DOE Center for Control of Plasma Kinetics Highlight Photo-Assisted Etching of Si in Cl- and Br-Containing Plasmas

Photo-assisted etching (PAE) of p-Si in Cl2/Ar plasmas was first reported in Ref. [1]. The PAE rate was substantial compared to the ion-assisted etching rate, causing complications for processes that require low ion energies, such as etching with atomic layer resolution or highly selective and anisotropic etching of nano-features. Absolute etching rates (solid symbols) are shown in Fig. 1, calibrated by relative intensity of optical emission of the Si 2882 Å line (proportionality constant is given in parenthesis in fig-ure label), and measured absolute etching rates (hollow stars), as a function of E1/2 (E=ion en-ergy), in different continuous wave ar-gon/halogen plasmas. Pulsed dc bias at 10 kHz and 50 % duty cycle was applied on the sample stage. Double headed arrow lengths indicate photo-assisted etching rates obtained by sub-tracting any isotropic (chemical) etching rate from the total sub-threshold etching rate. PA