JPH0430423A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture a semiconductor device wherein the increase in the contact resistance and the disconnection hardly occur even after the heat treatment by a method wherein the oxygen to enhance the barrier effect is contained in a barrier metal. CONSTITUTION:The oxygen contained in a barrier metal layer 6 comprising TiN to be formed by sputtering Ti in the gas atmosphere mixed with Ar gas, N2 gas and CO2 gas is coupled with titanium, nitrogen or carbon. Resultantly, the interfaces between a Ti layer 5 and the layer 6 as well as between the layer 6 and an Al layer 7 are hardly oxidized due to the diffusion of oxygen contained in the layer 6 while the increase in the contact resistance and the disconnection can hardly occur further enhancing the barrier effect even if the layer 6 containing oxygen is heat-treated. Accordingly, the barrier metal layer 6 having the sufficient barrier effect and making thermally stable contact resistance not to deteriorate the reliability on the Al layer 7 as the upper layer wiring can be formed so that the title semiconductor device giving excellent performances may be manufactured.

Description

[Detailed Description of the Invention] [Summary] Regarding a semiconductor device and its manufacturing method, even if the amount of oxygen added to improve the barrier effect in a barrier metal layer is increased, increase in contact resistance and disconnection can be prevented. It is an object of the present invention to provide a semiconductor device and a method for manufacturing the same, which can improve the barrier effect and further reduce the number of steps, the troublesome substrate handling, and the adhesion of dust on the substrate. an insulating film formed on the surface of the silicon substrate; a contact window selectively formed on the insulating film to expose the surface of the silicon substrate; and a contact window extending from the surface of the silicon substrate exposed at the bottom of the contact window. a high melting point metal layer covering the side surfaces and extending on the surface of the insulating film; a high melting point metal nitride layer formed overlapping the high melting point metal layer at least at the bottom of the contact window; It has a region overlapping the metal nitride layer, is formed to extend from inside the contact window to outside the contact window, and has a wiring layer made of aluminum or an aluminum alloy, and has a wiring layer in the high melting point metal layer. In order to prevent the silicon substrate and the wiring layer from reacting with each other, nitrogen, carbon, and oxygen are mixed together, or a high melting point metal is mixed with an inert gas, nitrogen By sputtering in a mixed gas atmosphere of gas and gas containing carbon and oxygen, a barrier metal layer made of high melting point metal nitride is formed to prevent a reaction between the silicon substrate and the wiring layer made of aluminum or aluminum alloy. Configure to form.

[Industrial application field]

The present invention relates to a semiconductor device and a method for manufacturing the same, and more particularly to a method for forming a barrier metal layer that prevents diffusion of A1 and Si between a silicon substrate and a wiring layer made of aluminum or an aluminum alloy.

Currently, the main wiring materials for LSI are aluminum alloys, such as A
ff-1% Si is used. This Aff-1%S
The aluminum alloy wiring layer consisting of
The idea is to alleviate the mutual diffusion between Al of the aluminum alloy wiring layer and Si of the silicon substrate by containing AI! When using wiring, it is known that if such heat treatment is repeated during the formation of the A1 alloy wiring layer and in subsequent processes, supersaturated silicon in the aluminum alloy wiring layer will precipitate at the contact area between the silicon substrate and the aluminum alloy wiring layer. It is being For this reason, there is a drawback in that the contact resistance between the silicon substrate and the aluminum alloy wiring layer increases significantly as the device becomes finer.

Furthermore, as wiring materials in recent miniaturized structures, aluminum that does not contain silicon, such as pure aluminum or A1-2% Cu, which has particularly excellent electromigration resistance, is used. Furthermore, in this case, a barrier metal layer, such as a titanium nitride (TiN) film, is provided between the wiring layer and the silicon substrate to prevent mutual diffusion between Al in the wiring layer made of aluminum or aluminum alloy and Si in the silicon substrate. is used. However, the barrier metal layer made of TiN formed under normal sputtering conditions (for example, Ti target, N2 gas and Ar gas atmosphere) has a drawback in that the diffusion prevention effect is not sufficient.

Therefore, there is a need for a semiconductor device and a method for manufacturing the same that can form a barrier metal layer that has even better diffusion prevention effects.

[Conventional technology]

Conventionally, methods for improving the diffusion prevention effect between a Si substrate and a wiring layer made of A1 or A1 alloy include: 1. Forming a barrier metal layer made of TiN by sputtering in an oxygen-containing atmosphere while maintaining the substrate at a high temperature ( After forming a barrier metal layer made of TiN under normal sputtering conditions (for example, T1 target, Ar gas and NZ gas atmosphere), the vacuum is broken and the film is taken out into the atmosphere and placed in an electric furnace. , and a method of performing heat treatment at 450 to 500° C. in a trace amount of oxygen atmosphere.

In each of these methods, oxygen is introduced into the barrier metal layer made of TiN in order to improve the barrier effect of the barrier metal layer.

[Problem to be solved by the invention]

First, the problems when using the manufacturing method (2) described above will be specifically explained using the drawings.

Figure 5 shows T formed by adding oxygen to the sputtering atmosphere.
FIG. 3 is a diagram showing a wiring contact structure using a barrier metal layer made of iN. In FIG. 5, 31 is, for example, a p-type silicon substrate, and 32 is a silicon substrate 31 with, for example, 70
For example, an n-type diffusion layer is formed by implanting As' at eV and 4×10 cm - , 33 is an insulating film made of SiO□, etc., and has a thickness of, for example, 1.0 μm, and 34 is formed on the insulating film 33. 35 is a Ti film with a thickness of, for example, 200 μm, and 36 is a TiN film.
For example, a barrier metal layer with a film thickness of 1000 people, etc.
37 is an A1 layer made of pure A1 and having a thickness of, for example, 1.0 μm.

Next, Fig. 6 shows the sample structure shown in Fig. 5 at 450°C x 3.
It is a figure which shows the frequency of a junction leak current value after heat processing of 0 minute + 500 degreeC x 60 minutes. Here, minus 'l'1 is placed on the silicon substrate 31 side of the sample shown in FIG.
The leakage current is measured by applying a positive voltage to the wiring layer side consisting of N35, barrier metal layer 36 and A1 layer 37.
It shows that the smaller the leakage current is, the better the barrier properties are. Measurements were made for 49 samples each. 6th
Figure (a) shows the case where 02 gas is not added, and Figure 6 (b)
) is the case where the 0° gas addition amount is 5% (4 seconds) at a flow rate, and FIG. 6(c) is the case where the 02 gas addition amount is 9% (7 seconds) at a flow rate. It can thus be seen that by increasing the amount of 0° gas added, the leakage current can be reduced and the barrier properties can be improved. It can be seen that leakage can be sufficiently suppressed by adding oxygen at a flow rate ratio of 9% or more.

Next, FIG. 7 is a diagram showing the relationship between contact resistance, oxygen addition amount, and various heat treatment conditions. It can be seen from FIG. 7 that the contact resistance increases as the amount of oxygen added increases, and when 9% (7 seconds) of oxygen is added, it gradually increases as heat treatment is added.

Next, Figure 8 shows the MTF (Mean) of the upper layer aluminum wiring.
FIG. 4 is a diagram showing the relationship between the time to failure and the amount of oxygen added. From FIG. 8, MTF decreases as the amount of oxygen added increases. This is TiN with oxygen added.
A1 layer 37 is used as the upper layer.
This shows that when the barrier metal layer 36 is formed, as the oxygen concentration in the barrier metal layer 36 increases, the wire becomes more likely to break.

As explained above, the barrier metal layer made of TiN formed by adding oxygen to the sputtering atmosphere has the advantage of improving the barrier effect, and the barrier effect improves as the amount of oxygen added increases.

