AVS 50th International Symposium
    Electronic Materials and Devices Monday Sessions
       Session EM+SC-MoA

Paper EM+SC-MoA7
STM Observation of Subsurface Boron Dopants on the Si(001)-2x1 Clean Surface

Monday, November 3, 2003, 4:00 pm, Room 321/322

Session: Defects and Interfaces in Electronic Materials and Devices
Presenter: M. Nishizawa, National Institute of Advanced Industrial Science and Technology, Japan
Authors: M. Nishizawa, National Institute of Advanced Industrial Science and Technology, Japan
L. Bolotov, National Institute of Advanced Industrial Science and Technology, Japan
T. Kanayama, National Institute of Advanced Industrial Science and Technology, Japan
Correspondent: Click to Email
As the feature size of integrated circuits approaches nanometer dimensions, dopant distribution in device regions plays an increasingly larger role in determining device performance. This has motivated research in recent years to identify a suitable technique to profile dopant distribution with atomic scale resolution. Among the more promising technologies is Scanning Tunneling Microscopy (STM). While a number of studies have been made to measure individual dopants on cleaved compound-semiconductor surfaces and cleaved or hydrogen-terminated Si surfaces using STM, no studies have been made on the Si(001)-2x1 clean surface. From a surface science perspective, the Si(001)-2x1 is one of the most widely studied and documented surfaces. However, it has not received attention in dopant measurement studies, as it is believed that surface states in the band gap obscure observation of dopant features. In this report, we show that Boron-dopant features can be successfully observed on the Si(001)-2x1 surface using STM. On the Boron-doped Si(001)-2x1 surface (sheet resistance is 0.01 @ohm@ cm) we have observed a number of specific features which are a few nanometers in size and appear as round-shaped protrusions superimposed on the corrugation of surface reconstruction in the filled-state image. The appearance of these features is quite similar to the dopant images observed previously on the other surfaces. These features can be recognized starting at a sample bias voltage (V@sub s@) of -1.0 V and tunneling current (I@sub t@) of 0.2 nA, can be enhanced by increasing V@sub s@ to -0.4 V and I@sub t@ to 2.0 nA. Area density of these features changes with dopant concentration of the substrate. From these results, we conclude that the specific features observed here are related to the Boron dopant located in a subsurface layer. This study was supported by NEDO.