On the Light Figure Phenomenon Revealed and Crystal Faces Developed by Chemical Etching in Silicon Crystal

The light figure phenomenon of silicon single crystal etched with various chemical reagents has been studied in order to find out the light figures or the etching conditions suitable for the orientation determination and to obtain the information regarding crystal faces developed by etching. Etching with aqueous solutions of potassium hydroxide or sodium hydroxide boiled or heated at 100° or 70°C produce distinct {100}, {110} and {111} light figures, while any other reagent reveals only indistinct light figures or no light figure at all. It has been found that for the orientation works the etching with saturated aqueous solution of either alkali heated over some 100°C are most suitable in view of the shortness of the required etching time (<2∼3 minutes). The crystal faces developed by etching with alkaline reagents vary with the kind, concentration and temperature of the reagent and the time of etching, and belong to the 〈100〉 and 〈110〉 zones, the {111} and {100} faces being commonly developed.