Role of secondary electrons in high power dual frequency capacitively coupled plasmas

Dual frequency capacitively coupled plasmas are often used in the semiconductor fabrication industry for applications requiring independent control of the ion energy and flux. The high frequency power typically contributes to electron heating and plasma density while the lower frequency power contributes to ion acceleration. At very high powers of the low frequency component, the ion energy can be high enough to induce emission of large quantities of secondary electrons from surfaces ^[1]. In addition, there are electron-induced secondary emission effects that may be present. These secondary electrons can have a significant impact on spatial plasma profiles due to changes in local electron energy distribution functions (EEDF) and ionization sources that are driven either by bulk or secondary electron population. Measurement of the secondary electron emission coefficient (SEEC) is not always practical. In this work, results from plasma simulations are discussed to highlight the impact of these secondary electrons on plasma properties, ion energy and angular distribution (IEAD), and sheath dynamics. The role of secondary electron emission in electropositive and electronegative plasma and its impact on radial uniformity will also be discussed.