JPH09237769A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable smooth advancement of silicide reaction and improvement of device performances by suppressing mixing of impurities (oxygen) into metallic wiring material, in particular, into titanium film. SOLUTION: A titanium film (Ti film) 20 is formed to cover the entire surface of a silicon substrate 11, and then a titanium nitride film (TiN film) 21 is continuously formed on the titanium film 20 by a sputtering process. At this time, the titanium nitride film 21 containing a less amount of oxygen can be formed by controlling a flow ratio (Ar/N2 ) of discharge gases. After formation of the titanium nitride film 21, first-time heat treatment causes a silicide reaction at a contact surface between the titanium film 20 and silicon substrate 11, thus forming a silicide film (TiSi2 film) 19. Thereafter second-time heat treatment is carried out over the silicide film 19 to provide its low resistance thereto.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device manufactured by forming a metal film such as a titanium film electrically connected to a semiconductor substrate made of a silicon material on the semiconductor substrate. More particularly, the present invention relates to a method for manufacturing a semiconductor device in which a silicide film having a low resistance is formed by causing a silicide reaction by heat treatment.

[0002]

2. Description of the Related Art Recently, VLSI (Large Scale Integrat)
ed circuit) with higher integration, contact holes to obtain electrical connection between the semiconductor substrate and the wiring formed above it, via holes and through holes to obtain electrical connection between multilayer wiring The holes are also miniaturized. Under the 0.25 μm rule, the aspect ratio of these contact holes, via holes, and through holes (hereinafter also collectively referred to as connection holes) exceeds 2. That is, the depth ratio of the connection hole is larger than the width.

Usually, in order to form such a connection hole, first, an insulating layer is formed on a semiconductor substrate (silicon substrate) or a lower wiring layer, and then an opening is formed in the insulating layer. After that, a metal wiring material is deposited on the insulating layer including the opening by, for example, a sputtering method (sputtering method). In this way, the inside of the opening is filled with the metal wiring material to complete the connection hole.

However, as described above, when the aspect ratio is high, the metal wiring material is not deposited on the bottom of the opening due to the so-called shadowing effect, or the metal of sufficient thickness is provided near the bottom of the side wall of the opening. There is a problem that the wiring material is not formed. Here, the shadowing effect is
This is a phenomenon in which sputtered particles that enter the opening during sputtering are not partially deposited in an optically shadowed area in the opening.

When such a shadowing effect occurs, the reliability of the electrical connection in the contact hole is lowered and the performance of the device is deteriorated.

In particular, in order to make the electrical connection with silicon (Si), which is a semiconductor substrate, smooth, a sufficient amount of metal wiring material is deposited on the bottom of the opening, and the metal and silicon are heat-treated by heat treatment. It is important that a sufficient silicide reaction occurs between them to form a good silicide film. When a good silicide film is formed, the contact resistance with the diffusion layer in the silicon substrate decreases and the interdiffusion barrier (
It can have a function as a barrier layer.

At present, as a metal for forming such a silicide film, it has excellent adhesion to a silicon substrate,
In addition, titanium (Ti), which has a small contact resistance with silicon, is often used. This titanium film is generally formed by a sputtering method. Further, a titanium nitride film (TiN) having an excellent barrier effect may be formed on this titanium film by a sputtering method in a nitrogen atmosphere.

[0008]

However, the metal wiring material such as titanium as described above contains a large amount of impurities such as oxygen when deposited by the sputtering method under the conventional conditions. Therefore, if heat treatment is applied after film formation,
Although a silicide reaction occurs, the reaction is suppressed,
There is a problem that a good silicide film cannot be formed. Hereinafter, this point will be specifically described.

That is, as shown in FIG. 5A, after a titanium film (Ti film) 102 is formed on a semiconductor substrate (silicon substrate) 101 by a sputtering method, it is exposed to the atmosphere, and then nitrogen (N) ₂ ) When heat treatment is performed at a predetermined temperature in the atmosphere, a silicide reaction occurs as shown in FIG. As a result, a silicide film (TiSi ₂ film) 103 is formed on the surface of the semiconductor substrate 101, and an oxide film (TiO _X film) 104 and a nitride film are formed on the silicide film 103.
The (TiN film) 105 is formed in this order. In this method, the titanium film 102 formed by the sputtering method reacts with oxygen in the atmosphere after opening to the atmosphere to form an oxide film 104, and a large amount of oxygen penetrates into the titanium film, resulting in the formation of silicon and titanium. The silicidation reaction between the two is suppressed.

