Downstream etching of silicon nitride using continuous-wave and pulsed remote plasma sources sustained in Ar/NF3/O-2 mixtures

作者：Huang Shuo; Volynets Vladimir; Hamilton James R; Nam Sang Ki^*; Song In Cheol; Lu Siqing; Tennyson Jonathan; Kushner Mark J^*

来源：Journal of Vacuum Science and Technology A, 2018, 36(2): 021305.

DOI：10.1116/1.5019673

Remote plasma sources (RPSs) are being investigated to produce fluxes of radicals for low damage material processing. In this computational investigation, the properties of a RPS etching system are discussed where an Ar/NF3/O-2 gas mixture is flowed through an inductively coupled plasma source into a downstream chamber containing a silicon nitride coated wafer. The plasma is largely confined in the RPS due to the highly attaching NFx (x = 1-3) and an isolating showerhead although a weak ion-ion plasma maintained by [NO+] approximate to [F-] leaks into the downstream chamber. The etching of silicon nitride proceeds through iterative removal of Si and N subsites by isotropic thermal neutrals. When the fluxes to the wafer are rich in fluorine radicals, the etch rate is limited by the availability of NO molecules and N atoms which remove N subsites. As power deposition increases with continuous-wave excitation, the etch rate increases almost linearly with the increasing fluxes of NO and N atoms, as production of NO through endothermic reactions is aided by increasing gas temperature. Production of N atoms through electron impact dissociation of NO and NFx is aided by the increasing electron density. Similar trends occur when increasing the duty cycle during pulsed excitation. Addition of a plenum between the RPS and the downstream chamber aids in lateral diffusion of radicals before passing through the final showerhead and improves the uniformity of etching. Published by the AVS.

• 出版日期2018-3