Etching of silicon (111) with the scanning tunneling microscope

Abstract

It has recently been demonstrated that the scanning tunneling microscope can be used to break organometallic molecules on a scale of tens of nanometers [E. E. Ehrichs, S. Yoon, and A. L. Lozanne, Appl. Phys. Lett. 53, 2287 (1988)]. This process has been used to write dots, lines, crisscross patterns, and letters on silicon surfaces. Thus far, dimethyl cadmium, trimethyl aluminum, and tungsten hexafluoride have been used as precursor gases. Organic surface contaminants can also be polymerized by this process, yielding stable structures with linewidths down to 10 nm. All these fabricated structures are conductive enough to drain the tunneling current. More information is currently being obtained by measuring the resistance of lines written by this technique. More recently, it has been observed that WF6 can produce either deposits or etch pits in silicon. The smallest pit obtained thus far is 20 nm in diameter and 12 nm deep. The parameter that determines whether deposition or etching takes place is probably the surface temperature, although this remains to be tested. The results may be useful for archival memory storage, custom interconnects, and for the study of the physics of nanostructures.