Semiconductor device manufacturing: process – Chemical etching
Reexamination Certificate
2000-06-30
2002-12-10
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Chemical etching
C438S687000, C438S688000, C438S712000
Reexamination Certificate
active
06492271
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-187023, filed Jun. 30, 1999; and No. 2000-187995, filed Jun. 22, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device having a wiring structure capable of preventing a short-circuiting between a W damascene wiring and a plug and a method of manufacturing the same.
A buried tungsten wiring structure (W damascene wiring structure) is used nowadays in many cases in a semiconductor device such as DRAM.
FIG. 15
shows the conventional W damascene wiring structure, comprising an interlayer insulating film
81
, a barrier metal layer
82
, a W wiring
83
, and a cap insulating film
84
. The barrier metal film
82
is formed of a titanium nitride film.
In the W damascene wiring structure shown in
FIG. 15
, the entire W wire
83
is covered with the barrier metal film
82
and the cap insulating film
84
, making it possible to prevent an adverse effect from being given to the device by the tungsten diffusion.
In the case of using the W damascene wiring structure shown in
FIG. 15
, the aligning mark cannot be recognized because the surface of the interlayer insulating film
81
is not planarized and, thus, deviation in alignment tends to take place. Therefore, where a contact hole is made in the interlayer insulating film
81
for forming a plug
85
, a short-circuiting tends to take place between the W wiring
83
and the plug
85
.
In order to overcome the above-noted problem, it is conceivable to employ the wiring structure as shown in
FIG. 17A
or FIG.
17
B. In the wiring structure shown in each of these drawings, the barrier metal film
82
in an upper portion of the wiring groove, said barrier metal film
82
causing a short-circuiting problem, is removed.
In order to realize the wiring structure shown in
FIG. 17A
, the barrier metal film
82
and the W wiring
83
must be non-selectively etched as shown in FIG.
18
A. Alternatively, it is necessary to selectively etch the barrier metal film
82
relative to the W wiring
83
, as shown in FIG.
18
B. Likewise, similar non-selective or selective etching must be performed for realizing the wiring structure shown in FIG.
18
B.
The etching includes a dry etching and a wet etching. The dry etching includes an anisotropic etching called RIE (Reactive Ion Etching) and an isotropic etching called CDE (Chemical Dry Etching). However, it is difficult to perform the non-selective etching and the selective etching shown
FIGS. 18A and 18B
by these etching methods. Particularly, it is substantially impossible to achieve the selective etching shown in FIG.
18
B.
It should also be noted that a CF-based gas, which produces a serious problem in terms of the earth environment, is used as a raw material gas in the dry etching. Further, a wet etching is performed after the dry etching for removing the by-products of the dry etching. It follows that the dry etching process is disadvantageous in the number of process steps required and the cost, compared with the wet etching process.
On the other hand, it is known to the art concerning the wet etching that tungsten and titanium nitride can be etched by chemicals having an oxidizing power. To be more specific, tungsten and titanium nitride can be dissolved in hydrochloric acid mixed with a hydrogen peroxide solution, i.e., hydrochloric acid allowed to produce an oxidizing power.
In general, a mixed solution of hydrochloric acid and a hydrogen peroxide solution is used as a cleaning solution and called SC
2
. In many cases, each of hydrochloric acid and hydrogen peroxide solution available on the market has a concentration of about 30 to 35%. These hydrochloric acid and hydrogen peroxide solution are mixed at a mixing ratio of 1:1 and the mixture is diluted with pure water in an amount 5 to 6 times as much as the amount of the original mixture for use as an etchant, as disclosed in, for example, Japanese Patent Disclosure (Kokai) No. 10-64866, Japanese patent Disclosure No. 8-153788 and Japanese Patent Disclosure No. 9-64006. Incidentally, the molar ratio of the hydrogen peroxide to hydrogen chloride in the hydrochloric acid is about 1.
If tungsten and titanium nitride are etched with the etchant described above, the etching rate of the tungsten is about 4 to 5 times as high as that of titanium nitride. Particularly, tungsten can be etched with only the hydrogen peroxide solution that is weakly acidic. It follows that in the conventional wet etching using a mixed solution of hydrochloric acid and a hydrogen peroxide solution, it was difficult to increase the selectivity ratio of titanium nitride relative to tungsten to exceed 1.
Also, the cleaning using a mixed solution of sulfuric acid and a hydrogen peroxide solution is called an SP cleaning, which is generally employed for removing a resist film. Disclosed in, for example, Japanese Patent Disclosure No. 10-50986 is an etching method for selectively etching a TiN film relative to a W film, a Cu film or a TiSi film by using the mixed solution noted above. In this method, it is possible to achieve at least 20 nm/min of the TiN film etching rate and at least 7 nm/min of the W film etching rate by using a mixed solution consisting of 1 part of sulfuric acid and 6 parts of a hydrogen peroxide solution and by setting the process temperature at 130° C. However, if the process temperature exceeds 100° C., it is difficult to use a pure water as a diluent, leading to an increased amount of the mixed solution consisting of sulfuric acid and hydrogen peroxide solution used as the etchant.
Another difficulty is brought about in the case of the batch treatment in which a plurality of wafers are processed simultaneously by employing the etching method described above. Specifically, in the case of etching a thin TiN film that is about 20 nm thick, it is difficult to achieve a uniform etching because the TiN film exhibits a high etching rate. A similar etching method, which is disclosed in Japanese Patent Disclosure No. 9-293727, also gives rise to a similar problem.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of manufacturing a semiconductor device, which permits easily performing a selective etching and a non-selective etching in a tungsten-titanium nitride system.
Another object of the present invention is to provide a semiconductor device having a wiring structure that permits preventing a short-circuiting between a W damascene wiring and a plug, which can be easily achieved by the method of the present invention for manufacturing a semiconductor device.
According to a first aspect of the present invention, which is intended to achieve the objects described above, there is provided a semiconductor device, comprising a silicon oxide film having a wiring groove, a silicon nitride film formed on a side wall of the wiring groove and not filling the side wall, a first tungsten film formed to extend from the bottom of the wiring groove to reach a central portion of the side wall of the wiring groove and thinner in the side wall portion than the central portion of the wiring groove, a titanium nitride film formed between the first tungsten film and the side wall of the wiring groove, a second tungsten film formed between the titanium nitride film and the first tungsten film and thinner than the first tungsten film, and a silicon nitride film formed on the second tungsten film to fill the wiring groove.
According to a second aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising an etching step using a mixed solution containing hydrochloric acid and a hydrogen peroxide solution, the molar ratio of hydrogen peroxide in the hydrogen peroxide solution to hydrogen chloride in the hydrochloric acid being 1/100 or less.
According to a third aspect of the present invention, there is provided a method of manufact
Nadahara Soichi
Ogawa Yoshihiro
Okuchi Hisashi
Tomita Hiroshi
Uozumi Yoshihiro
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
Luk Olivia
Niebling John F.
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