Enhanced boron gettering effect of n-type solar grade Si wafers by in situ oxidation

Abstract

To investigate the gettering effect of n-type (phosphorous-doped) crystalline Czochralski-silicon (Cz-Si) wafers, we made boron emitters by diffusing boron into them and, subsequently, oxidized the boron-diffused n-type crystalline silicon wafers by in situ wet and dry oxidation. After oxidation, we measured the minority carrier lifetime by using microwave photoconductivity decay (μ-PCD), open-circuit voltage by quasi-steady-static photoconductance and the sheet resistance by a 4 point probe, respectively. We suggested the boron diffusion and in situ oxidation conditions to achieve longer lifetimes. We can obtain the equivalent lifetime to conventional oxidation through the quartz tube designed for boron doping and in-situ oxidation. The uniformity of sheet resistance under 3% was achieved at relatively low temperature and the lifetime of 21.6 μs was also obtained by boron gettering effect and passivation of oxide layer.