Parameters Affecting Materials

The plasma process are carried out using vast range of frequency from DC to Giga Hz and with different voltage bias and waveforms on powered electrodes. Also, the biasing on the other electrode (grounded or floating conventionally) with a relatively small frequency pulse or tailored waveform is used to tailor the material properties now a days. A simple method to monitor the plasma similarity against these external parameters is to measure the plasma impedance. A plasma can be electrically represented as a diode, a resistor, and a capacitor in parallel. The electrical parameters of plasma i.e. impedance, forward power, reflected power, current, voltage and phase are need to be monitored to understand the electron and ion dynamics inside plasma as they will be directly affecting the properties on end product.

Figure 1: Schematic diagram of the magnetron sputtering assisted with substrate bias. (DOI:https://iopscience.iop.org/article/10.1088/2058-6272/aae7dd/meta )

The effect of radio-frequency substrate bias on ion properties and sputtering behavior of 2 MHz magnetron discharge was investigated as shown in the experimental described above in figure 2. The sputtering behavior was investigated by the electric characteristics of target and bias discharges using voltage–current probe technique. The variation of reactive impedance Xs with bias power is shown in figure 3. It can be found that the discharge pressure has obvious influence on the variation of reactive Xs . At the pressure of 5 Pa, the reactive Xs shows a decrease trend with the bias power increase, but at the pressure of 1 Pa a slight increase trend is obtained.

Thus, at higher pressure, the increase of bias power leads to the decrease of sheath thickness, while at lower pressure, the increase of bias power leads to the slight increase of sheath thickness. Sheath thickness directly controls the ion energies and modify the IVDF reaching the substrate. The impact of IVDF on the growth rate and properties of the deposited have been well established.

Figure 2: Variation of discharge impedance Xs with bias power for different sputtering power at the pressure of 5 and 1 Pa. (DOI:https://iopscience.iop.org/article/10.1088/2058-6272/aae7dd/meta )