JPH0969519A - Semiconductor device and fabrication thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method for fabricating a semiconductor device in which the reflectance of an antireflection film can be controlled using a same material depending on the wavelength of light source in a stepper by forming an aluminum oxide layer containing a transition metal or a metal nitride on the surface of interconnection. SOLUTION: A semiconductor element, e.g. an MOS transistor, is formed on the surface of a silicon substrate 1 and an interlayer insulation film 2 is formed thereon. Furthermore, an interconnection 3 of aluminum copper alloy is formed on the interlayer insulation film 2 followed by formation of an alumina antireflection film 4. The alumina antireflection film 4 contains a deposit of transition metal or aluminum nitride for decreasing the reflectance of the alumina antireflection film 4 effectively. Implantation energy, dose or the thickness of alumina layer can be regulated easily in the ion implantation for adding these elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device having wiring such as aluminum and a method for manufacturing the same, and more particularly to a structure of an antireflection film on the wiring and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, as the density of semiconductor integrated circuits has increased, the width of electrode wiring made of a metal film such as an aluminum alloy has been further miniaturized. Therefore, exposure by ultraviolet rays is often used in the photolithography process. At this time, if the metal film surface having an extremely large reflectance is used as it is, the pattern shape abnormality of the photoresist may occur due to the reflection on the metal film surface.
In order to prevent such reflection, a method of depositing various antireflection films on the surface of the metal film has been attempted.

Recently, as proposed in Japanese Patent Publication No. 6-52702, a titanium nitride film has been used as an antireflection film on an aluminum metal thin film. The main reason is
G-line (wavelength 4) emitted from the mercury lamp used for exposure
(36 nm) or i-line (wavelength 365 nm) has a high absorptivity, and a film having a thickness of about 100 nm has a sufficient antireflection function.

Hereinafter, such a conventional technique will be described with reference to FIG.
It will be described based on. FIG. 5 is a sectional view in the order of manufacturing steps for explaining the conventional technique.

On the surface of the silicon substrate 21, usually MO
A semiconductor element such as an S transistor is formed (not shown). Then, as shown in FIG. 5A, the interlayer insulating film 2 having a thickness of about 500 nm is a silicon oxide film deposited on the silicon substrate 21 by the chemical vapor deposition (CVD) method.
2 is formed. Then, an aluminum-copper alloy film 23 having a film thickness of 1 μm is formed on the interlayer insulating film 22 by the sputtering method.

Next, as shown in FIG.
A titanium nitride film 24 of nm thickness is deposited on the aluminum-copper alloy film 23 by sputtering. Then, as shown in FIG. 5C, a resist mask 25 having a wiring pattern is formed by the photolithography technique by the reduction projection exposure apparatus (stepper) using the above-mentioned i-line. In this case, the titanium nitride film 24 has a high i-line absorptivity and a reflectance of about 20%, and a wiring pattern having a line width of 0.5 μm is formed.

However, with further miniaturization in recent years, it is becoming impossible to resolve with i-line. For miniaturization in the future, it is essential to shorten the wavelength of exposure light for exposure used for exposing the photosensitive resist film. Therefore, a KrF excimer laser beam with a wavelength of 248 nm or a wavelength of 19
Steppers using a 3 nm ArF excimer laser beam have been developed as next-generation steppers. As the irradiation light source for photosensitivity changes day by day in this way, the antireflection film which has been conventionally used is no longer sufficient in terms of absorption wavelength region and reflectance. In addition, the raw material of the photoresist is different from that of the conventional one as the irradiation light source for photosensitivity is changed.

[0008]

The miniaturization and densification of semiconductor elements are being energetically advanced at present, and the wiring width of metal used for multilayer wiring is 0.35 μm to 0.2 μm.
It is getting finer with m.

