JPH1045416A - Formation of cobalt silicide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a low-resistance cobalt silicide film which does not induce a fine line effect. SOLUTION: A cobalt film 6 is formed on semiconductor layers 3, 4 contg. silicon and is subjected to a first heat treatment by lamp annealing, by which the cobalt silicide film 7 is formed. The unreacted cobalt film 6 is removed. The cobalt silicide film 7 is subjected to a heat treatment by lamp annealing, by which the cobalt silicide film 8 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a cobalt silicide film formed on a silicon layer.

[0002]

2. Description of the Related Art In recent years, there has been a demand for low resistance and high speed of a semiconductor device.
The LICIDE (Self-Aligned Silicide) method has attracted attention.

[0003] As a silicide material used in the salicide method, titanium silicide is desired from the viewpoint of compatibility with the current manufacturing process.
This is a problem because a phenomenon in which the sheet resistance increases as the line width decreases, that is, a so-called thin line effect occurs.

Here, after a titanium film is formed on the source / drain diffusion layer while changing the film thickness to 20 nm, 30 nm, and 50 nm, RTA (Rapid Thermal Annealing), so-called lamp annealing (for example, infrared light (wavelength) of a halogen lamp) is used. FIG. 7 shows the relationship between the width W of the diffusion layer and the sheet resistance Rs when TiSi ₂ is formed as titanium silicide by annealing (irradiation of 0.4 to 4.0 μm). FIG. 7A shows the case where the source / drain diffusion layers are n ⁺ ,
FIG. 7B shows a case where the source / drain diffusion layers are p ⁺ . In the drawing, the circles indicate the measured values of the sheet resistance Rs of only the silicon diffusion layer as a control sample. 7A and 7B that the sheet resistance Rs increases as the width W of the diffusion layer decreases.

On the other hand, C which is a kind of cobalt silicide
Since oSi ₂ does not cause an increase in sheet resistance due to the above-described thin wire effect, attention has been paid to it and active development is being studied. Cobalt silicide includes Co ₂ Si, CoSi,
There are three phases of CoSi _2, each of the specific resistance to 70
μΩcm, 100-150μΩcm, 14-17μΩc
m. Therefore, when forming cobalt silicide in a semiconductor device, CoSi, which is the phase having the lowest resistance, is used.
It is necessary to form ₂ . Here, Co ₂ Si,
The temperatures at which CoSi and CoSi ₂ are formed are respectively ~
400 ° C., 450-550 ° C.,> 700 ° C.

[0006]

However, Co is deposited on fine wiring to form CoSi ₂ 700.
Even if the silicidation is performed at a temperature of ° C. or higher, the sheet resistance does not increase due to the thin wire effect, but a high-resistance cobalt silicide having a high absolute value of the sheet resistance is formed.

FIG. 8 shows that 10
After forming a cobalt film having a thickness of 700 nm, the heat treatment temperature for silicidation by the RTA method is set to 700 ° C., 800 ° C., 90 ° C.
The relationship between the line width W of the diffusion layer and the sheet resistance Rs when cobalt silicide is formed by changing the temperature to 0 ° C. is shown. FIG.
A shows the case where the source / drain diffusion layers are n ⁺ , and FIG. 8B shows the case where the source / drain diffusion layers are p ⁺ .

8A and 8B, no increase in the sheet resistance Rs due to the reduction in the line width W is observed, but the sheet resistance Rs is increased.
It can be seen that the absolute value of s is as high as about 100Ω / □.

When a manufacturing process by the salicide method is applied to a semiconductor device, it is desired that the sheet resistance be 10 Ω / □ and that the sheet resistance be independent of the line width. It is necessary to avoid the formation of cobalt silicide.

In order to solve the above-mentioned problem, the present invention provides a method for forming a low-resistance cobalt silicide film which does not cause a thin wire effect.

[0011]

According to the present invention, there is provided a step of forming a cobalt film on a semiconductor layer containing silicon, and a step of forming a cobalt silicide film by performing a first heat treatment by lamp annealing on the film. This is a method of forming a cobalt silicide film including a step of removing an unreacted cobalt film and a step of performing a second heat treatment on the cobalt silicide film again by lamp annealing.

According to the above-described method of the present invention, a cobalt film is formed on a semiconductor layer containing silicon, and a heat treatment is performed on the cobalt film twice by lamp annealing. A CoSi film is formed, and a CoSi ₂ film can be formed by a _second heat treatment by a second lamp annealing.
The i ₂ film can be formed with low resistance.

