SOME FUNDAMENTAL-ASPECTS OF PROFILE ETCHING AT INP SURFACES

Etching profiles at mask edges on (100) InP are obtained in acidic FeC l3 containing solutions under uniform illumination and in iodic acid s olutions in darkness. For-both etching systems, the results of microsc opic etching near mask edges are compared to the macroscopic etching b ehavior of individual crystallographic faces. In the case of photoetch ing by FeCl3, a difference in profile shape is observed between p- and n-type samples, associated with the fact that the photoetching occurs by an electrochemical mechanism At p-type samples; the slowest etchin g face [i.e., the (111) face] is revealed whereas at n-type, profiles with very rough bottoms are observed. A tentative interpretation for t his phenomenon is proposed. Mo difference in profile shape is found be tween p- and n-type in the iodic acid solution, which operates through a chemical mechanism. An anisotropic microscopic etching behavior is however observed. A model, in which the presence of a thin oxide layer on the InP plays a crucial role, can explain this etching behavior.