However, as explained in FIGS. 7 and 8, when the amount of oxygen added increases, the contact resistance increases, and the wire becomes more likely to break, causing the upper layer A7! There is a problem in that it causes a decrease in the reliability of N37. This is thought to be due to oxygen in the barrier metal layer 36 made of TiN being diffused by the heat treatment, thereby oxidizing the interface with the upper or lower layer.

Next, problems when using the manufacturing method (2) described above will be explained.

This manufacturing method has the advantage that the barrier effect can be improved because an oxide layer is formed on the barrier metal layer made of TiN, but since it is first taken out to the atmosphere and transferred into an electric furnace, Problems such as an increase in the number of steps, troublesome substrate handling, and adhesion of dust on the substrate arise. As a result, production efficiency and reliability of semiconductor devices are significantly reduced.

Therefore, the present invention makes it possible to make it difficult to cause an increase in contact resistance and disconnection even if the amount of oxygen added to improve the barrier metal layer is increased, and also to improve the barrier effect. It is an object of the present invention to provide a semiconductor device and a method for manufacturing the same, which can reduce the number of steps, the trouble of handling the substrate, and the adhesion of dust on the substrate.

[Means for Solving the Problems] In order to achieve the object, a semiconductor device according to the present invention includes an insulating film formed on the surface of a silicon substrate, and a contact window selectively formed on the insulating film to expose the surface of the silicon substrate. and a high melting point metal layer formed extending from the silicon substrate surface exposed at the bottom of the contact window to the surface of the insulating film, covering the contact I/window side surface, and at least at the bottom of the contact window. It has a high melting point metal nitride F layer formed overlapping the melting point metal layer, and a region overlapping the high melting point metal nitride layer, and is formed so as to extend from inside the contact window to outside the contact window. or a wiring layer made of an aluminum alloy, and the high melting point metal layer contains nitrogen, carbon, and oxygen elements so that the silicon substrate and the wiring layer do not react with each other. It is a mixture.

In order to achieve the above object, a semiconductor device and a method for manufacturing the same according to the present invention sputter a high melting point metal in a mixed gas atmosphere of an inert gas, a nitrogen gas, and a gas containing carbon and oxygen. Alternatively, a barrier metal layer made of high melting point metal nitride is formed to prevent reactions between wiring layers made of aluminum alloy.

The refractory metals according to the present invention include '[''i, Zr, Hf,
Examples include W, Mo, etc., and the barrier metal layer made of high melting point metal nitride includes TiN, ZrN, HfN, WN,
Examples include MoN. Further, examples of the inert gas include He gas, Ar gas, etc., and examples of the gas containing carbon and oxygen include CO gas, CO□ gas, etc. In addition, the wiring layer made of aluminum alloy contains AI!・Si layer, Al-C
U layer etc. are mentioned.

In the present invention, after forming the barrier metal layer, a wiring layer made of A1 or Af gold alloy may be formed on the barrier metal layer without breaking the vacuum. This is preferable because it can prevent an increase in the number of steps required for handling the substrate, or prevent contamination of the substrate with dust.

In the present invention, when forming the barrier metal layer, a certain amount of gas containing carbon and oxygen (Co, Co2, etc.) may be added throughout the entire layer, or may be added in a pulsed manner or temporarily. It may be. When gas containing carbon and oxygen is added in a pulsed manner or temporarily in this way, carbon and oxygen can be localized in a part of the barrier metal layer, and when added in a constant amount throughout the barrier metal layer. This is preferable because the absolute amount of oxygen in the barrier metal layer can be reduced, and the specific resistance can be made smaller.

[Effect]

First, the effect of claim 10 of the present invention will be explained.

Conventionally, oxygen contained in the barrier metal layer was diffused by heat treatment, which oxidized the interface between the lower layer and the upper layer, resulting in an increase in contact resistance and a decrease in the reliability of the upper layer aluminum. However, as in the present invention, a high melting point metal such as titanium is used as an inert gas such as Ar gas, N2
gas, carbon and oxygen containing gas such as COz
By sputtering in a mixed gas atmosphere, oxygen contained in the barrier metal layer is bonded to titanium, nitrogen, or carbon. Looking at the bond energy between diatomic molecules, C-0 is 256.7 Kcal
/mol and N-0 is 149.7 Kcal/mol, so oxygen becomes more stable by forming a bond with carbon. Therefore, diffusion of oxygen in the barrier metal layer due to heat treatment can be made difficult to occur. Therefore, the interface with the lower layer and the upper layer is less likely to be oxidized due to the diffusion of oxygen in the barrier metal layer, and even if oxygen is contained in the barrier metal layer, increase in contact resistance and disconnection can be prevented. Moreover, the barrier effect can be improved.

Next, the effect of claim 3 of the present invention will be specifically explained using the drawings. Note that claim 2 has been explained as a solution, so a description thereof will be omitted.

As described in the prior art, in order to improve the barrier effect of the barrier metal layer made of TiN, it is necessary to incorporate oxygen into the barrier metal layer. Figure 4 shows the sample shown in Figure 5 at 450'C x 30 minutes + 500°C x 6
FIG. 7 is a diagram showing the frequency of junction leak current value after heat treatment for 0 minutes. FIG. 4(a) shows the case where no CO2 gas is added, and FIG. 4(b) shows the case where the CO2 gas is 9% (flow rate ratio).

From FIG. 4, it can be seen that leakage can be sufficiently suppressed by adding CO2 gas at a flow rate ratio of 9%.

Next, Table 1 shown below shows contact resistance and added CO.
□ This shows the relationship between gas and each heat treatment condition. From Table 1, the contact resistance is greater than when oxygen gas is added.
It is found to be thermally stable.

Table 1 MTF also increased compared to when oxygen gas was added.

As explained above, the barrier metal layer made of TiN formed by adding CO□ gas to the sputtering atmosphere is COz
The barrier effect improves as the amount of gas added increases, and when COz gas is added, a thermally stable contact resistance is obtained, and the reliability of the A1 layer of the upper wiring layer is not likely to deteriorate.

It is also more preferable to use the following method.

For example, A with a high melting point metal such as Ti as an inert gas.
When performing sputtering in a mixed gas atmosphere of CO□ gas or CO gas as a gas containing r gas, N2 gas, carbon and oxygen, for example, by adding CO2 gas or CO gas to the pulse 2 or - time. Carbon and oxygen are localized in a part of the barrier metal layer. In this way, oxygen and carbon are localized in a part of the barrier metal layer, and oxygen in the barrier metal layer is mainly combined with carbon, which has an excellent diffusion prevention effect and reduces the specific resistance of the film. It is possible to lower the temperature and make it difficult for oxygen to diffuse during heat treatment.

〔Example〕

Hereinafter, the present invention will be explained based on the drawings.

FIG. 1 is a diagram illustrating an embodiment of a semiconductor device and a method for manufacturing the same according to the present invention. The manufacturing method in the illustrated example is MO
S) It can be applied to the manufacturing method of transistors, etc.

In FIG. 1, 1 is, for example, a p-type silicon substrate, 2 is, for example, an n-type diffusion layer, 3 is an insulating film made of 5i02, etc., 4 is a contact hole formed in the insulating film 3, and 5 is a diffusion layer 2. Ti layer for making ohmic contact with 6
7 is a barrier metal layer made of TiN, and 7 is an A4 layer.

Next, the manufacturing method will be explained.

First, as shown in FIG. 1(a), for example, As"70
An n-type diffusion N2 is formed in the silicon substrate 1 by ion implantation of KeV, 4 x 1015 cm2, and a film thickness of, for example, 1 μm is formed on the silicon substrate 1 by, for example, the CVD method.
After the insulating film 3 is formed, the insulating film 3 is selectively etched by, for example, dry etching to form a contact hole 4 and expose the silicon substrate l in the contact hole 4.

Next, as shown in FIG. 1(b), the contact hole 4
After removing the natural oxide film within, for example, by wet treatment using hydrofluoric acid, in order to make ohmic contact with the diffusion layer 2, a 71 layer 5 is formed to a thickness of, for example, 200 mm to cover the inside of the contact hole 4 by, for example, sputtering. Form people.

