PURPOSE: To completely eliminate the danger of an operation due to a liquid containing chromium (VI), to completely eliminate the contamination of surroundings and to make the performance of the title etchant equal to or superior to the liquid by a method wherein nitric acid instead of chromium (VI) is contained as an oxidizing agent and the ratio of contained components is made optimum.
CONSTITUTION: An etchant which is used to selectively etch a silicon crystal is composed of the following: 36.5 to 49.5vol.% nitric acid as an oxidizing agent; 1.5 to 5vol.% hydrofluoric acid as an oxide solvent; 12.5 to 33.5vol.% acetic acid as a reaction buffer agent; and water and unavoidable impurities as the remaining part. When a crystal including defects is etched by using the etchant composed of the components, a clear etching pit which reflects the shape of the defects is revealed irrespective of a crystal orientation on the surface, and the surface is roughened little. As a result, it is possible to accurately judge the type, the size, the density, the position, the distribution and the like of the defects. Thereby, it is possible to clarlify a crystal defect which causes the operation error, of a highly integrated operation element, whose cause has been unaccountable so far and to enhance the production yield of a device. In addition, it is possible to completely eliminate the danger of an operation and the contamination of surroundings and to make the performance of the title etchant excellent.
KAWAKAMI KAZUTO
HAGA HIROTSUGU
