SSL Seminar Series 2001 No. 4
Title: X-ray Photoelectron Spectroscopy (XPS) and its application in interface study
Speaker: Dr. Pan Jisheng
Date: 16th February 2001, Friday
Time: 5:00-6:00pm
Venue: Physics Resource Room S13, 02-16

Abstract
X-ray Photoelectron Spectroscopy (XPS), also known as ESCA (Electron Spectroscopy for Chemical Analysis), is an extremely surface sensitive non-destructive technique that provides quantitative surface chemical state information for all elements except hydrogen and helium. It is the most established (since the mid-1960s) and widely used surface analysis technique. In this presentation, firstly, I will give you some basic knowledge of XPS such as its physical basis, why is the XPS technique surface sensitive? Chemical shifts, angle resolved XPS, quantification of XPS, small area XPS and Imaging XPS, XPS depth profile. Secondly, I will show you the development of XPS instrumentation. In this part, I will focus in introduction of ESCALAB220I-XL system in IMRE and some points in XPS measurement and data process such as charge compensation and referencing for insulators and spectral fitting. The purpose of these two parts of talk is hoped to give you a basic picture of XPS. Finally, I will talk my XPS study of interfacial reaction between Ta thin film and SiO2 when Ta as a diffusion barrier in the Cu/barrier/SiO2. It is well known that Cu is an attractive material for ULSI metallization due to its lower resistivity and higher electromigration resistance compared to Al and its alloys. However, the implementation of Cu metallization requires the use of a barrier layer since Cu diffuses easily into Si and SiO2, leading to an increase in device leakage. Also, Cu lacks the ability to adhere to SiO2 and most insulating substrates. Thus thin film layers should be used between Cu and SiO2 to improve the adhesion of Cu to the SiO2 layer. There has been a considerable effort to identify a suitable diffusion barrier for Cu metallization. Among these barriers, Ta-based barriers have been of increasing interest because Ta does not react with Cu and the diffusion of Cu through Ta into the oxidized Si substrate does not occur up to 700 oC. In the present study, Ta thin films of about 35 nm thick were investigated as a barrier material between Cu and SiO2 using X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). The detailed will be presented in this talk.

About speaker
Dr. Pan Jisheng received his B.Sc in physics from Hangzhou University in 1985 and M.Sc degree in nuclear physics from Shanghai Institute of Nuclear Research, Chinese Academy of Sciences in 1988 and was working there for 6 years. At Shanghai he focused his research on high-energy ion implantation of semiconductors, ion beam modification and sputtering of metal and alloy and surface modification of polymer. He obtained his PhD degree in surface science from National University of Singapore in 1998. Currently, he is working in Central Characterization Laboratory, IMRE. His areas of research interest are synthesis and characterization of thin films for microelectronic device fabrication, Ion beam nitridation of semiconductor surfaces and fluoride uptake in dental tissues. Dr. Pan has published more than 50 technical papers in his work area. He also has performed surface analysis for many microelectronics companies. He won the distinguished young investigator award of Chinese Academy of Sciences in 1990. He has been enlisted in the "Who's Who in the world 1998 (Marquis, USA)". He is a member of MRS (USA), IPS (Singapore), MRS (Singapore) and NSC (China).