Further, as shown in FIG. 6A, a titanium nitride film (TiN film) 106 as a diffusion barrier layer (barrier metal) is continuously formed on the titanium film 102 by a sputtering method. Then, when a predetermined heat treatment is performed in a nitrogen (N ₂ ) atmosphere, a silicide reaction occurs as shown in FIG. 6B. As a result, a silicide film (TiSi ₂ film) 103 is formed on the surface of the semiconductor substrate 101, and an oxide film (TiO _x ) having a segregated oxygen distribution is formed between the silicide film 103 and the nitride film (TiN film) 106. Membrane) 107
Is formed. In this method, since the oxygen content in the titanium nitride film 106 formed by the sputtering method is large, the oxide film 10 is formed at the interface between the silicide film 103 and the nitride film 106.
7 is formed, a large amount of oxygen penetrates into the titanium film, and as a result, the silicidation reaction between silicon and titanium is suppressed.

When the silicidation reaction is suppressed in this way, a good silicide film 103 (that is, a low resistance structure) cannot be realized, and the silicon substrate 10 cannot be realized.
There is a problem in that the reliability of the electrical connection between the wiring 1 and the wiring is reduced, and as a result, the performance of the device is deteriorated.

The present invention has been made in view of the above problems, and an object thereof is to suppress mixing of impurities into a metal wiring material, particularly a titanium film, and to allow a silicide reaction to proceed smoothly, thereby improving device performance. It is an object of the present invention to provide a method of manufacturing a semiconductor device that can improve

[0013]

According to the method of manufacturing a semiconductor device of the present invention, a first metal film electrically connected to the semiconductor substrate is formed on the surface of the semiconductor substrate made of a silicon material. And a step of, after forming the first metal film, continuously forming a second metal film having a function of suppressing mixing of impurities (oxygen) into the first metal film thereon. After forming the second metal film, heat treatment is performed to form a silicide film between the semiconductor substrate and the first metal film.

In this method of manufacturing a semiconductor device, when the first metal film and the second metal film are continuously formed and then heat treatment is performed, a gap between the semiconductor substrate (silicon substrate) and the first metal film is formed. However, since the second metal film has a function of suppressing the mixing of impurities into the first metal film at this time, the mixing of impurities into the first metal film is suppressed. It This allows the silicide reaction to proceed smoothly.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment] In the present embodiment,
A titanium film (Ti film) is used as the first metal film, and a titanium nitride film (TiN film) is used as the second metal film.
2 shows an example in which the metal film is formed by a sputtering method in which the flow rate ratio of the discharge gas is controlled.

FIG. 1 shows a sectional structure of a semiconductor device according to the first embodiment, for example, an N-channel type MOS (Metal Oxide Semiconductor) transistor having a salicide structure. This MOS transistor is provided in an active region defined by a thick field insulating film (SiO ₂ film) 12 selectively formed on a P-type silicon substrate 11, and has a source region 13,
The drain region 14 and the gate electrode 16 provided so as to face the channel region 15 between the source region 13 and the drain region 14.

The field insulating film (SiO ₂ film) 12 is formed by, for example, a LOCOS (Local Oxidation of Silicon) method. The source region 13 and the drain region 14 are each formed of an N ⁺ -type impurity region, have a so-called LDD (Lightly Doped Drain) structure, and have a shallow junction depth with the channel region 15 (N ⁻ -type low concentration layer). Type impurity regions) 13a, 13b are formed. The gate electrode 16 has a polycide structure including a conductive polycrystalline silicon film 16a and a silicide film (WSi film) 16b formed on the silicon substrate 11 with a gate insulating film (SiO ₂ film) 17 interposed therebetween. An offset oxide film (SiO ₂ film) 18a is formed on the gate electrode 16 and, for example, a silicon nitride film (Si ₃ N ₄ film) is formed on both sides.
A side wall (side wall) 18b is formed.

