KR100297668B1 - Method for forming metal oxide film - Google Patents

Abstract

A method of forming a metal oxide film required for a semiconductor device on a substrate is disclosed. The method for forming a metal oxide film of the present invention comprises the steps of preparing a gas for forming a metal oxide film by making a metal organic compound and each of the nitrogen compounds in which nitrogen is hydrogen-bonded to a gas state; Contacting the substrates with the substrate. According to the present invention, a metal oxide film having a uniform thickness can be formed at a lower temperature than the conventional method, or a metal oxide film can be formed faster at the same temperature.

Description

METHODS FOR FORMING METAL OXIDE FILM

The present invention relates to a method of forming a film on a substrate, and more particularly to a method of forming a metal oxide film required for a semiconductor device on a substrate.

In making semiconductor devices, dielectric films are used for various purposes. Particularly, as a dielectric film for a capacitor of a semiconductor device, a SiO ₂ film or a composite film of SiO ₂ / Si ₃ N ₄ is widely used. However, a semiconductor device such as DRAM (Dynamic Random Access Memory) or FeRAM (Ferroelectric Random Access Memory) is used. As the degree of integration increases, materials with higher dielectric constants such as Ta ₂ O ₅ , Pb (Zr, Ti) O ₄ , TiO _2, etc. will be used.

In the case of forming a metal oxide film by chemical vapor deposition in a semiconductor process, metal-organic compounds such as alkyl acid and diketone acid compound of a metal that can make a metal oxide film even at a relatively low temperature are used as a metal raw material. Although the metal oxide film can be chemically deposited using only an alkyl acid compound of a metal such as titanium isopropyl acid as a raw material, the oxide film thus formed tends to contain a large amount of carbon. Alternatively, a metal oxide is chemically deposited using an oxygen source such as O ₂ together with a diketone acid compound. However, when the metal oxide film is to be deposited at a low temperature of 300 ° C. or lower, there is a problem that the film is grown too slowly due to low reactivity of O ₂ .

On the other hand, unlike the conventional chemical vapor deposition method of simultaneously supplying the raw materials of the constituent elements constituting the thin film, if the raw materials are sequentially supplied, the thin film can be formed only by the chemical reaction on the surface of the substrate. The thin film of can be grown. This is illustrated in the book "Atomic Layer Growth" edited by T. Suntola and M. Simpson (see Resources: T. Suntola and M. Simpson eds. Atomic Layer Epitaxy , Blackie, London (1990)). . According to this, for example, SiCl ₄ and H ₂ O may be sequentially supplied onto the substrate, and the half reactions represented by the following Chemical Formulas 1 and 2 may be sequentially generated to form SiO ₂ films.

Si-OH ^* + SiCl ₄ → SiO-Si-Cl ₃ ^* + HCl

Si-Cl ^* + H ₂ O → Si-OH ^* + HCl

Here, the asterisks indicate chemical species immobilized on the membrane surface. However, in order to form SiO ₂ film by sequentially supplying only SiCl ₄ and H ₂ O, the substrate should be heated to a temperature of 300 ° C. or higher.

On the other hand, JW Klaus et al. Recently reported that pyridine, which does not directly participate in the reaction, can be fed with SiCl ₄ , H ₂ O to form SiO ₂ films at 17 ° C. (Reference: JW Klaus, O. Sneh, and SM George, "Growth of SiO ₂ at Room Temperature with the Use of Catalyzed Sequential Half-Reactions," Science, Vol. 278, p 1934 (1997 )). They found that the activation energy was lower when pyridine was added than that without pyridine, and this was the first example of using a gaseous catalyst for chemical vapor deposition. In other words, it was estimated that pyridine lowered the activation energy by weakening the bond between oxygen and hydrogen by hydrogen bonding with H ₂ O.

However, the method used by Klaus et al., Ie, the chemical vapor deposition method of sequentially supplying the raw materials to the substrate, is much slower than the chemical vapor deposition method of simultaneously supplying the raw materials, and thus cannot be applied where the film needs to be formed quickly. In addition, this method is applied to a process of forming a SiO ₂ film by supplying SiCl ₄ and H ₂ O to a substrate, there is a problem that H ₂ O is not exhausted well in a vacuum apparatus. In addition, SiCl ₄ , a chlorine compound used as a reaction gas, has a problem in that it is inconvenient to use because it is corrosive.

