An accurate MOS measurement procedure for work function difference in the Al/SiO2/Si system

Journal
Solid state electronics  
Volume
29
Issue
5
Start Page
571
End Page
578
Citation
Solid State Electronics 29 (5): 571-578 (1986)
Publisher DOI
10.1016/0038-1101(86)90080-8
Scopus ID
2-s2.0-0022717298
Publisher
Elsevier
Determination of Al/Si work function difference φMS is achieved by means of capacitance measurements of differently manufactured MOS varactors (Al/SiO2/n-Si) with variable oxide thickness ("step varactor"). For the φMS evaluation the influences of interface (fQit) and oxide (ifQf) charges have been considered, and models of their charges and dipole behaviour are described. Midgap band bending has been chosen as best condition for the evaluation of ΦMSO as basic amount of work function difference with negligible interference of Qit. Plots of ΦMSvs ψS for numerous specimens indicate that, usually, dipole voltage ΔΦ is closely connected to ΦMS within the voltage drop across the MOS varactor according toΦMS = ΦMSO + qΔΦ. For the evaluation of dipole voltage ΔΦ models of charge density Qit within interface states are presented which assume dominating donor or acceptor states within the two halves of the band gap. Corrections of impurity homogeneity across the wafer and of impurity profile into the depth of the chips are considered. For the work function difference extrapolated to intrinsic density, ΦMSO = (-0.26 ± 0.05) eV holds. Additionally from midgap through inversion of n-Si, dipole voltage was observed (ΔΦ = 0.015 V) which was caused by interface states and oxide charge 3 nm apart from one another. © 1986.
DDC Class
621.3: Electrical Engineering, Electronic Engineering