New microcharacters for wafer identification

Conventional identification (ID) systems use characters that are often illegible, with character recognition being difficult in as many as 20% of all processes. In contrast, new microcharacters in the V-shaped notch are clearly recognized throughout the process. The results can be explained by the following multiple effects. Marking location: These markings require only a small space. Hence, markings can even be in the beveled section of the V-shaped notch of a wafer. In the case of conventional ID systems, it is difficult to select an area that gives good readability during processes and wide enough for marking. Dot topography: A marking dot formed by conventional laser marking has a central depression due to the process of general heat distribution. In contrast, a marking dot formed by micro marking has a central peak protruding from the surface that is more easily distinguished than a dot that has a central depression. The contrast of the new dot is about two times greater than that of a conventional one. Contrast greatly influences readability