Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1996-06-10
2001-03-13
Quach, T. N. (Department: 2814)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S631000, C438S787000, C438S927000
Reexamination Certificate
active
06200894
ABSTRACT:
BACKGROUND OP THE INVENTION
1.Field of the Invention
The present invention generally relates to the manufacture of microelectronic systems and, more particularly, to enhancement of the interconnect properties of aluminum and aluminum alloy electrical conductors in fine line width conductor patterns with improved resistance to electromigration.
2.Background Description
Aluminum-based interconnects are commonly used in the industry due to their low resistivity and ease of fabrication. However, such interconnects are less reliable than either tungsten or copper-based interconnects since they are subject to electromigration, where electrical current induces damage in paths such as grain boundaries. Many different types of grain boundaries can form between aluminum grains, depending on their orientations, and different types of grain boundaries have been shown to produce enhanced or degraded reliability. See for example H. P. Longworth and C. V. Thompson,
MRS Symp. Proc.,
Vol. 265, 1992, pp. 95-100.
The “texture” of an aluminum film, as determined using X-ray diffraction, describes the distribution of grain orientations in a film, and hence indicates whether fewer or more types of grain boundaries exist in a film. More types of grain boundaries increase the likelihood that “weak” boundaries will be incorporated in an interconnect after patterning. Hence, the degree of texture in a film is an indication of how well the film will resist electromigration damage. See D. B. Knorr and K. P. Rodbell,
SPIE Vol.
1805 Submicrometer Metalization 1992, pp. 120-221.
Effects of insulator surface roughness on Al-alloy film crystallographic orientation in Al-alloy/Ti insulator structures have been discussed by H. Onoda et al., Jpn. J. Appl. Phys., vol. 34 (1995), pp. 1037-1040.
SUMMRY OF THE INVENTION
It is therefore an object of the present invention to provide enhanced aluminum interconnect properties in very fine metalization patterns interconnecting integrated circuits.
According to the invention, a method is provided for enhancing the texture and electromigration resistance of aluminum thin films in layered interconnects by appropriate control of the surface roughness of the underlying insulator layer, typically an oxide layer. Specifically, enhanced performance is obtained in aluminum interconnects of the present invention by endowing an underlying insulator layer with reduced surface roughness. This can be accomplished by various techniques within the scope of this invention, such as by choice of insulator film material and film formation mode per se and/or by surface conditioning, e.g., planarization, of a previously deposited insulator film in an appropriate manner to impart the requisite surface smoothness, followed by aluminum or aluminum alloy layered structure formation and refining the aluminum microstructure formed thereon by hot deposition or ex-situ heat treatment.
In the present invention, the planarity of the insulator underlying the aluminum film, in terms of mean surface roughness, R
ms
as measured by atomic force microscopy (AFM), generally is below the 10 nm level, preferably below the 5 nm level, to impart a qualitative improvement in the texture and electromigration resistance to the aluminum or aluminum alloy thin films subsequently formed thereon.
In the present invention, the aluminum thin films can be pure aluminum, or alloys of aluminum, such as aluminum alloyed with a transition or refractory metal to enhance the reliability of the interconnect. Aluminum alloys can be prepared by planar dc-magnetron sputtering and anealing methods. Exemplary aluminum alloys include Al
3
Ti, Al—Ti, Al—Ti—Si, Al—Cu, Al—Si, Al—Si—Cu, Ti/Al—Cu, and the like. The insulator layer can be an oxide type. The oxide layer can be formed by techniques including oxidation of silane to form silane oxide such as by using either oxygen or nitrous oxide oxidants in APCVD or LPCVD systems operated at about 450° C.; formation of sub-atmospheric undoped silicon glass (SAUSG); pyrolytic oxidation of an alkoxysilane in CVD such as by oxidation of tetraethylorthosilane (TEOS) in a PECVD system at temperatures as low as about 300° C.; forming high density plasma (HDP) deposited oxide; and thermally growing oxides, e.g., growing thermal oxides of silicon as formed by maintaining a silicon surface in an elevated temperature in an oxidizing environment (e.g., dry oxygen or water vapor).
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Lee, J., et al., “Room Temperature Deposition of Silicon Dioxide Films . . . ”, J. Electrochem. Soc., vol. 143, No. 4, Apr. 1996, pp. 1443-1451.
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C.V. Thompson (editor), et al, Materials Reliability in Microelectronics II, Symposium Apr. 27, 1992-May 1, 1992, Materials Research Society, 1992, pp. 94-101, “Electromigration in Bicrystal Al Lines”.
Licata Thomas J.
Okumura Katsuya
Rodbell Kenneth P.
International Business Machines - Corporation
Neff, Esq. Daryl K.
Quach T. N.
Whitham, Curtis & Whitham
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