Halogen etching of Si via atomic-scale processes

• Published in: Progress in surface science Vol. 68; no. 4; pp. 189 - 230
• Main Authors: Aldao, C.M., Weaver, J.H.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 15-09-2001; Elsevier
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Etching; Exact sciences and technology; Halogens; Materials science; Physics; Scanning tunneling microscopy; Silicon; Solid surfaces and solid-solid interfaces; Surface cleaning, etching, patterning; Surface structure and topography; Surface structure, morphology, roughness and topography; Surface treatments; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Scanning tunneling microscopy; Etching; Silicon; Surface structure, morphology, roughness and topography; Halogens; Bromine; Reviews; Semiconductor materials; Adsorption; Chlorine; Surface defect; STM; Iodine; Surface structure
• ISSN: 0079-6816; 1878-4240
• DOI: 10.1016/S0079-6816(01)00047-8

Scanning tunneling microscopy (STM) studies of spontaneous halogen etching of Si(1
0
0)-2×1 and Si(1
1
1) in the range 700–1100 K are reviewed. Although the morphology depends on temperature, the steady-state removal of Si by chlorine, bromine and iodine is dominated by layer-by-layer etching that produces bounded surface roughness. For Si(1
0
0), the etch pits, step profiles, and Si regrowth structures on the exposed surfaces exhibit temperature-dependent characteristic patterns. Healing of this etched surface begins at ∼1000 K, and there is complete halogen desorption and restoration of the pre-etch morphology by ∼1100 K. Since reaction pathways involve atomic level interactions, it is possible to use the data obtained with STM to extract information about the atomic-scale processes involved during etching. Thermally activated reactions of adsorbed F show that dimer vacancies (DVs) are produced in the top layer but, more significantly, there is multilayer pitting that accounts for a surface roughening which is unique to F. For Si(1
1
1)-7×7 etching in the range 700⩽
T⩽900 K involves Si removal from adatom sites and conversion to a 1×1 periodicity that is stabilized by the halogen. In this temperature range, bilayer step flow etching dominates and regrowth structures derived from six-membered Si rings terminated by Br appear near the bilayer steps. Step flow continues at 1000 K but terrace pitting is also activated. This produces triangular bilayer pits bounded by
〈1
1
̄
0〉
edges. At 1100 K, etching produces disordered vacancy clusters in the adatom layer. The presence of small ordered domains amidst randomly distributed adatoms is attributed to facile local removal.