Research of anisotropic etching in KOH water solution with isopropyl alcohol

Anisotropic etching plays a key role in the whole manufacture process of Microelectromechanical system (MEMS). As a non-poisonous and low-cost etchant, KOH water solution is used extensively in anisotropic etching process. The etching process of silicon wafers in KOH water solution with isopropyl alcohol (IPA) has been studied. IPA proved to be an effective admixture to the solution improves the smoothness of etched silicon surfaces. The etching rate of silicon wafers in the wide range of etching temperature has been estimated. The etching rate increases with the increase of etching temperature. The influence of solution concentration on etching rate has been discussed. Theoretical explanation is offered to expound the phenomenon that there is a peak of etching rate with the change of KOH concentration. An optimum of composition of KOH water solution is offered.