It is therefore an object of the present invention to provide a method capable of forming a metal oxide film quickly enough even at a low substrate temperature.

Another technical problem of the present invention is to provide a method capable of forming a metal oxide film having a uniform thickness in spite of irregularities on the surface of a semiconductor substrate.

The metal oxide film forming method of the present invention for achieving the above technical problem, a nitrogen compound gas containing a vapor of the metal metal alkyl compound, a metal organic compound and a nitrogen component capable of hydrogen bonding to the metal alkyl acid on the substrate. It is characterized in that the metal oxide film is formed by contact with each other by chemical vapor deposition.

As the nitrogen compound gas, ammonia gas may be used. The vapor of the alkyl acid metal and the nitrogen compound gas may be brought into contact with the substrate at the same time, or may be brought into contact with each other in turn.

In the case where a titanium oxide film is to be formed, titanium isopropyl acid can be used as the metal alkylate, and in the case where a tantalum oxide film is to be formed, tantalum ethyl carbonate can be used as the metal alkylate.

Hereinafter, preferred embodiments of the present invention and comparative examples thereof will be described.

Example 1

A silicon substrate was placed in a reactor made of stainless steel and heated to 300 ° C. Maintain the pressure of the reactor at 10 Torr, bubbling argon gas at a flow rate of 100 sccm to isopropyl acid heated to 60 ° C. to supply the titanium raw material to the reactor, and argon gas and ammonia gas to 50 sccm and 100 sccm, respectively. The titanium oxide film was formed by feeding the reactor for 30 minutes at a flow rate. At this time, the titanium oxide film contains a small amount of nitrogen contained in the ammonia gas. After the deposition, the film was 39.6 nm thick and had a refractive index of 2.2, measured with an ellipsometer.

Comparative Example 1

A silicon substrate was placed in a reactor of Example 1 and heated to 300 ° C. The pressure of the reactor was maintained at 10 Torr, and the titanium raw material was fed to the reactor by bubbling argon gas at a flow rate of 100 sccm in isopropyl acid heated to 60 ° C. and argon gas and oxygen gas were flowed at a flow rate of 50 sccm and 100 sccm, respectively. The reactor was fed for minutes. After evaporation, the film had a thickness of 6.9 nm and a refractive index of 2.0 as measured by an ellipsometer.

Example 2

A silicon substrate was placed in a reactor of Example 1 and heated to 330 ° C. The reactor pressure was maintained at 10 Torr, and argon gas heated to 60 ° C. was bubbled with argon gas at a flow rate of 100 sccm to supply titanium raw material to the reactor, and argon gas and ammonia gas of 50 sccm and 100 sccm, respectively. The reactor was fed at a flow rate for 30 minutes to form a titanium oxide film. At this time, the titanium oxide film contains a nitrogen component as an impurity as described in the first embodiment. After evaporation, the film had a thickness of 54.8 nm and a refractive index of 2.5, measured by an ellipsometer.

Comparative Example 2

A silicon substrate was placed in a reactor of Example 1 and heated to 330 ° C. The pressure of the reactor was maintained at 10 Torr, and the titanium raw material was fed to the reactor by bubbling argon gas at a flow rate of 100 sccm in isopropyl acid heated to 60 ° C. and argon gas and oxygen gas were flowed at a flow rate of 50 sccm and 100 sccm, respectively. A titanium oxide film was deposited by feeding the reactor for minutes. After vapor deposition, the film thickness measured by an ellipsometer was 16.0 nm and the refractive index was 2.4.

Example 3

A silicon substrate was placed in a reactor of Example 1 and heated to 350 ° C. The reactor pressure was maintained at 10 Torr, and argon gas heated to 60 ° C. was bubbled with argon gas at a flow rate of 100 sccm to supply titanium raw material to the reactor, and argon gas and ammonia gas of 50 sccm and 100 sccm, respectively. The titanium oxide film was deposited in the same manner as in Example 1 by supplying the reactor for 30 minutes at a flow rate. After vapor deposition, the film thickness measured by an ellipsometer was 72.1 nm and the refractive index was 2.7.

