Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
1999-12-23
2001-09-18
Nguyen, Nam (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S192150
Reexamination Certificate
active
06290822
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to dielectric films, and more particularly, to improved methods for forming such materials.
2. Description of the Related Art
Dielectric films and, more particularly, high dielectric constant (&egr;>10) films, such as tantalum pentoxide (Ta
2
O
5
), titanium oxide (TiO
2
), and barium strontium titanate ((Ba,Sr)TiO
3
or BST), play an important role in the manufacturing of integrated circuits. Such films have applicability, for example, in the manufacture of metal-oxide-semiconductor (MOS) transistors as well as in the manufacture of metal-oxide-metal (MOM) and metal-insulator-metal (MIM) capacitors and amorphous semiconductors.
High dielectric constant films are generally formed by either sputtering or chemical vapor deposition (CVD). For several reasons, the preferred method, however, is CVD. For example, high dielectric constant films deposited using CVD are far less dense and, therefore, can be annealed at lower temperatures than sputtered films. Further, sputtered high dielectric constant films are typically oxygen deficient (or metal-rich). This is especially true in the interfacial regions between the electrode and the dielectric, as in the case of MOM and MIM capacitors. The oxygen deficiency that is typical of a sputtered high dielectric constant film generates pathways for electrical conduction (referred to as “leakage”). This leakage (and hence the oxygen deficiency that causes it) is considered a flaw in the film. In an attempt to remedy this flaw, post deposition annealing of the film in an oxygen ambient is usually required to incorporate oxygen into the film and thereby reduce the leakage by eliminating (or substantially eliminating) the oxygen deficiency. However, because of the dense nature of sputtered films, they are difficult to anneal.
Despite the foregoing disadvantages of sputtering, sputtering does have some advantages over CVD for forming high dielectric constant films. For example, with sputtering, there is more flexibility in varying the composition of dopants in the resultant film. Further, it is easier to change materials to be deposited by sputtering. Still further, sputtering involves fewer dangerous chemicals than CVD.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a method for forming dielectric films, and in particular, high dielectric constant films that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
Additional features and advantages of the invention will be set forth in the description that follows and, in part, will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the method particularly pointed out in the written description and claims hereof as well as the appended drawing.
To achieve these and other advantages and in accordance with the purposes of the invention, as embodied and broadly described, the invention provides a method for forming a dielectric film having a desired composition comprising sputtering a dielectric material onto a substrate to produce an intermediary film, the intermediary film incorporating one or more elements in addition to those elements included in the desired composition of the dielectric film; and removing the one or more additional elements from the intermediary film to produce the dielectric film having the desired composition.
In one aspect of the invention, the dielectric film is a high dielectric constant film.
In another aspect of the invention, the additional one or more elements are introduced with an ambient gas during the sputtering of the dielectric material.
In yet another aspect of the invention, the sputtering of the dielectric material includes as least one of reactive sputtering, chemical sputtering, and RF sputtering of the dielectric material.
In still another aspect of the invention, the removing of the one or more additional elements from the intermediary film includes annealing the intermediary film in an oxidizing ambient comprising O
2
or NO
2
and/or performing a plasma treatment on the intermediary film.
In still yet another aspect of the invention, the dielectric material comprises Ta
2
O
5
, TiO
2
, or ZrO
2
.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 5319226 (1994-06-01), Sohn et al.
patent: 5814852 (1998-09-01), Sandhu et al.
patent: 5856704 (1999-01-01), Schuele
patent: 5944964 (1999-08-01), Solberg et al.
patent: 6149778 (2000-11-01), Jin et al.
patent: 61 035 548 (1986-02-01), None
J. P. Chang, M. L. Steigerwald, R. M. Fleming, R. L. Opila and G. B. Alers; “Thermal Stability of Ta205 in Metal-Oxide-Metal Capacitor Structures”; Appplied Physics Letters, vol. 74, No. 24; Jun. 14, 1999; pp. 3705-3707.
Fleming Robert McIenore
Steigerwald Michael Louis
Wong Yiu-Huen
Zahurak Susan M.
Agere Systems Guardian Corp.
Cantelmo Gregg
Nguyen Nam
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