Ridgetop Group’s Hot Carrier (HC) Prognostic Cell is a pad-limited CMOS hot carrier damage/failure detection cell. It is a part of the Sentinel Silicon™ library of prognostic (“canary”) cells.
The HCI prognostics cell’s unique and proprietary architecture behaves as an early-warning “sentinel” of an upcoming hot carrier damage fault condition in the host circuit. This degradation of MOS transistors is caused by the injection of high-energy electrons into the gate oxide. The damage is in the form of localized charge trapping, which causes a decrease in drain current ID and an increase in threshold voltage (VT). The amount of pre-warning is given in the form of percent of delta VT shift from 2 to 10%.
Promoting miniaturization without scaling the supply voltage implies increasing the electric field intensity of the internal elements of a device. This is especially true in the case of MOS FETs, where the electric field intensity near the drain area increases and a hot carrier degradation effect occurs.
Carriers (electrons) that flow into the high-electric-field area are accelerated by the strong field, and gain substantial energy. Some of the carriers become a hot carrier, which means they have enough energy to overcome the electric potential barrier existing between the Si substrate and gate oxide film. These degradations cause the deterioration of all semiconductor device characteristics and ultimately lead to failure.
The HC prognostic cell looks at two modes of degradation: Drain avalanche hot carrier (DAHC) injection and channel hot electron (CHE) injection.A block diagram of the Ridgetop Hot Carrier prognostic cell is shown in the figure below.