A sidewall 18 is formed on the surface of the silicon substrate 11.
As described above, the silicide film (TiSi ₂ film) 19 is formed between b and the field oxide film 12 to reduce the resistance between the silicon substrate and the wiring layer. Although not shown, a wiring layer made of, for example, conductive polycrystalline silicon or aluminum is formed on the silicide film 19.

Next, FIGS. 2A to 2C and the previous FIG.
A method of manufacturing the semiconductor device having the above structure will be described with reference to FIG.

FIG. 2A shows a thick field insulating film (SiO 2) formed on the surface of a P-type silicon substrate 11 by the LOCOS method.
Film) 12 is selectively formed, and in the active region defined by the field insulating film (SiO ₂ film) 12,
The source region 13 and the drain region 14 are formed by the impurity diffusion method.
On the silicon substrate 11 between the source region 13 and the drain region 14 by CVD (Ch
A gate electrode 16 made of a conductive polycrystalline silicon film 16a and a silicide film (WSi film) 16b is formed by using a known method such as an emical vapor deposition method or a sputtering method, and the upper surface of the gate electrode 16 is offset. Oxide film
(SiO ₂ film) 18a and the side wall surface is covered with a side wall (side wall) 18b.

From this state, in the present embodiment, as shown in FIG. 2B, the silicon substrate 11 including the gate electrode 16 and the field insulating film 12 as the first metal film is formed by the sputtering method. For example, a film thickness of 3 on the surface of
A titanium film (Ti film) 20 having a thickness of 0 nm is formed. The film forming conditions at this time are as follows, for example.

[Ti Film Sputtering Conditions] Discharge gas: Argon (Ar) = 100 sccm Container pressure: 0.4 Pa Power: Direct current (DC) = 5 kW Ambient temperature: 150 ° C.

After the titanium film 20 is formed, it is continuously (that is,
A titanium nitride film (TiN film) 21 having a film thickness of 10 nm, for example, is formed as a second metal film in the same vacuum.
The titanium nitride film 21 has a function as a conventional diffusion barrier layer (barrier metal) and, unlike the conventional one, has a small oxygen content. Therefore, the titanium nitride film 21 contains impurities (oxygen) from the titanium nitride film 21 to the titanium film 20. ) Has a function of suppressing the mixture.

The film forming conditions at this time are as follows, for example. In the present embodiment, in particular, the titanium nitride film 21 having a low oxygen content is formed by controlling the flow rate ratio (Ar / N ₂ ) of the discharge gas to form the film.

[TiN Film Sputtering Conditions] Discharge gas: Argon (Ar) = 55 sccm, Nitrogen (N ₂ ) =
55sccm Container internal pressure: 0.4Pa Electric power: Direct current (DC) = 5kW Ambient temperature: 150 ° C

After the titanium film 20 and the titanium nitride film 21 are continuously formed in this manner, the first heat treatment is performed as shown in FIG. 2 (c). This first heat treatment was performed at a temperature of 7 in a nitrogen atmosphere (N ₂ = 2000 sccm).
It is performed at a temperature of 00 ° C or lower, for example, 650 ° C. By performing such heat treatment, the titanium film 20 and the silicon substrate 1
A silicide reaction occurs at the contact surface with 1 to form a silicide film (TiSi ₂ film) 19. At this time, since the titanium nitride film 21 on the titanium film 20 has a low oxygen content, the amount of oxygen that diffuses from the titanium nitride film 20 into the titanium film 21 by heat treatment and is intruded is greatly reduced compared to the conventional case. Therefore, the silicide reaction between titanium and silicon proceeds smoothly, and a good silicide film 19 can be obtained.

Next, as shown in FIG. 2D, for example, by wet etching using a mixed solution of ammonia and hydrogen peroxide, etc., on the gate electrode 16 and the field insulating film 1.
The titanium film 20 and the titanium nitride film 21 on 2 are selectively removed in order to leave the silicide film 19 on the source region 13 and the drain region 14, respectively. Then, each silicide film 1 on the source region 13 and the drain region 14
In order to reduce the resistance of No. 9, the second heat treatment is performed.
This second heat treatment was performed in a nitrogen atmosphere (N ₂ = 2000 sc
cm) in a temperature of 750 ° C. or higher, for example, 800 ° C. By performing such a heat treatment, the silicide reaction can be further promoted, the resistance of the silicide film 19 can be reduced, and the structure shown in FIG. 1 can be obtained.