[0013]

DETAILED DESCRIPTION OF THE INVENTION A method for forming a cobalt silicide film according to the present invention comprises the steps of forming a cobalt film on a semiconductor layer containing silicon, and performing a first heat treatment by lamp annealing on the cobalt film to form the cobalt silicide film. The method includes a step of forming, a step of removing an unreacted cobalt film, and a step of performing a second heat treatment on the cobalt silicide film by lamp annealing.

According to the present invention, in the method of forming a cobalt silicide film, the step of performing the first heat treatment by lamp annealing on the cobalt film is performed at a temperature in the range of 450 to 550 ° C., and the second heat treatment by lamp annealing is performed again. The process is performed in the range of 650 to 900 ° C.

Further, the present invention, in the above-described method for forming a cobalt silicide film, further comprises a step of forming an antioxidant film on the cobalt film after the step of forming the cobalt film,
After the step of forming a cobalt silicide film by performing a first heat treatment by lamp annealing on the cobalt film, a step of removing the antioxidant film is employed.

According to the present invention, in the method of forming a cobalt silicide film, the semiconductor layer containing silicon and the cobalt silicide film are formed in a self-aligned manner.

Hereinafter, an embodiment of a method for forming a silicide film of the present invention will be described with reference to the drawings. In this example, a cobalt film is formed on silicon, and these are reacted to form a silicide film.

First, as shown in FIG. 1A, a semiconductor substrate 1 made of silicon or the like is placed on a region separated by an element isolation film 12 formed by performing LOCOS (local thermal oxidation) on the surface of the semiconductor substrate 1. A gate electrode 3 made of polycrystalline silicon is formed via a gate insulating film 2, a source / drain diffusion layer 4 is formed on the surface, and a side wall 5 made of an insulating film is formed on a side surface of the gate electrode 3.

Next, as shown in FIG. 1B, a cobalt film 6 covering the entire surface is formed by sputtering using Ar.
Is formed. The film forming conditions are, for example, DC power: 0.8 k
W, pressure: 0.4 Pa, gas flow rate: heater gas (A
r) 60 sccm, process gas (Ar) 30 scc
m, substrate temperature: 150 ° C., and film thickness: 10 nm.

Next, a heat treatment by a first lamp annealing is performed by a lamp annealing apparatus. The heat treatment temperature is
The temperature is set to 450 ° C. to 550 ° C. in a temperature region where CoSi is formed, and the flow rate is set to 10 liter / min in a nitrogen gas atmosphere.
Heat treatment is performed for seconds. Thereby, as shown in FIG. 2C,
The cobalt film 6 on the gate electrode 3 and the source / drain diffusion layer 4 is silicided by silicon of the gate electrode 3 and the source / drain diffusion layer 4 to form a CoSi film 7.

Next, as shown in FIG. 2D, the unreacted cobalt film 6 on the element isolation film 12 and the side walls 5 is removed by wet etching. The wet etching is performed at 70 ° C. for 3 minutes using, for example, sulfuric acid / hydrogen peroxide (a mixture of sulfuric acid: hydrogen peroxide = 4: 1).

Next, a second heat treatment is performed by a lamp annealing apparatus. At this time, the heat treatment is performed at a temperature of 650 to 900 ° C. at which CoSi ₂ is formed at a flow rate of 10 L / min in a nitrogen gas atmosphere for 30 seconds.

In this manner, as shown in FIG. 2E, a CoSi ₂ film 8 which is cobalt silicide having the lowest resistance phase is formed.

As a result, on the source / drain diffusion layer 4 and the gate electrode 3, there is no thin line effect and a low resistance (10 Ω /
□ or less) can be formed. In addition, since the heat treatment by lamp annealing is performed, the heat treatment can be performed in a short time and in an atmosphere having no oxidizing property, and there is no oxidation of the cobalt film and the cobalt silicide film, and the increase in resistance caused by the oxidation causes an annealing furnace. Less in comparison.

In the above-described example, the cobalt film is formed and silicidized by the lamp annealing method. However, when the cobalt film is formed and then opened to the atmosphere, the cobalt film surface is oxidized. Therefore, the thickness of the substantial cobalt that contributes to the formation of silicide is reduced. In order to prevent this oxidation, a TiN film is formed on the surface of the cobalt film,
The silicidation reaction can be further promoted. An example is shown below.

