Selectivity loss during tungsten chemical vapor deposition: The role of tungsten pentafluoride

Journal Article · Mon May 01 04:00:00 EDT 1989 · J. Vac. Sci. Technol., A; (United States)

DOI:https://doi.org/10.1116/1.575854· OSTI ID:6335183

Creighton, J R

Our previous studies found evidence for a selectivity loss mechanism that is initiated by desorption of tungsten subfluorides formed by the reaction of WF/sub 6/ with metallic tungsten surfaces. When a hot (approx. =600 /sup 0/C) tungsten surface is exposed to WF/sub 6/, a nonvolatile subfluoride, apparently WF/sub 4/ , will accumulate on a nearby SiO/sub 2/ surface held at approx. =30 /sup 0/C. Disproportionation of this tungsten subfluoride upon heating above 350 /sup 0/C produces a reactive state of tungsten that induces rapid selectivity loss when exposed to chemical vapor deposition conditions. The net effect of this tungsten subfluoride desorption--disproportionation mechanism is the transport of tungsten from a tungsten surface to the silicon dioxide surface. Isolation of a higher tungsten subfluoride, apparently WF/sub 5/, has been accomplished by cooling the SiO/sub 2/ surface to approx. =-45 /sup 0/C under otherwise similar experimental conditions. Preliminary Auger spectroscopic results yield a stochiometry of F/W = 4.9 +- 0.5 for this subfluoride, and temperature programmed desorption results are consistent with the behavior of tungsten pentafluoride. Upon heating WF/sub 5/ multilayers, most of the compound desorbs, but some reaction and disproportionation occurs leaving a reduced state of tungsten on the SiO/sub 2/ surface. It seems likely that tungsten pentafluoride is the key volatile species in a tungsten transport mechanism that can initiate selectivity loss.

• Research Organization: Sandia National Laboratories, Albuquerque, New Mexico 87185
• OSTI ID: 6335183
• Journal Information: J. Vac. Sci. Technol., A; (United States), Journal Name: J. Vac. Sci. Technol., A; (United States) Vol. 7:3; ISSN JVTAD
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
CHEMICAL COATING
CHEMICAL REACTION KINETICS
CHEMICAL VAPOR DEPOSITION
COATINGS
DEPOSITION
ELEMENTS
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
KINETICS
METALS
REACTION KINETICS
REFRACTORY METAL COMPOUNDS
SEMIMETALS
SILICON
SUBSTRATES
SURFACE COATING
SURFACE PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
TUNGSTEN
TUNGSTEN COMPOUNDS
TUNGSTEN FLUORIDES