JP3252582B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device which is effective for filling a contact hole for electrically connecting a semiconductor substrate and a wiring with tungsten (W).

[0002]

2. Description of the Related Art In recent years, as semiconductor devices have been miniaturized and integrated, the diameter of a contact hole for electrically connecting a semiconductor substrate and a wiring has been miniaturized. Along with that
The aspect ratio is also increasing. Therefore, the step coverage of the conductive film such as aluminum (Al) in the contact hole is reduced, and the reliability of the wiring is reduced. Thus, it has become difficult to electrically connect the semiconductor substrate and the wiring.

Therefore, a method has been developed in which a W film having good step coverage is deposited and the contact hole is filled with tungsten (W), and then W is etched back to leave W in the contact hole to form a W plug. Have been.

Hereinafter, a conventional method for manufacturing a semiconductor device using W plug wiring will be described. FIG. 3 shows titanium (T
i) Description of film peeling, FIG. 4 shows a conventional method of manufacturing a semiconductor device by W plug wiring.

In FIG. 4, 1 is a semiconductor substrate, 2 is n ⁺
Diffusion layer, 3 is an interlayer insulating film, 4 is a contact hole, 5 is a Ti film, 6 is a titanium nitride (TiN) film, 7 is a W film, 8
Denotes an Al film, 9 denotes a TiN film, and 10 denotes a Ti film peeling.
Hereinafter, description will be made in the order of steps.

An n ⁺ diffusion layer 2 formed on a semiconductor substrate 1
In order to make an electrical connection to the substrate, the interlayer insulating film 3 is etched using a photoresist as a mask to form a contact hole 4 (FIG. 4A).

Next, a Ti film 5 serving as an adhesion layer and a Ti film
An N film 6 is deposited by a sputtering method. The step coverage of the sputtered film depends on the sputtering temperature. Therefore, in order to keep the step coverage of the sputtered film constant, it is necessary to keep the temperature of the semiconductor substrate 1 during sputtering constant. For this reason, the semiconductor substrate 1 is placed on the back surface by, for example, argon (Ar)
The semiconductor substrate 1 is heated by a gas, and the semiconductor substrate 1 is brought into close contact with a heater block from which an Ar gas is blown out by a clamp in order to maintain heat conduction between the semiconductor substrate 1 and the Ar gas. The Ti film 5 is formed by sputtering using a Ti target and Ar gas. A Ti target is used to form the TiN film 6, and reactive sputtering is performed using a mixed gas of an Ar gas and a nitrogen (N ₂ ) gas. At this time, the migration of Ti particles is larger than that of nitrogen ions,
i film 5 is formed to the outer peripheral portion of semiconductor substrate 1,
A Ti film 5 not covered with the TiN film 6 is formed (FIG. 4B).

Subsequently, by reducing tungsten hexafluoride (WF ₆ ) gas with silane (SiH ₄ ) gas or hydrogen (H ₂ ) gas, the W film 7 is reduced in thickness to a half or more of the contact diameter. accumulate. Thereby, the inside of the contact hole becomes W
(FIG. 4C).

Subsequently, the surface of the semiconductor substrate 1 is SF ₆
Etch back with gas to remove W film 7 outside contact hole
Is removed. At this time, the SF ₆ gas reacts with the Ti film 5 not covered with the TiN film 6 to form Ti fluoride. This reaction causes peeling of the Ti film 10 (FIGS. 3 and 4D).

Subsequently, the surface of the semiconductor substrate 1 is etched back to remove the W film 7 outside the contact hole.
Thereafter, an Al film 8 and a TiN film 9 are deposited and formed by a sputtering method, and then patterned to form a Ti film 5, a TiN film 6,
A wiring composed of the Al film 8 and the TiN film 9 is formed (FIG. 4E).

As described above, the wiring using the conventional W plug is formed.

[0012]

However, in the above-described conventional manufacturing method, there is a possibility that the Ti film peels off at the outer peripheral portion of the semiconductor substrate as shown in FIGS. 3 and 4 (d) and 4 (e). . When the peeled Ti film adheres again to the semiconductor substrate as particles, a short circuit occurs between the Al films, which causes a problem that the wiring yield is reduced.

