JP3522738B2 - Metal thin film formation method by chemical vapor deposition - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a metal thin film by chemical vapor deposition for forming a metal thin film on a substrate during the manufacture of semiconductor devices, and more particularly to a chemical vapor deposition method using an excited gas. The present invention relates to a method for forming a metal thin film by phase growth.

[0002]

2. Description of the Related Art As semiconductor devices have been highly integrated, the diameters of contact holes and through holes formed in an insulating film have been extremely miniaturized. As a technique for filling the stepped portion of such a fine pattern, for example, filling a contact hole or a through hole in an insulating film on a substrate with a refractory metal or the like, a chemical vapor deposition method (hereinafter, referred to as CVD
Are called effective).

In the conventional CVD in which a metal thin film is deposited on a substrate to fill a stepped portion, a fluoride such as tungsten or molybdenum is used as a source gas, and the metal fluoride is used as a reactive gas, hydrogen. It is introduced into a CVD apparatus as a mixed gas with a silane-based gas, and while this reactive gas is excited by plasma, ultraviolet rays, etc., a reduction reaction of this raw material gas and the reactive gas is performed on the substrate to deposit a metal thin film. (JP-A-63-65075 and JP-A-64-233).

However, the formation of the metal thin film on the substrate by the chemical vapor deposition method is almost determined by the selection of the source gas and the reactive gas, and depends on the reaction process of the selected source gas and the reactive gas. As a result, an etching reaction of the wafer substrate and the deposited metal thin film occurs. For example, in forming a tungsten thin film on a substrate, a reduction reaction for reducing tungsten fluoride to metallic tungsten is performed by reducing trifluorosilane (SiHF3) in addition to metallic tungsten to be deposited on a substrate by reduction as a final product. ) Is generated as the reaction most likely to proceed. Therefore, when hydrogen is used as the reactive gas, a reaction temperature of about 400 to 500 ° C. is required. At this reaction temperature, the etching reaction of the silicon substrate is promoted, or the surface of the formed metal thin film becomes rough. Or

[0005]

As described above, when hydrogen is used as a reactive gas, a high temperature is required for the reaction, so that the surface is roughened or the substrate is eroded, which causes leakage current. It is also a cause of thin film peeling.

Therefore, an object of the present invention is to provide a method for forming a metal thin film by a chemical vapor deposition method in which corrosion of a substrate is prevented, leakage current is suppressed, and flatness of a film surface is improved.

[0007]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a semiconductor having a step portion by a chemical vapor deposition method.
In a method of forming a metal thin film on a body device substrate,
Place the semiconductor device substrate in the reaction chamber, and
A step of maintaining the temperature below 400 ° C. and exhausting the reaction chamber
Process and source gas containing halide in the reaction chamber
Introducing step, and adsorbing the source gas on the gas
And the step of evacuating by interrupting the introduction of the raw material gas
And introducing a reactive gas into the discharge tube connected to the reaction chamber.
And the step of exciting and by the excited reactive gas
The raw material gas adsorbed on the semiconductor device substrate is
And forming a thin film on the substrate by the reaction
A step of interrupting the introduction of the volatile gas and exhausting the gas, the method for forming a metal thin film by a chemical vapor deposition method. Further, according to the present invention, a plurality of gases are alternately placed in a semiconductor device.
Chemistry for forming a metal thin film by introducing it on a vice substrate
A method for vapor phase growth, comprising:
Step of keeping device substrate from room temperature to less than 400 ° C
And evacuating the reaction chamber, including a halide
Introducing a first source gas into the reaction chamber;
Adsorbing a first source gas onto the gas, and
A step of interrupting the introduction of the first source gas and exhausting the gas;
Excitation by introducing a second gas into the discharge tube connected to the reaction chamber
And a step of using the excited second gas
Reacting the first source gas adsorbed on the body device substrate
Forming a thin film on the semiconductor device substrate
And interrupting the introduction of the second gas and exhausting the gas,
By a chemical vapor deposition method characterized by having
This is a thin film forming method.

[0008]

According to the present invention, when a metal thin film is formed on a substrate such as a semiconductor device substrate by a chemical vapor deposition method, a source gas and a reactive gas excited by an exciting means are alternately introduced onto the substrate. The raw material gas adsorbed on the substrate by introducing the raw material gas is reacted with the excited reactive gas introduced to form a metal thin film, and this step is repeated to form a metal thin film of a desired thickness on the substrate. To form.

