Characterization of the post dry-etch cleaning of silicon for Ti-self-aligned silicide technology

The Si surface after reactive ion etching (RIE) and different cleaning proc edures was characterized by angle resolved X-ray photoelectron spectroscopy , high-resolution transmission microscopy, and atomic force microscopy. It was shown that CFx polymers, silicon carbides (Si-C bonds), and chemisorbed fluorine (Si-F), cover the silicon surface after RIE in a CHF3/C2F6 mixtur e. The last two residues penetrate the surface layer of a silicon substrate . CFx polymers are removed by oxygen plasma but Si-C and Si-F bonds related residues cannot be removed by "oxygen plasma/diluted HF" treatment. These compounds can be removed only by additional etching of the silicon surface layer. According to our experimental conditions a silicon consumption of 2. 8 nm was enough to eliminate these compounds. By comparing different cleani ng recipes and conditions it was found that O-2-plasma/HF/APM (ammonia-hydr ogen peroxide mixture) provides the best cleaning characteristics. APM remo ves fluorine and carbon contamination by precise, controlled etching of sil icon with high etch selectivity toward an SiO2 spacer. The silicon surface after the cleaning is quite smooth. It was demonstrated that the post space r-etch cleaning of O-2-plasma/HF/APM is a robust process for Ti-salicide te chnology with respect to the reduction of the leakage current between poly- Si and source/drain. (C) 1999 The Electrochemical Society. S0013-4651(98)06 -051-0. All rights reserved.