The present invention solves the above-mentioned conventional problems, and can prevent the peeling off of the Ti film due to the reaction between the SF film gas, which is the etching gas for the W film, and the Ti film, thereby improving the wiring yield. A method for manufacturing a semiconductor device is provided.

[0014]

According to a method of manufacturing a semiconductor device of the present invention, a step of forming a first adhesion layer in a contact hole formed on a semiconductor substrate and a part of the first adhesion layer are provided. Forming a second adhesion layer thereon, nitriding another surface of the first adhesion layer not covered with the second adhesion layer, and forming a second adhesion layer on the first and second adhesion layers. And a step of selectively etching the tungsten to leave the tungsten only inside the contact hole.

The first and second adhesion layers are each composed of titanium and titanium nitride formed by a sputtering method.

In the step of nitriding the surface of the first adhesion layer, nitriding is performed by using a plasma containing nitrogen.

In the step of nitriding the surface of the first adhesion layer, heat treatment is performed at a temperature of 380 to 500 ° C. in a nitrogen atmosphere.

Further, a method of manufacturing a semiconductor device according to the present invention
A step of forming a titanium film in a contact hole formed on a semiconductor substrate, a step of forming a titanium nitride film on a part of the titanium film, and a step of forming a titanium film not covered with the titanium nitride film. Removing a portion, depositing tungsten on the titanium nitride film, and selectively etching the tungsten to leave the tungsten only inside the contact hole.

In the method of manufacturing a semiconductor device according to the present invention, the step of removing the titanium film is performed by dry etching using a gas containing fluorine or a fluorine compound.

The step of removing the titanium film in the method of manufacturing a semiconductor device according to the present invention is performed by wet etching using an aqueous solution containing fluorine or a fluorine compound.

[0021]

According to the present invention, when depositing a W film, the first adhesion layer Ti film not covered with the second adhesion layer TiN film has a TiN film formed on its surface by nitriding treatment, or Excess S due to removal by etching
The Ti film does not peel off due to the reaction with the F ₆ gas and the Ti film,
There is no problem that the wiring yield decreases.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a semiconductor device according to a first embodiment of the present invention will be described below with reference to the cross-sectional views of FIG.

Here, for simplicity of illustration, only the n ⁺ diffusion layer and the wiring process are shown. In the figure, 1 is a semiconductor substrate, 2 is an n ⁺ diffusion layer, 3 is an interlayer insulating film, 4 is a contact hole, 5 is a Ti film, 6 is a TiN film, 7 is a W film,
8 is an Al film, 9 is a TiN film, and 11 is a TiN film.

First, in order to electrically connect to the n ⁺ diffusion layer 2 formed on the semiconductor substrate 1, the interlayer insulating film 3
Then, a contact hole is formed (FIG. 1A).

Next, a Ti film 5 having a thickness of 600.degree.
A TiN film 6 of 00 ° is deposited by a sputtering method. Ti
A Ti target is used to form the film 5 and sputtering is performed using Ar gas. A Ti target is used to form the TiN film 6 and reactive sputtering is performed using a mixed gas of Ar and N ₂ . At this time, since the migration of the Ti particles is larger than that of the nitrogen ions, the Ti film 5 is formed to the outer peripheral portion of the semiconductor substrate 1 rather than the TiN film 6, and the Ti film 5 is formed of TiN at the edge of the semiconductor substrate 1. It is formed to the outside of the film 6 and is exposed (FIG. 1B).

Therefore, in an ammonia (NH ₃ ) atmosphere,
Heat treatment is performed at 50 ° C. for 30 minutes. As a result, the Ti film 5 exposed at the edge of the semiconductor substrate 1 is nitrided,
This becomes the N film 11. Therefore, the entire surface of the semiconductor substrate 1 is finally covered with the TiN film (FIG. 1).
(C)).

