JPH0547698A - Manufacture of mos-type semiconductor device - Google Patents

Abstract

PURPOSE:To provide a manufacture of a MOS-type semiconductor device where junction leakage is hard to occur in the diffused layer below a silicide film. CONSTITUTION:The natural oxide film 21 on the surface of an Si substrate is removed, and then a metallic film is made on the surface, and in this condition, heat treatment is performed to form a silicide film 23. Since the metallic film and the Si substrate 21 react with each other in the condition that a natural oxide film nonuniform in thickness does not exists between the Si substrate 11 and the metallic film, the silicide film 23 uniform in thickness is made on the surface of the Si substrate 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a MOS type semiconductor device having a silicide film formed on a diffusion layer formed on a silicon substrate.

[0002]

2. Description of the Related Art In a MOS transistor, for example, if the channel length is shortened for miniaturization, the influence of the drain voltage extends to the source diffusion layer and the controllability of the gate voltage is lost. As a result, deterioration of the subthreshold characteristic, which is one phenomenon of the short channel effect, occurs.

Therefore, in order to reduce this phenomenon, the junction is made shallow to suppress the spread of the depletion layer from the drain diffusion layer. In this case, the sheet resistance is remarkably high only with the shallow diffusion layer. Therefore, a silicide film is formed on the surface of the source / drain diffusion layer to reduce the sheet resistance and the contact resistance at the same time.

Also, for example, in the case of a diffusion layer used as a source / drain connection, a power supply line, a ground line, etc., a silicide film is formed in order to reduce the sheet resistance of the shallow diffusion layer. ..

As a method of forming this silicide film, a method of reacting a metal such as Ti or W with Si constituting a substrate or a gate electrode by a heat treatment to form a silicide, and a method of forming a silicide film by a sputtering method are used. There is a method of forming directly.

Among them, the method by heat treatment is effective even if the above-mentioned metal film is formed on the entire surface of the Si substrate.
This is a useful method because only the exposed source / drain diffusion layers and gate electrodes of a MOS transistor can be silicided in a self-aligned manner, that is, salicided.

[0007]

However, for example, when a clean Si surface is exposed to the atmosphere at room temperature, a natural oxide film is formed on the surface. Since this natural oxide film generally has an extremely non-uniform film thickness, when such a natural oxide film is present between the Si surface and the metal film, the heat treatment as described above is performed. The silicidation of the metal film proceeds nonuniformly. As a result, the thickness of the formed silicide film becomes non-uniform, and the diffusion layer below the silicide film and S
Junction leakage is likely to occur at the pn junction with the i substrate.

Therefore, an object of the present invention is to provide a method of manufacturing a MOS type semiconductor device capable of forming a silicide film having a uniform thickness on a diffusion layer formed on a silicon substrate in a self-aligned manner. Is.

[0009]

In order to solve the above-mentioned problems, the present invention provides a method for manufacturing a MOS type semiconductor device in which a silicide film is formed on a diffusion layer formed on a silicon substrate. The native oxide film on the silicon substrate is removed before forming a metal film for reacting with the substrate for silicidation.

[0010]

In the method of manufacturing a MOS semiconductor device according to the present invention, a natural oxide film having a non-uniform thickness is not formed between the surface of the silicon substrate and the metal film, and the metal film is formed on the silicon substrate. Since it reacts with and silicidizes, silicidation proceeds uniformly, and as a result, a silicide film having a uniform film thickness is formed on the surface of the silicon substrate.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a method of manufacturing a MOS transistor will be described below with reference to FIG.

In this embodiment, first, as shown in FIG. 1A, the LOCO is formed on the surface of the element isolation region of the Si substrate 11.
The SiO ₂ film 12 is formed by the S method. Then, a SiO ₂ film 14 which is a gate oxide film is formed on the surface of the active region 13 by the thermal oxidation method.

Then, a polycrystalline Si film 15 is deposited on the entire surface of the Si substrate 11 by the CVD method. Then, a resist (not shown) is applied on the polycrystalline Si film 15,
This resist is processed into a gate electrode pattern by lithography.

