Electrolyte for EC-V profiling of InP and GaAs based structures

摘要

Electrochemical C-V (EC-V) profiling is the most often used and convenient method for accurate majority carrier concentration depth profiling of semiconductors. None of the previously developed electrolytes recommended for EC-V profiling of InP and GaAs based structures works with all the materials encountered. In our experience, the most common problems encountered when using these electrolytes are: (i) a poor electrolyte/semiconductor Mott-Schottky barrier, (ii) preferential dissolution at the defect areas, (iii) high chemical etch rates, (iv) formation of insoluble products on the surface, (v) large parasitic capacitance components, (vi) a rough bottom of the etch crater, (vii) rounding at the crater rim and (viii) electrolyte seeping under the edge of the sealing rim. Although, according to us, FAP is the best electrolyte for accurate profiling of InP structures, it does not work well with other III-V compounds. To overcome this, recently, we have developed a new electrolyte, which we call UNIEL (UNIversal ELectrolyte). However, as with the FAP electrolyte, the presence of HF makes the UNIEL incompatible with the electrochemical cell of Polaron EC-V profilers manufactured by BIG-RAD. By slightly modifying the electrochemical cell configuration we are able to use both the FAP and UNIEL electrolytes, without destroying the calomel electrode. Recently, we have, nevertheless, experimented with variations of the UNIEL with no HF content for EC-V profiling of structures based on InP and GaAs. Presently available results are presented here.