Radiation Hardening Design Services

Ridgetop has been on the forefront of designing effective solutions for electronics operating in harsh environments. One of the harshest environments for complex electronics is exposure to radiation. Maintaining full functionality in the space environment, where radiation effects are much higher than on the ground, is especially difficult.

Radiation effects can be separated into three broad categories:

• Total Ionizing Dose (TID) – This is an accumulative problem where the oxides within integrated circuits (ICs) will trap charge, creating threshold voltage (V_T) shifts and unwanted conduction paths for leakage currents. These effects can eventually cause failure of the IC, either in the form of increased transistor mismatch or increased off-state power dissipation. The scaling of MOS transistors has helped mitigate these effects. V_T shifts have been significantly reduced in transistor technologies in which the gate oxides are thinner than 5 nm due to recovery by tunneling. A significant reduction in radiation-induced leakage currents has also occurred in advanced nano-CMOS technologies and this improvement in hardness has been shown to be mainly due to the increased transistor body doping levels along the insulation oxide trenches, which mitigates the trench sidewall inversion. Despite these advances, recent studies indicate that TID radiation damage remains a threat to modern CMOS ICs.
• Transient Dose Rate (TDR) – This is a highly specialized effect that is found in high pulse fluxes from sudden discharges of radiation.
• Single-Event Effects (SEE) – These effects can cause transient bit flips in digital circuits at high altitudes where energetic particles can strike a sensitive node within an IC. There are methods to handle this, such as triple module redundancy with voting, but at the expense of area and power. Other, more serious effects have been found, such as Single-Event Latchup (SEL) and Single-Event Gate Rupture (SEGR).

Over the years, Ridgetop has introduced precision radiation effects test structures within our Sentinel Silicon™ Library, including RadCell F_OX (for current leakage) and RadCell V_T (for threshold voltage shifts).

Other solutions that Ridgetop has designed include are rad-hard IP cores as part of our a InstaCell™ Library. Among the blocks available is our rad-hard, high-speed, precision analog-to-digital converter (ADC) IP core that offer a 40 MSPS sample rate and 14 bits of resolution. This is an excellent choice for critical imaging systems.

For unique or specialized requirements, Ridgetop’s Design Services Group can help. Ridgetop is signed up for certification as a Trusted Supplier under the DoD’s Trusted Foundry program and will be receiving the certification shortly. Design examples include: both IC and PCB-based solutions; FPGA-based designs; laser rangefinder electronics; and critical designs for FAA-compliant (including DO-178 and DO-254) commercial aerospace designs. For more information, click here: http://www.ridgetopgroup.com/products/semiconductor/rad-hard.php.

Ridgetop also participates in industry conferences where many of these issues are discussed, such as Hardened Electronics And Radiation Technology Conference (HEART), Government Microelectronics Conference (GOMAC) and IEEE Nuclear and Space Radiation Effects Conference (NSREC).