JPH06124959A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain the manufacturing method of a semiconductor device wherein the design dimension precision of a device is improved without generating crystal defect in a semiconductor substrate, and excellent ohmic contact between a metal silicide layer and the semiconductor substrate can be realized. CONSTITUTION:A semiconductor substrate 1 wherein a gate electrode 3, a source 20 and a drain 21 are formed is set in a mixed gas atmosphere containing chlorine fluoride gas and hydrogen gas. By irradiating the mixed gas with ultraviolet rays, a natural oxide film 8 formed on the semiconductor substrate 1 is eliminated. Then a metal silicide layer 10 is formed on the gate electrode 3 surface, the source 20, and the drain 21.

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 semiconductor device, and more particularly, to a MOS (Me) capable of making good ohmic contact between a metal silicide layer and a semiconductor substrate.
tal Oxide Semiconductor) and a method for manufacturing a semiconductor device having a transistor formed therein.

[0002]

2. Description of the Related Art Conventionally, LSI (Large Scale Integration)
With the high integration of ated circuits), miniaturization of devices has been increasingly required. The miniaturization of this device is
The SI is performed not only in the lateral direction (direction parallel to the surface of the semiconductor substrate) but also in the height direction (direction perpendicular to the surface of the semiconductor substrate). Therefore, the parasitic resistance of the gate electrode and the source and drain of the MOS transistor increases rapidly,
There is a problem that the operating speed of the circuit is significantly deteriorated.

Therefore, as disclosed in Japanese Patent Publication No. 2-37093, by forming a low resistance metal silicide layer on the surface of the gate electrode and the source and drain, the surface of the gate electrode and the source are formed. And the resistance of the layer formed on the drain is changed from the conventional tens to hundreds of Ω / □ to several Ω.
Conventional examples have been proposed in which the device characteristics are improved by reducing the value to / □.

Generally, the metal silicide layer formed on the surface of the gate electrode and the source and drain is stable on the entire surface of the semiconductor substrate on which the gate electrode, source and drain are formed, and a stable metal. An unreacted metal film is formed by forming a metal film capable of forming a compound and subjecting it to heat treatment (annealing) to silicify only the metal film formed on the gate electrode and the source and drain. Is selectively removed by etching.

However, when the metal silicide layer is formed by the above method, a natural oxide film is formed on the gate electrode or the semiconductor substrate when forming the metal film capable of forming a stable compound with the semiconductor material. If present, during the heat treatment for silicidation, the natural oxide film hinders the alloying of the metal film and the semiconductor (silicon) and the silicidation reaction becomes non-uniform, resulting in ohmic contact between the metal silicide layer and the semiconductor substrate. There was a problem that I could not get enough.

Therefore, usually, a semiconductor substrate before forming a metal film capable of forming a stable compound with the semiconductor material is subjected to chemical treatment using an HF solution. However, the chemical solution treatment using this HF solution has a problem that a natural oxide film is formed again on the semiconductor substrate or on the surface of the gate electrode because it is necessary to wash with pure water after the chemical solution treatment. It was In addition, an oxide film intentionally formed by the HF solution, such as an oxide film for isolation between elements (field oxide film) or an oxide film for protecting the gate sidewall (sidewall), which is necessary for forming a semiconductor device. However, there is a problem in that the device design dimensions are changed and the device characteristics are hindered because they are simultaneously etched.

Therefore, in Japanese Patent Publication No. 2-37093, in order to eliminate the adverse effect caused by the natural oxide film,
By implanting impurity ions into the interface between the metal film capable of forming a stable compound with the semiconductor material and the semiconductor substrate and the gate electrode, the natural oxide film is destroyed,
Good ohmic contact between the metal silicide layer and the semiconductor substrate.

[0008]

However, the method of destroying the natural oxide film by ion implantation, which is introduced in the above Japanese Patent Publication No. 2-37093, provides good ohmic contact between the metal silicide layer and the semiconductor substrate. On the other hand, there is a problem that damage to the ion implantation occurs inside the semiconductor substrate and junction leakage increases, which adversely affects the device characteristics.

If the natural oxide film is not destroyed uniformly, silicidation becomes non-uniform in the subsequent heat treatment step, and, for example, during reflow of the interlayer insulating film (after heat treatment). When about 1000 ° C. is applied to the above), the metal silicide layer aggregates, causing a serious problem that the layer resistance in the gate portion, the source and the drain portion increases.

An object of the present invention is to solve such a problem and to improve the design dimensional accuracy of a device without causing crystal defects inside the semiconductor substrate,
Moreover, it is an object of the present invention to provide a method for manufacturing a semiconductor device capable of making good ohmic contact between a metal silicide layer and a semiconductor substrate.

