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Recommended by Jong-Shinn Wu
Advanced Module Process Development Division, Technology Development Center, Macronix International Company, Ltd., (MD420) No.16, Li-Hsin Road, Science-Based Industrial Park, Hsinchu 300, Taiwan
Received 23 June 2008; Accepted 26 August 2008
1. Introduction
As the dimension of devices continues to scale down, the Al patterning by dry etching becomes challenging due to insufficient amount of photoresist to leave for etch rate fluctuation [1]. A damascene process is the highly potential approach to avoid the metal dry etching problems [2]. However, it is known that switching Al to W or Cu involves additional investments, both in terms of equipments and process development efforts [3]. Since Gabriel et al. [4] and Stojakovic and Ning [5] adopted hard mask to pattern Al in the dry etching process, it is worth exploring Al dry etching with hard mask in our 75 nm nonvolatile memory technology and beyond. With developing the TEOS hard-mask-based Al patterning in our study, the etch defectivity is regarded as leading edge challenge in the manufacturing line. As illustrated in Figure 1, the defect types, referred to as "post hard-mask etch residue," "post metal etch residue," "blocked etch metal island," "particle," "bridging," "particulate bridging," and "corrosion," were found at the early stage of development. Interestingly, the major adders of post hard-mask etch residue, post metal etch residue, and blocked etch metal island were particularly high in the oxide-masked Al patterning but few in the conventional resist-masked Al patterning. From the observations of scanning electron micrographs as shown in Figure 1, these three defect types pose a tangible and substantial yield risk due to their subtle physical characteristics and high density on wafer. Hence, it is important to understand the behavior of these defect adders within the Al etching process sequence.
Examples of defect adders within the oxide-masked Al etching process sequence.
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This paper describes the identification of the foregoing defect adders. Among these defect adders, post hard-mask etch residue is commonly observed after the oxide hard-mask patterning followed by resist...