JP3592209B2 - Method for manufacturing semiconductor device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor device, particularly a semiconductor device having a multilayer wiring.
[0002]
[Prior art]
With the increase in the density of semiconductor integrated circuit devices and the miniaturization of element patterns, new technologies such as chemical mechanical polishing (CMP) have been introduced to the formation of metal plugs embedded in contact holes and via holes attached to wiring. Is coming. FIG. 5 shows an example of a conventional method of manufacturing a semiconductor device using a CMP method for forming such a metal plug.
[0003]
First, an interlayer insulating film 102 is deposited on a semiconductor substrate 101 on which a transistor, a diffusion layer, and the like are formed by a known technique, and the surface is flattened using a CMP method or the like (FIG. 5A). Next, a contact hole 103 connected to the semiconductor substrate 101 is formed in the interlayer insulating film 102 (FIG. 5B). Further, a barrier metal 104 made of, for example, a titanium nitride / titanium laminated film is formed, and then a tungsten film 105 is formed by a CVD method or the like (FIG. 5C).
[0004]
Thereafter, the tungsten film 105 and the barrier metal 104 are polished by using the CMP method until the surface of the interlayer insulating film 102 is exposed to form a tungsten plug 106 (FIG. 5D). Next, a titanium film 107, a titanium nitride film 108, an aluminum alloy film 109, and a titanium nitride film 110, which are adhesion layers with the interlayer insulating film 102, are successively sequentially deposited by a sputtering method (FIG. 5E). The wiring is patterned using a dry etching method (FIG. 5F).
[0005]
[Problems to be solved by the invention]
Incidentally, in general, the titanium film 107 and the titanium nitride film 108 are continuously formed in the same chamber of a sputtering apparatus using the same titanium target. This is for improving the throughput in forming the titanium / titanium nitride laminated film and improving the productivity. The titanium nitride film 108 is formed in a chamber into which an argon gas and a nitrogen gas are introduced. Therefore, after the formation of the titanium nitride film, the surface of the titanium target is nitrided. A clean titanium film cannot be formed from this titanium target. When titanium containing nitrogen is formed at the contact interface of the titanium film 107 on the semiconductor substrate 101 side, the contact resistance increases. Therefore, before the next semiconductor substrate is disposed to face the titanium target and the titanium film 107 is formed on this semiconductor substrate, it is necessary to perform cleaning for removing titanium nitride on the surface of the titanium target.
[0006]
In recent years, the sputtering apparatus used in the above manufacturing process is of a single-wafer type, and the volume of the chamber is designed to be as small as possible. For this reason, no shutter is provided on the target. Therefore, in the step of cleaning the titanium target, a small amount of titanium is formed on the titanium nitride film 8 already formed on the semiconductor substrate.
[0007]
If there is a thin titanium film due to the slight deposition of titanium, as shown in FIG. 6, aluminum in the aluminum alloy film 109 reacts with titanium 120 on the titanium nitride film 108 to form an alloy. A titanium-aluminum product 120 is formed in the aluminum alloy film near the boundary. The titanium-aluminum product easily moves as a migration path when a thermal stress is applied to the entire semiconductor substrate at 180 ° C. for several tens of hours, so that voids are formed in the aluminum alloy film 109 and reliability is deteriorated. (Stress migration).
[0008]
Therefore, an object of the present invention is to provide a method for manufacturing a highly reliable semiconductor device in which stress migration is suppressed.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention includes a step of sequentially depositing a titanium film and a titanium nitride film on an insulating film formed on a semiconductor substrate by a sputtering method; Sputtering cleaning the surface of the titanium target used for deposition of the titanium target, oxidizing the titanium adhered to the surface of the titanium nitride film by the sputtering cleaning, and forming the titanium nitride film on the oxidized titanium nitride film. Depositing a metal film containing aluminum as a main component.
