Control of ion energy distributions in inductively coupled ratio-frequency plasmas with a biased electrode*

We measured the ion energy distribution (IED) and plasma density as a function of the voltage phase shift $\varphi $ between the source and bias electrode in inductively coupled argon plasma driven at 13.56 MHz by using a retarding field energy analyzer and a commercial Langmuir probe, respectively. Our results demonstrate that under some certain discharge conditions, as the phase shift $\varphi $ increases from 0 to 2$\pi $, the plasma potential slightly decreases with $\varphi $, while the IED exhibits drastic changes in both the IED width and the energy of bimodal distribution. To be specific, as $\varphi $ increases from 0 to $\pi $, the IED width increases and the bimodal distribution shifts to high energy region. However the IED width almost keeps constant and the bimodal distribution shifts to low energy region, when $\varphi $ increases from $\pi $ to 2$\pi $.