As described above, in the present embodiment, the titanium nitride film 21 as the diffusion barrier layer is continuously formed on the titanium film 20 which causes the silicide reaction, and at the time of forming the titanium nitride film 21, Argon (Ar) and nitrogen (N ₂ ) = 55 sccm are used as the discharge gas, and the flow rate ratio (Ar / N ₂ ) is controlled (specifically, Ar / N ₂ = 55 sccm).
Since the sputtering method of cm / 55 sccm = 1) is used, the titanium nitride film 21 having a low oxygen content can be formed. Therefore, the penetration of oxygen into the titanium film 20 can be suppressed and the silicide reaction can proceed smoothly, so that a good silicide film 19 can be formed.

Now, here, the discharge gas flow rate ratio (Ar / N
₂ ) An example was given, but by controlling this flow rate ratio so that the ratio of argon (Ar) becomes higher, a titanium nitride film with a high titanium content and therefore a low oxygen content is formed. be able to. On the other hand, a titanium nitride film formed by a sputtering method with a high nitrogen (N ₂ ) ratio is more preferable than a titanium nitride film formed with a high argon (Ar) ratio as in this embodiment. Because it is a porous film,
Impurities such as oxygen are easily mixed, and the oxygen content is high. Therefore, when heat treatment is performed after film formation as described above (FIG. 6), a large amount of oxygen in the titanium nitride film diffuses into the titanium film, which suppresses the silicide reaction and adversely affects it.

Here, in the present specification, "a low oxygen content" in the titanium nitride film means that when the oxygen content in the film is less than 9 at% (atoms%), preferably 4 at.
% Or less. On the other hand, the phrase "the oxygen content is large" means that the oxygen content in the film is 9 at% or more. The control conditions for obtaining the titanium nitride film in such a range are shown below in the case of using a general sputtering apparatus.

Flow rate ratio (Ar / N ₂ ) = 9.3 (eg Ar = 10)
0 sccm, N ₂ = 12 sccm) or more, preferably 20
By setting (for example, Ar = 100 sccm, N ₂ = 5 sccm) or more, it is possible to form a titanium nitride film having a high titanium content (that is, a low oxygen content). Is Ar = 10-200s
It is desirable to set ccm and N _{2 in} the range of 1 to 100 sccm. On the other hand, when Ar / N ₂ ≉9.3, the titanium nitride film has a large nitrogen content (that is, a large oxygen content).

[Second Embodiment] In the first embodiment, an example in which the present invention is applied to a salicide structure MOS transistor has been described, but in the second embodiment, FIG. An example applied to a buried structure of a connection hole (contact hole) between a silicon substrate and a wiring will be described with reference to FIG. Here, first, an example in which the present invention is applied to a general process will be described.

In this embodiment, as shown in FIG. 3A, a BPSG (Boro-Phospho-Silic) film having a thickness of 1.0 μm is formed on the silicon substrate 31 by, for example, the CVD method.
After forming the insulating film 32 made of an ate glass film, a contact hole 33 is formed in the insulating film 32 by lithography and etching techniques. The diameter of the contact hole 33 is, for example, 0.4 μm, and the aspect ratio is 2
~ 3. Then, on the silicon substrate 31 including the contact holes 33, a first metal film having a film thickness of, for example, 30 is formed by a directional sputtering apparatus using a collimator plate.
A titanium film (Ti film) 34 having a thickness of 30 nm is formed. The film forming conditions at this time are as follows.

[Ti Film Sputtering Conditions] Discharge gas: Argon (Ar) = 48 sccm Container pressure: 0.3 Pa Power: Direct current (DC) = 5 kW Atmosphere temperature: 150 ° C.

