The Implementation of the Surface Charging Effects in Three-Dimensional Simulations of SiO<sub>2</sub> Etching Profile Evolution

Abstract

Refined control of etched profile in microelectronic devices during plasma etching process is one of the most important tasks of front-end and back-end microelectronic devices manufacturing technologies. A comprehensive simulation of etching profile evolution requires knowledge of the etching rates at all the points of the profile surface during the etching process. Electrons do not contribute directly to the material removal, but they are the source, together with positive ions, of the profile charging that has many negative consequences on the final outcome of the process especially in the case of insulating material etching. The ability to simulate feature charging was added to the 3D level set profile evolution simulator described earlier. The ion and electron fluxes were computed along the feature using Monte Carlo method. The surface potential profiles and electric field for the entire feature were generated by solving Laplace equation using finite elements method. Calculations were performed in the case of simplified model of Ar + /CF 4 non-equilibrium plasma etching of SiO 2 .

Application of the Level Set Method in Three-Dimensional Simulation of the Roughening and Smoothing of Substrates in Nanotechnologies

“…The initial surface is given by {x|ϕ(0,x) = 0}. The evolution of the surface in time is caused by the surface processes in the case of the etching [19]. The velocity of the point on the surface normal to the surface determines the initial surface.…”

Control of electron velocity distributions at the wafer by tailored voltage waveforms in capacitively coupled plasmas to compensate surface charging in high-aspect ratio etch features

“…While positive ions are accelerated towards the wafer by the sheath electric field and hit it vertically and continuously with high energies, electrons reach the substrate during the local sheath collapse at low energies and with a wide angular distribution [8]. The etch process is driven by high energy ions and reactive radicals [9][10][11][12][13][14][15][16], but the fluxes of positive ions and electrons must balance at each surface element of a dielectric wafer locally on time average, including the bottom and the sidewalls of trenches [8,17,18]. In the presence of a wide angular distribution, electrons cannot penetrate deeply into HAR trenches.…”

Electric field reversals resulting from voltage waveform tailoring in Ar/O2 capacitively coupled plasmas sustained in asymmetric systems

“…The highly anisotropic, near normal, high energy ions can penetrate deeply into HAR features whereas the electrons typically have nearly thermal and angularly broad distributions onto the wafer [1]. When etching dielectric (or low conductivity materials), these conditions result in the lower echelons of the feature being charged positively and the upper echelons being charged negatively [8,9]. This differential charging generates electric field components within the feature [8][9][10].…”

“…When etching dielectric (or low conductivity materials), these conditions result in the lower echelons of the feature being charged positively and the upper echelons being charged negatively [8,9]. This differential charging generates electric field components within the feature [8][9][10]. The intra-feature electric fields can deviate ion trajectories from the vertical which can then lead to undesired consequences including a reduction of the ion flux at the bottom of the feature and reduction in etch rate [11], and profile distortion such as notching, twisting and bowing [8][9][10][11][12][13][14][15].…”