Effect of Secondary Electron Emission on Surface Charging during Plasma Etching for Microelectronics Fabrication

Plasma etching is a critical process in semiconductor device manufacturing. During this process ions having a broad range of energy and a narrow angular distribution are incident onto the wafer. Depending on the power format, electrons are incident onto the wafer with broad angle, low energy distributions or moderately energetic, moderately narrow distributions. These different energy and angular distributions lead to differential charging of the features being etched, which can in turn lead to feature distortion due to deflection of the trajectories of incoming particles. A phenomenon that is important in this process is secondary electron emission induced by ions, electrons and photons striking the surface. With secondary emission by electrons and ions being dependent on energy and angle, secondary electron emission can result in additional positive charging at the location of intial collision even by electrons. The secondary electrons are accelerated by the local electric field can deposit charge in a different location.

The Monte Carlo Feature Profile Model (MCFPM), a 3-dimensional voxel-based model, describes the physics and chemistry of feature scale plasma etching and charge deposition. The MCFPM receives energy and angle resolved fluxes from the Hybrid Plasma Equipment Model (HPEM). The MCFPM capabilities for describing the emission of secondary electrons by ions, electrons, high-energy electron beam and photons have been improved. Charging of test structures in capacitively coupled plasmas sustained in argon with continous and pulsed excitation and the role of secondary emission will be discussed.