Voltage Waveform Tailoring in Plasma Etching of Dielectrics to Mitigate Surface Charging Effects

Abstract

Shrinking feature sizes and increasingly large aspect ratios (HAR) in plasma etching pose major challenges to high volume manufacturing of nanoscale semiconductor devices. When plasma etching dielectric materials, electrostatic charging in the feature and the resulting deflection of electrons and ions can be a source of feature distortion and reduction in etch rate. Disparate intra-feature charging results from the ion angular distribution into the feature typically being narrower than the angular distribution of electrons. Voltage waveform tailoring (VWT) allows for significant control of the ion and electron energy and angular distribution which can partially mitigate intra feature charging. In this talk, we will discuss results from a computational investigation of the plasma etching of HAR features in SiO 2 using VWT. The system is a dual-frequency capacitively coupled plasma sustained in fluorocarbon gas mixtures and operated at 40 mTorr. The gas phase simulations were performed using the Hybrid Plasma Equipment Model (HPEM). The applied waveform consists of 5 harmonics with a base frequency of 1 MHz. Using HPEMs reactive fluxes to the wafer, the etching of a HAR via in SiO 2 was simulated using the Monte Carlo Feature Profile Model (MCFPM). The resulting features were evaluated with respect to surface charge distribution, feature deformation and etch rate.