Semiconductor device manufacturing: process – Coating of substrate containing semiconductor region or of... – Insulative material deposited upon semiconductive substrate
Reexamination Certificate
2003-01-10
2004-08-03
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Coating of substrate containing semiconductor region or of...
Insulative material deposited upon semiconductive substrate
Reexamination Certificate
active
06770573
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention generally relates to a method for fabricating a dielectric material that has an ultralow dielectric constant (or ultralow-k) associated therewith. More particularly, the present invention relates to an improved method for fabricating a thermally stable ultralow-k film for use as an intralevel or interlevel dielectric in an ultra-large-scale integration (“ULSI”) back-end-of-the-line (“BEOL”) wiring structure.
2. Description of the Prior Art
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 dielectric. 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 silicon oxide are needed to reduce the capacitances. Dielectric materials (i.e., dielectrics) that have low-k values have been commercially available. For instance, one such material is polytetrafluoroethylene (“PTFE”), which has a k value of 2.0. However, these dielectric materials are not thermally stable when exposed to temperatures above 300~350° C. Integration of these dielectrics in ULSI chips requires a thermal stability of at least 400° C. Consequently, these dielectrics are rendered useless during integration.
The low-k materials that have been considered for applications in ULSI devices include polymers containing Si, C, O, such as methylsiloxane, methylsilsesquioxanes, and other organic and inorganic polymers. For instance, a paper (N. Hacker et al. “Properties of new low dielectric constant spin-on silicon oxide based dielectrics.”
Mat. Res. Soc. Symp. Proc
. 476 (1997): 25) described materials that 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 very-large-scale-integration (“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 plasma enhanced chemical vapor deposition (“PECVD”) technique using readily available processing equipment will simplify the material's integration in the manufacturing process, reduce manufacturing cost, and create less hazardous waste. A co-pending application (Hydrogenated Oxidized Silicon Carbon Material, U.S. Ser. No. 09/107,567, filed on Jun. 19, 1998, now U.S. Pat. Nos. 6,147,009 and 6,497,963) assigned to the common assignee of the present invention and incorporated herein by reference in its entirety, described an ultralow dielectric constant material, consisting of Si, C, O and H atoms, having a dielectric constant not more than 3.6, and exhibiting very low crack propagation velocities.
Another co-pending application (Multiphase Low Dielectric Constant Material and Method of Deposition, U.S. Ser. No. 09/320,495, filed on May 16, 1999, now U.S. Pat. Nos. 6,312,793, 6,479,110, and 6,312,793) assigned to the common assignee of the present invention and incorporated herein by reference in its entirety, described a dual-phase material, consisting of a matrix composed of Si, C, O, and H atoms, a phase composed of mainly C and H atoms, and having a dielectric constant of not more than 3.2. It should be noted that continued reduction of the dielectric constant of such materials will further improve the performance of electronic devices incorporating such dielectrics.
In view of the foregoing, there is a continued need for developing a dielectric material that has a dielectric constant of not more than about 2.8 and inhibits cracking.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved method for fabricating an ultralow dielectric constant material having a dielectric constant of not more than about 2.8. More preferably, the dielectric constant for the ultralow-k material is in a range of about 1.5 to about 2.5, and most preferably, the dielectric constant is in a range of about 2.0 to about 2.25. It should be noted that all dielectric constants are relative to a vacuum unless otherwise specified.
It is another object of the present invention to provide an improved method for fabricating an ultralow dielectric constant material comprising Si, C, O and H atoms from a mixture of at least two precursors, wherein a first precursor is selected from molecules with ring structures comprising SiCOH components and a second precursor is an organic molecule selected from the group consisting of molecules with ring structures.
It is a further object of the present invention to provide an improved method for fabricating an ultralow dielectric constant film in a parallel plate plasma enhanced chemical vapor deposition (“PECVD”) reactor.
It is yet a further object of the present invention to provide an improved method for fabricating an ultralow dielectric constant material by depositing a film on a substrate in the presence of CO
2
or CO
2
and O
2
, thereby improving uniformity of the film deposited and stabilizing the plasma within the PECVD reactor.
It is still a further object of the present invention to provide an improved method for fabricating an ultralow dielectric constant material for use in electronic structures as an intralevel or interlevel dielectric in a back-end-of-the-line (“BEOL”) interconnect structure.
It is yet another object of the present invention to provide a thermally stable ultralow dielectric constant material that has low internal stresses and a dielectric constant of not higher than about 2.8. More preferably, the dielectric constant for the ultralow-k material is in a range of about 1.5 to about 2.5 and, most preferably, the dielectric constant is in a range of about 2.0 to about 2.25.
In accordance with the present invention, there is provided an improved method for fabricating a thermally stable dielectric material that has a matrix comprising Si, C, O, and H atoms and an atomic level nanoporosity. In a preferred embodiment, the dielectric material has a matrix that consists essentially of Si, C, O, and H. The present invention further provides an improved method for fabricating the dielectric material by reacting a first precursor gas comprising atoms of Si, C, O, and H and at least a second precursor gas comprising atoms of C, H, and optionally O, F and N in a plasma enhanced chemical vapor deposition (“PECVD”) reactor. The present invention yet further provides for mixing the first precursor gas with CO
2
, or mixing the first and second precursor gases with CO
2
and O
2
, thereby stabilizing the plasma in the PECVD reactor and improving the uniformity of the film deposited on the substrate.
In a preferred embodiment, there is provided a method for fabricating a thermally stable ultralow dielectric constant (ultralow-k) film comprising the steps of: providing a plasma enhanced chemical vapor deposition (“PECVD”) reactor; positioning an electronic structure (i.e., substrate) in the reactor; flowing a first precursor gas comprising atoms of Si, C, O, and H into the reactor; flowing a second precursor gas mixture comprising atoms of C, H and optionally O, F and N into the reactor; and depositing an ultralow-k film on the substrate in the presence of CO
2
or CO
2
and O
2
. Preferably, the first precursor is selected from molecules with ring structures comprising SiCOH components such as 1, 3, 5, 7-tetramethylcycloterasiloxane (“TMCTS” or “C
4
H
16
O
4
Si
4
”). The second precursor may be an organic molecule selected from the group consisting of molecules with ring structures, preferably with more than one ring present in the mole
Grill Alfred
Patel Vishnubhai V.
Hoang Quoc
Scully, Scott, Murphy & Preseer
Trepp, Esq. Robert M.
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