Tracking and Synchronization with Inversion-Based ILC for a Multi-Actuator-Driven Wafer Inspection Cartridge Transport Robot System

This paper proposes a simple tracking and synchronization control of a dual-drive system using inversion-based iterative learning control (IILC), which reformulates the model at each iteration based on input/output data. By the power of the IILC, this work simplifies the dual-actuator-driven dynamic system control problem that is normally addressed with a MIMO method. This work also shows the potential of the IILC for nonlinear system applications by reformulating the model at each iteration based on the input/output data. An analytical representation of the iteration-varying IILC followed by simulations is provided. A set of physical system testings with a dual-motor gantry and a semiconductor wafer inspection robotic system are carried out to verify the control method.

Image Wafer Inspection based on Template Matching

This paper presents a template matching technique for detecting defects in VLSI wafer images. This method is based on traditional techniques of image analysis and image registration, but it combines the prior art of image wafer inspection in a new way, using prior knowledge like the design layout of VLSI wafer manufacturing process. This technique requires a golden template of the patterned wafer image under inspection which is obtained from the wafer image itself mixed to the layout design schemes. First a mapping between physical space and pixel space is needed. Then a template matching is applied for a more accurate alignment between wafer device and template. Finally, a segmented comparison is used for finding out possible defects. Results of the proposed method are presented in terms of visual quality of defect detection, any misalignment at topology level and number of correctly detected defective devices.

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

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.

Vibration Control of Scanning Electron Microscopes with Experimental Approaches for Performance Enhancement

A vibration isolator embedded in precision equipment, such as a scanning electron microscope (SEM), wafer inspection equipment, and nanoimprint lithography equipment, play a critical role in achieving the maximum performance of the equipment during the fabrication of nano/micro-electro-mechanical systems. In this study, the factors that degrade the performance of SEM equipment with isolation devices are classified and discussed, and improvement measures are proposed from the viewpoints of the measured image patterns and vibrations in comparison with the relevant vibration criteria. In particular, this study quantifies the image patterns measured using SEMs, and the results are discussed along with the measured vibration. A guide for the selection of mounting equipment is presented by performing vibration analysis on the lower mount of the dual elastic mount configuration applied to the SEM, as well as the image patterns analyzed with that configuration. In addition, design modifications for the mount and its arrangement are suggested based on impact tests and numerical simulations.