JP3090561B2 - Semiconductor device thin film forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma enhanced CVD (Plasma Enhancement) for forming a thin film on a sample surface such as a semiconductor substrate.
The present invention relates to a method for forming a thin film of a semiconductor device to which the (dCVD) method is applied.

[0002]

2. Description of the Related Art Conventionally, in order to form a thin film on a sample surface such as a semiconductor substrate, a plasma-enhanced CVD (hereinafter referred to as PECV) has been proposed.
A plasma is generated in a reaction vessel of the apparatus, and a reaction gas introduced into the reaction vessel is activated by using plasma discharge energy, and a deposit generated by chemical vapor deposition of the reaction gas is generated. The plasma-excited CVD method for promoting the deposition on the sample surface is widely applied.

Here, as a reaction gas, for example, Si is used to deposit a SiO ₂ thin film on the surface of a semiconductor substrate.
An H ₄ -based gas (silane-based gas) or a TEOS (tetraethyl orthosilicate) -based gas is used.

[0004]

By the way, with the demand for realizing a further high-density semiconductor integrated device (VLSI) in recent years, the development of a submicron miniaturization generation technology has become extremely important. Therefore, by experimentally verifying the shape of a thin film formed by the conventional plasma-excited CVD method, the applicability of the conventional technology to submicronization was examined.

FIGS. 4 (a) to 4 (f) show 13.5 between counter electrodes provided in a reaction vessel of the PECVD apparatus.
Plasma is generated by applying a high-frequency power such as 6 MHz, and Al wiring formed on the SiO ₂ oxide film on the surface of the semiconductor substrate and on the surface by introducing a SiH ₄ -based reaction gas into the reaction vessel. The vertical cross-sectional shape when an SiO ₂ thin film for insulating coating is formed is shown above. The figure is a trace of a micrograph.

[0006] As is apparent from the above experimental results, Si
Since the O ₂ thin film has a rounded shape with a convex side surface and has a poor embedding ability such that the base is hollowed out from the head, a void (gap) is formed near the bottom of the Al wiring. There is a problem that occurs. In particular, a very serious problem is caused in a high-density wiring at a submicron where the gap between the Al wirings is small (see FIGS. 4E and 4F).

FIGS. 5 (a) to 5 (f) show 13.5 between counter electrodes provided in a reaction vessel of the PECVD apparatus.
Plasma is generated in the reaction vessel by applying a high-frequency power of 6 MHz, and a TEOS-based gas is introduced into the reaction vessel, thereby forming SiO _{2 on the} surface of the semiconductor substrate.
The experimental results (longitudinal sectional view) when an SiO ₂ thin film for insulating coating is further formed on the oxide film and the Al wiring formed on the surface thereof are shown. FIG. 5 also shows a trace of a micrograph.

According to the results of this experiment, FIG.
As is apparent from FIG. 4F, the shape of the side wall portion of the formed SiO ₂ thin film is not round as compared with the case of FIGS. 4A to 4F, and as a result, the generation of voids is reduced. It was realized. Therefore, it can be said that the technique has greatly contributed to the improvement of the controllability of the generated thin film.

As described above, the use of a TEOS-based gas is more suitable for forming a high-density thin film than the use of a SiH ₄ -based reaction gas, but as shown in FIGS. In order to form a denser thin film at a submicron where the distance between Al wirings is narrower, the burying ability is not sufficiently exhibited.
Even if an S-based gas is applied, it is difficult to meet the demand for higher density.

[0010] Further, in order to improve the film formation shape and the embedding characteristics, a normal pressure CV using an O ₃ -TEOS-based gas is used.
Although the technique by the D method is known, the oxide thin film formed by this manufacturing technique has a high hygroscopicity, and thus has a problem that the moisture resistance of a finally manufactured semiconductor integrated device is reduced.

The present invention has been made in view of such problems of the conventional PECVD method, and provides a method of forming a thin film of a semiconductor device which can cope with higher density and higher reliability. The purpose is to:

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method of generating plasma in a reaction vessel by using a single-frequency high-frequency power, and converting a reaction gas introduced into the reaction vessel into a plasma discharge energy. In the method for forming a thin film of a semiconductor device, wherein a deposit generated by chemical vapor deposition of the reaction gas is applied to a sample surface by activating the reaction gas, a TEOS-based gas and a halogen-based gas are used as the reaction gas. By introducing a mixed gas with the above into the reaction vessel, halogen atoms are taken in and the deposit having a low dielectric constant is deposited on the sample surface. The halogen-based gas is a halogen-based gas having a saturated carbon skeleton, and includes CF ₄ , CHF ₃ , and C ₄ .
_{2 F 6, CCl 4, CCl} 2 F 2, applied to any one of the gas of C ₃ F _8. Further, the halogen-based gas includes F ₂ ,
Cl ₂ , NF ₃ , SF ₆ , SiF ₄ , SiCl ₄ , ClF ₃ ,
Any one gas of BCl ₃ , HCl, HBr, and HF is applied.