The same effect can be obtained even if this heat treatment is performed in an N ₂ atmosphere. However, this heat treatment is 500
The heat treatment is desirably performed at a temperature of 500 ° C. or less. If the heat treatment is performed at a temperature of 500 ° C. or more, the nitride film is sharply nitrided. Is generated and causes particles. Further, by performing the heat treatment at a temperature of 500 ° C. or less, it can be used in the process after the formation of the Al wiring. But 3
If the temperature is lower than 80 ° C., the nitridation rate is extremely slow, which is not practical.

Subsequently, the temperature was 450 ° C. and the pressure was 80 Torr.
The WF ₆ gas is reduced with SiH ₄ gas or H ₂ gas by the CVD method to deposit the W film 7 to a thickness of １ ／ or more of the contact diameter, and fill the contact hole with W (FIG. 1).
(D)).

Subsequently, the W film outside the contact hole is etched back using an SF ₆ -Ar-based gas at an RF power of 100 to 400 W and a pressure of 100 to 200 mTorr. After the W film is removed, since the Ti film 5 is entirely covered with TiN film 6, without direct contact with SF ₆ gas, the reaction of the Ti film 5 and SF ₆ gas does not occur. Therefore, peeling of the Ti film does not occur at the outer peripheral portion of the semiconductor substrate 1. Next, an Al film 8 having a thickness of 9000 ° and a thickness 3
A TiN film 9 of 00 ° is formed by a sputtering method, and is patterned to form a wiring (FIGS. 1E and 1F).

According to the method of this embodiment, the Ti film 5 is formed outside the TiN film 6 by sputtering.
Since the surface is covered by the N film 11, no reaction occurs between the Ti film 5 and the SF ₆ gas in the W etch back process. Therefore, particles generated by peeling of the Ti film at the outer peripheral portion of the semiconductor substrate 1 can be reduced.

Next, a method of manufacturing a semiconductor device according to a second embodiment of the present invention will be described with reference to the cross-sectional views in the order of steps shown in FIG.

First, in order to electrically connect to the n ⁺ diffusion layer 2 formed on the semiconductor substrate 1, the interlayer insulating film 3
Then, a contact hole is formed (FIG. 1A).

Next, a Ti film 5 having a thickness of 600.degree.
A TiN film 6 of 00 ° is deposited by a sputtering method. Ti
The film 5 is formed by sputtering with an Ar gas using a Ti target, and the TiN film 6 is formed by reactive sputtering with a mixed gas of Ar and N ₂ using a Ti target. At this time, since the migration of the Ti particles is larger than that of the nitrogen ions, the Ti film 5 is formed to the outer peripheral portion of the semiconductor substrate 1 rather than the TiN film 6, and the Ti film 5 is formed of TiN at the edge of the semiconductor substrate 1. It is formed to the outside of the film 6 and is exposed (FIG. 1B).

Then, high-frequency plasma processing is performed in an NH ₃ atmosphere at a power of 400 W, a pressure of 5.0 Torr, a NH ₃ flow rate of 200 sccm, and a substrate temperature of 400 ° C. for 60 seconds. As a result, the Ti film 5 exposed at the edge of the semiconductor substrate 1 is nitrided to form a TiN film 11. Therefore, FIG.
In (c), the entire surface of the semiconductor substrate 1 is finally covered with the TiN film. In this high-frequency plasma treatment, the same effect can be obtained by using N ₂ instead of NH ₃ .

Subsequently, a temperature of 450 ° C. and a pressure of 80 Torr
The WF ₆ gas is reduced with SiH ₄ gas or H ₂ gas by the CVD method to deposit the W film 7 to have a thickness equal to or more than の of the contact diameter, and fill the contact hole with W (FIG. 1).
(D)).

Subsequently, the W film outside the contact hole is etched back with an RF power of 100 to 400 W and a pressure of 100 to 200 mTorr using an SF ₆ -Ar-based gas. After the W film is removed, since the Ti film 5 is entirely covered with TiN film 6, without direct contact with SF ₆ gas, the reaction of the Ti film 5 and SF ₆ gas does not occur. Therefore, peeling of the Ti film does not occur at the outer peripheral portion of the semiconductor substrate 1. Next, an Al film 8 having a thickness of 9000 ° and a thickness of 30
A 0 ° TiN film 9 is formed by sputtering and patterned to form wiring (FIGS. 1E and 1F).

