JPH10112446A - Contact formation and semiconductor device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an ohmic contact of a low resistance and obtain a device which can be operated at a fast speed by forming a metallic layer on an untreated substrate containing a silicon material, forming metallic silicide by performing heat treatment and forming metallic nitride by a CVD method by using specified mixture gas thereon. SOLUTION: A layer insulation film 2 formed of SiO2 is formed on a semiconductor board 1 formed of silicon, etc., and a contact hole 3 is opened therein. Then, a Ti layer 4 is formed by an ECR plasma CVD device by using mixture gas containing TiCl4 . Thereafter, an untreated substrate is carried to a heat treatment chamber without being exposed to air and is subjected to heat treatment; then, the Ti layer 4 in a bottom part of the contact hole 3 in contact with the semiconductor board 1 formed of silicon is converted into a Ti silicide layer 5. Then, the untreated substrate is carried to an ECR plasma CVD device again and a TiN layer 6 is formed. In the process, the Ti silicide layer 5 is not nitrified any more and a contact of low resistance can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a contact used in a manufacturing process of a semiconductor device, and more particularly, to a method for forming a contact on a metal layer such as Ti formed on a silicon material or on a silicon material. The present invention relates to a contact formation method capable of obtaining a low-resistance ohmic contact when a metal nitride layer such as TiN is formed on a metal silicide layer such as Ti silicide, and a semiconductor device using the same.

[0002]

2. Description of the Related Art As the design rules of semiconductor devices such as LSIs have been reduced from half micron to quarter micron or less and multi-layer wiring structures have been frequently used, impurity diffusion layers and first layers of a semiconductor substrate have been developed. The aspect ratios of contact holes for connecting wiring and via holes connecting between wiring layers also tend to increase. For example, in a semiconductor device of the 0.18 μm rule, the thickness of the interlayer insulating film is 1.
Since it is about 0 μm, the aspect ratio reaches 5. In order to achieve a highly reliable multilayer wiring structure using such fine and high-aspect-ratio connection holes, a metal layer such as Ti for ohmic contact and the like such as TiN for preventing diffusion of wiring material are provided in the connection holes. After a thin and conformal metal nitride layer or the like is formed, a method of filling a connection hole with an upper wiring material or a contact plug by high-temperature sputtering of an Al-based metal or selective CVD or blanket CVD of W is being adopted. In this specification, a contact hole and a via hole are collectively called a connection hole.

[0003] Usually, to form a Ti layer or a TiN layer,
Sputtering using bulk Ti metal as a target material or reactive sputtering is performed. Above all, attention has been focused on, for example, collimated sputtering in which the perpendicular incidence component of sputtered particles is increased and long-distance sputtering in which the distance between the target and the substrate is increased, which is disclosed in, for example, JP-A-6-140359. According to these sputtering methods, since the sputtered particles reach the bottom of the connection hole having a large aspect ratio, it has been confirmed that the contact resistance is reduced and the barrier property is improved as compared with the conventional sputtering method. However, since these sputtering methods increase the vertical incidence component of the sputtered particles on the substrate to be processed, extremely thin portions are formed on the shoulders and side surfaces of fine connection holes having a large aspect ratio. Is inevitably formed. In this case, when blanket CVD of W is performed in the next step, WF _{6 as} a source gas enters from a thin portion of the barrier layer, and W
May abnormally grow, or the Ti layer or the TiN layer may peel off.

In order to address the problem of step coverage which is difficult to solve by these sputtering methods including the collimation method, etc., a conformal Ti layer or TiN by CVD using a chemical reaction on the surface of a substrate to be processed.
A method for forming a layer is expected.

[0005] Currently proposed CVD of Ti-based material layer
The method is roughly classified into a method using an inorganic metal halide such as TiCl ₄ reported in the 44th Symposium on Semiconductor / Integrated Circuit Technology, p. 31 (1993), Proc. 11th. Int. IEEE V
TD reported in MIC, p440 (1994), etc.
And a method using an organic titanium compound such as MAT or TDEAT.

[0006] Among the Ti-based material layers, in the CVD of the Ti layer, the thermal reduction reaction using the metal halides TiCl ₄ and H ₂ is an endothermic reaction given by the following equation (1) and is thermodynamic. This is a system in which the reaction hardly proceeds (ΔG represents the standard heat of formation). TiCl ₄ + 2H ₂ → Ti + 4HCl ΔG = 393.3 kJ / mol (1)

For this reason, H ₂ is dissociated in the plasma and H ₂
Plasma CVD using reduction reaction by atoms and H active species
Has attracted attention. This reaction is an exothermic reaction represented by the following formula (2). TiCl ₄ + 4H → Ti + 4HCl ΔG = −478.6 kJ / mol (2)

Accordingly, the formation of the Ti layer by plasma CVD allows the reaction to proceed easily and makes it possible to form the film at a relatively low temperature. In particular, ECR plasma CVD
Method, inductively coupled plasma CVD method and helicon wave plasma C
The plasma CVD method using a high-density plasma generation source such as the VD method is advantageous in that the dissociation of TiCl ₄ proceeds easily and the film formation rate and uniformity are high.

On the other hand, in the method of forming the TiN layer,
Plasma CVD and thermal CVD using metal halides such as Cl ₄ and organic Ti compounds have been studied. Among them, the method using TiCl ₄ includes a Ti layer by H ₂ reduction,
Further, a TiN layer formed by adding a nitriding agent such as N ₂ to this gas system and a TiN layer formed by a reducing nitriding agent such as NH ₃ or methylhydrazine are continuously formed in the same CVD apparatus. It has advantages that can be.

In an actual semiconductor device manufacturing process, after forming a Ti layer and a TiN layer on a silicon material,
A heat treatment such as A (Rapid Thermal Anneal) is used to apply thermal energy to perform a silicidation reaction.
This process will be described with reference to FIGS.
FIG. 8A is a schematic sectional view in which a Ti layer 4 and a TiN layer 6 are formed on a semiconductor substrate 1 such as silicon by a sputtering method. On the semiconductor substrate 1, a thin native oxide film 11 is formed. When a heat treatment for silicidation is performed in this state, as shown in FIG.
1 is reduced and silicified to be converted into a Ti silicide layer 5. On the other hand, the oxygen in the natural oxide film 11 is T
The TiO _x layer 12 is deposited on the surface of the i-silicide layer 5 to form a high-resistance TiO _x layer 12 at the interface with the TiN layer. In particular, in the film formation by the sputtering method, since the step coverage at the bottom of the connection hole is not so good, in the process of the silicidation heat treatment, oxygen in the air or residual oxygen in the heat treatment atmosphere is reduced as shown in FIG. The thinner part of the TiN layer 6 is transmitted to reach the interface between the TiN layer 6 and the Ti layer 4,
The formation of the iO _x layer 12 is promoted. Such a TiO _x layer 1
No. 2 is described in IEICE Technical Report SDM95-203 (1
995).

In any case, the Si (semiconductor substrate) / Ti silicide layer /
A contact structure composed of a TiO _x layer / TiN layer (uppermost layer) is formed in a layer order. Among them, the interface between the semiconductor substrate 1 and the Ti silicide layer 5 is clean and the Schottky barrier height between silicon and Ti silicide is low, so that a low-resistance contact is formed. However, since the high-resistance TiO _x layer 12 is formed between the Ti silicide layer 5 and the TiN layer 6, the resistance value of the entire contact structure cannot be reduced.

