JPH10242268A - Method of filling connection hole in multilayer wiring structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of filling a connection hole, which can perform the filling by treatment at relatively low temperature without influence on lower-layer wiring, and besides can perform the filling favorably without being influenced by moisture even if an interlayer insulating film contains moisture much, when filling the connection hole leading to the lower-layer wiring with a wiring material. SOLUTION: In this filling method, lower-layer wiring 11 consisting of low melting point metal or low melting point alloy is made on a substrate 10, and interlayer insulating films 12 and 13 are made to cover the lower-layer wiring 11, and a connection hole 14 leading to the lower-layer wiring 11 is made, and titanium is grown on the interlayer insulating films 12 and 13, covering the connection hole 14, and nitriding by plasma nitriding method is applied to the titanium film 15 so as to make the titanium film 15 into a titanium nitride film 16, and after nitriding, a wiring material 17 consisting of low-melting point metal or low-melting point alloy is grown, and the connection hole 14 is stopped with a film consisting of a wiring material 17 by high-pressure reflow method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for burying connection holes, and more particularly to a method for burying connection holes in a multilayer wiring structure in which a lower wiring is formed of a low melting point metal or a low melting point alloy.

[0002]

2. Description of the Related Art With the miniaturization of internal wiring due to the high integration of VLSIs, the technique of embedding wiring material in fine connection holes has become important. Conventionally, techniques for embedding a wiring material in a fine connection hole include a CVD blanket W method,
High-temperature sputtering using a wiring material such as Al or Cu,
A reflow method, a high-pressure reflow method, and the like have been studied, and some of them have been put to practical use.

The CVD blanket W method is most widely used as a wiring embedding technique because of its high and stable ability to embed connection holes and the like. However, in addition to the W film formation step, an adhesion layer (base film) film formation step, a W etch back step, a wiring material film formation step, and the like are required, and there is a disadvantage that the process is complicated. The high-temperature sputtering method and the reflow method using Al or Cu have advantages that the process is simpler than the CVD blanket W method, and that Al and Cu have lower resistance than W. However, since high temperature substrate heating of about 500 to 550 [deg.] C. is necessary for embedding, there is a concern that the reliability of the lower layer wiring may be reduced particularly when applied to the embedding into the connection hole in the multilayer wiring structure. . Furthermore, the embedding capability itself is not so high, and in the case of a connection hole, the aspect ratio is limited to about 2 to 3, and it is considered that application to a fine device in the future is difficult. The high-pressure reflow method using Al or Cu has recently attracted particular attention as a technique for improving the embedding property of the reflow technique.

A description will be given of an example in which an embedding technique by a high-pressure reflow method is applied to embedding in a connection hole leading to a lower wiring. First, as shown in FIG. 3A, a connection hole 3 communicating with the lower wiring 1 is formed in an interlayer insulating film 2 formed on the substrate (not shown) so as to cover the lower wiring 1.
Next, a base film 4 functioning as an adhesion layer is formed to cover the connection holes 3. In this example, as the base film 4, Ti and TiN are formed in this order by a normal sputtering method.
A laminated film of Ti (the lower layer is Ti and the upper layer is TiN) is formed and used as a base film 4.

Next, the substrate is heated to about 400 ° C., and a wiring material 5 such as Al or an Al alloy is formed in that state. At this time, the thickness of the film made of the wiring material 5 is changed to the thickness of the connection hole 3.
The wiring material 5 bridges over the opening of the connection hole 3 as shown in FIG.
As a result, the opening is covered with the wiring material 5, and the void 6 is left in the connection hole 3. Subsequently, the substrate is heated to about 400 to 450 ° C. in a high vacuum atmosphere,
Al is softened, and at the same time, an inert gas such as Ar is introduced at a high pressure, and as shown in FIG.
Is pressed into the connection hole 3 while flowing. Further, by continuing this, as shown in FIG.
The wiring material 5 is buried and filled in the connection holes 3 until the state of disappearing. According to the embedding technique by such a high-pressure reflow method, the aspect ratio is 4 to 5 in an ideal case.
Degree of connection holes can be buried.

