Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2000-08-07
2002-11-26
Nguyen, Viet Q. (Department: 2818)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S931000
Reexamination Certificate
active
06486061
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the formation of dielectric layers during fabrication of integrated circuits on semiconductor wafers. More particularly, the present invention relates to a method for providing a dielectric film having a low dielectric constant that is particularly useful as a premetal or intermetal dielectric layer.
2. Description of the Related Art
One of the primary steps in the fabrication of modern semiconductor devices is the formation of a thin film on a semiconductor substrate by chemical reaction of gases. Such a deposition process is referred to as chemical vapor deposition or “CVD.” Conventional thermal CVD processes supply reactive gases to the substrate surface where heat-induced chemical reactions take place to produce a desired film. Plasma enhanced CVD techniques, on the other hand, promote excitation and/or dissociation of the reactant gases by the application of radio frequency (RF) or microwave energy. The high reactivity of the released species reduces the energy required for a chemical reaction to take place, and thus lowers the required temperature for such PECVD processes.
Semiconductor device geometries have dramatically decreased in size since such devices were first introduced several decades ago. Today's fabrication plants are routinely producing devices having 0.25 &mgr;m and even 0.18 &mgr;m feature sizes, and tomorrow's plants soon will be producing devices having even smaller geometries. In order to further reduce the size of devices on integrated circuits, it has become necessary to use conductive materials having low resistivity and insulators having a low dielectric constant. Low dielectric constant films are particularly desirable for premetal dielectric (PMD) layers and intermetal dielectric (IMD) layers to reduce the RC time delay of the interconnect metalization, to prevent cross-talk between the different levels of metalization, and to reduce device power consumption. Undoped silicon oxide films deposited using conventional CVD techniques may have a dielectric constant (k) as low as about 4.0 or 4.2. One approach to obtaining a lower dielectric constant is to incorporate fluorine in the silicon oxide film. Fluorine-doped silicon oxide films (also referred to as fluorine silicate glass or—“FSG” films) may have a dielectric constant as low as about 3.4 or 3.6. Despite this improvement, films having even lower dielectric constants are highly desirable for the manufacture of integrated circuits using geometries of0.18 &mgr;m and smaller. Numerous films have been developed in attempts to meet these needs including: a spin-on glass called HSQ (hydrogen silsesqui-oxane, HSiO
1.5
) and various carbon-based dielectric layers, such as parylene and amorphous fluorinated carbon. Other low-k films have been deposited by CVD using an organosilane precursor and oxygen to form a silicon-oxygen-carbon (Si—O—C) layer.
While the above types of dielectric films are useful for some applications, manufacturers are always seeking new and improved methods of depositing low-k materials for use as IMD and other types of dielectric layers. For example, after deposition at low temperature, a silicon carbon or Si—O—C film is often quite porous. Consequently, the film tends to absorb moisture. The absorbed moisture generally degrades the properties of the film. In the case of a low-k film, moisture tends to increase the dielectric constant of the film and is detrimental to film adhesion. The porosity is normally reduced during the previously described thermal cure. However, if the cure is performed ex-situ, the film is exposed for a time to moisture from the ambient atmosphere.
SUMMARY OF THE INVENTION
The method of the present invention provides a new and improved post-deposition treatment process. The method of the present invention deposits and densities and cures an insulating layer. The post-deposition densification treatment further enhances adhesion by reducing shrinkage of the deposited film. The post-deposition densification takes place in a reducing environment. In one embodiment, the deposited film is treated in a reducing environment of ammonia for approximately 1 to 5 minutes at a temperature of approximately 400° C. Curing can be done in either a vacuum or conventional furnace environment. The densification is particularly useful for enhancing the stability of a film that is to be cured ex-situ, i.e. after removing the substrate from vacuum.
The densification is beneficial for films deposited by a low-temperature CVD process. In one embodiment, the insulating layer is deposited from a process gas of ozone and an organosilane precursor having at least one silicon-carbon (Si—C) bond. During the deposition process, the substrate is heated to a temperature less than about 250 C. In some embodiments, the organosilane precursor has a formula of Si(CH3)xH4-x where x is either 3 or 4 making the organosilane precursor either trimethylsilane (TMS) or tetramethylsilane (T4MS). In other embodiments, the substrate over which the carbon-doped oxide layer is deposited is heated to a temperature of between about 100-200° C. and the deposition is carried out in a vacuum chamber at a pressure of between 1-760 Torr.
