From Large Research Instruments To An Industrial Control: X-ray Photoelectron Spectroscopy Characterizations Of Advanced Technology Gate Stack

摘要

With the continuous downscaling of integrated circuit, metrology techniques have to face new challenges to support the development of advanced technology nodes. One of them is the composition determination of nanometer thick multilayers films. Since the 32nm node, the SiO_2 gate insulator has been replaced by the High-k Metal Gate (HKMG) film stack [1]. For the 14nm node, this HKMG stack is composed of a high-k HfON layer deposited on a SiON interfacial layer (IL), to prevent the formation of a bad quality SiO_2 layer between the HfON layer and the channel [2]. To reach the transistor specifications, thickness and composition of the different deposited layers must be precisely controlled. For the HKMG stack, the amount of nitrogen in the HfON and SiON layers is specifically critical. Nevertheless, for such thin layers, conventional optical metrology techniques, well suited for volume measurements, are difficult to implement. This is why X-ray based techniques, more suited for surface characterization, are increasingly used. X-Ray Photoelectron Spectroscopy (XPS) is a well-established method for the analysis of ultrathin films thanks to its surface sensitivity (<100A) and its ability to chemically characterize samples [3]. Hence, in this work we present three different XPS systems, used to characterize the HfON/SiON HKMG stack: a Nano Angle Resolved Photoelectron Spectroscopy (Nano-ARPES) system using the SOLEIL synchrotron ANTARES beam line [4], a Thermo Fisher Scientific laboratory pARXPS (parallel Angle Resolved XPS) system and an in-line NOVA system. The Nano-ARPES and the pARXPS, thanks to the angular information, can provide depth resolved information on the chemical state of near-surface layers [5]. The in-line NOVA system, optimized for an industrial use, can quickly and accurately provide ultra-thin film stack information. These three tools, based on the same technique, exhibit different way to implement it, whether it is resolution driven or used in a production purpose (Figure 1).