[0006]

By the way, in such an embedding technique by the high-pressure reflow method, FIG.
As shown in (c), when this technique is used for embedding for connection between the lower wiring 1 and the upper wiring in a multilayer wiring structure, the lower wiring 1 is particularly formed of a low melting point metal or a low melting point alloy. In such a case, there is a limitation that heat treatment at a high temperature cannot be performed.

Further, in the filling technique by the high-pressure reflow method, the filling property is very sensitive to the state of the interlayer insulating film 2 forming the connection hole 3, and particularly the interlayer insulating film 2 contains a large amount of moisture. In this case, the embedding property is significantly reduced. The reason is considered as follows. During high-pressure reflow, the substrate is heated to about 400 to 450 ° C. At this time, moisture and the like are degassed from the interlayer insulating film 2, and an oxide layer 7 is formed on the TiN surface of the base film 4 as shown in FIG. You. Then, the wiring material 5 pushed into the connection hole 3
An oxide layer 7 that is difficult to flow is formed at the interface between the substrate and the base film 4 and TiN. It will be.

However, in recent years, due to the demand for miniaturization of VLSI and flattening of an interlayer insulating film accompanying multilayer wiring, a normal pressure CVD method (chemical vapor phase) using O ₃ and tetraethoxysilane (TEOS) as reaction gases has been demanded. An SiO ₂ film (hereinafter, referred to as an O ₃ -TEOS · SiO ₂ film) or a spin-on-glass film (hereinafter, referred to as an SOG film) formed by a growth method) has excellent flatness but high moisture absorption. There is a tendency that an interlayer insulating film made of a material is often used. Therefore, it is desired to provide an improvement measure that enables good embedding even when an interlayer insulating film made of a material having high hygroscopicity is used.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a wiring made of a low melting point metal or a low melting point alloy in a connection hole leading to a lower wiring formed of a low melting point metal or a low melting point alloy. When embedding a material, the embedding can be performed by a relatively low-temperature process that does not affect the lower wiring, and the embedding can be performed satisfactorily even if the interlayer insulating film contains a large amount of moisture. It is an object of the present invention to provide a method for filling a connection hole which can be performed.

[0010]

According to the present invention, there is provided a method for filling a connection hole in a multilayer wiring structure, comprising the steps of: forming a lower wiring made of a low melting point metal or a low melting point alloy on a substrate; Forming an insulating film, forming a connection hole communicating with the lower wiring in the interlayer insulating film, forming titanium on the interlayer insulating film to cover the inside of the connection hole, and forming the titanium film Performing a nitriding process by a plasma nitriding method to convert the titanium film into a titanium nitride film; and, after the nitriding process, forming a wiring material made of a low-melting-point metal or a low-melting-point alloy while covering the connection hole. And embedding a film made of the wiring material in the connection hole by a high-pressure reflow method.

According to this method of burying the connection holes in the multilayer wiring structure, the nitriding treatment is performed by the plasma nitridation method which can be performed at a low temperature, so that the titanium nitride film can be formed without adversely affecting the lower wiring. Will be possible. Further, a titanium film is formed so as to cover the inside of the connection hole, and then the titanium film is nitrided by a plasma nitridation method to form a titanium nitride film. The film becomes denser than the titanium nitride film obtained in the above, and has a high barrier property against moisture and the like. Therefore, even if a high moisture film is used as the interlayer insulating film, the titanium nitride film can suppress the permeation of outgas such as moisture into the connection holes, and thereby the oxide layer caused by the outgas can be suppressed. Formation can be prevented.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
FIGS. 1A to 1E are diagrams for explaining an embodiment of a method for burying connection holes in a multilayer wiring structure according to the present invention. In FIG. 1, reference numeral 10 denotes a base. In addition,
The base 10 is a precursor of a semiconductor device, and is formed by forming various semiconductor device components (not shown) on a silicon wafer.

