Studies on interface states at ultrathin SiO2/Si(100) interfaces by means of x-ray photoelectron spectroscopy under biases and their passivation by cyanide treatment

Abstract

The energy distribution of interface states at ultrathin oxide/Si͑100͒ interfaces is obtained using a new method, i.e., x-ray photoelectron spectroscopy measurements under biases between the metal overlayer and the Si substrate of the metal-oxide-semiconductor ͑MOS͒ devices. Ultrathin thermal oxide layers formed at 450°C in oxygen have an interface state peak near the midgap and it is attributed to isolated Si dangling bonds with which no atoms in the oxide layer interact. On the other hand, thermal oxide layers formed at 650°C have a two-peaked structure, one peak above and the other below the midgap, and they are attributed to Si dangling bonds with which an oxygen or Si atom in the oxide layer interacts weakly. The density of the interface states, especially that near the midgap, decreases drastically by cyanide treatment, i.e., the immersion of Si in a KCN solution for a few seconds followed by a rinse in boiling water, performed before the oxide formation. It is suggested that cyanide ions penetrate into the Si, forming Si-CN bonds at structurally imperfect places. The cyanide treatment improves the electrical characteristics of the MOS tunneling diodes.

Catalytic decomposition of HCN on heated W surfaces to produce CN radicals

“…This decrease has been ascribed to the increase in defect states [2][3][4]. Recently, Kobayashi and his coworkers have developed a new method, a cyanide treatment, to reduce the defect states and their precursors in the semiconductor band-gap [6][7][8][9][10][11]. In this method, the semiconductor devices are immersed in KCN solutions containing crown-ether, typically 18-crown-6, under a positive bias to terminate the Si dangling bonds by CN.…”

“…However, such a decrease was completely suppressed, even after 25-h irradiation, for cyanide-treated samples. They have shown that this technique can be applied not only to a-Si:H, but also to SiO 2 /Si interfaces [6][7][8] and poly-crystalline silicon (poly-Si) [9,10].…”

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

“…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].…”

Improvement of Photovoltaic Conversion Efficiency and also Photoluminescence Efficiency of p-Cu2O/n-ZnO thin film heterostructures by Cyanide Treatment

“…That is to say, K + ions do not have direct contact with Cu 2 O, only CN -ions do. Details of the cyanide treatment were described elsewhere [6,7]. The scheme of reaction for the Cyanide treatment are described below.…”