Effects of Lamp Pulses on the Oxygen - Precipitation - Gettering of Cr in Czochralski Grown Si

Abstract

Experiments on the intrinsic gettering of Cr in p-type Czochralski-grown Si including lamp pulse annealings have been carried out. Transmission Electron Microscopy observations of both oxide and metallic precipitates on cross-sectional specimens, as well as quantitative results about the electrically active metal depth-profiles, using Deep Level Transient Spectroscopy measurements, are presented. We have observed that a lamp pulse (1200 °C/5 s) applied prior to a three-step gettering cycle produced a strong retardation of the oxygen precipitation, and consequently an inhibition of the Cr bulk precipitation during the nucleation step. Besides, it was observed that the Cr-precipitates formed in the bulk during the oxygen nucleation step were highly unstable upon a post-gettering 2–4 s lamp pulse at 1000 °C, whereas the same lamp pulse did not produce a significant re-dissolution of Cr-precipitates formed during the oxide precipitate growth step. The reversibility of the intrinsic gettering of Cr upon a post-gettering lamp pulse thus critically depends on the oxide precipitate growth rate during the gettering process.

A Deep Level Transient Spectroscopy Study of the Internal Gettering of Cr in Czochralski‐Grown Silicon: Efficiency and Reversibility upon Lamp Pulse Annealings

“…Furthermore, the amount of re-dissolved Cr upon a short duration RTA should depend on the size of the Cr precipitates formed after internal gettering, which is determined by the second critical mechanism, i.e., the growth rate of metallic precipitates during the gettering process] We have observed by cross-sectional transmission electron microscopy (XTEM) that the formation of large CrSi2 precipitates after gettering is closely correlated to the formation of large SiQ amorphous precipitates. 16 This confirms the conclusions of Gilles et al concerning the precipitation of Fe, i.e., that the oxygen precipitates constitute the actual gettering sites and that the metal precipitation kinetics are mostly triggered by the oxygen precipitate growth rate]…”

“…In addition, in the CDBG sample, a high density of oxygen precipitates (about 5 • 1011 cm -3) into both the platelet and polyhedral forms was observed, whereas the CDBG sample initially submitted to a RTA at 1200~ for 5 s exhibited only oxygen precipitates into the platelet form with a slightly lower density (about 3 • i0 II cm-3). 16 In the introduction, we have mentioned that anomalous O~ loss kinetics, upon a two-step annealing sequence preceded by a lamp pulse annealing, have already been observed, n Although this strange behavior is not yet clearly explained, it may be held responsible for the failure of internal gettering, particularly when the metal is introduced by diffusion in a lamp furnace before applying the gettering cycle.…”

On the Origin of Internal Gettering Suppression in Low Carbon CZ Silicon by Rapid Thermal Annealing

“…2~ The density of the O precipitates was studied with the help of an etching by the Secco solution after a complete gettering process preceded by an RTA. 39 The density was higher in this case in comparison with a classical gettering treatment, and the gettering was inefficient. The authors interpreted these effects as a retardation of the O nucleation.…”

Influence of rapid thermal annealing and internal gettering on Czochralski-grown silicon. I. Oxygen precipitation

“…Then, a thermal treatment at 980°C for 30 min under Ar/H 2 ͑10%͒ is applied, so as to simulate the metal diffusion annealing used in a previous study on the efficiency of the IG of chromium. 17 Then the samples are submitted to the three-step IG process: ͑i͒ a treatment at 1100°C for 8 h under O 2 , to form the O denuded zone; ͑ii͒ the nucleation step at 750°C for 24 h; and ͑iii͒ the growth treatment at 950°C for 10 h. These last two thermal treatments are applied under nitrogen.…”