New process boosts ESD protection

By Nick Flaherty www.flaherty.co.uk

Electrostatic discharge (ESD) can be a major problem for embedded equipment. Static generated from everyday movement can damage silicon devices, especially as process technology means feaatures in the chips are ever smaller and more vulnerable to such electric shocks

Toshiba is hoping a new process technology it has developed to increase resistance to Electrostatic Discharge (ESD) in devices will help.

The 0.13μm process technology at New process boosts ESD protection | EETE Power Management optimizes the structure of transistor and significantly improves ESD characteristics by a factor of four, while the standard deviation is only 1/12 that of the conventional structure. Analysis of 3D simulations has also allowed Toshiba to identify a mechanism for optimizing transistor structure to boost ESD robustness.

ESD protection devices are required to protect internal circuit and this is particularly true for analogue power semiconductor devices required to apply 10V to 100V, which need a high rated voltage. In this case, ESD protection devices must ensure high current flow, which results in enlarged chip size. Shrinking the size of the ESD protection device is an issue in realizing more compact chips.

Using 3D simulation analysis of an ESD event, Toshiba found out that ESD induced destruction is caused by lattice temperature increase due to the current flowing at the highest electric field point. Modifying the transistor structure, which extending the drain low resistive region to the source direction and suppressing the lateral silicon resistance, shifts the current flow from the bottom of the drain to source direction and detaches it from the highest electrical field point. This optimized design was found to increase ESD robustness by up to four times and to decrease the standard deviation down to 1/12. In addition, the device size required to ensure a HBM (Human Body Model) of ±2000V was cut by 68%.

Toshiba offers advanced analog process platforms, with 0.13μm process technology, that can be embedded with the transistors such as CMOS, DMOS, bipolar transistor and the passive devices such as resistor and capacitor. User can select a process suited to each application from three process platforms: “BiCD-0.13” is mainly for automotive (DMOS line up is up to 100V); “CD-0.13BL” is mainly for motor control drivers