Precipitation‐Induced Currents and Generation‐Recombination Currents in Intentionally Contaminated Silicon P+N Junctions

Abstract

The effects of impurities such as gold, iron, copper, nickel, tantalum, and tungsten on junction reverse I‐V characteristics were investigated using DLTS (deep level transient spectroscopy), TSCAP (thermally stimulated capacitance), I‐V , C‐V , and I‐T measurements. In almost all cases, the reverse I‐V characteristics consisted of two components; a normal Shockley‐Read‐Hall (SRH) generation component and a soft leakage component which dominates the SRH component above a given onset voltage. Only the SRH component can be detected with the DLTS and TSCAP methods. The soft leakage currents were ascribed to the presence of impurity precipitates lying near the metallurgical junction of the devices. Soft leakage currents measured at 80°K were fitted to a Fowler‐Nordheim field‐emission model. Localized electric field values near the precipitates of the order of 106–107 V/cm were obtained by this analysis. These values could be correlated with the possible shape of the precipitates. The distribution of the SRH generation centers within the active regions of the devices and the activation energies of the emission rates of above‐mentioned impurities were measured using the DLTS technique. The following results were obtained: Au 0.55 eV (c), Fe 0.57 eV (c); Cu 0.2 eV (c), 0.49 eV (v), 0.41 eV (v); Ni 0.19 eV (c), 0.36 eV (c); Ta 0.21 eV (c); and W 0.25 eV (c), 0.28 eV (c), respectively. Here c and vrepresent measurements from the conduction band and valence band, respectively.

Quantitative trace metal analysis of silicon surfaces by ToF-SIMS

“…The MstdRSFm(i) values were determined for each metal using the metal-speciÐc regression coefficients and the "standardÏ oxide ion ratios tabulated in Table 3. These MstdRSFm(i) values are then used to generate a series of M1MF values, corresponding to each sputter depth within the two craters, using Eqn (3). Values for the coefficients in Eqn (6) were determined and are tabulated in Table 2.…”

Challenges facing copper‐plated metallisation for silicon photovoltaics: Insights from integrated circuit technology development

“…Copper contamination in Si devices with a p‐n junction has been shown to lead to an increase in leakage current . Istratov et al suggested that the leakage current at p‐n junctions increases through the formation of Cu precipitates in the junction area, most likely starting from the n‐type side of the junction, where Cu complex formation is favoured .…”

Characterisation of electrically active defects

“…Furthermore oxygen content in the starting wafer in the 10 17 cm -3 range has been shown to increase leakage by Slotboom et al [19], while Busta and Waggener studied generation currents induced by metal impurity precipitation. In their analysis they obtained deep energy levels through deep level transient spectroscopy for gold, iron, copper, nickel, tantalum, and tungsten [20].…”