KR100456316B1 - Method for forming gate in semiconductor device - Google Patents

Abstract

Since a method of forming polysilicon and tungsten laminated gates having improved interfacial resistance properties between polysilicon and tungsten is disclosed, the gate forming method of the semiconductor device of the present invention includes a gate insulating film, a polysilicon film, and a tungsten-rich WSi on a semiconductor substrate. stacking _x films, diffusion barrier films, and tungsten films in sequence; Patterning the stacked films by a gate mask and an etching process; and performing a selective oxidation to selectively oxidize the polysilicon film to react the tungsten-rich WSi _x film with the polysilicon film to react the tungsten film with the polysilicon film. And forming a tungsten silicide film at the interface between the silicon films.

Description

Method for forming gate in semiconductor device

The present invention relates to a method of forming a gate electrode of a semiconductor device, and more particularly, to a method of forming a gate electrode having a laminated structure of polysilicon and tungsten.

As is well known, gates of highly integrated MOSFETs with fine line widths have been extensively studied for materials for low resistance. The gate structure, which has a laminated structure of polysilicon and tungsten, is applied to 256M DRAM or more because it has a resistivity of 1/10 or less and excellent thermal stability than the gate structure of polysilicon and tungsten silicide.

1A and 1B are cross-sectional views of respective processes for explaining a gate electrode forming method having a stacked structure of polysilicon and tungsten according to the prior art.

Referring to FIG. 1A, a gate insulating film 2, a polysilicon film 3, a diffusion barrier film 4 such as a tungsten nitride film WN _x as a conductive material, and a tungsten layer are formed on a semiconductor substrate 1 on which an element formation region is defined. The film 5 is formed in turn, and the gate electrodes 10 are formed in the element formation region by patterning the films 5, 4, 3, 2 through a known etching process.

Referring to FIG. 1B, the damage caused by the etching process for forming the gate electrode 10, for example, the damage applied to the gate electrode 10 and the gate insulating film 2 is recovered, and The semiconductor substrate 1 on which the gate 10 is formed is heat-treated in an oxidation process, that is, an oxidizing atmosphere, so as to prevent damage due to lightly doped drain (LDD) ion implantation to be performed later.

At this time, the heat treatment is performed by a selective oxidation process of oxidizing only silicon so that the tungsten film 4 is prevented from being oxidized. As a result of the oxidation process, the surface of the semiconductor substrate 1 and the gate insulating film 2 and the polysilicon are An oxide film 11 is formed on the sidewall of the film 3.

2 illustrates a problem of the prior art caused by the selective oxidation process.

When the oxidation process is performed in an oxygen atmosphere, tungsten is rapidly oxidized to expand the volume, which causes gate peeling. Therefore, a selective oxidation process in which only silicon is selectively oxidized while preventing tungsten oxidation is applied.

The selective oxidation process selectively oxidizes only silicon using the Gibb's free energy difference of tungsten and silicon in H ₂ O / H ₂ atmosphere, and oxidizes according to the ratio and temperature of H ₂ O / H ₂ . The selection ratio changes.

However, during the selective oxidation, oxygen (O) penetrates the interface between the polysilicon (2) and tungsten (5) to form an oxide (4a) in the form of SiON, and thus the electrical contact area of the polysilicon and tungsten is increased. Relatively decreasing, the interface resistance increases rapidly, which impedes low-resistance gate implementation.

An object of the present invention is to provide a gate forming method of a semiconductor device to improve the interfacial resistance characteristics of polysilicon and tungsten.

1A and 1B are cross-sectional views of respective processes for explaining a method of forming a gate electrode having a laminated structure of polysilicon and tungsten according to the prior art;

Figure 2 is a cross-sectional view for showing the problems of the prior art.

3A and 3B are cross-sectional views of respective processes for explaining a method of forming a gate electrode according to an exemplary embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings *

101 semiconductor substrate 102 gate insulating film

103 polysilicon film 104 tungsten-rich WSi _x film

105: diffusion barrier 106; Tungsten film

107: mask insulating film 104A: WSi ₂ film

105A: oxide 110: oxide film by selective oxidation

A method of forming a gate of a semiconductor device of the present invention for achieving the above object comprises the steps of laminating a gate insulating film, a polysilicon film, a tungsten-rich WSi _x film, a diffusion barrier film, a tungsten film in sequence on the semiconductor substrate; Patterning the stacked films by a gate mask and an etching process; and performing selective oxidation to selectively oxidize the polysilicon film without oxidation of the tungsten film to react the tungsten-rich WSi _x film with the polysilicon film. And forming a tungsten silicide film at an interface between the tungsten film and the polysilicon film.

In the present invention described above, the tungsten-rich WSi _x film is formed to a thickness of 20 to 100 GPa, and is characterized by 1.0 <x <2.0.

