Increasing minority carrier lifetime in as-grown multicrystalline silicon by low temperature internal gettering

(2016) Increasing minority carrier lifetime in as-grown multicrystalline silicon by low temperature internal gettering. Copyright and reuse: The Warwick Research Archive Portal (WRAP) makes this work of researchers of the University of Warwick available open access under the following conditions. This article is made available under the Creative Commons Attribution 4.0 International license (CC BY 4.0) and may be reused according to the conditions of the license. For more details see: A note on versions: The version presented in WRAP is the published version, or, version of record, and may be cited as it appears here. Articles you may be interested in Evidence for the role of hydrogen in the stabilization of minority carrier lifetime in boron-doped Czochralski silicon Appl. On the low carrier lifetime edge zone in multicrystalline silicon ingots Dependence of phosphorus gettering and hydrogen passivation efficacy on grain boundary type in multicrystalline silicon Advanced modeling of the effective minority carrier lifetime of passivated crystalline silicon wafers We report a systematic study into the effects of long low temperature (500 C) annealing on the lifetime and interstitial iron distributions in as-grown multicrystalline silicon (mc-Si) from different ingot height positions. Samples are characterised in terms of dislocation density, and lifetime and interstitial iron concentration measurements are made at every stage using a temporary room temperature iodine-ethanol surface passivation scheme. Our measurement procedure allows these properties to be monitored during processing in a pseudo in situ way. Sufficient annealing at 300 C and 400 C increases lifetime in all cases studied, and annealing at 500 C was only found to improve relatively poor wafers from the top and bottom of the block. We demonstrate that lifetime in poor as-grown wafers can be improved substantially by a low cost process in the absence of any bulk passivation which might result from a dielectric surface film. Substantial improvements are found in bottom wafers, for which annealing at 400 C for 35 h increases lifetime from 5.5 ls to 38.7 ls. The lifetime of top wafers is improved from 12.1 ls to 23.8 ls under the same conditions. A correlation between interstitial iron concentration reduction and lifetime improvement is found in these cases. Surprisingly, although the interstitial iron concentration exceeds the expected solubility values, low temperature annealing seems to result in an initial increase in interstitial iron concentration, and any subsequent decay is a complex process driven not only by diffusion of interstitial …