JPH10144919A - Method for manufacturing mis transistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture MIS transistors which prevent generation of concave and convex parts in an interface between source and drain layers and a metal silicide film and have superior leak characteristic by relaxing, a stress generated in the interface between the source and drain layers and metal silicide film. SOLUTION: A cobalt film 12 is formed on an upper face of source and drain layers 8, and a titanium film 11 is formed on an upper face of this cobalt film 12 as a stress relaxing layer. The cobalt film 12 is heated and made to silicide-react to form a cobalt silicide film 8a. At this time, by forming the titanous film 11, with respect to a compression stress generated in an interface between the source and drain layers 8 and cobalt silicide film 8a, a drivers pulling stress can be applied to the cobalt silicide film 8a formed thereafter. Thereafter, the compression stress can be relaxed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a MIS transistor having a so-called salicide structure in which a high-melting metal silicide film is formed on the upper surfaces of a gate electrode, a source, and a drain layer. It is suitable.

[0002]

2. Description of the Related Art Conventionally, as a salicide process, a 10-nm-thick titanium film and a cobalt film are sequentially stacked on the surface of a single-crystal silicon substrate having a (100) plane orientation, and then subjected to a heat treatment to obtain a single crystal. There is a method of epitaxially growing a cobalt silicide film on the surface layer of a silicon substrate (see Reference: Appl. Phys. Lett. 58 (12) described by M. Lawrence and others).
25 March 1991 "Growth of
epitaxial CoSi ₂ onSi ”or
A. J. Vantomme et al. Appl. P
hys. 75 (8), 15 April 1994 "E
pitaxial CoSi ₂ filmson Si
(100) by solid-phase react
ion ").

According to this method, the cobalt silicide film is formed by single crystal growth according to the crystallinity of the underlying single crystal silicon substrate.

[0004]

However, when the cobalt silicide film is epitaxially grown by the above-mentioned method, the shape of the interface between the cobalt silicide film and the single crystal silicon substrate is not flat, and irregularities are generated. That has been confirmed. The reason why the interface becomes uneven is that the cobalt silicide film and the single crystal silicon substrate are not reacted when the cobalt film is silicided due to the difference in the coefficient of thermal expansion between the single crystal silicon substrate and the formed cobalt silicide film. It is presumed that stress is generated at the interface of.

When the above method is applied to the formation of a metal silicide film on a source / drain layer in a MOS transistor, the interface between the source / drain layer and the metal silicide film becomes uneven. Due to the unevenness, the metal silicide film partially approaches the PN junction of the source / drain layer and the single crystal silicon substrate, or reaches the PN junction, which causes a problem that the leak characteristic is deteriorated.

In view of the above, it is an object of the present invention to provide a method of manufacturing a MIS transistor having a good leak characteristic by relaxing a stress generated at an interface between a metal silicide film and a source / drain layer. .

[0007]

In order to achieve the above object, the following technical means are employed. According to the first to third aspects of the present invention, the refractory metal film (12) is formed on the upper surface of the source / drain layer (8), and the stress relaxation layer (13) is formed on the upper surface of the refractory metal film (12). ) Is formed. Then, a heat treatment is performed, and a source is applied in the stress relaxation layer (13).
The method is characterized in that the refractory metal film (12) undergoes a silicidation reaction while relaxing the stress generated at the interface between the drain layer (8) and the metal silicide film (8a) to form a metal silicide film (8a).

Specifically, as the stress relaxation layer (13), a metal thin film, for example, a titanium film, a tungsten film, or the like is applied, or a metal nitride film, for example, a titanium nitride film, A cobalt nitride film, a tungsten nitride film, an aluminum nitride film, or the like can be used. That is, during the heat treatment, the substrate (1) and the formed metal silicide film (8
In a), thermal expansion is attempted, but since the coefficients of thermal expansion are different, stress is generated at the interface between the metal silicide film (8a) and the source and drain layers (8).

The stress can be relieved by forming the stress relieving layer (21), thereby generating irregularities at the interface between the metal silicide film (8a) and the source and drain layers (8). And the leakage current at the PN junction between the source / drain layer (8) and the substrate (1) can be suppressed. Specifically, as described in claim 2, the metal silicide film (8
When a stress is applied to the metal silicide film (8a) to offset the stress generated by the metal silicide film (8) with the metal silicide film (8a), the stress generated by the metal silicide film (8a) with the substrate (1) is reduced. Can be eased.