In the present invention, the tungsten-rich WSi _x film is formed by depositing in-situ without vacuum destruction after deposition of the polysilicon film.

In the present invention, the selective oxidation is characterized in that it is carried out at 700 ~ 1100 ℃ in H ₂ O / H ₂ atmosphere.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. do.

3A and 3B are cross-sectional views of respective processes for explaining a method of forming a gate electrode according to the present invention.

Referring to FIG. 3A, a gate insulating film 102, a polysilicon film 103, a tungsten-rich WSi _x film 104, for example, a conductive material may be formed on a semiconductor substrate 101 on which a device formation region is defined. A diffusion barrier film 105 such as tungsten nitride film WN _x and a tungsten film 106 are sequentially formed, and a mask insulating film 107 is formed thereon.

The thickness of the tungsten-rich WSi _x film 104 is selected to be a thickness suitable for forming a tungsten silicide film in a subsequent selective oxidation process, and is preferably set to 20 to 100 kPa. Moreover, it is preferable to set 1.0 <x <2.0 in WSi _x .

In addition, the deposition of the tungsten-rich WSi _x film 104 is deposited in-situ without vacuum breakdown after the deposition of the polysilicon 103 and thus the polysilicon 103 and the tungsten-rich WSi _x film 104 are deposited. It is preferable to suppress the formation of a natural oxide film at the interface between the films 104.

In addition, the mask insulating film 107 is suppressed from being decomposed to the tungsten nitride film WN _x , which is a conductive material, by using a deposition process for 30 seconds to 2 hours at 800 ° C. or lower.

Subsequently, the gate electrodes 120 are formed in the device formation region by patterning the layers 107, 106, 105, 104, and 103 through a conventional gate mask and etching process.

Referring to FIG. 3B, damage caused by an etching process for forming the gate electrode 120, for example, damage applied to the gate electrode 120 and the gate insulating layer 102 is recovered, and The resultant is reoxidized to prevent damage by lightly doped drain (LDD) ion implantation to be performed subsequently.

In this case, the re-oxidation process is performed in a selective oxidation process to oxidize only silicon so that the tungsten film 106 is prevented from being oxidized. As a result of the oxidation process, the surface of the semiconductor substrate 101 and the gate insulating film 102 and poly The oxide film 110 is formed on the sidewall of the silicon film 103. Process conditions at the time of selective oxidation are preferably 0.01? H ₂ O / H ₂ ? 0.5, 700 to 1100 ℃, 30 seconds to 2 hours.

During the selective oxidation, oxide 105A will be formed at the interface between tungsten 106 and polysilicon 103. However, in the present invention, the tungsten-rich WSi _x film 104 reacts with the polysilicon 103 to form the tetragonal WSi ₂ film 104A, breaking the oxide 105A. To form an ohmic contact of tungsten 106 / WSi ₂ film 104A / polysilicon 103 structure.

As a result, the present invention is to form a structure of the gate electrode with improved interface resistance characteristics.

It is possible to omit the mask insulating film according to the device applied in the embodiment of the present invention.

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

The present invention can implement a low resistance gate by improving the interfacial characteristics when forming a gate of a polysilicon and tungsten laminate structure, thereby realizing a high-speed, highly integrated device.

Claims (7)

Sequentially stacking a gate insulating film, a polysilicon film, a tungsten-rich WSi _x film, a diffusion barrier film, a tungsten film, and a mask insulating film on a semiconductor substrate; Patterning the stacked films by a gate mask and an etching process: and Selective oxidation is performed to selectively oxidize the polysilicon film without oxidation of the tungsten film, thereby reacting the tungsten-rich WSi _x film with the polysilicon film to form a tungsten silicide film at an interface between the tungsten film and the polysilicon film. Steps to Gate forming method of a semiconductor device comprising a. The method of claim 1, And the tungsten-rich WSi _x film is formed to a thickness of 20 to 100 GPa and has a thickness of 1.0 &lt; x &lt; 2.0. The method of claim 1, And the tungsten-rich WSi _x film is formed by depositing in-situ without vacuum destruction after deposition of the polysilicon film. The method of claim 1, The selective oxidation is performed at 700 to 1100 ° C. in a H ₂ O / H ₂ atmosphere. The method of claim 1, The diffusion barrier is a gate forming method of a semiconductor device, characterized in that the conductive material is tungsten nitride. The method of claim 4, wherein The selective oxidation is a gate manufacturing method of a semiconductor device, characterized in that carried out for 30 seconds to 2 hours at 0.01 ≦ H ₂ O / H ₂ ≦ 0.5. The method of claim 4, wherein The mask insulating film is a gate manufacturing method of the semiconductor device, characterized in that deposited for 30 seconds to 2 hours at 800 ℃ or less.