A Galactic Failure

In my blog entry of June 4th, I described increasing concern of wear-out of multilayer ceramic capacitors. This increasing concern is driven by demands for increasing perfomance (CV) and minizaturzation of of chip sizes. Another concern in electronic systems is the increasing susceptitibility of soft errors from radiation sources. The two major sources of radiation upset are cosmic radiation and semiconductor packaging materials. I find it interesting to think about the sea of (mostly) protons which with were created by exploding stars millions of years ago and then traveling millions of miles, finding their way to the solar system, to earth, to North America, to a specific city, to a specific street, to a particular electronic system, to a single IC and then cause a high reliability system to fail. These particles were well on their way before any electronic systems were even thought about. Although the discovery of radiation effects on electronics was known in the 1990s, it has become an increasing concern is the last several years as IC geometies go below 90nm and Vdd voltages are at 1.5v and below. The secondary neutrons are more likely to cause a soft upset when the critical charge, Qc, gets smaller. Also, the natural radiation found in semiconductor packaging materials which previously did not result in a major problem, now must be calculated in the total system reliability. Most of the electronic systems in use now are consumer electronics where a device upset every 6 months is of no concern. However high reliability systems such as in medical electronics must carefully consider soft error rates. All high reliability system manufacturers should have some expertise in this area. IC suppliers must be asked to provide data on soft errors and then the data must be interpreted by a knowldegable engineer. The design of the IC can have an important effect on SER and the suppliers should have either tested or modeled small geometry devices and provided data to the system designer. This data should include effects from both cosmic radiation and semiconductor packaging materials such as molding compounds, lead solder and BPSG passivation.

Reference: SER - History, Trends and Challenges, Cypress Semiconductor, 2004

Note: Some of the early incidents of radiations effects were, in retrospect, somewhat humorous. For example a semiconductor fab facility was shut down for months due to radioactive phosphoric acid derived from radioactive bat droppings from Jordan Mountain which is near an old uranium mine. An apparantly insignificant decision cause a major problem (the "butterfly effect")