Radiation hardened

Microelectronics designed for environments with high levels of ionizing radiation have special design challenges. A single charged particle of radiation can knock thousands of electrons loose, causing electronic noise, signal spikes, and in the case of digital electronics, incorrect results. This is a problem in the design of artifical satellites, nuclear power stations, and nuclear weapons.

Many manufacturers of integrated circuits market a product line of radiation hardened (also known as RAD hardened or simply hardened) chips and sensors for their military, aerospace, and nuclear power customers. These are often based on their more mundane commercial equivalents, with some manufacturing and design variations that reduce the susceptibility to inteference. Typically, the hardened variants lag behind the cutting-edge commercial products by several technology generations due to the extensive development and testing required to produce a radiation resistant design.

Techniques

• Hardened chips are often manufactured on insulating substrates instead of the usual semiconductor wafers. Silicon oxide and sapphire are commonly used.
• Error correcting memory uses additional parity bits to check for and possibly correct corrupted data.
• Redundant circuitry elements can be used to duplicate calculations. If the end results do not match due to errors, the calculation can be repeated.
• Shielding the package against radioactivity, to reduce exposure of the bare device.
• Watchdog timer circuitry can check for crashes in operating software.
• Capacitor-based DRAM is often replaced by more rugged (but larger, and more expensive) SRAM.

Examples

• RAD6000 is variant of the IBM POWER CPU manufactured by BAE SYSTEMS
• Sandia Labs manufactures an Intel Pentium variant.
• An Integrated Approach with COTS Creates Rad-Tolerant Single Board Computer for Space