On the other hand, CVD having excellent step coverage
When the TiN layer is formed by the method, the promotion of the formation of the TiO _x layer due to the incorporation of oxygen in the air or the like is suppressed, but the formation of the TiO _x layer by the solid phase diffusion of oxygen from the natural oxide film still exists. In the TiN layer CVD process,
As shown in FIG. 9A, nitrogen active species (N ^* ) is used in plasma CVD, and NH ₃ is used in thermal CVD such as low pressure CVD.
And a gas having a high nitriding ability such as methyl hydrazine. For this reason, when the Ti layer 4 is not subjected to the silicidation reaction or formed insufficiently after the formation of the Ti layer 4, the underlying Ti
Layer 4 is nitrided to form TiN layer 10 by nitriding Ti. In this case, the thickness of the Ti layer 4 that can be silicided decreases or disappears, the natural oxide film 11 cannot be reduced, and the natural oxide film 11 remains on the semiconductor substrate 1. This situation is shown in FIG. Also in this case, the contact resistance cannot be reduced.

In order to form a low-resistance contact, the natural oxide film on the surface of the silicon material layer is reduced and removed by the Ti layer, and the silicidation of the Ti layer is sufficiently advanced. Ti formed on
It is essential to remove the O _x layer. The silicidation reaction can be promoted by sufficiently applying thermal energy by RTA or the like. However, TiO _x is a thermodynamically stable substance as compared with SiO _x, and it is difficult to remove TiO _x by ordinary wet etching or the like. The TiO _x layer can be removed by dry etching using a halogen-based gas such as chlorine.
It is difficult to obtain an etching selectivity with the i-silicide layer, and if excessive over-etching is performed, the underlying semiconductor substrate may be exposed.
There is a problem that l-type metal wiring is corroded by residual chlorine.

Usually, when a TiN layer is formed on a Ti layer by CVD using a metal halide such as TiCl ₄ and a nitriding agent, first, a nitride layer is formed on the surface of the Ti layer,
by l _4, TiCl _x based active species are degradation products of TiCl _4, or dissociated product from TiCl ₄ Cl ^* (chlorine radicals) or the like, it is performed to prevent the etching of the Ti layer. That is, T by plasma CVD
In forming the iN layer, the surface of the Ti layer is nitrided by N ^* (nitrogen radical) generated in the plasma. Also heat CV
In the formation of a TiN layer by D, when NH ₃ reduction is used, the surface of the Ti layer is nitrided by NH ₃ plasma treatment in advance. When using methylhydrazine reduction, methylhydrazine is reacted with the surface of the Ti layer to obtain a T
The surface of the i-layer is nitrided.

By the nitriding treatment, the etching of the Ti layer by TiCl ₄ or TiCl _x -based active species, which is a decomposition product of TiCl ₄ , or Cl ^* radicals is suppressed. However, the nitriding treatment of the surface of the Ti layer also has a problem of hindering a silicidation reaction of the Ti layer necessary for forming a low-resistance ohmic contact. This problem will be described with reference to FIG.

FIG. 10 shows that after a Ti layer (not shown) having a thickness of, for example, 20 nm is formed in contact with a semiconductor substrate 1 such as silicon, the surface thereof is nitrided, and then the TiN layer 6 is subjected to ECR.
It is a schematic sectional drawing of an example of the contact part formed by plasma CVD, for example, 30 nm. The nitridation reaction of Ti is T
It is a reaction system in which the reaction proceeds more thermodynamically than the silicidation reaction of i. Therefore, the nitrogen atoms easily diffuse in the Ti layer, and reach the semiconductor substrate 1 made of silicon, which is a base material layer. In a current situation where a bonding layer (not shown) of the semiconductor substrate 1 is extremely shallow as in a recent semiconductor device, it is common to form a thin Ti layer. For this reason, when the TiN layer 10 or the high-resistance Ti—Si—N compound layer 9 is formed by nitriding the Ti layer and the thickness of the Ti layer is reduced, the thinned Ti layer becomes a natural oxide film on the semiconductor substrate 1. (Not shown) can no longer be reduced uniformly, and the Ti silicide layer 5 is also formed non-uniformly. Reference numeral 8 denotes a Ti—O—N—S formed by taking in oxygen in a natural oxide film (not shown) on the surface of the semiconductor substrate 1.
This is an i-compound layer.

If the silicidation reaction does not proceed uniformly and the high-resistance Ti-Si-N compound layer 9 is formed, it is difficult to realize a low-resistance contact. Further, the Ti-ON-Si compound layer 8 formed at the interface between the semiconductor substrate 1 and the TiN layer 10 by nitriding Ti is also a high-resistance substance and forms a pseudo MOS structure. Ohmic contact cannot be realized.

Further, in a salicide process in which a silicide layer is formed in a self-aligned manner on the surface of a gate electrode such as a source or drain of a semiconductor substrate or polycrystalline silicon, the surface nitridation of the Ti layer causes an adverse effect. That is, Ti
Since the nitrogen atoms penetrating into the layer induce aggregation of the silicide, a uniform silicide layer cannot be formed. In addition, the presence of the nitrogen atom also hinders the crystal transition to the low-resistance C54 structure TiSi ₂ phase.

In a salicide technique in which a silicide layer is formed on the entire surface of the source and drain regions of a semiconductor substrate to reduce the resistance of a diffusion layer, an interlayer insulating film is formed after forming a silicide layer. A process of opening connection holes facing the source and drain regions is employed. Since the salicide technique involves processes such as formation of a metal layer such as Ti or Co, heat treatment, and wet etching, it is almost impossible to continuously apply a substrate to be processed in the same apparatus without exposing the substrate to the atmosphere. Therefore, an oxide layer is inevitably formed on the surface of the silicide layer when exposed to the air. Also during the silicidation heat treatment, the surface of the silicide layer is oxidized by the entrained oxygen in the heat treatment atmosphere.

For this reason, after forming a metal layer such as Ti or Co, a TiN cap layer for preventing oxidation is formed thereon. In the case of Ti, the Ti layer is partially nitrided at this time.
After the silicidation heat treatment, the TiN cap layer is removed with sulfuric acid and hydrogen peroxide. At this time, nitrogen in the portion where the Ti layer is nitrided escapes, and oxidation proceeds mainly in the portion from which the nitrogen has escaped, and the Ti silicide layer surface An oxide layer is formed. Thus, on the Ti silicide layer where the oxide layer exists on the surface,
Selective CVD through interlayer insulating film formation process and connection hole opening process
Even if a tungsten plug is formed, contact resistance increases due to the presence of an oxide layer at the interface between the Ti silicide layer and the tungsten plug. For example, the 56th Annual Meeting of the Japan Society of Applied Physics (1995 Autumn Meeting) Proceedings p700, Lecture No. 27a-PB-17.

Therefore, as a method of removing the oxide layer on the Ti silicide layer, a method of plasma etching with a gas containing Cl such as BCl ₃ or ClF ₃ is used, for example, Adv
anced Metallization and I
interconnect System for UL
SI Applications 1995, p467
Has been reported to. However, in this method, Cl remains on the surface of the Ti silicide layer, and there is a concern about corrosion of the upper Al-based metal wiring and the like. Also, an ICP (Inductively C) using a sputtering effect by Ar ions.
Soft etching using an "coupled Plasma" has been attempted. However, in this method, the removal of the oxide layer on the Ti silicide layer was insufficient.
For example, Extended Abstracts of
the1996 International Con
reference on Solid State De
visits and Materials, p139
Has been reported to.

[0022]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned problems of the prior art. That is, an object of the present invention is to provide a method for forming a metal layer such as Ti on a silicon material,
Alternatively, TiN is formed on the metal silicide on the silicon material layer.
A low-resistance contact forming method that does not leave a native oxide film on the surface of the underlying silicon material layer or form a new oxide layer on the metal silicide layer when forming a metal nitride layer such as It is to provide. Another object of the present invention is to provide a highly integrated semiconductor device having a low-resistance contact formed by such a contact forming method.

