MODEL OF ETCHING PROFILES FOR ION ENERGY FLUX DEPENDENT ETCH RATES IN A COLLISIONLESS PLASMA SHEATH

A model for the simulation of etch rates in ion-assisted etching of trenches on semiconductor wafers is developed. The evolution equation for the etched profiles where the etch rate is proportional to the incident ion energy flux is solved by the method of characteristics. The novel feature is that the ions incident on the semiconductor wafer are represented by a drifted Maxwellian distribution function. Approximate analytical expressions for the etch rates are derived and etch profiles are computed by integrating trajectory equations. The anisotropy of the etch improves with increasing values of the parameter U where U is the ratio of the ion beam speed to the ion thermal speed. The deviation from a rectangular trench is shown for different values of U. © 1995 American Institute of Physics.