After the titanium film 34 is formed, it is continuously (that is,
In the same vacuum), for example, a titanium nitride film (TiN film) 35 as a second metal film having a film thickness of 70 nm is formed.
This titanium nitride film 35 has the function of suppressing the entry of impurities (oxygen) into the titanium film 34, as with the titanium nitride film 21 described in the first embodiment.

The film forming conditions at this time are as follows.
Also in this embodiment, as in the first embodiment,
By controlling the flow rate ratio of the discharge gas and forming the film, the titanium nitride film 35 having a low oxygen content can be formed.

[TiN Film Sputtering Conditions] Discharge gas: Argon (Ar) = 75 sccm, Nitrogen (N ₂ ) =
75 sccm Container pressure: 0.6 Pa Electric power: Direct current (DC) = 6.5 kW Ambient temperature: 150 ° C.

When a directional sputtering device is used,
In order to obtain the titanium nitride film 35 having a low oxygen content,
Flow rate ratio (Ar / N ₂ ) = 1.0 (eg Ar = 75 sccm, N ₂
= 75 sccm) or more, preferably Ar / N ₂ = 2 or more. In this case, the gas flow rate is Ar = 10 to 200 scc
It is desirable to set m and N _{2 in} the range of 10 to 200 sccm. On the other hand, when Ar / N _{2 is} less than 1.0, the titanium nitride film has a large nitrogen content (that is, a large oxygen content).

After the titanium film 34 and the titanium nitride film 35 are continuously formed in the contact hole 33 in this manner, heat treatment is performed as shown in FIG. 3B. This heat treatment is performed in a nitrogen atmosphere (N ₂ = 30 sccm) at a temperature of 650 ° C., for example. By performing such a heat treatment, a silicide reaction occurs at the contact surface between the titanium film 34 and the silicon substrate 31, and the contact hole 33
A silicide film (TiSi ₂ film) 36 is formed at the bottom of the. At this time, the titanium nitride film 35 having a low oxygen content is formed on the titanium film 34 by controlling the flow rate ratio (Ar / N ₂ ) of the discharge gas. The amount of oxygen that diffuses and enters the film 34 is small. Therefore, the silicide reaction between titanium and silicon proceeds smoothly at the bottom of the contact hole 33, and a good silicide film 36 can be obtained.

After the silicide film 36 is formed in this way, as shown in FIG. 3C, a metal film, for example, a tungsten film (W film) 37 is formed by the CVD method so as to fill the contact hole 33. .

[Modification of Second Embodiment] FIG. 4A
(C) represents a modification of the second embodiment. This example shows an example in which FIG. 3 is applied to a general process, while RTN (Rapid Thermal Nitridati) of Ti is used.
on) This is an example of applying the process. FIG. 3 (a)
The same components as in (c) to (c) will be assigned the same reference numerals and described below.

In this embodiment, as shown in FIG. 4A, after forming the contact hole 33 in the insulating film 32 on the silicon substrate 31, the collimating plate is formed on the silicon substrate 31 including the contact hole 33. A titanium film (Ti film) with a thickness of 70 nm is formed by the directional sputtering method using
41 is formed. The film forming conditions at this time are as follows.

[Ti Film Sputtering Condition] Discharge gas: Argon (Ar) = 48 sccm Container pressure: 0.3 Pa Power: Direct current (DC) = 5 kW Atmosphere temperature: 150 ° C.

After the titanium film 41 is formed, it is continuously (that is,
In the same vacuum), for example, a titanium nitride film (TiN film) 42 as a second metal film having a film thickness of 30 nm is formed.

The film forming conditions at this time are as follows.
Also in this embodiment, as in the first embodiment,
By controlling the flow rate ratio of the discharge gas and forming the film, the titanium nitride film 41 having a low oxygen content can be formed.

[TiN film sputtering conditions] Discharge gas: Argon (Ar) = 75 sccm, Nitrogen (N ₂ ) =
75 sccm Container pressure: 0.6 Pa Electric power: Direct current (DC) = 6.5 kW Ambient temperature: 150 ° C.

After the titanium film 41 and the titanium nitride film 42 are continuously formed in the contact hole 33 in this manner, the first heat treatment (annealing) is performed as shown in FIG. 4B. This heat treatment is performed in an argon atmosphere (Ar = 50
00 sccm) at a temperature of 650 ° C. for 30 seconds. By performing such a first heat treatment, a silicide reaction occurs at the contact surface between the titanium film 41 and the silicon substrate 31, and a silicide film (TiSi ₂ film) 43 is formed at the bottom of the contact hole 33. At this time, the titanium nitride film 42 having a low oxygen content is formed on the titanium film 41 by controlling the flow rate ratio (Ar / N ₂ ) of the discharge gas. The amount of oxygen that diffuses and enters the film 41 is small. Therefore, the silicide reaction between titanium and silicon proceeds smoothly at the bottom of the contact hole 33,
A good silicide film 43 can be formed.

After the first heat treatment, the second heat treatment (annealing) is performed as shown in FIG. This heat treatment is performed in an ammonia (NH ₃ ) atmosphere (NH ₃ = 2000 scc
m) at a temperature of 650 ° C for 30 seconds. As a result, a nitride layer (TiN film) is further formed on the surface of the titanium nitride film 42.

After the second heat treatment, as shown in FIG. 4D, the contact hole 33 is formed by, for example, the CVD method.
A metal film such as a tungsten film (W
A film) 44 is formed.

In this embodiment, since the titanium film 41 and the titanium nitride film 42 are continuously formed, the heat treatment is performed twice under different atmospheres, so that the silicide reaction proceeds more smoothly, Better silicide film 43
Can be obtained.

[Third Embodiment] Next, a third embodiment of the present invention will be described.
An embodiment will be described. In the present embodiment, in the salicide structure shown in FIG. 1, plasma CVD (Plasma Chemi) is used to form a titanium film as a first metal film and a titanium nitride film as a second metal film.
cal Vapor Deposition: The plasma chemical vapor deposition method is applied. Since the structure is the same as that of the first embodiment (FIGS. 1 and 2), the description thereof will be omitted.

In the present embodiment, the titanium film (Ti film) 20 and the titanium nitride film (TiN film) 21 shown in FIG.
The continuous film formation is performed by the plasma CVD method under the following conditions.

[Plasma CVD condition of Ti film] Reaction gas: titanium tetrachloride (TiCl ₄ ) / hydrogen (H ₂ ) / argon (Ar) Container pressure: 0.2 Pa Power: 3.0 kW Ambient temperature: 420 ° C. Film Thickness: 30 nm [Plasma CVD condition of TiN film] Reaction gas: titanium tetrachloride (TiCl ₄ ) / nitrogen (N ₂ ) / hydrogen (H ₂ ).
/ Argon (Ar) Pressure inside container: 0.1 Pa Electric power: 3.0 kW Ambient temperature: 420 ° C Film thickness: 70 nm

As a result of experiments, the titanium film and the titanium nitride film formed under such conditions each have a smaller oxygen content than the films obtained by the general sputtering method. Therefore, the silicide reaction proceeds smoothly by the heat treatment after the film formation, and a good silicide film can be obtained.

[Fourth Embodiment] Next, a fourth embodiment of the present invention will be described.
An embodiment will be described. In the first embodiment, the titanium nitride film having a low oxygen content is formed by the sputtering method in which the flow rate ratio (Ar / N ₂ ) of the discharge gas is controlled. However, in the present embodiment, the discharge gas is formed. The titanium nitride film having a low oxygen content is formed by controlling the total flow rate of. Since the structure of this embodiment is similar to that of the first embodiment, the description thereof is omitted.

In this embodiment, after the titanium film (Ti film) is formed as in the first embodiment, the titanium nitride film (TiN film) is continuously formed by the directional sputtering apparatus under the following conditions. To form.

[Directional Sputtering Conditions of TiN Film] Discharge gas: Argon (Ar) = 15 sccm, Nitrogen (N ₂ ) =
55 sccm Power: Direct current (DC) = 12 kW Ambient temperature: 200 ° C. Film thickness: 50 nm

In the present embodiment, in particular, by setting the total flow rate of the discharge gas to be Ar + N ₂ = 15 + 55 = 70 sccm or less, the pressure inside the container of the sputtering apparatus is 2.0 mTorr.
Below, the titanium nitride film formed under this pressure has a low oxygen content of 4.0 at% or less.
Therefore, the silicide reaction proceeds smoothly by the heat treatment after the film formation, and a good silicide film can be obtained.

