JP2555949B2 - Method for manufacturing semiconductor device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of manufacturing a semiconductor device using Al wiring.

[0002]

2. Description of the Related Art As the degree of integration of semiconductor devices increases, wirings are also miniaturized. As the wiring material of the semiconductor device, A
An Al alloy film in which a small amount of Si or Cu is added to 1 is widely used, but since the Al alloy has a high reflectance, a photoresist film is directly formed on the Al alloy film to form a desired pattern by the reduced projection exposure method. Pattern is not formed even if an attempt is made to form the pattern.

The pattern changes due to the reflected light from the Al alloy film, especially in the place where there is a step. Therefore,
Although dyeing or the like is added to the photoresist film to reduce the influence of reflected light, it is difficult to apply to fine wiring due to problems such as deterioration of fine workability.

Therefore, in order to form fine wiring, it is desirable to use an ordinary photoresist film (which does not contain dye etc.) which is excellent in fine workability, and a film having a low reflectance is formed on the Al alloy film. The method of forming is used. A film that is widely used as a film with low reflectance is a TiN film,
The application of this TiN film as an antireflection film is, for example, 19
It is proposed in Proceedings 29a-B-3 of the Japan Society of Applied Physics in the spring of 1987.

A main process flow according to the prior art when forming a TiN film as an antireflection film on an Al alloy film to form an Al wiring will be described with reference to FIG. 1 relating to the present invention. First, as shown in FIG. 1A, the silicon oxide film 2
Ti film 3, TiN on the silicon substrate 1 whose surface is covered with
After the film 4 is sequentially formed by the sputtering method, the Al alloy film 5 is formed by the sputtering method. The Ti film 3 is for improving the ohmic contact between the silicon substrate and the wiring and for reducing the connection resistance, and the film thickness is 20 to
The TiN film 4 has a thickness of about 100 nm, is a barrier metal that prevents the element from being destroyed by the mutual diffusion of the silicon substrate and Al, and has a thickness of about 50 to 200 nm.

When the Al alloy film 5 is formed, the silicon substrate 1 is heated to a temperature of 150 to 200 ° C.
The reason is as follows. That is, at a low temperature, the Al alloy film 13 covering the stepped portion of the silicon oxide film 12 of the silicon substrate 11 does not move at all, so that the coverage at the corner of the bottom of the stepped portion is poor as shown in FIG. Generally, about 1% of Si is added to the Al alloy film 13, but when the silicon substrate is heat-treated and cooled, the Si is granularly precipitated in the Al alloy film 13. This is done in order to solve problems such as large precipitation grains in the Al alloy film 13 formed at a low temperature, which easily plugs the wiring and lowers the reliability of the wiring. The Al alloy film formed at a low temperature is difficult to control in temperature, and the quality of the Al alloy film is unstable. When the Al alloy film is formed at a temperature higher than 200 ° C., large granular Si precipitates are already formed in the Al alloy film when the Al alloy film is formed.
Since the Al alloy film is patterned into a desired shape, when the dry etching method is used for etching, Si precipitation remains as an etching residue, and this is performed in order to solve the problem that a short circuit easily occurs between wirings.

After forming the Al alloy film 5, a second TiN film 6 is formed as shown in FIG. TiN film 6
Is formed by sputtering a Ti target in a mixed atmosphere of nitrogen and Ar. At that time, the Al alloy film 5 and the second
It is preferable that the TiN film 6 is continuously formed in another process chamber of the same sputtering apparatus. The reason is as follows.
That is, if the TiN film is formed after exposing the air to the atmosphere after forming the Al alloy film 5, the electromigration resistance is deteriorated, or the connection resistance between the Al wires when the second Al wire is formed thereon is increased. This is because it will increase. These problems are reported in SDM 91-136 of Technical Research Report of the Institute of Electronics, Information and Communication Engineers of 1991.

When the Al alloy film 5 and the second TiN film 6 are continuously formed by the same sputtering apparatus, since the Al alloy film 5 is in a vacuum after being formed, almost no temperature is generated before the TiN film 6 is formed. There is no decrease, and TiN at a substrate temperature of 150 ° C or higher
The film 6 will be formed.

Next, as shown in FIG. 1C, a photoresist film 7 is formed on the TiN film 6 and is patterned into a desired shape by a usual photolithography technique.

Next, as shown in FIG. 1D, a second TiN film 6, an Al alloy film 5 and a Ti film are formed by using a dry etching technique.
After the N film 4 and the Ti film 3 are sequentially etched, the photoresist film 7 is removed to complete the Al wiring.

