Léon Winters, Philips Semiconductors; and Joseph Zahka, Millipore During the manufacture of semiconductor devices, the wafer surface is exposed at numerous process steps to potential sources of contamination, including particles, inorganic ions, and organic residues. To ensure a stable production process, it is necessary to maintain a constant, low baseline surface contamination level. Wet cleans are commonly used to achieve that objective. The effectiveness of a wet clean is determined by three main parameters: its intrinsic contamination level (i.e., the level of contaminants and roughness that is added by the cleaning sequence itself), its capability to remove contaminants and to smooth out surface roughness, and its robustness. A clean is considered robust when it achieves the same low baseline contamination levels on wafers even if high levels of contaminants occasionally appear in the cleaning sequence. The fact that the RCA cleaning sequence, improved with the introduction of megasonics and dilute chemistry, is still in use in front-end processing after 30 years implies that it adheres to these cleaning parameters. The peroxide-based RCA technique uses two standard clean (SC) chemical mixtures. The SC-1 chemistry consists of ammonium hydroxide, hydrogen peroxide, and ultrapure water (UPW), while SC-2 consists of hydrochloric acid, hydrogen peroxide, and UPW. The wafers are also rinsed with UPW following both the SC-1 and SC-2 cleaning steps. The optimization of the RCA process has been intensively investigated, and researchers have found that the post-RCA wafer surface levels of several metal contaminants depend strongly on the metal concentration in UPW. The study discussed in this article evaluated the effectiveness of a filter/purifier at reducing the metal concentration of UPW and, consequently, the wafer surface metal concentration after an RCA clean. Because the filter/purifier had already been tested in a single-tank wet bench configuration, this study focused on its performance in a
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Topics of Interest
As the semiconductor industry moves toward the 256-Mb chip generation with 0.15-µm feature sizes on 300-mm wafers, wet chemical cleaning remains essential to the removal of particles and metallic...
Izzy K. Bansal, M/A-Com, a Tyco Electronics company Experiments involving various surface-cleaning methods demonstrate that an ultradilute approach can reduce chemical consumption, lower costs, and...
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Anurag Kumar and Mark J. Camenzind, Organic contamination deposited on wafer surfaces from ultrapure water (UPW) can seriously undermine wafer-cleaning efficiency, which leads to nonuniform etching.
Christiane Gottschalk, MKS Instruments, ASTeX; and Juergen Schweckendiek, ASTEC ), an allotrope of oxygen, is a highly reactive gaseous oxidizing agent that absorbs harmful ultraviolet (UV) radiation,...