Coating processes – Direct application of electrical – magnetic – wave – or... – Plasma
Reexamination Certificate
2001-09-27
2002-11-12
Nguyen, Ngoc-Yen (Department: 1754)
Coating processes
Direct application of electrical, magnetic, wave, or...
Plasma
C427S579000, C427S489000, C438S680000, C438S681000
Reexamination Certificate
active
06479110
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a multiphase material that has a low dielectric constant (or low k), a method for fabricating films of this material and electronic devices containing such films. More particularly, the present invention relates to a low dielectric constant, multiphase material for use as an intralevel or interlevel dielectric film, a cap material, or a hard mask/polish stop in a ULSI back-end-of-the-line (BEOL) wiring structure, electronic structures containing the films and a method for fabrication such films and structures.
BACKGROUND OF THE INVENTION
The continuous shrinking in dimensions of electronic devices utilized in ULSI circuits in recent years has resulted in increasing the resistance of the BEOL metallization as well as increasing the capacitance of the intralayer and interlayer. This combined effect increases signal delays in ULSI electronic devices. In order to improve the switching performance of future ULSI circuits, low dielectric constant (k) insulators and particularly those with k significantly lower than that of silicon oxide are needed to reduce the capacitances. Dielectric materials that have low k values have been commercially available, for instance, one of such materials is polytetrafluoroethylene (PTFE) with a k value of 2.0. However, these dielectric materials are not thermally stable when exposed to temperatures above 300~350° C. which renders them useless during integration of these dielectrics in ULSI chips which require a thermal stability of at least 400° C.
The low-k materials that have been considered for applications in ULSI devices include polymers containing Si, C, O, such as methylsiloxane, methylsesquioxanes, and other organic and inorganic polymers. For instance, materials described in a paper “Properties of new low dielectric constant spin-on silicon oxide based dielectrics” by N. Hacker et al., published in Mat. Res. Soc. Symp. Proc., vol. 476 (1997) p25 appear to satisfy the thermal stability requirement, even though some of these materials propagate cracks easily when reaching thicknesses needed for integration in the interconnect structure when films are prepared by a spin-on technique. Furthermore, the precursor materials are high cost and prohibitive for use in mass production. In contrast to this, most of the fabrication steps of VLSI and ULSI chips are carried out by plasma enhanced chemical or physical vapor deposition techniques. The ability to fabricate a low-k material by a PECVD technique using readily available processing equipment will thus simplify its integration in the manufacturing process, reduce manufacturing cost, and create less hazardous waste. A co-pending application (Ser. No. 09/107,567) assigned to the common assignee of the present invention, which is incorporated here by reference in its entirety, described a low dielectric constant material consisting of Si, C, O, and H atoms having a dielectric constant not more than 3.6 and which exhibits very low crack propagation velocities. Further reduction of the dielectric constant of such a material will further improve the performance of electronic devices incorporating such dielectric.
It is therefore an object of the present invention to provide a low dielectric constant material consisting of two or more phases and having a dielectric constant of not more than 3.2.
It is another object of the present invention to provide methods for fabricating the multiphase materials of this invention.
It is a further object of the present invention to provide a method for fabricating a multiphase material wherein the first phase is a hydrogenated oxidized silicon carbon film ( contains Si, C, O, and H and henceforth called SiCOH), and at least a second phase consisting essentially of C and H atoms.
It is a further object of the present invention to prepare a multiphase material that contains nanometer-sized voids.
It is another further object of the present invention to prepare a multiphase material that has a dielectric constant which is at least 10% lower than that of a single phase SiCOH dielectric material.
It is another further object of the present invention to provide a method for fabricating a low dielectric constant, thermally stable multiphase film from a precursor mixture which contains two or more different precursor molecules.
It is still another further object of the present invention to provide a method for fabricating a low dielectric constant material including two or more phases in a parallel plate plasma enhanced chemical vapor deposition chamber.
It is still another further object of the present invention to provide a method for fabricating a low dielectric constant material including two or more phases using a remote plasma chemical vapor deposition process.
It is yet another object of the present invention to provide a method for fabricating a multiphase material for use in electronic structures as an intralevel or interlevel dielectric in a BEOL interconnect structure.
It is yet another further object of the present invention to provide a multiphase material with a low internal stress and a dielectric constant of not higher than 3.2.
It is still another further object of the present invention to provide an electronic structure incorporating layers of insulating materials as intralevel or interlevel dielectrics in a BEOL wiring structure in which at least one of the layers of insulating materials is a multiphase material.
It is yet another further object of the present invention to provide an electronic structure which has layers of multiphase materials as intralevel or interlevel dielectrics in a BEOL wiring structure which contains at least one dielectric cap layer formed of different materials for use as a reactive ion etching mask, a polish stop or a diffusion barrier.
SUMMARY OF THE INVENTION
In accordance with the present invention, a novel dielectric material that has two or more phases wherein the first phase is formed of a SiCOH material is provided. The invention further provides a method for fabricating the multiphase material by reacting a first precursor gas containing atoms of Si, C, O, and H and at least a second precursor gas containing mainly atoms of C, H, and optionally F, N and O in a plasma enhanced chemical vapor deposition chamber. The present invention still further provides an electronic structure that has layers of insulating materials as intralevel or interlevel dielectrics used in a BEOL wiring structure wherein the insulating material may be a multiphase film.
In a preferred embodiment, a method for fabricating a dual phase film is described. In the dual phase film, the first phase is formed of hydrogenated oxidized silicon carbon and the second phase is formed of mainly C and H atoms. The method can be carried out by the operating steps of first providing a plasma enhanced chemical vapor deposition chamber, positioning an electronic structure in the chamber, flowing a first precursor gas containing atoms of Si, C, O, and H into the chamber, flowing a second precursor gas mixture containing atoms of C, H, and optionally F, N and O, into the chamber, and depositing a dual-phase film on the substrate. Optionally, the deposited film can be heat treated at a temperature of not less than 300° C. for a time period of at least 0.25 hour. The method may further include the step of providing a parallel plate reactor which has a conductive area of a substrate chuck between about 300 cm
2
and about 700 cm
2
, and a gap between the substrate and a top electrode between about 1 cm and about 10 cm. A RF power is applied to at least one of the electrodes. The substrate may be positioned on the powered electrode or on the grounded electrode.
The first precursor utilized may be selected from molecules containing at least some of Si, C, O, and H atoms. Oxidizing molecules such as O
2
or N
2
O can be added to the first precursor. Preferably the first precursor is selected from molecules with ring structures such as 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS or C
4
H
16
O
4
Si
4
), tetraet
Gates Stephen McConnell
Grill Alfred
Patel Vishnubhai Vitthalbhai
International Business Machines - Corporation
Nguyen Ngoc-Yen
Trepp Robert M.
Tung Randy W.
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