for maintaining radiation hardness. In an example, the memory element is an SRAM cell. Both delays are coupled together in series so that if either one of the delays fails, a delay will still be maintained within the SRAM cell. The critical areas of the delays may be positioned so that a common line of sight cannot be made between each delay and a circuit node.
1. A method of radiation hardening a memory element having a feedback element, the method comprising:
positioning a first delay in a feedback path of the feedback element, the first delay residing in a first portion of a device plane;
positioning a second delay in the feedback path, the second delay coupled in series with the first delay and residing in a second portion of the device plane; and
positioning a component of the memory element in a third portion of the device plane so that the first, second, and third portions of the device plane are positioned such that deposition of charge from an incident single particle cannot occur in all three portions, thereby reducing a probability that the particle traveling through the device plane would cause an upset of the memory element, wherein two of the first, second, and third portions of the device plane reside in a common trajectory zone defining where a trajectory of the particle may disable or cause a particle induced state change in two of the first delay, the second delay and the component of the memory element, and wherein one of the first, second, and third portions of the device plane is located outside of the common trajectory zone.
2. The method as in claim 1 , wherein the first and second portions of the device plane reside in the common trajectory zone, and wherein the third portion of the device plane resides outside of the common trajectory zone.
3. The method as in claim 1 , wherein the first and third portions of the device plane resides in the common trajectory zone, and wherein the second portion of the device plane reside outside of the common trajectory zone.
4. The method as in claim 1 , wherein the first and second delays each have a critical area that is susceptible to a deposition of charge from the incident single particle.
5. The method as in claim 4 , wherein the critical areas of the first and second delays are each associated with a field effect transistor.
6. The method as in claim 4 , wherein the critical areas of the first and second delays are each associated with a diode.
7. The method as in claim 4 , wherein the critical areas of the first and second delays are each associated with a capacitor.