[0010]
When the above oxidation step is applied to a thin titanium film formed on a titanium nitride film by sputtering cleaning the surface of a titanium target, even if a metal film such as an aluminum alloy film is formed thereafter, titanium A product alloyed with aluminum is not formed. Therefore, stress migration is suppressed, and the reliability of the wiring is improved.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described.
After the sputtering cleaning, the surface of the titanium nitride film is treated by at least one selected from plasma treatment, heat treatment, liquid contact treatment, and etching treatment. By this treatment, a small amount of titanium present on the surface of titanium nitride can be changed to a titanium compound or removed. Thus, by removing at least titanium as a simple substance (metal) from the titanium nitride film, formation of an alloy of titanium and aluminum can be prevented.
[0013]
Hereinafter, each of the above processes will be described.
The plasma treatment is preferably treatment with oxidizing plasma or nitriding plasma. Here, the oxidizing or nitriding plasma may include oxygen or nitrogen in a plasma state, respectively, and may include plasma of another atom (for example, plasma of an inert gas). Plasma containing both oxygen and nitrogen may be used. As the plasma, nitrogen plasma is particularly preferable.
[0014]
The heat treatment is preferably performed in an oxidizing atmosphere or a nitriding atmosphere. Here, the oxidizing or nitriding atmosphere may be an atmosphere containing oxygen or nitrogen, respectively, and other gases may be present. An atmosphere in which oxygen and nitrogen are present, for example, an atmospheric component may be used. As the atmosphere, a nitrogen atmosphere is particularly preferable.
[0015]
The heat treatment temperature is equal to or higher than ordinary temperature, preferably 100 to 500 ° C, more preferably 300 to 500 ° C. Although the heat treatment time depends on the heat treatment temperature, for example, when the treatment is performed at 300 to 500 ° C., about 10 to 15 minutes is preferable. If the heat treatment temperature is too high or the heat treatment time is too long, an undesirable reaction may occur between compounds formed before the heat treatment or between the compound and the semiconductor substrate.
[0016]
The liquid contact treatment is a treatment in which a liquid is brought into contact with the surface of the titanium nitride film. As the liquid, a liquid containing water (particularly pure water), an acid or an organic compound is preferable. As the acid, fuming nitric acid is particularly preferred. Examples of the organic compound include tetramethylammonium formate, N, N-dimethylformamide, and propionic acid.
[0017]
The etching process may be wet etching, but here, application of dry etching is mainly considered. As an etching gas, SF ₆ + Ar and Cl ₂ + BCl ₃ are particularly preferable.
[0018]
Comparing the above treatments, the plasma treatment is advantageous in that titanium can be completely oxidized or completely nitrided, and the heat treatment is preferable in that it has an action of alleviating stress due to film formation. In addition, the liquid contacting treatment is advantageous in that the cleaning of the semiconductor substrate after sputtering can be performed at the same time, and the etching treatment is preferable in that titanium on titanium nitride can be completely removed. However, the process applicable to the method of the present invention is not limited to the above-described processes as long as the process can prevent titanium on the titanium nitride film from existing as a metal.
[0019]
Hereinafter, preferred embodiments of the present invention will be further described with reference to the drawings.
(Embodiment 1)
First, as conventionally performed, an interlayer insulating film 2 is deposited on a semiconductor substrate 1 on which a transistor, a diffusion layer, and the like are formed, and the surface is flattened using a CMP method or the like (FIG. 1A). ). Next, a contact hole 3 connected to the semiconductor substrate 1 is formed in the interlayer insulating film 2 (FIG. 1B). The contact hole is a through hole of the interlayer insulating film. Further, a barrier metal 4 made of, for example, a titanium nitride / titanium laminated film is formed, and a tungsten film 5 is formed on the barrier metal by a CVD method or the like (FIG. 1C). Subsequently, the tungsten film 5 and the barrier metal 4 are polished by etch back by a CMP method, dry etching or the like until the surface of the interlayer insulating film 2 is exposed, thereby forming a tungsten plug 6 embedded in the interlayer insulating film ( FIG. 1 (d)).