First, as shown in FIG. 1A, an Al--Si alloy was formed as a wiring material on a substrate 10 and then patterned to form a lower wiring 11 connected to the above components. Subsequently, in order to eliminate the step caused by the formation of the lower wiring 11 and to planarize it, O ₃ and tetraethoxysilane are used as reaction gases to form SiO 2 by a normal pressure CVD method.
₂ was deposited to form a first interlayer insulating film 12 made of an O ₃ -TEOS.SiO ₂ film. Here, the O ₃ -TEOS.SiO ₂ film serving as the first interlayer insulating film 12 has a high hygroscopic property due to physical adsorption, and therefore easily removes moisture in the atmosphere such as when left in the air at room temperature. It has the property of adsorbing to The first interlayer insulating film 1
2 is 0.5 μm from the upper surface of the lower wiring 11.
m.

Next, the SiO 2 is formed by plasma CVD.
₂ was deposited on the first interlayer insulating film 12 to form a second interlayer insulating film 13. Here, the second interlayer insulating film 13
The SiO ₂ film formed by the plasma CVD method has a low hygroscopic property, though depending on the forming conditions, and therefore has a sufficient moisture absorption compared to the first interlayer insulating film 12 made of the O ₃ -TEOS.SiO ₂ film. The nature is low.
Note that the thickness of the second interlayer insulating film 13 is set to 0.1.
It was about 4 μm.

Next, the second interlayer insulating film 1 is formed by known photolithography and dry etching techniques.
3. The first interlayer insulating film 12 was opened, and a connection hole 14 communicating with the lower wiring 11 was formed. Here, the connection hole 14 has an opening diameter of about 0.3 μm and a depth of about 0.9 μm. Next, the substrate 10 is placed on a heater stage in a gas chamber, and Ar is introduced into the gas chamber to make an Ar atmosphere, and the pressure in the chamber is reduced to 13 °.
The pressure was adjusted to 3 Pa, and in this state, the substrate 10 was subjected to a preheating treatment at 450 ° C. for 2 minutes. Subsequently, the lower wiring 1 is formed at the bottom of the connection hole 14 by a conventionally known Ar sputter etching.
1. The natural oxide film (not shown) formed on the upper surface was removed.

Next, a film of Ti is formed by ECRCVD under the following conditions, and as shown in FIG.
A titanium film 15 having a thickness of about 0.7 μm was formed in a state of covering the inner wall surface and the upper surface of the lower wiring 11 facing the connection hole 14. Ti film formation conditions Microwave; 2.45 GHz, 2.8 kW Process gas; TiCl ₄ / H ₂ / Ar = 3/100 /
170 sccm pressure; 0.4 Pa Substrate temperature: 450 ° C. By forming the Ti film by the CVD method as described above, the titanium film 15 can be formed with good step coverage, and thus the inner wall surface of the connection hole 14 can be sufficiently formed. The titanium film 15 could be deposited and formed with a suitable thickness.

Next, the titanium film 15 was subjected to a nitriding treatment by a plasma nitriding method to form a titanium nitride film 16 functioning as an adhesion layer as shown in FIG. Here, as the nitriding treatment by the plasma nitriding method,
An ECR method under the following conditions was employed. Plasma nitriding conditions Process gas; H ₂ / NH ₃ / Ar = 30/8/170
sccm pressure; 0.23 Pa μ wave power; 2800 W heating temperature; 400 ° C.

In such a nitriding treatment by the plasma nitriding method, the treatment can be performed at a low temperature of 200 to 500 ° C., for example, as compared with the thermal nitridation treatment requiring heating at about 900 ° C. The titanium film 15 can be satisfactorily nitrided without any adverse effect on the lower wiring 11 made of the Al-Si alloy which is a melting point alloy. Further, the titanium nitride film 16 formed in this manner is made of titanium nitride (TiN) formed by reactive sputtering or the like.
The film becomes denser than the film, and has a high barrier property against moisture and the like.

Next, an Al-0.5% Cu alloy is formed under the following conditions by a DC magnetron sputtering method, and a wiring material film serving as an upper wiring is formed on the titanium nitride film 16 as shown in FIG. 17 was formed to a thickness of about 0.5 μm. Al-0.5% Cu alloy film forming conditions DC power; 15 kW Process gas; Ar 100 sccm pressure; 0.4 Pa Film forming temperature: 400 ° C. When the wiring material film 17 is thus formed, the connection hole 1 is formed.
4, a void 18 is formed between the base film 16 and the wiring material film 17.

Next, the wiring material film 17 was subjected to a reflow process by the high-pressure reflow method under the following conditions, and the wiring material constituting the wiring material film 17 was embedded in the connection holes 14 as shown in FIG. . High-pressure reflow processing conditions Process gas; Ar pressure; 70 MPa Reflow time; 1 minute Substrate temperature: 450 ° C. Note that the series of processes from the Ar sputter etching to the high-pressure reflow are continuously performed in a vacuum using a multi-chamber apparatus. I went to. Thereafter, an upper layer wiring (not shown) was formed by etching the wiring material film 17 after the reflow treatment, and a multilayer wiring structure was obtained.

In such a method for filling the connection holes, since the nitriding is performed by the plasma nitriding method, the temperature condition can be set to a relatively low temperature of about 200 to 500 ° C. The titanium nitride film 16 can be formed without adversely affecting the structure. In addition, the dense titanium nitride film 16 formed by the plasma nitridation method and having the denseness among the first and second interlayer insulating films 12 and 13 constituting the interlayer insulating film has particularly high hygroscopicity and therefore contains a large amount of moisture. In order to effectively prevent outgas such as moisture from the interlayer insulating film 12, an oxide layer is formed on the wiring material film 17 due to the outgassing, thereby preventing a defective filling of the wiring material from occurring. Thus, good embedding can be performed.

Since the titanium nitride film 16 effectively barriers outgas such as moisture, the interlayer insulating film has high hygroscopicity and therefore contains a large amount of moisture, O ₃ -TE.
An OS.SiO ₂ film can be used, which facilitates planarization by an interlayer insulating film. Also,
Since the titanium film 15 is formed by the CVD method, the step coverage on the inner wall surface of the connection hole 14 is better than when the titanium film 15 is formed by, for example, the sputtering method, and thus a more reliable moisture barrier effect is obtained. This allows better embedding.

FIGS. 2A and 2B show FIGS.
It is a figure for explaining the modification of the example of an embodiment shown to (e). This embodiment is different from the embodiment shown in FIGS. 1A to 1E in that a titanium film 15 is formed without performing a series of processes from Ar sputtering to high-pressure reflow, and then the film is formed. The point is that the nitriding process is performed by an apparatus different from the apparatus used in the above, and a laminated film 19 made of TiN / Ti is further formed on the titanium nitride film 16 as a base film.

That is, in this example, the connection hole 14 is opened as shown in FIG.
The natural oxide film on the upper surface of the lower wiring 11 was removed by r-sputter etching. Next, the substrate 10 was taken out of the apparatus subjected to the Ar sputter etching, put into another CVD apparatus, and a titanium film was formed by a CVD method under the same conditions as in the previous example to form a titanium film 16. Next, the substrate 10 was taken out and put into another plasma processing apparatus, and a plasma nitridation process was performed under the same conditions as in the previous example, and the titanium film 15 was changed to a titanium nitride film 16.

Subsequently, a DC is formed on the titanium nitride film 16.
Ti, T under the following conditions by magnetron sputtering
iN was formed in this order to form a laminated base film 19. Ti film formation conditions DC power; 6 kW Process gas; Ar 100 sccm pressure; 0.4 Pa Film formation temperature: 400 ° C. Film thickness: 20 nm TiN film formation conditions DC power: 12 kW Process gas; Ar / N ₂ 20/70 sccm pressure; 4Pa Film forming temperature; 400 ° C Film thickness: 50 nm

Next, in the same manner as in the previous example, Al-0.5
2B, a wiring material film 17 made of a% Cu alloy is formed, and a high-pressure reflow process is performed to change the wiring material forming the wiring material film 17 into the connection holes 14 as shown in FIG.
Embedded in the wiring material film 1 after reflow processing
7 was etched to form an upper layer wiring (not shown) to obtain a multilayer wiring structure.

In this method of filling the connection holes, the nitriding is performed by the plasma nitriding method at a low temperature as in the previous example. And a dense titanium nitride film 1 formed by a plasma nitriding method.
6 effectively barriers outgassing of moisture and the like, so that poor embedding of the wiring material can be prevented and good embedding can be performed. Further, in this example, a film forming process of titanium (Ti) and a plasma nitriding process are performed using an existing CVD device and a plasma processing device, respectively, without using an expensive multi-chamber device as in the previous example. As a result, production costs can be reduced. Here, in this example, when transporting between the apparatuses,
However, as described above, since the titanium nitride film 16 has a high barrier property against moisture and the like as described above, the titanium nitride film 16 can be buried well without lowering the burying property.

In the above embodiment, the lower wiring 11
Al-Si alloy was used as the material of the above, and the Al-0.5% Cu alloy was used as the wiring material film 17 to be the upper layer wiring. However, the present invention is not limited to these, and any of them has a low melting point metal or Any alloy having a low melting point may be used. Specifically, metals such as Al, Cu, Ag, and Au, and Al-
An Al alloy such as Si-Cu or Al-Ge, or a Cu alloy can be used. In addition, the present invention is not limited to the nitriding conditions by the plasma nitriding method, and the present invention is not limited to the above example. For example, N ₂ can be used instead of NH ₃ as a process gas. Other plasma processing methods can also be used. Further, in the above-described embodiment, the titanium film 15 is formed by the CVD method, but may be formed by a normal sputtering method.

[0029]

As described above, the method of embedding the connection hole in the multilayer wiring structure of the present invention is a method in which the nitriding treatment is performed by the plasma nitriding method which can be performed at a low temperature, so that the lower wiring is adversely affected. Thus, a titanium nitride film can be formed without the need. In addition, since a titanium nitride film obtained by performing a nitriding treatment by a plasma nitriding method becomes dense, and thus the titanium nitride film has a high barrier property against moisture and the like, a film having high moisture is used as an interlayer insulating film. However, the titanium nitride film can suppress the outgassing of moisture and the like into the connection holes, thereby preventing the formation of an oxide layer due to the outgassing and reducing the embedding failure of the wiring material. It is possible to prevent the occurrence and to perform a good embedding. In addition, since the titanium nitride film effectively blocks outgas such as moisture, the interlayer insulating film has high hygroscopicity, and thus O ₃ containing a large amount of moisture.
Can be used -TEOS · SiO ₂ film and SOG film, thereby to facilitate planarization by an interlayer insulating film.

[Brief description of the drawings]

FIGS. 1A to 1E are side sectional views of a main part for explaining an embodiment of a method for burying connection holes in a multilayer wiring structure according to the present invention in the order of steps.

2 (a) and 2 (b) are cross-sectional views of a main part for describing a modification of the embodiment shown in FIGS. 1 (a) to 1 (e).

3 (a) to 3 (c) are side sectional views for explaining a conventional wiring material embedding technique in the order of steps.

FIG. 4 is a side sectional view of a main part for describing a problem of a conventional embedding method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Base 11 Lower wiring 12 First interlayer insulating film 13 Second interlayer insulating film 14 Connection hole 15 Titanium film 16 Titanium nitride film 17 Wiring material film

Claims (3)

[Claims] A step of forming a lower layer wiring made of a low melting point metal or a low melting point alloy on a base; a step of forming an interlayer insulating film covering the lower layer wiring; and forming a connection hole leading to the lower layer wiring to the interlayer. Forming an insulating film, forming a titanium film on the interlayer insulating film covering the inside of the connection hole, performing a nitriding process on the titanium film by a plasma nitriding method,
A step of forming a titanium film into a titanium nitride film; a step of forming a wiring material made of a low melting point metal or a low melting point alloy after the nitriding treatment so as to cover the connection hole; Burying the connection hole in the connection hole by a method. 2. The interlayer insulating film according to claim 1, wherein at least a part thereof uses ozone and tetraethoxysilane as a reaction gas and has a CV
2. The method according to claim 1, wherein the film is a SiO ₂ film or a spin-on-glass film formed by a method D. 3. The method according to claim 1, wherein the step of forming the titanium film is performed by a CVD method.