JPH0427163A - Semiconductor device and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Regarding a semiconductor device, particularly a semiconductor device with an improved diffusion prevention layer between a silicon substrate and an aluminum or aluminum alloy wiring layer, and a method for manufacturing the same, the contact resistance between the substrate and the wiring is disclosed. An object of the present invention is to provide a semiconductor device and a method for manufacturing the same that sufficiently prevents mutual diffusion between a substrate and wiring while ensuring device reliability and production efficiency without increasing The layer for preventing diffusion between the silicon substrate and the wiring layer of aluminum or aluminum alloy on the substrate is made of a high melting point metal or an alloy mainly composed of a high melting point metal, at the bottom and top of the layer thickness. The manufacturing method of the present invention is made of these nitrides, and the intermediate part of the layer thickness is made of a high melting point metal, an alloy mainly composed of a high melting point metal, or a nitride of these metals containing oxygen. In order to form a layer on the silicon substrate that prevents diffusion between the substrate and the wiring layer of aluminum or aluminum alloy, a mixed gas atmosphere of an inert gas and a nitriding gas is placed on the substrate heated to a high temperature. A process of sputtering a high melting point metal, an alloy mainly composed of a high melting point metal, or a nitride thereof in a medium or inert gas atmosphere, and in the middle of the sputtering, introducing oxygen into the atmosphere and then stopping the introduction. The configuration is configured to perform the process of

[Industrial application field]

The present invention relates to a semiconductor device, and particularly to a semiconductor device in which a diffusion prevention layer between a silicon substrate and an aluminum or aluminum alloy wiring layer is improved, and a method for manufacturing the same.

[Conventional technology]

Currently, the main wiring material for LSI is A#, -1%81
Aluminum-silicon alloys such as

However, it is known that supersaturated silicon in the wiring alloy precipitates at the contact portion between the substrate and the wiring when various heat treatments are performed during wiring formation and subsequent processes. In miniaturized devices, such precipitated silicon significantly increases the contact resistance between the substrate and wiring. Therefore, in recent devices with advanced miniaturization, pure aluminum or Al, which does not contain silicon, is used as the wiring material.
An aluminum/copper alloy such as -2% Cu is used.

In that case, a diffusion prevention layer is provided between the substrate and the wiring layer in order to prevent mutual diffusion of aluminum in the wiring material and silicon in the substrate.

Materials for forming the diffusion prevention layer include high-melting point metals such as titanium, zirconium, hafnium, tungsten and tantalum, alloys containing high-melting point metals as main components such as tungsten-titanium alloys, and nitrides of these metals. However, nitrides are considered to be superior in terms of diffusion prevention properties.

The nitride diffusion prevention layer is generally formed by sputtering. However, simply sputtering nitride as usual does not provide sufficient diffusion prevention properties. As an essential method to improve diffusion prevention properties, (1) Sputtering is carried out by introducing oxygen into a mixed gas atmosphere of an inert gas and a nitriding gas or into an inert gas atmosphere while maintaining the silicon substrate at a high temperature. method (Japanese Patent Application No. 638,564 filed by the present inventors), (2) After forming a diffusion prevention layer made of nitride by sputtering, it is taken out into an open flame and then heated in a trace oxygen atmosphere in an electric furnace for 450~ 60
There is a method of performing heat treatment at 0°C.

In all of the above methods, grain boundary diffusion within the nitride layer is suppressed by containing oxygen in the entire nitride layer or the surface layer, and it is thought that the diffusion prevention properties of the nitride layer as a whole are improved.

However, in the above conventional method (1), when the amount of oxygen required to obtain sufficient diffusion prevention property is added, the contact resistance between the substrate and the wiring increases, and the failure life of the wiring (MT F
There was a problem in that the mean time to failure) became short and the reliability of the device decreased. In addition, with conventional method (2), the process of taking out the device while it is in the oven and transferring it to the electric furnace is increased, the troublesome handling of the substrate, and the adhesion of dust on the substrate, etc., reduce the productivity of the device. There were also problems in terms of reliability.