[0011]

In order to achieve this object, according to the present invention, a metal silicide layer is formed on a surface of a gate electrode formed on a semiconductor substrate via a gate oxide film and on a source and a drain. In the method of manufacturing a semiconductor device, the gate electrode, the semiconductor substrate on which the source and drain are formed, chlorine fluoride gas, hydrogen gas,
And a step of irradiating the mixed gas with ultraviolet rays to remove the natural oxide film on the semiconductor substrate, and after removing the natural oxide film, the gate electrode surface, source and The present invention provides a method for manufacturing a semiconductor device, which comprises the step of forming a metal silicide layer on the drain.

[0012]

According to the present invention, a semiconductor substrate having a gate electrode, a source and a drain is placed in a mixed gas atmosphere containing chlorine fluoride gas and hydrogen gas, and the mixed gas is irradiated with ultraviolet rays. Therefore, the mixed gas reacts as shown by 2ClF ₃ + 3H ₂ → 6HF ^* + Cl ₂ to generate HF radicals. The generated HF radicals can remove the natural oxide film formed on the semiconductor substrate or on the surface of the gate electrode. Here, since the amount of HF radicals generated by the reaction is extremely small, the etching rate with respect to the natural oxide film which is a low-grade oxide film is high, but like the field oxide film and the sidewall which are dense films, The etching rate for the oxide film necessary for forming the semiconductor device becomes small. Therefore, when the natural oxide film is removed, the field oxide film, the side wall, etc. are not etched, so that the design dimension of the device does not change. In addition, at this time, Cl generated simultaneously
_{Since 2} (chlorine) immediately becomes Cl ₂ + H ₂ → 2HCl, the semiconductor substrate and the gate electrode are not etched by the chlorine radical. Therefore, only the natural oxide film formed on the semiconductor substrate or on the surface of the gate electrode can be selectively removed.

After removing the natural oxide film by the above method, on the surface of the gate electrode, the source and the drain,
Since the metal silicide layer is formed, a uniform silicide reaction can be performed. Therefore, for example, even when heat of about 1000 ° C. is applied to the metal silicide layer during the subsequent reflow (heat treatment) of the interlayer insulating film, the metal silicide layer does not aggregate. Therefore, the layer resistance in the gate portion, the source and the drain portion does not increase, and good ohmic contact can be established between the metal silicide layer and the semiconductor substrate.

Furthermore, since ion implantation for destroying the natural oxide film is not required, crystal defects are not generated inside the semiconductor substrate, junction leakage can be reduced, and device characteristics can be improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment according to the present invention will be described with reference to the drawings. 1 to 5 are partial cross-sectional views showing a part of a manufacturing process of a MOS type semiconductor device according to an embodiment of the present invention, and FIG. 6 shows an apparatus used for removing a natural oxide film in this embodiment. FIG.

In the process shown in FIG. 1, a p-type semiconductor substrate 1 is used.
A field oxide film 7 is formed in the element isolation region by a known selective oxidation technique. Next, an oxide film with a film thickness of about 15 nm is formed in the element formation region of the semiconductor substrate 1. Then, a polycrystalline silicon film having a film thickness of about 350 nm is formed on the oxide film, and an impurity for reducing the resistance is doped therein. Next, the polycrystalline silicon film doped with the impurities and the oxide film are patterned to form a gate electrode 3 and a gate oxide film 2. Then, using the gate electrode 3 as a mask, n-type impurities are ion-implanted into the semiconductor substrate 1 at a low concentration to form an n ⁻ diffusion layer 6
070 tails 16 are formed. Next, for example, CV is formed on the entire surface of the semiconductor substrate 1, the gate electrode 3, and the gate oxide film 2.
The film thickness is 2 by D (Chemical Vapor Deposition) method.
An oxide film of about 00 nm is formed. Next, anisotropic etching is performed on this oxide film by reactive ion etching to form sidewalls 4 made of the oxide film on the sidewalls of the gate electrode 3. Next, using the side wall 4 and the gate electrode 3 as a mask, n-type impurities are ion-implanted into the semiconductor substrate 1 at a high concentration to form n ⁺ diffusion layers 5 and 15, and an LDD (Lightly Doped Drain) is formed.
Structure) Get the structure. Thus, the source 20 composed of the n ⁺ diffusion layer 5 and the n ⁻ diffusion layer 6 and the n ⁺ diffusion layer 1 are formed.
5, the drain 21 composed of the n ⁻ diffusion layer 16 was formed.
Then, the semiconductor substrate 1 is heat-treated to electrically activate the n-type impurities ion-implanted into the source 20 region and the drain 21 region. Here, the gate electrode 3
A natural oxide film 8 was formed on the surface, the source 20 and the drain 21.

