Quantitative Estimation of Aluminum-Induced Negative Charge Region Top Area of SiO₂ Based on Frequency-Dependent AC Surface Photovoltage

Abstract

Most aluminum (Al) in Al-contaminated and thermally oxidized n-type silicon (Si) dioxide (SiO 2 ) is clarified to be segregated at the very top area of SiO 2 , causing a negative charge, as has been suggested by the formation of an (AlOSi) À network and/or AlO 2 À based on AC surface photovoltage (SPV). For a strongly inverted state at an oxidation temperature of 800 C for 1 h, the thickness of the Al-induced negative charge region is quantitatively determined to be 2.4 nm on the basis of AC SPV after successive step etching and chemical analysis. As oxidation duration increased at 800 C for 3 h, the strongly inverted state changed into a weakly inverted state, where the thickness of the Al-rich region is reduced (0.8 nm), proving that more than half of the (AlOSi) À network collapse and/or Al diffuses inside SiO 2 during a longer oxidation duration.

Collapse of Cr(OH)3/n‐Si Schottky barrier and growth of atomic bridging–type surface photovoltages in Cr‐deposited n‐type Si(001) wafers

“…An AC SPV is the change in the surface potential of a semiconductor when it is illuminated by a PB. In the present experiment, the frequency-dependent AC SPV was measured with an instrument developed in-house [8] on the basis of the system reported by Shimizu and coworkers, [12,13] while illuminating the sample with light from a blue light-emitting diode (LED) in an on-off mode. [8] The wavelength peak of the LED was 470 nm.…”

“…[1][2][3][4][5][6][7][8] The AC SPV occurs when a Si semiconductor with a depletion or inversion layer is irradiated with a PB (a negative charge in n-type Si and/or a positive charge in p-type Si). Until now, two kinds of AC SPV have been reported, atomic bridging-type [8][9][10][11][12][13] and a Schottky barrier type. [14][15][16][17][18] The atomic bridging-type AC SPV has been postulated to be as follows: if a trivalent Al or Fe, Al 3+ or Fe 3+ replaces the tetravalent Si ion, Si 4+ , in the native oxide [8][9][10] or thermally grown oxide [12] by the mechanism of metal-induced negative oxide charge [11] in the form of a network of (AlOSi) À or (FeOSi) À , [8][9][10] demonstrated previously.…”

Schottky-Barrier-Induced AC Surface Photovoltages in Au-Precipitated n-Type Si(001) Surfaces

“…This new mechanism of the occurrence of AC SPV differs from that originally described for the metal-induced negative-oxide charge 15) such as (AlOSi) À networks and/or AlO 2 À in n-type Si. 8,16,17) Omori et al 9) speculated that Au exists as clusters both on the surface of the native oxide and/or at the SiO 2 /Si interface exposed to air on the basis of AC SPV characteristics. However, the direct observation on the top of native oxide for the Si surface dipped in hydrofluoric acid (HF) aqueous solution and Au-contaminated was not performed; in contrast, in the thermally oxidized Au-contaminated n-type Si(001) wafer surface, clusterlike Au granules were observed on the top of SiO 2 on the basis of atomic force microscopy (AFM) images.…”

Negative Oxide Charge in Thermally Oxidized Cr-Contaminated n-Type Silicon Wafers

“…At temperatures between 550 and 750 C, AC SPV decreased inversely proportionally to frequency, indicating that the surface was strongly inverted in n-type Si. Analogous to the formation of the (AlOSi) À and/or AlO 2 À networks in thermal oxide, [4][5][6] a (CrOSi) À and/or CrO 2 À networks may have been formed, resulting in the creation of a negative oxide charge. Immediately after the immersion of a sample wafer (with a hydrophobic surface) in Cr-contaminated solution, Cr(OH) 3 is reported to give rise to a Schottky barrier on an n-type Si surface.…”