JPH05315334A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To make a metal interconnection line at a contact smooth by causing a CVD tungsten to be buried in an area of the contact which is incompletely filled when the tungsten is used for filling the contact and also used as an interconnection. CONSTITUTION:An interlayer dielectric film 4 is deposited on a silicon substrate 1 on which a lower layer interconnection line 3 is formed with a dielectric film 2 interposed between them, and a contact is opened. A sputtered titanium tungsten 5a is then deposited, and a CVD tungsten 7 is deposited. An aluminum alloy 8 is sputtered, and then a sputtered titanium tungsten 9b is deposited. A CVD tungsten 10 is deposited to fill the contact. The CVD tung-sten 10 and the sputtered titanium tungsten 5a are etched back. With the use of a resist as a mask, the aluminum allay 8, the CVD tungsten 7 and the sputtered titanium tungsten 5a are selectively etched away.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for filling a contact hole in a metal wiring forming process.

[0002]

2. Description of the Related Art To connect a metal wiring to the surface of a semiconductor substrate or to connect an upper wiring to a lower wiring of the semiconductor substrate, a method of sputtering aluminum alloy and then selectively etching using a resist as a mask is generally used. there were.

However, as semiconductor integrated circuits have become faster and more highly integrated, the contact diameter has become finer, and as shown in FIG. 6A, a contact is opened in the interlayer insulating film 4 covering the lower layer wiring 3. Even if the aluminum alloy 8 is sputtered, the aluminum alloy 8 is opened almost without being deposited inside the contact.

Then, by the CVD (chemical vapor deposition) method,
A method of completely filling tungsten in a contact hole and then forming an aluminum alloy wiring is disclosed in, for example, H. H. et al.
H. International Conference on Multilayer Wiring by Hoang et al.
0 Proceedings 7th Internet
Ional IEEE VLSI Intercon
ection Conference) pp. 133 ~
141.

The first method will be described with reference to FIG.

After opening a contact in the interlayer insulating film 4 on the silicon substrate 1, a refractory metal 5 made of titanium tungsten or titanium nitride having a thickness of 100 nm is deposited by a sputtering method, and then tungsten 7 is deposited by a CVD method.
Embed.

The refractory metal 5 improves the adhesion between the interlayer insulating film 4 and the CVD tungsten 7. Further, it suppresses the reaction between WF ₆ (tungsten hexafluoride) and H ₂ (hydrogen), which are reaction gases when growing tungsten 7, with the silicon substrate 1. Generally, titanium tungsten or titanium nitride is used.

After that, the CVD tungsten 7 and the sputtered refractory metal 5 on the interlayer insulating film 4 are etched back, and then an aluminum alloy 8 to be a metal wiring is formed.
At this time, if the etch back is too much, the CV in the contact
Since the D-tungsten 7 becomes thin and a step remains, the aluminum alloy 8 becomes open, the wiring resistance increases, and the yield decreases. On the other hand, if the CVD tungsten 7 remains on the interlayer insulating film 4, the metal wiring made of the aluminum alloy 8 is short-circuited.

Next, the second method will be described with reference to FIG.

This is for forming an aluminum alloy 8 to be a metal wiring without etching back the sputtered refractory metal 5 and the CVD tungsten 7 on the interlayer insulating film 4.

Next, the third method will be described with reference to FIGS.
This will be described with reference to (d).

First, as shown in FIG. 7A, an interlayer insulating film 4 is deposited on the silicon substrate 1 on which the lower wiring 3 is formed across the insulating film 2, and then contacts are opened.

Next, as shown in FIG. 7B, titanium nitride 5a is deposited by the sputtering method.

Next, as shown in FIG. 7C, tungsten 7 is deposited by the CVD method to fill the contact. At this time, the tungsten grown on the side surface of the contact forms a seam at the center.

Next, as shown in FIG.
CV by plasma containing ₆ (sulfur hexafluoride) as the main component
D Tungsten 7 is etched back. Then Cl
Interlayer insulating film 4 by plasma mainly composed of ₂ (chlorine)
The sputtered tungsten 5a on the surface is etched back.
After that, an upper wiring (not shown) made of an aluminum alloy is formed.