The formation conditions for forming the 71 layer 5 are, for example, a DC power of 50
0W, Ar gas flow rate 30sec, pressure 2.0mT
It is orr.

Next, as shown in FIG. 1(C), A, r gas, N2 gas, and C were heated in the same reaction chamber in which the 71 layer 5 was formed.
A barrier metal layer 6 made of TiN is formed by sputtering Ti in a mixed gas atmosphere of Oz gas.

Then, the A1 layer 7 is formed to cover the 71 layer 5 by sputtering, for example, without breaking the vacuum in the same reaction chamber as the one in which the barrier metal layer 6 was formed (or in another reaction chamber by vacuum transfer). As a result, a wiring contact portion as shown in FIG. 1(d) can be obtained.

That is, in this example, oxygen contained in the barrier metal layer 6 made of TiN formed by sputtering Ti in a mixed gas atmosphere of Ar gas, N2 gas, and CO2 gas is replaced by titanium, nitrogen, or Bonded with carbon. Looking at the bond energy between two atomic molecules, C-〇 is 256.7 Kcal/mol,
Since N-0 is 149.7 Kcal/mol, oxygen becomes more stable by forming a bond with nitrogen. This makes it difficult for oxygen to diffuse into the barrier metal layer 6 due to heat treatment. Therefore, due to the diffusion of oxygen in the barrier metal layer 6, the 71 layer 5 and the barrier metal layer 6
The interface between the barrier metal layer 6 and the A1 layer 7 becomes less likely to be oxidized, and even if oxygen is contained in the barrier metal layer 6 and heat treatment is performed, increase in contact resistance and disconnection can be prevented, and the barrier effect is can be improved. Therefore, the barrier metal layer 6 can be formed so as to have a sufficient barrier effect, have a thermally stable contact resistance, and not cause a decrease in the reliability of the A1 layer 7 of the upper wiring layer.

In addition, in this embodiment, after forming the barrier metal layer 6, the A1 layer 7 is formed on the barrier metal layer 6 without breaking the vacuum, so that after forming the conventional barrier metal layer 6, it is once taken out to the atmosphere and then placed in another layer. Problems such as an increase in the number of steps, troublesome handling of the substrate, and adhesion of dust on the substrate that occur when performing heat treatment using an apparatus can be solved.

As explained above, the use of the barrier metal layer 6 made of TiN or the like according to the present invention greatly contributes to improving the performance and productivity of semiconductor devices.

In addition, in the above embodiment, when forming the barrier metal layer 6 made of TiN, a case was explained in which a certain amount of COz gas was added throughout the entire layer, but the present invention is not limited to this (see FIG. 2). As shown in Fig. 3, CO□ gas may be added to the pulse 2, or as shown in Fig. 3, Co2 gas may be added in a temporary amount.In these cases, the barrier metal Since carbon and oxygen can be localized in a part of the layer 6 and the absolute amount of oxygen in the barrier metal layer 6 can be reduced, the resistivity can be reduced, which is preferable. Both, DC power: 5KW, Ar gas flow rate 20sec,
NZ gas flow rate 80sccm, C○2 gas flow 20s
It is cca+. In addition, in the above description of one embodiment of the present invention, Ti (titanium) is selected as the high melting point metal, but
In addition, Zr (zirconium), Hf (hafnium), W (
The same effect can be obtained even if materials such as tungsten (tungsten), Mo (molybdenum), etc. are selected and used.

〔Effect of the invention〕

According to the present invention, it is possible to contain oxygen in a barrier metal layer to improve the barrier effect, thereby making it difficult to increase contact resistance and disconnection even when heat treatment is performed, and to improve the barrier effect. Furthermore, it is possible to reduce the number of steps, the troublesome handling of the substrate, and the adhesion of dust on the substrate.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining a manufacturing method of one embodiment of a semiconductor device and its manufacturing method according to the present invention, FIGS. 2 and 3 are diagrams for explaining a manufacturing method of other embodiments, and FIG. The sample shown in Figure 5 was heated at 450°C x 30 minutes + 500°C.
Figure 5 shows the frequency of junction leakage current after heat treatment for 60 minutes at ℃. Figure 5 shows a wiring contact using a barrier metal layer made of titanium nitride, which was formed by adding oxygen in a conventional SVA atmosphere. Figure 6 is a diagram showing the structure of the conventional example, and Figure 6 is a diagram showing the frequency of the junction leak current value after heat-treating the sample shown in Figure 5 of the conventional example at 450°C x 30 minutes + 500°C x 60 minutes. Figure 7 is the conventional example. FIG. 8 is a diagram showing the relationship between the MTF of the A1 layer of the upper layer interconnection and the amount of oxygen added in the conventional example. 1...-Silicon substrate, 6...-Barrier metal layer, 7...Aff layer. Diagram for explaining the manufacturing method of another embodiment Diagram for explaining the manufacturing method for another embodiment Leakage current fL(A/(J) Figure (a) 10-5 is 4 10-3 Leakage current (A/ca2) υ η-5 Figure a Elementary addition amount (sccj) Figure Added oxygen flow rate ratio 0□/A, +N, +0□× 100% The same figure showing the relationship between the MTF and the amount of oxygen added in the A2 layer of the upper layer wiring of the conventional example.

Claims (6)

[Claims] (1) Insulating film (3) formed on the silicon substrate (1) surface
) is selectively formed on the insulating film (3) and on the silicon substrate (
1) A contact window that exposes the surface; and a high melting point metal layer that extends from the surface of the silicon substrate (1) exposed at the bottom of the contact window to the surface of the insulating film (3), covering the side surface of the contact window. (5), and at least at the bottom of the contact window, the high melting point metal layer (
A high melting point metal nitride layer (6) formed on top of (6)
), a wiring layer (7) made of aluminum or aluminum alloy and having a region overlapping with the high melting point metal nitride layer (6) and extending from inside the contact window to outside the contact window; The high melting point metal layer (5) includes the silicon substrate (1).
) and the wiring layer (7) do not react with each other, a semiconductor device comprising nitrogen, carbon, and oxygen elements all mixed together. (2) The surface of the high melting point metal layer (5) in contact with the high melting point metal nitride layer (6), and the high melting point metal layer (
2. The semiconductor device according to claim 1, wherein on each of the surfaces in contact with the wiring layer (7) in 5), there is a region containing a nitrogen element and not containing a carbon element and an oxygen element. (3) By sputtering a high melting point metal in a mixed gas atmosphere of inert gas, nitrogen gas, and gas containing carbon and oxygen, a wiring layer (7) made of silicon substrate (1) and aluminum or aluminum alloy is formed. A semiconductor device and a method for manufacturing the same, characterized in that a barrier metal layer (6) made of a high melting point metal nitride is formed to prevent reactions between the two. (4) After forming the barrier metal layer (6), the wiring layer (7) made of aluminum or aluminum alloy is formed on the barrier metal layer (6) without breaking the vacuum. The described semiconductor device and its manufacturing method. (5) The semiconductor device and its manufacturing method according to claim 3, characterized in that the gas containing carbon and oxygen is added in a pulsed manner or temporarily. (6) Sputtering a high melting point metal in an atmosphere that does not contain carbon and oxygen but contains inert gas and nitrogen gas, and then sputtering a high melting point metal in an atmosphere that contains carbon and oxygen but also contains inert gas and nitrogen gas. A silicon substrate (1) and a wiring layer (7) made of aluminum or an aluminum alloy are formed by sputtering a metal and then sputtering a high melting point metal in an atmosphere that does not contain carbon or oxygen and contains inert gas and nitrogen gas. ) A semiconductor device and its manufacturing method, characterized in that a barrier metal layer (6) made of a high melting point metal nitride is formed so as to prevent a reaction between the semiconductor device and the metal nitride.