We have developed new DMOS FET (DMOS) and intelligent power devices (IPD) specified for automotive load driving. Their features are extra-high surge immunity and low on-resistance. MOS power semiconductor devices are the most suitable for driving high speed and large current loads in future car electronics, but their high cost is the main obstacle preventing their implementation. To cut the total system cost, we have tried to enhance surge immunity of power semiconductor devices, at the same time reducing ON resistance, which enables us to omit external protection. Enhanced avalanche power dissipation also enables us to lower the breakdown voltage of the device, which also brings lower on-resistance. The drain to source avalanche immunity of vertical type DMOS (VDMOS) has been sharply improved by using the parasitic PN junction of the channel diffusion region as the cellular zener diode. Avalanche power dissipation energy per unit area of this durable DMOS is 10 to 100 times higher than that of conventional VDMOSs. Although the breakdown voltage of this device is only 30V, no external protection device is required in automotive applications. Several fault phenomena which might occur in this device are also described. Two types of IPDs are proposed in this paper. One is a durable and low-cost high-side switch IPD, whose enhanced surge immunity of IC section from VDD line transient is verified by prototypes. Simplification of the fabrication process has also been achieved by lowering its breakdown voltage. The other is an extra-low on-resistance H-bridge IPD. Major on-resistance reduction of an output lateral type DMOS (LDMOS) is achieved because the cell-array structure is realized by applying 2-layer electrode technology to the power section. The on-resistance per unit area of this LDMOS is almost equal to that of VDMOSs in the same voltage class.

The hole-trapping and electron-trapping characteristics in dry oxides following various chemical cleanings have been studied using the avalanche injection method. The results indicated that hole trap density was almost the same for the chemical cleanings. Electron traps with two capture cross sections, σ, were observed. Electron traps with σ210-17 cm2 were found to be independent of the chemical cleaning, while those with σ410-19 cm2 to depend on the cleaning. Comparison with previous works indicated that electron traps with larger σ were related to Si-OH bonds. The other electron trap showed the increasing trapping rate with increasing the current density injected into oxide. This was explained by trap generation due to electron injection. A correlation between the density of generated electron traps and the amount of Al contamination on surfaces before dry oxidation was observed.