IN-SITU X-RAY PHOTOEMISSION SPECTROMICROSCOPY OF ELECTROMIGRATION IN PATTERNED AL-CU LINES WITH MAXIMUM H.H. SOLAK*, G.F. LORUSSO*, S. SINGH*, F. CERRINA*, J.H. UNDERWOOD**, AND P. BATSON** Dept. of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA Center for X-ray Optics, Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA ABSTRACT We report the application of a unique photoemission spectromicroscope (MAXIMUM) to the study of electromigration phenomena in Al-Cu interconnects. MAXIMUM is a scanning type photoemission microscope that uses multilayer-coated optics to focus 130 eV x-rays to a sub- 0.1 [tm spot. An electron energy analyzer collects photoelectrons in a chosen spectral region of interest to form an image of the sample that is sensitive to chemical states of elements on the sample surface. Al-Cu lines were characterized by spectromicroscopy techniques before and after electromigration stressing in the UHV environment of the microscope chamber. We present spectro-micrographs showing the chemical and structural changes on Al-Cu line surfaces as a result of the electromigration process. INTRODUCTION Electromigration is one of the major reliability concerns in microelectronics industry because of its damaging effects on metal interconnect lines. Al, which has been the industrial choice for interconnect metallization, is especially susceptible to this damage mechanism. As the interconnect line width and thickness' continue to shrink electrical current densities increase together with the reliability problem [1]. Addition of small amounts of Cu (0.5-4%) to Al has been found to increase the lifetimes of interconnect lines against electromigration damage significantly and it is practiced commonly in industry [2]. However, a consensus still has not been reached upon the mechanism by which Cu slows down electromigration. One great source of difficulty is the low solubility of Cu in Al, and existence of different phases at operation and test conditions. Most of the Cu added to Al lines is found in the (0) A1 2 Cu phase precipitates under equilibrium conditions. In some experiments grain boundaries were also shown to be rich in Cu [3]. The dominant path for electromigration is through grain boundary networks and Cu must be effective in slowing down the electromigration along grain boundaries to cause the observed effect [4]. Therefore it is essential to obtain information on the Cu content of grain boundaries, its chemical state and the dynamics of Cu distribution between grain boundaries, grains and A1 2 Cu precipitates during process, operation and test conditions. Photoemission spectroscopy is a powerful method in studying physical and chemical properties of solid surfaces. However the sampling area is ordinarily too large to obtain spatially resolved information on the scale that is necessary for analysis of interconnect lines. MAXIMUM, a spectromicroscope with chemical sensitivity and sub 0. l.tm spatial resolution, installed on Beamline 12.0 at the ALS is a suitable tool to study this problem [5]. It can map the distribution of an element and can differentiate chemical states of the same element (like 39 Mat. Res. Soc. Symp. Proc. Vol. 516 01998 Materials Research Society