Investigation of conduction mechanism in thick film resistors trimmed by the pulse voltage method

The conduction mechanism of RuO₂-based thick-film resistor (TFR) trimmed by the pulse voltage trimming (PVT) method is discussed. The surface temperature distribution barely changed when power was applied to the TFR, moreover, no current crowding was found by results of scanning electron microscopy-voltage contrast (SEM-VC). The existence of electron traps in the TFR could not be detected from the results of temperature stimulus current (TSC) characteristics. The resistance value of the TFR increased at 600°C and then decreased abruptly at 800°C. It was supposed, therefore, that the heat stress accumulated in the TFR during the refiring process of the TFRs was relaxed by the thermal annealing due to the PVT. Consequently, the decrease in the resistivity of the TFR, after the PVT, was quite logical, if an increase in the number of conductive paths resulted when the conductive structure was modified in the TFR. In addition, frequency resistance characteristics of the TFRs qualitatively best fit the values predicted by the metal-insulator-metal model