Next, the fourth method will be described with reference to FIGS.
This will be described with reference to (d).

First, as shown in FIG. 8A, an interlayer insulating film 4 is deposited on the silicon substrate 1 on which the lower wiring 3 is formed with the insulating film 2 interposed therebetween, and then contacts are opened.

Next, as shown in FIG. 8B, tungsten 6 is deposited by the sputtering method.

Next, as shown in FIG. 8C, tungsten 7 is deposited by the CVD method to fill the contact. At this time, the tungsten grown on the side surface of the contact forms a seam at the center.

Next, as shown in FIG. 8D, the CVD tungsten 7 and the sputtered tungsten 6 are etched back by plasma containing SF ₆ as a main component. After that, an upper wiring (not shown) made of an aluminum alloy is formed.

[0021]

When the CVD method is used to completely bury tungsten in a large-diameter contact that must be connected with low resistance such as power supply and ground by the first and second methods, the tungsten film is not formed. The thicker the wiring, the higher the wiring resistance. Therefore, as shown in FIG.
If the aluminum alloy 8 is formed without completely filling the contact with the tungsten 7, a recess is formed in the center of the contact, and a step is formed in the aluminum wiring at the contact. In addition, since the connection area with the aluminum wiring is smaller than that in the case where it is completely filled with CVD tungsten, there is a problem that the resistance at the contact increases.

When the sputtered titanium nitride is etched back by the third method, as shown in FIG. 7D, the interlayer insulating film 4 is formed.
The titanium nitride 5a on the side surface is also etched to form a recess (gap). When the uniformity of plasma etching is poor, there is a problem that the recess reaches the bottom surface of the contact and the lower layer wiring 3 is etched.

When CVD tungsten and sputtered tungsten are simultaneously etched back by the fourth method, as shown in FIG.
As shown in (d), the interlayer insulating film 4 is etched and the surface is roughened. Further, as the etching of the inter-layer insulation film 4 progresses, the inter-layer insulation film 4 becomes thin and the withstand voltage between the lower layer wiring 3 and the upper layer wiring decreases.

[0024]

A method of manufacturing a semiconductor device according to the present invention comprises a step of opening a contact in an interlayer insulating film formed on one main surface of a semiconductor substrate, and a first sputtering method for the contact. After depositing refractory metal, CV
A step of depositing a second refractory metal film by the D method, a step of depositing an aluminum alloy film on the second refractory metal film by a sputtering method, and a sputtering method on the aluminum alloy film and in the contact. A step of depositing a third refractory metal film by a CVD method and then a fourth refractory metal film by a CVD method, and the fourth refractory metal film and the third refractory metal film on the aluminum alloy by a dry etching method. Of etching back the refractory metal film, and patterning the laminated metal film composed of the aluminum alloy film, the second refractory metal film and the first refractory metal film.

Alternatively, in the method of manufacturing a semiconductor device of the present invention, a step of forming an interlayer insulating film on one main surface of a semiconductor substrate, a step of depositing a titanium nitride film on the interlayer insulating film, and the titanium nitride film. And selectively etching the interlayer insulating film to open a contact, depositing a tungsten film on the titanium nitride film and in the contact to fill the contact, and plasma etching the titanium nitride film on the titanium nitride film. It includes a step of etching back the tungsten film and a step of etching the titanium nitride film.

[0026]

EXAMPLE FIG. 1A shows a first example of the present invention.
This will be described with reference to (c).

First, as shown in FIG. 1A, an interlayer insulating film 4 is deposited on a silicon substrate 1 on which an insulating film 2 is formed and a lower wiring 3 is formed, and a contact having a diameter of 1 μm is opened. Next, titanium-tungsten 5a having a thickness of 100 nm is deposited by the sputtering method. Next 350-400
WF _{6 at} sccm and H _{2 at} 600-700 sccm
As a reaction gas and the substrate temperature is 400 to 450 ° C.
Tungsten 7 having a thickness of 200 nm is deposited by the VD method. Next, the aluminum alloy 8 having a thickness of 500 nm is deposited by the sputtering method in which the substrate temperature is 130 ° C. or lower.

