The present invention relates to a resist removal width inspection apparatus for inspecting whether a width of resist material removed, in a photo process, from the outer surrounding part of a resist-coated semiconductor wafer, glass substrate or the like, is proper or not.
In a photo process of forming a pattern on a semiconductor wafer, a wafer is coated with a resist material, and a resist layer formed on the wafer is exposed to light through a pattern by using the photographic technique, so as to form a minute pattern on the wafer. In the process, there is possibility of generating dust particles due to contact of the resist material attached to the outer surrounding portion of the wafer with the carrier. To avoid the dust generation, after the resist coating, the resist material is removed from an outer surrounding portion over a fixed width (this width will be referred frequently to as a resist removal width) on the resist-coated wafer (edge bead removal (EBR) process). In this case, if the resist material is excessively removed, an original resist pattern is adversely affected, and if the resist removal width is narrow, dust may be generated. Accordingly, it is necessary to inspect whether the resist removal width is proper or not. Conventionally, a visual inspection is employed for inspecting the resist removal width. That is, an operator applies light to the resist-coated wafer, visually checks a color change of light reflected from the wafer, discriminates an edge (boundary position) of the resist based on the color change, and judges whether the resist removal width is proper or not, by its position and shape.
The visual inspection by the operator inevitably suffers from adverse influences of the dust generated by the operator himself or herself upon the inspection result and a variation caused by individual difference in the inspection result. Further, the inspection result is utilized for only an examination pass decision, and cannot be utilized for management based on numerical values of inspection contents. For this reason, there is a need of automatizing the inspection process of the resist removal width.