Comparative Example 3

A silicon substrate was placed in a reactor of Example 1 and heated to 350 ° C. The pressure of the reactor was maintained at 10 Torr, and the titanium raw material was fed to the reactor by bubbling argon gas at a flow rate of 100 sccm in isopropyl acid heated to 60 ° C. and argon gas and oxygen gas were flowed at a flow rate of 50 sccm and 100 sccm, respectively. A titanium oxide film was deposited by feeding the reactor for minutes. After vapor deposition, the film thickness measured by an ellipsometer was 55.7 nm and the refractive index was 2.4.

Example 4

A silicon substrate was placed in a reactor of Example 1 and heated to 300 ° C. The pressure of the reactor was maintained at 10 Torr, argon gas bubbled in titanium isopropyl acid heated to 60 ° C. for 10 seconds at a flow rate of 100 sccm, argon gas not passed through titanium raw material at a flow rate of 100 sccm for 10 seconds, and ammonia gas. 10 seconds at a flow rate of 100 sccm, the argon gas not passed through the titanium raw material was sequentially supplied to the reactor for 10 seconds at a flow rate of 100 sccm for 30 minutes to form a titanium oxide film. After vapor deposition, the film thickness measured by an ellipsometer was 23.9 nm and the refractive index was 2.4.

[Comparative Example 4]

A silicon substrate was placed in a reactor of Example 1 and heated to 300 ° C. The pressure of the reactor was maintained at 10 Torr, argon gas bubbled in titanium isopropyl acid heated to 60 ° C. for 10 seconds at a flow rate of 100 sccm, argon gas not passed through titanium raw material at a flow rate of 100 sccm for 10 seconds, and an oxygen gas. 10 seconds at a flow rate of 100 sccm, argon gas not passed through the titanium raw material was sequentially supplied for 10 seconds at a flow rate of 100 sccm for 10 minutes to form a titanium oxide film. After evaporation, the film had a thickness of 6.9 nm and a refractive index of 2.0 as measured by an ellipsometer.

Example 5

A silicon substrate was placed in a reactor of Example 1 and heated to 265 ° C. The pressure of the reactor is maintained at 7.5 Torr, and argon gas is bubbled into the ethyl tantalum heated to 135 ° C. at a flow rate of 100 sccm to supply a tantalum raw material to the reactor, and 100 sccm of ammonia gas is simultaneously supplied to the reactor for tantalum oxide. A film was formed. As a result of analyzing the composition of the tantalum oxide film by Auger electron spectroscopy, the ratio of tantalum: oxygen: carbon: nitrogen was determined to be about 35: 51: 5: 12. Here, the carbon component is that the carbon component contained in tantalum ethyl carbonate is included in the thin film during the chemical vapor deposition process. After the deposition, the thickness of the film measured by ellipsometer was 37.9 nm.

[Comparative Example 5]

A silicon substrate was placed in a reactor of Example 1 and heated to 265 ° C. The pressure of the reactor was maintained at 7.5 Torr, argon gas was bubbled into the ethyl tantalum heated to 135 ° C. at a flow rate of 100 sccm, and a tantalum raw material was supplied to the reactor, and 100 sccm of oxygen gas was simultaneously supplied to the reactor for 30 minutes. Under this condition, no film was deposited on the silicon substrate.

Example 6

A silicon substrate was placed in a reactor of Example 1 and heated to 350 ° C. The pressure of the reactor was maintained at 7.5 Torr, argon gas heated to 135 ° C. was bubbled with argon gas at a flow rate of 100 sccm to supply tantalum raw material to the reactor, and 100 sccm of ammonia gas was simultaneously supplied to the reactor for 30 minutes. A tantalum oxide film was formed as shown in 5. After the deposition, the thickness of the film measured by an ellipsometer was 220 nm.

Comparative Example 6

A silicon substrate was placed in a reactor of Example 1 and heated to 350 ° C. The pressure of the reactor is maintained at 7.5 Torr, and argon gas is bubbled into the ethyl tantalum heated to 135 ° C. at a flow rate of 100 sccm to supply a tantalum raw material to the reactor, and 100 sccm of oxygen gas is simultaneously supplied to the reactor for tantalum oxide. A film was formed. After the deposition, the film thickness measured by an ellipsometer was 40.3 nm.

