BACKGROUND

A power MOSFET has been used in automotive electronics as a reliable switching device. An increase of electronics systems requires the power MOSFET with low on-resistance to reduce power dissipation. In general, on-resistance of the power MOSFET is reduced by miniaturization of unit cells. In this paper, however, it is shown that low on-resistance can be achieved by the improvement of the drain electrode process. Taguchi Methods_ have been applied to improve the drain electrode process. This result also can be applied to devices with similar structures.

PROCESS

Nine process parameters from the drain electrode were studied to optimize the conductivity. Eighteen combinations of nine parameters were tested for robustness. For each of 18 runs, the input currents were varied at 0.5, 1.0 and 1.5 Amperes, and voltage was measured under two compounded noise conditions. Since conductivity must be assured under various customers' usage environments including aging, two noise conditions were derived from compounding two noise factors, "ambient temperature" and "cycling."

BENEFITS

• Because the robust drain electrode was achieved, the annealing process was eliminated. (The annealing process was added as a follow-up solution for a poor drain electrode process. It is a typical engineering practice to add compensation to fix problems.)

• Because the annealing is eliminated, needless to say, all defects from annealing were eliminated (defects such as peeling and cracking from annealing).

• Because there is no need for annealing, the substrate can be...