Next, as shown in FIG. 1B, titanium-tungsten 9b having a thickness of 100 nm is deposited by a sputtering method. Next, WF ₆ of 350 to 400 sccm and H ₂ of 600 to 700 sccm are used as reaction gases, and a thickness of 20
Deposit 0 nm of tungsten 10 to fill the contact.

Next, as shown in FIG. 1C, the CVD tungsten 10 and the sputtered titanium tungsten 5a on the aluminum alloy 8 are etched back by dry etching using SF ₆ and C ₂ F ₄ as reaction gases. Next, the aluminum alloy 8, the CVD tungsten 7, and the sputtered titanium tungsten 5a are selectively etched using a resist (not shown) as a mask.

In this embodiment, the contact can be flattened by the upper wirings 5a, 7 and 8. The contact was completely filled with titanium-tungsten 5a, tungsten 7, titanium-tungsten 9b and tungsten 10, and the contact (connection) resistance could be reduced.

Next, a second embodiment of the present invention will be described with reference to FIGS. 2 (a) and 2 (b).

First, as shown in FIG. 2A, an interlayer insulating film 4 is deposited on the silicon substrate 1 on which the lower wiring 3 is formed with the insulating film 2 interposed therebetween, and then a contact having a diameter of 1 μm is opened. Next, sputtered titanium tungsten 5a, CV
D tungsten 7 and aluminum alloy 8 are sequentially deposited. The process up to this point is the same as in the first embodiment.

Next, titanium nitride 9a having a thickness of 100 nm is deposited by the sputtering method. Next, tungsten 10 is deposited by the CVD method to fill the contact.

Next, as shown in FIG. 2B, the CVD tungsten 10 on the sputtered titanium nitride 9a is etched back by dry etching. At this time, fluorine-based S
With F ₆ gas, titanium nitride that is not etched 9
a You can stop at the surface. Next, using a resist (not shown) as a mask, sputtered titanium nitride 9a,
The aluminum alloy 8, the CVD tungsten 7, and the sputtered titanium tungsten 5a are selectively etched.

In this example, by depositing titanium nitride 9a on the aluminum alloy 8, it was possible to suppress the generation of hillocks in the aluminum alloy 8. Further, in the resist process, the titanium nitride 9a serves as an antireflection film, so that the exposure conditions are improved.

Next, a third embodiment of the present invention will be described with reference to FIGS.

First, as shown in FIG. 3A, a lower wiring 3 made of an aluminum alloy having a thickness of 800 nm is formed on the insulating film 2 on the silicon substrate 1. Next, after depositing a silicon oxide film by the plasma CVD method, SOG is performed.
After applying (spin on glass), a flat interlayer insulating film 4 is formed by reflowing and etching back. Next, using titanium as a target, reactive sputtering using a mixed gas of argon and nitrogen was performed to obtain a thickness of 1
Deposit 00 nm titanium nitride 5a.

Next, as shown in FIG. 3B, the sputtered titanium nitride 5a and the interlayer insulating film 4 are etched by using a resist (not shown) as a mask to open contacts, and then the resist is removed.

Next, as shown in FIG. 3C, 100 nm thick tungsten 6 is deposited by the sputtering method.

Next, as shown in FIG. 3D, a tungsten film 7 having a thickness of 0.8 μm is deposited by the CVD method using WF ₆ and H ₂ to fill the contact. At this time, the tungsten grown on the side surface of the contact forms a seam at the center. The role of the sputtered tungsten 6 before this is that when the CVD tungsten 7 is deposited, the lower wiring 3 and the W are formed.
This is to prevent the reaction with F ₆ to form AlF ₃ (aluminum hexafluoride) which is an insulator.

Next, as shown in FIG. 3 (e), C on the surface of the sputtered titanium nitride 5a was removed by plasma using SF _6.
The VD tungsten 7 and sputtered tungsten 6 are etched back.

Next, as shown in FIG. 3 (f), the sputtered titanium nitride 5a is etched by plasma using Cl ₂ so that the contact is filled with sputtered tungsten 6 and CVD tungsten 7. Thereafter, an upper layer wiring (not shown) made of aluminum alloy is formed to complete the two-layer wiring.

