Gas separation – Deflector
Reexamination Certificate
2000-09-15
2003-02-18
Smith, Duane (Department: 1724)
Gas separation
Deflector
C055S445000, C055S490000, C055S529000, C204S192120, C204S298110
Reexamination Certificate
active
06521010
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
The subject application is related to subject matter disclosed in Japanese Patent Application No. Hei 11-262711 filed on Sep. 16, 1999 in Japan to which the subject application claims priority under the Paris Convention and which is incorporated by reference herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to semiconductor device manufacturing apparatuses employing a PVD method, such as sputtering apparatuses and vacuum evaporation apparatuses. In particular, the present invention relates to a multicathode sputtering apparatus capable of reducing the cleaning frequency of filters, the filters themselves, a filtering frame, a semiconductor device manufacturing method, and a semiconductor device manufacturing apparatus.
2. Description of the Related Art
In the field of semiconductor devices, ground rules are becoming finer and the number of interconnection layers is increasing, to increase the aspect ratio (depth to diameter) of each via hole. As a result, a standard sputtering technique finds difficulty to fill such high-aspect-ratio via holes. To cope with this problem, there is a long-throw sputtering technique that elongates the distance between a target and a substrate and forms a film on the substrate only with particles that are straightly sputtered from the target toward the substrate. This technique is capable of correctly forming films in via holes and securing a sufficient coverage of each film. This technique, however, has a problem of causing asymmetry among films in via holes located along the periphery of a substrate and a problem of hardly forming a uniform film over the surface of a substrate. The larger the diameters of substrates or silicon wafers, the more the problems of asymmetry and unevenness become serious. To solve these problems, Japanese Unexamined Patent Publications Hei 10-121235 and Hei 11-29859 propose a multicathode sputtering apparatus that arranges a plurality of cathodes and corresponding targets in a chamber. This apparatus employs filters that pass only vertically oriented particles to form a film on a substrate, thereby improving the overall uniformity of the film.
FIG. 1
shows a film forming state of a multicathode sputtering apparatus according to a prior art. A chamber
5
accommodates targets
41
to
43
that are attached to cathodes, respectively. The targets
41
to
43
face a substrate
8
with filters
71
to
73
interposing between them. The filters
71
to
73
have openings corresponding to the targets
41
to
43
, respectively. The diameter of each opening is greater than the diameter of the target. The chamber
5
has an outlet
6
connected to a vacuum pump (not shown).
To form a film on the substrate
8
, the chamber
5
is evacuated to a predetermined pressure, and argon gas is introduced into the chamber
5
through an inlet
7
to a sputtering pressure. Power sources
61
to
63
apply predetermined power to the cathodes to produce plasma on the targets
41
to
43
to sputter particles from the targets
41
to
43
. The sputtered particles pass through the openings of the filters
71
to
73
and deposit on the substrate
8
.
The sputtered particles linearly advance from the targets
41
to
43
according to the cosine rule at any angles with respect to normal lines extended from the targets. Particles of large angles hit and deposit on the filters
71
to
73
without reaching the substrate
8
. Only geometrically reachable particles arrive at the substrate
8
and deposit thereon to form a film, thereby suppressing overhangs on steps and via holes, improving the coverage of the film over the substrate
8
, and eliminating asymmetry in the film. By individually changing the power to the cathodes, the uniformity of a film on the substrate
8
may be improved.
This prior art, however, deposits particles around the openings of only the filter
71
that is closest to the cathodes, among the filters
71
to
73
. When the particles on the filter
71
exceed a certain thickness, they peel off the filter
71
and drop onto the substrate
8
, to form clusters of particles on the substrate
8
. To avoid this, the prior art must frequently wash the filter
71
, which deteriorates the mean time between maintenances of the apparatus. The peeling problem frequently occurs when forming titanium nitride (TiN) films or tantalum nitride (TaN) films, to greatly deteriorate productivity.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a filter capable of minimizing particles depositing thereon.
Another object of the present invention is to provide a filter capable of preventing particles peeled off the same from dropping onto a substrate.
Still another object of the present invention is to provide a filtering frame capable of minimizing particles depositing thereon.
Still another object of the present invention is to provide a filtering frame capable of preventing particles peeled off the same from dropping onto a substrate.
Still another object of the present invention is to provide a semiconductor device manufacturing apparatus capable of minimizing particles depositing on filters.
Still another object of the present invention is to provide a semiconductor device manufacturing apparatus capable of preventing particles peeled off filters from dropping onto a substrate.
Still another object of the present invention is to provide a semiconductor device manufacturing method capable of minimizing particles depositing on filters.
In order to accomplish the objects, a first aspect of the present invention provides a filter having a flat plate with circular openings and a funnel provided for each of the openings. Each funnel has a bottom opening matching with the plate opening and a top opening smaller than the bottom opening. A normal line extended from the center of the top opening coincides with a normal line extended from the center of the bottom opening and is in parallel with a normal line extended from the plate. Sputtered particles deposit on an outer face of each funnel. Since sputtered face is wide, the deposited particles spread into a thin film. This elongates a time to cause the peeling of the film off the funnels, prevents the formation of clusters of particles on a substrate, and extends the life of the filter. Even if the film on the funnels peels off, it will stay on the filter because the peeled film is unable to go beyond the funnels. Accordingly, no peeled film drops onto the substrate. Each funnel passes particles sputtered from only an overhead target and blocks particles sputtered from adjacent targets. This improves the directivity of sputtered particles to form a uniform film on the substrate. For each funnel, particles sputtered from adjacent targets except an overhead target hit the outer face of the funnel substantially at a right angle, and therefore, the particles deposited on the funnel strongly adhere thereto and hardly peel off.
According to the first aspect, the bottom openings of adjacent funnels may partly overlap one another, and the overlapping parts of the adjacent funnels may be cut. This arrangement enables the distance between adjacent targets to be freely set without regard to the dimensions of the funnels.
According to the first aspect, the flat plate may be a flat disk so that the filter may easily be rotated in a sputtering apparatus to improve the uniformity of a film formed on a substrate.
A second aspect of the present invention provides a filtering frame having a first filter made of a flat plate having first circular openings, and a second filter that is in parallel with the first filter and has second circular openings corresponding to the first openings, respectively, the diameter of the second openings being smaller than that of the first openings, normal lines extended from the centers of each pair of the first and second openings coinciding with each other. The filtering frame is installed in a sputtering apparatus such that the first filter is closer to cathodes than the secon
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Greene Jason M.
Kabushiki Kaisha Toshiba
Smith Duane
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