Particularly, in the present invention, when the reactive gas is introduced,
By exciting the reactive gas by an appropriate excitation means and introducing it as an excited species such as a hydrogen radical on the substrate,
The reaction temperature can be lowered and the metal thin film can be formed in a shorter time.

This is because, for example, hydrogen gas is used as a reactive gas, and is excited by plasma formed by electron cyclotron resonance or by ultraviolet rays, for example, is introduced as an excited species of hydrogen radicals, and is adsorbed on the substrate surface, for example, hexafluoride. The source gas of tungsten reacts with each other to form thin film metal tungsten. In this case, the substrate temperature affects only the adsorbed state of the raw material gas and does not affect the reaction itself, so that the substrate temperature becomes lower than when the reactive gas is not excited. Since the substrate temperature is low, the erosion of the substrate such as the silicon substrate by the source gas and the roughening of the film surface are further prevented.

The substrate used in the present invention is a wafer substrate of silicon or compound semiconductor for manufacturing semiconductor integrated circuits,
Substrates such as glass substrates used for liquid crystal display devices and plasma display devices and substrates for manufacturing other semiconductor devices, especially substrates having an insulating film on the surface thereof, particularly those having stepped portions such as contact holes and through holes Therefore, it is necessary to embed the stepped portion with metal.

The source gas used in the present invention is a metal halide such as tungsten hexafluoride, titanium tetrachloride and an organic metal compound such as trimethylaluminum and triethylaluminum. The reactive gas used in the present invention is a gas capable of reacting with the above-mentioned raw material gas, and examples thereof include hydrogen, hydrazine, phosphine, and diborane.

The substrate temperature (CVD process temperature) in the present invention is a constant temperature from room temperature to less than 400.degree.

That is, in the present invention, since a constant substrate temperature selected from the above range is used throughout the entire CVD process, it is necessary to perform a heat cycle (a plurality of times) for heating and cooling the substrate to change the substrate temperature. There is no. Therefore, the CVD process time is shortened. Particularly, since the excitation means is used, the CVD process time can be shortened as compared with the case where this is not used.

In the present invention, since the raw material gas and the reactive gas are introduced alternately, erosion of the substrate and roughening of the film surface due to the raw material gas are prevented.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Reference Example 1 First, an example of forming a metal thin film by a chemical vapor deposition method by alternately introducing a raw material gas and a non-excited reactive gas, which are the premise of the present invention, will be described.

Source gas using the CVD apparatus shown in FIG.
Tungsten hexafluoride (WF ₆) And reactive gas
Hydrogen gas (H₂) And on the semiconductor device substrate,
Introduced alternately with the time interval and gas flow rate shown in Fig.
A tungsten film was formed.

That is, the pressure control device 8 is provided inside the CVD chamber 4.
After reducing the pressure to several tens of Torr by the vacuum pump 5,
As a raw material gas 6, tungsten hexafluoride (WF ₆ ) was introduced into the CVD chamber 4 through the gas flow rate control device 2a from the gas inlet 1 as shown in FIG. 3A. At this time, CV
The inside of the D chamber 4 and the semiconductor device substrate 9 were heated and held at 400 ° C. constantly.

The raw material gas (WF ₆ ) is adsorbed on the semiconductor device substrate 9 in a layer thickness of 3 to 5 molecules (WFx), and then the supply of the raw material gas is interrupted as shown in FIG. Hydrogen (H ₂ ) as gas flow controller ₂ b
It is introduced into the CVD chamber 4 via. The raw material (WFx) adsorbed on the semiconductor device substrate 9 was reduced by hydrogen gas (H2) to deposit a thin film of tungsten (W) on the semiconductor device substrate 9 (FIG. 3C).

Thereafter, the source gas and the reactive gas are alternately supplied at the time intervals and the gas flow rates shown in FIG. 2 so that the metal thin film can be formed on the semiconductor device substrate 9 to have a desired thickness. ) Thin film was formed.

A conventional mixed gas of tungsten hexafluoride (WF ₆ ) and hydrogen gas (H ₂ ), and tungsten hexafluoride (WF ₆ ) and silicon tetrahydride (S) as a reactive gas.
Table 1 below shows the substrate temperature and physical properties when a tungsten thin film is formed on the same substrate by CVD using a mixed gas of iH ₄ ) and when the film is formed by the method of Reference Example 1 .

