The Loading Effect in Plasma Etching

The dependence of etch rate on the quantity of material being etched, often referred to as the loading effect, for plasma etching is analyzed quantitatively with the aid of some simplifying assumptions. The etch rate is related to the quantity of material being etched through three phenomenological parametersβ, τ, and , which are related to the affinity of the etching material for the active species created in the plasma, the lifetime of the active species, and the volume generation rate of the active species, respectively. It is shown analytically that the reciprocal of the etch rate, when identical wafers are etching simultaneously, is directly proportional to . Data are presented for the plasma etching of Si in a plasma which confirm the analytical prediction. The significance of loading with respect to the measurement of etch rate, end‐point detection, and the interpretation of the temperature dependence of etch rate is discussed. A brief discussion of the physical meaning of the phenomenological parameters and their relation to process parameters subject to control such as power, pressure, and temperature is also included.