Si cleaning method without surface morphology change by cyanide solutions

Ultra-thin silicon oxide layers on crystalline silicon wafers: Comparison of advanced oxidation techniques with respect to chemically abrupt SiO 2 /Si interfaces with low defect densities

“…This investigation is motivated by the findings, that oxidation in HCl minimizes metallic contamination and avoids defects in the oxide layer [4]. Compared to Si substrates with oxides grown in ultra-pure water, RCA solutions [30], or nitric acid (NAOS), Si surfaces oxidized in diluted HCl solution (WCOHCl) may achieve a higher level of passivation after post-deposition thermal treatments, such as annealing at 425 °C and firing at 860 °C as applied in Si solar cell industry [26,31,32]. Wetchemically prepared oxide layers were found to include sub-stoichiometric silicon oxides (i.e.…”

“…oxidation in boiling azeotropic HNO 3 [24,25]]. Ultra-thin NAOS oxides were utilized for interface conditioning in Si devices and solar cells after subsequent defect passivation by aqueous HCN solution at room temperature [26] and post metallization annealing processes (PMA) [27]. To minimize chemical consumption and the number of process steps, in this study also a dissolved solution of hydrochloric acid (HCl) in ultra-pure deionized water [28,29] was investigated as an alternative to oxidation in concentrated solutions.…”

Improved Si/SiOx interface passivation by ultra-thin tunneling oxide layers prepared by rapid thermal oxidation

“…The defect distribution resembles a nearly intrinsic energetic distribution D it (E). So far, nearly similar results have only been reported with significantly more complex oxidation procedures which require a complex sequence of surface pre-treatment steps prior to oxidation, like plasma oxidation under ultra high vacuum (UHV) with elaborate surface pre-treatment [44,45,48], surface pre-conditioned multi-step NAOS oxidation with subsequent passivation in hydrogen cyanide (HCN) and post metallization anneal (PMA) [49][50][51], or complex multi-stage thermal oxidation with surface preconditioning for MOS technology [37].…”

Metal Removal and Defect Passivation Performed on Si Wafers for Solar Cell Use by HCN Treatments

“…We have already reported that HCN solutions possess high activity for metal removal, which activity enables cleaning with ultra-low concentration solutions at room temperature. [6][7][8][9][10] Since metal species removed from surfaces are present in the form of metal-cyanide complex ions (e.g., Cu(CN) 4 3− ) which are extremely stable in aqueous solutions, 11 re-adsorption of the removed metals does not proceed, which makes it possible to use the cleaning solutions repeatedly. Avoidance of re-adsorption also enables to remove metal contaminants to extremely low levels.…”