Effect of gas pressure on ion energy at substrate side of Ag target radio-frequency and very-high-frequency magnetron sputtering discharge

The effect of gas pressure on ion energy distribution at the substrate side of Ag target radio-frequency (RF) and very-high-frequency (VHF) magnetron sputtering discharge was investigated. At lower pressure, the evolution of maximum ion energy (E) with discharge voltage (V) varied with the excitation frequency, due to the joint contribution of the ion generation in the bulk plasma and the ion movement across the sheath related to the ion transit sheath time τ_i and RF period τ_RF. At higher pressure, the evolution of E–V relationships did not vary with the excitation frequency, due to the balance between the energy lost through collisions and the energy gained by acceleration in the electric field. Therefore, for RF and VHF magnetron discharge, lower gas pressure can have a clear influence on the E–V relationship.