JPH1126461A - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate peeling-off of wiring without raising resistivity of a copper film by forming a titanium nitride of specified nitrogen concentration between the peripheral surface of a copper or copper alloy interconnection and an insulating film. SOLUTION: An insulating film 200 is formed on a silicon substrate 100. Then a tungsten plug 300 is packed in an opening part. Then by a sputtering method which uses a target of titanium, a first titanium nitride film 301 of film thickness 50 nm is formed. The thickness of a region of the titanium nitride film 301 is 5 nm or more. The nitrogen concentration of the titanium nitride film 301 is 52 atom % or more. Then, a copper film 302 of film thickness 400 nm, a cap titanium nitride film 303, and a second insulating film 201 comprising a silicon oxide film of film thickness 400 nm working as an etching mask are formed. Then, a desired pattern is obtained through dry-etching. Thus, with resistivity of wiring kept low, a wiring of high reliability with no peeling-off is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly, to a semiconductor device having a low-resistance and highly reliable wiring made of copper or copper alloy and a method of manufacturing the same.

[0002]

2. Description of the Related Art As is well known, aluminum or an aluminum alloy has been mainly used as a wiring material of an LSI (Large Scale Integrated Circuit). However, since aluminum has a low melting point (660 ° C.) and poor migration resistance, failures such as disconnection are likely to occur, and it is difficult to cope with high integration and high speed of LSI.

On the other hand, copper has a much higher melting point than aluminum (1083 ° C.) and a lower electric resistivity (about 2/3 of aluminum in bulk value), so that next-generation LSI
It is effective as a wiring material.

However, copper wiring has some disadvantages as compared with aluminum wiring. One of the problems is that the adhesion between the copper wiring and the insulating film is low.

In order to solve this problem, there is known a method in which a different kind of metal or alloy is sandwiched between a copper wiring and an insulating film as an adhesive layer.

An example of forming a copper wiring using this method is as follows.
"Applied Physic Letter
s Letter, 63 (19) (1993) pp. 2703-2704).

In this method, a 100-nm-thick titanium nitride film, a 500-nm-thick copper film, and a 50-nm-thick titanium nitride film are sequentially formed on a silicon substrate on which a 100-nm-thick silicon oxide film is formed as an insulating film by sputtering. After forming
A silicon oxide film is formed to a thickness of 300 nm, and dry etching is performed using the silicon oxide film as a mask to form a copper wiring. In the method described here, the titanium nitride layer immediately above the copper wiring is used as an adhesive layer between the silicon oxide film serving as an etching mask and the copper wiring, and the titanium nitride layer immediately below the copper wiring is used as the bonding layer between the substrate and the copper wiring. I have.

However, since the adhesion between the copper film and the titanium nitride film is generally not so high, there is a possibility that the copper film and the titanium nitride film may be peeled off after fine processing or cleaning, and high reliability is required. It is difficult to form a copper wiring having the same.

An example of a technique for solving this problem is disclosed in Japanese Patent Application Laid-Open No. H5-218036.

In the method described here, a 100-nm-thick tungsten layer is formed on a substrate on which a semiconductor element is formed by a CVD (chemical vapor deposition) method, and then a tungsten film having a thickness of 5 nm is formed.
In this method, a titanium layer having a thickness of 0 nm is formed by a sputtering method, a copper layer having a thickness of 300 nm is formed by a CVD method, and copper wiring is formed by a dry etching method.

[0011]

However, in a structure in which a copper film and a titanium film are in direct contact, titanium atoms may diffuse into the copper film and the resistivity of the copper film may increase.

An object of the present invention is to solve the problems of the conventional method and to provide a highly reliable copper wiring without peeling of the wiring without causing an increase in the resistivity of the copper film, and a method of manufacturing the same. That is.

[0013]

An object of the present invention is to provide a method for manufacturing a semiconductor device, comprising the steps of:
This is achieved by forming titanium nitride having a nitrogen concentration of 52 atomic% or more.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. In addition, each drawing is drawn schematically,
Parts unnecessary for the description are not shown.

Embodiment 1 FIG. 1 is a sectional view showing a manufacturing process of a semiconductor device according to the present invention. The description will be made in the following order.

First, as shown in FIG. 1A, an insulating film 200 made of a 500-nm-thick silicon oxide film having an opening is formed on a silicon substrate 100 on which a semiconductor element (not shown) is formed. Formed and tungsten plug 3
00 was formed by a selective CVD method to fill the opening. Then, by a sputtering method using a titanium target, under the conditions of DC power = 4 kW (power density per square centimeter 8 W) and a flow rate ratio of nitrogen gas to argon gas (flow rate ratio of nitrogen / argon) = 2,
After the first titanium nitride film 301 having a thickness of 50 nm is formed, a copper film 302 having a thickness of 400 nm, a titanium nitride film 303 for a cap, and a second silicon oxide film having a thickness of 400 nm are used as an etching mask for fine processing. Insulating film 20
1 was formed.