For example, when the metal silicide film (8a) generates a compressive stress on the substrate (1), a tensile stress acting in a direction opposite to the compressive stress is exerted on the metal silicide film (8a). By doing so, this compressive stress can be reduced. According to the present invention, the gate electrode (5) is formed on the upper surface of the substrate (1) via the gate insulating film (4), and the source and drain layers (8) are formed. . Then, a stress relaxation film (21) made of a compound of a plurality of substances is formed on the upper surfaces of the source and drain layers (8), and a high melting point metal film (22) is formed on the upper surface of the stress relaxation film (21). I do. Thereafter, heat treatment is performed to decompose the stress relaxation layer (21) into a plurality of substances. Then, any of the plurality of substances is left at the interface between the source / drain layer (8) and the metal silicide film (8a), and while the stress generated at this interface is alleviated, a silicidation reaction is caused to occur. Silicide film (8a)
Is formed.

As described above, by forming the stress relaxation film (21) between the refractory metal film (22) and the source / drain layer (8), the metal silicide film (8a) formed thereafter and the source Since the stress generated at the interface of the drain layer (8) can be reduced, the occurrence of unevenness at the interface between the metal silicide film (8a) and the source / drain layer (8) can be suppressed. Thereby, the leak current at the PN junction between the source / drain layer (8) and the substrate (1) can be suppressed.

More specifically, the stress relaxation film (21) is a metal compound film formed by combining at least two kinds of metals, for example, a titanium-tungsten compound film, a titanium-cobalt-tungsten film. Compound film, titanium / nickel / tungsten compound film, etc., as shown in claim 6,
A metal nitride film, for example, a titanium nitride film, a titanium / tungsten nitride film, a titanium / cobalt nitride film, a titanium / nickel nitride film, or the like can be used.

In the step of forming the metal silicide film (8a), the metal compound film or the metal nitride film is decomposed, and the decomposed metal or nitrogen remains on the surfaces of the source and drain layers (8). Membrane (8a)
Is formed. Further, the substrate (1) and the metal silicide film (8a) tend to thermally expand due to the heat treatment. However, since these substrates have different coefficients of thermal expansion, the metal silicide film (8a) and the source and drain layers (8) Stress occurs at the interface.

However, metal or nitrogen remaining on the surface of the source / drain layer (8) becomes wedges to relieve stress generated at the interface between the source / drain layer (8) and the metal silicide film (8a). Can be.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. (First Embodiment) FIGS. 1 and 2 show a manufacturing process in a case where the present invention is applied to a MOS transistor. Hereinafter, a manufacturing method in the present embodiment will be described with reference to FIGS.

First, the LDD (Light) shown in FIG.
(Doped Drain) structure is formed. That is, a LOCOS film 3 for element isolation is formed in a P-well layer 2 formed in a surface layer portion of a single crystal silicon substrate (hereinafter, referred to as a silicon substrate) 1. Then, a gate electrode 5 made of polysilicon electrically insulated via the gate oxide film 4 is formed. Then, ion implantation is performed using the gate electrode 5 as a mask to form the electric field relaxation layer 6.

Thereafter, a SiN film is formed on the entire upper surface, anisotropically etched, and a side wall film 7 is formed on the side of the gate electrode 5.
To form Then, after performing ion implantation using the gate electrode 5 and the side wall film 7 as a mask, heat treatment is performed to activate the ion-implanted impurities, thereby forming the source and drain layers 8. Thereby, the LD shown in FIG.
A D structure is formed.

Next, as shown in FIG. 1B, a titanium film 11, a cobalt film 12, and a titanium nitride film 13 are sequentially formed by sputtering. Then, the wafer is heat-treated at about 450 ° C. in a nitrogen gas atmosphere. As a result, the gate electrode 5, the source,
The surface layer of the drain layer 8 undergoes a silicidation reaction, and FIG.
As shown in (c), the cobalt silicide films 5a and 8a
Is formed.

At this time, cobalt in the cobalt film 12 diffuses in the titanium film 11 while diffusing in the titanium film 1.
1 to the lower layer to cause the silicidation reaction. Therefore, the cobalt silicide films 5a, 8a
After the formation, the cobalt film 12 moves to a lower layer of the titanium film 11 as a whole. However, the titanium film 11 that has moved to the upper layer of the cobalt film 12 is thereafter nitrided in a nitrogen gas atmosphere, and is integrated with the previously formed titanium nitride film 13.

