Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Of specified material other than unalloyed aluminum
Reexamination Certificate
1999-06-09
2002-02-12
Crane, Sara (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified material other than unalloyed aluminum
C257S761000, C257S762000, C257S767000
Reexamination Certificate
active
06346747
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a method for fabricating a thermally stable diamond-like carbon film and electronic device containing such film and more particularly, relates to a method for fabricating a thermally stable diamond-like carbon (DLC) film for use as an intralevel or interlevel dielectric in a ULSI back-end-of-the-line (BEOL) wiring structure and electronic structures formed by such method.
BACKGROUND OF THE INVENTION
Amorphous hydrogenated carbon (a-C:H), also known as diamond-like carbon for its superior hardness, has many useful properties such as chemical inertness, high wear resistance, high resistivity and low dielectric constant (k<3.6). For instance, in a paper “Diamond-Like Carbon Materials As Low-k Dielectrics” published in Proc. Advanced Metalization and Interconnect Systems for ULSI Applications (1996), by Materials Research Society, Pittsburgh, Pa. 1997, such desirable properties were discussed. DLC films can be fabricated by a variety of techniques including physical vapor deposition or sputtering, ion beam sputtering and DC or RF plasma assisted chemical vapor deposition with precursors of a variety of carbon-bearing source materials. U.S. Pat. No. 5,559,369, assigned to some of the common assignees of the present invention, further discloses diamond-like carbon for use in VLSI and ULSI interconnect systems.
The continuous shrinking in dimensions of electronic devices utilized in ULSI circuits in recent years has resulted in increasing the resistance of the back-end-of-the-line (BEOL) metalization as well as increasing of the intralayer and interlayer capacitances. This combined effect increases signal delays in ULSI electronic devices. In order to improve the switching performances of future ULSI circuits, low dielectric constant 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 are available, for instance, polytetrafluoroethylene (PTFE) with k value of 2.0. However, these dielectric materials are not stable at temperatures above 300
~
350° C. which renders them useless during integration of these dielectrics in ULSI chips which require thermal stability at temperatures of at least 400° C. DLC materials have been previously considered as a possible low-k dielectric, however, the films have either been found not stable at temperatures above 300° C., or have dielectric constants significantly higher than 3.6.
It is therefore an object of the present invention to provide a method for fabricating a thermally stable carbon-based low dielectric constant film that does not have the drawbacks or shortcomings of the conventional methods.
It is another object of the present invention to provide a method for fabricating a thermally stable carbon-based low dielectric constant film from a cyclic hydrocarbon precursor.
It is a further object of the present invention to provide a method for fabricating a thermally stable carbon-based low dielectric constant film in a parallel plate plasma enhanced chemical vapor deposition chamber.
It is another further object of the present invention to provide a method for fabricating a thermally stable diamond-like carbon film of low dielectric constant for use in electronic structures as an intralevel or interlevel dielectric in a back-end-of-the-line interconnect structure.
It is still another object of the present invention to provide a method for fabricating a thermally stable diamond-like carbon film of low dielectric constant capable of sustaining a process temperature of at least 350° C. for four hours.
It is yet another object of the present invention to provide a thermally stable diamond-like carbon film of low dielectric constant that has low internal stresses and a dielectric constant of not higher than 3.6.
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 back-end-of-the-line wiring structure in which at least two of the layers of insulating materials comprise diamond-like carbon film.
It is yet another further object of the present invention to provide an electronic structure which has layers of diamond-like carbon films as intralevel or interlevel dielectrics in a back-end-of-the-line wiring structure which further contains at least one dielectric cap layer as a RIE MASK polish stop or a diffusion barrier.
SUMMARY OF THE INVENTION
In accordance with the present invention, a method for fabricating a thermally stable carbon-based low dielectric constant film such as a hydrogenated amorphous carbon or diamond-like carbon film by reacting a precursor gas of cyclic hydrocarbon in a parallel plate chemical vapor deposition chamber is provided. The present invention further provides an electronic structure that has layers of insulating materials as intralevel or interlevel dielectrics used in a back-end-of-the-line wiring structure wherein the insulating material can be a hydrogenated amorphous carbon or a diamond-like carbon film.
In a preferred embodiment, a method for fabricating a thermally stable carbon-based low dielectric constant film can be carried out by the operating steps of first providing a parallel plate plasma enhanced chemical vapor deposition chamber, positioning an electronic structure in the chamber, flowing a precursor gas of a cyclic hydrocarbon into the chamber, depositing a carbon-based low dielectric constant film on the substrate, and heat treating the film at a temperature not less than 300° C. for a time period of at least 0.5 hour. The method may further consist 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 the substrate at a frequency between about 12 MHZ and about 15 MHZ. The heat treating step may further be conducted at a temperature not higher than 300° C. for a first time period and then at a temperature not lower than 380° C. for a second time period, the second time period is longer than the first time period. The second time period may be at least 10 folds of the first time period. The cyclic hydrocarbon utilized can be selected from either cyclohexane or benzene. The carbon-based low dielectric constant film can be of either a hydrogenated amorphous carbon or a diamond-like carbon.
The deposition step for the carbon-based low dielectric constant film may further include the steps of setting the substrate temperature at between about 25° C. and about 325° C., setting the RF power density at between about 0.05 W/cm
2
and about 1.0 W/cm
2
, setting the precursor flow rate at between about 5 sccm and about 200 sccm, setting the chamber pressure at between about 50 m Torr and about 500 m Torr, and setting a substrate DC bias between about −50 VDC and about −600 VDC. The deposition process can be conducted in a parallel plate type plasma enhanced chemical vapor deposition chamber. When the conductive area of the substrate chuck is changed by a factor X, the RF power applied to the substrate chuck is also changed by a factor of X.
In another preferred embodiment, a method for fabricating a thermally stable diamond-like carbon film can be carried out by the operating steps of first providing a parallel plate type chemical vapor deposition chamber that has plasma enhancement, then positioning a pre-processed wafer on a substrate chuck which has a conductive area of between about 300 cm
2
and about 700 cm
2
and maintaining a gap between the wafer and a top electrode between about 1 cm and about 10 cm, flowing a precursor gas of a cyclic hydrocarbon into the chamber, and depositing a diamond-like carbon film on the wafer. The process may further include the step of heat treating the film after the deposition step at a temperature of not less than 300° C. for at least 0.5 hour. The pro
Grill Alfred
Jahnes Christopher Vincent
Patel Vishnubhai Vitthalbhai
Crane Sara
Trapp Robert M.
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