Determination of Si-metal work function differences by MOS capacitance technique

TLDR: Very accurate and reliable values of the difference between silicon electron affinity, χSi, and the metal work function, ΦM, have been obtained for seven different metals by the MOS flat-band capacitance technique as discussed by the authors.

Abstract: Very accurate and reliable values of the difference between silicon electron affinity, χSi, and the metal work function, ΦM, have been obtained for seven different metals by the MOS flat-band capacitance technique. Different MOS structures with the same interface charge density and the same metal but varying oxide thickness were manufactured on the same wafer by employing a small temperature gradient during steam oxidation in an r.f. induction heated vertical furnace. The flat-band voltage, VFB, vs oxide thickness, tox, graphs obtained are very good straight lines. Use of both p- and n-Si in case of the metals Au and Cr produced two values of the silicon bandgap EG. The value of EG obtained in case of Au differed from the established value of 1·11 eV at room temperature by −0·04 eV only, and by 0·07 eV in case of Cr. This gives an indication of the experimental accuracy of the ΦHS = ΦM − χSi values. Φ MS ∗ obtained by this technique is 0·73 eV for Ag. −0·11 eV for Al, 0·82 eV for Au, −0·06 eV for Cr, 0·63 eV for Cu, −1·05 eV for Mg, and −0·82 eV for Sn. The total inaccuracy is limited to −0.06 +0.03 eV .