[0013] As the halogen-based gas having a saturated carbon backbone, to apply the _C 2 _{F 6,} also, as the halogen-containing _{gas, F 2, Cl 2, NF} 3, SF 6, Si
F ₄ , SiCl ₄ , ClF ₃ , BCl ₃ , HCl, HB
Any one of r and HF is applied.

[0014]

As described above, in the PECVD method in which plasma is generated in a reaction vessel by high frequency power of a single frequency, a mixed gas of the TEOS-based gas and a halogen-based gas having a saturated carbon skeleton is applied to the reaction gas. When a thin film is formed on the surface of an uneven base material, voids do not occur because the side walls of the thin film are formed in a forward tapered shape. Furthermore, when the present invention is applied to the manufacture of a semiconductor device having high-density wiring or the like, voids do not occur because the entire thin film is sufficiently buried in the concave portions of the uneven base material. Further, since the denseness of the side wall of the thin film is improved, it is possible to provide a method excellent in film formation controllability. Further, since fluorine is taken into the thin film to form a thin film having a low dielectric constant, it is possible to improve the electrical characteristics of the transistor and the like. Compared with a thin film formed by an atmospheric pressure CVD method using an O ₃ -TEOS-based gas, the same or abnormal ability is obtained with respect to the film forming shape and the embedding property, and the moisture absorbing property is much higher. An excellent (that is, extremely low hygroscopic) thin film can be formed.

[0015]

An embodiment of the present invention will be described below with reference to the drawings. First, based on FIG. 1, the PE applied to this embodiment will be described.
The general configuration of the CVD apparatus will be described. Counter electrodes 3 and 4 are accommodated in an insulated reaction vessel 2 for realizing a reaction chamber 1 sealed from the outside air, and one electrode 4 is maintained at a ground potential. At the same time, a semiconductor substrate 5 for forming a thin film is attached to the opposite surface, and high-frequency power output from a high-frequency oscillation source 8 for generating plasma is applied to the other electrode 3 via an impedance matching circuit 9. ing. Further, a reaction gas is introduced from above the electrode 3 into the reaction chamber 1 via the pipe 6, and an unnecessary portion of the reaction gas is exhausted from one side of the reaction vessel 2. A heater 7 for controlling temperature is provided on the electrode 4 side.
The frequency of the high frequency power is 13.56 MHz, for example.
Is set to

In the PECVD apparatus having such a configuration, a mixed gas of a halogen-based gas having a saturated carbon skeleton and a TEOS-based gas is introduced into the reaction chamber 1 as the above-mentioned reaction gas, and the reaction gas is supplied by high-frequency power from a high-frequency oscillation source 8. By activating the mixed gas with the plasma discharge energy generated between the counter electrodes 3 and 4, Si
An O ₂ thin film is generated. The halogen-based gas having a saturated carbon skeleton includes, for example, CF ₄ , CHF ₃ , C
_{2 F 6, CCl 4, CCl} 2 F 2, applied to any one kind of gas such as C ₃ F _8.

FIGS. 2 (a) to 2 (f) show the SiO ₂ oxide film on the semiconductor substrate surface and the Al wiring formed on the surface by the thin film forming method according to the present invention and the SiO ₂ oxide film for insulating coating. ₂ shows a longitudinal sectional shape when _two thin films are formed. The figure is a cross-sectional view showing the outline of the micrograph of the vertical cross-sectional shape by tracing, and the vertical and horizontal lengths are as indicated by the unit scale (0.5 μm) in the figure.

As shown in FIGS.
If the width and relative spacing of the wiring are relatively large, SiO
_{(2) Since} the side wall of the thin film is formed in a forward tapered shape, generation of voids is eliminated.

On the other hand, as shown in FIG. 1E, even when the width and relative interval of each Al wiring are in the submicron range, the sidewall shape of the SiO ₂ thin film becomes flat, so that voids are generated. It is greatly reduced. Further, as shown in FIG. 3F, when the width and the relative spacing of each Al wiring are further reduced in the submicron range, the recesses between the Al wirings also have S
The iO ₂ thin film is buried, and the problem of void generation is completely eliminated. That is, the effect of forming a thin film having excellent embedding characteristics can be obtained. Further, in these cases shown in FIGS. 7E and 7F, since the side wall portion of the thin film has a dense composition structure, the quality is improved.

Incidentally, the reason why the voids are reduced and the side wall portion of the SiO ₂ thin film is formed in a tapered shape is as follows.
At the same time as deposits are deposited on the upper surface of the Al wiring and the SiO ₂ oxide film based on the TEOS-based gas, the deposits (SiO ₂
It is presumed that the thin film is isotropically etched. Further, since the SiO ₂ thin film incorporates fluorine, its dielectric constant is lowered, and the Al wiring is made of MOSFE.
In the case where it is applied as an inter-gate wiring for connecting between the gate electrode of T and the like, an electrically good MO
An SFET can be realized. Furthermore, O _3, which is conventionally considered to be capable of realizing good thin film formation,
-Forming a thin film that exhibits the same or better performance with respect to the film forming shape and embedding characteristics and has extremely low hygroscopicity even when compared with a thin film formed by a normal pressure CVD method using a TEOS-based gas. Can be.

