Spatial resolution of less than 10 nm has been identified as a requirement for accurate and quantitative two-dimensional dopant profiling by the International Technology Roadmap for Semiconductors (ITRS). Since scanning capacitance microscopy (SCM) can potentially meet this goal, SCM is developing into an important technique for dopant profiling of sub-micrometer semiconductor structures.
How Scanning Capacitance Microscopy (SCM) Works
The SCM technique is based on the high frequency response of the metal-oxide-semiconductor (MOS) structure, formed between the SCM probe, sample oxide and semiconductor. The semiconductor dopant concentration under the probe is characterized by the change in capacitance, dC, induced by a bias voltage change, dV, applied between the probe and sample. Inverse modelling techniques can be used to extract dopant concentration information from the SCM measurements.
Using Scanning Capacitance Microscopy to Research Metal Oxide Semiconductor (MOS) Technology
In carrying out the experimental SCM work, we have found that fabrication of a reasonably good quality overlying oxide on the sample, is important for the success of SCM measurements in quantitative dopant concentration extraction. In the course of this work, we have shown that the SCM technique itself can be used as a local nanoprobe to determine the quality of the oxide layer in MOS technology, without the need to form the metal or gate metallization for the SCM measurements, as the conductive probe tip functions like the gate electrode of a MOS structure. Some aspects of the SCM research work are carried out in collaboration with Professor Y.T. Yeow from the University of Queensland, Australia. Besides SCM, we are also investigating other type of scanning probe techniques for the characterization of nanostructures, such as electrostatic force microscopy and conduction atomic force microscopy.