Thereafter, as shown in FIG. 2A, the titanium nitride film 11 is removed by etching with an aqueous solution of ammonia and hydrogen peroxide, and the unreacted portion of the cobalt film 12 is removed with hydrochloric acid and peroxide. It is selectively etched away with a mixed solution of hydrogen water. Next, as shown in FIG. 2B, after a titanium nitride film 14 is formed again on the entire surface of the wafer, a heat treatment is performed at 750 ° C. for 30 seconds in a nitrogen gas atmosphere to form the cobalt silicide films 5a and 8a. Lower the resistance.

After that, the titanium nitride film 14 is removed by etching with a mixed solution of ammonia and hydrogen peroxide solution, as shown in FIG.
A MOS transistor having a salicide structure composed of the cobalt silicide films 5a and 8a as shown in FIG. By the way, when forming the cobalt silicide film 8a on the surface of the source / drain layer 8, the titanium nitride film 13 functions as a stress relaxation layer.

More specifically, since the silicon substrate 1 and the cobalt silicide film 8a formed during the heat treatment have different coefficients of thermal expansion, the cobalt silicide film 8a and the source,
Stress occurs at the interface with the drain layer 8. For example, when the coefficient of thermal expansion of the cobalt silicide film 8a is larger than the coefficient of thermal expansion of the silicon substrate 1,
a generates a tensile stress on the silicon substrate 1. Conversely, when the coefficient of thermal expansion of the cobalt silicide film 8a is smaller than the coefficient of thermal expansion of the silicon substrate 1, the cobalt silicide film 8a generates a compressive stress on the silicon substrate 1.

Therefore, even if the cobalt silicide film 8a attempts to generate a compressive stress or a tensile stress on the silicon substrate 1, if the stress is offset by the stress relaxation layer formed on the upper surface, the cobalt silicide film 8a
The stress generated at the interface between a and the source / drain layer 8 can be reduced. That is, when a tensile stress is generated as in the former case, a stress relaxation layer for generating a compressive stress corresponding to the magnitude of the tensile stress on the cobalt silicide film 8a is formed on the upper surface of the cobalt silicide film 8a. Form. When a compressive stress is generated as in the latter case, a stress relaxation layer for generating a tensile stress corresponding to the magnitude of the compressive stress on the cobalt silicide film 8a is provided on the upper surface of the cobalt silicide film 8a. Form.

Then, the titanium nitride film 1 shown in this embodiment
3, a titanium nitride film 13 is formed on an upper surface of the cobalt film 12 to generate a compressive stress (outwardly pointing arrow in FIG. 3) on the cobalt silicide film 8a as shown in FIG. When the film 8a generates a tensile stress (inward arrow in FIG. 3) on the silicon substrate 1, the tensile stress can be reduced.

As described above, the stress generated by the cobalt silicide film 8a on the silicon substrate 1 is relaxed, whereby the occurrence of irregularities at the interface between the cobalt silicide film 8a and the source / drain layer 8 can be suppressed. The leakage current at the PN junction between the source / drain layer 8 and the P well layer 2 can be suppressed. In the present embodiment, the cobalt silicide films 5a and 8a are used as the silicide films, but a nickel silicide film may be used.

The titanium nitride film 13 is used as a stress relaxation layer.
As described above, the type and magnitude of the stress generated by the silicide film on the silicon substrate 1 and the type and magnitude of the stress generated by the stress relieving layer on the silicide film are described above. Since it is determined by the size, it can be appropriately changed according to these. Specifically, if the stress relaxation layer is a metal film, it can be changed to a titanium film, a tungsten film, or the like, and if the metal nitride film is used, it can be changed to a cobalt nitride film, a tungsten nitride film, an aluminum nitride film, or the like. It is possible. Further, a composite made of any combination of these metal films and metal nitride films may be used.

For example, when a tungsten nitride film is applied to the stress relaxation layer and a nickel silicide film or a cobalt silicide film is applied to the silicide film, the tungsten nitride film generates a tensile stress on the nickel silicide film. In addition, when tungsten is applied to the stress relaxation layer and a nickel silicide film or a cobalt silicide film is applied to the silicide film, tungsten generates different stresses on these silicide films depending on film formation conditions. Compressive stress,
A tensile stress can be generated. (Second Embodiment) FIGS. 4 to 6 show a manufacturing process when the present invention is applied to a MOS transistor. Hereinafter, a manufacturing method in the present embodiment will be described with reference to FIGS.

