Road to Recovery

With the proliferation of advanced electronics in critical systems, semiconductor reliability has received increased levels of interest by concerned engineers. The concerns stem from the fact that smaller process geometries that allow increased functionality also introduce problems from extremely thin gate oxide thicknesses and shorter lifetimes.

Over the years, Ridgetop has designed a number of unique semiconductor test structures for determining the extent of damage induced by effects such as:

• Time-Dependent Dielectric Breakdown (TDDB)
• Hot Carrier Injection (HCI)
• Radiation Effects (edge leakage, threshold voltage shifts)
• Negative Bias Temperature Instability (NBTI)

These test structures can be used for “canary”-type prognostic applications to detect the impending failure of the integrated circuit (IC), or adapted for use in commercial die-level process monitoring applications. These can be used to facilitate “process-aware” design of advanced ICs.

NBTI has surfaced as a key area of concern due to its introduction of temperature-dependent intermittencies. The intermittencies are caused by temporary threshold voltage shifts within transistors in the ICs. The ICs are supposed to have matched transistors, so with NBTI causing significant mismatches to occur, timing errors, “locked up” systems or other problems can occur. These problems can then “heal” and be difficult to recreate on the test bench. Thus, intermittencies drive up the cost of maintenance of these complex systems when these problems cannot be reproduced. Variously called NTF (No Trouble Found), NFF (No Fault Found), or CND (Could Not Duplicate), these issues require advanced methods to isolate, characterize and solve.

Ridgetop’s NBTI is the newest member of our Sentinel Silicon™ library, and joins other solutions that we offer to designers of critical systems, including SJ BIST (for BGA intermittencies), and many others. Ridgetop has current programs in process geometries to 28 nm.

For more information on our NBTI Test Structures, or the Sentinel Silicon™ library, please give us a call.