Next, the process flow from the formation of the first Al wiring to the second Al wiring by the above method will be described with reference to the drawings. As shown in FIG. 2E, the silicon oxide film 8
To form an interlayer insulating film. The surface of the silicon oxide film 8 is flattened by combining an etch-back process with a film formed by the plasma chemical vapor deposition method, an SOG film which is spun after spin coating, and the like.

Next, as shown in FIG. 2 (F), a contact hole reaching the second TiN film 6 is formed at a desired position of the silicon oxide film by the usual lithography technique and dry etching technique.

After that, as shown in FIG. 2G, a second Al alloy film 9 and a third TiN film 10 are formed by a sputtering method and patterned into a desired shape to form a second A film.
l wiring is formed.

[0014]

In this conventional method of manufacturing a semiconductor device, since the formation temperature of the Al alloy film is 150 ° C. or higher, when the TiN film is subsequently formed, it is contained in the TiN film. With unreacted active nitrogen,
A slight amount of aluminum nitride (Al
N) is formed.

Particularly, the temperature at the time of forming the Al alloy film is 450 ° C.
In the case of performing the process of filling the connection hole provided in the interlayer insulating film by flowing the Al alloy film by heating the substrate to 450 ° C. or higher after the above or after forming the Al alloy film,
AlN is easily formed.

When AlN is formed at the interface between the Al alloy film and the TiN film in this way, the electromigration resistance of the Al wiring deteriorates. The reason is that the presence of AlN lowers the crystallinity of the Al alloy film when the substrate is heat-treated. Usually, the Al alloy film is predominantly oriented in the (100) plane, and the stronger the orientation to the (100) plane, the longer the electromigration life.
However, there is a problem that the orientation on the (100) plane is weakened and the electromigration life is shortened.

Since AlN is an insulator, TiN
Due to the presence of AlN at the interface between the film and the Al alloy film, TiN
When the connection resistance between the film and the Al alloy film becomes high and the Al2 layer wiring as shown in FIG. 2G is formed, the connection resistance between the first Al wiring and the second Al wiring increases, and in the worst case, Has the problem of being cut off.

When the TiN film is formed on the Al alloy film, the temperature is 3
At 00 ℃ or higher, the connection resistance is always high, but 150 to 20
At a temperature of about 0 ° C., the connection resistance varies.

An object of the present invention is to provide a method of manufacturing a semiconductor device in which the electric resistance is improved without nitriding the Al surface even when the wiring is formed in the laminated structure in which the TiN film is formed on the Al alloy film. To provide.

[0020]

To achieve the above object, a method of manufacturing a semiconductor device according to the present invention includes an Al forming step and a refractory metal nitride film forming step, and at least A
The l or laminate structure including an Al alloy film and a refractory metal nitride film, a manufacturing method of a semiconductor device to form an Al wiring, Al forming step, Al before Symbol laminated structure Te in a vacuum
Alternatively, it is a step of forming an Al alloy film on the substrate, and in the refractory metal nitride film forming step, Al of the substrate or Al of the substrate is formed by a reactive sputtering method while keeping the ambient atmosphere of the substrate that has undergone the Al forming step in a vacuum state. In the step of forming the refractory metal nitride film on the Al alloy film, the substrate temperature immediately before the formation of the refractory metal nitride film is 150 ° C. or lower.

Further, the formation temperature of the Al or Al alloy film is 150 ° C. or higher, and a step of cooling the substrate to 150 ° C. or lower is included before the formation of the refractory metal nitride film.

After the Al or Al alloy film is formed, the step of heating the substrate to cause the Al or Al alloy film to flow and the step of cooling the substrate to 150 ° C. or lower are included.

Further, after forming the Al wiring, a step of forming an interlayer insulating film, a step of forming a connection hole reaching the Al wiring at a desired position of the interlayer insulating film, and a second Al
And a step of forming wiring.

The refractory metal nitride film is titanium nitride (TiN).

[0025]

When the refractory metal film is formed on the Al or Al alloy film by the reactive sputtering method in the same vacuum without being exposed to the air, the temperature of the substrate immediately before the refractory metal film is formed is set to 150 ° C. or lower. To do.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.
1A to 1D are process sectional views showing an embodiment of the present invention.

As shown in FIG. 1A, a Ti film 3, T is formed on a silicon substrate 1 whose surface is covered with a silicon oxide film 2.
The iN film 4 is sequentially formed by the sputtering method, and then 1
While heating the silicon substrate 1 at a temperature of 50 to 500 ° C., for example, an Al alloy film 5 in which 1% of Si and 0.5% of copper are added to Al is formed by a sputtering method in an amount of 0.3 to 1.0 μm.
m.

