DIFFUSION BARRIER PERFORMANCE OF THIN Cr FILMS IN THE Cu/Cr/Si STRUCTURE Y. Ezer 1 *, J. Ha ¨rko ¨nen 1 , V. Sokolov 1 , J. Saarilahti 2 , J. Kaitila 2 , and P. Kuivalainen 1,2 1 Electron Physics Laboratory, Helsinki University of Technology, P.O. Box 3000, 02150 HUT, Helsinki, Finland 2 VTT Electronics, P.O. Box 1100, 02044 VTT, Helsinki, Finland (Refereed) (Received December 2, 1997; Accepted February 18, 1998) ABSTRACT The Cu/Cr/Si structure was studied for thermal stability using thin Cr layers as a barrier in the range of 10 to 40 nm, between 250 and 500°C for 30 min. Investigations using sheet resistance method, deep level transient spectros- copy (DLTS), X-ray diffraction (XRD) analysis, Rutherford backscattering spectroscopy (RBS), and adhesion tests were carried out, to reveal the behav- ior of Cu and Cr in the Cu/Cr/Si structures. It is shown that even a 10-nm thin Cr layer preserves the multilayer structure up to 400°C and that Cu silicide formation is observed only after annealing at 450°C. However, as found by DLTS, compared with the conventional characterization techniques, Cu mi- gration into the structure reduces the effectiveness of the Cr layers as a diffusion barrier at 50°C. © 1998 Elsevier Science Ltd KEYWORDS: A. electronic materials, A. multilayers, A. thin films, B. sput- tering INTRODUCTION Currently, predominant Al-based alloys cannot meet the new requirements for intercon- nections set by downscaling device dimensions in submicron ULSI technology. Copper with its record-high conductivity has apparent advantages as an interconnection material. *To whom correspondence should be addressed. Materials Research Bulletin, Vol. 33, No. 9, pp. 1331–1337, 1998 Copyright © 1998 Elsevier Science Ltd Printed in the USA. All rights reserved 0025-5408/98 $19.00 + .00 PII S0025-5408(98)00117-2 1331