Reaction of cyanide ions with copper on Si surfaces and its use for Si cleaning

Liu, Yueh-Ling; Fujiwara, Naozumi; Iwasa, Hitoo; Takahashi, Masatoshi; Imai, Shigeki; Kobayashi, Hikaru

doi:10.1016/j.susc.2006.01.017

Cited by 8 publications

(10 citation statements)

References 26 publications

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“…8 Etching of SiO 2 does not occur at all even in such a high pH HCN aqueous solution. 7 Moreover, it is found that HCN aqueous solutions have the capability of removing various metals such as Cu, Fe, Cr, Co, Mn, and Ca from SiO 2 surfaces. It is also evident that the HCN aqueous solutions can dissolve metal Ni from the following experimental result.…”

Section: H18mentioning

confidence: 99%

“…3,4 We have recently developed semiconductor cleaning solutions which contain cyanide ions ͑CN − ͒. [5][6][7][8] Due to the strong reactivity of CN − ions with metal species, semiconductor cleaning can be performed at room temperature using low concentration ͑e.g., 0.2%͒ solutions. Due to the large complex stability constant of CN − ions compared with other chelating agents, 9 metal-cyanide complex ions in the cleaning solutions are not readsorbed on the surface, which makes it possible to remove metal contaminants completely and to use the cleaning solutions repeatedly.…”

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Mechanism of Ni Removal from Si Materials Using Hydrogen Cyanide Aqueous Solutions

Liu

Takahashi

Kobayashi

2007

J. Electrochem. Soc.

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The mechanism of Ni removal from SiO 2 -covered Si specimens by HCN aqueous solutions has been investigated by means of total reflection X-ray fluorescence spectroscopy and X-ray photoelectron spectroscopy measurements. Ni contaminants on the SiO 2 surface are present in the form of SiO-NiOH. The removal mechanism consists of two steps, i.e., an initial fast process followed by a slow process. The rate-determining steps of both the processes are of the first order with respect to the concentration of cyanide ions ͑CN − ͒. The fast and slow processes are tentatively attributed to the removal of SiO-NiOH on terraces and in sub-nanometer pores, respectively. The cleaning ability of the HCN aqueous solutions is much better than ammonia aqueous solutions, because of high reactivity to form nickel-cyanide complex ions and avoidance of readsorption of Ni͑CN͒ 4 2− complex ions in the solutions.Complete removal of metal contaminants is required for the fabrication of Si devices because heavy metals such as Cu, Fe, Ni, and Co form trap states in the Si bandgap. 1 In the fabrication process of Si devices, surface contaminants are usually removed by the RCA method, i.e., alkaline and acid solutions containing hydrogen peroxide. 2 The conventional RCA method requires high concentration ͑e.g., ϳ5%͒ cleaning solutions and heating at 50 ϳ 80°C. Moreover, the RCA method causes surface etching, which makes the device fabrication processes complicated and possibly forms rough surfaces and defect states. To avoid etching, RCA cleaning solutions using dilute varieties are recently employed in LSI fabrication processes.Solutions containing chelating agents such as EDTA are found to have an effect to prevent readsorption of metal species in cleaning solutions. 3,4 We have recently developed semiconductor cleaning solutions which contain cyanide ions ͑CN − ͒. 5-8 Due to the strong reactivity of CN − ions with metal species, semiconductor cleaning can be performed at room temperature using low concentration ͑e.g., 0.2%͒ solutions. Due to the large complex stability constant of CN − ions compared with other chelating agents, 9 metal-cyanide complex ions in the cleaning solutions are not readsorbed on the surface, which makes it possible to remove metal contaminants completely and to use the cleaning solutions repeatedly. We have already found that CN − ions selectively react with semiconductor defect states such as Si dangling bonds, resulting in the defect passivation. [10][11][12][13][14] The defect passivation by CN − ions greatly improves varioustype Si solar cells 10-13 and decreases the density of a leakage current flowing through an ultrathin SiO 2 layer of metal-oxidesemiconductor ͑MOS͒ diodes. 14 Therefore, cyanide solutions can be applied to not only semiconductor cleaning but also defect passivation.In the present study, HCN aqueous solutions were found to possess a great effect of removing Ni contaminants and the removal mechanism is investigated by means of total reflection X-ray fluorescence spectroscopy ͑TXRF͒ and X-ray pho...

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confidence: 99%

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Mechanism of Ni Removal from Si Materials Using Hydrogen Cyanide Aqueous Solutions

Liu

Takahashi

Kobayashi

2007

J. Electrochem. Soc.

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“…Several defect passivation methods applicable to Si materials have been developed, e.g., hydrogen plasma treatment [1,2], forming gas annealing [3,4], deposition of a hydrogen-containing silicon nitride layer [4,5], wet-chemical passivation [6], etc. We have also developed a method of defect passivation for semiconductor devices called cyanide method [7][8][9][10][11][12][13] which can simultaneously remove metal contaminants [14][15][16][17][18][19]. The cyanide method simply includes immersion of Si materials in di-lute cyanide solutions such as HCN aqueous solutions at room temperature.…”

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confidence: 99%

Passivation of defect states in surface and edge regions on pn-junction Si solar cells by use of hydrogen cyanide solutions

et al. 2009

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“…We have recently developed a cleaning method for the removal of heavy metal contaminants such as Cu and Ni using cyanide solutions [16][17][18][19][20]. The semiconductor cleaning can be performed at room temperature using dilute (e.g., $0.03 wt%) solutions due to strong reactivity of cyanide ions (CN À ) to form stable metal-cyano complex ions.…”

Section: Introductionmentioning

confidence: 99%