According to the method of this embodiment, the Ti film 5 is formed outside the TiN film 6 by sputtering.
Since the surface is covered by the N film 11, no reaction occurs between the Ti film 5 and the SF ₆ gas in the W etch back process. Therefore, particles generated by peeling of the Ti film at the outer peripheral portion of the semiconductor substrate 1 can be reduced.

Next, a method of manufacturing a semiconductor device according to a third embodiment of the present invention will be described with reference to the cross-sectional views in the order of steps shown in FIG.

First, in order to establish electrical connection to the n ⁺ diffusion layer 2 formed on the semiconductor substrate 1, an interlayer insulating film 3 is formed.
Then, a contact hole is formed (FIG. 1A).

Next, a Ti film 5 having a thickness of 600.degree.
A TiN film 6 of 00 ° is deposited by a sputtering method. Ti
A Ti target is used to form the film 5 and sputtering is performed using Ar gas. A Ti target is used to form the TiN film 6 and reactive sputtering is performed using a mixed gas of Ar and N ₂ . At this time, since the migration of the Ti particles is larger than that of the nitrogen ions, the Ti film 5 is formed to the outer peripheral portion of the semiconductor substrate 1 rather than the TiN film 6, and the Ti film 5 is formed of TiN at the edge of the semiconductor substrate 1. It is formed to the outside of the film 6 and is exposed (FIG. 1B).

Then, using nitric acid (HNO ₃ ) at room temperature
The Ti film 5 is nitrided for 0 second to form a TiN film 11. Therefore, finally, the entire surface of the semiconductor substrate 1 becomes Ti
It will be covered with the N film (FIG. 1C).

Subsequently, a temperature of 450 ° C. and a pressure of 80 Torr
The WF ₆ gas is reduced with SiH ₄ gas or H ₂ gas by the CVD method to deposit the W film 7 to have a thickness equal to or more than の of the contact diameter, and fill the contact hole with W (FIG. 1).
(D)).

Subsequently, the W film outside the contact hole is etched back with an RF power of 100 to 400 W and a pressure of 100 to 200 mTorr using SF ₆ -Ar based gas. After the removal of the W film, the Ti film 5 is entirely covered with the TiN film 6, so that the Ti film 5 does not come into direct contact with the SF ₆ gas, and no reaction occurs between the Ti film 5 and the W etching gas SF ₆ . Therefore, peeling of the Ti film does not occur at the outer peripheral portion of the semiconductor substrate 1. Next, a 9000 mm thick Al film 8 and a 300 nm thick TiN film 9 are formed by sputtering.
Form wiring by patterning (FIG. 1 (e),
(F)).

According to the method of this embodiment, the Ti film 5 is formed outside the TiN film 6 by sputtering.
Since the surface is covered by the N film 11, no reaction occurs between the Ti film 5 and the SF ₆ gas in the W etch back process. Therefore, particles generated by peeling of the Ti film at the outer peripheral portion of the semiconductor substrate 1 can be reduced.

Hereinafter, a method of manufacturing a semiconductor device according to a fourth embodiment of the present invention will be described with reference to the cross-sectional views shown in FIG.

Here, for simplicity of illustration, only the n ⁺ diffusion layer and the wiring process are shown. In the figure, 1 is a semiconductor substrate, 2 is an n ⁺ diffusion layer, 3 is an interlayer insulating film, 4 is a contact hole, 5 is a Ti film, 6 is a TiN film, 7 is a W film,
8 is an Al film, 9 is a TiN film, and 11 is a TiN film.

First, in order to electrically connect to the n ⁺ diffusion layer 2 formed on the semiconductor substrate 1, the interlayer insulating film 3
Then, a contact hole is formed (FIG. 2A).