The method is particularly useful in the manufacture of sub-0.2 micron circuits as it can form a PMD or IMD film with a dielectric constant below 3.0. The film has good gap fill capabilities, high film stability and etches uniformly and controllably when subject to a chemical mechanical polishing (CMP) step. The method is particularly useful when, for throughput reasons, the substrate containing the deposited film is removed from vacuum for curing in a furnace.
These and other embodiments of the present invention, as well as its advantages and features, are described in more detail in conjunction with the text below and attached figures.
REFERENCES:
patent: 5314845 (1994-05-01), Lee et al.
patent: 5338362 (1994-08-01), Imahashi
patent: 5532191 (1996-07-01), Nakano et al.
patent: 5605867 (1997-02-01), Sato et al.
patent: 5610105 (1997-03-01), Vines et al.
patent: 5741740 (1998-04-01), Jang et al.
patent: 5820976 (1998-10-01), Kamo
patent: 5872065 (1999-02-01), Sivaramakrishnan
patent: 5989983 (1999-11-01), Goo et al.
patent: 6054379 (2000-04-01), Yau et al.
patent: 6114216 (2000-09-01), Yieh et al.
patent: 6255222 (2001-07-01), Xia et al.
patent: 199 04 311 (1999-08-01), None
patent: 0 421 203 (1991-04-01), None
patent: 0 721 019 (1996-07-01), None
patent: 0 774 533 (1997-05-01), None
patent: 0 884 401 (1998-12-01), None
patent: WO 99/19910 (1999-04-01), None
K.V. Guinn et al., “Chemical Vapor Deposition of SiO2 From Ozone-Organosilane Mixtures Near Atmospheric Pressure,”Material Research Society Symp. Proc.,vol. 282, pp. 575-580 (1993).
S. Nag et al., “Carbon Doped Silicon Oxide Films for Sub-0.25 &mgr;m Technology Interconnect Isolation,”Novellus Systems, Inc.,San Jose, CA, pp. 74-78 (date??).
A. Nara et al., “Low Dielectric Constant Insulator by Downstream Plasma CVD at Room Temperature Using Si(CH3)4/O2,”Extended Abstracts of the 1996 International Conference on Solid State Devices and Materials,Yokohama, pp. 815-817 (1996).
A. Nara et al., “Low Dielectric Constant Insulator Formed by Downstream Plasma CVD at Room Temperature Using TMS/O2,”Jpn. J. Appl. Phys.,vol. 36, Part 1, No. 3B, pp. 1477-1480 (Mar. 1997).
G.M. Renlund et al., “Silicon Oxycarbide Glasses: Part I. Preparation and Chemistry,”J. Material Research, vol. 6, No. 12, pp. 2716-2722 (Dec. 1991).
Y. Song et al., “Optical and Structural Properties of Low-Temperature PECVD ETMS SiOx Thin Films,”Thin Solid State Films 334, pp. 92-97 (1998).
Y. Uchida et al., “Chemical-Vapor Deposition of OH-free and Low-k Organic-Silica Films,”Jpn. J. Appl. Phys.,vol. 37, Part 1, No. 12A, pp. 6369-6373 (Dec. 1998).
H. Wong et al., “Chemistry of Silicon Oxide Annealed in Ammonia,”Applied Surface Science,pp. 49-54 (1993).
H. Sugimara et al., “Silicon Oxide Films of Controlled Refractive Indices Prepared by RF Plasma CVD,”Int.
Gaillard Frederic
Lim Tian H.
Xia Li-Qun
Yieh Ellie
Applied Materials Inc.
Nguyen Viet Q.
Nhu David
Townsend & Townsend & Crew
LandOfFree
Post-deposition treatment to enhance properties of Si-O-C... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Post-deposition treatment to enhance properties of Si-O-C..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Post-deposition treatment to enhance properties of Si-O-C... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2948768