[0023]

SUMMARY OF THE INVENTION A contact forming method according to the present invention is proposed to solve the above-mentioned problems, and includes a step of forming a metal layer on a substrate to be processed containing a silicon material; Forming a metal silicide layer by reacting a silicon material with a metal layer by performing a heat treatment on the metal nitride layer layer using a mixed gas containing a metal halide compound and a nitriding agent on the metal silicide layer. Is formed by a CVD method. At this time, a step of forming a metal layer, a step of forming a metal silicide layer, and a step of forming a metal nitride layer by CVD.
It is desirable that the step of forming by a method be continuously performed without exposing the substrate to be processed to the atmosphere.

Another contact forming method of the present invention includes a step of forming a metal layer on a substrate to be processed containing a silicon material;
By subjecting this substrate to heat treatment, a silicon material and a metal layer react with each other to form a metal silicide layer, and a plasma treatment with a gas containing H ₂ is performed to form a metal silicide layer on the metal silicide layer. The method includes a step of removing an oxide layer and a step of forming a metal nitride layer on the metal silicide layer. The step of forming the metal nitride layer may be either a CVD method or a method of nitriding the surface of the metal silicide layer with nitrogen active species.

In another contact forming method of the present invention, a metal layer is formed on a substrate to be processed containing a silicon material, and the silicon substrate and the metal layer are reacted by performing a heat treatment on the substrate to be processed. forming a metal silicide layer, subjected to plasma treatment with a gas containing halogen-based chemical species, the step of removing the oxide layer that is inevitably formed on the metal silicide layer, plasma treatment with a gas containing H ₂ subjected, Removing a halogen-based chemical species remaining on the metal silicide layer; and forming a metal nitride layer on the metal silicide layer by a CVD method using a mixed gas containing a metal halide compound and a nitriding agent. It is characterized by the following. The step of forming the metal nitride layer may be either a CVD method or a method of nitriding the surface of the metal silicide layer with nitrogen active species. Is desirable. The silicon material targeted by the present invention is any one of single crystal silicon, polycrystalline silicon, and amorphous silicon.

A semiconductor device according to the present invention has a low-resistance contact formed by the above-described method.

Next, the operation will be described. One of the characteristic points of the present invention is that when a TiN layer is formed on a Ti layer by CVD, a Ti layer in contact with a silicon material as an underlayer reacts with the silicon material in advance and is converted into a Ti silicide layer. It is a point to put. Ti silicide, or TiSi ₂ ,
As is apparent from the following equations (3) and (4), the metal Ti
It is a substance that is less thermodynamically nitrided. Ti + N → TiN ΔG = −810.7 kJ / mol (3) TiSi ₂ + N → TiN + 2Si ΔG = −669.5 kJ / mol (4)

Therefore, when the TiN layer is formed by CVD, there is little possibility that the Ti silicide layer is further nitrided, and a low-resistance contact can be formed.
FIG. 7 is a schematic sectional view of a contact portion formed by the contact forming method of the present invention. Among them, FIG.
2A, a Ti layer (not shown) having a thickness of 20 nm is formed on a semiconductor substrate 1 made of silicon or the like, and is subjected to a silicidation heat treatment to convert the Ti layer into a Ti silicide layer 5.
It is a schematic sectional drawing of the contact part formed by R plasma CVD by 30 nm. As can be seen from the figure, the Ti silicide layer 5 is formed uniformly, and excessive nitriding of the Ti layer (not shown) is prevented. High resistance Ti-Si-N
No generation of a compound layer is observed. Oxygen in a natural oxide film (not shown) formed on the semiconductor substrate 1 is swept out to the interface between the Ti silicide layer 5 and the TiN layer 6, and an extremely thin Ti-ON-Si Compound layer 8 or TiO
_{An x} layer is formed. Unlike the layer formed on the surface of the semiconductor substrate 1, the Ti—O—N—Si compound layer 8 does not significantly hinder the low-resistance ohmic contact. This is because the Ti—O—N—Si compound layer 8 or the TiO _x layer is extremely thin,
Since it is a layer that exists between metal compound interfaces, MOS
It is considered that the tunnel current flows freely without forming the structure. FIG. 4B shows that a Ti layer (not shown) having a thickness of 20 nm is further formed on a semiconductor substrate 1 such as silicon and then subjected to a silicidation heat treatment to form a Ti silicide layer 5.
After the oxide film (not shown) such as a Ti-ON-Si compound layer or a TiO _x layer on the surface is reduced and removed by hydrogen plasma, the TiN layer 6 is formed to a thickness of 30 nm by ECR plasma CVD. It is an outline sectional view. The oxide film on the surface of the Ti silicide layer 5 may be removed by a mild plasma treatment that does not damage the underlying Ti silicide layer 5 by the halogen-based chemical species, and then the adsorbed halogen-based chemical species may be removed by H plasma. . Either method can form a low-resistance ohmic contact of the Si / Ti silicide layer / TiN layer.

Another feature of the present invention is that Ti
When a metal layer such as Ti or a metal nitride layer such as TiN is formed on a metal silicide layer such as silicide, an oxide layer inevitably formed on the metal silicide layer is removed. TiO ₂ , C formed on Ti silicide layer
Any reduction reaction of an oxide layer such as CoO formed on the silicide layer by hydrogen active species is an endothermic reaction and is a system that easily proceeds. By removing the oxide layer on the surface of the metal silicide layer exposed at the bottom of the connection hole, the resistance value between the metal silicide layer / metal layer or metal nitride layer is reduced. When the metal nitride layer is formed by nitriding the metal silicide layer, it can be formed in a self-aligned manner at the bottom of the connection hole. Furthermore, it is also possible to form a buried contact plug continuously on this metal nitride layer.

The semiconductor device formed by such a contact forming method can operate at high speed because the contact resistance value is reduced as compared with the conventional device. Especially 0.35μ
This effect is remarkable when applied to a highly integrated semiconductor device having a contact diameter of m or less.

[0031]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Examples 1 to 5 below are examples in which a contact mainly composed of a Ti silicide layer and a TiN layer is formed in a contact hole opened in an interlayer insulating film on a semiconductor substrate. TiCl as metal halide
₄ , a Ti layer and a TiN layer were formed by plasma CVD.

Embodiment 1 This embodiment employs a cluster tool in which an ECR plasma CVD chamber and a heat treatment chamber are integrated via a gate valve as a processing apparatus, and transports a substrate to be processed without exposing it to the atmosphere. This is an example in which a series of processes are performed to form a contact, which will be described with reference to FIGS. Naturally, a processing apparatus in which a heating means such as a halogen lamp is integrated in the plasma CVD chamber may be employed, and a series of processing may be performed in the same chamber.

