J. S. Luo, L. Y. Huang, W. L. Gu, J. D. Russell, Inotera Memories, Inc., Taoyuan, Taiwan

Summary: Transmission electron microscopy (TEM) is more and more important on the structure analysis and characterization of materials for process evaluation and failure analysis in Integrated Circuit (IC) industry with device shrinkage. The sample preparation is critical to TEM analysis success. In general, most of TEM analyses were performed on cross section TEM (XTEM) samples, for instance, line monitoring, construction analysis, embedded defects analysis, etc. Therefore, efficient XTEM sample preparation is essential to TEM analysis for semiconductor industry to perform yield improvement and metrology monitoring. At present, there are many methods to be used to prepare XTEM samples. Among those sample preparation methods, FIB milling using Ga ions is widely used in sample preparation for scanning electron microscopy (SEM) and TEM analysis, especially in localization and investigation of failures or defect analysis. In general, a protection layer, such as Pt or oxide layers, has to be deposited onto specific area using FIB for avoiding ion damage, curtain effect and to reduce the amount of rounding of the top of a TEM lamella during FIB milling. However, a 20-30 nm mixing amorphous layer was formed at the interface of the protection layer and sample. It is a problem to analyze the surface defect or structure, which is just a few nm or less thick on the surface, because the defect or structure will be changed or damaged during a protection layer deposition. Backside polishing is a good choice to overcome the mixing or damage layer. In this paper, a novel method of XTEM sample preparation is demonstrated for specific surface defect analysis using backside polishing. Using our novel sample preparation method, a whole surface defect or structure was localized and then analyzed by TEM successfully. The details of new backside XTEM sample preparation method and few more examples will be carried out in this full paper.