Automated System for Optical Inspection of Defects in Resist-coated Non-patterned Wafer

Abstract

Quality control of the resist coating on a silicon wafer is one of the major tasks
prior to the exposition of patterns into the resist layer. Thus, the ability to inspect and
identify the physical defect in the resist layer plays an important role. The absence of any
unwanted defect in resist is an ultimate requirement for preparation of precise and
functional micro- or nano-patterned surfaces. Currently used wafer inspection systems are
mostly utilized in semiconductor or microelectronic industry to inspect non-patterned or
patterned wafers (integrated circuits, photomasks, … etc.) in order to achieve high yield
production. Typically, they are based on acoustic micro-imaging, optical imaging or
electron microscopy. This paper presents the design of a custom optical-based inspection
device for small batch lithography production that allows scanning a wafer surface with an
optical camera and by analyzing the captured images to determine the coordinates (X, Y),
the size and the type of the defects in the resist layer. In addition, software responsible for
driving the scanning device and for advanced image processing is presented.

Keywords: Optical inspection, Resist layer, Non-patterned wafer, Quality control.