Processes for depositing low dielectric constant materials

Details Processes for depositing low dielectric constant materials Processes for depositing low dielectric constant materials

2001-02-07

2004-05-11

Chen, Bret (Department: 1762)

Coating processes

Coating by vapor, gas, or smoke

Mixture of vapors or gases utilized

C427S255290, C427S255395

Reexamination Certificate

active

06733830

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to low dielectric constant (“low-k”) materials, and more particularly to chemical vapor deposition (CVD) processes for making low-k materials, and the use of low-k materials as dielectric layers in microelectronic devices.
2. Description of the Related Art
As the dimensions of microelectronic devices become smaller, the importance of the physical properties of the materials used in their manufacture becomes more important. This is particularly true of the dielectric materials that are used to insulate metal lines and vias from one another because of the contributions to parasitic capacitance that these materials make. Silicon dioxide has been employed within the industry as a dielectric material for the manufacture of devices for nearly three decades, but may become less suitable in the future because of its relatively high dielectric constant (k~4.1). Thus, there is a need in the art of microelectronic device manufacturing for a process to deposit low-k films.
Fluorinated silicon glass (FSG) has been identified as a possible replacement for silicon dioxide, see e.g., U.S. Pat. Nos. 5,563,105; 5,703,404; and 5,876,798. FSG films are known to have a dielectric constant in the range 3.3 to 3.6, depending on the fluorine concentration.
Carbon is also known to reduce the dielectric constant of oxide materials. Generally speaking, organic precursors are employed in plasma deposition or spin-on deposition processes. The preparation of low-k films by plasma-enhanced chemical vapor deposition (PECVD) has been disclosed, for example in G. Sugahara et al., “Low Dielectric Constant Carbon Containing SiO
2
Films Deposited By PECVD Technique Using a Novel CVD Precursor,” Feb. 10-11, 1997, DUMIC Conference, 97ISMIC-222D; T. Shirafuji et al., “Plasma Copolymerization of Tetrafluoroethylene/Hexamethyldisiloxane and In Situ Fourier Transform Infrared Spectroscopy of Its Gas Phase,” Jpn. J. Appl. Phys., 38, 4520-26 (1999); M. Loboda, “New solutions for intermetal dielectrics using trimethylsilane-based PECVD processes,” Microelectronic Engineering, 50, 15-23 (2000); T. Shirafuji et al., “PE-CVD of Fluorocarbon/SIO Composite Thin Films Using C4H8 and HMDSO,” Plasmas and Polymers, 4(1) 57-75 (1999); T. Shirafuji et al., “PE-CVD of Fluorocarbon/Silicon Oxide Composite Thin Films from TFE and HMDSO,” Mat. Res. Soc. Symp. Proc., 544, 173-178 (1999). Other references in this regard include Indrajit Banerjee, et. al., “Characterization of Chemical Vapor Deposited Amorphous Fluorocarbons for Low Dielectric Constant Interlayer Dielectrics.” J. Electrochem. Soc., Vol. 146(6), p. 2219, 1999; C. B. Labelle, et. al., DUMIC, pg. 1998, 1997; Sang-Soo Han, et. al., “Deposition of Fluorinated Amorphous Carbon Thin Films as a Low-Dielectric Constant Material.” J. Electrochem. Soc., Vol. 146(9), p. 3383, 1999; U.S. Pat. Nos. 6,068,884; 6,051,321; 5,989,998; and 5,900,290. All patents and literature references mentioned herein are incorporated by reference in their entireties.
Spin-on processes are also known for making low-k films. These processes generally involve dissolving or dispersing a low-k polymer in a solvent to form a liquid coating mixture, depositing the coating mixture onto a substrate, spinning the substrate to create a uniform coating, then drying the coating to remove the solvent. Another known method for reducing the dielectric constant of a film is to introduce porosity into the film.
There remains a need for low-k films having better properties more suitable for use in microelectronics manufacturing, and for processes for producing such films that can be readily integrated into fabrication process flows.
SUMMARY OF THE INVENTION
Available processes for the deposition of low-k films may be suitable in some semiconductor manufacturing processes, but there is a need in the art for CVD processes that do not require the use of a plasma. Thus far, that need has not been fulfilled by thermal CVD processes because films deposited using conventional chemical precursors do not have the desired low dielectric constant, or because thermal CVD of those precursors must be conducted at a temperature that is too high for the stage of the integrated circuit production. Accordingly, there is a need in the art for chemical precursors that can be used to produce low-k films by thermal CVD. Preferably, these chemicals precursors would be highly versatile, forming low-k films under a variety of CVD conditions, thus providing the manufacturer with a range of processing options for a given application.
The inventor has discovered a number of chemical precursors that are useful in CVD processes for the deposition of low-k films.
In one embodiment, a thermal chemical vapor deposition process for depositing a Si-containing material on a surface is provided. In this preferred process, a substrate is contained in a chemical vapor deposition chamber and a gas containing a chemical precursor is introduced to the chamber. The chemical precursor is preferably a compound containing at least one silicon atom and at least one carbon atom, or a compound containing at least one carbon atom and at least one oxygen atom. The chemical precursor is more preferably a siloxane, a (fluoroalkyl)fluorosiloxane, a (fluoroalkyl)silane, an (alkyl)fluorosilane, a (fluoroalkyl)fluorosilane, an alkylsiloxysilane, an alkoxysilane, an alkylalkoxysilane, a silylmethane, an alkoxysilylmethane, an alkylalkoxysilylmethane, an alkoxymethane, an alkylalkoxymethane, or a mixture of two or more of these chemical precursors with one another. The Si-containing film is preferably deposited onto the substrate by thermal CVD at a temperature of about 300° C. or higher, and preferably has a dielectric constant of about 3.5 or lower, as deposited. These Si-containing films are useful in the manufacture of integrated circuits, e.g., as interlevel dielectrics.
In another preferred embodiment, a CVD process is provided for depositing a low-k Si-containing material on a surface. In a preferred CVD process, a substrate is contained in a chemical vapor deposition chamber and a gas containing a chemical precursor is introduced to the chamber. The chemical precursor is preferably a silylmethane, an alkoxysilylmethane, an alkylalkoxysilylmethane, an alkoxymethane, an alkylalkoxymethane, or a mixture of two or more these chemical precursors with one another. The Si-containing film is preferably deposited onto the substrate by thermal CVD, and the film preferably has a dielectric constant of about 3.5 or lower, as deposited. These processes are useful for making Si-containing films with utility in the manufacture of integrated circuits, e.g., as interlevel dielectrics.
In another preferred embodiment, novel alkoxysilylmethanes and alkylalkoxysilylmethanes are provided, useful as chemical precursors for low-k films, as well as processes for making them.
Multi-layered low-k films and processes for making them are also disclosed herein.
In a preferred embodiment, a CVD process for depositing a Si-containing material on a surface is provided. In a preferred CVD process, a substrate is contained in a chemical vapor deposition chamber and a first gas containing a first chemical precursor is introduced to the chamber. A first Si-containing film is deposited onto the substrate. This first Si-containing film preferably has a dielectric constant of about 3.5 or lower, as deposited, and a thickness in the range of about 50 Å to about 5000 Å. A second gas containing a second chemical precursor, different from the first chemical precursor, is then introduced into the chamber, and a multi-layered film is created by depositing a second Si-containing film onto the first film. This second Si-containing film preferably has a dielectric constant of about 3.5 or lower, as deposited, and a thickness in the range of about 50 Å to about 5000 Å. The resulting multi-layered film preferably has a dielectric constant of about 3.5 or lower, as deposited. Preferably, the outer layers of the

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