Influence of Cu on the native oxide growth of Si

Abstract

The influence of Cu on the native oxide growth on Si wafers was investigated by means of x-ray photoelectron spectroscopy and high-resolution electron energy loss spectroscopy (HREELS). The Cu coverage on the Si wafers was varied from 1012 cm−2 to about half a monolayer by adding Cu to aqueous HF in the ppm range. Immediately after the HF treatment no SiO2−x component (chemical shift ≳3.4 eV) can be measured by XPS. The chemical surface composition as characterized by HREELS is practically the same as for noncontaminated HF. A short additional water rinse of 2 min changes the chemical surface state of the Si wafers significantly. For Cu coverages more than about 1% of a monolayer, a pronounced initial oxide growth was noticed already after a 2-min water rinse with the oxide thickness depending on the amount of Cu coverage present on the Si surface. The oxide growth kinetics after storage of Cu-contaminated Si surfaces in air was studied for storage times up to 1 year. With almost no change in the chemical surface state visible directly after the HF treatment, however, an enhanced roughness of the Si wafer was noticed. The copper-induced enhancement of the oxidation of the silicon surface in combination with the oxide removal of the HF leads to an etching of the Si wafer.

Leakage Current Distribution and Dielectric Breakdown of Cu-Contaminated Thin SiO[sub 2]

“…These results indicate that the residual hillocks consisted of a thick SiO 2 film. Reports that the oxidation of silicon is accelerated by the Cu particles 28 and Cu 3 Si 29,30 support our experimental results. We conclude that the thick SiO 2 film grown under the Cu particles suppressed the oxide leakage current.…”

Spectroscopic Studies on Electroless Deposition of Copper on a Hydrogen-Terminated Si(111) Surface in Fluoride Solutions

“…25,26 These results imply that rinsing with Milli-Q water accelerates the surface oxide formation on the Cu-deposited Si wafer surface, as reported previously. 6,7 At the same time, the partially fluorinated Si species formed during the immersion in the NH 4 F solution containing Cu 2ϩ are converted to SiO 2 by a Milli-Q water rinse.…”

“…Compared to the electroless copper deposition observed on the H-Si͑100͒ surface, [5][6][7] the copper seemed to be more difficult to deposit on the H-Si͑111͒ surface in dilute HF solution containing Cu 2ϩ . This may be related to the stable surface structure of the H-Si͑111͒ substrate.…”

“…[1][2][3] Many studies on Cu impurity have been carried out because Cu is easily deposited on an Si surface in hydrofluoric acid ͑HF͒-based etching solutions. [4][5][6][7][8][9][10][11][12] Furthermore, Cu is now attracting much attention because of its possible application as a conduction material in the fabrication of the wiring structure on ultralarge-scale integrated circuits ͑ULSIs͒. 13,14 Ohmi et al investigated Cu deposition on an Si͑100͒ surface in various electrolyte solutions in detail.…”

“…Graf et al observed that an additional water rinse could significantly enhance the surface oxidation of the Si wafer after immersion in 5% HF solution containing copper in the parts per million range. 7 Parks et al showed that the amount of Cu deposited on an Si͑100͒ surface from HFbased etching solutions increased as the Cu concentration in the solution increased based on total reflection X-ray fluorescence measurements. [8][9][10] Kimerling et al demonstrated that the nucleation rate of Cu on a Si surface depended on the reduction rate of Cu 2ϩ while the growth rate of Cu nuclei was determined by the rate of the Si anodic dissolution.…”