Improved copper detection in hydrofluoric acid by recombination lifetime measurements on dedicated silicon substrates

Boehringer, M.; Hauber, J.

doi:10.1063/1.1436272

Cited by 10 publications

(8 citation statements)

References 14 publications

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“…(3) For species present within a few nm below the substrate surface, the TXRF intensity has a maximum at or above the critical angle. 17 (4) In the case of homogeneously distributed species throughout the substrate, the TXRF intensity is low below the critical angle and increases rapidly above it. 31,32 Figure 6B shows observed results for the dependence of the TXRF signal intensity of the Cu Ka peak on the X-ray incident angle with respect to the surface-parallel direction.…”

Section: Cleaning Solutionsmentioning

confidence: 98%

“…4,5 Cu has been used as alternative wiring materials to aluminum alloys due to the lower resistivity. Cu induces energy levels near the Si midgap, which greatly decreases the carrier lifetime.…”

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confidence: 99%

“…Metallic contaminants even with a minute concentration (i.e., <1 Â 10 11 atoms/cm 2 ) cause degradation of semiconductor device characteristics, e.g., an increase in the interface state density, 1 shifts of the threshold voltage, 2 and decreases in the minority carrier diffusion length 3 and the minority carrier lifetime. 4,5 Cu has been used as alternative wiring materials to aluminum alloys due to the lower resistivity. Cu induces energy levels near the Si midgap, which greatly decreases the carrier lifetime.…”

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confidence: 99%

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Chemical States of Copper Contaminants on SiO2 Surfaces and Their Removal by ppm-order HCN Aqueous Solutions

Takahashi

Higashi

Ozaki

et al. 2011

J. Electrochem. Soc.

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Cu contaminants of $1 Â 10 13 atoms/cm 2 on SiO 2 surfaces can be removed to less than $3 Â 10 9 atoms/cm 2 by immersion in 3 ppm HCN aqueous solutions within 2 min at room temperature. The Cu removal process by HCN aqueous solutions consists of the initial fast and subsequent slow steps. X-ray absorption fine structure (XAFS) measurements with the total reflection X-ray fluorescence (TXRF) geometry (TXRF-XAFS) have been used for determination of chemical states of Cu contaminants before and after cleaning with HCN aqueous solutions. Cu contaminants are composed of Cu þ and Cu 2þ species, latter being present above the former. In the former species, a Cu atom is linearly bound to two oxygen atoms (Cu 2 O-like species), while in the latter species, a Cu atom is bound to four equatorial oxygen atoms and two axial oxygen atoms [Cu(OH) 2 -like species]. CN À ions react with outer Cu(OH) 2 Àlike species with a high rate, leading to initial fast removal of Cu contaminants. When the Cu concentration decreases to $1 Â 10 10 atoms/cm 2 , Cu þ species becomes a main species and its removal rate becomes much lower.Metallic contaminants even with a minute concentration (i.e., <1 Â 10 11 atoms/cm 2 ) cause degradation of semiconductor device characteristics, e.g., an increase in the interface state density, 1 shifts of the threshold voltage, 2 and decreases in the minority carrier diffusion length 3 and the minority carrier lifetime. 4,5 Cu has been used as alternative wiring materials to aluminum alloys due to the lower resistivity. Cu induces energy levels near the Si midgap, which greatly decreases the carrier lifetime. Therefore, it should be removed completely. For next generation devices, the International Technology Roadmap for Semiconductors (ITRS) (Ref. 6) suggests that surface concentrations of metal contaminants should be less than 5 Â 10 9 atoms/cm 2 . During cleaning, surface etching should be avoided since it may result in roughened surfaces and formation of defect states. To clean surfaces of Si devices, wet cleaning techniques based on the RCA cleaning method, i.e., cleaning with hydrogen peroxide plus ammonia aqueous solutions (APM) and hydrochloric acid plus hydrogen peroxide mixture (HPM), 7 have been usually employed. To avoid re-adsorption of metal species, incorporation of chelating agents such as ethylene-diamine-tetraacetic acid, 8,9 1,2-cyclohexane-diamine-tetraacetic acid, 8,10 and tetramethylammonium hydroxide 11 in the cleaning solutions has been proposed. The HPM cleaning solutions can remove metal contaminants. However, the HPM cleaning method should be performed at elevated temperatures at around 80 C using relatively high concentration (i.e., a few %) solutions, since the cleaning solutions do not possess high ability of metal removal.We have developed semiconductor cleaning solutions containing cyanide ions (CN À ). 12-19 CN À ions form metal-cyanide complex ions, leading to removal of metal species from surfaces without etching. Moreover, because of the high reactivity of CN À ions with metal...

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Section: Cleaning Solutionsmentioning

confidence: 98%

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confidence: 99%

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confidence: 99%

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Chemical States of Copper Contaminants on SiO2 Surfaces and Their Removal by ppm-order HCN Aqueous Solutions

Takahashi

Higashi

Ozaki

et al. 2011

J. Electrochem. Soc.

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“…on semiconductor surfaces seriously degrade semiconductor device characteristics, e.g., increasing the interface state density [1], decreasing the minority carrier diffusion length [2], the minority carrier life time [3,4], shifting the threshold voltage [5], etc., even when their concentrations are less than 10 10 atoms/cm 2 . Copper has been used as interconnect instead of aluminum (Al) alloys, and when the Si surfaces are contaminated by Cu, it easily diffuses into Si bulk even at room temperature [6] and forms deep levels in the Si band-gap [7], causing an increase in the leakage current density through gate oxide layers, especially in the case of ultrathin (i.e., less than 3 nm) SiO 2 layers [8].…”

Section: Introductionmentioning

confidence: 99%

Si cleaning method without surface morphology change by cyanide solutions

Takahashi¹,

Liu²,

Narita³

et al. 2008

Applied Surface Science

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“…Since a minute concentration of Cu seriously degrades the device characteristics, i.e., decreasing the minority carrier diffusion length [3] and the minority carrier life time [4,5], increasing the interface state density [6] and surface roughness [7,8],…”

Section: Introductionmentioning

confidence: 99%