First, the LDD structure shown in FIG. 4A is formed as in the first embodiment. Next, as shown in FIG. 4B, a titanium nitride film 21 and a cobalt film 22 are sequentially stacked by a sputtering method. At this time, the titanium nitride film 21 is formed with a smaller thickness than the cobalt film 22. Then, in a nitrogen gas atmosphere, the wafer is 450
Heat treatment at about ° C. As a result, the surface portions of the gate electrode 5 and the source / drain layers 8 where the silicon is exposed undergo a silicidation reaction to form cobalt silicide films 5a and 8a as shown in FIG.

Here, in the heat treatment, the titanium nitride film 21 undergoes a decomposition reaction to be decomposed into titanium and nitrogen. Then, cobalt in the cobalt film 22 diffuses in the titanium, reaches the gate electrode 5, the source and drain layers 8, and performs a silicidation reaction with silicon in these. Finally, the cobalt diffuses in the titanium, and all the cobalt enters the lower layer of the titanium.
However, cobalt cannot partially enter the underlayer of nitrogen. Therefore, as shown in FIG. 6, the nitrogen atoms 21a in the titanium nitride film 21 partially remain on the upper surfaces of the source and drain layers 8.

In this heat treatment, the cobalt film 2
Since the cobalt in Step 2 diffuses through the titanium formed by the decomposition of the titanium nitride film 21 and penetrates to the lower layer of titanium, after the formation of the cobalt silicide film 8a, the cobalt film 22 Move to lower level. Thereafter, the titanium is nitrided in a nitrogen gas atmosphere to form a titanium nitride film 23 on the upper surface of the cobalt film 22, as shown in FIG.

Thereafter, as shown in FIG. 5A, the titanium nitride film 23 is removed by etching with an aqueous solution of ammonia and hydrogen peroxide, and the unreacted portion of the cobalt film 22 is removed with hydrochloric acid and peroxide. It is selectively etched away with a mixed solution of hydrogen water. Next, at 750 ° C. and 30 ° C. in a nitrogen gas atmosphere.
Heat treatment for 2 seconds to form cobalt silicide films 5a and 8a.
To lower the resistance. At this time, as shown in FIG.
Since a titanium nitride film 24 is formed on the surfaces of the cobalt silicide films 5a and 8a, the titanium nitride film 24 is thereafter removed by etching with a mixed solution of ammonia and hydrogen peroxide solution, as shown in FIG. A MOS transistor having a salicide structure composed of cobalt silicide films 5a and 8a as shown in FIG.

Incidentally, the remaining nitrogen atoms 21a
When lowering the resistance of the cobalt silicide film 8a,
It functions to reduce stress at the interface between the cobalt silicide film 8a and the source / drain layer 8. Specifically, at the time of the heat treatment for lowering the resistance, the silicon substrate 1 and the formed cobalt silicide film 8a have different coefficients of thermal expansion. For this reason, as shown in the first embodiment, the cobalt silicide film 8a causes the silicon substrate 1 to have a compressive stress or a tensile stress (based on the thermal expansion coefficient between the cobalt silicide film 8a and the silicon substrate 1). (Arrow portion in FIG. 6).

At this time, the nitrogen atoms 21a remaining at the interface between the cobalt silicide film 8a and the source / drain layer 8
However, this prevents the cobalt silicide film 8a from expanding or contracting with respect to the silicon substrate 1 due to a hook like a wedge. Since the nitrogen is uniformly interposed in the titanium nitride film 21, the nitrogen remains in a state where it is sufficiently diffused at the lattice position where the above-mentioned stress can be relaxed.

As described above, by forming the titanium nitride film 21 under the cobalt film 22, nitrogen atoms remain at the interface between the cobalt silicide film 8a and the source / drain layer 8 during the silicidation reaction, thereby The stress generated at the interface between the cobalt silicide film 8a and the source / drain layer 8 can be reduced. Therefore, the occurrence of unevenness at the interface between the cobalt silicide film 8a and the source / drain layer 8 can be suppressed, and the leakage current at the PN junction between the source / drain layer 8 and the P well layer 2 can be suppressed.

In this embodiment, the cobalt silicide films 5a and 8a are used as the silicide films, but a nickel silicide film may be used. Further, the titanium nitride film 21 was formed between the cobalt film 22 and the source / drain layers 8, but instead of the titanium nitride film 21, a titanium-tungsten compound film, a titanium-nickel
A tungsten compound film, a titanium / cobalt / tungsten compound film, a titanium / tungsten nitride film, a titanium / cobalt nitride film, a titanium / nickel nitride film, or the like may be formed.

