National University of Science and Technology «MISIS»:

P. B. Lagov

A. S. Drenin

E. S. Rogovskii

A. M. Lednev

Possible process options for thinning semiconductor substrates have been analyzed. Experiments have been conducted to assess the efficiency of plasma−chemical etching of (100) orientation single crystal germanium substrates used for growing heteroepitaxial structures of multi−cascade solar cells based on A³B⁵ semiconductor compounds. The specimens were etched on a reactive ion etching instrument with an induction type high−density plasma source in (SF₆ : Ar = 2 : 1) gas mixture through various photoresist masks. For FP−383 photoresist masks with 2, 4 and 6.5 μm windows, the etched layer was 20 μm in depth. For a FN−11 photoresist mask with a 95 μm window, etching reached a depth of 58 μm. The FP−383 masks exhibited thinning from 1.5 to 0.87 μm, and the FN−11 mask thinned from 10 to 8 μm. We show that the etching rate which was 2.1−3.3 μm/min decreases with an increase in mask window width following a power law. We have concluded that plasma−chemical etching is a promising tool for improving the energy and mass parameters of multi−cascade solar cells with conventional and metamorphic structures at the final stage of their fabrication.

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