First, on a semiconductor substrate 1 made of silicon or the like, SiO
₂ is formed, and a contact hole 3 is opened here. The thickness of the interlayer insulating film 2 is, for example, 1.0 μm, and the opening diameter of the contact hole 3 is 0.3 μm.
It is. Next, after removing a natural oxide film (not shown) on the surface of the diffusion layer of the semiconductor substrate 1 exposed at the bottom of the contact hole 3 with a diluted hydrofluoric acid aqueous solution, the substrate is placed on a substrate stage of an ECR plasma CVD apparatus, and H _2. / Ar or H ₂ / N
₂ / Ar plasma treatment is performed to clean the bottom of the contact hole 3. Next, using the same ECR plasma CVD apparatus, using a mixed gas containing TiCl ₄ , as an example, the Ti layer 4 is formed to a thickness of 20 nm under the following plasma CVD conditions.
Form. TiCl ₄ 3 sccm H ₂ 100 sccm Ar 170 sccm Gas pressure 0.75 Pa Microwave power 2.8 kW (2.45 GHz) Substrate temperature 380-460 ° C. The substrate to be processed after forming the Ti layer 4 is shown in FIG. Shown in

Thereafter, the substrate to be processed is transported to the heat treatment chamber connected to the ECR plasma CVD chamber without being exposed to the atmosphere, where the substrate is subjected to a heat treatment. The heat treatment conditions are, for example, in an Ar or H ₂ atmosphere, or in an Ar / H ₂ mixed gas atmosphere, at 600 ° C. to 800 ° C.
Temperature conditions. By this heat treatment, Ti at the bottom of contact hole 3 in contact with semiconductor substrate 1 made of silicon is formed.
The layer 4 is converted to a Ti silicide layer 5 as shown in FIG. Depending on the heat treatment conditions, the interlayer insulating film 2
, That is, the Ti layer 4 on the surface of the interlayer insulating film 2 and the side surface of the contact hole 3 hardly reacts, and remains as unreacted Ti metal. In this silicidation heat treatment, for example, after forming a Ti silicide having a C49 structure by a first heat treatment at 650 ° C. for 30 to 60 seconds, a second heat treatment at 800 ° C. for 30 sec is further applied to form a low-resistance C54 structure. The phase transition to the silicide layer proceeds extremely smoothly. Such heat treatment is performed by RTA (Rapid
It is desirable to use a Thermal Anneal device.

Next, the substrate to be processed is again subjected to ECR plasma C.
The substrate is transported to a VD apparatus, and a TiN layer is formed to a thickness of 30 nm under the following plasma CVD conditions as an example. Prior to formation of the TiN layer, a thin Ti layer may be formed on the Ti silicide layer 5. TiCl ₄ 20 sccm H ₂ 26 sccm N ₂ 8 sccm Ar 170 sccm Gas pressure 0.75 Pa Microwave power 2.8 kW (2.45 GHz) Substrate temperature 380 to 460 ° C. In the present plasma CVD process, N in the plasma is used. ^Although nitrogen active species such as ⁺ and N ^* also reach the bottom of the contact hole 3, the Ti silicide layer 5 is not further nitrided at this stage. However, the unreacted Ti layer 4 in contact with the interlayer insulating film 2 reacts with the nitrogen active species and is nitrided to be converted to TiN. As a result, the plasma C is mainly deposited on the Ti silicide layer 5 at the bottom of the contact hole 3.
The TiN layer 6 formed by VD has a TiN layer formed by nitriding the Ti layer 4 and a plasma C
A TiN layer 6 made of TiN formed by VD is formed. In the subsequent steps, the contact holes 3 are buried by sputtering of an Al-based metal or CVD of a high-melting metal such as W to form a contact plug or a wiring layer (not shown).

According to the present embodiment, since the Ti layer 4 at the bottom of the contact hole 3 has been converted into the Ti silicide layer 5 in advance, the Ti layer 4 is excessively nitrided and the high resistance Ti--S
There is no inconvenience of forming an iN compound or the like. If the natural oxide film on the surface of the semiconductor substrate 1 at the bottom of the contact hole 3 is not sufficiently removed, an extremely thin Ti—O—N—Si layer or TiO _X layer may be formed on the Ti silicide layer 5. However, this is not enough to impair ohmic contact. According to the present embodiment, it is possible to form a contact having a resistance value which is lower by about one digit than that of the related art.

Embodiment 2 In this embodiment, an ECR plasma CVD apparatus is used as a processing apparatus, and a Ti layer is formed, a silicidation reaction is performed, a TiO _x layer is removed by hydrogen active species, and a Ti layer is formed in the same processing apparatus. This is an example in which the film is continuously applied, which is shown in FIGS.
This will be described with reference to FIG. FIGS. 2A to 2F are schematic cross-sectional views showing the lower portion of the contact hole 3 in an enlarged manner. In this embodiment, it is assumed that the natural oxide film on the surface of the semiconductor substrate exposed at the bottom of the connection hole is not sufficiently removed. In this case, a low-resistance contact is to be formed.

First, on a semiconductor substrate 1 such as silicon
₂ is formed, and a contact hole 3 is opened here. The thickness of the interlayer insulating film 2 is, for example, 1.0 μm, and the opening diameter of the contact hole 3 is 0.2 μm.
It is. Next, after removing a natural oxide film (not shown) on the surface of the diffusion layer of the semiconductor substrate 1 exposed at the bottom of the contact hole 3 with a diluted hydrofluoric acid aqueous solution or the like, the substrate is mounted on a substrate stage of an ECR plasma CVD apparatus. A new natural oxide film 1 is formed on the surface of the semiconductor substrate 1 exposed at the bottom of the contact hole 3.
1 has already been formed. Next, using a mixed gas containing TiCl ₄ , for example, a Ti layer 4 of, eg, 20 nm is formed under the following plasma CVD conditions. TiCl ₄ 3 sccm H ₂ 100 sccm Ar 170 sccm Gas pressure 0.75 Pa Microwave power 2.8 kW (2.45 GHz) Substrate temperature 380-460 ° C. The substrate to be processed after forming the Ti layer 4 is shown in FIG. Shown in

Next, without exposing to the atmosphere a substrate to be processed in the same ECR plasma CVD chamber, H ₂ under the following conditions as an example the Ti layer 4 surface, as shown in FIG. 2 (b)
/ Ar plasma treatment using a mixed gas of 120 to 300
Apply for seconds. H ₂ 100 sccm Ar 50 sccm Gas pressure 0.75 Pa Microwave power 2.8 kW (2.45 GHz) Substrate temperature 380 to 460 ° C. In this plasma processing step, thermal energy due to plasma irradiation is added, and the surface of the substrate to be processed is added. Is 400-500 ° C
Heat up to. Therefore, a reduction reaction of the native oxide film 11 on the surface of the semiconductor substrate 1 exposed at the bottom of the contact hole 3 and
The silicidation reaction of the Ti layer 4 proceeds almost simultaneously,
At the same time as the silicide layer 5 is formed, oxygen in the natural oxide film 11 is precipitated on the surface, and the TiO _x layer 12 is formed. The state during this time is shown in FIGS.

Subsequently, when the plasma processing using the H ₂ / Ar mixed gas is continued, as shown in FIG.
Reduction of the iO _x layer 12 proceeds. The reduction reaction of TiO ₂ , which is the most thermodynamically stable among Ti oxides, with hydrogen active species is
This is an exothermic reaction represented by the following formula (5), and is a system that thermodynamically proceeds easily. TiO ₂ + 4H ^* → Ti + 2H ₂ O ΔG = −440 kJ / mol (5) The TiO _x layer 12
Is removed, and a clean Ti silicide layer 5 surface is formed. In the plasma treatment process using H _2, the emission spectrum of a hydrogen atom line as shown in FIG. 6, ie, Hα line (656.3 nm), Hβ line (486.1 nm), Hγ
Line (434.0 nm) and Hδ line (410.2 nm)
Are observed. Therefore, by monitoring the emission spectra of these hydrogen atom lines, it is understood that H ₂ is dissociated into hydrogen atoms and the TiO _x layer 12 is reduced under favorable plasma processing conditions.

Next, in the same ECR plasma CVD apparatus, for example, a TiN layer was formed under the following plasma CVD conditions.
It is formed to a thickness of 0 nm. Prior to the formation of the TiN layer, a thin second Ti layer may be newly formed. TiCl ₄ 20 sccm H ₂ 26 sccm N ₂ 8 sccm Ar 170 sccm Gas pressure 0.75 Pa Microwave power 2.8 kW (2.45 GHz) Substrate temperature 380-460 ° C. By this plasma CVD process, FIG. As shown in FIG. 5, the TiN layer 6 is formed with good step coverage. In the same figure, a Ti layer 4 remains on the side surface of the contact hole 3, but this is nitrided by a CVD process of a TiN layer,
It may be converted to the N layer and disappear. The subsequent steps are:
Sputtering of Al-based metal and C of refractory metal such as W
The contact hole 3 is buried by VD or the like, and a contact plug or a wiring layer (not shown) is formed.

According to this embodiment, the high resistance Ti-Si-
Without forming an N compound, a TiO _X layer or a Ti—O—N—Si layer, it is possible to form a contact having a resistance value that is at least one order of magnitude lower than in the prior art.

Embodiment 3 In this embodiment, it is assumed that an ECR plasma CVD chamber and a heat treatment chamber are separately provided as stand-alone apparatuses as processing apparatuses, and Ti silicide is transported between the apparatuses in the atmosphere. After reducing and removing the oxide layer formed on the layer surface by plasma containing H ₂ gas,
This is an example in which a TiN layer is formed. This contact forming method will be described with reference to FIGS.

First, on a semiconductor substrate 1 made of silicon or the like, SiO
₂ is formed, and a contact hole 3 is opened here. The thickness of the interlayer insulating film 2 is, for example, 1.0 μm, and the opening diameter of the contact hole 3 is 0.3 μm.
It is. Next, after removing a natural oxide film (not shown) on the surface of the diffusion layer of the semiconductor substrate 1 exposed at the bottom of the contact hole 3 with a diluted hydrofluoric acid aqueous solution, the substrate is placed on a substrate stage of an ECR plasma CVD apparatus, and H _2. / Ar or H ₂ / N
₂ / Ar plasma treatment is performed to clean the bottom of the contact hole 3. Next, using the same ECR plasma CVD apparatus, a mixed gas containing TiCl ₄ was used, and the Ti layer 4 was used as an example under the following plasma CVD conditions.
nm. TiCl ₄ 3 sccm H ₂ 100 sccm Ar 170 sccm Gas pressure 0.75 Pa Microwave power 2.8 kW (2.45 GHz) Substrate temperature 380-460 ° C. The substrate to be processed after the Ti layer 4 is formed is shown in FIG. Shown in

Thereafter, the substrate to be processed is carried out of the ECR plasma CVD apparatus, and carried into a heat treatment apparatus which is separately provided. Since the substrate to be processed is exposed to the air during the transfer process, the surface of the Ti layer 4 is oxidized. A heat treatment is applied to the substrate whose surface has been oxidized. The heat treatment condition is, for example, A
A temperature condition of 600 ° C. to 800 ° C. was set in an r or H ₂ atmosphere or an Ar / H ₂ mixed gas atmosphere. By this heat treatment, as shown in FIG. 3 (b), T at the bottom of the contact hole 3 in contact with the semiconductor substrate 1 made of silicon
i layer 4 is converted to Ti silicide layer 5. Also Ti
An oxide layer 7 made of Ti—Si—O or TiO _x is inevitably formed on the surface of the silicide layer 5 due to the surface oxidation of the Ti layer 4. On the other hand, depending on the heat treatment conditions, the Ti layer 4 in contact with the interlayer insulating film 2 hardly reacts, and remains unreacted Ti metal.

Next, the substrate to be processed is again subjected to ECR plasma C.
It is transported to a VD device and subjected to a plasma treatment with a mixed gas containing H ₂ and Ar under the following conditions, for example. H ₂ 100 sccm Ar 20 to 170 sccm Gas pressure 0.75 Pa Microwave power 2.8 kW (2.45 GHz) Substrate temperature Room temperature In this plasma processing step shown in FIG. The oxide layer 7 on the Ti silicide layer 5 is hydrogen-reduced by (H ^* ) according to the following equation (6). TiSiO + H ^* → TiSi + H ₂ O (6)

Thereafter, T is deposited on the clean Ti silicide layer 5 and Ti layer 4 under the following plasma CVD conditions as an example.
An iN layer is formed to a thickness of 30 nm. Prior to the formation of the TiN layer, a thin second Ti layer may be newly formed. TiCl ₄ 20 sccm H ₂ 26 sccm N ₂ 8 sccm Ar 170 sccm Gas pressure 0.75 Pa Microwave power 2.8 kW (2.45 GHz) Substrate temperature 380 to 460 ° C. In the present plasma CVD process, N in the plasma is used. ^Although nitrogen active species such as ⁺ and N ^* also reach the bottom of the contact hole 3, the Ti silicide layer 5 is not further nitrided at this stage. However, the unreacted Ti layer 4 in contact with the interlayer insulating film 2 reacts with the nitrogen active species and is nitrided to be converted to TiN. As a result, as shown in FIG. 3D, a TiN layer 6 formed by plasma CVD is formed on the Ti silicide layer 5 at the bottom of the contact hole 3.
However, a TiN layer 6 made of TiN formed by nitriding the Ti layer 4 and TiN formed by plasma CVD is formed at a portion in contact with the interlayer insulating film 2.

According to this embodiment, the Ti layer 4 at the bottom of the contact hole 3 is converted into the Ti silicide layer 5 in advance, and the oxide layer on the Ti silicide layer 5 is also removed. Ni-nitride and high-resistance Ti-Si-
It is possible to form a contact having a resistance value which is about one digit lower than that of the related art without forming an N compound or the like.

Embodiment 4 This embodiment is based on the previous embodiment 3. In this embodiment, it is particularly assumed that the natural oxide film on the surface of the semiconductor substrate exposed at the bottom of the connection hole is insufficiently removed. In this case, a low-resistance contact is to be formed. This process will be described with reference to FIGS. FIG. 4 is a schematic sectional view showing an enlarged bottom portion of the contact hole.

First, an SiO.sub.2 is deposited on a semiconductor substrate 1 such as silicon.
₂ is formed, and a contact hole 3 is opened here. The thickness of the interlayer insulating film 2 is, for example, 1.0 μm, and the opening diameter of the contact hole 3 is 0.2 μm.
It is. Next, a natural oxide film (not shown) on the surface of the diffusion layer of the semiconductor substrate 1 exposed at the bottom of the contact hole 3 is removed with a diluted hydrofluoric acid aqueous solution or the like, and the bottom of the contact hole 3 is cleaned. Place on the substrate stage. On the surface of the semiconductor substrate 1 exposed at the bottom of the contact hole 3, a new natural oxide film 11 has already been formed. Next, TCR was performed using an ECR plasma CVD apparatus.
Using a mixed gas containing iCl ₄ , a Ti layer 4 is formed to a thickness of 20 nm as an example under the following plasma CVD conditions. TiCl ₄ 3 sccm H ₂ 100 sccm Ar 170 sccm Gas pressure 0.75 Pa Microwave power 2.8 kW (2.45 GHz) Substrate temperature 380 to 460 ° C. The substrate to be processed after forming the Ti layer 4 is shown in FIG. Shown in

Thereafter, the substrate to be processed is carried out of the ECR plasma CVD apparatus, and is carried in to a separately provided heat treatment apparatus. Since the substrate to be processed is exposed to the air during the transfer process, the surface of the Ti layer 4 is oxidized. A heat treatment is applied to the substrate whose surface has been oxidized. The heat treatment condition is, for example, A
A temperature condition of 700 ° C. to 800 ° C. was set in an r or H ₂ atmosphere or an Ar / H ₂ mixed gas atmosphere. Due to this heat treatment, the natural oxide film 11 is reduced and deposited on the surface of the Ti layer 4, and the TiO _x layer 12 is formed here due to the influence of the surface oxide film (not shown) due to exposure to the atmosphere. At the same time, the silicidation reaction of the Ti layer 4 also proceeds, and the Ti silicide layer 5 is formed. Fig. 4 shows this series of reactions.
(B) to (c). On the other hand, depending on the heat treatment conditions, the Ti layer 4 in contact with the interlayer insulating film 2 hardly reacts, and remains unreacted Ti metal.

