Two-dimensional profiling of shallow junctions in Si metal-oxide-semiconductor structures using scanning tunneling spectroscopy and transmission electron microscopy

Abstract

We have used cross-sectional scanning tunneling spectroscopy and cross-sectional transmission electron microscopy to perform two-dimensional profiling of shallow pn junctions in Si metal-oxide-semiconductor structures. In the tunneling spectroscopy measurements, clear differences were observed between current-voltage spectra obtained from p-type, n-type, and depleted regions of the metal-oxide-semiconductor structures; current images generated from the tunneling spectra revealed the profiles of the pn junctions with spatial resolution in both the lateral and vertical directions on the order of 10 nm. Calculated tunneling current-voltage spectra were found to be consistent with observed differences in experimental spectra obtained from p-type and n-type regions of the junctions. Junction profiles obtained by scanning tunneling spectroscopy have also been compared to transmission electron microscopy images of chemically delineated junctions and measurements of vertical dopant profiles obtained by secondary ion mass spectrometry.

Imaging the depletion zone in a Si lateral pn junction with scanning tunneling microscopy

“…There have been a number of investigations of Si pn junctions with the STM, but direct imaging of the depletion region has been less than successful. [1][2][3][4][5][6][7] This is mainly due to Fermi-level pinning, caused by the large density of surface states in the band gap of Si͑001͒ and Si͑111͒, which dominates the tunneling characteristics and inhibits junction delineation. On the other hand, STM and scanning tunneling spectroscopy ͑STS͒ measurements of H-terminated 1,4,7-9 and oxide-covered 3,5,10 Si surfaces and pn junctions have demonstrated the ability of these layers to passivate the surface states so that the Fermi level is unpinned.…”

A reverse bias, tip-insulator-semiconductor tunnel diode model accounting for the delineation of a p/p+ junction using scanning tunneling microscopy

“…It is worth noting that an interesting result has been reported by Yu et al 12 who delineated a n ϩ /p junction using CITS mode. In their case, if the tip-sample distance was established at 1.5 V with 1 nA current, under the same large negative bias condition, the tip current in the depletion region in the n ϩ /p junction would be much larger than that both in the p and n ϩ region.…”

Atomic scale images of acceptors in III-V semiconductors

“…The first two parts are treated in the textbooks [71,131], therefore only a summary will be given here. The spin-orbit Hamiltonians will be discussed in more detail.…”

“…This method provides an easy possibility to include strain fields and electric fields. The formalism for standard band structure calculations is given in different textbooks [71,131]. Here, the calculation is extended to account for the spin-orbit interaction of the electrons with the crystal potential.…”