Although the present invention has been described with reference to various embodiments, the present invention is not limited to the above embodiments, and various modifications can be made. For example, the conditions such as sputtering (temperature, gas flow rate, gas flow rate ratio, etc.) shown in the above embodiment are examples, and can be set to appropriate values. The point is that the second metal film having a low oxygen content must be formed to such an extent that the silicide reaction between the first metal film such as titanium and the silicon substrate is favorably performed in the subsequent heat treatment process. Good.

[0061]

As described above, according to the method of manufacturing the semiconductor device of the present invention, after the first metal film is formed on the surface of the semiconductor substrate formed of the silicon material, the first metal film is formed on the first metal film. Since the second metal film, which has a function of suppressing the entry of impurities into the metal film, is formed continuously, it is possible to prevent the entry of impurities into the first metal film when heat treatment is performed in a later step. It is suppressed, and a smooth silicide reaction proceeds between the semiconductor substrate (silicon substrate) and the first metal film,
A good silicide film can be formed. Therefore, it is possible to realize a low resistance structure in the connection hole and the like, and to improve the electrical connection, which can advantageously miniaturize the periphery of the connection hole and the like, and improve the reliability and performance of the device. Has the effect.

[Brief description of drawings]

FIG. 1 is a sectional view of an N-channel MOS transistor according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining the manufacturing process of the transistor of FIG. 1 focusing on the process of forming a silicide film.

FIG. 3 is a cross-sectional view illustrating a step of forming a silicide film in a contact hole according to the second embodiment of the present invention.

FIG. 4 is a sectional view for explaining a modified example of the second embodiment of the present invention.

FIG. 5 is a cross-sectional view for explaining a conventional silicide film forming step.

FIG. 6 is a cross-sectional view for explaining another conventional silicide film forming step.

[Explanation of symbols]

11 ... Semiconductor substrate (silicon substrate), 13 ... Source region, 14 ... Drain region, 16 ... Gate electrode, 19 ... Silicide film (TiSi ₂ film), 20, 34, 41 ... Titanium film (Ti film) (first Metal film) 21, 35, 42 ... Titanium nitride film (TiN film) (second metal film)

Claims (8)

[Claims] 1. A step of forming a first metal film electrically connected to the semiconductor substrate on a surface of the semiconductor substrate formed of a silicon material, and the step of forming the first metal film and then forming the first metal film. A step of continuously forming a second metal film having a function of suppressing the entry of impurities into the first metal film, and a step of heat-treating the second metal film, And a step of forming a silicide film between the semiconductor substrate and the first metal film. 2. The method of manufacturing a semiconductor device according to claim 1, wherein a film having a low oxygen content is used as the second metal film. 3. A film having a low oxygen content has an oxygen content of 9
3. The method for manufacturing a semiconductor device according to claim 2, wherein the content is less than at%. 4. A film having a low oxygen content has an oxygen content of 4
The method for manufacturing a semiconductor device according to claim 3, wherein the content is at% or less. 5. The method of manufacturing a semiconductor device according to claim 4, wherein the first metal film is a titanium film, and the second metal film having a low oxygen content is a titanium nitride film. 6. The titanium nitride film is formed by a sputtering method using argon (Ar) and nitrogen (N ₂ ) as a discharge gas, and the flow rate ratio (Ar / N ₂ ) of the gas is controlled. 6. The method of manufacturing a semiconductor device according to claim 5, wherein the oxygen content in the titanium nitride film is reduced. 7. The oxygen content in the titanium nitride film is set to 4 at% or less by forming the titanium nitride film using a plasma CVD (chemical vapor deposition) method. Item 6. A method of manufacturing a semiconductor device according to item 5. 8. The oxygen content in the titanium nitride film is set to 4 at% or less by forming the titanium nitride film by a sputtering method under a pressure condition of 2.0 mTorr or less. Item 6. A method of manufacturing a semiconductor device according to item 5.