Next, it is moved to another process chamber in a vacuum, and Ar gas at room temperature is flowed on the back surface of the silicon substrate 1 for 1 to 3 minutes to cool the temperature of the silicon substrate 1 to room temperature. The higher the pressure in the process chamber at this time is, the faster the cooling rate is. However, if the pressure is too high, the oxygen partial pressure becomes high, and
1Torr because the surface of the alloy film may be oxidized.
The following is better.

Then, the process chamber was moved to another process chamber, as shown in FIG.
As shown in (B), the second TiN film 6 is formed to a thickness of 50 to 100 nm at room temperature by a reactive sputtering method in which a Ti target is sputtered in a mixed atmosphere of Ar and nitrogen.

Next, as shown in FIG. 1C, a photoresist film 7 is formed on the TiN film 6 and is patterned into a desired shape by a usual photolithography technique.

Next, as shown in FIG. 1D, the second TiN film 6, the Al alloy film 5, and the like are formed by using a dry etching technique.
After the TiN film 4 and the Ti film 3 are sequentially etched, the photoresist film 7 is removed to complete the Al wiring.

In this method, the silicon substrate after the Al alloy film 5 is formed is cooled in a process chamber different from the sputtering chamber, but after the substrate is moved to the process chamber in which the TiN film 6 is formed. , At room temperature before the TiN film 6 is formed.
The TiN film 6 may be formed by flowing only r gas to the back surface of the silicon substrate 1 and cooling it to 150 ° C. or lower, then adding nitrogen gas and applying a high voltage to the target to start sputtering.

In this method, in order to improve the safety so that AlN is not formed, the substrate is moved to the process chamber where the TiN film is formed, the substrate is cooled, and then the nitrogen gas is flowed. Since it has been confirmed by experiments that the surface of the Al alloy film is not nitrided by nitrogen molecules, AlN is not formed on the surface of the Al alloy film 5 even when nitrogen gas is flowed at the same time as Ar. There is no.

According to this method, the T
Since the sputtering of the iN film can be started, the number of processed sheets per unit time can be increased. In this way TiN
If the substrate is cooled in the process chamber where the film 6 is formed, there is an advantage that the present invention can be carried out even if the number of process chambers is one, but compared with the method in which the substrate is cooled in another process chamber, the unit time is reduced. There is a problem that the number of processed sheets per hit is small.

The method described above is a method in which a low temperature inert gas is sprayed onto the substrate to actively cool it. However, in an apparatus which cannot take such a method, the temperature at the time of forming the Al alloy film is 150 ° C. When the TiN film 6 is not so high, the standing time before the formation of the TiN film 6 may be lengthened, and the TiN film 6 may be formed after waiting until the temperature becomes 150 ° C. or less by heat radiation. Alternatively, A on a plurality of substrates, for example, 25 substrates
After the l-alloy film 5 is formed, it may be returned to the substrate cassette once and the TiN film 6 may be formed in order from the first substrate. This is because the temperature of the first substrate is lowered to 150 ° C. or lower due to heat radiation while the Al alloy film 5 is formed on the 25 substrates.

In the above-described examples, the temperature at the time of forming the Al alloy film was 150 ° C. or higher, but the Al alloy film was 100 ° C.
After the substrate is formed at a low temperature of ℃ or less, the substrate is heated to 400 to 500 ° C., the Al alloy film is made to flow, and in the process of filling the opening provided in the interlayer insulating film, the various methods described above are used. The effect of the present invention can be obtained by cooling the silicon substrate to 150 ° C. or lower by any one and then forming the TiN film by the reactive sputtering method.

By the method as described above, the first Al
After forming the wiring, as shown in FIGS. 2E to 2G, by forming the silicon oxide film 7 which is the interlayer insulating film and the second Al wiring, the interface between the Al alloy film and the TiN film is completely removed. A
The Al2 layer wiring can be formed without forming 1N.

In order to clarify the difference between the present invention described above and the prior art, FIG. 3 shows a comparison of respective process flows and changes in the substrate temperature. The substrate temperature at the time of forming the Al alloy film is 450 ° C. Substrate 450
While the substrate temperature is slightly lowered while being heated to 0 ° C. and moving to the process chamber for forming the Al alloy film, the temperature rises again to 450 ° C. or higher during the formation of the Al alloy film. Up to this point, the conventional technology and the present invention are exactly the same. Thereafter, in the conventional technique, the substrate is moved to the process chamber for forming the TiN film, and at that time, the substrate temperature is slightly lowered,
The formation of the TiN film starts at 0 ° C. or higher.

