Tsitsi Madziwa-Nussinov

Ion orbits in plasma etching of semiconductors

Fabrication of high-speed semiconductor circuits depends on etching submicron trenches and holes with straight walls, guided by sheath accelerated ions, which strike the substrate at a normal angle. Electrons accumulate at the nonconductive entrance of each trench, charging it negatively and preventing the penetration of electrons to the bottom of the trench. This “electron shading” effect causes an ion charge at the bottom, which is well known to cause damage to thin oxide layers. In addition, the deflection of ions by electric fields in the trench can cause deformation of the trench shape. To study this effect, the ion orbits are computed self-consistently with their charging of the trench walls. It is found that (a) the orbits depend only on the electric fields at the entrance and are sensitive to changes in the shape of the photoresist layer there; (b) there is an “ion shading” effect that protects part of the wall; and (c) the number of ions striking the wall is too small to cause any deformation thereof.

Generation and Diagnostics of an Electron Beam in a Plasma Cathode Electron (PCE) Source

Summary form only given. An electron beam source is under development at Los Alamos National Laboratory. We outline the generation of the electron beam in a plasma cathode electron (PCE) source. Our PCE source was created using 1.5 kW of microwave power at 2.45 GHz delivered in a static magnetic field of 875 Gauss. We were able to drive electron beams of greater than 100 A in our source with very high beam efficiencies by biasing the ECR source chamber to -140V. Diagnosis of the beam was done using spectroscopy and electric probes. We discuss both the generation method and the diagnostics we used in this experiment.