Problems of and Solutions for Coating Techniques for TEM Sample Preparation on Ultra Low-k Dielectric Devices after Progressive-FIB Cross-section Analysis

This paper presents the impact of coating techniques for TEM sample preparation on ultra low-k dielectric devices after progressive-FIB cross-section analysis. The ultra low-k materials used as inter-metal dielectrics (IMD) has a k value less than 2.6. In the experimental study on three commonly used protective coatings (sputtered Pt, e-beam deposited insulator and PECVD oxide) for the 28 nm technology node with ultra low-k IMD, PECVD oxide coating was found to be an ideal choice for the TEM sample preparation with the least low-k dielectric deformation or damage. In-situ e-beam deposited insulator in a dual-beam FIB tool equipped with a GIS for insulator deposition is a convenient and commonly used method. However, the e-beam can introduce a considerable damage to the ultra low-k IMD during the e-beam deposition. Sputtered Pt can achieve a damage-free profile of an ultra low-k IMD, but we have to sacrifice certain portion of the target area in the final FIB cleaning process during TEM sample preparation. This makes sputtered Pt not suitable for the TEM sample preparation on a defect with a small size (<100 nm).