Next, in the step shown in FIG. 2, the semiconductor substrate 1 obtained in the step shown in FIG.
1, and the semiconductor substrate 1 is placed on the stage 32. Then, a ClF ₃ nozzle 34 is supplied from a gas supply box (not shown) for supplying ClF ₃ gas as chlorine fluoride gas into the chamber 31 of the apparatus shown in FIG.
Supplying a ClF ₃ gas, the H ₂ gas (hydrogen gas) to the feeding box (not shown) via of H ₂ nozzle 35 H ₂ gas through. At this time, the partial pressure of the gas is
The ClF ₃ gas was adjusted to 0.1 to 100 Torr, and the H ₂ gas was adjusted to 200 to 300 Torr.

Then, in a mixed gas atmosphere containing the ClF ₃ gas and the H ₂ gas, ultraviolet rays (UV light) having a wavelength of 150 to 350 nm are directed toward the surface of the semiconductor substrate 1.
Is emitted from the ultraviolet light lamp 33. In this embodiment, a low pressure mercury lamp is used as the ultraviolet lamp 33. By the irradiation of this ultraviolet ray, the mixed gas in the chamber 31 reacts as shown by 2ClF ₃ + 3H ₂ → 6HF ^* + Cl ₂ , and the generated HF radical causes
The natural oxide film 8 formed on the surface of the semiconductor substrate 1 is removed. At this time, since the amount of HF radicals generated is extremely small, the etching rate for the natural oxide film 8 which is a low-grade oxide film is high, but the etching rate for the field oxide film 7 and the sidewall 4 which are dense films is high. Get smaller. Therefore, the field oxide film 7 and the sidewalls 4 are not etched when the natural oxide film 8 is removed. Therefore, the design dimensions of the device do not change and the device characteristics are not hindered.

Further, at this time, Cl simultaneously produced
_{Since 2} immediately becomes Cl ₂ + H ₂ → 2HCl, the semiconductor substrate 1 and the gate electrode 3 are not etched by chlorine radicals. Therefore, only the natural oxide film 8 formed on the surface of the semiconductor substrate 1 can be selectively removed.

Next, in the step shown in FIG. 3, the surface of the gate electrode 3 from which the natural oxide film 8 has been removed in the step shown in FIG.
On the source 20 and the drain 21, and the field oxide film 7
On the upper surface of the sidewall 4, a titanium film 9 having a film thickness of about 300 Å is formed as a metal film capable of forming a stable compound with a semiconductor material. Next, in the step shown in FIG. 4, the titanium film 9 obtained in the step shown in FIG. 3 is subjected to heat treatment (annealing) to bring the titanium film 9 in contact with the semiconductor, that is, the surface of the gate electrode 3, the source 20 and Drain 21
The titanium film 9 formed thereon is silicidized to form a titanium silicide layer 10 having a film thickness of about 700Å.

Next, in the step shown in FIG. 5, the titanium film 9 which has not been silicided in the step shown in FIG.
The unreacted titanium film 9 formed on the field oxide film 7 and on the surface of the sidewall 4 is, for example, H ₂ O ₂ /
Removal with an aqueous solution containing NH ₄ OH.
Then, the titanium silicide layer 10 obtained in the step shown in FIG.
An interlayer insulating film is formed on the upper side, the field oxide film 7 and the sidewall 4 surface, contact holes are formed in the gate electrode 3, the source 20 and the drain 21, and desired metal wiring and a final protective film are formed. A MOS type semiconductor device (invention product) was completed.

In the MOS semiconductor device according to the present embodiment, the layer resistance in the gate portion, the source and drain portions after the high temperature heat treatment process performed for the purpose of reflowing the interlayer insulating film, and the gate portion before the reflow are performed. The layer resistances at the source and drain portions showed almost the same value. Next, as a comparison, a MOS type semiconductor device (comparative product 1) was manufactured in the same process as in the above embodiment without providing a titanium silicide layer.
Was manufactured.

Next, when the layer resistances at the gate portion, the source and the drain portion of the invention product and the comparative product 1 were measured,
The layer resistance of the invention product was 3 to 5 Ω / □, and the layer resistance of Comparative product 1 was 80 to 200 Ω / □. From this, it was confirmed that the invention product can significantly reduce the signal delay time in the diffusion layer wiring extending from the drain 21 (or the source 20). Further, the junction leakage current was almost the same in both the invention product and the comparative product 1.