Next, a Ti film 5 having a thickness of 600.degree.
A TiN film 6 of 00 ° is deposited by a sputtering method. Ti
A Ti target is used to form the film 5 and sputtering is performed using Ar gas. A Ti target is used to form the TiN film 6 and reactive sputtering is performed using a mixed gas of Ar and N ₂ . At this time, since the migration of the Ti particles is larger than that of the nitrogen ions, the Ti film 5 is formed to the outer peripheral portion of the semiconductor substrate 1 rather than the TiN film 6, and the Ti film 5 is formed of TiN at the edge of the semiconductor substrate 1. It is formed to the outside of the film 6 and is exposed (FIG. 2B).

Therefore, the entire surface of the semiconductor substrate 1 is dry-etched by high-frequency plasma using SF ₆ gas capable of selectively etching the Ti film 5. As a result, the Ti film 5 exposed on the surface of the semiconductor substrate 1 is removed, and FIG.
As shown by a region 17 in FIG. 2C, the edge of the TiN film 6 and the edge of the Ti film 5 are aligned (FIG. 2C).

Subsequently, a temperature of 450 ° C. and a pressure of 80 Torr
The WF ₆ gas is reduced with SiH ₄ gas or H ₂ gas by the CVD method to deposit the W film 7 to a film thickness equal to or more than の of the contact diameter, and fill the contact hole with W (FIG. 2).
(D)).

Subsequently, the W film outside the contact hole is etched back with an RF power of 100 to 400 W and a pressure of 100 to 200 mTorr using SF ₆ -Ar based gas. Even after the W film is removed, the Ti film 5 and Ti
Since the edges of the N film 6 are aligned, the Ti film 5 is SF ₆
There is no direct contact with the gas, and no reaction occurs between the Ti film 5 and the SF ₆ gas. Therefore, T
No i-film peeling occurs. Next, an Al film 8 having a thickness of 9000 mm and a TiN film 9 having a thickness of 300 mm are formed by a sputtering method and patterned to form wirings (FIG. 2E,
(F)).

According to the manufacturing method of this embodiment, even if the Ti film 5 is formed outside the TiN film 6, the Ti film formed outside is removed by dry etching in advance, so that the W etching is performed. No reaction occurs between the Ti film 5 and the W etching gas SF _{6 in the} back step. Therefore,
Particles generated at the outer peripheral portion of the semiconductor substrate 1 due to peeling of the Ti film can be reduced.

Hereinafter, a method of manufacturing a semiconductor device according to a fifth embodiment of the present invention will be described with reference to FIGS.

First, in order to establish electrical connection to n ⁺ diffusion layer 2 formed on semiconductor substrate 1, interlayer insulating film 3 is formed.
Then, a contact hole is formed (FIG. 2A).

Next, a Ti film 5 having a thickness of 600.degree.
A TiN film 6 of 00 ° is deposited by a sputtering method. Ti
The film 5 uses a Ti target and sputters only Ar gas. The TiN film 6 is formed using a Ti target and reactive sputtering is performed using a mixed gas of Ar and N ₂ .
At this time, since the migration of the Ti particles is larger than that of the nitrogen ions, the Ti film 5 is formed to the outer peripheral portion of the semiconductor substrate 1 rather than the TiN film 6, and the Ti film 5 is formed of TiN at the edge of the semiconductor substrate 1. It is formed to the outside of the film 6 and is exposed (FIG. 2B).

Therefore, buffered hydrofluoric acid (HF: NH ₄ F =
1: 5), the Ti film 5 is selectively wet-etched. Since the Ti film 5 has a higher etching rate for buffered hydrofluoric acid than the TiN film 6, the Ti film 5 can be removed while the TiN film 6 remains on the semiconductor substrate 1. As a result, the Ti film 5 exposed on the surface of the semiconductor substrate 1
Is removed, and as shown by a region 17 in FIG.
The edge of the N film 6 is aligned with the edge of the Ti film 5 (FIG. 2).
(C)).

Subsequently, the temperature was 450 ° C. and the pressure was 80 Torr.
The WF ₆ gas is reduced with SiH ₄ gas or H ₂ gas by the CVD method to deposit the W film 7 to a film thickness equal to or more than の of the contact diameter, and fill the contact hole with W (FIG. 2).
(D)).

