AVS 46th International Symposium
    Thin Films Division Monday Sessions
       Session TF-MoP

Paper TF-MoP27
XPS and AES Investigation on the Oxidation Resistance of Plasma-treated Copper Leadframe

Monday, October 25, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: R.G. Krishnan, Institute of Microelectronics, Singapore
Authors: A. Wong, Nanyang Technological University, Singapore
R.G. Krishnan, Institute of Microelectronics, Singapore
G. Sarkar, Nanyang Technological University, Singapore
Correspondent: Click to Email
Copper is widely used as a material in the microelectronic plastic packaging and IC interconnect applications. The oxidation of copper to form oxide due to microelectronic processing can result in poor copper metal to epoxy mold compound (Cu/EMC) bonding causing package delamination which compromises package reliability. Besides, metallization material problems such as increment in signal transmission delays, decrease power dissipation and decrease reliability to electrical and thermal stress migration failures can occur. Plasma treatment of copper is believed to be able to enhance its oxidation resistance. Based on the x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) results, it was possible to confirm firstly, the successful incorporation of C and N into a copper film above the copper substrate using plasma treatment and secondly, the change in oxidation resistance of this film as a result of the treatment. Thickness measurements from AES depth profiles also confirmed the dominant influence the film thickness have on the enhancement of oxidation resistance in the film as compared to a small change in film stoichiometry. XPS and AES analyses show that once the film was heated at 250@super o@C, the N/Cu (atomic concentration) ratio of the film decreased from 1.074 to 0.635. Heating at 300@super o@C cause further decaying of the N/Cu ratio to to 0 which is confirmed by the disappearance of the XPS N 1s signal. There is no difference in the binding energy of the XPS Cu 2p3/2 signal of the pristine copper and the treated copper. The oxidation of pristine copper at 250 °C can be seen from the shift of the XPS Cu 2p3/2 binding energy at 932.70 eV to 933.60 eV and an increasing Full-width-half-maxima (FWHM) from 1.00 eV to 3.00 eV. However, these are not observed for the oxidation-resistant film at 250 °C as there is a delay in the oxidation onset temperature (shown by the shift in binding energy and increase in FWHM of the XPS Cu 2p3/2 spectra) by at least 50 °C, which depends on the film thickness. The surface analysis data and the oxidation resistance of the film are finally correlated and discussed.