The future of delta IDDQ testing

The increase in off-state current for deep submicron technologies will make conventional I_DDQ testing ineffective. An attractive alternative is differential I_DDQ or ΔI_DDQ testing as a function of the test pattern; it is relatively easy to implement it in a production environment and the method can detect I_DDQ anomalies of a few percent of the off-state current itself. In its simplest form the method is limited by state-dependent leakage current variations. More advanced versions of ΔI_DDQ testing can cope with these state-dependencies and are useful for off-state currents in the milliampere range. The presence of state-dependent leakage currents can be utilised to detect large passive defects, which are otherwise undetectable with ΔI _DDQ. For even higher leak-age currents circuit-specific state-dependencies become the limiting factor and make ΔI_DDQ testing ineffective for devices with off-state currents above 100 mA