Next, a desired pattern is transferred to the second insulating film 201 serving as an etching mask by using a photolithography method and a dry etching method, and is dry-etched by a chlorine gas using an RF plasma etching apparatus. A desired patterned copper wiring as shown in FIG. 1 (b) was obtained. The same processing was performed by changing the film forming conditions and the film thickness of the first titanium nitride film 301, and several types of semiconductor devices were manufactured.

The surface of the sample thus formed was observed with an optical microscope and an SEM (scanning electron microscope).
If the ratio of the copper wiring remaining without peeling is defined as adhesiveness, if the titanium nitride film is formed under the condition that the nitrogen / argon flow rate ratio is large and the DC power is low as shown in FIG. 2, no peeling occurs. Wiring could be formed.

The composition of the first titanium nitride film 301 of the sample thus formed was examined by Auger electron spectroscopy. FIG. 3 is a diagram showing the relationship between the nitrogen concentration (atomic%) of the first titanium nitride film 301 of each sample and the adhesiveness of the copper wiring. Conventionally, as described in JP-A-8-97209, for example, a nitrogen concentration of 50 atomic% is used to improve barrier properties.
Although the following titanium nitride film has been used, when a copper wiring is formed using a conventional titanium nitride film as shown in FIG. 3, peeling occurs. However, when the nitrogen concentration of the first titanium nitride film 301 is set to 52 atomic% or more, a high-performance copper wiring without peeling can be obtained.

Further, the sample thus formed is
The relationship between the adhesiveness of the copper wiring and the thickness of the first titanium nitride film 301 was examined. As can be seen from FIG. 4, if there is a titanium nitride film of 5 nm or more between the copper wiring and the insulating film, a copper wiring without peeling can be obtained.

The sample thus formed is
After heat treatment at 450 ° C. for 30 minutes in a hydrogen atmosphere, the resistivity of the copper wiring was determined. If the nitrogen concentration of the first titanium nitride film was 50 at% or more, the resistivity of the wiring was 1.9 μΩcm or less. Therefore, it is not a problem in practical use.

That is, as shown in this embodiment, a titanium nitride film having a thickness of 5 nm or more is formed between the copper wiring and the insulating film.
If the nitrogen concentration of the titanium nitride film is 52 atomic% or more, the resistivity of the wiring is kept low as compared with the related art,
Highly reliable wiring without peeling can be realized.

In this embodiment, a single layer of titanium nitride is formed between the copper wiring and the insulating film.
In order to reduce the contact resistance with zero, it is possible to form titanium nitride, pure titanium, or another conductive film having a different composition between the titanium nitride and the insulating film. In order to enhance the barrier properties of the titanium nitride, other elements such as oxygen and silicon can be added to the titanium nitride.

<Embodiment 2> FIG. 5 is a process chart showing a second embodiment of the present invention.

First, as shown in FIG. 5A, an insulating film 200 made of a 500-nm-thick silicon oxide film having an opening is formed on a silicon substrate 100 on which a semiconductor element (not shown) is formed. Formed and tungsten plug 3
00 was formed by a selective CVD method to fill the opening. Thereafter, the film thickness is 50 nm under the conventional sputtering conditions of sputtering power = 8 kW (power density per square centimeter: 16 W), and the flow ratio of nitrogen gas to argon gas (nitrogen / argon flow ratio) = 1.
After the first titanium nitride film 301 is formed, the sample is transported to a plasma processing chamber, and ICP (inductively coupled plasma) power = 1 kW (power density per square centimeter 2 W), RF (high frequency) bias = 100 V Nitrogen plasma treatment was performed for 2 minutes.

Thereafter, as shown in FIG.
0 nm copper film 302, sputtering power = 8 kW, nitrogen /
Titanium nitride film 3 for cap under argon flow ratio = 1 condition
03, film thickness 400 as an etching mask for fine processing
A second insulating film 201 made of a silicon oxide film having a thickness of nm was formed.

Next, a desired pattern is transferred to the second insulating film 201 serving as an etching mask by using a photolithography method and a dry etching method, and is dry-etched by a chlorine gas using an RF plasma etching apparatus. The desired patterned copper wiring as shown in FIG. 5 (c) was obtained. The same processing was performed by changing the time of the nitrogen plasma processing, and several types of semiconductor devices were manufactured.

When the surface of the sample thus formed was observed with an optical microscope and an SEM (scanning electron microscope), it did not peel off if the plasma processing time was 2 minutes or more as shown in FIG. Highly reliable copper wiring was obtained.

That is, as shown in this embodiment, if the surface of the conventional titanium nitride film is treated with nitrogen plasma, a highly reliable wiring without peeling can be realized as compared with the conventional case.

In this embodiment, pure nitrogen is used as the plasma processing gas. However, a similar effect can be expected with a gas containing nitrogen atoms such as ammonia gas instead of pure nitrogen. Further, it is also possible to add an argon gas or the like to nitrogen or a gas containing a nitrogen atom, and carry out the sputter etching and the nitrogen plasma treatment at the same time.