[Problem to be solved by the invention]

An object of the present invention is to provide a semiconductor device and a method for manufacturing the same that sufficiently prevents mutual diffusion between the substrate and the wiring, while ensuring reliability and production efficiency of the device without increasing the contact resistance between the substrate and the wiring. With the goal.

[Means to solve the problem]

The above object, according to the present invention, is such that a layer for preventing diffusion between a silicon substrate and an aluminum or aluminum alloy wiring layer on the substrate is formed of a high-melting point metal or Consisting of an alloy whose main component is a high-melting point metal or a nitride thereof, and the middle part of the layer thickness is made of a high-melting point metal, an alloy whose main component is a high-melting point metal, or a nitride thereof containing oxygen. This is achieved by a semiconductor device characterized by:

The refractory metals, alloys mainly composed of refractory metals, or nitrides thereof in the top, bottom, and middle parts may be different materials for these three parts, or the same for the three parts or any two parts. The material may be

There may be other layers consisting of refractory metals, alloys mainly composed of refractory metals, or nitrides thereof between the top and middle parts, and between the bottom and middle parts, but these layers without other layers may be present. It is preferable to keep it concise and consist of three parts. In this case, the diffusion prevention layer is a three-layered layer consisting of a lower and upper part of a refractory metal, an alloy mainly composed of a refractory metal, or a nitride thereof, and the intermediate part in which the lower material contains oxygen. It becomes a structure. In this three-layer structure, it is more simple and desirable for the upper and lower parts to be made of the same material. In this case, it is desirable that the upper and lower parts are made of a material with high diffusion prevention properties, most preferably titanium nitride.

According to the present invention, the semiconductor device of the present invention having the above-mentioned three-layered diffusion preventive layer includes forming a layer on a silicon substrate to prevent diffusion between the substrate and a wiring layer of aluminum or aluminum alloy. sputtering a high melting point metal, an alloy mainly composed of a high melting point metal, or a nitride thereof on the substrate heated to a high temperature in a mixed gas atmosphere of an inert gas and a nitriding gas or in an inert gas atmosphere. and a step of introducing oxygen into the atmosphere and then stopping the introduction during the sputtering.

During the oxygen introduction period, sputtering may be continued or sputtering may be interrupted. Control of the treatment process can be simplified by interrupting sputtering and performing only the oxidation reaction independently.

[For production]

The semiconductor device of the present invention improves diffusion prevention properties by containing oxygen in the middle part of the thickness of the diffusion prevention layer to prevent grain boundary diffusion within the diffusion prevention layer. The lower layer is made of a high-melting point metal, an alloy mainly composed of a high-melting point metal, or a nitride of these metals, thereby preventing an increase in contact resistance and a decrease in the life of the wiring due to oxygen addition. In other words, even if a diffusion prevention layer is formed by introducing oxygen in an amount that provides a sufficient diffusion prevention effect, the lower part of the diffusion prevention layer on the substrate side and the upper part of the diffusion prevention layer on the wiring side do not contain oxygen. , neither the increase in contact resistance nor the shortening of the lifespan due to wiring breakage, which conventionally occur with the addition of oxygen, does not occur.

According to the method for manufacturing a semiconductor device of the present invention, the diffusion prevention layer having the above structure can be formed in the same sputtering device, thereby avoiding the increase in the transportation steps between processing devices and the complexity of handling as in the past. It is possible to manufacture semiconductor devices with high production efficiency and high reliability by preventing contamination caused by dust in the atmosphere.

In the present invention, the aluminum alloy may be any aluminum-based alloy used for wiring of semiconductor devices.
I! -Aluminum-silicon alloy such as 1%Si, Al
-Aluminum-copper alloys such as 2% Cu are included.

High melting point metals, alloys mainly composed of high melting point metals, or nitrides thereof, which form the lowermost and uppermost parts of the diffusion prevention layer, or high melting point metals or high melting point metals, which contain oxygen and form the middle part of the diffusion prevention layer. An alloy whose main component is a melting point metal or a nitride thereof is a high melting point metal, an alloy whose main component is a high melting point metal, or a nitride thereof that has the function of preventing mutual diffusion between the silicon substrate and wiring. . Conventionally used materials include high melting point metals such as titanium, zirconium, hafnium, tungsten and tantalum, alloys whose main components are high melting point metals such as tungsten-titanium alloys, and nitrides of these metals. Titanium nitride is advantageous because it has the highest diffusion prevention properties.

In the method of the present invention, a gas such as argon that does not substantially cause a chemical reaction during sputtering is used as the inert gas, and a gas that exhibits nitriding properties on the sputtered layer during sputtering, such as nitrogen, is used as the nitriding gas. use When the layer to be formed by sputtering is a layer of a nitride of a high melting point metal or a nitride of an alloy whose main component is a high melting point metal, sputtering is performed in a mixed gas atmosphere of an inert gas and a nitriding gas, When the layer to be formed by sputtering is a layer of a refractory metal or an alloy whose main component is a refractory metal, sputtering is performed in an inert gas atmosphere.

Hereinafter, the present invention will be explained in more detail by way of examples with reference to the accompanying drawings.

〔Example〕

FIG. 1 shows an example in which the present invention is applied to a contact portion (electrode structure) between a pure aluminum wiring layer and a silicon substrate.

In the figure, 1 is, for example, a P-type Si substrate, 2 is a silicon oxide film, 3 is, for example, an n-type substrate diffusion layer, 4 is a titanium layer for making ohmic contact with the substrate diffusion layer, and 5 is a titanium layer according to the present invention. 6 is an aluminum wiring layer, and 7 is a contact hole. Diffusion prevention layer 5
consists of a lower part 51 and an upper part 53 made of titanium nitride, and an intermediate part 52 made of titanium nitride containing oxygen.

The electrode structure of FIG. 1 is formed as follows.

First, after forming an n diffusion layer 3 on a silicon substrate 1, a silicon oxide film having a thickness of, for example, 1 μm is formed on the diffusion layer 3, and after patterning, a contact hole 7 is formed by dry etching.

Next, after removing the natural oxide film in the contact hole 7 by wet treatment using acid, a titanium layer 4 with a thickness of 200 μm is formed by sputtering in order to make contact with the substrate diffusion layer 3 in the contact hole 7. do. The substrate temperature was 450°C, and the sputtering conditions were DC power 50.
0W, argon atmosphere (flow rate 3Qsccm, pressure 2.Q
mTorr). Next, while maintaining the substrate temperature, the atmospheric gas was changed to argon gas (20%
secm) and nitrogen gas (80 secm) (with a total flow rate of 1001005e), a lower titanium nitride layer 51 with a thickness of 500 mm is formed.

Next, after turning off the DC power for sputtering, the upper surface layer 52 of the lower titanium nitride layer 51 is introduced into the mixed atmosphere for 30 seconds at an amount of 80 SCCm (80% flow rate of the total atmospheric gas). Oxidize. Next, the atmospheric gas is switched again to the above-mentioned argon/nitrogen mixed atmosphere to form the upper titanium nitride layer 53 with a thickness of 500 wafers.

This completes the formation of the diffusion prevention layer 5 (1000 layers thick). An aluminum wiring layer 6 is formed on this diffusion prevention layer 5.
The formation of the electrode structure shown in FIG. 1 is completed.

In the above steps, the steps after the formation of the titanium layer 4 are performed in the same sputtering apparatus from beginning to end. Therefore, there is no need to take it out into the atmosphere after forming the diffusion prevention layer and transfer it to another heat treatment equipment for heat treatment as in the conventional method, and there is no need to worry about the transportation process or the hassle of handling the substrate, and there is no need to worry about dust adhering to the substrate. No such problems arise.

The obtained electrode structure shown in FIG. 1 maintained sufficient diffusion prevention properties even after heat treatment at 500° C., and showed a low and stable contact resistance.

In this example, the upper material and the lower material are titanium nitride (T
Although nitrides of high-melting point metals are generally preferred, for example, zirconium nitride (ZrN), hafnium nitride (HfN), tungsten nitride (WN), molybdenum nitride (MoN) can be used instead of titanium nitride. ),
It can be replaced with tantalum nitride (TaN) or the like.

[Conventional example]

For comparison, an electrode structure provided with a conventional diffusion prevention layer shown in FIG. 2 was formed by a conventional method.

The electrode structure itself in the same figure is essentially the same as the electrode structure in the embodiment shown in FIG.
00 persons) The entire structure was formed in an atmosphere containing oxygen. However, the amount of oxygen introduced was varied to various levels.

Other conditions are the same as in the example.

Regarding the obtained electrode structure, 450°C x 3Q minutes + 500
Junction leak current value after heat treatment for 60 minutes at °C (
-5V) is shown in Figure 3, the contact resistance between the board/wiring is shown in Figure 4, and the wiring rupture life (MTF) is shown in Figure 5.
The figure shows the relationship with the amount of oxygen introduced.

From FIG. 3, it can be seen that sufficient diffusion prevention properties can be obtained by setting the amount of oxygen introduced to 9%. However, as shown in Fig. 4, the contact resistance already increases when the amount of oxygen introduced is 7%, and as shown in Fig. 5, the contact resistance increases even when the amount of oxygen introduced is 5%.
As a result, the wiring rupture life (MTF) is significantly shortened. As a result, it can be seen that in the conventional diffusion prevention layer, if a sufficient diffusion prevention property is to be obtained, an increase in contact resistance and a shortened lifespan due to wiring breakage are inevitable.

〔Effect of the invention〕

As explained above, according to the present invention, a semiconductor device can sufficiently prevent mutual diffusion between the substrate and wiring while ensuring device reliability and production efficiency without increasing contact resistance between the substrate and wiring. is obtained.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing an example of an electrode structure in which the diffusion prevention layer of the present invention is applied to the contact area between an aluminum wiring layer and a silicon substrate, and Figure 2 is a cross-sectional view showing an example of an electrode structure in which a conventional diffusion prevention layer is provided. Figure 3 is a graph showing junction leakage current values for various amounts of oxygen introduced, Figure 4 is a graph showing changes in substrate/wiring contact resistance with respect to the amount of oxygen introduced, and Figure 5 is a graph showing the amount of oxygen introduced. FIG. 1: P-type silicon substrate, 2: silicon oxide film, 3: n-type substrate diffusion layer, 4: titanium layer, 5.5°: diffusion prevention layer, 51: lower titanium nitride layer, 52: middle oxygen-containing layer layer, 53: upper titanium nitride layer, 6: aluminum wiring layer, 7: contact hole.

Claims (1)

[Claims] 1. The layer for preventing diffusion between the silicon substrate and the wiring layer of aluminum or aluminum alloy on the substrate is made of a high melting point metal or a high melting point metal at the bottom and top of the layer thickness. or nitrides thereof,
1. A semiconductor device characterized in that an intermediate portion of the layer thickness is made of a high melting point metal, an alloy containing a high melting point metal as a main component, or a nitride thereof containing oxygen. 2. The diffusion prevention layer consists of a lower and upper part of a high melting point metal, an alloy mainly composed of a high melting point metal, or a nitride thereof, and the middle part in which the lower material contains oxygen. The semiconductor device according to claim 1, characterized in that: 3. The semiconductor device according to claim 2, wherein the upper part and the lower part are made of the same material. 4. The semiconductor device according to claim 3, wherein the material of the upper part and the lower part is titanium nitride. 5. In order to form a layer on the silicon substrate that prevents diffusion between the substrate and the wiring layer of aluminum or aluminum alloy, a mixed gas of an inert gas and a nitriding gas is applied to the substrate heated to a high temperature. A step of sputtering a high melting point metal, an alloy mainly composed of a high melting point metal, or a nitride thereof in an atmosphere or an inert gas atmosphere, and during the sputtering, introducing oxygen into the atmosphere. A method of manufacturing a semiconductor device, comprising a step of stopping. 6. The method according to claim 5, wherein the sputtering is interrupted during the oxygen introduction period. 7. The method according to claim 5 or 6, wherein the sputtering is performed by sputtering titanium nitride.