Next, the polycrystalline Si film 15 is anisotropically etched using the resist as a mask to process the polycrystalline Si film 15 into a gate electrode pattern. When this anisotropic etching is completed, the resist is removed by ashing with oxygen plasma.

Next, the polycrystalline Si film 15 and the SiO ₂ film 1
Source / drain diffusion layers 16 are formed by ion-implanting impurities into the active region 13 using 2 as a mask. At this time, the polycrystalline Si film 15 is also doped with the same impurities as the impurities doped in the source / drain diffusion layers 16.

After that, the SiO ₂ film 17 is deposited on the entire surface of the Si substrate 11 by the CVD method. And this S
By etching back the entire surface of the iO ₂ film 17, side walls made of the SiO ₂ film 17 are formed on the side surfaces of the polycrystalline Si film 15.

In this state, when the surface of the active region 13 is exposed to the atmosphere at room temperature, a native oxide film 21 having a film thickness of, for example, 50 to 70Å is formed on the surface of the active region 13. Therefore, in this embodiment, as shown in FIG. 1B, the natural oxide film 21 is removed from the surface of the active region 13 by reverse sputtering (sputter etching) using Ar ⁺ ions 22.

Next, a metal film such as a Ti film or a W film is formed on the entire surface of the Si substrate 11 by the vapor deposition method or the like. And
When heat treatment is performed in this state, as shown in FIG.
The metal film on the source / drain diffusion layer 16 and the polycrystalline Si film 15 reacts with Si of the Si substrate 11 and the polycrystalline Si film 15 to form a silicide film 23 such as a TiSi ₂ film or a WSi ₂ film.
And the metal film 24 on the SiO ₂ films 12 and 17 remains unreacted.

Therefore, only the metal film 24 which remains unreacted is selectively removed by etching. As a result,
As shown in (d), the silicide film 23 is formed in a self-aligned manner only on the surface of the source / drain diffusion layer 16 and the upper surface side of the polycrystalline Si film 15. That is, the silicide film 23 is formed on the source / drain diffusion layer 16, the source / drain regions are silicided in a self-aligned manner, and the gate electrode has a polycide structure.

According to the manufacturing method of this embodiment, since the natural oxide film 21 is removed from the surface of the active region 13 before the deposition of the metal film, the silicidation of the metal film proceeds uniformly, and as a result, the film is formed. The silicide film 23 having a uniform thickness can be obtained. Therefore, the source / drain diffusion layer 16 and the Si substrate 1
A junction leak is unlikely to occur in the pn junction between the first and the second junctions.

The shallow source / drain diffusion layer 16 can be formed by various methods. For example, ion implantation of impurities may be performed at a low acceleration voltage, or unlike the above-described embodiment, a metal film may be deposited on the Si substrate 11 and then the Si substrate 11 may be ion-implanted through the metal film. Further, after the metal film is silicidized to form the silicide film 23, S is formed through the silicide film 23.
It can be formed by performing ion implantation into the i substrate 11, or further by implanting impurities only into the silicide film 23 once and diffusing the impurities from the silicide film 23 into the Si substrate 11 by heat treatment.

[0022]

According to the present invention, since a silicide film having a uniform thickness can be formed on the surface of a silicon substrate, a junction leak is unlikely to occur in the diffusion layer below this silicide film.

[Brief description of drawings]

1A to 1D are diagrams illustrating an M according to an embodiment of the present invention.
FIG. 6 is a cross-sectional view showing the method of manufacturing the OS transistor in the order of steps.

[Explanation of symbols]

 11 Si substrate 16 source / drain diffusion layer 21 natural oxide film 23 silicide film 24 unreacted metal film

Claims (1)

[Claims] 1. A method of manufacturing a MOS type semiconductor device in which a silicide film is formed on a diffusion layer formed on a silicon substrate, before forming a metal film for reacting with the silicon substrate for silicidation. A method comprising removing a native oxide film on the silicon substrate.