Instead of depositing the tungsten nitride 5a by the sputtering method used in this embodiment, the thickness of the tungsten nitride 5a is set to 1 by the sputtering method.
Tungsten nitride can be formed by depositing Ti (titanium) having a thickness of 00 nm and then performing heat treatment in a nitrogen atmosphere at 800 ° C.

Further, instead of etching the tungsten nitride 5a with plasma using Cl ₂ , it is also possible to carry out wet etching with an aqueous solution of hydrogen peroxide and ammonia.

Next, a fourth embodiment of the present invention will be described with reference to FIGS.

First, as shown in FIG. 4A, after forming the lower layer wiring 3 on the insulating film 2 on the silicon substrate 1,
The interlayer insulating film 4 is formed and then planarized. Next, titanium nitride 5a is deposited by reactive sputtering, and the contact is opened. The process up to this point is the same as in the third embodiment.

Next, as shown in FIG. 4B, a tungsten film 7 having a thickness of 500 nm is grown by the selective CVD method using WF ₆ and SiH ₄ (monosilane). The reason why the contact is not completely buried here is that the thickness of the interlayer insulating film 4 differs depending on the location, and there are contacts with different depths. When the tungsten 7 is filled to match the shallowest contact, the deep contact is filled only part way.

Next, as shown in FIG. 4C, 100 nm thick tungsten 6 is deposited by the sputtering method.

Next, as shown in FIG. 4D, 0.8 μm thick tungsten 7 is deposited by the CVD method using WF ₆ and H ₂ to fill the contact. At this time, the tungsten grown on the side surface of the contact forms a seam at the center.

Next, as shown in FIG. 4 (e), C on the surface of the sputtered titanium nitride 5a is removed by plasma using SF _6.
The VD tungsten 7 and sputtered tungsten 6 are etched back.

Next, as shown in FIG. 4 (f), the sputtered titanium nitride 5a is etched by plasma using Cl ₂ so that the contacts are filled with CVD tungsten 7c, sputtered tungsten 6 and CVD tungsten 7. Thereafter, an upper layer wiring (not shown) made of aluminum alloy is formed to complete the two-layer wiring.

In the third embodiment, when tungsten is etched back by plasma, the etching rate of the seam portion is large. Therefore, in the third embodiment, as shown in FIG.
As shown in, the lower wiring 3 is also etched.

On the other hand, in the fourth embodiment, as shown in FIG. 4E, the selective CVD tungsten 7c and the sputtered tungsten 6 are buried in the contact. Therefore, even if the etch back is over, the lower layer wiring 3 is not etched.

The formation of the upper layer wiring has been described above.
The present invention can also be applied to the lower layer wiring connected to the diffusion layer on the surface of the semiconductor substrate.

[0055]

EFFECTS OF THE INVENTION After CVD tungsten is deposited on a contact, an aluminum alloy is sputtered, and then CVD tungsten is embedded in the center of the contact. As a result, the metal wiring was flattened at the contact, and the contact resistance could be reduced.

Since sputtered titanium nitride is not formed on the side surface of the contact, a recess (gap) does not occur when the CVD tungsten and the sputtered tungsten are etched back.

Further, since sputtered titanium nitride is formed on the interlayer insulating film, when the CVD tungsten and the sputtered tungsten are etched back, the etching stops at the sputtered titanium nitride.

Therefore, the surface of the interlayer insulating film becomes rough,
The problem that the interlayer insulating film becomes thin could be solved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of the present invention in process order.

FIG. 2 is a cross-sectional view showing a second embodiment of the present invention in process order.

FIG. 3 is a sectional view showing a third embodiment of the present invention in the order of steps.

FIG. 4 is a sectional view showing a fourth embodiment of the present invention in process order.

FIG. 5 is a cross-sectional view comparing a third embodiment of the present invention with a fourth embodiment.

FIG. 6 is a cross-sectional view showing a conventional method for filling a contact hole to form a metal wiring.

FIG. 7 is a cross-sectional view showing a conventional method for filling a contact hole to form a metal wiring.

