Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
1998-12-03
2001-03-20
Nguyen, Nam (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S192150
Reexamination Certificate
active
06203674
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a continuous forming method for Ti/TiN film, and more particularly to a Ti/TiN film continuous forming method for freely controlling a TiN film forming process so that a TiN film formed has such film quality as a nitride TiN film or a metallic mode TiN film in the TiN film forming process.
Following high-integration design of semiconductor devices, more minute and more multiple layer structure is being promoted for the wiring structure. As such an enhancement in minuteness and layer-multiplicity of the wiring structure is promoted, a multiple-layer wiring technique is growing more sophisticated technologically, and the technical position which the multiple-layer wiring technique occupies in the manufacturing process for semiconductor integrated circuits is more and more important.
Particularly for semiconductor devices based on the design rule subsequent to 0.5 &mgr;m are increasingly used such a wiring structure that metal of high melting point such as titanium (hereinafter referred to as “Ti”), titanium nitride (hereinafter referred to as “TiN”) or the like is laminated as barrier metal on the upper or lower surface of aluminum alloy formed as a wiring film, for example, Al—Si film, Al—Si—Cu film or the like, or on both the upper and lower surfaces thereof.
Here, the conventional laminated wiring structure having a high melting point metal film as barrier metal will be described with reference to
FIGS. 1A
to
1
D.
FIGS. 1A
to
1
D are cross-sectional views showing various wiring structures.
The wiring structure shown in
FIG. 1A
is a laminated wire comprising a Ti film
11
of 20 nm in thickness, and a TiN film
12
of 70 nm in thickness which is formed on the Ti film
11
.
The wiring structure shown in
FIG. 1B
is a laminated wire comprising a Ti film
13
of 20 nm in thickness, a TiN/Ti film
14
of 20 nm/5 nm in thickness respectively, an Al—Cu film
15
of 500 nm in thickness and a Ti/TiN/Ti film
16
of 5 nm/100 nm/5 nm in thickness respectively, these films being successively formed in this order.
The wiring structure shown in
FIG. 1C
is a laminated wire comprising a Ti film
17
of 100 nm in thickness, a TiN/Ti film
18
of 20 nm/5 nm in thickness respectively, an Al—Cu film
19
of 500 nm in thickness and a TiN/Ti film
20
of 35 nm/5 nm in thickness respectively, these films being successively formed in this order.
The wiring structure shown in
FIG. 1D
is a laminated wire comprising a Ti film
21
of 200 nm in thickness, a TiN/Ti film
22
of 20 nm/5 nm in thickness respectively, an Al—Si film
23
of 900 nm in thickness, and a TiN film
24
of 35 nm in thickness, these films being successively formed in this order.
As described above, wires having the laminated wiring structure containing five to seven layers have been used in semiconductor devices mass-produced in the 0.35 &mgr;m design rule generation.
A so-called multi-chamber type sputtering device is used to form the laminated wiring structures shown in
FIGS. 1A
to
1
D. Here, the construction of the multi-chamber type sputtering device will be described with reference to FIG.
2
.
FIG. 2
is a schematic plan view showing the construction of the multi-chamber type sputtering device.
As shown in
FIG. 2
, the multi-chamber type sputtering device has plural process chambers each containing a sputtering material (target) which is connected with the kind of each film formed (hereinafter referred to as “chamber”). With this multi-chamber type sputtering device, one kind of metal film is formed on a wafer by using one chamber. A wafer is sequentially fed into the plural chambers and the film formation is repeated to form a laminated film. In the multi-chamber type sputtering device, the respective wafers are sequentially processed in turn.
More specifically, the multi-chamber type sputtering device
30
includes plural chambers
32
A to
32
D (in the case of
FIG. 2
, four chambers are illustrated) in which desired targets are respectively mounted, a feeding arm
33
for feeding the wafers, a separation chamber
34
which intercommunicates with each of the chambers
32
A to
32
D through a gate valve (not shown), and a load lock chamber
38
which intercommunicates with the separation chamber
34
and also intercommunicates with the external through a gate valve
36
.
As not shown, in each of the chambers
32
A to
32
D are provided a cathode electrode which will serve as a sputtering source by mounting a target of a desired sputtering material, a wafer holder for holding the wafers, a gas inlet port for reaction gas, a cryopump connected to each chamber through a discharge valve to keep the inside of the chamber under high vacuum, etc.
When a metal film is formed on a wafer by sputtering, a wafer cassette in which wafers are mounted is first automatically fed to the load lock chamber
38
, and then a wafer W is fed from the wafer cassette to the separation chamber
34
by the feeding arm
33
. Subsequently, the wafer W is fed into one of the chambers
32
A-
32
D to be subjected to the sputtering process, and mounted on the wafer holder. In one of the chambers
32
A-
32
D, a metal film is formed on the wafer on the wafer holder by the sputtering method according to a predetermined recipe.
After the film formation of the metal film is completed, the wafer is taken out from one of the chambers
32
A-
32
D, and fed through the separation chamber
34
to the next chamber
32
A,
32
B,
32
C or
32
D to perform the similar film forming process. The wafer W thus treated is mounted on the wafer cassette of the load lock chamber
38
, and the wafer cassette is taken out to the outside, thereby completing the overall process.
Such a multi-chamber type sputtering device has a restriction that the number of chambers which can be equipped is limited to three or four. Accordingly, when a multilayered film having four layers or five layer or more is formed, it is necessary to continuously form different kinds of metal films in the same chamber.
Particularly when a Ti film and TiN film are continuously formed (hereinafter referred to as “continuous formation of Ti/TiN film”), the Ti/TiN film is formed by the following process because the continuous formation thereof is relatively easy. That is, in this process, a chamber in which a Ti target is mounted is used, and argon gas (hereinafter referred to as “Ar gas”) is introduced in a Ti film forming step. Further, reaction gas containing a mixture of Ar gas and nitride gas (hereinafter referred to as “N
2
gas”) is introduced in a TiN film forming step, thereby forming a TiN film by a reactive sputtering method.
That is, when the Ti/TiN film is continuously formed, the Ti target is first sputtered while Ar gas flows, thereby forming the Ti film on the wafer, and then mixture gas of Ar gas and N
2
gas flows to sputter the Ti target whose surface is nitrided, thereby continuously forming the TiN film on the Ti film.
The TiN film is roughly classified into a nitride mode TiN film and a metallic mode TiN film from the viewpoint of film quality. The nitride mode TiN film is defined as a TiN film having high barrier performance which is obtained by sputtering Ti target while sufficiently exposing the surface of the Ti target to N
2
plasma to nitride the surface of the Ti target. On the other hand, the metallic mode TiN film is defined as a TiN film obtained by sputtering target containing a large amount of Ti components such as Ti
2
N or the like. The selective formation of the nitride mode TiN and the metallic mode TiN can be performed by adjusting the ratio of Ar gas and N
2
gas or setting the flow rate of N
2
to a predetermined rate or more.
The TiN film which has been hitherto used as a wiring film is the nitride mode TiN film having higher barrier performance. Accordingly, when the Ti/TiN film is continuously formed in one chamber in the above manner, it is a technical great problem whether the TiN film formed has desired film quality or not, that is, whether the TiN film formed is the nitride mode TiN film
Nguyen Nam
Sonnenschein Nath & Rosenthal
Sony Corporation
Ver Steeg Steven H.
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