[0020]
Thereafter, a titanium film 7 and a titanium nitride film 8, which are adhesion layers with this layer, are successively deposited on the interlayer insulating film 2. This deposition may be performed using a single-wafer type standard sputtering apparatus having no shutter on the target. When the titanium nitride film 8 is deposited by sputtering using argon and nitrogen (reactive sputtering), a titanium nitride layer is formed on the surface of the titanium target. When this titanium nitride layer is removed by cleaning by sputtering, an extremely thin titanium film is formed on the surface of the titanium nitride film 8. The thickness of this titanium film is usually about 3 nm to 5 nm.
[0021]
In order to remove this thin titanium film, the above-described processing (here, processing using oxygen plasma 20) is applied (FIG. 1E). When the surface of the titanium nitride film was exposed to oxygen plasma (60 ° C., 3 minutes), it was confirmed that the titanium film on the titanium nitride film was almost completely oxidized .
[0022]
Note that the treatment with the oxygen plasma 20 is preferably performed in a chamber different from a deposition chamber of a sputtering apparatus for a titanium film or the like. This is because contamination of oxygen can be avoided.
[0023]
Here, oxygen plasma is applied, but any other plasma such as nitrogen plasma may be used as long as it can change metal titanium to a titanium compound (this change is oxidation in a broad sense, that is, an increase in the oxidation number of titanium). You may. Further, oxidation or nitridation of metallic titanium may be performed by using heat treatment. The heat treatment is not particularly limited, but may be performed using a furnace, a lamp annealing device, or the like.
[0024]
Thus, a titanium nitride film 80 containing no titanium is formed, and an alloy film 9 mainly containing aluminum and a titanium nitride film 10 are successively deposited again by the sputtering method (FIG. 1F). Note that, for example, an alloy of aluminum and copper can be used as the alloy film. Further, an aluminum film may be used instead of the alloy film 9. Further, the wiring is patterned using a lithography technique and a dry etching method (FIG. 1G).
[0025]
When the wiring is formed by the above method, the titanium generated by the target cleaning is oxidized by the oxygen plasma, and therefore does not alloy with the aluminum and titanium of the subsequently deposited alloy film 9. Therefore, no titanium-aluminum product is formed in the aluminum alloy near the boundary between the titanium nitride film and the alloy film. Thus, the stress migration caused by the titanium-aluminum product is suppressed, and the reliability of the semiconductor device can be improved.
[0026]
Here, the case where the metal buried in the contact hole 3 is tungsten by the CVD method has been described, but tungsten other than the tungsten such as copper or aluminum may be used by the sputtering method. Further, here, the case where the wiring is formed on the contact hole formed on the semiconductor substrate has been described, but the above-described process may be applied to the case where the wiring is formed on the via hole connecting the wiring layers. Good.
[0027]
(Embodiment 2)
First, in the same manner as in the first embodiment, a contact hole 3 is formed in an interlayer insulating film 2 formed on a semiconductor substrate 1, and then a barrier metal 4 and a tungsten plug 6 are buried in the contact hole 3 (FIG. a) to (d)). Further, a titanium film 7 and a titanium nitride film 8 are continuously formed, and the titanium target is subjected to sputtering cleaning.
[0028]
In this embodiment, cleaning with pure water 30 is applied as a treatment of the surface of the titanium nitride film 8 (FIG. 2E). By cleaning with pure water, titanium attached to the titanium nitride film during sputtering cleaning reacts with oxygen in water molecules. The temperature of the pure water is not particularly limited, but is preferably 25 ° C. or higher. Note that the liquid used for cleaning may be any liquid that does not excessively corrode the already formed interlayer insulating film or metal, and is not limited to pure water.
[0029]
Thereafter, in the same manner as in the first embodiment, an alloy film 9 and a titanium nitride film 10 are deposited on the processed titanium nitride film 80 (FIG. 2 (f)), and the wiring is patterned (FIG. 2 (f)). g)).
[0030]
(Embodiment 3)
Also in the present embodiment, first, as in the first embodiment, a contact hole 3 is formed in an interlayer insulating film 2 formed on a semiconductor substrate 1, and then a barrier metal 4 and a tungsten plug 6 are embedded in the contact hole 3. (FIGS. 3A to 3D). Further, a titanium film 7 and a titanium nitride film 8 are continuously formed, and the titanium target is subjected to sputtering cleaning (FIG. 3E).
[0031]
In this embodiment, dry etching 40 is applied as a treatment of the surface of the titanium nitride film 8 (FIG. 3F). By the dry etching, titanium attached to the titanium nitride film due to the sputter cleaning is removed. The time of the etching is adjusted so that the etching is stopped before the titanium film 7 under the titanium nitride film 8 is exposed.
[0032]
Thereafter, in the same manner as in the first embodiment, an alloy film 9 and a titanium nitride film 10 are deposited on the processed titanium nitride film 80 (FIG. 3 (g)), and wiring patterning is performed (FIG. 3 (g)). h)).
[0033]
The semiconductor device shown in FIG. 4 can be obtained by the steps described in the first to third embodiments. In this semiconductor device, since the aluminum alloy film 9 is deposited on the titanium nitride film 80 in a state where titanium does not remain as a metal, formation of a titanium-aluminum product in the patterned wiring is prevented. .
[0034]
The method of the present invention is particularly suitable for manufacturing using a sputtering apparatus in which a shutter is not arranged on a target which is a single wafer type, and is particularly suitable for continuous manufacturing of a plurality of semiconductor devices using the same apparatus. I have.
[0035]
【The invention's effect】
As described above, according to the manufacturing method of the present invention, it is possible to suppress an alloy reaction between aluminum and an unreacted titanium forming a migration path, and to prevent stress migration caused by a titanium-aluminum product. The utility of the present invention in the technical field is extremely high as to provide a semiconductor device with high performance and high reliability.
[Brief description of the drawings]
FIG. 1 is a process diagram showing an example of a manufacturing process of a semiconductor device of the present invention by a cross section of the device.
FIG. 2 is a process drawing showing another example of the manufacturing process of the semiconductor device of the present invention by a cross section of the same device.
FIG. 3 is a process drawing showing another example of the manufacturing process of the semiconductor device of the present invention by a cross section of the same device.
FIG. 4 is a sectional view showing an example of a semiconductor device manufactured according to the present invention.
FIG. 5 is a process diagram showing a manufacturing process of a conventional semiconductor device by a cross section of the device.
FIG. 6 is a cross-sectional view showing a semiconductor device manufactured by a conventional process.
[Explanation of symbols]
Reference Signs List 1 semiconductor substrate 2 interlayer insulating film 3 contact hole 4 barrier metal 5 tungsten film 6 tungsten plug 7 titanium film 8 titanium nitride film 9 aluminum alloy film 10 titanium nitride film 20 oxygen plasma treatment 30 cleaning with pure water 40 dry etching 80 (after treatment) ) Titanium nitride film 120 Titanium-aluminum product

Claims (5)

A step of sequentially depositing a titanium film and a titanium nitride film by a sputtering method on an insulating film formed on a semiconductor substrate; a step of sputtering cleaning a surface of a titanium target used for depositing the titanium nitride film; A step of oxidizing titanium attached to the surface of the titanium nitride film by cleaning, and a step of depositing a metal film containing aluminum as a main component on the titanium nitride film in which the attached titanium is oxidized. A method for manufacturing a semiconductor device. The method according to claim 1, wherein the step of oxidizing the titanium includes a plasma treatment using an oxidizing plasma. The step of oxidizing the titanium, the method of manufacturing a semiconductor device according to claim 1 comprising a thermal treatment in an oxidizing atmosphere. The method according to claim 3 , wherein the heat treatment is performed at a temperature of 100 ° C. or more and 500 ° C. or less. The method of manufacturing a semiconductor device according to claim 1, wherein the step of oxidizing the titanium includes, as a liquid contact process, cleaning with a liquid containing water, an acid, or an organic compound.

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