FIG. 8 is a cross-sectional view showing a conventional method of filling a contact hole to form a metal wiring.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Insulating film 3 Lower layer wiring 4 Interlayer insulating film 5 Sputter refractory metal 5a Sputtered titanium nitride 5b Sputtered titanium tungsten 6 Sputtered tungsten 7 CVD tungsten 8 Aluminum alloy 9a Sputtered titanium nitride 9b Sputtered titanium tungsten 10 CVD tungsten

Claims (8)

[Claims] 1. A step of forming a contact in an interlayer insulating film formed on one main surface of a semiconductor substrate, and a step of depositing a first refractory metal on the contact by a sputtering method,
A step of depositing a second refractory metal film by a CVD method,
A step of depositing an aluminum alloy film on the second refractory metal film by a sputtering method, and a step of depositing a third refractory metal film on the aluminum alloy film and in the contact by a sputter method, and then by a CVD method. Depositing a fourth refractory metal film, and etching back the fourth refractory metal film and the third refractory metal film on the aluminum alloy by a dry etching method,
And a step of patterning a laminated metal film including the aluminum alloy film, the second refractory metal film, and the first refractory metal film. 2. A step of forming a contact in an interlayer insulating film formed on one main surface of a semiconductor substrate, and a step of depositing a first refractory metal on the contact by a sputtering method,
A step of depositing a second refractory metal film by a CVD method,
A step of depositing an aluminum alloy film on the second refractory metal film by a sputtering method, and a step of depositing a third refractory metal film on the aluminum alloy film and in the contact by a sputter method, and then by a CVD method. Depositing a fourth refractory metal film, etching back the fourth refractory metal film on the third refractory metal film by a dry etching method, and the third refractory metal film And a step of patterning a laminated metal film including the aluminum alloy film, the second refractory metal film, and the first refractory metal film. 3. The method for manufacturing a semiconductor device according to claim 1, wherein the third refractory metal film is one of a titanium tungsten film and a titanium nitride film. 4. A step of forming an interlayer insulating film on one main surface of a semiconductor substrate, a step of depositing a titanium nitride film on the interlayer insulating film, and a step of selectively etching the titanium nitride film and the interlayer insulating film. Opening a contact with the titanium nitride film, depositing a tungsten film on the titanium nitride film and in the contact to fill the contact, and etching back the tungsten film on the titanium nitride film by plasma etching, And a step of etching the titanium nitride film. 5. The method for manufacturing a semiconductor device according to claim 4, wherein the titanium nitride film is deposited by a sputtering method. 6. A step of forming an interlayer insulating film on one main surface of a semiconductor substrate, and a titanium film is deposited on the interlayer insulating film, followed by heat treatment in a nitrogen atmosphere to convert the titanium film into a titanium nitride film. Changing step, selectively etching the titanium nitride film and the interlayer insulating film to open a contact, depositing a tungsten film on the titanium nitride film and in the contact to fill the contact, and plasma etching Etching back the tungsten film on the titanium nitride film by
And a step of etching the titanium nitride film. 7. A step of forming an interlayer insulating film on one main surface of a semiconductor substrate, a step of depositing a titanium nitride film on the interlayer insulating film, and a step of selectively etching the titanium nitride film and the interlayer insulating film. A contact is opened, and a step of depositing a first tungsten film on the titanium nitride film and in the contact by a sputtering method, and then depositing a second tungsten film by a CVD method to fill the contact. A method of manufacturing a semiconductor device, comprising: a step of etching back the second tungsten film and the first tungsten film on the titanium nitride film by plasma etching; and a step of etching the titanium nitride film. 8. A step of forming an interlayer insulating film on one main surface of a semiconductor substrate, a step of depositing a titanium nitride film on the interlayer insulating film, and a step of selectively etching the titanium nitride film and the interlayer insulating film. Opening a contact, and depositing a first tungsten film on the contact by a selective CVD method, depositing a second tungsten film on the titanium nitride film and in the contact, and then burying the contact And a step of etching back the second tungsten film on the titanium nitride film by plasma etching, and a step of etching the titanium nitride film.