## 3 Results
Since the Cu-doped TiNxOy resistors are not destroyed completely by high-current but rather continue to function in high-resistivity state, they may be used as integrated fusible resistors in order to limit currents to tens mA range and to provide the benefit of both overcurrent and inrush current protection. In order to explore the prospects of using the Cu-doped TiNxOy thin film resistors as fusible resistors, we studied their lifetime as a function of power. For that, we increased the maximum voltage to 200 V and varied the voltage ramp magnitude. Figure 6 shows the stressed resistors _I-V_ curves family measured for several resistors destroyed at different voltage ramps. As expected, low ramps yield lower maximum current and critical voltage due to a larger time-integral of power, i.e., dissipated energy. These data were used to calculate the fusible resistors life-time versus maximum power shown in Figure 6b. Figure 6c shows micro-images of a resistor burnt by steep high voltage ramp along with its EDX 2D color-coded map of the nitrogen and oxygen concentration distribution. From both the optical image and EDX data, it appears that the fusing action of resistors is, indeed, due to the nitrogen replacement with oxygen, i.e., transition from optically non-transparent N-rich to a transparent O-rich TiNxOy. This N-to-O transition happens dynamically when increasing the voltage and always starts at a point close to the middle of the resistor body, gradually propagating towards the high-bias terminal with the propagation speed  
Figure 5: High voltage stress burning tests of the 3-square Cu-TiNxOy thin film resistor: (**a**) The maximum stress voltage progressively increased from 11 to 30 Volts in nine consecutive measurements (shown in nine different colors); the maximum current peaks of the IV-curves correspond to light emission by resistor body, eventually resulting in irreversible change and the phase transition shown in (**b**) (red curves of group 2) from low-resistance state (blue curves of group 1) to high-resistance state (green curves of group 3). Shown at the yellow inset of (**b**) is EDX nitrogen concentration distribution maps for the normal (state-1) and burnt (state-3) resistors, which reveals noticeable N-concentration gradient in the later. proportional to the voltage increase rate. The N-to-O transition boundary front propagates by discrete jumps accompanied by the light micro flashes. Figure 6d shows the same _I-V_ curves as in Figure 6a at higher voltages revealing intriguing features: pronounced current oscillations. The first peak voltage is always fixed at \(\sim\)25 V for all destroyed resistors, and higher peaks gradually diminish and ungroup. These oscillations appeared only at high voltage ramps and the higher the ramp the higher their magnitude and the narrower the peaks. At lower ramps these peaks diminish and start shifting to lower voltages before transforming into almost equidistant saw-like current pattern. The highest voltage current peak appears as a sharp spike measuring 5-10 mA at 100-120 V, and the resistor eventually (>150 V) explodes by sublimating the metal traces to pads if one increases the voltage even further. The current peaks of Figure 6d are related to the light micro flashes mentioned above and are associated with the micro-scale breakdown-like step-by-step conversion of the parts of the resistor body that they spark through from grey to transparent. Half of resistor attached to the terminal at zero voltage always preserves its N-rich composition associated with the grey color. Shown in Figure 7 are the results of the S-parameters' high-frequency measurements and simulations.