Frequenzabhängige Kapazitäts-Spannungs-Messungen an Metall-Halbleiter-Randschichten
Frequency dependent admittance analysis on metal-semiconductor contacts
The evaluation of Schottky diode capacitances or reliable free carrier concentration profiles in doped semiconductors by admittance measurements needs a time and money consuming diode structuring process, since the rectifying and ohmic conctacts are produced separately. The formation of both contacts during the same process step reduces costs. However, the diodes exhibit a poor ohmic contact. Consequently, minority carrier influence, series resistance effects and deep level influence lead to frequency dependent admittances. In this work frequency dependent admittance analysis and a simple small-signal equivalent circuit model are used to evaluate space charge capacitances reflecting only the free carriers of the doped material. This method is useful for automatic routing control of semiconductors. The minority carrier, deep level and series resistance influence on the diode admittance is reviewed.