<Embodiment 3> FIG. 7 is a process chart showing a third embodiment of the present invention. On a silicon substrate 100 on which a semiconductor element (not shown) is formed, a film 40 having an opening is formed.
An insulating film 200 having a thickness of 0 nm is formed, and an opening provided in the insulating film 200 is filled with a tungsten plug 300 formed by a selective CVD method.
m of the second insulating film 201 was formed. Next, a DC power = 4 kW (power density per square centimeter 8 W) and a flow rate ratio of nitrogen gas to argon gas (nitrogen) by sputtering using a titanium target on the second insulating film 201 provided with the opening. / Argon flow ratio) = 2
A first titanium nitride film 301 having a thickness of 50 nm under the following conditions:
A copper film 302 having a thickness of 800 nm was sequentially formed at 25 ° C. by a sputtering method (FIG. 7A).

Next, the wafer was transferred to a heat treatment chamber without breaking vacuum, and heat treated at 450 ° C. for 20 minutes.
The sample thus formed is subjected to CMP (chemical mechanical polishing).
The copper wiring was formed by removing the first titanium nitride film 301 and the copper film 302 in the region other than the opening provided in the second insulating film 201 by the method (FIG. 7B). The same processing was performed by changing the film forming conditions and the film thickness of the first titanium nitride film 301, and several types of semiconductor devices were manufactured.

When the surface and the cross section of the sample thus formed were observed with an optical microscope and an SEM, as in the case of the result shown in Example 1, the flow rate of nitrogen / argon was large and the DC power was low. 1 titanium nitride film 30
By forming 1, a wiring without peeling could be formed. Further, when the relationship between the thickness of the first titanium nitride film 301 and the adhesiveness was examined, a wiring without peeling was formed when the thickness of the first titanium nitride film 301 was 5 nm or more.

That is, as shown in this embodiment, a titanium nitride film having a thickness of 5 nm or more is formed between the copper wiring and the insulating film.
If the nitrogen / titanium composition ratio of the titanium nitride film is at least 52 atomic%, a highly reliable wiring with no peeling can be realized as compared with the related art.

In this embodiment, one layer of titanium nitride is formed between the copper wiring and the insulating film. However, similarly to the first embodiment, between the titanium nitride and the insulating film, titanium nitride having a different composition or pure titanium nitride is formed. It is also possible to form titanium or another conductive film. In order to enhance the barrier properties of the titanium nitride, other elements such as oxygen and silicon can be added to the titanium nitride.

[0036]

According to the present invention, it is possible to form a highly reliable copper wiring without peeling without increasing the resistivity of the copper wiring.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of a manufacturing step of a semiconductor device in a first embodiment of the present invention.

FIG. 2 is a diagram showing the DC power and the nitrogen / argon flow rate ratio dependency of the adhesiveness of a copper wiring.

FIG. 3 is a graph showing the dependency of the adhesiveness of copper wiring on the nitrogen concentration in titanium nitride.

FIG. 4 is a graph showing the dependence of the adhesiveness of a copper wiring on the thickness of a first titanium nitride film.

FIG. 5 is a cross-sectional view of a principal part in a manufacturing step of the semiconductor element in the second embodiment of the present invention.

FIG. 6 is a diagram showing the dependency of the adhesiveness of a copper wiring on exposure time to nitrogen plasma.

FIG. 7 is a cross-sectional view of a main part of a manufacturing step of a semiconductor device in a third embodiment of the present invention.

[Explanation of symbols]

Reference numeral 100: a substrate on which a semiconductor element is formed; 200, a first insulating film; 201, a second insulating film; 300, a connection hole buried with a conductive substance; 301, a first titanium nitride film;
02: copper film, 303: titanium nitride film for cap.

Claims (5)

[Claims] An insulating film formed on a semiconductor substrate, a copper or copper alloy wiring formed on or surrounded by the insulating film, and at least a peripheral surface of the copper or copper alloy wiring. The nitrogen concentration in the region in contact with the copper or copper alloy wiring between one surface and the insulating film is 52%.
A semiconductor device comprising titanium nitride of at least atomic%. 2. The titanium nitride according to claim 1, wherein the nitrogen concentration is 52.
2. The semiconductor device according to claim 1, wherein the thickness of the region that is at least atomic% is at least 5 nm. A step of forming an insulating film on the semiconductor substrate;
Forming a copper or copper alloy wiring on the insulating film or being surrounded by the insulating film; and forming titanium nitride between at least one peripheral surface of the copper or copper alloy wiring and the insulating film. A method for manufacturing a semiconductor device, comprising at least a step, wherein a nitrogen concentration in a region of the titanium nitride in contact with the copper or copper alloy is set to 52 atomic% or more. 4. The titanium nitride according to claim 1, wherein the nitrogen concentration is 52.
4. The method according to claim 3, wherein the thickness of the region that is at least atomic% is at least 5 nm. 5. A step of forming an insulating film on a semiconductor substrate;
Forming a copper or copper alloy wiring on the insulating film or being surrounded by the insulating film; and forming titanium nitride between at least one peripheral surface of the copper or copper alloy wiring and the insulating film. In a method of manufacturing a semiconductor device including at least a step, prior to the formation of the copper or copper alloy wiring, the surface of the titanium nitride is exposed to a plasma containing nitrogen atoms or nitrogen ions after the formation of the titanium nitride. Manufacturing method.