Coating processes – Electrical product produced – Integrated circuit – printed circuit – or circuit board
Reexamination Certificate
1998-07-06
2001-01-16
Talbot, Brian K. (Department: 1762)
Coating processes
Electrical product produced
Integrated circuit, printed circuit, or circuit board
C427S099300, C427S124000, C427S255280, C427S255700, C438S652000, C438S675000, C438S680000, C438S681000
Reexamination Certificate
active
06174563
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for forming thin metal films, and more specifically, it relates to a method for forming thin metal films for wiring.
2. Description of the Related Art
For forming high integration and high speed LSIs, the design of the LSIs becomes more exacting, so that as the width of wires and the diameter of via holes decrease, there results an increase of the aspect ration. As a method of embedding the grooves for wires and the via holes, there has been developed a method for forming metal films by chemical vapor deposition technique which in principle provides excellent step coverage.
An example of conventional formation methods of thin metal films is shown in FIG.
2
. This conventional example is described in “Proceedings of VLSI Multilevel Interconnection Conference”, 1993, p. 463-469. According to this formation method of thin metal films, an insulating film
102
is first deposited all over the surface of a substrate
101
as shown in FIG.
2
(
a
), and a via hole
104
is then bored. In succession, a barrier metal
103
is deposited. Next, an aluminum film
105
is deposited in accordance with a chemical vapor deposition technique using dimethylaluminum-hydride. At this time, a void
106
occasionally is formed in the via hole
104
, as shown in FIG.
2
(
b
). The formation of the void is caused by the fact that the aluminum film deposited by the chemical vapor deposition technique has a rough surface. That is to say, in the course of the deposition of the aluminum film, the surface of the aluminum film is chapped, and recesses of the film come in contact with each other in the upper portion of the via hole, whereby the feed of raw material to the inside of the via hole is blocked, so that the recesses remain in the form of the void.
In the above-mentioned conventional example, current density increases due to the void in the via hole, so that the migration phenomenon of an aluminum atom by current called electromigration increases, with the result that wires are liable to be broken and the reliability of the wiring deteriorates inconveniently.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for forming thin metal films which solve the above-mentioned problems of the prior art and which can accomplish the complete embedding of a via hole.
The aspects of the present invention are as follows:
A method for forming thin metal films for wiring which comprises a step of depositing an insulating film on a substrate and forming a via hole or a groove for wiring in the insulating film, a step of forming, by a chemical vapor deposition technique, a first metal film as an undercoat all over the surface of the substrate on which the via hole or the groove for wiring is formed, and a step of forming a second metal film of the same kind of metal as the first metal film to a desired thickness at a temperature higher than a deposition temperature at the time of the formation of the first metal film by the chemical vapor deposition technique.
In forming thin metal films in accordance with the present invention there is used as a raw material for the chemical vapor deposition of the first metal film, a material having a decomposition temperature lower than the decomposition temperature of a raw material used in the chemical vapor deposition of the second metal film.
Preferably the main component of the first and second metal films is aluminum or copper.
In a particularly preferred embodiment of the invention the raw material of the first and second metal films is selected from the group consisting of triisobutylaluminum (TIBA), dimethylaluminum-hydride (DMAH), monomethylaluminum-dihydride (MMADH), diethylaluminum-hydride (DEAH), trimethylaminealane (TMAA), triethylaminealane (TEAA) and dimethylethylaminealane (DMEAA) or the raw material of the first and second metal films is selected from the group consisting of hexafluoroacetylacetonatocopper trimethylvinylsilane (hfac)Cu(VTMS), cyclopentadienyltriethylphosphinecopper CpCuTEP, acetylacetonatocopper Cu(ACAC)
2
, dipivaloylmethanecopper Cu(DPM)
2
, heptafluorobutanoylpivaloylmethanecopper Cu(FOD)
2
, pentafluoropropanoylpivaloylmethanecopper Cu(PPM)
2
and hexafluorobutanoylpivaloylmethanecopper Cu(HFA)
2
.
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patent: 5151305 (1992-09-01), Matsumoto et al.
patent: 5175125 (1992-12-01), Wong
patent: 5231056 (1993-07-01), Sanshu
patent: 5371042 (1994-12-01), Ong
patent: 5523259 (1996-06-01), Merchant et al.
patent: 5545591 (1996-08-01), Sugai et al.
patent: 3291920 (1991-12-01), None
patent: 41498 (1992-01-01), None
patent: 5136138 (1993-06-01), None
patent: 115073 (1995-05-01), None
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patent: 8-8253 (1996-01-01), None
“Sub-Half Micron Aluminum Metallization Technology Using a Combination of CVD and Sputtering” Sugai et al Jun. 8-9, 1993; VMIC Conference; pp. 463-469.
Hayes, Soloway, Hennesey, Grossman & Hage, P.C.
NEC Corporation
Talbot Brian K.
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