JPH08186084A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE: To prevent the swell of a metal film from being locally generated by forming a barrier metal on a layer insulating film formed in the surface of a semiconductor substrate and heat-treating the barrier metal in a high vacuum and after that, depositing a metal film thereon by a chemical vapor phase epitaxy method. CONSTITUTION: After a diffused layer 2 is formed in the predetermined region of a silicon substrate 1, a layer insulating film 3 is formed. Next, a contact hole 4 is formed and a titanium metal layer 5 is formed. After that, the titanium nitride metal layer 6 of a barrier metal is formed by an ordinary sputtering method or a chemical vapor phase epitaxy method. Next, the silicon substrate 1 on which the titanium nitride is formed is heat-treated at the temperature of not less than 350 deg.C to not more than 800 deg.C in a high vacuum. Next, an aluminum metal film 8 is formed by a chemical vapor phase epitaxy method. Therefore, the aluminum metal film 8 is deposited on the titanium nitride metal layer 6 and deposited so as to fill the contact hole 4. After the aluminum metal film 8 is deposited, it is heat-treated in a high vacuum at a temperature of not less than 300 deg.C to not more than 600 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a metal film used for wiring and a method for forming wiring.

[0002]

2. Description of the Related Art Miniaturization and densification of the structure of semiconductor devices are still vigorously promoted. Regarding miniaturization, at present, a semiconductor element formed with a size of 0.25 μm is used, and a 256 megabit DRAM based on this size as a design standard has been developed and prototyped. Regarding the densification, a method of making the semiconductor element three-dimensional as well as a planar densification by miniaturization have been studied, and some of them have already been put to practical use. In fact, the three-dimensionalization of this semiconductor element has been practically applied to a passive element such as a capacitor among semiconductor elements, together with a multilayer structure of electrode wiring or a multi-layered structure of diffusion layers. Is embodied. At present, this three-dimensionalization is being studied at the development level even for active elements such as transistors.

As described above, miniaturization and three-dimensionalization are the most effective methods for achieving high performance or multi-functionalization of semiconductor devices by high integration, high speed, etc., and are essential for future manufacturing of semiconductor devices. Has become.

On the other hand, due to such miniaturization and three-dimensionalization, the flatness of the semiconductor element is deteriorated, and it is becoming more and more difficult to form the above-mentioned multilayer wiring despite the necessity. This is because the three-dimensional structure increases the vertical dimension more than the lateral dimension of the semiconductor element, and the step difference between where the semiconductor element is present and where it is not is increased. For this,
The film thickness of the interlayer insulating film between the diffusion layer on the surface of the semiconductor substrate and the wiring or between the multilayer wiring increases, and the aspect ratio of the contact hole formed in the interlayer insulating film increases. Further, it tends to be difficult to fill the contact hole with metal.
And this tendency is more remarkable in a finer semiconductor device.

Regarding the method of connecting the diffusion layer and the wiring or between the multilayer wirings and the method of filling the contact hole with the conductive material, a CVD (chemical vapor deposition) method of an aluminum metal film or the like (hereinafter referred to as aluminum CVD The method of forming a metal film by the method (referred to as “method”) has been most promising for simultaneously embedding a conductor material in a contact hole and wiring a metal.

A conventional wiring forming method using the aluminum CVD method will be described below. 5A to 5C are sectional views showing the conventional technique in the order of steps. As shown in FIG. 5A, the diffusion layer 22 is formed in a predetermined region of the silicon substrate 21. After this, an interlayer insulating film 23 covering the entire surface of the silicon substrate is deposited. Next, contact hole 2
4 is formed on the diffusion layer 22 by a known photolithography technique and dry etching technique. Then, the titanium metal layer 2 is formed on the surfaces of the contact hole 24 and the interlayer insulating film 23.
5 and the titanium nitride metal layer 26 are laminated. Here, the titanium metal layer 25 or the titanium nitride metal layer 26 that is a barrier metal is formed by the sputtering method.

Next, as shown in FIG. 5B, aluminum CV
The aluminum metal film 27 is formed by the D method. Here, a source gas of an alkyl metal such as dimethyl aluminum hydride (DMAH) is used as a reaction gas of this aluminum CVD, and Ar or H ₂ gas is used as an atmosphere gas. The temperature of this film formation is set to 100 to 200 ° C.

In the above description of the conventional technique, the formation of the wiring electrically connected to the diffusion layer has been described. Here, when the lower layer wiring and the upper layer wiring which replace the diffusion layer are electrically connected, they are similarly formed.

[0009]

In the above-described conventional wiring forming method, the adhesion between the barrier metal and the metal film formed by the CVD method is poor, and the aluminum metal film is formed by the aluminum CVD method as shown in FIG. The metal film bulge 28 as shown in b) locally occurs. This occurs because hydrogen contained in the titanium metal layer 25 and the titanium nitride metal layer 26 described above is released from the titanium metal layer and pushes up a part of the aluminum metal film. Such swelling of the metal film significantly impairs fine workability for forming fine wiring, and also causes peeling or unevenness of the wiring.

Further, since the aluminum metal film formed by the conventional CVD method contains a large amount of hydrogen, the reliability of the wiring formed by this aluminum metal film is remarkably lowered. In particular, the electromigration (EM) resistance of the wiring deteriorates.

An object of the present invention is to solve the above problems and facilitate the formation of highly reliable fine multi-layer wiring.

[0012]

To this end, a method of manufacturing a semiconductor device according to the present invention comprises a step of forming a barrier metal on an interlayer insulating film formed on the surface of a semiconductor substrate, and the barrier metal in a high vacuum. And a step of depositing a metal film on the barrier metal subjected to the heat treatment by chemical vapor deposition after the heat treatment.

Here, the barrier metal is a titanium nitride thin film formed by laminating on a titanium metal thin film, and the temperature of the heat treatment is set to 350 ° C. or higher and 800 ° C. or lower.

Alternatively, after the metal film is deposited by the chemical vapor deposition method, the metal film is subjected to heat treatment in a high vacuum.

Here, the metal film deposited by the chemical vapor deposition method is an aluminum metal film, and after the deposition of the aluminum metal film, a heat treatment of 300 ° C. or more and 600 ° C. or less in a high vacuum is continuously performed. Is given.

Further, as the metal film, an alloy of aluminum and copper or a thin film of copper is used.

[0017]

Next, the present invention will be described with reference to the drawings. 1A to 1D are cross-sectional views in the order of steps for explaining a method for manufacturing a semiconductor device according to an embodiment of the present invention. As shown in FIG. 1A, the diffusion layer 2 is formed in a predetermined region on the surface of the silicon substrate 1. After doing so, the interlayer insulating film 3 is formed. Here, the interlayer insulating film 3 is a silicon oxide film or a BPSG film (silicon oxide film containing boron glass and phosphorus glass) deposited by the CVD method. Next, the contact hole 4 is formed by a known photolithography technique and dry etching technique. For example, the diameter of this contact hole is set to 0.3 μm.

Next, the titanium metal layer 5 is formed by the collimated sputtering method. Here, the film thickness of the titanium metal layer 5 is set to 20 to 40 nm. After this, the titanium nitride metal layer 6 is formed by the usual sputtering method or CVD method. The film thickness of the titanium nitride metal layer 6 is 50 to 100 nm. Here, when the titanium nitride metal layer 6 is formed by the CVD method, T 2 is used as a reaction gas.
A mixed gas of iCl ₄ and NH ₃ is used, and N ₂ or H ₂ gas is used as an atmosphere gas. The temperature and gas pressure for this film formation are 500 to 600 ° C.,
It is set at 1 to 10 Torr.

Next, the silicon substrate in the state shown in FIG. 1A is vacuum annealed. This vacuum annealing is performed by a vacuum annealing apparatus having a lamp heating unit and having a vacuum system capable of adjusting the degree of vacuum to 10 ⁻⁵ to 10 ⁻⁸ Torr. Here, the vacuum annealing conditions are as follows: heating temperature is 350 ° C. and vacuum degree is 1
It is set to be 0 ^-7 Torr. Then, vacuum annealing is performed for 30 seconds. By this vacuum annealing,
As shown in (b), degassing 7 is generated. This degassing 7
Is H ² gas as described later.

Next, as shown in FIG. 1C, the aluminum metal film 8 is formed by the CVD method. Here, a source gas of an alkyl metal such as DMAH is used as a reaction gas for this CVD, and H ₂ gas is used as an atmosphere gas.
Then, the total pressure of these gases is set to 1 Torr. The temperature of this film formation is 100 to 150.
Set to ° C. In this way, the aluminum metal film 8 having a film thickness of 500 nm is deposited on the titanium nitride metal layer 6 and deposited so as to fill the contact hole 4.

As described above, the aluminum metal film to be the conductor and the wiring buried in the contact hole 4 is formed.

Next, the analysis of the outgas 7 shown in FIG. 1B will be described. This degassing analysis is performed by the temperature rising gas desorption analysis method. That is, in this analysis method,
The temperature of the sample to be measured is raised at a constant heating rate, and the degassing of atoms or molecules released from the sample is analyzed by a quadrupole mass spectrometer, and the amount of degassing is determined for each mass of degassing. Quantified. Here, the conditions for the temperature rising gas desorption are
Temperature range 100-700 ° C., heating rate 100 ° C./min, background pressure in analyzer 1 × 10 ⁻⁹ Torr
Is. The mass range of the analysis gas is 2 to 100 in terms of mass / charge.

FIG. 2 shows the results of the temperature rising gas desorption analysis of the silicon substrate in the state of FIG. 1 (a). Degassing 7 mentioned above
Shows a sharp increase in temperature from around 300 ° C and reaches a peak at 350 ° C. This degassing was H _{2 according to} the mass spectrometry described above. This H ₂ gas is released from the titanium nitride metal layer 6 or the titanium metal layer 5 shown in FIG.

Next, the effect of this vacuum annealing will be described. Table 1 summarizes the deposition state of the aluminum metal film 8 after the step of FIG. 1C after changing the temperature condition of the vacuum annealing in the step of FIG. 1B and performing vacuum annealing.

[0025]

[Table 1]

Here, the vacuum degree of the vacuum annealing is 10 ⁻⁷ T.
orr and the annealing time is 30 seconds.

As can be seen from the levels 4 and 5 shown in this table, when the vacuum annealing temperature is 350 ° C. or higher, the aluminum metal film does not swell at all, and the adhesiveness with the lower titanium nitride metal layer does not occur. Greatly improved.

The deposition state of the aluminum metal film becomes worse as the vacuum annealing temperature decreases. In Levels 1 and 2, the aluminum metal film swells and its adhesiveness is poor. In level 3, the aluminum metal film does not swell and its adhesion is not so bad, but it is in an insufficient state. The level 1 corresponds to the case of the above-mentioned conventional technique.

Here, the effect of degassing increases as the temperature of this vacuum annealing increases. However, if the temperature becomes too high, the junction depth of the diffusion layer 2 increases and it becomes difficult to form a shallow junction. In particular, it becomes difficult to form a shallow junction in a diffusion layer having a p-type conductivity. Therefore, the temperature of this vacuum annealing is preferably set to 800 ° C. or lower. Here, if the degree of vacuum during this annealing is 10 ⁻⁵ Torr or more, the time required for vacuum annealing is 1 minute or less, the junction depth of the p-type diffusion layer does not change at all, and the depth of 0. Bonding of 1 μm or less is secured.

If the vacuum annealing of the present embodiment is performed subsequent to the above-mentioned film formation of the barrier metal in one processing apparatus equipped with a multi-chamber, the wiring process will be further simplified. Here, if the vacuum degree of this vacuum annealing is 10 ⁻⁵ Torr or more, the above-described annealing effect will be produced in an annealing time of about 1 minute.

Such barrier metal annealing can also be performed in a heat treatment furnace in an atmosphere of N ₂ or Ar gas at normal pressure. However, in this normal pressure annealing, it is necessary to raise the purity of the heat treatment furnace or the gas system so that the partial pressure of H ₂ O or H ₂ becomes 10 ⁻⁶ Torr or less.

Next, a second embodiment of the present invention will be described with reference to FIG. 3A to 3D are sectional views showing a method of manufacturing a semiconductor device according to the present invention in the order of steps. As shown in FIG. 3A, the diffusion layer, the interlayer insulating film, the barrier metal and the like are formed on the silicon substrate in the same manner as described with reference to FIG. That is, first, the diffusion layer 2 is formed in a predetermined region on the surface of the silicon substrate 1. Then, the interlayer insulating film 3 is formed.
Here, the interlayer insulating film 3 is a silicon oxide film deposited by the CVD method. Next, the contact hole 4 is formed by a known photolithography technique and dry etching technique. For example, the diameter of this contact hole is 0.2
It is set to μm.

Next, the titanium metal layer 5 is formed by the collimated sputtering method. Here, the film thickness of the titanium metal film 5 is set to about 20 nm. After doing this,
The titanium nitride metal layer 6 is formed by the CVD method. The film thickness of this titanium nitride metal is about 50 nm. Where CVD
In forming titanium nitride metal by the method, T
A mixed gas of iCl ₄ or alkyl Ti and N ₂ H ₂ is used, and N ₂ or H ₂ gas is used as an atmosphere gas. Here, the total gas pressure is set to about 1 Torr, and the film formation temperature is set to about 400 ° C.

Next, as shown in FIG. 3B, vacuum annealing is performed in the same manner as in the above-described first embodiment. Here, the vacuum annealing conditions are set so that the heating temperature is 350 ° C. and the degree of vacuum is 10 ⁻⁶ Torr. Then, vacuum annealing is performed for 30 seconds. By this vacuum annealing, outgas 7 is generated as shown in FIG.

Next, an aluminum metal film 8 is deposited as shown in FIG. Here, the film formation of the aluminum metal film 8 is performed by the same method as described in the first embodiment. That is, the aluminum metal film 8 is formed by the CVD method. A source gas of an alkyl metal such as DMAH is used as a reaction gas for this CVD, and H ₂ gas is used as an atmosphere gas. Then, the total pressure of these gases is set to 1 Torr. The temperature of this film formation is 100
Set to ~ 150 ° C. In this way, the film thickness is 50
A 0 nm aluminum metal film 8 is deposited on the titanium nitride metal layer 6 and deposited so as to fill the contact hole 4.

After the aluminum metal film 8 is formed, high vacuum annealing is performed again. This high-vacuum annealing causes re-outgassing 9. Here, the vacuum annealing conditions are set so that the heating temperature is 300 to 350 ° C. and the degree of vacuum is 10 ⁻⁶ Torr. Then, vacuum annealing is performed for 30 seconds to 1 minute.

In this way, as shown in FIG. 3D, a highly reliable wiring electrically connected to the diffusion layer 2 formed on the silicon substrate 1 is formed.

Next, the analysis result of the above-mentioned re-degassing 9 will be described. FIG. 4 shows the result of the temperature rising gas desorption analysis of the silicon substrate in the state of FIG. 3 (d). The amount of the re-degas 9 described above has one peak due to CH ₄ at a temperature of around 270 ° C. and a peak due to H _{2 at} around 340 ° C.
Here, these gases are released from the aluminum metal film 8.

The results of the temperature rising gas desorption analysis show that the effect of re-degassing is fully exhibited when the temperature of the vacuum annealing of the aluminum metal film 8 is set to 300 ° C. or higher. When vacuum annealing is performed after forming the aluminum metal film, the reliability of the wiring is further improved. That is, the EM resistance is improved about three times as compared with the case without vacuum annealing.
Also, the resistance to stress migration (SM) is improved to more than twice. Further, as shown in FIG. 3C, the smoothness of the surface of the aluminum metal film formed by the CVD method is improved as compared with the case shown in FIG. 1C.

In the case of this embodiment, the heating temperature in vacuum annealing of the aluminum metal film may be set to 660 ° C. or lower of the melting point of the aluminum metal film. However, in the case of multi-layer wiring, if the wiring made of aluminum metal is formed in the lower layer, this heating temperature needs to be set to 600 ° C. or lower. This is because if the temperature of the vacuum annealing exceeds 600 ° C., the shape of the underlying wiring changes.

In the series of wiring formation in this embodiment, the vacuum annealing is performed following the above-described barrier metal film formation in one processing apparatus having a multi-chamber, and the aluminum metal film formation is further repeated. When the vacuum annealing is performed, the wiring forming process is further simplified.
Then, the reliability of the formed wiring is further improved.

In the above first and second embodiments, the same effect is obtained even if a refractory metal such as tungsten or its nitride is used as the barrier metal. Also, the case where DMAH is used as a source gas in aluminum CVD has been described, but triisobutylaluminum (TI
It should be noted that the same effect can be obtained by using (BA) as a source gas. Further, similar effects can be obtained when an aluminum-copper alloy is formed by the CVD method instead of aluminum metal or when copper is formed by the CVD method.

If the vacuum degree of the vacuum annealing described in the first or second embodiment is 10 ^-5 or more, the annealing time can be 1 minute or less, which is a problem in the production of semiconductor devices. Does not occur.

Further, in these embodiments, the formation of the wiring electrically connected to the diffusion layer was mainly described, but the same effect can be obtained even when the wiring of the lower layer and the wiring of the upper layer in the multilayer wiring are connected. Also mention.

[0045]

As described above, according to the method of manufacturing a semiconductor device of the present invention, a barrier metal film is formed or a CV film is formed.
After forming the metal film by the D method, vacuum annealing is performed.
As a result, local swelling of the metal film from the barrier metal, which occurs in the metal film formed by the CVD method, is suppressed, and the degree of adhesion between the metal film and the barrier metal is significantly improved. In addition, the reliability including the EM or SM resistance of the metal film wiring formed by the CVD method is also improved.

Furthermore, the prevention of the swelling of the metal film or the improvement of the smoothness of the surface of the metal film facilitates the formation of a fine wiring pattern.

As described above, the present invention facilitates the formation of highly reliable fine multi-layered wiring and promotes high integration or high density of semiconductor devices.

[Brief description of drawings]

1A to 1D are schematic cross-sectional views in order of a process, illustrating a first embodiment of the present invention.

FIG. 2 is a temperature rising gas desorption analysis diagram for explaining the effect of the first embodiment of the present invention.

3A to 3D are schematic cross-sectional views in order of the steps, for explaining the second embodiment of the present invention.

FIG. 4 is a temperature rising gas desorption analysis diagram for explaining the effect of the second embodiment of the present invention.

5A to 5D are schematic cross-sectional views in order of processes, illustrating a conventional technique.

[Explanation of symbols]

 1,21 Silicon substrate 2,22 Diffusion layer 3,23 Interlayer insulating film 4,24 Contact hole 5,25 Titanium metal layer 6,26 Titanium nitride metal layer 7 Degassing 8,27 Aluminum metal film 9 Regassing 28 Metal film Blisters

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 21/768

Claims (5)

[Claims] 1. A step of forming a barrier metal on an interlayer insulating film formed on a surface of a semiconductor substrate, a step of heat-treating the barrier metal in a high vacuum, and a step of performing the heat treatment after the step of the heat treatment. And a step of depositing a metal film on the barrier metal by a chemical vapor deposition method. 2. The barrier metal is a titanium nitride thin film formed by laminating on a titanium metal thin film, and the temperature of the heat treatment is 350 ° C. or higher and 800 ° C. or lower. Of manufacturing a semiconductor device of. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the metal film is heat-treated in a high vacuum after the metal film is formed by the chemical vapor deposition method. 4. The metal film deposited by the chemical vapor deposition method is an aluminum thin film, and the temperature of heat treatment of the metal film in a high vacuum is 300 ° C. or higher and 600 ° C. or lower. 4. The method for manufacturing a semiconductor device according to claim 3. 5. The method of manufacturing a semiconductor device according to claim 1, wherein the metal film is an alloy of aluminum and copper or a thin film of copper.