First, as shown in FIG. 3A, similarly to FIG. 1A, a gate electrode 3 is formed via a gate insulating film 2 in an element-isolated region of a semiconductor substrate 1, and a source / drain diffusion is formed in the semiconductor substrate 1. Sidewalls 5 are formed on the side surfaces of the layer 4 and the gate electrode 3, respectively.

Next, as shown in FIG. 3B, after a cobalt film 6 is formed in the same manner as in the previous example, the T film is continuously formed in the same device.
An iN film 9 is formed. The conditions for forming the cobalt film 6 are the same as in the previous example. The conditions for forming the TiN film 9 are, for example, DC power: 6.5 kW, pressure: 0.4 Pa, gas flow rate: heater gas (Ar) 15 sccm, process gas (N2) 135 sccm, substrate temperature: 150 ° C., and film thickness: 20 nm. And

Next, as shown in FIG. 3C, a heat treatment using a lamp annealing apparatus is performed to form the CoSi film 7 in the same manner as in the previous example, and then the TiN film 9 on the CoSi film 7 is removed by selective etching. The conditions of the lamp annealing method are as follows:
Perform the same as in the previous example. Subsequently, as shown in FIG. 4D, the TiN film 9 and the unreacted cobalt film 6 on the element isolation film 12 and the side walls 5 are sequentially removed by selective etching by wet etching. The wet etching of the TiN film is performed, for example, using ammonia peroxide (NH ₄ OH: H).
_The reaction is performed at 65 ° C. for 3 minutes using ₂ O ₂ : H ₂ O = 1: 2: 6). The wet etching of the unreacted cobalt film 6 is performed under the same conditions as in the previous example.

Thereafter, as in the previous example, a second heat treatment is performed by a lamp annealing apparatus. As a result, FIG.
As shown in E, the CoSi ₂ film 8 can be formed. The heat treatment can be performed in the same manner as in the above example.

Thus, a CoSi ₂ film, which is a low-resistance phase cobalt silicide, can be formed.

The CoSi ₂ film 8 thus formed is
Are formed in self-alignment with the gate electrode 3 and the source / drain diffusion layer 4.

Next, an example in which the amount of oxygen contained in the silicide film is further reduced to form a cobalt silicide film will be described below.

As described above, the cobalt film is easily oxidized by oxygen or the like in the atmosphere. The oxide film is removed from the surface of the semiconductor wafer by washing before the cobalt film is formed, but a natural oxide film remains slightly. The oxygen in the oxide film has a bad influence on the silicidation reaction as described above. Therefore, it is preferable that there is no natural oxide film.

First, as shown in FIG. 5A, similarly to the previous example, the gate electrode 3 and the source / drain diffusion layer 4 on the gate insulating film 2 are formed in the region of the semiconductor substrate 1 separated by the device isolation film 12. Sidewalls 5 are formed on the side surfaces of the gate electrode 3 respectively. At this time, the surface of the gate electrode 3 and the source / drain diffusion layer 4 are slightly
0 remains.

Next, as shown in FIG. 5B, in order to remove the natural oxide film 10 remaining on the surface, a reduced metal film 11 of Ti, Zr, Hf or the like having a large reducing action is covered by a sputtering method. It is formed entirely. The film forming conditions are, for example, D
C power: 0.5 kW, pressure: 0.4 Pa, gas flow rate:
Heater gas (Ar) 60 sccm, process gas (A
r) 30 sccm, substrate temperature: 150 ° C., film thickness: 20 n
m.

Next, as shown in FIG. 5C, the reduced metal film 1
The metal film 11 that has reduced the natural oxide film 10 is removed in the same apparatus where the wafer 1 is formed, and a clean wafer surface is exposed. As a method for removing the reduced metal film 11 at this time, a method such as soft etching that causes less damage to the substrate is used. The conditions of the soft etching are, for example, a gas flow rate (Ar) of 50 sccm, a pressure of 0.4 Pa, an RF bias of 0.3 kW, and a substrate temperature of 600 ° C.

Next, as shown in FIG. 6D, a cobalt film 6 and a TiN film 9 are sequentially formed by a sputtering method as in the previous example.

Next, as shown in FIG. 6E, similarly to the previous example, the first heat treatment by the lamp annealing method is performed, so that the C electrode is formed on the gate electrode 3 and the source / drain diffusion layer 4.
An oSi film 7 is formed.

Next, as shown in FIG. 6F, the TiN film 9 and the unreacted cobalt film 6 are removed by wet etching as in the previous example.

Thereafter, as in the previous example, a second heat treatment by a lamp annealing method is performed to form a CoSi ₂ film 8 which is a low-resistance phase cobalt silicide. Thus, a low-resistance cobalt silicide film can be formed on the diffusion layer and the gate as described above.

The silicon-containing layer forming the cobalt silicide film is composed of a diffusion layer or a polycrystalline silicon layer in a silicon substrate as described above, and a cobalt film is formed thereon and lamp annealing is performed twice. By the heat treatment by the method, a cobalt silicide film can be formed in a self-alignment manner on these diffusion layers and polycrystalline silicon layers.

The method of forming a cobalt silicide film of the present invention is not limited to the above-described example, and may take various other configurations without departing from the gist of the present invention.

[0043]

According to the method of forming a cobalt silicide film according to the present invention described above, heat treatment is performed twice at a predetermined temperature by lamp annealing, so that there is no thin line effect on the diffusion layer and the gate, and the resistance is low. (About 10 Ω / □ or less) can be formed.

Further, since the heat treatment by lamp annealing is performed, the heat treatment can be performed in a short time and in an atmosphere having no oxidizing property, and the cobalt film and the cobalt silicide film are not oxidized, and the resistance caused by the oxidation is increased. Characteristic can be prevented.

Therefore, by applying the method of the present invention to the so-called salicide method, it is possible to reduce the resistance and speed of the semiconductor device.

[Brief description of the drawings]

FIGS. 1A and 1B are process diagrams of one manufacturing process of an embodiment of a method for forming a cobalt silicide film of the present invention.

FIGS. 2A to 2E are process diagrams of one manufacturing process of an embodiment of a method for forming a cobalt silicide film of the present invention.

3A to 3C are process diagrams of a manufacturing process according to another embodiment of the method for forming a cobalt silicide film of the present invention.

FIGS. 4D and 4E are process diagrams of a manufacturing process of another embodiment of the method for forming a cobalt silicide film of the present invention.

5A to 5C are process diagrams of a manufacturing process according to still another embodiment of the method for forming a cobalt silicide film of the present invention.

FIGS. 6A to 6F are process diagrams of a manufacturing process according to still another embodiment of the method of forming a cobalt silicide film of the present invention.

FIG. 7 is a diagram showing the relationship between the width of the diffusion layer and the sheet resistance when a titanium silicide film is formed on the diffusion layer. This is the case where it is formed on the A n ⁺ source / drain diffusion layer. This is the case where it is formed on the B p ⁺ source / drain diffusion layer.

FIG. 8 is a diagram showing a relationship between the width of the diffusion layer and the sheet resistance when a cobalt silicide film is formed on the diffusion layer. This is the case where it is formed on the A n ⁺ source / drain diffusion layer. This is the case where it is formed on the B p ⁺ source / drain diffusion layer.

[Explanation of symbols]

1 semiconductor substrate, 2 gate insulating film, 3 gate electrode,
4 Source / drain diffusion layers, 5 sidewalls, 6
Cobalt film, 7 CoSi film, 8 CoSi ₂ film, 9
TiN film, 10 natural oxide film, 11 reduced metal film, 1
2 Device separation membrane

Claims (4)

[Claims] 1. A step of forming a cobalt film on a semiconductor layer containing silicon, a step of performing a first heat treatment by lamp annealing on the cobalt film to form a cobalt silicide film, and removing an unreacted cobalt film. And a second step of lamp annealing the cobalt silicide film.
A method of forming a cobalt silicide film, comprising a step of performing a heat treatment. 2. A step of performing a first heat treatment by lamp annealing on the cobalt film in the range of 450 to 550 ° C., and a step of performing the second heat treatment by lamp annealing in the range of 650 to 900 ° C. The method for forming a cobalt silicide film according to claim 1, wherein: 3. After the step of forming the cobalt film,
A step of forming an antioxidant film on the cobalt film, a step of performing a first heat treatment by lamp annealing on the cobalt film to form a cobalt silicide film, and then removing the antioxidant film. The method for forming a cobalt silicide film according to claim 1. 4. The method for forming a cobalt silicide film according to claim 1, wherein the semiconductor layer containing silicon and the cobalt silicide film are formed in a self-aligned manner.