Next, the substrate to be processed is again subjected to ECR plasma C.
It is transported to a VD apparatus and subjected to a plasma treatment with a mixed gas containing H ₂ and Ar under the following conditions, for example, under the following conditions:
Apply for 00 seconds. H ₂ 100 sccm Ar 20 to 170 sccm Gas pressure 0.75 Pa Microwave power 2.8 kW (2.45 GHz) Substrate temperature Room temperature In this plasma processing step, as shown in FIG. The TiO _x layer 12 on the Ti silicide layer 5 is hydrogen-reduced by the following formula (7) by the active hydrogen species therein, and a clean Ti silicide layer 5 surface is formed.
TiO ₂ + 4H ^* → Ti + 2H ₂ OΔG = −44
0 kJ / mol (7)

Thereafter, T is deposited on clean Ti silicide layer 5 and Ti layer 4 under the following plasma CVD conditions, for example.
An iN layer is formed to a thickness of 20 nm. Prior to the formation of the TiN layer, the second Ti layer may be formed thin. TiCl ₄ 20 sccm H ₂ 26 sccm N ₂ 8 sccm Ar 170 sccm Gas pressure 0.75 Pa Microwave power 2.8 kW (2.45 GHz) Substrate temperature 380 to 460 ° C. In the present plasma CVD process, N in the plasma is used. ^Although nitrogen active species such as ⁺ and N ^* also reach the bottom of the contact hole 3, the Ti silicide layer 5 is not further nitrided at this stage. However, the unreacted Ti layer 4 in contact with the interlayer insulating film 2 reacts with the nitrogen active species and is nitrided to be converted to TiN. As a result, a TiN layer 6 formed by plasma CVD is formed on the Ti silicide layer 5 at the bottom of the contact hole 3 as shown in FIG. Ti
T consisting of N and TiN formed by plasma CVD
An iN layer 6 is formed.

According to the present embodiment, the Ti layer 4 at the bottom of the contact hole 3 is converted into the Ti silicide layer 5 in advance, and the oxide layer on the Ti silicide layer 5 is also removed. A contact having an order of magnitude lower resistance can be formed.

Embodiment 5 This embodiment is similar to the previous embodiment 3 in that the processing apparatus is an EC.
Assuming that the R plasma CVD chamber and the heat treatment chamber exist individually as stand-alone devices,
After removing the oxide layer formed on the surface of the Ti silicide layer by transporting between the individual devices into the atmosphere with a gas containing a halogen-based chemical species, performing a plasma treatment including an H ₂ gas, and then forming a TiN layer This is an example. This contact formation method will be described with reference to FIGS.

In this embodiment, the steps of performing the heat treatment for silicidation, that is, the steps shown in FIG. 5A are the same as those described in the previous embodiment 3 with reference to FIGS. The same is true, and duplicate description will be omitted. T
An oxide layer 7 made of Ti—Si—O is inevitably formed on the surface of the i-silicide layer 5 due to the surface oxidation of the Ti layer 4.

Next, the substrate to be processed shown in FIG. 5A is transported again to the ECR plasma CVD apparatus, and subjected to a plasma treatment with a gas containing Cl ₂ gas under the following conditions, for example. Cl ₂ 5 sccm Ar 170 sccm Gas pressure 0.75 Pa Microwave power 2.8 kW (2.45 GHz) Substrate temperature Room temperature This plasma processing step is shown in FIG. In this step, the oxide layer 7 on the Ti silicide layer 5 is expressed by the following equation (8).
Are reactively etched and removed by chlorine species (Cl ^* ). TiSiO + 8Cl ^* → TiCl ₄ + SiCl ₄ +1/2 O ₂ (8)

Next, a plasma treatment is performed in the same ECR plasma CVD apparatus with a mixed gas containing H ₂ and Ar under the following conditions as an example. H ₂ 100 sccm Ar 20 to 170 sccm Gas pressure 0.75 Pa Microwave power 2.8 kW (2.45 GHz) Substrate temperature Room temperature In this plasma processing step, as shown in FIG.
Halogen-based species adhering to the Ti silicide layer 5 due to active hydrogen species in the plasma, in this case Cl ^* or TiC
Remove _lx etc.

Thereafter, a second Ti layer (not shown) is formed on the clean Ti silicide layer 5 and the Ti layer 4 by, for example, 10
It is formed to a thickness of nm by ECR plasma CVD.
Subsequently, in the same ECR plasma CVD chamber, a TiN layer is formed to a thickness of 30 nm under the following plasma CVD conditions as an example. TiCl ₄ 20 sccm H ₂ 26 sccm N ₂ 8 sccm Ar 170 sccm Gas pressure 0.75 Pa Microwave power 2.8 kW (2.45 GHz) Substrate temperature 380 to 460 ° C. In the present plasma CVD process, N in the plasma is used. ^Although nitrogen active species such as ⁺ and N ^* also reach the bottom of the contact hole 3, the Ti silicide layer 5 is not further nitrided at this stage. However, the unreacted Ti layer 4 in contact with the interlayer insulating film 2 reacts with the nitrogen active species and is nitrided to be converted to TiN. As a result, as shown in FIG. 5D, a TiN layer 6 formed by plasma CVD is formed on the Ti silicide layer 5 at the bottom of the contact hole 3 and a Ti layer 4 is formed by nitriding the portion in contact with the interlayer insulating film 2. Ti
T consisting of N and TiN formed by plasma CVD
An iN layer 6 is formed.

According to this embodiment, the Ti layer 4 at the bottom of the contact hole 3 is converted into the Ti silicide layer 5 in advance, and the oxide layer on the Ti silicide layer 5 is completely removed. Excessively nitrided and high resistance Ti-S
It is possible to form a contact having a resistance value that is lower by about one digit or more than before without forming an iN compound or the like.

In the first to fifth embodiments described above, only the impurity diffusion layer of the semiconductor substrate exposed at the bottom of the contact hole has T
In this example, an i-silicide layer was formed, and then a TiN layer was formed. In the following Examples 6 to 8, a Ti silicide layer is formed by a salicide process over the entire surface of an impurity diffusion layer of a semiconductor substrate, and a TiN layer is formed through a subsequent interlayer insulating film forming step and a connection hole opening step. It is an example to which the present invention is applied.

Embodiment 6 In this embodiment, an ECR plasma CVD apparatus is used, and a tungsten layer is formed by blanket CVD from a step of removing an oxide layer on a metal silicide layer to a step of forming a metal nitride layer. 8 is an example in which the substrate to be processed is continuously applied without exposing the substrate to the atmosphere.
This will be described with reference to (a) to (c) and FIGS. 9 (d) to (f).

A semiconductor substrate 1 having a Ti silicide layer 5 formed on the surface of a diffusion layer (not shown) in a self-aligned manner is prepared. This semiconductor substrate 1 may be formed by a normal salicide process. Next, after forming an interlayer insulating film 2 made of SiO ₂ to a thickness of, for example, 1.5 μm over the entire surface of the semiconductor substrate 1, a contact hole 3 facing the diffusion layer in which the Ti silicide layer 5 is formed is formed by RIE or the like. . The opening diameter of the contact hole 3 is, for example, 0.2 μm. On the surface of the Ti silicide layer 5 exposed in the contact hole 3 bottom oxide layer 7 of TiO _x, as shown in FIG. 8 (a)
Thus, even if a contact plug is formed in this state, a low-resistance electrical connection cannot be obtained.

The substrate to be processed shown in FIG. 8A is set on a substrate stage of an ECR plasma CVD apparatus, and as an example, the oxide layer 7 is removed using a gas containing H ₂ under the following conditions. H ₂ 100 to 300 sccm Ar 0 to 100 sccm Gas pressure 0.75 Pa Microwave power 2.8 kW (2.45 GHz) Substrate temperature Room temperature to 460 ° C. In this hydrogen plasma processing step, as shown in FIG. The oxide layer 7 is easily reduced, and as shown in FIG.
The surface of the i-silicide layer 5 is cleaned.

Next, in the same ECR plasma CVD apparatus, the following plasma C using a mixed gas containing TiCl ₄ was used.
The Ti layer 4 is continuously formed, for example, by 15 nm under the VD condition. FIG. 9D shows a state after the Ti layer 4 is formed. TiCl ₄ 3 sccm H ₂ 200 sccm Ar 170 sccm Gas pressure 0.75 Pa Microwave power 2.8 kW (2.45 GHz) Substrate temperature 380-460 ° C. The step of forming the Ti layer 4 may be omitted.

Subsequently, in the same ECR plasma CVD apparatus, the following plasma C using a mixed gas containing TiCl ₄ was used.
Under the VD condition, the TiN layer 6 is continuously formed, for example, by 15 nm. FIG. 9E shows the state after the formation of the TiN layer 6. TiN layer forming conditions _{TiCl 4 20 sccm H 2 26 sccm} N 2 8 sccm Ar 170 sccm Gas pressure 0.75 Pa Microwave power 2.8 kW (2.45 GHz) substrate temperature three hundred and eighty to four hundred sixty ° C.

Thereafter, the substrate to be processed is transferred to a tungsten CVD apparatus via a gate valve without exposing the substrate to the atmosphere, and as shown in FIG.
The W layer 13 is formed by the VD method, and the W layer 13 and the TiN layer 6 are formed.
Then, the Ti layer 4 is etched back to form a contact plug. Alternatively, the W layer 13, the TiN layer 6, and the Ti layer 4 may be patterned into the shape of the upper wiring. According to the present embodiment, the oxide layer on the Ti silicide layer 5 is removed, and thereafter, the Ti layer, the TiN layer, and the W layer are continuously formed without exposing the substrate to be processed to the atmosphere. Resistive contacts can be formed.

Embodiment 7 In the present embodiment, after the step of removing the oxide layer on the metal silicide layer, the step of forming the metal nitride layer is selectively performed by nitriding the metal silicide layer, and then the aluminum is formed by selective CVD. This is an example in which the process until the plug is embedded is continuously performed without exposing the substrate to be processed to the atmosphere. This will be described with reference to FIGS.

FIG. 10A shows a semiconductor plate 1 in which a Ti silicide layer 5 is formed in a self-aligned manner on the surface of a diffusion layer (not shown).
An interlayer insulating film 2 is formed thereon, and the substrate to be processed having the contact holes 3 opened is subjected to hydrogen plasma treatment by an ECR plasma CVD apparatus to reduce and remove an oxide layer (not shown) on the surface of the Ti silicide layer 5 for cleaning. It is a schematic sectional drawing of what was done. The steps up to this point are the same as those in the previous embodiment 7 shown in FIG.
It can be applied according to the steps described with reference to (a) to (c).

Next, the wafer is transported to the parallel plate type plasma processing apparatus in the same ECR plasma CVD apparatus or through a gate valve, and is subjected to plasma processing using a mixed gas containing N ₂ and Ar. Here, an example of processing conditions by the parallel plate type plasma processing apparatus is shown below. N ₂ 100 to 2000 sccm Ar 0 to 300 sccm Gas pressure 7.5 Pa RF power 0.1 to 1 kW (0.45 to 60 MHz) Substrate temperature Room temperature to 460 ° C. In the plasma, N ₂ ⁺ 10B, the TiN layer 6 is formed in a self-aligned manner by the nitriding reaction of the cleaned Ti silicide layer 5 as shown in FIG.

The substrate to be processed shown in FIG. 10B is transported to an aluminum CVD apparatus without being exposed to the atmosphere.
Selective CVD of aluminum is performed using an organic metal compound DMAH or TIBA. The gas pressure is 0.0
1 to 1 Torr, of which the partial pressure of DMAH may be 0.01 to 0.1 Torr. Substrate temperature is 2
00 to 300 ° C. As a result, a contact plug made of the Al layer 14 was buried in the contact hole 3 as shown in FIG. Since the TiN layer 6 is formed on the surface of the Ti silicide layer 5, a good low-resistance ohmic contact can be formed without causing junction leakage due to Al spikes or the like.

Embodiment 8 In this embodiment, the steps from the step of removing the oxide layer on the metal silicide layer to the step of embedding a tungsten plug by selective CVD are continuously performed without exposing the substrate to be processed to the atmosphere. This is an example, which will be described with reference to FIGS.

FIG. 11 (a) shows the results of the sixth embodiment shown in FIG.
The interlayer insulating film 2 is formed on the semiconductor plate 1 in which the Ti silicide layer 5 is formed in a self-aligned manner on the surface of a diffusion layer (not shown) according to the process described with reference to FIG. FIG. 3 is a schematic cross-sectional view showing a state in which a processing substrate is being subjected to hydrogen plasma processing by a parallel plate type plasma processing apparatus here. An example of the plasma processing conditions is shown below. H ₂ 100 to 2000 sccm Ar 0 to 300 sccm Gas pressure 7.5 Pa RF power 0.1 to 1 kW (0.45 to 60 MHz) Substrate temperature Room temperature to 460 ° C. In this hydrogen plasma processing step, the oxide layer 7 is easily formed. It is reduced and the surface of the Ti silicide layer 5 is cleaned. After this,
The TiN layer may be formed by performing a nitrogen plasma treatment in the same manner as in the previous embodiment, but in this embodiment, the process proceeds to the next step.

Next, the substrate to be processed is transported in the same chamber or in a tungsten CVD apparatus without exposing the substrate to the atmosphere.
A contact plug made of the W layer 13 is embedded therein. This state is shown in FIG. SiH ₄ / WF ₆ flow rate ratio 1 or less Gas pressure 0.01-1 Torr Substrate temperature 200-400 ° C.

According to this embodiment, since the oxide layer on the surface of the Ti silicide layer 5 has been removed, clean W / TiSi
_Two interfaces can be formed, and a low-resistance contact can be formed.

As described above, the contact forming method of the present invention has been described in detail with reference to eight examples. However, the present invention is not limited to these examples, and various embodiments are possible. For example, a plasma CVD apparatus in the case of forming by plasma CVD method a Ti layer and a TiN layer, H ₂ plasma processing apparatus or a plasma processing apparatus using a halogen-based chemical species, in the embodiment ECR plasma CVD apparatus or a parallel plate type plasma processing apparatus Was adopted, but inductively coupled plasma CVD equipment or helicon wave plasma C
A VD device or the like may be used arbitrarily. Further, the Ti layer which is the lower layer of the TiN layer may be formed by sputtering or the like.
Further, the present invention can be suitably implemented even when the TiN layer is formed by a low pressure CVD method. An example of the reduced pressure CVD method for the TiN layer is shown below. TiCl ₄ 40 sccm NH ₃ 60 sccm N ₂ 3000 sccm Gas pressure 10 to 3000 Pa Substrate temperature 630 ° C.