When the wiring width is narrowed in this way, as described above, the irradiation light for exposure of the stepper has a shorter wavelength and excimer laser light is used. However, the wavelength of the irradiation light for exposure is 30
When the thickness is 0 nm or less, the reflectance of the titanium nitride film used as the conventional antireflection film increases, so that the function as the antireflection film is significantly reduced. Then, since the phases of such excimer laser light are aligned, the reflectance thereof further increases.

Further, when the titanium nitride film thickness is used as an antireflection film in such a short wavelength region, the film thickness must be increased. Then, it is difficult to reduce the resistance of the fine wiring. This is because the electric resistance of the titanium nitride film is about 10 times that of the aluminum-copper alloy.

Further, this titanium nitride film has a problem in adhesion to the above-mentioned photosensitive resist film for excimer laser light, and it is difficult to form a fine pattern.

An object of the present invention is to solve the above problems and to provide a method capable of controlling the reflectance of an antireflection film with the same material according to the wavelength of the irradiation light source of the stepper.

[0013]

Therefore, in the semiconductor device of the present invention, the wiring formed on the surface of the interlayer insulating film on the semiconductor substrate contains an aluminum oxide layer containing a transition metal or a metal nitride. An aluminum oxide layer is formed on the surface of the wiring.

Here, chromium is used as the transition metal. Aluminum nitride is used as the metal nitride.

Further, a method of manufacturing a semiconductor device according to the present invention
In the step of forming aluminum metal wiring on the surface of the interlayer insulating film on the semiconductor substrate, the step of depositing an aluminum metal thin film on the interlayer insulating film and the step of oxidizing the surface of the aluminum metal thin film to form an aluminum oxide layer. A step, after forming the aluminum oxide layer, ion-implanting a transition metal into the aluminum oxide layer, and forming a resist pattern for the wiring on the surface of the ion-implanted aluminum oxide layer of the transition metal, including.

Alternatively, in the method of manufacturing a semiconductor device according to the present invention, in the step of forming the wiring of aluminum metal described above, a step of depositing an aluminum metal thin film on the interlayer insulating film, and nitrogen on the surface of the aluminum metal thin film. A step of ion-implanting ions, a step of converting the surface of the aluminum ion thin film into which nitrogen ions are injected into an aluminum oxide layer by anodic oxidation in a chemical solution, and a resist for wiring on the surface of the aluminum oxide layer Forming a pattern.

In the present invention, the surface of a metal film used as a wiring is oxidized and the obtained aluminum oxide film (alumina film) is ion-implanted with a transition metal element and used as an antireflection film. According to this method, by changing the parameters such as the film thickness of the aluminum oxide film, the type of implantation element, the implantation amount, and the implantation energy, the absorption wavelength region and reflection that are optimal for the wavelength of the irradiation light source used in the stepper It is possible to get a rate. This is because the injected transition metal element forms a color center or a precipitation layer as an intermetallic compound, where light absorption and scattering occur.

Further, an element such as nitrogen or carbon that forms a compound with aluminum is ion-implanted into the surface layer of the metal film used as wiring, and then the surface of the metal film is oxidized to obtain an antireflection film having the same effect. To be This is because the injected element forms an intermetallic compound with aluminum or an island-shaped compound, and these compounds cause absorption and scattering of light.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a semiconductor device having wirings containing aluminum metal according to the present invention.

Semiconductor elements such as MOS transistors are formed on the surface of the silicon substrate 1 (not shown). Then, as shown in FIG. 1, an interlayer insulating film 2 is formed on the silicon substrate 1. Here, the interlayer insulating film 2 is a silicon oxide film having a film thickness of about 500 nm. The interlayer insulating film 2 is formed by first depositing a silicon oxide film having a film thickness of about 1000 nm by a CVD method and flattening the deposited silicon oxide film by a chemical mechanical polishing (CMP) method.

