Design of Solar Cells p+/n Emitter by Spin-On Technique
A. El Amrani, A Boucheham, Y. Belkacem, R. Boufenik and M. Boudaa
Research Center in Semiconductor Technology for Energetic (CRTSE), 02 Bd. Frantz Fanon, Alger, BP No 140, Les 07 Merveilles, Algiers, Algeria
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In this paper spin-on dopant diffusion has been investigated as a technique for fabrication of p+/n monocrystalline silicon solar cell emitters. A homogeneous spreading onto the front wafer surface has been achieved by using 2 ml of boron-dopant solution and three-step spin-profile. Study of the wafers stacking arrangement has revealed that the highest doping level and the best emitter sheet resistance uniformity were obtained using the back-to-back wafers arrangement. The N2/O2 gas ratio variation during the diffusion process has shown that a higher percentage of nitrogen yields a slightly lower emitter sheet resistance. Study on temperature dependence of as-processed emitter resistivity revealed that 910°C results in targeted sheet resistance of around 48 Ω/sq. Using these preliminary experimental results, a batch of 6 silicon wafers was processed. After BSG and BRL chemical removal, the batch average sheet resistance of the emitter was 49.50 Ω/sq. The uniformity of a wafer and of the batch was below 7% and 13%, respectively. The ECV and SIMS depth profiling have shown the electrically active and the total boron surface concentration of 1.5× 1020 atoms/cm3 and 2.5× 1020 atoms/cm3, respectively. The junction depth was around 0.3 μm. Finally, by increasing the oxygen flow rate we reached an average sheet resistance of 51 Ω/sq. and a junction depth of 0.35 μm.

DOI: 10.12693/APhysPolA.132.717
PACS numbers: 81.15.KK, 88.40.JJ, 85.40.Ry