JP2776838B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for manufacturing a semiconductor device, and more particularly to a technology effective when applied to formation of an insulating film constituting a semiconductor integrated circuit.

[Conventional technology]

The technology for forming a silicon nitride film used as an insulating material of a semiconductor integrated circuit is described in, for example, Science Forum Inc., published on November 28, 1983, "Super LSI Handbook", pp. 101-102.

Examples of an insulating film included in a semiconductor integrated circuit include a gate insulating film, an insulating film for element isolation, an interlayer insulating film, a passivation film, and the like. These insulating film materials mainly include SiO ₂
And Si ₃ N ₄ are used.

For example, the gate insulating film of a MOS-FET is an SiO ₂ film obtained by thermally oxidizing the surface of a silicon substrate, a Si ₃ N ₄ film obtained by directly nitriding the surface of a silicon substrate, or a Si film using a CVD method. It is constituted by such as ₃ N ₄ film.

In the manufacturing process of a MOS type semiconductor device, the ability to form a high-quality gate insulating film is the most important factor in determining device performance, and the gate insulating film must be thin ( Various characteristics are required, such as that the film quality is uniform and free of defects, and that the electrical characteristics of the film do not deteriorate due to aging.

[Problems to be solved by the invention]

However, according to the study of the present inventor, there is a problem that it is difficult to obtain a high quality silicon oxide film or silicon nitride film by the conventional insulating film forming technology.

In other words, in conventional insulating film forming methods such as thermal oxidation, direct nitridation, and CVD, since the silicon substrate is exposed to high temperatures during film formation, damage to the integrated circuit element due to heat may cause variations in impurity profiles and the like. Is inevitable.

In particular, as the thickness of the gate insulating film becomes 10 nm or less with the miniaturization of integrated circuits, the influence of the natural oxide film formed on the surface of the gate insulating film cannot be ignored, and the film quality and film It becomes difficult to control the thickness.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a technique capable of forming a high-quality insulating film.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[Means for solving the problem]

The outline of a representative invention among the inventions disclosed in the present application will be briefly described as follows.

That is, the method of manufacturing a semiconductor device according to claim 1 is
By irradiating the surface of the insulating film deposited on the surface of the semiconductor substrate with first light in a vacuum atmosphere to activate the surface of the insulating film, nitrogen or a nitrogen compound is added to the surface of the insulating film. By supplying a reaction gas consisting of, by irradiating the second light that decomposes the reaction gas,
A second insulating film made of a nitrogen compound is formed on the surface of the insulating film.

According to a second aspect of the present invention, in the method of manufacturing a semiconductor device, the surface of the insulating film attached to the surface of the semiconductor substrate is irradiated with first light in a vacuum atmosphere to decompose and remove the insulating film. After exposing the substrate, a reaction gas comprising nitrogen or a nitrogen compound is supplied to the surface of the substrate,
By irradiating a second light for decomposing the reaction gas, a second insulating film made of a nitrogen compound is formed on the surface of the base.

[Action]

According to the above-described means, since a film is formed by a radical reaction using light energy, a high-quality insulating film can be obtained.

Further, since the formation of the insulating film is performed at a low temperature, damage to the semiconductor substrate and variation in the impurity profile can be suppressed.

Embodiment 1 FIGS. 1A to 1C are cross-sectional views of a main part of a semiconductor substrate showing a method for manufacturing a semiconductor device according to an embodiment of the present invention.

As shown in FIG. 1A, a field insulating film 2 is formed on a surface of a semiconductor substrate (hereinafter, referred to as a substrate) 1 made of a p-type or n-type silicon single crystal by a LOCOS method (selective oxidation method). The surface of the active element region surrounded by the field insulating film 2 is formed by a wet oxidation method or the like.
An extremely thin SiO ₂ film 3 of about 20 nm is formed.

Therefore, as shown in FIG. 1B, first, a region other than the active element region is covered with a photoresist mask 4, and then,
Light (hν ₁ ) is irradiated to the surface of the SiO ₂ film 3 from above the substrate 1 in a vacuum atmosphere at room temperature.

The wavelength of this light is equal to or higher than the Si—O bond energy (3 to 7 eV) of the SiO ₂ film 3, and the light source is, for example, a low-pressure mercury lamp or laser light.

By this light irradiation, a part of the Si—O bond of the SiO ₂ film 3 is cut to generate dangling bonds, and the vicinity of the surface of the SiO ₂ film 3 is activated.

At this time, since the light acts only on the surface layer of the substrate 1, the inside of the substrate 1 is hardly damaged.

Next, a reaction gas composed of N ₂ or NH ₃ is supplied to the surface of the substrate 1, and light (hν ₂ ) for decomposing the reaction gas is irradiated from above the substrate 1.

Then, the reaction gas is radicalized by this light irradiation, and an extremely thin SiO _x N is formed on the surface of the activated SiO ₂ film 3.
_{A y} (silicon oxynitride) film 5 is formed, and as a result, a thin gate insulating film 6 having a two-layer structure of the SiO ₂ film 3 and the SiO _x N _y film 5 is obtained (FIG. 1C). .

In addition, since the film forming process on the surface of the SiO ₂ film 3 is a reaction rate-determining system, the obtained SiO _x N _y film 5 is an insulating film with extremely high uniformity.

As described above, according to the first embodiment, the gate insulating film 6 having a high dielectric constant and a high withstand voltage can be obtained.
In addition, when the SiO _x N _y film 5 is formed, damage to the substrate 1 due to heat and variation in impurity profiles are small, so that the MOS _x
-The reliability of the FET can be improved.

Embodiment 2 FIGS. 2A to 2C are cross-sectional views of a main part of a semiconductor substrate showing a method of manufacturing a semiconductor device according to another embodiment of the present invention.

As shown in FIG. 2A, a field insulating film 2 is formed on the surface of a substrate 1 made of a p-type or n-type silicon single crystal by a LOCOS method (selective oxidation method). In the upper layer, a plate electrode 7 constituting a capacitor of the MOS type memory is formed. The plate electrode 7 is obtained by adding impurities such as phosphorus (P) or arsenic (As) to polysilicon deposited by the CVD method, and thereafter performing annealing to reduce the resistance.

On the surface of the plate electrode 7 thus obtained,
An extremely thin native oxide film 8 of about 20 to 50 ° is formed.
When the natural oxide film 8 is formed, it is difficult to control the film quality and thickness of the plate electrode 7. Therefore, in order to obtain a high quality plate electrode 7, it is necessary to remove the natural oxide film 8. .

Therefore, as shown in FIG. 2 (b), high energy is selectively applied to the surface of the plate electrode 7 in a vacuum atmosphere at room temperature.
By irradiating a high-power laser beam (hν ₃ ),
The natural oxide film 8 is decomposed and removed to expose the polysilicon constituting the plate electrode 7.

At this time, since the light acts only on the surface layer of the substrate 1, the inside of the substrate 1 is hardly damaged.

Next, a reaction gas composed of N ₂ or NH ₃ is supplied to the surface of the substrate 1 and light (hν) for decomposing the reaction gas is supplied.
₄ ) Irradiate. Then, by this light irradiation, N ₂ or NH ₃ is radicalized, and an extremely thin SiN _X film 9 is formed on the surface of the plate electrode 7 (FIG. 2C).

Since the film formation reaction of the SiN _X film 9 is a reaction-limiting system, the obtained SiN _X film 9 is an insulating film having extremely high uniformity.

As described above, according to the second embodiment, a high-quality plate electrode 7 having no native oxide film 8 on the surface can be obtained. Further, when the SiN _x film 9 is formed, damage to the substrate 1 due to heat, Since the variation in the impurity profile is small, the reliability of the MOS semiconductor device can be improved.

As described above, the invention made by the inventor has been specifically described based on the embodiments. However, the present invention is not limited to the first and second embodiments, and can be variously modified without departing from the gist thereof. Needless to say, there is.

For example, in the first and second embodiments, the case where the present invention is applied to the insulating film forming the MOS integrated circuit has been described. However, it is needless to say that the present invention can be applied to the insulating film forming the bipolar integrated circuit.

〔The invention's effect〕

The effect obtained by the representative one of the inventions disclosed in the present application will be briefly described as follows.

(1). By irradiating the surface of the insulating film attached to the surface of the substrate with the first light in a vacuum atmosphere to activate the surface of the insulating film, the surface of the insulating film is formed from nitrogen or a nitrogen compound. 2. The semiconductor device according to claim 1, wherein a second insulating film made of a nitrogen compound is formed on a surface of the insulating film by irradiating a second light for decomposing the reactive gas while supplying the reactive gas. According to the manufacturing method, a high-quality insulating film can be formed without damaging the semiconductor substrate or causing a variation in the impurity profile.

(2). Also, by irradiating the surface of the insulating film deposited on the surface of the substrate with the first light in a vacuum atmosphere,
After decomposing and removing the insulating film to expose the underlayer, supplying a reaction gas composed of nitrogen or a nitrogen compound to the surface of the underlayer and irradiating a second light for decomposing the reaction gas to thereby form the underlayer. According to the method of manufacturing a semiconductor device according to claim 2, wherein the second insulating film made of a nitrogen compound is formed on the surface of the semiconductor device, high quality can be obtained without damaging the semiconductor substrate or causing variation in the impurity profile. Can be formed.

[Brief description of the drawings]

1A to 1C are cross-sectional views of a main part of a semiconductor substrate showing a method for manufacturing a semiconductor device according to an embodiment of the present invention. FIGS. 2A to 2C are diagrams of the present invention. FIG. 13 is a cross-sectional view of a principal part of a semiconductor substrate, illustrating a method of manufacturing a semiconductor device according to another embodiment. 1 ... semiconductor substrate, 2 ... field insulating film, 3 ... Si
O ₂ film, 4 ... photoresist mask, 5 ... SiO _x N _y film, 6
...... gate insulating film, 7 ...... plate electrode, 8 ...... natural oxide film, 9 ...... SiN _X film, hν ₁ ~hν ₄ ...... light.

Claims (2)

(57) [Claims] 1. A surface of an insulating film formed on a main surface of a semiconductor substrate is activated by irradiating the surface of the insulating film with first light in a vacuum atmosphere. Supplying a reaction gas composed of nitrogen or a nitrogen compound to the substrate, and irradiating a second light for decomposing the reaction gas to form a second insulation film composed of a nitrogen compound on the surface of the insulation film. A method for manufacturing a semiconductor device, comprising: 2. The method according to claim 1, further comprising: irradiating the surface of the insulating film formed on the main surface of the semiconductor substrate with first light in a vacuum atmosphere to decompose and remove the insulating film to expose a base. By supplying a reaction gas made of nitrogen or a nitrogen compound to the surface of the base and irradiating a second light for decomposing the reaction gas, a second insulating film made of a nitrogen compound is formed on the surface of the base. A method for manufacturing a semiconductor device, comprising the steps of: