JPH11204456A - Method for manufacturing semiconductor device - Google Patents

Abstract

[PROBLEMS] To increase the resistance value of a refractory metal film despite forming a silicon nitride film on the refractory metal film to be a gate electrode or a metal wiring by a chemical vapor deposition method. In addition, the shape of the pattern made of the high melting point metal film is not made non-uniform. SOLUTION: A silicon oxide film 2, a polycrystalline silicon film 3, a barrier metal layer 4, and a high melting point metal film 5 are sequentially deposited over a whole surface of a silicon substrate 1. Next, the silicon substrate 1 is loaded into the load lock chamber with the oxygen concentration in the load lock chamber provided adjacent to the reaction furnace reduced to 1 ppm or less. Next, the silicon substrate 1
Is transferred from the load lock chamber to a reaction furnace maintained at a temperature of about 600 ° C. and depressurized, and then ammonia gas is flowed into the reaction furnace for about 5 minutes while the temperature in the reaction furnace is maintained at 600 ° C. . Thereafter, the temperature in the reactor was increased to 760 ° C., and NH ₃ gas and SiH ₂ were introduced into the reactor.
By introducing a source gas composed of Cl ₂ gas,
The first silicon nitride film 6 is formed on the refractory metal film 5 by LP-
The film is formed by a CVD method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device in which a silicon oxide film is formed on a high melting point metal film formed on a semiconductor substrate. .

[0002]

2. Description of the Related Art Semiconductor integrated circuit devices such as MOSFETs
In order to achieve high speed, it is necessary to reduce the resistance of the gate electrode and the metal wiring. In order to reduce the resistance of the gate electrode and the metal wiring, the gate electrode and the metal wiring must be made of a low-resistance material. Processes composed of melting point metals have been developed.

As an example of a method of manufacturing a semiconductor device having a gate electrode made of a high-melting-point metal film and a metal wiring, an n-type semiconductor device having a gate electrode having a laminated structure of a high-melting-point metal film / barrier metal layer / polycrystalline silicon film will be described. Type MOSFE
3A to 3C and FIG.
This will be described with reference to FIGS. 5 (a) and 5 (b) and FIGS. 5 (a) and 5 (b).

First, as shown in FIG. 3A, after a device isolation region 11 is formed in a predetermined region on a silicon substrate 10, a silicon oxide film serving as a gate insulating film is formed over the entire surface of the silicon substrate 10. 12 is formed. Next, after depositing a polycrystalline silicon film 13 on the silicon oxide film 12,
An n-type conductive impurity such as As is introduced into the polycrystalline silicon film 13. Next, after depositing a barrier metal layer 14 made of a compound of a high melting point metal such as titanium nitride (TiN) on the polycrystalline silicon film 13, for example, tungsten (W) or the like is deposited on the barrier metal layer 14. A refractory metal film 15 made of a refractory metal is deposited. The barrier metal layer 14 plays a role in preventing a reaction between the high melting point metal forming the high melting point metal film 15 and the polycrystalline silicon forming the polycrystalline silicon film 13. Next, a protective film 16 made of a silicon nitride film is deposited on the high melting point metal film 15 to protect the high melting point metal film 15.

Next, as shown in FIG. 3B, a silicon oxide film 12, a polycrystalline silicon film 13, and a barrier metal layer 1 are formed.
4. A multilayer film composed of the refractory metal film 15 and the protective film 16 is patterned to form a polycrystalline silicon film 13, a barrier metal layer 14, and a gate electrode 17 composed of the refractory metal film 15.
To form By doing so, the low-resistance gate electrode 1
7 can be formed. Next, using the gate electrode 17 as a mask, an impurity such as As is ion-implanted into the silicon substrate 10 at an energy of about 20 keV to form a low-concentration impurity diffusion region 19a. Next, after depositing a silicon nitride film over the entire surface of the silicon substrate 10,
By performing anisotropic etching on the silicon nitride film, sidewalls 18 made of the silicon nitride film are formed on the side surfaces of the gate electrode 17. Next, using the gate electrode 17 and the side wall 18 as a mask, the silicon substrate 1
The low-concentration impurity diffusion region 1 is formed by self-aligning the high-concentration impurity diffusion region 19b by ion-implanting an impurity such as As with an energy of about 30 keV.
An impurity diffusion layer 19, which is composed of 9a and a high-concentration impurity diffusion region 19b, is formed as a source / drain region.

