Metal Impurities near the SiO2 ‐ Si Interface

Abstract

The behavior of metal impurities (Cu, Fe, Cr, and Ni) near the SiO2‐normalSi interface during dry O2 and O2/normalHCl oxidation was studied by means of defect etching and secondary ion mass spectroscopy methods using intentionally metal‐contaminated silicon wafers. Redistribution of metal impurities resulting from a thermal oxidation is different for each metal. Copper diffused into the silicon, showing concentration peaks 0.3–1.2 μm from the interface, and tended to be rejected by the silicon dioxide. Iron accumulated at the interface, while chromium tended to accumulate in the oxide having a lower concentration in silicon. Gettering ability using O2/normalHCl oxidations was excellent for copper, but poor for iron and chromium impurities. Copper and iron impurities precipitate in the silicon near the interface, but chromium and nickel impurities do not.

Chromium distribution in multicrystalline silicon: comparison of simulations and experiments

“…Unfortunately, the low lifetime of the wafer from the top impedes a measurement of a chromium concentration below 6 × 10 11 cm −3 . Because of the oxide in the capping layer, we cannot exclude a reaction between oxygen and chromium at the interface , which could lead to a small external gettering effect during annealing. Without growing precipitates beforehand, a high supersaturation, i.e., a total concentration above 1 × 10 14 cm −3 , is necessary to reduce the fraction of dissolved chromium efficiently.…”

Diffusion of Sr, Bi, and Ta in amorphous SiO2

“…Diffusion coefficients of dopants such as B, Al, P, As, and Sb have been established because of their technological importance [14]. Diffusion studies in SiO 2 are also available for Fe [15][16][17], Cu [15,18], Ag [18,19], Au [18,20], Ti [18,21], Pd [18], Co [21], Ni [22], and Cr [15].…”

Impurity Precipitation, Dissolution, Gettering and Passivation in PV Silicon: Final Technical Report, 30 January 1998--29 August 2001

“…These iron-silicide precipitates were observed at Si/SiO 2 interfaces. However, most observations of iron-silicide precipitates were done after implantation of high doses of iron with subsequent annealing [119][120][121][122][123][124][125][126][127][128][129]. These studies were stimulated by the prospect of using iron-silicide or silicon-based optoelectronics (see, e.g., [130][131][132]) since its direct band gap of about 0.87 eV makes it suitable for the fabrication of infrared detectors or emitters integrated to silicon circuits.…”

“…Besides precipitation of iron at extended defects in the bulk, accumulation of iron at the Si/SiO 2 interfaces or at the bare silicon surface has also been observed [113,127,[158][159][160][161][162][163][164]. The precipitation of iron near the growing Si/SiO 2 interface may be stimulated by silicon self-interstitials, injected by the growing oxide and consumed by the iron-silicide precipitates, or by local compressive strain fields at the Si/SiO 2 interface [161,162].…”