On the other hand, in the present invention, the substrate is cooled to room temperature before the TiN film is formed, and then the TiN film is formed.
It is 100 ° C or lower.

In the present invention, the substrate temperature when forming the TiN film on the Al alloy film is limited to 150 ° C. or lower because the Al 2 layer wiring as shown in FIG.
When it was determined whether AlN was formed by the connection resistance, the connection resistance varied at 150 ° C. or higher, but the connection resistance was low and stable from room temperature to 150 ° C.

In the case of essentially nitriding Al with nitrogen, 500
It should not be nitrided unless the temperature is higher than ℃, but TiN film type
Nitriding at temperatures above 150 ° C during sputtering is due to sputtering
Radical nitrogen generated by plasma is directly on the Al surface
Nitrogen is activated by the active nitrogen incorporated in the TiN film.
By nitriding the Al surface, either or both
It seems that the nitriding temperature was lowered because the Al surface was nitrided.
Be seen. This can be seen from the fact that the Al surface is not nitrided even when heated to about 450 ° C. in a nitrogen atmosphere after forming the Al alloy film.

In the above description, the uppermost layer of Al wiring is T.
Although the iN film is used, the effect of the present invention can be obtained when an Al alloy film or another metal such as tungsten (W) is further formed on the TiN film.

[0043]

As described above, according to the present invention, after the Al alloy film is formed, the substrate is cooled to 150 ° C. or lower, and then the TiN film is formed thereon by the reactive sputtering method. It is possible to prevent the AlN film from being formed at the interface between the film and the TiN film. The reason for this is that active nitrogen such as radical nitrogen generated by plasma is
It is difficult to react with, and it is presumed that AlN is not formed at 150 ° C or lower.

Since AlN is not formed at the interface between the Al alloy film and the TiN film, the connection resistance between the Al alloy film and the TiN film can be kept low and stable. It is as low as 1/2 or less, and can be formed with a small variation.

Further, since AlN is not formed in the Al alloy film, the (100) plane is easily aligned in the direction perpendicular to the substrate, and therefore electromigration resistance can be improved and the life can be tripled or longer. it can.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of main steps showing an embodiment of the present invention.

FIG. 2 is a sectional view of a main step showing an embodiment of the present invention.

FIG. 3 is a diagram showing a process flow of the present invention and a conventional example, and a substrate temperature change in that case.

FIG. 4 is a cross-sectional view illustrating a problem of a conventional example.

[Explanation of symbols]

 1,11 Silicon substrate 2,8,12 Silicon oxide film 3 Ti film 4,6,10 TiN film 5,9,13 Al alloy film 7 Photoresist film

Claims (5)

(57) [Claims] 1. A method of manufacturing a semiconductor device, comprising an Al forming step and a refractory metal nitride film forming step, wherein Al wiring is formed by a laminated structure including at least Al or an Al alloy film and a refractory metal nitride film. Te, Al forming step, the Al or Al alloy film before Symbol laminated structure Te in a vacuum and a step of forming on a substrate, a refractory metal nitride film forming step, the ambient atmosphere around the substrate after the Al forming step While maintaining the vacuum state, it is a step of forming a refractory metal nitride film on the Al or Al alloy film of the substrate by a reactive sputtering method, the substrate temperature immediately before the formation of the refractory metal nitride film,
A method for manufacturing a semiconductor device, which is 150 ° C. or lower. 2. The formation temperature of the Al or Al alloy film is 150 ° C. or higher, and the method further comprises the step of cooling the substrate to 150 ° C. or lower before forming the refractory metal nitride film. 1. The method for manufacturing a semiconductor device according to 1. 3. The method according to claim 1, further comprising the steps of heating the substrate to flow the Al or Al alloy film after forming the Al or Al alloy film, and cooling the substrate to 150 ° C. or lower. The method of manufacturing a semiconductor device according to claim 1. 4. A step of forming an interlayer insulating film after forming the Al wiring, a step of forming a connection hole reaching the Al wiring at a desired position of the interlayer insulating film, and forming a second Al wiring. The method of manufacturing a semiconductor device according to claim 1, 2, or 3, further comprising: 5. The refractory metal nitride film is made of titanium nitride (TiN).
3. The method for manufacturing a semiconductor device according to 3 or 4.