Next, after depositing, for example, a titanium (Ti) film over the entire surface of the silicon substrate 10, 650 to 70
By performing a heat treatment at a temperature of 0 ° C. for about 30 seconds, a silicide film 20 is formed in a self-aligned manner on the impurity diffusion layer 19 from which silicon is exposed, as shown in FIG. In this case, the titanium film deposited on the protective film 16 and the sidewall 18 made of the silicon nitride film does not react with the silicon nitride film, and thus remains unreacted. Next, after removing the unreacted titanium film by wet etching, a heat treatment is performed at a temperature of 850 to 900 ° C. for about 5 seconds to transform the silicide layer 20 into a low-resistance phase, thereby forming a source / drain region. The resistance of the impurity diffusion layer 19 is reduced.

Next, as shown in FIG. 4A, after an interlayer insulating film 21 made of a silicon oxide film is deposited over the entire surface of the silicon substrate 10, the interlayer insulating film 21 is selectively formed. Then, a contact hole 22 is formed by performing dry etching.

Next, as shown in FIG. 4B, a metal film is deposited inside the contact hole 22 and on the contact hole 22 to form a metal wiring 23 and the metal wiring 23 and the impurity diffusion layer 19. Is formed.

Since the gate electrode 17 is covered with the side wall 18 made of a high melting point metal, when forming the contact hole 22 in the interlayer insulating film 21,
As shown in FIG. 5A, even if the contact hole 22 crosses over the gate electrode 17 side due to misalignment of lithography, the silicon oxide film forming the interlayer insulating film 21 and the high melting point forming the sidewall 18 According to the dry etching selectivity with the metal film, the gate electrode 1
The contact hole 22 can be formed without short-circuiting the impurity diffusion layer 19 with the impurity diffusion layer 19. Further, since the gate electrode 17 is covered with the side wall 18 made of a high melting point metal, even if the gate electrodes 17 are provided at a small interval as shown in FIG. The contact hole 22 can be formed in the self-alignment 21.

[0010]

By the way, the structure of the MOSFET has been miniaturized in order to cope with high integration and high speed in recent semiconductor integrated circuit devices, and accordingly, the resistance of the gate electrode 17 has been reduced. Although required, when the gate electrode 17 is formed of the high melting point metal film 15 such as tungsten in order to reduce the resistance of the gate electrode 17, the situation where the high melting point metal film 15 is etched in the cleaning step and the heat treatment step It is necessary to avoid a situation where the high melting point metal film 15 causes an abnormal reaction with the atmospheric gas. Therefore, it is necessary to cover the refractory metal film 15 made of tungsten or the like with a stable protective film 16 made of a silicon nitride film.

As shown in FIG. 5A or FIG. 5B, in order to achieve high integration of a semiconductor integrated circuit device,
Even when a method of forming a contact hole exposing the sidewall 18 to the contact hole 22 (hereinafter referred to as a self-aligned contact hole forming method) is performed, it is necessary to cover the gate electrode 17 with the sidewall 18 made of a silicon nitride film. is there.

When forming the silicon nitride film forming the protective film 16 and the side wall 18, the silicon nitride film is decompressed in order to satisfy the etching resistance in the cleaning step or the etching resistance in the self-align contact hole forming step. Chemical vapor deposition (Low Pressure CV)
D method: LP-CVD method).

However, in the step of forming a silicon nitride film on the high melting point metal film 15 made of, for example, tungsten by the LP-CVD method, a wafer having the high melting point metal film 15 exposed is removed. After charging the reactor through a load lock chamber having substantially the same atmosphere as the atmosphere into a reactor having substantially the same atmosphere as the atmosphere, NH ₃ and SiH ₂ Cl ₂ gas are introduced into the reactor at a flow rate of 600 sccm and 60 sccm, respectively. Is formed at a temperature of about 760 ° C., and when a silicon nitride film is formed in this manner,
The first problem is that the surface of the refractory metal film is non-uniformly nitrided, and the silicon nitride film grows non-uniformly and granularly, thereby impairing the performance of the protective film 16. And the third problem that the pattern shape of the patterned high-melting metal film becomes non-uniform when a multilayer film is patterned to form a gate electrode or a metal wiring.

Japanese Patent Application Laid-Open No. 7-94731 discloses a semiconductor device in which a refractory metal nitride film is formed on a refractory metal film and a silicon nitride film is formed on the refractory metal nitride film. Manufacturing methods have been proposed.

According to this method of manufacturing a semiconductor device, the first problem that the performance of the protective film made of a silicon nitride film is impaired is solved, but the second problem that the resistance value of the high melting point metal film is increased. Problem is not solved. Further, the third problem that the pattern shape of the refractory metal film becomes uneven is solved by a complicated process.

By the way, in order to solve the above-mentioned first to third problems, the silicon nitride film is subjected to plasma C at about 450 ° C.
VD method (Plasma Enhanced CVD method: PE-CVD method)
It is also considered that a film is formed by the method described above. That is, PE-C
When the silicon nitride film is formed on the high melting point metal film by the VD method, the first problem is that the performance of the protective film made of the silicon nitride film is impaired, and that the resistance value of the high melting point metal film increases. The second problem and the third problem of non-uniformity in the pattern shape of the refractory metal film do not occur.

However, the silicon nitride film formed by the PE-CVD method has a new problem that the etching resistance in the cleaning step or the etching resistance in the self-aligned contact hole forming step is not sufficient. Therefore, it is not preferable to form a silicon nitride film to be a protective film of a refractory metal film or a sidewall of a gate electrode by the PE-CVD method.

In view of the above, the present invention provides a method of forming a gate electrode or a metal wiring, on which a silicon nitride film is formed by a chemical vapor deposition method. It is an object of the present invention to prevent the rise of the temperature and increase the non-uniformity of the shape of the pattern made of the high melting point metal film.

[0019]

Means for Solving the Problems To achieve the above object, the present inventors have made LP-CVD on a refractory metal film.
Auger Electron Spectroscopy (Auger Electron Spectroscopy) shows the composition of a multilayer film when a silicon nitride film is formed by a method and the composition of a multilayer film when a silicon nitride film is formed on a refractory metal film by a PE-CVD method. (Spectroscopy: AES method)
Was analyzed by

FIG. 6 shows a cross-sectional structure of a multilayer film when a silicon nitride film is formed by the LP-CVD method, and FIG.
2 shows a cross-sectional structure of a multilayer film when a silicon nitride film is formed by an E-CVD method. FIG. 8 shows the LP-CV
A of multi-layer film when silicon nitride film is formed by D method
FIG. 9 shows an ES analysis result, and FIG. 9 shows an AES analysis result of the multilayer film when the silicon nitride film is formed by the PE-CVD method.

When the silicon nitride film is formed by the LP-CVD method, as shown in FIGS. 6 and 8, an abnormal reaction occurs at the interface between the refractory metal film 15 and the protective film 16 made of the silicon nitride film. While the layer 25 is formed, P
When the silicon nitride film is formed by the E-CVD method, the reaction layer 25 is not formed at the interface between the refractory metal film 15 and the protective film 16 as shown in FIGS. As can be seen from FIG. 8, the reaction layer 25 is an amorphous film in which tungsten, silicon, nitrogen, and oxygen are mixed.

Therefore, LP-CVD is performed on the refractory metal film.
When the silicon nitride film is formed by the method, the cause of the increase in the resistance value of the refractory metal film or the non-uniformity of the pattern of the refractory metal film is caused by the presence of the reaction layer 25. Conceivable.

Further, the inventors of the present invention changed the composition of a multilayer film when a silicon nitride film was formed by the LP-CVD method and the composition of a multilayer film when a silicon nitride film was formed by the PE-CVD method. It was analyzed by X-ray diffraction.

FIG. 10 shows an X-ray diffraction pattern when a silicon nitride film is formed by the LP-CVD method.
Shows an X-ray diffraction pattern when a silicon nitride film is formed by the PE-CVD method. The peak of tungsten nitride (W ₂ N), which does not appear in FIG.
At 0, it appears near W (110).

From the above analysis results, the abnormal reaction layer is a film in which a crystal of tungsten nitride and an amorphous phase of silicon, nitrogen, and oxygen are mixed. Oxygen enters the film to form an oxide film on the surface of the refractory metal film. In the process of forming the silicon nitride film, the refractory metal oxide film changes to a phase containing silicon and nitrogen. It is considered to be formed by this.

The present invention has been made on the basis of the above findings, and is intended to reduce the semiconductor substrate on which a high melting point metal film is formed to an oxygen concentration such that an oxide film is not formed on the surface of the high melting point metal film. It is charged into a reaction furnace maintained at an oxygen concentration such that an oxide film is not formed on the surface of the refractory metal film through the held load lock chamber, and the LP-CVD method is performed in the reaction furnace. To form a silicon nitride film on the high melting point metal film.

