Two-dimensional surface dopant profiling in silicon using scanning Kelvin probe microscopy

Abstract

We h a ve applied a simultaneous combination of scanning Kelvin probe microscopy and scanning atomic force microscopy to the problem of pro ling dopant concentrations in two dimensions in silicon microstructures. By measuring the electrochemical potential di erence which minimizes the electrostatic force between probe tip and sample surface, we estimate the work function di erence between the tip and surface. To the extent that this work function di erence is a consequence of the dopant concentration at, or near, the sample surface, we infer doping pro les from our measurement. Structures examined and presented here include contact holes, and the technologically signi cant lightly-doped drain of a metal-oxide-silicon eld-e ect transistor. Using this methodology, w e are able to distinguish relative c hanges in dopant concentration with lateral resolution less than 100 nm. Sample preparation is minimal, and measurement time is fast compared to other techniques. Our measurements have been compared to predictions based on two-and three-dimensional process and device simulation tools. The comparisons show our technique is sensitive t o c hanges in dopant concentration, from 10 15 cm ,3 to 10 20 cm ,3 , of less than ten percent at these size scales. Suggestions to resolve absolute dopant concentration are made.

Surface photovoltage phenomena: theory, experiment, and applications

“…The spatial resolution limit of the KFM is typically several tens of nm [259,265,266]. This value is about two to ®ve orders of magnitude better than that of most scanning Kelvin probes and one order of magnitude better than the record-resolution Kelvin probe mentioned in Section 3.1 [208].…”

“…Having discussed KFM principles and applications, we now describe several phenomena which are potential sources of artifacts in KFM readings and must be taken into account when interpreting experimental data: Just as the Kelvin probe, the KFM is also susceptible to systematic errors in CPD reading due to stray capacitance [263,266,268,271], as described in detail in Section 3.1. In the ideal treatment presented above, we have assumed that all capacitance is due to the tip apex only.…”

Carbon nanotubes as a tip calibration standard for electrostatic scanning probe microscopies

“…The offset y 0 provides a direct measure of the non-local contribution to the SPM signal due to the cantilever and conical part of the tip. [5,19,20,21] The profile shape is tip dependent and profiles for tip 1 and 2 are compared in Fig. 4d.…”

Sensitive imaging of electromagnetic fields with paramagnetic polar molecules

“…A tremendous progress in measuring magnetic fields has been recently achieved leading to the development of Hall effect sensors [5], SQUID sensors [6], force sensors [7], sensors based on microelectromechanical systems [8], and NV centers in diamond [9], as well as atomic magnetometers [10,11], making it possible to achieve the magnetic field sensitivity of 0.1 fT Hz −1/2 and to detect the magnetic field of a single electron, with steps being taken towards the detection of the magnetic field of a single nuclear spin [12,13]. At the same time, the development of scanning capacitance microscopy [14], scanning Kelvin probe [15], and electric field-sensitive atomic force microscopy [16] advanced the techniques for measuring electric fields to the level of probing individual charges. An unprecedented accuracy of 10 −6 electron charge was achieved with the use of single-electron transistors [17].…”