 Since neutral particles attack the wafer from all angles, this process is isotropic.Plasma etching can be isotropic, i.e., exhibiting a lateral undercut rate on a patterned surface approximately the same as its downward etch rate, or can be anisotropic, i.e., exhibiting a smaller lateral undercut rate than its downward etch rate.Such anisotropy is maximized in deep reactive ion etching.