Method for registering a mask pattern in a photo-etching apparatus for semiconductor devices

A method for registering a pattern on a mask plate with a pattern already formed on a semiconductor wafer;

• characterized by the steps of forming at a predetermined position on said wafer a reflector group which consists of a plurality of reflectors of predetermined shape aligned at a predetermined pitch along a predetermined direction;
• forming first and second window groups at predetermined positions on said mask plate in correspondence to the position of said reflector group on the wafer, each window group consisting of a plurality of windows of predetermined shape aligned at the same predetermined pitch along the same direction as the reflector group, one window group being provided with a staggered phase relationship equal to a multiple of one half of said predetermined pitch with respect to the other window group;
• moving one of said wafer and said mask plate relative to the other in the direction of alignment of the reflectors and windows while irradiating said reflector group with light;
• providing first and second detecting means for determining the quantity of light reflected by the reflector group and passing through said first and second window groups, respectively;
• and determining the relative position of the wafer and the mask plate by determining when the detected respective quantities of light take a predetermined proportion to thereby register the pattern on said mask plate with the pattern already formed on said semiconductor wafer.