TiCl _{4 is} used as a titanium halide compound.
However, other halogen compounds such as TiBr ₄ can be used. It is also clear that the technical idea of the present invention can be extended to the formation of metal films and metal nitride films by plasma CVD of various metal halides, not limited to titanium halides.

As the metal silicide material and the metal nitride material, Ti silicide and TiN have been mainly described.
It is possible to use silicide or nitride of various metals such as Co.

As a substrate to be processed on which a TiN layer is formed, a silicon substrate having a connection hole facing an impurity diffusion layer and a silicon substrate having a silicide layer formed by a salicide method have been exemplified. A semiconductor substrate having a via hole facing a wiring layer or the like made of silicon or an object to be processed containing another silicon material may be appropriately used.

[0080]

As is apparent from the above description, according to the contact formation method of the present invention, when forming a TiN layer on a Ti layer on a silicon material layer as a base by a CVD method, When the TiN layer is formed on the silicide layer, a low-resistance contact can be formed without leaving a natural oxide film on the underlying silicon material layer. When the TiN layer is formed by the CVD method, excessive nitriding and etching of the underlying Ti layer can be effectively prevented. For this reason, when adopted for a contact plug, a highly reliable, low-resistance ohmic contact can be formed. Therefore, by using the contact formation method of the present invention, it is possible to provide a high-integration semiconductor device having a low-resistance ohmic contact and capable of operating at high speed.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a contact forming method of Example 1 in the order of steps.

FIG. 2 is a schematic cross-sectional view showing a contact forming method of Example 2 in the order of steps.

FIG. 3 is a schematic cross-sectional view showing a contact formation method of Example 3 in the order of steps.

FIG. 4 is a schematic cross-sectional view showing a contact forming method of Example 4 in the order of steps.

FIG. 5 is a schematic cross-sectional view showing a contact forming method of Example 5 in the order of steps.

FIG. 6 is an emission spectrum diagram of a hydrogen atom beam.

FIG. 7 is a schematic sectional view of a contact portion according to the contact forming method of the present invention.

FIG. 8 is a schematic cross-sectional view showing the first half of a contact formation method according to a sixth embodiment in the order of steps.

FIG. 9 is a schematic cross-sectional view showing the latter half of the contact forming method of Example 6 in the order of the steps.

FIG. 10 is a schematic cross-sectional view showing a contact formation method of Example 7 in the order of steps.

FIG. 11 is a schematic cross-sectional view showing a contact formation method of Example 8 in the order of steps.

FIG. 12 is a schematic sectional view of a contact portion according to a conventional contact forming method.

FIG. 13 is a schematic sectional view of a contact portion according to another conventional contact forming method.

FIG. 14 is a schematic sectional view of a contact portion according to still another conventional contact forming method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Interlayer insulating film, 3 ... Contact hole, 4 ... Ti layer, 5 ... Ti silicide layer, 6 ... TiN
Layer, 7: oxide layer, 8: Ti-ON-Si compound layer, 9
... Ti-Si-N compound layer, 10 ... T by nitriding Ti
iN layer, 11 ... natural oxide film, 12 ... TiO _x layer, 13 ...
W layer, 14 ... Al layer

Claims (21)

[Claims] A step of forming a metal layer on a substrate to be processed containing a silicon material; a step of forming a metal silicide layer by reacting the silicon material with the metal layer by performing a heat treatment on the substrate to be processed. Forming a metal nitride layer on the metal silicide layer by using a mixed gas containing a metal halide compound and a nitriding agent;
A contact forming method. 2. The method according to claim 1, wherein the step of forming the metal layer and the step of forming the metal nitride layer by a CVD method are both performed by a plasma CVD method. 3. The step of forming the metal layer, the step of forming the metal silicide layer, and the step of forming the metal nitride layer by a CVD method without exposing the substrate to be processed to the atmosphere. 2. The method according to claim 1, wherein the method is performed. 4. After the step of forming the metal silicide layer, a second metal layer is formed on the metal silicide layer,
2. The method according to claim 1, wherein the metal nitride layer is formed on the second metal layer. 5. A step of forming a metal layer on a substrate to be processed containing a silicon material; a step of forming a metal silicide layer by reacting the silicon material with the metal layer by performing a heat treatment on the substrate to be processed. Performing a plasma treatment with a gas containing H ₂ to remove an oxide layer inevitably formed on the metal silicide layer; and forming a metal nitride layer on the metal silicide layer. A method for forming a contact, comprising: 6. The contact forming method according to claim 5, wherein the step of forming the metal nitride layer is performed by a CVD method using a mixed gas containing a metal halide compound and a nitriding agent. 7. The contact forming method according to claim 5, wherein the step of forming the metal layer and the step of forming the metal nitride layer by a CVD method are both performed by a plasma CVD method. 8. The step of forming the metal layer, the step of forming the metal silicide layer, the step of removing the oxide layer, and the step of forming the metal nitride layer include exposing the substrate to be processed to the atmosphere. The method according to claim 6, wherein the method is performed continuously without performing the method. 9. The contact forming method according to claim 5, wherein the step of forming the metal nitride layer is performed by nitriding the surface of the metal silicide layer with a nitrogen active species. 10. The plasma processing step using a gas containing H ₂ and the step of forming the metal nitride layer are performed continuously without exposing the substrate to be processed to the atmosphere. 10. The contact forming method according to 9. 11. After the step of removing the oxide layer, a second metal layer is formed on the metal silicide layer, and the metal nitride layer is formed on the second metal layer. The method for forming a contact according to claim 5, wherein 12. A step of forming a metal layer on a substrate to be processed containing a silicon material, a step of forming a metal silicide layer by reacting the silicon material with the metal layer by performing a heat treatment on the substrate to be processed. Performing a plasma treatment with a gas containing a halogen-based species to remove an oxide layer unavoidably formed on the metal silicide layer; performing a plasma treatment with a gas containing H ₂ on the metal silicide layer; A method for forming a contact, comprising: a step of removing residual halogen-based species; and a step of forming a metal nitride layer on the metal silicide layer. 13. The contact forming method according to claim 12, wherein the step of forming the metal nitride layer is performed by a CVD method using a mixed gas containing a metal halide compound and a nitriding agent. 14. The contact forming method according to claim 13, wherein both the step of forming the metal layer and the step of forming the metal nitride layer by a CVD method are performed by a plasma CVD method. 15. A step of forming the metal layer, a step of forming the metal silicide layer, a plasma processing step using a gas containing the halogen-based species, a plasma processing step using a gas containing the H ₂ , and the metal nitriding. 15. The contact forming method according to claim 13, wherein the step of forming the object layer is performed continuously without exposing the substrate to be processed to the atmosphere. 16. The method according to claim 12, wherein the step of forming the metal nitride layer is performed by nitriding the surface of the metal silicide layer with a nitrogen active species. 17. The step of removing the oxide layer, the step of removing the halogen-based species, and the step of forming the metal nitride layer are performed continuously without exposing the substrate to be processed to the atmosphere. 17. The method according to claim 16, wherein: 18. The method according to claim 18, wherein after the step of removing the oxide layer, a second metal layer is formed on the metal silicide layer, and the metal nitride layer is formed on the second metal layer. 13. The method of forming a contact according to claim 12, wherein: 19. The contact forming method according to claim 1, wherein the silicon material is any one of single-crystal silicon, polycrystalline silicon, and amorphous silicon. . 20. A semiconductor device having a contact formed by the method of forming a contact according to claim 1. 21. The semiconductor device according to claim 20, wherein said contact diameter is 0.35 μm or less.