More specifically, the method for manufacturing a semiconductor device according to the present invention comprises the steps of: forming a semiconductor substrate on which a refractory metal film serving as a gate electrode or a metal wiring is formed; Through a load lock chamber that is maintained in an atmosphere with an oxygen concentration that does not form, it is charged into a reaction furnace that is maintained in an atmosphere with an oxygen concentration that does not form an oxide film on the surface of the high-melting metal film. Substrate loading process
A step of introducing a source gas containing nitrogen and silicon into a reactor in which a semiconductor substrate has been introduced, and forming a silicon nitride film on the refractory metal film by a chemical vapor deposition method. I have.

According to the method of manufacturing a semiconductor device of the present invention,
The semiconductor substrate is passed through a load lock chamber which is maintained in an atmosphere having an oxygen concentration such that an oxide film is not formed on the surface of the refractory metal film, so that no oxide film is formed on the surface of the refractory metal film. And a silicon nitride film is formed by a LP-CVD method in the reaction furnace maintained in such an atmosphere. No abnormal reaction layer is formed at the interface with the silicon nitride film.

In the method of manufacturing a semiconductor device according to the present invention,
In the film forming step, NH ₃ gas is introduced into the reaction furnace to make the inside of the reaction furnace an atmosphere of NH ₃ gas, and then NH ₃ gas is introduced into the reaction furnace.
It is preferable to include a step of introducing a source gas composed of a mixed gas of _three gases and a SiH ₂ Cl ₂ gas.

In the method of manufacturing a semiconductor device according to the present invention, in the film forming step, the oxide film formed on the surface of the refractory metal film is removed by holding the semiconductor substrate in an atmosphere of a reducing gas. It is preferable to include a step of introducing a source gas into the reactor later.

In the method of manufacturing a semiconductor device according to the present invention, in the film forming step, the oxide film formed on the surface of the refractory metal film is removed while the semiconductor substrate is held in a reducing gas atmosphere. Later, an NH ₃ gas is introduced into the reaction furnace to change the inside of the reaction furnace to an atmosphere of NH ₃ gas, and then a source gas composed of a mixed gas of NH ₃ gas and SiH ₂ Cl ₂ gas is introduced into the reaction furnace. It is more preferable to include a step of introducing.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing a semiconductor device according to each embodiment of the present invention will be described with reference to the drawings.

(First Embodiment) A method of manufacturing a semiconductor device according to a first embodiment of the present invention will be described below with reference to FIG.

First, as in the prior art, after forming an element isolation region (omitted in FIG. 1) in the silicon substrate 1, a silicon oxide film serving as a gate insulating film is formed over the entire surface of the silicon substrate 1. A film 2, a polycrystalline silicon film 3, a barrier metal layer 4 made of a compound of a high melting point metal such as titanium nitride, and a high melting point metal film 5 made of a high melting point metal such as tungsten are sequentially deposited. The barrier metal layer 4 plays a role in preventing a reaction between the high melting point metal forming the high melting point metal film 5 and the polycrystalline silicon forming the polycrystalline silicon film 3.

Next, the interior of the load lock chamber provided adjacent to the reaction furnace is replaced with nitrogen gas to reduce the oxygen concentration in the load lock chamber to 1 ppm or less. Then, the silicon substrate 1 on which the high melting point metal film 5 is formed is loaded.

Thus, no oxide film is formed on the surface of the refractory metal film 5 inside the load lock chamber. In the first embodiment, the oxygen concentration in the load lock chamber is set to 1 ppm or less, but if the oxygen concentration in the load lock chamber is about 40 ppm or less, the surface portion of the refractory metal film 5 No oxide film is formed on the substrate.

Next, the silicon substrate 1 is transferred from the load lock chamber to a reaction furnace maintained at a temperature of about 600 ° C. and depressurized, and then the reaction furnace is maintained at a temperature of 600 ° C. Ammonia (N
H ₃ ) Flow gas for about 5 minutes. Thereafter, the temperature in the reaction furnace was increased to 760 ° C., and a flow rate of 600
sccm NH ₃ gas and flow rate 60 sccm SiH ₂
By introducing Cl ₂ gas, the first silicon nitride film 6 is deposited on the refractory metal film 5 under a total pressure of 40 Pa.
The film is formed by a P-CVD method. In this case, N
Of H ₃ reactor by flowing gas after the atmosphere of the NH ₃ gas, the reason for introducing the source gas of NH ₃ gas and SiH ₂ Cl ₂ gas, SiH ₂ Cl ₂ constitutes a refractory metal film This is for avoiding formation of silicide of tungsten by reacting with tungsten.

Next, a multilayer film composed of the silicon oxide film 2, the polycrystalline silicon film 3, the barrier metal layer 4, the refractory metal film 5, and the first silicon nitride film 6 is patterned by a method similar to the conventional method. After forming a gate electrode composed of the polycrystalline silicon film 3, the barrier metal layer 4, and the refractory metal film 5, the silicon substrate 1 is formed using the gate electrode as a mask.
Then, an impurity such as As is ion-implanted at an energy of about 20 keV, and thereafter, LP-CVD is performed over the entire surface.
After depositing a second silicon nitride film having a thickness of about 100 nm by the method, the second silicon nitride film is anisotropically etched to form a second silicon nitride film on the side surface of the gate electrode. A sidewall is formed (see FIG. 3B).

In the step of forming the second silicon nitride film by the LP-CVD method, the silicon substrate 1 is kept at about 600 ° C. from the load lock chamber similarly to the step of forming the first silicon nitride film 6. After being transferred into the reactor which is maintained at a temperature of and reduced in pressure, the temperature in the reactor is raised to 600 ° C.
NH flow 600sccm into the reactor while maintaining the ₃
Let the gas flow for about 5 minutes. Thereafter, the temperature in the reactor was reduced to 76
Raise the temperature to 0 ° C and set the flow rate in the reactor at 600 scc.
m 2 NH ₃ gas and a flow rate of 60 sccm SiH ₂ Cl ₂ gas are introduced to form a second silicon nitride film on the refractory metal film 5 at a total pressure of 40 Pa by LP-CVD.
The film is formed by a method. In this case, the reason for introducing the source gas composed of the NH ₃ gas and the SiH ₂ Cl ₂ gas after setting the atmosphere in the reaction furnace to the NH ₃ gas atmosphere is that SiH ₂ Cl ₂ reacts with tungsten constituting the high melting point metal film. This is to avoid the formation of silicide of tungsten.

Next, as in the conventional method, after forming an impurity diffusion layer serving as a source / drain, a contact and a metal wiring are formed (FIGS. 3B and 3C and FIG. 4).
(See (a) and (b)).

By the way, when forming the first and second silicon nitride film, by introducing the source gas of NH ₃ gas and SiH ₂ Cl ₂ gas after the reaction furnace to an atmosphere of NH ₃ gas The reason for avoiding the formation of tungsten silicide is that the formation of tungsten silicide complicates the etching process for the multilayer film and increases the resistance of the refractory metal film, although slightly. It is.

FIG. 2 shows the result of AES analysis of the multilayer film formed according to the first embodiment. As can be seen from FIG. 2, between the refractory metal film 5 and the first silicon nitride film 6. No abnormal reaction layer made of tungsten, silicon, nitrogen and oxygen is formed.

As described above, according to the first embodiment, the oxygen concentration is such that an oxide film is not formed on the surface of the high melting point metal film 5, that is, the reaction furnace kept in an atmosphere containing almost no oxygen. The silicon substrate 1 on which the refractory metal film 5 is formed is put into the reaction furnace held in the reactor, and the surface of the refractory furnace, that is, the surface of the refractory metal film 5 is kept in an atmosphere containing almost no oxygen. Since the silicon nitride film 6 is formed in a reaction furnace maintained at an oxygen concentration such that an oxide film is not formed in a portion, an abnormal reaction layer is not formed at the interface between the refractory metal 5 and the silicon nitride film 6. .

Accordingly, the resistance value of the refractory metal film 5 does not increase, and the pattern obtained by patterning the refractory metal film 5 does not have a non-uniform shape.

[0045] Particularly, in the first embodiment, after the reaction furnace to an atmosphere of NH ₃ gas, NH ₃ in the reactor
For forming a silicon nitride film 6 by introducing gas and a source gas of SiH ₂ Cl ₂ gas, the tungsten reacts with tungsten SiH ₂ Cl ₂ constituting the source gas constitutes a refractory metal film 5 The situation in which silicide is formed can be avoided.

(Second Embodiment) Hereinafter, a method for manufacturing a semiconductor device according to a second embodiment of the present invention will be described with reference to FIG.

First, as in the first embodiment, a silicon oxide film 2, a polycrystalline silicon film 3, a barrier metal layer 4, and a high melting point metal such as tungsten are formed over the entire surface of a silicon substrate 1. A melting point metal film 5 is sequentially deposited.

Next, the interior of the load lock chamber provided adjacent to the reactor is replaced with nitrogen gas to reduce the oxygen concentration in the load lock chamber to 1 ppm or less. Then, the silicon substrate 1 on which the high melting point metal film 5 is formed is loaded.

Thus, no oxide film is formed on the surface of the refractory metal film 5 inside the load lock chamber. In the second embodiment, the oxygen concentration in the load lock chamber is set to 1 ppm or less. However, if the oxygen concentration in the load lock chamber is about 40 ppm or less,
No oxide film is formed on the surface of the refractory metal film 5.

Next, after transferring the silicon substrate 1 from the load lock chamber to the reactor at a temperature of about 600 ° C. and reduced pressure, the temperature in the reactor is maintained at 760 ° C. H ₂ gas and H ₂ O gas are introduced at a pressure ratio of about 1: 1. As a result, the oxide film of the refractory metal, such as a tungsten oxide film, formed on the surface of the refractory metal film 5 is reduced, so that almost no oxide film is formed on the surface of the refractory metal film 5.

Next, while keeping the temperature inside the reactor at 600 ° C., NH ₃ gas at a flow rate of 600 sccm
Pour for about a minute. Thereafter, the temperature in the reaction furnace was increased to 760 ° C., and the flow rate of NH 2 was set to 600 sccm in the reaction furnace.
By introducing ₃ gas and SiH ₂ Cl ₂ gas at a flow rate of 60 sccm, a first silicon nitride film 6 is formed on the high melting point metal film 5 by LP-CVD under a total pressure of 40 Pa. In this case, the reason why the source gas composed of the NH ₃ gas and the SiH ₂ Cl ₂ gas is introduced after the atmosphere in the reactor is made of the NH ₃ gas is that SiH ₂ Cl ₂ reacts with tungsten constituting the high melting point metal film. This is to avoid the formation of tungsten silicide.

Next, a multilayer film composed of the silicon oxide film 2, the polycrystalline silicon film 3, the barrier metal layer 4, the refractory metal film 5, and the first silicon nitride film 6 is patterned by a method similar to the conventional method. After forming a gate electrode composed of the polycrystalline silicon film 3, the barrier metal layer 4, and the refractory metal film 5, the silicon substrate 1 is formed using the gate electrode as a mask.
Then, an impurity such as As is ion-implanted at an energy of about 20 keV, and thereafter, LP-CVD is performed over the entire surface.
After depositing a second silicon nitride film having a thickness of about 100 nm by the method, the second silicon nitride film is anisotropically etched to form a second silicon nitride film on the side surface of the gate electrode. A sidewall is formed (see FIG. 3B).

In the step of forming the second silicon nitride film by the LP-CVD method, the silicon substrate 1 is kept at about 600 ° C. from the load lock chamber similarly to the step of forming the first silicon nitride film 6. After being transferred into the reactor which is maintained at a temperature of and reduced in pressure, the temperature in the reactor is raised to 600 ° C.
NH flow 600sccm into the reactor while maintaining the ₃
Let the gas flow for about 5 minutes. Thereafter, the temperature in the reactor was reduced to 76
Raise the temperature to 0 ° C and set the flow rate in the reactor at 600 scc.
m 2 NH ₃ gas and a flow rate of 60 sccm SiH ₂ Cl ₂ gas are introduced to form a second silicon nitride film on the refractory metal film 5 at a total pressure of 40 Pa by LP-CVD.
The film is formed by a method. In this case, the reason why the source gas composed of the NH ₃ gas and the SiH ₂ Cl ₂ gas is introduced after the atmosphere in the reactor is made of the NH ₃ gas is that SiH ₂ Cl ₂ reacts with tungsten constituting the high melting point metal film. This is to avoid the formation of tungsten silicide.

Next, as in the conventional method, after forming an impurity diffusion layer serving as a source / drain, a contact and a metal wiring are formed (FIGS. 3B and 3C and FIG. 4).
(See (a) and (b)).

As described above, according to the second embodiment, the oxygen concentration is such that an oxide film is not formed on the surface of the high melting point metal film 5, that is, the reaction furnace kept in an atmosphere containing almost no oxygen. The silicon substrate 1 on which the refractory metal film 5 is formed is put into the reaction furnace held in the reactor, and the surface of the refractory furnace, that is, the surface of the refractory metal film 5 is kept in an atmosphere containing almost no oxygen. Since the silicon nitride film 6 is formed in a reaction furnace maintained at an oxygen concentration such that an oxide film is not formed in a portion, an abnormal reaction layer is formed at the interface between the high melting point metal film 5 and the silicon nitride film 6. Not done.