[0023]

[Table 1]

In Table 1, the step coverage is the ratio of the film thickness a of the film formed on the plane to the film thickness b of the film formed on the bottom of the hole.
It is expressed by b / a × 100%, and the closer to 100% the better. The surface roughness is evaluated from the surface reflectance, and ◎ indicates that the surface state is substantially the mirror surface and is excellent, and ○ indicates that the surface state is close to the mirror surface and good, and the Δ mark Indicates that the surface condition is far from the mirror surface and is defective.

It can be seen from Table 1 above that by alternately and discontinuously supplying the raw material gas and the reactive gas, a metal thin film having no surface erosion and excellent surface flatness is formed. .

Example 1 As shown in FIG. 4, a CVD apparatus equipped with an RF induction plasma as an excitation means was used, and tungsten hexafluoride (WF ₆ ) was used as a source gas, and hydrogen gas (H ₂ was used as a reactive gas). 2) and (4) are alternately and discontinuously introduced on the semiconductor device substrate 9 at time intervals and gas flow rates similar to those of FIG. 2 to form a metal tungsten film.

That is, the inside of the discharge tube 3 together with the inside of the CVD chamber 4 is passed through the pressure control device 8 and the vacuum pump 5 to several tens Torr.
After the pressure is reduced to 2, tungsten hexafluoride (WF ₆ ) as a source gas 6 is introduced into the discharge tube 3 through the gas flow rate control device 2a from the gas introduction port. At this time, the temperature in the reaction chamber 4 and the semiconductor device substrate 9 was heated to 300 ° C. or lower.

On the semiconductor device substrate 9, the source gas (WF
₆ ) is adsorbed with a layer thickness of 3 to 5 molecules (WFx). Then, the supply of the raw material gas is interrupted, and hydrogen (H ₂ ) as the reactive gas 7 is introduced into the discharge tube 3 via the gas flow rate control device 2b. Then, a high frequency is introduced by the high frequency generator 10 to form plasma in the discharge tube 3, and the H ₂ gas is excited (H) and supplied onto the substrate. The raw material (WFx) adsorbed on the semiconductor device substrate 9 was reduced by excitation H to deposit a thin film of tungsten (W) on the semiconductor device substrate 9.

Thereafter, a thin film of tungsten (W) was formed by alternately repeating the supply of the source gas and the reactive gas so that the thin metal film could be formed to a desired thickness. At this time, argon gas or the like can be added to stabilize the discharge.

A metal tungsten thin film having the same characteristics as in Reference Example 1 was obtained by the above process. By using the RF induction plasma as the means for exciting the reactive gas, it was possible to use a lower substrate temperature than when the exciting means was not used, and the CVD process time could be shortened.

Example 2 As shown in FIG. 5, using a CVD apparatus equipped with electron cyclotron resonance as an excitation means, a metal tungsten film was formed on the semiconductor device substrate 9 by CVD in the same manner as in Example 2. .

That is, instead of the RF induction discharge tube used in Example 1, an electron cyclotron resonance discharge tube 14 composed of a microwave oscillator 13 and an electromagnet 12 is used, and tungsten hexafluoride (WF ₆ ) as a source gas 6 is used. ₂ and hydrogen gas (H ₂ ) which is the reactive gas 7 are alternately introduced at the same time intervals as shown in FIG. 2, and the hydrogen (H ₂ ) gas is excited to generate excited species (H) by electron cyclotron resonance discharge. A metal tungsten thin film having the same characteristics as in Reference Example 1 was obtained in the same manner as in Example 2. At this time, argon gas or the like may be added to stabilize the discharge.

By using electron cyclotron resonance as the means for exciting the reactive gas, it is possible to use a lower substrate temperature than when no means for exciting is used, and moreover, CV
D Process time could be shortened.

Reference Example 2 As shown in FIG. 6, a metal tungsten film is deposited on the semiconductor device substrate 9 by CVD in the same manner as in Example 1 using a CVD apparatus using photoexcitation using ultraviolet rays as excitation means. Formed.

