Dual Damascene Reactive Ion Etch Polymer Characterization through X-Ray Photoelectron Spectroscopy for 65 nm and 45nm Te
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Dual Damascene Reactive Ion Etch Polymer Characterization through X-Ray Photoelectron Spectroscopy for 65 nm and 45nm Technology Nodes Samuel S. Choi, Chet Dziobkowski1, Leo Tai1 IBM TJ Watson Research Center, 2070 Route 52, Hopewell Junction, NY 12533, U.S.A. 2 IBM Microelectronics SRDC, 2070 Route 52, Hopewell Junction, NY 12533, U.S.A. ABSTRACT At 65nm and beyond technology nodes, copper interconnect formation in dual damascene integration is continually challenged from a polymer management perspective. Highly polymeric plasma chemistry is required to reduce line edge roughness, shape physical profile, and control critical dimension across a 300mm wafer. But too much fluorocarbon deposition on a wafer results in poor defects yield. In this paper, X-ray photoelectron spectroscopy (XPS) characterization technique is used to quantify and to optimize a metal line reactive ion etch process to increase electrical opens yield. A reduction of 2 at.% in carbon mass results in a Do (defects/cm2) improvement from > 2.0 to less than 1.0. This result is realized without a shift to the trench physical profile which is important for reliability performance. Moreover, with a shorter turnaround time of XPS characterization compared to electrical hardware splits, quicker yield learning cycle is realized for both RIE process and module integration. INTRODUCTION Copper interconnect process development and manufacturing are extremely challenged as technology node’s critical dimension (CD) shrinks and chip functional yields must be met to profit [1]. Much effort is devoted to RIE pattern transfer to meet each technology nodes’ critical dimension specifications. Fluorocarbon species are extensively used in RIE to shrink and to control CD [2]. A consequence of too much fluorocarbon (e.g. CFx) on a wafer is manifested in a Photo-Limiting Yield (PLY) scan detection of hollow metal, Fig. 1. Hollow metal is a killer defect that degrades electrical open yield.
Figure 1: Corroded copper lines due to residual RIE polymer. Unfortunately, much less effort is devoted for manufacturability of a RIE process in relation to electrical chip yield. Namely, how can a RIE process be optimized such that both technology and electrical yield requirements are met? This paper addresses this
need. Furthermore, new and rapid turnaround characterization techniques are in need to optimize a RIE process that is scalable to the next technology node [3]. We propose the use of X-ray photo-electron spectroscopy (XPS) surface analytic technique as an additive tool for RIE process optimization. The XPS’s soft x-ray energy is less energetic than an electron beam, hence mono-layers of fluorine detection is possible. Moreover, unlike Auger electron spectroscopy, XPS’s large probe beam area (10 µm2) provides ample sampling desirable for 300 mm wafers [4]. Standard scanning electron micrograph (SEM) analysis is still used to confirm physical profile shifts associated with RIE process changes. Lastly, electrical split of 65nm RIE processes shows enhanced elect
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