Subsequently, the W film outside the contact hole is etched back with an RF power of 100 to 400 W and a pressure of 100 to 200 mTorr using SF ₆ -Ar based gas. Thereafter, an Al film 8 having a thickness of 9000 mm and a TiN film 9 having a thickness of 300 mm are formed by a sputtering method and patterned to form wirings (FIGS. 2E and 2F).

According to the manufacturing method of this embodiment, even if the Ti film 5 is formed outside the TiN film 6, the Ti film formed outside is removed by wet etching in advance, so that the W etching is performed. No reaction occurs between the Ti film 5 and the W etching gas SF _{6 in the} back step. Therefore, particles generated due to peeling of the Ti film at the outer peripheral portion of the semiconductor substrate 1 can be reduced.

[0060]

As described above, according to the present invention, when a W plug is formed, after the Ti film and the TiN film are formed, the Ti film exposed at the edge of the semiconductor substrate and not covered is nitrided or removed. Is what you do. This makes it possible to prevent the Ti film from reacting with the SF6 gas, which is an etching gas for the W film, when the W film is etched back, thereby suppressing the peeling of the Ti film at the outer peripheral portion of the semiconductor substrate, and the peeling of the Yi film. Particles generated due to the above can be reduced.

[Brief description of the drawings]

FIG. 1 shows a first to a first methods of manufacturing a semiconductor device according to the present invention.
Step-by-step sectional view of the third embodiment

FIG. 2 is a sectional view in the order of steps of a fourth and fifth embodiments of a method of manufacturing a semiconductor device according to the present invention.

FIG. 3 is a diagram for explaining peeling of a Ti film;

FIG. 4 is a cross-sectional view in the order of steps in a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

Reference Signs List 1 semiconductor substrate 2 n ⁺ diffusion layer 3 interlayer insulating film 4 contact hole 5 Ti film 6 TiN film 7 W film 8 Al film 9 TiN film 10 Peeling of Ti film 11 TiN film 12 clamp ring

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-196421 (JP, A) JP-A-5-13368 (JP, A) JP-A-7-161662 (JP, A) JP-A-7-161 94448 (JP, A) JP-A-6-244288 (JP, A) JP-A-5-94990 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/285 301 H01L 21/768

Claims (8)

(57) [Claims] A step of forming a first adhesion layer in a contact hole formed in a peripheral portion of the semiconductor substrate; and forming a second adhesion layer on a part of the first adhesion layer. A step of nitriding another surface of the first adhesion layer that is not covered with the second adhesion layer; a step of depositing tungsten on the first and second adhesion layers; Selectively etching to leave the tungsten only inside the contact hole. 2. The method of manufacturing a semiconductor device according to claim 1, further comprising a step of forming the first adhesion layer by a titanium sputtering method and a step of forming a second adhesion layer by a titanium nitride sputtering method. A step of forming a titanium film in a contact hole formed in a peripheral portion of the semiconductor substrate; a step of forming a titanium nitride film on a part of the titanium film; Nitriding the other surface of the titanium film which is not covered; depositing tungsten on the titanium film and the titanium nitride film; selectively etching the tungsten to only inside the contact hole. A method of manufacturing a semiconductor device, comprising: a step of leaving the tungsten. 4. The method for manufacturing a semiconductor device according to claim 3, wherein SF6 is used as the etching gas for tungsten. 5. The method according to claim 3, wherein the step of nitriding the other surface of the titanium film is a heat treatment in an ammonia atmosphere, and the heat treatment temperature is in a range of 380 ° C. to 500 ° C. . 6. A step of forming a titanium film in a contact hole formed in a peripheral portion of a semiconductor substrate; a step of forming a titanium nitride film on a part of the titanium film; Removing the remaining portion of the titanium film that has not been removed, depositing tungsten on the titanium nitride film, and selectively etching the tungsten to leave the tungsten only inside the contact hole. A method for manufacturing a semiconductor device comprising: 7. The method according to claim 6, wherein the step of removing the titanium film is performed by dry etching using a gas containing fluorine or a fluorine compound. 8. The method according to claim 6, wherein the step of removing the titanium film is performed by wet etching using an aqueous solution containing fluorine or a fluorine compound.