That is, instead of the RF induction discharge tube used in Example 1, an ultraviolet lamp 15 is installed on the semiconductor device substrate 9, and it reacts with tungsten hexafluoride (WF ₆ ) which is the source gas 6. Alternate introduction of hydrogen gas (H ₂ ) as gas 7 and generation of excited species (H) of reactive gas (H ₂ ) by ultraviolet light were performed in the same manner as in Example 2 above, and the same as in Reference Example 1 was performed. A metallic tungsten thin film having characteristics was obtained.

By using an ultraviolet lamp as the means for exciting the reactive gas, it was possible to use a lower substrate temperature than when the exciting means was not used, and it was possible to shorten the CVD process time.

As the ultraviolet light source, an ultraviolet laser such as an excimer laser or a vacuum ultraviolet light source by hydrogen discharge can be used. Further, it is possible to combine the method of Examples 1 and 2 with the reference example 2 .

[0038]

As described above, according to the present invention, in a method for forming a thin film by a chemical vapor deposition method in which a source gas is decomposed by using a reactive gas, the source gas and the excited reactive gas are used. By alternately introducing on the substrate,
It is possible to obtain a metal thin film in which the leakage current is suppressed and the flatness of the thin film surface is improved, without erosion of the substrate or roughness of the metal thin film surface.

Further, by using the excited reactive gas, it is possible to use a lower substrate temperature than when no excited species is used, and the CVD time can be shortened.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a CVD apparatus used in Reference Example 1 .

FIG. 2 shows the time intervals at which the source gas and the reactive gas are alternately and discontinuously introduced in Reference Example 1 together with the gas flow rate.

FIG. 3 is a schematic view showing steps of forming a thin film according to Reference Example 1 .

FIG. 4 is a schematic diagram of a CVD apparatus used in Example 1 of the present invention.

FIG. 5 is a schematic view of a CVD apparatus used in Example 2 of the present invention.

6 is a schematic view of a CVD apparatus used in Reference Example 2. FIG.

[Explanation of symbols]

1 ... Gas inlet, 2 ... Gas flow controller, 3 ... discharge tube, 4 ... Reaction chamber, 5 ... vacuum pump, 6 ... Raw material gas, 7 ... Reactive gas, 8 ... Pressure control device, 9 ... Semiconductor device substrate, 10 ... High frequency oscillator, 11 ... coil, 12 ... electromagnet, 13 ... Microwave oscillator, 14 ... Electron sacrotron resonance discharge tube, 15 ... UV lamp.

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) C23C 16/00-16/56 H01L 21/205 H01L 21/28-21/285 JISST file (JOIS)

Claims (3)

(57) [Claims] 1. A half having a step portion by a chemical vapor deposition method.
In the method of forming a metal thin film on a conductor device substrate
Te, and placing the semiconductor device substrate in a reaction chamber, from room temperature
A step of maintaining the temperature below 400 ° C., a step of exhausting the reaction chamber, and a step of introducing a source gas containing a halide into the reaction chamber.
A step of adsorbing the source gas on the gas, a step of interrupting the introduction of the source gas and exhausting it, and introducing a reactive gas into the discharge tube connected to the reaction chamber.
And a step of exciting the semiconductor device substrate by the excited reactive gas.
The raw material gas adsorbed on the plate is reacted to form a thin film on the substrate.
Forming on the body, the metal thin film forming method by a chemical vapor deposition method characterized by having the steps of evacuating to interrupt the introduction of the reactive gas. 2. The step portion is a contact hole portion or
The method of claim 1, wherein the metal thin film is formed by chemical vapor deposition. 3. A semiconductor device substrate containing a plurality of gases alternately.
Chemical vapor deposition method for forming metal thin film by introducing on top
A temperature of the semiconductor device substrate from a room temperature in a reaction chamber.
A step of maintaining the temperature below 400 ° C., a step of exhausting the reaction chamber, and a step of introducing a first source gas containing a halide into the reaction chamber.
A step of admitting, a step of adsorbing the first source gas on the gas, a step of interrupting the introduction of the first source gas and exhausting the gas, and a second step in a discharge tube connected to the reaction chamber. Introduce the gas of
And a step of exciting the semiconductor device substrate by the excited second gas.
The thin film is formed by reacting the first raw material gas adsorbed on the plate.
A method of forming a metal thin film by a chemical vapor deposition method , comprising: forming on the semiconductor device substrate; and interrupting introduction of the second gas and exhausting .