Monitoring Roughness and Edge Shape on Semiconductors Through Multiresolution and Multivariate Image Analysis Pierantonio Facco, Fabrizio Bezzo, and Massimiliano Barolo Dipartimento di Principi e Impianti di Ingegneria Chimica, Universita ` di Padova, via Marzolo 9, 35131 Padova (PD), Italy Rajib Mukherjee and Jose ´ A. Romagnoli Gordon A. and Mary Cain Dept. of Chemical Engineering, Louisiana State University, Baton Rouge, LA 70803 DOI 10.1002/aic.11733 Published online March 27, 2009 in Wiley InterScience (www.interscience.wiley.com). Photolithography is one of the most important processes in the production of inte- grated circuits. Usually, attentive inspections are required after this process, but are limited to the measurement of some physical parameters such as the critical dimension and the line edge roughness. In this paper, a novel multiresolution multivariate tech- nique is presented to identify the abnormalities on the surface of a photolithographed device and the location of defects in a sensitive fashion by comparing it to a reference optimum, and generating fast, meaningful and reliable information. After analyzing the semiconductor surface image in different levels of resolutions via wavelet decomposi- tion, the application of multivariate statistical monitoring tools allows the in-depth ex- amination of the imprinted features of the product. A two level nested PCA model is used for surface roughness monitoring, while a new strategy based on ‘‘spatial moving window’’ PCA is proposed to analyze the shape of the patterned surface. The effective- ness of the proposed approach is tested in the case of semiconductor surface SEM images after the photolithography process. The approach is general and can be applied also to inspect a product through different types of images, different phases of the same production systems, or different processes. V V C 2009 American Institute of Chemi- cal Engineers AIChE J, 55: 1147–1160, 2009 Keywords: process monitoring, semiconductor manufacturing, multivariate statistical methods, multiresolution methods Introduction Photolithography is a process that selectively removes parts from a thin film using light, so that a geometric pattern can be transferred (often from a mask) to a light sensitive chemical (the resist) deposited on a substrate. This process is used during the fabrication of integrated circuits (IC) as well as in many other micro-fabrication processes (e.g., micro- compressors production 1 ). In particular, a microelectronics manufacturing process comprises an extensive sequence of complex semi-batch processes, among which photolithog- raphy is referred to as one of the most important. 2 In fact, photolithography: i) recurs up to 35 times for a given device; ii) defines the wafer critical dimension (CD) and the other Correspondence concerning this article should be addressed to J.A. Romagnoli jose@lsu.edu. Jose ´ A. Romagnoli jose@lsu.edu. V V C 2009 American Institute of Chemical Engineers AIChE Journal 1147 May 2009 Vol. 55, No. 5