For example, when a titanium-tungsten compound film is applied, since tungsten molecules are large in size and cobalt is difficult to diffuse, tungsten remains on the surfaces of the source and drain layers 8. Like wedge, it relieves stress as wedge. In this case as well, cobalt or nickel diffuses in the titanium which has undergone the decomposition reaction, and nitrogen and tungsten remain on the surfaces of the source and drain layers 8 to form wedges to relieve stress. I do. In the case where cobalt or nickel is contained in these films, the cobalt or nickel undergoes a salicide reaction with silicon of the source / drain layer 8 and changes to a silicide film. (Other Embodiments) In the first and second embodiments, the silicon substrate 1 is used as the substrate, but a P-type silicon substrate or an N-type silicon substrate doped with impurities may be used. In this case, in the second embodiment, the stress relaxation layer may be determined based on the relationship between the silicide film and the silicon substrate doped with impurities.

[Brief description of the drawings]

FIG. 1 is a procedure diagram showing a manufacturing process of a MOS transistor according to a first embodiment.

FIG. 2 is a procedure diagram showing a manufacturing process of the MOS transistor, following FIG. 1;

FIG. 3 is a conceptual diagram of the vicinity of a cobalt silicide film 8a during a silicidation reaction.

FIG. 4 is a procedure diagram illustrating a manufacturing process of a MOS transistor according to a second embodiment.

FIG. 5 is a procedural diagram illustrating a manufacturing process of the MOS transistor, following FIG. 4;

FIG. 6 is a conceptual diagram near the cobalt silicide film 8a during a silicidation reaction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate, 2 ... P well layer, 4 ... Gate insulating film, 5 ... Gate electrode, 5a ... Cobalt silicide film, 6
... Electric field relaxation layer, 7 ... sidewall film, 8 ... source and drain layers,
8a ... Cobalt silicide film, 11 ... Titanium film, 12 ...
Cobalt film, 13: titanium nitride film, 21: titanium nitride film, 22: cobalt film.

Claims (6)

[Claims] 1. A step of forming a gate electrode (5) on a top surface of a substrate (1) via a gate insulating film (4); and forming source and drain layers (8) on both sides of the gate electrode (5). Forming a refractory metal film (12) on the upper surface of the source / drain layer (8); and forming a stress relaxation layer (1) on the upper surface of the refractory metal film (12).
3) forming a metal silicide film (8a) by performing a heat treatment to cause a silicidation reaction of the refractory metal film (12), thereby forming a metal silicide film (8a). Forming the silicidation reaction in the stress relaxation layer (13) while relaxing the stress generated at the interface between the source / drain layer (8) and the metal silicide film (8a). MIS transistor manufacturing method. 2. The stress relaxation layer (13) includes the source / drain layer (8) and the metal silicide film (8a).
2. The method according to claim 1, wherein a stress acting in a direction opposite to the stress generated at the interface of the MIS transistor is generated. 3. The method according to claim 1, wherein the stress relaxation layer is formed of a metal thin film or a metal nitride film. 4. A step of forming a gate electrode (5) on a top surface of a substrate (1) via a gate insulating film (4); and forming source and drain layers (8) on both sides of the gate electrode (5). Forming, on the upper surface of the source / drain layer (8), forming a stress relieving layer (21) made of a compound of a plurality of substances; and refractory metal on the upper surface of the stress relieving layer (21). Membrane (2
2) forming a metal silicide film (8a) by silicidation of the refractory metal film (22); and forming the metal silicide film (8a). By the heat treatment, the stress relaxation layer (21) is decomposed into the plurality of substances, and one of the plurality of substances is left at the interface between the source / drain layer (8) and the metal silicide film (8a). The silicidation reaction is performed while relaxing the stress generated at the interface.
A method for manufacturing an S transistor. 5. The stress relaxation layer (21) is formed of a metal nitride film that is a compound of metal and nitrogen, and in the step of forming the metal silicide film (8a), the metal nitride film is formed with the metal. The source and drain layers (8) are decomposed into nitrogen and the decomposed nitrogen causes the nitrogen to decompose.
5. The MI according to claim 4, wherein stress generated at an interface between the metal silicide film and the metal silicide film is relaxed.
A method for manufacturing an S-tonista 6. The stress relaxation layer (21) is formed of a metal compound film in which a first metal and a second metal are combined, and in the step of forming the metal silicide film (8a), The first metal and the second metal are decomposed and the decomposed first metal relaxes the stress generated at the interface between the source / drain layer (8) and the metal silicide film (8a). The method for manufacturing a MIS transistor according to claim 4, wherein: