JPH06252269A - Semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To improve resistance to electromigration in the vicinity of an alloy wiring layer interface, by forming an alloy layer composed of aluminum and tungsten between tungsten and an aluminum alloy wiring layer. CONSTITUTION:At least tungsten is buried in a connection hole which connects a semiconductor layer or a metal wiring layer 101 with an aluminum alloy wiring layer 105 positioned above the semiconductor layer or the metal wiring layer 101. Between the tungsten 104 and the aluminum alloy wiring layer 105, an alloy layer 106 composed of at least aluminum and tungsten is formed. Since the aluminum alloy does not directly come into contact with the tungsten 104, resistance to electromigration in the vicinity of the interface between the tungsten 104 and the aluminum alloy wiring layer 105 is improved. Generation of voids in aluminum alloy or tungsten can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring structure in a connection hole portion of a semiconductor device and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, a semiconductor layer or a metal wiring layer,
After tungsten is embedded by chemical vapor deposition (hereinafter referred to as CVD method) in a connection hole that connects an aluminum alloy wiring layer located above a semiconductor layer or a metal wiring layer, tungsten and an insulating film When an aluminum alloy wiring layer is formed on the semiconductor layer or the metal wiring layer and the aluminum alloy wiring layer are connected to each other, without forming an alloy layer made of aluminum and tungsten between the tungsten and the aluminum alloy wiring layer, I was making a connection. Below, an example will be shown as an example in which a metal wiring layer and an Al alloy wiring are connected.

FIG. 2 shows a cross-sectional structure of a connecting portion between a metal wiring layer and an aluminum alloy wiring layer located thereabove according to a conventional method.
Shown in. 201 is a metal wiring layer, 202 is an insulating film, 203
Is titanium, 204 is tungsten, and 205 is an aluminum alloy wiring layer. First, an insulating film 202 having a thickness of 1.0 μm is formed on a metal wiring layer 201 having a thickness of 0.4 μm. The insulating film 202 is silicon dioxide formed by thermal CVD using a cold wall type low pressure CVD apparatus using silane and oxygen as source gases.

Next, the metal wiring layer 201 is formed on the insulating film 202 and the aluminum alloy wiring layer 20 formed on the insulating film 202.
The connection hole with 5 is opened. The method of opening the holes is to apply a photoresist to the entire surface of the wafer, expose and transfer the pattern of the connecting holes, and develop it, and then use the resist as a mask and the reactive ion etching method using carbon tetrafluoride and oxygen as etching gas. Make a hole. The diameter of the connection hole is 0.6 μm.

Then, titanium 203 having a film thickness of 0.1 μm is formed in the connection hole and on the entire surface of the insulating film 202 by a magnetron sputtering method, and tungsten having a film thickness of 0.4 μm is formed on the entire surface of the titanium 203. Tungsten 2
Reference numeral 04 is formed by a thermal CVD method using a cold wall type low pressure CVD apparatus using tungsten hexafluoride and hydrogen as source gases. Note that tungsten 204 formed by a thermal CVD method has poor adhesion to silicon dioxide which is the insulating film 202, and when tungsten 204 is deposited on the insulating film 202, film peeling easily occurs. In addition, titanium 203 and tungsten 20 formed by the thermal CVD method
Adhesion with No. 4 is good. Therefore, tungsten 20
In order to prevent the film peeling of No. 4, titanium 203 is formed on the entire surface of the insulating film 202 by magnetron sputtering, and then tungsten 204 is formed on the entire surface of the titanium 203.
Deposit.

Further, the reactive ion etching apparatus is used to completely remove the tungsten and titanium existing outside the contact hole. Sulfur hexafluoride is used for etching tungsten, and chlorine is used for etching titanium. In both cases, the end point of etching is detected by the change in the emission intensity of plasma and the connection is made without using a mask such as a resist. Etching is performed so that titanium 203 and tungsten 204 remain only in the holes.

Finally, the tungsten 204 and the insulating film 2
After forming an aluminum alloy thin film with a film thickness of 0.4 μm on the entire surface of 02 by magnetron sputtering, a photoresist is applied on the entire surface of the wafer, the wiring pattern is exposed and transferred, and developed, and the resist is used as a mask for etching gas. Etching is performed using chlorine using a reactive ion etching apparatus, and then the photoresist is peeled off to form an aluminum alloy wiring layer 205.

[0008]

However, since the aluminum alloy and tungsten are in direct contact with each other in the above-mentioned technique, when a current is passed from the aluminum alloy to the tungsten or from the tungsten to the aluminum alloy, electromigration causes A phenomenon occurs in which the atoms of A cross over the interface between the aluminum alloy and tungsten and flow into the other. Due to the movement of the atoms, a void is generated in the aluminum alloy or tungsten, and finally there is a problem that the aluminum metal wiring or the tungsten is disconnected. Therefore, the present invention is intended to solve such a problem, and its purpose is to connect a semiconductor layer or a metal wiring layer to an aluminum alloy wiring layer located above the semiconductor layer or the metal wiring layer. In a semiconductor device having a structure in which at least tungsten is filled in the hole, a semiconductor device having excellent electromigration resistance in the vicinity of an interface between tungsten and an aluminum alloy wiring layer and a method for manufacturing the same are provided. .

[0009]

The semiconductor device of the present invention comprises:
At least tungsten is filled in a connection hole that connects the semiconductor layer or the metal wiring layer and the aluminum alloy wiring layer located above the semiconductor layer or the metal wiring layer, and the tungsten and the aluminum alloy wiring layer are connected to each other. An alloy layer made of at least aluminum and tungsten is present between the two. The method for manufacturing a semiconductor device of the present invention is one of the following two methods. The first manufacturing method includes a step of forming an insulating film on a semiconductor layer or a metal wiring layer, a step of forming a connection hole in the insulating film, a step of filling the connection hole with tungsten, the tungsten and the insulating layer. The method is characterized by including a step of forming an aluminum alloy wiring layer on the film and a step of forming an alloy layer of aluminum and tungsten between the tungsten and the aluminum alloy wiring layer by heating and holding. A second manufacturing method is a step of forming an insulating film on a semiconductor layer or a metal wiring layer, a step of forming a connection hole in the connection hole, a step of filling the connection hole with tungsten, the tungsten and the insulation By forming the aluminum alloy wiring layer on the film while heating, the formation of the aluminum alloy wiring layer and the formation of the alloy layer of aluminum and tungsten between the tungsten and the aluminum alloy wiring layer are simultaneously performed. It is characterized by including the step of performing.

[0010]

EXAMPLES Examples of the present invention will be described in detail below. 1A to 1H show cross-sectional views of respective steps in the case of connecting the metal wiring layer and the aluminum alloy wiring layer in the order of the steps. 101 is a metal wiring layer, 102 is an interlayer insulating film, 103
Is titanium, 104 is tungsten, 105 is an aluminum alloy wiring layer, and 106 is an alloy layer made of aluminum and tungsten. First, the insulating film 102 having a thickness of 1.0 μm is formed on the metal wiring layer 101 having a thickness of 0.4 μm. The insulating film 102 is silicon dioxide formed by a thermal CVD method using a cold wall type low pressure CVD apparatus using silane and oxygen as source gases (FIG. 1).
(See (a)).

Next, a connection hole between the metal wiring layer 101 and the aluminum alloy wiring layer 105 formed on the insulating film is opened in the insulating film 102. The method of opening the holes is to apply a photoresist to the entire surface of the wafer, expose and transfer the pattern of the connecting holes, and develop it, and then use the resist as a mask and the reactive ion etching method using carbon tetrafluoride and oxygen as etching gas. Make a hole. The diameter of the connection hole is 0.6 μm (see FIG. 1 (b)).

Then, a titanium film 103 having a thickness of 0.1 μm is formed in the contact hole and on the entire surface of the insulating film 102 by a magnetron sputtering method (see FIG. 1C).

Next, a tungsten film having a thickness of 0.4 μm is formed on the entire surface of the titanium 103. Tungsten 1
Reference numeral 04 is formed by a thermal CVD method using a cold wall type low pressure CVD apparatus using tungsten hexafluoride and hydrogen as source gases. Note that tungsten 104 formed by a thermal CVD method has poor adhesion to silicon dioxide which is the insulating film 102, and thus when the tungsten 104 is deposited over the insulating film 102, film peeling easily occurs. In addition, titanium 103 and tungsten 104 formed by a thermal CVD method
Adhesion with is good. Therefore, tungsten 104
In order to prevent the film peeling, the titanium 103 is formed on the entire surface of the insulating film 102 by the magnetron sputtering method, and then the tungsten 104 is deposited on the entire surface of the titanium (see FIG. 1D).

Further, the reactive ion etching apparatus is used to completely remove the tungsten and titanium existing outside the connection hole. Sulfur hexafluoride is used for etching tungsten, and chlorine is used for etching titanium. In both cases, the end point of etching is detected by the change in the emission intensity of plasma and the connection is made without using a mask such as a resist. Etching is performed so that titanium 103 and tungsten 104 remain only in the holes (see FIG. 1E).

Next, the tungsten 104 and the insulating film 10 are formed.
An aluminum alloy thin film having a film thickness of 0.4 μm is formed on the entire surface of 3 by magnetron sputtering. The temperature of the silicon wafer substrate during film formation is approximately 150 ° C. to 250 ° C. (see FIG. 1 (f)).

Next, this wafer is subjected to an electric resistance furnace.
By heating for a certain period of time, mutual diffusion occurs at the interface between the tungsten 104 and the aluminum alloy wiring 105, and the alloy layer 106 made of aluminum and tungsten.
Is generated. The composition of the alloy layer 106 composed of aluminum and tungsten depends on the temperature and the heating time, but in order to suppress the movement of aluminum atoms and tungsten atoms during energization, the intermetallic compound WAl _{12 of} tungsten and aluminum must be present. Is desirable. Further, when heating is performed at an excessively high temperature for a long time, the diffusion distance of aluminum and tungsten becomes long, a solid solution is formed over a wide range, and the wiring resistance increases. FIG. 3 shows the relationship between the holding time and the thickness of the WAl ₁₂ layer in the heat treatment for forming the alloy layer of aluminum and tungsten. According to this, it is known that in order to form WAl ₁₂ having a thickness of 0.1 μm, it is necessary to hold it for 30 minutes even if the heating temperature is 550 ° C. If the holding time is 60 minutes or more at any processing temperature, WAl
₁₂ grows slower. Furthermore, considering that the melting point of aluminum is 660 ° C., the processing temperature is 450
C. to 550.degree. C., and a treatment time of 20 minutes to 60 minutes is suitable (see FIG. 1 (g)).

Finally, a photoresist is applied to the entire surface of the wafer, the wiring pattern is transferred by exposure and developed, and then chlorine is used as an etching gas with this resist as a mask to perform etching with a reactive ion etching apparatus, and then the photoresist is used. The aluminum alloy wiring layer 20
5 is formed (see FIG. 1 (h)).

Another embodiment is as follows.
After opening a connection hole in the insulating film deposited on the metal wiring layer,
Titanium and then tungsten are formed, and the tungsten and titanium existing outside the contact hole are completely removed by reactive ion etching. Next, an aluminum alloy thin film having a thickness of 0.4 μm is formed on the entire surface of tungsten and the insulating film by magnetron sputtering. By setting the temperature of the silicon wafer substrate during the film formation to 500 ° C. to 600 ° C., an aluminum alloy thin film is deposited on the tungsten and the insulating film, and at the same time, aluminum and tungsten are formed by mutual diffusion between tungsten and the aluminum alloy. An alloy layer consisting of is formed. Finally, using a resist as a mask and using chlorine as a mask, etching is performed by a reactive ion etching apparatus to form an aluminum alloy wiring layer.

Further, when the electromigration resistance near the interface between the tungsten and the aluminum alloy wiring layer was compared by an acceleration test, it was found that 0.0 was obtained between the tungsten and the aluminum alloy wiring layer using the method of this embodiment.
The life when a WAl ₃ layer of 2 μm or more is formed is WA
It has been known to increase about two times the case where l _3-layer does not exist at all.

Even when single crystal silicon, polycrystalline silicon, amorphous silicon or refractory metal silicide is present instead of the metal wiring layer existing under the contact hole, the same process as in the above embodiment can be performed. Is.

Further, in the above-mentioned embodiment, among the titanium formed as the adhesion layer when tungsten is deposited by the thermal CVD method, titanium existing outside the connection hole is removed by etching with chlorine, which is carried out subsequent to the etching of tungsten. However, after etching the tungsten, while leaving the titanium remaining, deposit the aluminum alloy on the titanium, etch the aluminum alloy with chlorine using the resist as a mask, and form the aluminum alloy wiring layer when forming the aluminum alloy wiring layer. It is also possible to etch titanium subsequent to etching.

As the adhesion layer in the case of depositing tungsten by the thermal CVD method, in addition to titanium shown in the above-mentioned embodiment, titanium nitride formed by the sputtering method, titanium tungsten, tungsten, and the CVD method are used. It is also possible to use the filmed titanium nitride in a single layer. In addition, it is also possible to select two or more kinds of titanium, titanium nitride, titanium tungsten, tungsten formed by the sputtering method, and titanium nitride formed by the CVD method and use them as a laminated film.

Further, in the above-described embodiment, titanium is formed by magnetron sputtering in the connection hole and on the entire surface of the insulating film, and tungsten is formed on the entire surface of this titanium. Then, tungsten and titanium are etched to form the inside of the connection hole. Only tungsten and titanium remained, but the selection C
By using the VD method, it is possible to form tungsten only in the connection hole. If this selective CVD method is used, an adhesion layer such as titanium is unnecessary. To perform selective CVD, silane and tungsten hexafluoride are used as source gases, and the flow rate ratio of these gases is approximately 1: 1.
It is necessary to form a film at a pressure of 1 torr or less and a temperature of 200 ° C to 350 ° C.

[0024]

According to the present invention described above, at least tungsten is contained in the connection hole that connects the semiconductor layer or the metal wiring layer and the aluminum alloy wiring layer located above the semiconductor layer or the metal wiring layer. In a semiconductor device having a filled structure, an electro-luminescence near the interface between tungsten and an aluminum alloy wiring layer is achieved by forming an alloy layer made of aluminum and tungsten between the tungsten and the aluminum alloy wiring layer. This has the effect of improving migration.

[0025]

[Brief description of drawings]

1A to 1H are cross-sectional views of each step of a joining portion between a metal wiring layer and an aluminum alloy wiring layer in an embodiment of the present invention.

FIG. 2 is a sectional view of a joint portion between a metal wiring layer and an aluminum alloy wiring layer in a conventional method.

FIG. 3 is a graph showing the relationship between the holding time and the thickness of the WAl ₁₂ layer in the heat treatment for forming the alloy layer of aluminum and tungsten.

[Explanation of symbols]

101 ... Metal wiring layer 102 ... Insulating film 103 ... Titanium 104 ... Tungsten 105 ... Aluminum alloy wiring layer 106 ... Alloy layer made of aluminum and tungsten 201 ... Metal wiring layer 202 ... Insulating film 203 ... Titanium 204 ... Tungsten 205 ... Aluminum alloy wiring layer

Claims (5)

[Claims] 1. A connection hole for connecting a semiconductor layer or a metal wiring layer to an aluminum alloy wiring layer located above the semiconductor layer or the metal wiring layer is filled with at least tungsten, and the tungsten and the aluminum are provided. A semiconductor device characterized in that an alloy layer made of at least aluminum and tungsten exists between the alloy wiring layer and the alloy wiring layer. 2. A step of forming an insulating film on a semiconductor layer or a metal wiring layer, and a step of forming a connection hole in the insulating film,
A step of filling the connection hole with tungsten, a step of forming an aluminum alloy wiring layer on the tungsten and the insulating film, and a step of heating and holding the aluminum and tungsten between the tungsten and the aluminum alloy wiring layer. And a step of forming an alloy layer of 3. A step of forming an insulating film on a semiconductor layer or a metal wiring layer, and a step of forming a connection hole in the insulating film,
Forming the aluminum alloy wiring layer by filling the connection hole with tungsten and forming an aluminum alloy wiring layer on the tungsten and the insulating film while heating the tungsten and the aluminum alloy wiring. A method for manufacturing a semiconductor device, comprising the step of simultaneously forming an alloy layer made of aluminum and tungsten between the layer and the layer. 4. The method of manufacturing a semiconductor device according to claim 2, wherein the heating temperature is 450 ° C. to 550 ° C. and the holding time is 20 minutes to 60 minutes. 5. The method of manufacturing a semiconductor device according to claim 3, wherein the heating temperature is 500 ° C. to 600 ° C.