F 87. The stated purpose of the invention described by the 143 Specification is to modify CVD
films to reduce resistivity and improve stability. Application 09/128,143, Specification, p.
3, ll. 16-19.
F 88. In the section titled “Summary of the Invention,” the 143 Specification states that the
inventors have found that post treating films with an inert plasma while biasing the substrate
will improve film resistivity and stability:
We have found that a post treatment of films formed via chemical vapor
deposition by exposure of the deposited film to an inert plasma while biasing
the substrate, results in more stable films. In particular, titanium nitride films
formed by chemical vapor deposition from a metallo-organo titanium
compound are modified to improve the resistivity and stability of the films.
Application 09/128,143, Specification, p. 3, l. 20 - p. 4, l. 2 (emphasis added).
F 89. The 143 Specification says that subjecting a CVD TiN film to an inert plasma containing
“high energy ions, obtained by applying a DC bias voltage to the substrate” is “[i]n
accordance to the process of the present invention:”
In accordance with the process of the present invention, films of titanium
nitride are post treated with an inert plasma containing high energy ions,
obtained by applying a DC bias voltage to the substrate. Only a low power RF
level need be applied, i.e., sufficient power to form a plasma from a precursor
gas, and a voltage of about 100 to 1000 volts applied to the substrate. For
example, a voltage of about 400 volts while applying only 100 watts of RF
power to form a plasma is quite sufficient to produce high energy ions and to
passivate or densify a titanium nitride film so that it remains stable over time.
Application 09/128,143, Specification, p. 7, l. 20 - p. 8, l. 5 (emphasis added).
F 90. The written description further emphasizes the importance of applying a voltage bias during
the plasma treatment:
Thus, it was highly unexpected that when a bias voltage was applied to the
substrate in a plasma, the sheet resistivity markedly decreased, and, more
importantly, remained stable over time.
Application 09/128,143, Specification, p. 11, ll. 21-24.
F 91. The use of high energy ions is said not to adversely effect coverage, deposition rate or barrier
performance, but
does markedly reduce the absorption of oxygen by the film and stabilizes the
resistivity of the titanium nitride film.
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