Decrease in the leakage current density of Si-based metal–oxide–semiconductor diodes by cyanide treatment

Abstract

Crown-ether cyanide treatment, which includes the immersion of Si in KCN solutions containing 18-crown-6 molecules, is found to greatly decrease the leakage current density of Si-based metal–oxide–semiconductor (MOS) diodes. The decrease by one order of magnitude for the single crystalline Si-based MOS diodes is attributable to the elimination of Si/SiO2 interface states by reaction with cyanide ions and formation of Si–CN bonds. The reduction in the leakage current density by two orders of magnitude is caused for polycrystalline Si-based MOS diodes, and this decrease is attributed to the passivation of trap states in poly-Si as well as the interface states.

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

“…Due to the high bond energy, the Si-CN bonds are not ruptured upon heating at 800°C, and UV and visible light irradiation. The passivation of interface states results in a decrease in the density of a leakage current flowing through ultrathin SiO 2 layers [17]. Defect states present in poly-crystalline Si can also be passivated by CN À ions [18].…”

“…The treatment with the KCN aqueous solutions has already been found to eliminate Si/SiO 2 interface states [15][16][17] and defect states in polycrystallilne [18] and amorphous Si [19], resulting in the improvement of electrical characteristics of metal-oxide-semiconductor (MOS) diodes. We have recently found that KCN solutions of methanol have an ability of removing Cu and Ni contaminants from Si surfaces [20].…”

Complete prevention of reaction at HfO2/Si interfaces by 1nm silicon nitride layer

“…A leakage current flows via interface states, resulting in an increase in its density [34,35]. Another reason for the high leakage current density may be the formation of Hf silicide islands which form thin HfO 2 regions and/or minute electrical contacts between Si and Al.…”

Si cleaning method without surface morphology change by cyanide solutions

“…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. We have also found that CN À ions selectively react with semiconductor defect states such as Si dangling bonds, resulting in the defect passivation [21][22][23][24]. The defect passivation by CN À ions greatly improves www.elsevier.com/locate/apsusc Available online at www.sciencedirect.com Applied Surface Science 254 (2008) 3715-3720 conversion efficiencies of single crystalline Si [21], polycrystalline Si [22], and amorphous Si [23] solar cells, and decreases the density of a leakage current flowing through an ultrathin SiO 2 layer of metal-oxide-semiconductor (MOS) diodes [24].…”