Therefore, the resistance value of the refractory metal film 5 does not increase and the pattern obtained by patterning the refractory metal film 5 does not have a non-uniform shape.

In particular, in the second embodiment, after removing the oxide film formed on the surface of the refractory metal film 5 in an atmosphere of a reducing gas, NH ₃ gas and SiH ₂ gas are introduced into the reaction furnace. In order to form the silicon nitride film 6 by introducing a source gas composed of a mixed gas with Cl ₂ gas, the oxide film formed on the surface of the refractory metal film 5 before the silicon nitride film 6 is introduced into the reactor is also required. Since it can be removed, a situation where an abnormal reaction layer is formed at the interface between the refractory metal film 5 and the silicon nitride film 6 can be more reliably prevented. That is, when the refractory metal oxide film is exposed to an oxygen gas having a certain concentration at a high temperature of 600 ° C. or higher at a high temperature of 600 ° C. or more, the refractory metal and oxygen react with each other to form an oxide film. When the refractory metal film is exposed to the atmosphere at room temperature, almost no oxide film is formed, but depending on the conditions, a slight oxide film may be formed on the surface of the refractory metal film. is there. In the second embodiment, even a slight oxide film formed on the surface of the refractory metal film is removed.

In the first and second embodiments,
The silicon substrate 1 was transferred from the load lock chamber in which the oxygen concentration was kept at 1 ppm or less to the reaction furnace. The oxygen concentration in the load lock chamber may be 1 ppm or more and about 40 ppm or less. It may be directly charged into the reactor without passing through the load lock chamber. In this case, the temperature and the oxygen concentration in the reaction furnace are maintained such that an oxide film of the high melting point metal is hardly formed on the surface of the high melting point metal film 5, and then the silicon substrate 1 is placed in the reaction furnace. It is necessary to input.

Further, in the first and second embodiments, the case where the gate electrode is formed by etching the multilayer film has been described. Alternatively, the multilayer film may be etched into a predetermined pattern shape. The present invention can be applied to the case of forming a metal wiring such as a bit line of a DRAM.

In the first and second embodiments, a tungsten film is used as the refractory metal film, but a titanium film, a cobalt film, a nickel film, or a molybdenum film may be used instead.

In the first and second embodiments, a multilayer structure composed of a refractory metal film / barrier metal layer / polycrystalline silicon film is used as the multilayer film. A laminated structure composed of a film / barrier metal layer may be used.

Further, in the first and second embodiments, a silicon nitride film is formed on the refractory metal film by LP-CVD.
Although the case where the film is formed by the method has been described, the present invention can be applied to a case where a plasma TEOS film is formed by the LP-CVD method on the refractory metal film instead.

[0063]

According to the method of manufacturing a semiconductor device of the present invention, a semiconductor substrate is put into a reaction furnace maintained in an atmosphere having an oxygen concentration such that an oxide film is not formed on the surface of a high melting point metal film. Since an abnormal reaction layer is not formed at the interface between the refractory metal film and the silicon nitride film because the silicon nitride film is formed by the chemical vapor deposition method, silicon is formed on the refractory metal film by the chemical vapor deposition method. Despite the formation of the nitride film, the resistance value of the refractory metal film does not increase and the pattern shape when the refractory metal film is patterned does not become uneven.

In the method of manufacturing a semiconductor device according to the present invention,
Deposition process, after the inside of the reaction furnace in an atmosphere of NH ₃ gas and comprising the step of introducing a source gas comprising a NH ₃ gas and SiH ₂ Cl ₂ gas into the reaction furnace, constitutes a source gas SiH ₂ Cl ₂ can be prevented from reacting with the refractory metal constituting the refractory metal film to form silicide of the refractory metal on the surface of the refractory metal film.

In the method of manufacturing a semiconductor device according to the present invention,
When the film forming step includes a step of introducing a source gas into the reaction furnace after removing the oxide film formed on the surface portion of the refractory metal film in a reducing gas atmosphere, Since even the slight oxide film formed on the surface of the refractory metal film before can be removed, the situation where an abnormal reaction layer is formed at the interface between the refractory metal film and the silicon nitride film is more reliably prevented. can do.

In the method of manufacturing a semiconductor device according to the present invention,
After the oxide film formed on the surface of the high melting point metal film is removed in a reducing gas atmosphere, the inside of the reaction furnace is changed to an NH ₃ gas atmosphere, and then the source is placed in the reaction furnace. Including the step of introducing a gas, it is possible to more reliably prevent an abnormal reaction layer from being formed at the interface between the refractory metal film and the silicon nitride film and to silicide the refractory metal on the surface of the refractory metal film. A situation in which an object is formed can be avoided.