In this embodiment, as the reaction gas,
Although the case where a mixed gas of a halogen-based gas having a saturated carbon skeleton and a TEOS-based gas is applied has been described, similar effects can be obtained by using a mixed gas of another halogen-based gas and a TEOS-based gas. In this case, as the halogen-based gas, for example, F ₂ , Cl ₂ , NF ₃ , SF ₆ , Si
F ₄ , SiCl ₄ , ClF ₃ , BCl ₃ , HCl, HB
Any one kind of gas such as r and HF is applied.

Further, similarly, when the present invention is applied to an ECR plasma CVD apparatus, a SiO ₂ thin film having an excellent film formation shape and excellent burying characteristics can be produced. In this case, for example, the ECR plasma C schematically shown in FIG.
2.45G via the waveguide to the plasma generation chamber of the VD device
Hz microwaves are introduced, nitrogen (N ₂ ) or the like is introduced as a plasma generation gas, and the above-mentioned mixed gas (that is, a halogen-based gas having a saturated carbon skeleton and a TEOS-based gas is used as a reaction gas). Or a mixed gas of a halogen-based gas and a TEOS-based gas) is introduced into the reaction chamber.

[0023]

As described above, according to the present invention, plasma is generated in a reaction vessel by high frequency power of a single frequency, and a reaction gas introduced into the reaction vessel is activated using plasma discharge energy. In the method of forming a thin film for a semiconductor device, wherein a deposit generated by chemical vapor deposition of a reactive gas is applied to a sample surface, the reactive gas includes a halogen-based gas having a saturated carbon skeleton and a TEOS-based gas. Or a mixed gas of a halogen-based gas and a TEOS-based gas, so that even if a thin film is formed on the surface of an uneven base material, the side wall of the thin film is formed in a forward tapered shape. No voids occur. For example, when the present invention is applied to the manufacture of a semiconductor integrated circuit device having an extremely high wiring density or inter-element density, a thin film having a recess between the wirings or between the elements is sufficiently buried, so that voids are formed. Excellent embedding characteristics can be obtained without generation.
Further, since the denseness of the side wall of the thin film is improved, it is possible to provide a method excellent in film quality controllability. Furthermore,
Fluorine is taken into the thin film to form a thin film having a low dielectric constant, and it is easy to control the quality of the formed film, for example, to form a thin film having extremely low hygroscopicity. Excellent effects such as improvement of characteristics can be obtained.

As described above, since a thin film having an excellent film-forming shape and an excellent embedding property can be formed, a method for forming a thin film of a semiconductor device which can cope with the realization of a further high-density and highly integrated semiconductor device is provided. be able to.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a schematic configuration of a PECVD apparatus for explaining one embodiment of a method for forming a thin film of a semiconductor device according to the present invention.

FIG. 2 is a longitudinal sectional view showing a shape of a SiO ₂ thin film generated by the PECVD apparatus shown in FIG.

FIG. 3 is an explanatory diagram for explaining an embodiment of the present invention when an ECR plasma CVD apparatus is applied.

FIG. 4 is a longitudinal sectional view showing a shape of a SiO ₂ thin film generated by a conventional PECVD method using a SiN-based gas.

FIG. 5 is a longitudinal sectional view showing a shape of a SiO ₂ thin film produced by a conventional PECVD method using a TOES-based gas.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reaction chamber, 2 ... Reaction container, 3, 4 ... Counter electrode, 5 ... Semiconductor substrate, 6 ... Piping, 7 ... Heater, 8 ... High frequency power supply,
9 ... Impedance matching circuit.

Continuing on the front page (72) Inventor Shinsuke Mizuno 14-3 Shinsen, Narumi, Narita-shi, Chiba Applied Materials Japan Co., Ltd. (72) Inventor Katsuyuki Rokuhei 14-3 Shinsen, Narumi-shi, Narita-shi, Chiba Applied Materials Japan Co., Ltd.

Claims (3)

(57) [Claims] A plasma is generated in a reaction vessel by high frequency power of a single frequency, and a reaction gas introduced into the reaction vessel is activated by using plasma discharge energy, whereby a chemical gas of the reaction gas is generated. In the method for forming a thin film of a semiconductor device, wherein a deposit generated by phase growth is deposited on a sample surface, by introducing a mixed gas of a TEOS-based gas and a fluorine-based gas into the reaction vessel as the reaction gas, A method of forming a thin film for a semiconductor device, comprising: depositing the deposit having a low dielectric constant by incorporating fluorine atoms onto the sample surface, and forming a SiOF film. 2. The fluorinated gas is CF ₄ , CHF ₃ ,
_{2. The} method according to claim 1, wherein the method is one of CCl ₂ F ₂ and C ₃ F ₈ . 3. The fluorine-based gas includes F ₂ , NF ₃ and SF.
_{6. The} method for forming a thin film of a semiconductor device according to claim 1, wherein the method is any one of SiF ₄ , ClF ₃ , and HF.