RESEARCH OF POSSIBILITIES FOR IMPROVING THE ENERGY AND MASS PARAMETERS OF SOLAR CELLS USING PLASMA-CHEMICAL ETCHING

Abstract

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.