[Brief description of the drawings]

FIG. 1 is a sectional view of a multilayer film obtained by a method of manufacturing a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an AES analysis result of a multilayer film obtained by the method for manufacturing a semiconductor device according to the first embodiment of the present invention.

FIGS. 3A to 3C are cross-sectional views showing steps of a conventional example, and a method of manufacturing a semiconductor device according to the first and second embodiments of the present invention.

FIGS. 4A and 4B are cross-sectional views showing steps of a conventional method for manufacturing a semiconductor device according to first and second embodiments of the present invention.

FIGS. 5A and 5B are cross-sectional views showing a conventional example, and a method of forming a self-aligned contact hole in a method of manufacturing a semiconductor device according to first and second embodiments of the present invention. It is.

FIG. 6 illustrates a conventional method for manufacturing a semiconductor device,
FIG. 3 is a cross-sectional view of a multilayer film when a silicon nitride film is formed by a CVD method.

FIG. 7 is a cross-sectional view of a conventional method of manufacturing a semiconductor device;
FIG. 3 is a cross-sectional view of a multilayer film when a silicon nitride film is formed by a CVD method.

FIG. 8 is a cross-sectional view of a conventional method for manufacturing a semiconductor device;
FIG. 9 is a diagram illustrating an AES analysis result of a multilayer film when a silicon nitride film is formed by a CVD method.

FIG. 9 is a cross-sectional view of a conventional method of manufacturing a semiconductor device;
FIG. 9 is a diagram illustrating an AES analysis result of a multilayer film when a silicon nitride film is formed by a CVD method.

FIG. 10 shows a conventional method for manufacturing a semiconductor device,
FIG. 11 is a diagram showing an X-ray analysis result of a multilayer film when a silicon nitride film is formed by a CVD method.

FIG. 11 is a cross-sectional view of a conventional method for manufacturing a semiconductor device;
FIG. 11 is a diagram showing an X-ray analysis result of a multilayer film when a silicon nitride film is formed by a CVD method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Silicon oxide film 3 Polycrystalline silicon film 4 Barrier metal layer 5 High melting point metal film 6 First silicon film 10 Silicon substrate 11 Element isolation region 12 Silicon oxide film 13 Polycrystalline silicon film 14 Barrier metal layer 15 High melting point Metal film 16 Protective film 17 Gate electrode 18 Side wall 19 Impurity diffusion layer 19a Low concentration impurity diffusion region 19b High concentration impurity diffusion region 20 Silicide layer 21 Interlayer insulating film 22 Contact hole 23 Metal wiring 24 Contact

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[Procedure amendment]

[Submission date] December 8, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

Claims (4)

[Claims] 1. A semiconductor substrate on which a refractory metal film serving as a gate electrode or a metal wiring is formed is kept in an atmosphere having an oxygen concentration such that an oxide film is not formed on the surface of the refractory metal film. Via a load lock chamber, a substrate loading step of loading into a reaction furnace maintained in an atmosphere having an oxygen concentration such that an oxide film is not formed on the surface portion of the high melting point metal film; and Introducing a source gas containing nitrogen and silicon into the reaction furnace, and forming a silicon nitride film on the refractory metal film by a chemical vapor deposition method. Manufacturing method of a semiconductor device. Wherein said film-forming step, NH ₃ into the reaction furnace
The interior of the reaction chamber by introducing the gas after the atmosphere of the NH ₃ gas, NH ₃ gas into the reaction furnace and SiH ₂ Cl ₂
2. The method for manufacturing a semiconductor device according to claim 1, further comprising a step of introducing the source gas comprising a gas mixture with a gas. 3. The method according to claim 1, wherein the film forming step includes: holding the semiconductor substrate in an atmosphere of a reducing gas to remove an oxide film formed on a surface of the high melting point metal film; 2. The method according to claim 1, further comprising a step of introducing the source gas. 4. The method according to claim 1, wherein the step of depositing includes removing the oxide film formed on the surface of the refractory metal film while holding the semiconductor substrate in an atmosphere of a reducing gas, and then placing the semiconductor substrate in the reaction furnace. A step of introducing NH ₃ gas to change the inside of the reaction furnace to an atmosphere of NH ₃ gas, and thereafter introducing the source gas composed of a mixed gas of NH ₃ gas and SiH ₂ Cl ₂ gas into the reaction furnace The method for manufacturing a semiconductor device according to claim 1, comprising: