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Distribution of potential barrier height local values at Al-SiO₂ and Si-SiO₂ interfaces of the metal-oxide-semiconductor (MOS) structures

100%

Piskorski K. , Przewlocki H. M.

tom Vol. 36, nr 5

1-5

Using the photoelectric measurement methods distributions have been determined of the gate-dielectric EBG(x,y) and semiconductor-dielectric EBS(x, y) barrier height values in square gate (1 x 1 mm²) AI-SiO₂Si(n⁺) structures. Measurements have been made on a series of 26 MOS capacitors with semitransparent gates (tAl= 35 nm), on one silicon wafer. Barrier heights were measured using the modified Powell-Berglund and the modified Fowler methods. Measurement methods were modified in such a way as to allow determination of EBG(x,y) and EBS(x,y) distributions, as described in the text. It has been found that the EBG(x,y) distribution has a characteristic dome-like shape which is identical with the independently determined shape of the effective contact potential difference φMS(x,y) distribution. The EBS(x,y) distribution is of a random character and differences between highest and lowest values of EBS for any of the measured capacitors are much smaller than the respective differences in EBG values. These results show that it is the gate-dielectric barrier height distribution EBG(x,y) which causes the dome-like shape of the FMS(x,y) distribution, observed for several years in our laboratory. This finding supports aur hypothesis that the characteristic FMS(x,y) distribution over the gate area of Al-SiO₂-Si structures resuIts from the mechanical stress distribution under the gate electrode.

Band diagram determination of MOS structures with different gate materials on 3C-SiC substrate

80%

Piskorski K. , Przewlocki H. M. , Esteve R. , Bakowski M.

tom Vol. 20, No. 1

67-74

MOS capacitors were fabricated on 3C-SiC n-type substrate (001) with a 10-µm N-type epitaxial layer. An SiO2 layer of the thickness tox ≈ 55 nm was deposited by PECVD. Circular Al, Ni, and Au gate contacts 0.7 mm in diameter were formed by ion beam sputtering and lift-off. Energy band diagrams of the MOS capacitors were determined using the photoelectric, electric, and optical measurement methods. Optical method (ellipsometry) was used to determine the gate and dielectric layer thicknesses and their optical indices: the refraction n and the extinction k coefficients. Electrical method of C = ƒ (VG) characteristic measurements allowed to determine the doping density ND and the flat band voltage VFB in the semiconductor. Most of the parameters which were necessary for the construction of the band diagrams and for determination of the basic physical properties of the structures (e.g. the effective contact potential difference ΦMS) were measured by several photoelectric methods and calculated using the measurement data. As a result, complete energy band diagrams have been determined for MOS capacitors with three different gate materials and they are demonstrated for two different gate voltages VG: for the flat-band in the semiconductor (VG = VFB) and for the flat-band in the dielectric (VG = VG0).