Next, as another comparison, after removing the natural oxide film formed on the semiconductor substrate or the gate electrode before the titanium film is formed using the HF solution, the same steps as those in the above-described embodiment are performed. Then, a MOS type semiconductor device (Comparative product 2) was manufactured. In this comparative product 2, the layer resistance in the gate part, the source and the drain part after the high temperature heat treatment performed for the purpose of reflowing the interlayer insulating film is 5 to 5 times the layer resistance in the gate part, the source and the drain part before the reflow. That was six times higher.

In this embodiment, in the process shown in FIG.
Although ClF ₃ gas was used as the chlorine fluoride gas, the present invention is not limited to this, and the same effect can be obtained by using Cl ₂ F ₆ , ClF ₂ , ClF or the like. Further, in the process shown in FIG. 2, a low-pressure mercury lamp is used as the ultraviolet light lamp 33, but the invention is not limited to this, and any ultraviolet light such as an excimer laser that emits ultraviolet light (ultraviolet light) can be used. Of course, a lamp may be used.

Further, in the process shown in FIG. 3, the titanium film 9 is formed as a metal film capable of forming a stable compound with a semiconductor material, but the present invention is not limited to this, and iridium, tantalum, palladium, platinum, nickel. Other metals, such as tungsten, may be used as long as they can form a stable compound with a semiconductor material. In addition, although the process of manufacturing the MOS type semiconductor device having the LDD structure has been described in the present embodiment, the present invention is not limited to this, and for example, a metal film capable of silicidation is formed before forming the source and the drain. The present invention is also effective in other steps such as siliciding this metal film to form a metal silicide layer and then forming a source and a drain.

The present embodiment is an example, and the present invention is not limited to the above embodiment.

[0028]

As described above, according to the method of manufacturing a semiconductor device of the present invention, a semiconductor substrate having a gate electrode, a source and a drain is mixed with chlorine fluoride gas and hydrogen gas. Since the mixed gas is charged into a gas atmosphere to irradiate the mixed gas with ultraviolet rays, the mixed gas reacts as shown by 2ClF ₃ + 3H ₂ → 6HF ^* + Cl ₂ to generate an extremely small amount of HF radicals. Only the natural oxide film formed on the semiconductor substrate or on the surface of the gate electrode can be selectively removed. Therefore, when removing the natural oxide film, the field oxide film, sidewalls, etc. are not etched. Moreover, since Cl ₂ simultaneously generated at this time immediately becomes Cl ₂ + H ₂ → 2HCl, the semiconductor substrate, the gate electrode, and the like are not etched by the chlorine radical. As a result, the design dimension of the device does not change, so that the device characteristics can be improved.

Further, after removing the natural oxide film by the above method, on the surface of the gate electrode, the source and the drain,
Since the metal silicide layer is formed, a uniform silicidation reaction can be performed, and the metal silicide layer does not aggregate during the high temperature heat treatment to be performed thereafter, so that the layer resistance does not increase. As a result, a good ohmic contact can be made between the metal silicide layer and the semiconductor substrate.

Furthermore, since ion implantation for destroying the natural oxide film is not required, crystal defects are not generated inside the semiconductor substrate, and device characteristics such as junction leak can be improved.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a part of a manufacturing process of a MOS semiconductor device according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view showing a part of the manufacturing process of the MOS semiconductor device according to the embodiment of the invention.

FIG. 3 is a partial sectional view showing a part of the manufacturing process of the MOS semiconductor device according to the embodiment of the invention.

FIG. 4 is a partial cross-sectional view showing a part of the manufacturing process of the MOS semiconductor device according to the embodiment of the invention.

FIG. 5 is a partial sectional view showing a part of the manufacturing process of the MOS semiconductor device according to the embodiment of the invention.

FIG. 6 is a cross-sectional view of an apparatus used for removing a natural oxide film in this example.

[Explanation of symbols]

1 semiconductor substrate 2 gate oxide film 3 gate electrode 4 sidewall 5 n ⁺ diffusion layer 6 n ^- diffusion layer 7 field oxide film 8 natural oxide film 9 titanium film 10 titanium silicide film 15 n ⁺ diffusion layer 16 n ^- diffusion layer 20 source 21 drain

Claims (1)

[Claims] 1. A method of manufacturing a semiconductor device, comprising: a gate electrode surface formed on a semiconductor substrate via a gate oxide film; and a metal silicide layer formed on a source and a drain, the gate electrode, the source and the drain. A step of charging the semiconductor substrate on which is formed a mixed gas atmosphere containing chlorine fluoride gas and hydrogen gas, irradiating the mixed gas with ultraviolet rays, and removing the natural oxide film on the semiconductor substrate. When,
A step of forming a metal silicide layer on the surface of the gate electrode, the source and the drain after removing the native oxide film.