Then, an aluminum alloy wiring 3 made of an aluminum copper alloy is formed on the interlayer insulating film 2. Here, the line width of the aluminum alloy wiring 3 is 0.35 μm or less, and the height thereof is set to 0.5 μm or more. Further, an alumina antireflection film 4 is formed on the aluminum alloy wiring 3. Here, the film thickness of the alumina antireflection film 4 is 50 n.
It is set to about m or less. Further, the alumina antireflection film 4 contains a deposit such as a transition metal or aluminum nitride that effectively reduces the reflectance. As described above, the semiconductor device of the present invention is formed.

Next, the manufacturing method of the present invention will be described with reference to FIGS. 2A to 2D are cross-sectional views in the order of manufacturing steps for explaining the first embodiment of the present invention. 3A to 3D are cross-sectional views in the order of manufacturing steps for explaining the second embodiment of the present invention.

As shown in FIG. 2A, the silicon substrate 1
A semiconductor element such as a MOS transistor is formed thereon (not shown). Next, the interlayer insulating film 2 having a film thickness of about 500 nm is formed of a silicon oxide film. Here, the method of forming this interlayer insulating film 2 is the same as that described in FIG.

Next, the aluminum alloy thin film 5 is deposited on the interlayer insulating film 2 by the sputtering method. Here, the aluminum alloy thin film 5 is a metal thin film containing 0.5 atomic% of copper in aluminum, and the film thickness thereof is set to about 1 μm.
Although not shown, the aluminum alloy thin film 5 is electrically connected to the diffusion layer formed on the surface of the silicon substrate 1 through a contact hole provided in a predetermined region of the interlayer insulating film 2. .

Next, as shown in FIG. 2B, an alumina thin film 6 is formed on the aluminum alloy thin film 5. Here, the film thickness of the alumina thin film 6 is set to about 50 nm. The method of forming the alumina thin film 6 is anodic oxidation of the surface of the aluminum alloy thin film 5. That is, a mixed chemical solution of 50 g / liter of ammonia borate and 30 g / liter of ammonium citrate is used as an electrolytic solution, and an electrochemical reaction in the electrolytic solution causes 10
A positive voltage of about 0V is applied. In this way, a dense alumina film having a film thickness of about 50 nm is formed.

As a method of forming the alumina thin film 6, other than this, surface oxidation of the aluminum alloy thin film 5 at an oxidation temperature of about 400 ° C. in oxygen plasma is also possible.

Next, as shown in FIG. 2C, chromium ions 7 are ion-implanted into the alumina thin film 6 to form a chromium-containing alumina thin film 8. Here, the implantation energy of chromium ions is 80 keV, and the dose amount is 1 ×.
It is set to 10 ¹⁶ ions / cm ² .

Next, as shown in FIG. 2D, a resist mask 8 having a wiring pattern is formed by a photolithography technique using a stepper that uses a KrF excimer laser beam as irradiation light for exposure. In this case, the chromium-containing alumina thin film 8 has a high absorptance of irradiation light and a reflectance of about 10%. Then, a wiring pattern having a line width of 0.25 μm is easily formed.

In the subsequent steps, using the resist mask 9 as an etching mask, the chromium-containing alumina thin film 8 and the aluminum alloy thin film 5 are sequentially dry-etched.
The aluminum alloy wiring 3 and the alumina antireflection film 4 described above are formed.

Next, a second embodiment will be described with reference to FIG. As shown in FIG. 3A, semiconductor elements such as MOS transistors are formed (not shown) on the silicon substrate 1 as in the first embodiment. Next, the film thickness is 500
The interlayer insulating film 2 having a thickness of about nm is formed of a silicon oxide film. Then, the aluminum alloy thin film 5 is deposited on the interlayer insulating film 2 by the sputtering method. Here, the film thickness of the aluminum alloy thin film 5 is about 1 μm. Further, this aluminum alloy thin film 5 is electrically connected to the diffusion layer formed on the surface of the silicon substrate 1 through the contact hole provided in the predetermined region of the interlayer insulating film 2 as in the first embodiment. I shall.

Next, as shown in FIG. 3B, nitrogen ions 10 are ion-implanted into the surface of the aluminum alloy thin film 5.
Here, the ion implantation energy is set to about 100 keV, and the dose amount is adjusted to be about 5 × 10 ¹⁷ ions / cm ² .

Next, the surface of the aluminum alloy thin film 5 implanted with nitrogen ions is anodized. The conditions for this anodic oxidation are the same as in the case of the first embodiment. That is, a mixed chemical solution of 50 g / liter of ammonia borate and 30 g / liter of ammonium citrate is used as an electrolytic solution, and a positive voltage of about 150 V is applied to the silicon substrate 1 by an electrochemical reaction in the electrolytic solution. Is applied. In this way, a dense alumina film having a film thickness of about 50 nm is formed.

The alumina thin film thus formed contains aluminum nitride formed by the above-mentioned nitrogen ion implantation. Then, the aluminum nitride-containing alumina thin film 11 as shown in FIG. 3C is formed. Here, the structure of aluminum nitride in the alumina thin film has an island shape isolated from each other.

Next, as shown in FIG. 3D, a resist mask 9 having a wiring pattern is formed by a photolithography technique using a stepper that uses i-line as irradiation light for exposure. In this case, the aluminum nitride-containing alumina thin film 11 has a high irradiation light absorptance and a reflectance of 1 or less.
It becomes about 0%, and a wiring pattern having a line width of 0.35 μm can be easily formed.

After that, similarly to the first embodiment, the aluminum nitride-containing alumina thin film 11 and the aluminum alloy thin film 5 were sequentially dry-etched using the resist mask 9 as an etching mask, which was described with reference to FIG. The aluminum alloy wiring 3 and the alumina antireflection film 4 are formed.

In the above embodiments, the case where the wiring is formed of an aluminum alloy thin film has been described. Here, it should be noted that the same is true when an aluminum metal thin film is used instead of the aluminum alloy thin film. It should be noted that this wiring can be made of a metal other than aluminum, for example, a refractory metal such as copper or tungsten. However, in this case, the alumina thin film must be deposited on these metal films by the CVD method or the like.

Next, the effect of the embodiment of the present invention will be described with reference to FIG. FIG. 4 shows the relationship between the reflectance and the irradiation light wavelength of various alumina thin films used in the present invention. Here, the alumina thin film has a thickness of 50 nm and is formed on the aluminum-copper alloy thin film.

As shown in FIG. 4, the reflectance is generally reduced in the chromium-containing alumina thin film and the aluminum nitride-containing alumina thin film as compared with the alumina thin film containing nothing. In the case of a chromium-containing alumina thin film, its reflectance monotonically decreases as the wavelength of the irradiation light becomes shorter. For example, when the irradiation light is a KrF excimer laser or an ArF excimer laser, the reflectance is 10
%. On the other hand, in the case of a titanium nitride thin film which is a conventional technique, the reflectance is 20 to 40% in the KrF or ArF excimer laser light region.
However, this is the case where the film thickness of the titanium nitride thin film is 50 nm.

In the case of the aluminum nitride-containing alumina thin film, the reflectance thereof becomes the minimum in the wavelength range of irradiation light of 300 to 400 nm. For example, when the irradiation light is i-line, the reflectance is about 10%. Here, the reflectance of the chromium-containing alumina thin film is 15 to 20%,
Since the reflectance of the titanium nitride thin film is about 30%, it is understood that the aluminum nitride-containing alumina thin film is optimal in this irradiation light wavelength region.

As described above, the reflectance of the alumina thin film used for antireflection of the present invention is greatly reduced to 1/2 to 1/4 of that of the titanium nitride thin film when the film thickness is the same.
A resist mask for fine wiring can be easily formed.

In the present invention, a transition metal other than chromium or carbon, which is contained in the alumina thin film, produces the same effect. In this way, the alumina thin film, which is the base material, is fixed, and the absorption wavelength region and reflectance can be greatly changed by changing the elements to be contained, and further, the ion implantation energy to be contained, the dose amount, and the film thickness of the alumina thin film. It is also possible to slightly change the reflectance by changing the. The surface of the alumina thin film that has been subjected to such a treatment is easily adjusted so as to be optimal for the stepper light source.
As shown in (d), after the photoresist is applied, highly accurate exposure and development can be performed, and the dimension control of the resist mask becomes easy.

[0042]

As described above, an alumina thin film containing a transition metal or aluminum nitride is used for the antireflection film according to the present invention. And the implantation energy in the ion implantation for containing these elements,
The dose amount or the film thickness of the alumina thin film can be easily adjusted.

According to the present invention, since the reflectance of the antireflection film can be easily adjusted even if the irradiation light in the photolithography process has a shorter wavelength, the fine wiring pattern can be easily formed. . Furthermore, since the thickness of the antireflection film can be set to be thin, it is easy to reduce the resistance of fine wiring.

Further, since the material matrix of the antireflection film is an alumina thin film, the manufacturing method can be uniformly unified even when the irradiation light wavelength of the stepper changes in the photolithography process, and the wiring manufacturing process is simple. become.

Further, the alumina thin film which is the base material of the antireflection film can be used as an etching mask in the dry etching of the aluminum alloy thin film. Therefore, it is possible to dry-etch the aluminum alloy thin film by forming the resist mask to be thin and using the alumina thin film and the thin resist mask as etching masks. By doing so, it becomes possible to form finer aluminum alloy wiring.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a semiconductor device for explaining the present invention.

FIG. 2 is a cross-sectional view in the order of manufacturing steps for explaining the first embodiment of the present invention.

FIG. 3 is a cross-sectional view in the order of manufacturing steps for explaining a second embodiment of the present invention.

FIG. 4 is a graph showing the reflectance of irradiation light for explaining the effect of the present invention.

5A to 5D are cross-sectional views in order of processes for explaining the conventional technique.

[Explanation of symbols]

 1, 21 Silicon substrate 2, 22 Interlayer insulating film 3 Aluminum alloy wiring 4 Alumina antireflection film 5 Aluminum alloy thin film 6 Alumina thin film 7 Chromium ion 8 Chromium-containing alumina thin film 9,25 Resist mask 10 Nitrogen ion 11 Aluminum nitride-containing alumina thin film 23 Aluminum copper alloy film 24 Titanium nitride film

Claims (5)

[Claims] 1. A wiring formed on a surface of an interlayer insulating film on a semiconductor substrate, wherein an aluminum oxide layer containing a transition metal or an aluminum oxide layer containing a metal nitride is formed on a surface portion of the wiring. A semiconductor device characterized in that 2. The semiconductor device according to claim 1, wherein the transition metal is chromium. 3. The semiconductor device according to claim 1, wherein the metal nitride is aluminum nitride. 4. A step of depositing an aluminum metal thin film on the interlayer insulating film in the step of forming an aluminum metal wiring on the surface of the interlayer insulating film on a semiconductor substrate, and a step of oxidizing and oxidizing the surface of the aluminum metal thin film. A step of forming an aluminum layer, a step of ion-implanting a transition metal into the aluminum oxide layer after forming the aluminum oxide layer, and a resist pattern for the wiring on the surface of the aluminum oxide layer ion-implanted with the transition metal And a step of forming a semiconductor device. 5. A step of depositing an aluminum metal thin film on the interlayer insulating film in the step of forming an aluminum metal wiring on the surface of the interlayer insulating film on a semiconductor substrate, and nitrogen ions on the surface of the aluminum metal thin film. A step of implanting ions, a step of converting the surface of the aluminum metal thin film into which the nitrogen ions are implanted into an aluminum oxide layer by anodic oxidation in a chemical solution, and a step of forming a resist pattern for the wiring on the surface of the aluminum oxide layer. And a step of forming the semiconductor device.