Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2001-06-15
2004-05-04
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S672000, C438S675000, C438S681000, C438S662000
Reexamination Certificate
active
06730596
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of and an apparatus for forming an interconnection, and more particularly to a method of and an apparatus for forming a fine interconnection in a highly integrated circuit formed on a semiconductor substrate such as a semiconductor wafer or the like.
BACKGROUND ART
Aluminum or aluminum alloy has generally been used as a material for forming interconnection circuits on semiconductor substrates. It has been customary to grow a film of the material according to a process such as sputtering, CVD, or the like and then produce a pattern in the film according to etching or the like. As the level of circuit integration increases in recent years, there is a demand for the usage of silver, copper or its alloy, which has a higher conductivity, as an interconnection material. Since it is difficult to etch these materials, it has been proposed to immerse a substrate having interconnection pattern trenches therein in a plating liquid and perform electrolytic or electroless plating on the substrate to embed the trenches with silver, copper or its alloy.
However, while the plating processes are an inexpensive and highly technically accomplished technology, the electrolytic plating process is capable of growing a film only on an electrically conductive material, whereas the electroless plating process suffers a problem in that substances contained in the plating liquid affect the natural environment and the working environment. Accordingly, there has been a strong need for the development of a metal interconnection technology as a substitute for the plating processes.
DISCLOSURE OF INVENTION
The present invention has been made in view of the foregoing problems and demand. It is an object of the present invention to provide a method of and an apparatus for forming an interconnection by stably depositing an interconnection metal of good quality as a substitute for the conventional plating processes.
According to an invention described in claim
1
, there is provided a method of forming an interconnection, comprising the steps of preparing a substrate having fine recesses formed in a surface thereof, dispersing ultrafine particles made at least partly of a metal in a predetermined solvent, producing an ultrafine particle dispersed liquid, supplying the ultrafine particle dispersed liquid to the fine recesses of the substrate, heating the substrate to melt and bond the metal, and chemical mechanical polishing the surface of the substrate to remove an excessively attached metal therefrom.
With the above arrangement, it is possible to easily form interconnections according to so-called single and dual damascene processes.
The ultrafine particle dispersed liquid may be placed in a container, providing a liquid reservoir, and the substrate may be immersed in the liquid reservoir to supply the ultrafine particle dispersed liquid to only the fine recesses of the substrate. Alternatively, the ultrafine particle dispersed liquid may be supplied to the fine recesses of the substrate by being coated or sprayed in the fine recesses of the substrate and/or on areas surrounding the fine recesses. Furthermore, the ultrafine particle dispersed liquid may be coated by a spin coating process.
According to an invention described in claim
2
, the method according to claim
1
comprises the step of evaporating the solvent between the step of supplying the ultrafine particle dispersed liquid to the fine recesses of the substrate and the step of heating the substrate to melt and bond the metal.
According to an invention described in claim
3
, in the method according to claim
1
or
2
, each of the ultrafine particles comprises an ultrafine composite metal particle comprising a core made substantially of a metal component and a covering layer made of an organic substance chemically bonded to the core.
For manufacturing ultrafine particles made at least partly of a metal, there has been proposed a process of evaporating the metal in a vacuum in the presence of a small amount of a gas to agglomerate ultrafine particles made of only the metal from the gas phase, producing ultrafine metal particles. Such a physical process, however, does not lend itself to mass production as the amount of generated ultrafine metal particles is small, and is costly because a device for generating an electron beam, a plasma, or a laser beam, etc. or a device for performing inductive heating is necessary to evaporate the metal. In addition, since the particle diameters range in a wide distribution, some of the metal particles remain unmelted when heated, failing to obtain a uniform metal film of low resistance.
When ultrafine particles made of only the metal is used, the ultrafine particles tend to agglomerate in a dispersed liquid, the ultrafine particle dispersed liquid is liable to provide an irregular covering layer. One solution would be to add a suitable surface active agent to the ultrafine particle dispersed liquid to turn them into a protective colloid. However, such a protective colloid fails to provide sufficient dispersion stability.
The bonded structure of ultrafine composite metal particles according to the present invention appears to be such that a core made of a metal component and an organic compound making up a covering layer share metal molecules, or an organic compound and a core form a complex-analogous structure by way of an ionic bond, through the details of the bonded structure are not clear. Since such ultrafine composite metal particles can be produced by a chemical process in a liquid phase, they can be mass-produced at a reduced cost in an ordinary atmospheric environment with a simple apparatus without the need for a large vacuum device. Since the ultrafine composite metal particles have a uniform diameter, all the ultrafine composite metal particles are fused together at a constant temperature. Inasmuch as the ultrafine composite metal particles are covered with an organic metal compound therearound, their ability to agglomerate in a solvent is small, and hence they can easily be scattered uniformly over the surface of the substrate. The ultrafine composite metal particles are stable and hence can easily be handled. Even after the solvent is evaporated, the ultrafine composite metal particles remain chemically stable until they are decomposed with heat and can be handled for easy process management.
According to a method described in claim
4
, in the claim according to any one of claims
1
through
3
, the ultrafine particles have an average diameter ranging from 1 to 20 nm.
It is known that the melting point of a metal particle is lowered as the diameter thereof is reduced. This effect starts to manifest itself when the diameter of the metal particle is 20 nm or less, and becomes distinctive when the diameter of the metal particle is 10 nm or less. Therefore, the average diameter of the ultrafine particles are preferably in the range from 1 to 20 nm, and preferably in the range from 1 to 10 nm depending on the shape and dimensions of the fine recesses and the structure of the semiconductor device.
According to a method described in claim
5
, in the method according to any one of claims
1
through
4
, the ultrafine particle dispersed liquid has a predetermined surface tension to increase adhesiveness of the ultrafine particle dispersed liquid to the fine recesses of the substrate and/or areas surrounding the fine recesses.
With the ultrafine particle dispersed liquid having a predetermined surface tension, the applicability of the ultrafine particle dispersed liquid in the fine recesses of the substrate and on areas surrounding the fine recesses is increased. Thus, the substrate with a large amount of liquid held thereon can be dried, so that a sufficient amount of ultrafine particles can be supplied to the recesses and the areas surrounding the fine recesses. Consequently, it is not necessary to repeat the applying and drying steps, and the fine recesses can be filled with the metal according to a simple process.
According to an invention describ
Fukunaga Akira
Hongo Akihisa
Horie Kuniaki
Kato Takao
Nagasawa Hiroshi
Browdy and Neimark , P.L.L.C.
Ebara Corporation
Rocchegiani Renzo N
Smith Matthew
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