Example 7

A silicon substrate was placed in a reactor of Example 1 and heated to 250 ° C. The pressure of the reactor was maintained at 7.5 Torr, and argon gas bubbled in ethyl tantalum heated to 135 ° C. was flowed at 100 sccm for 20 seconds, argon gas was not passed through tantalum raw material at 100 sccm for 5 seconds, and ammonia gas was used. 5 seconds at a flow rate of 100 sccm, argon gas not passed through the tantalum material was sequentially supplied to the reactor for 5 seconds at a flow rate of 100 sccm for 30 minutes to form a tantalum oxide film. After the deposition, the thickness of the film measured by an ellipsometer was 4.4 nm.

Examples and comparative examples as described above are summarized in Table 1 below.

Substrate temperature Reactor pressure Metal Organic Compound Gas supply Supply method Film thickness Example 1 300 ℃ 10 Torr Isopropyl Titanium ammonia The same time 39.6 nm Comparative Example 1 300 ℃ 10 Torr Isopropyl Titanium Oxygen The same time 6.9 nm Example 2 330 ℃ 10 Torr Isopropyl Titanium ammonia The same time 54.8 nm Comparative Example 2 330 ℃ 10 Torr Isopropyl Titanium Oxygen The same time 16.0 nm Example 3 350 ℃ 10 Torr Isopropyl Titanium ammonia The same time 72.1 nm Comparative Example 3 350 ℃ 10 Torr Isopropyl Titanium Oxygen The same time 55.7 nm Example 4 300 ℃ 10 Torr Isopropyl Titanium ammonia Sequential 23.9 nm Comparative Example 4 300 ℃ 10 Torr Isopropyl Titanium Oxygen Sequential 6.9 nm Example 5 265 ℃ 7.5 Torr Tantalum ethyl ammonia The same time 37.9 nm Comparative Example 5 265 ℃ 7.5 Torr Tantalum ethyl Oxygen The same time 0 nm Example 6 350 ℃ 7.5 Torr Tantalum ethyl ammonia The same time 220 nm Comparative Example 6 350 ℃ 7.5 Torr Tantalum ethyl Oxygen The same time 40.3 nm Example 7 250 ℃ 7.5 Torr Tantalum ethyl ammonia Sequential 4.4 nm

Referring to Table 1, it can be seen that when the other conditions are the same, the case where ammonia, which is a nitrogen compound, is supplied, shows a faster film growth rate than when it is not. In addition, the simultaneous feed of the source gas showed a faster film growth rate than the sequential feed. However, in the case of the chemical vapor deposition method of supplying raw materials sequentially, if the substrate temperature is higher than the thermal decomposition temperature of the metal raw material used, a gas phase reaction occurs and the diffusion of the raw materials affects the growth of the film. It is difficult to obtain a film of uniform thickness.

In addition, it was confirmed that the deposition rate is lower when the gas is sequentially supplied than the simultaneous feeding, but the advantage of the sequentially feeding is that even when the uneven surface of the substrate surface is severe, it is possible to deposit a thin film having excellent step coverage. Since it is present, both the sequential supply process and the simultaneous supply process can be effectively used as the thin film deposition process depending on the surface of the substrate.

Therefore, in order to make a metal oxide film having a uniform thickness by using a metal organic compound having a low self-decomposition temperature as a raw material, it is lower than the thermal decomposition temperature of the metal organic compound by supplying nitrogen compound and metal organic compound which can be hydrogen-bonded alternately. It was possible to grow a metal oxide film of uniform thickness at the substrate temperature. A thin film may be formed by simultaneously or sequentially supplying oxygen gas together with the gas of the nitrogen compound and the metal organic compound.

From the results of Example and Klaus et al., It is expected that derivatives of ammonia and other heterocyclic compounds including nitrogen capable of hydrogen bonding to nitrogen also play the same role as ammonia.

Therefore, according to the present invention, it is possible to form a metal oxide film of uniform thickness at a lower temperature than the conventional method, or to form a metal oxide film faster at the same temperature.

Claims (5)

A method of forming a metal oxide film, comprising forming a metal oxide film by chemical vapor deposition by contacting a substrate with a nitrogen compound gas containing a vapor of an alkyl acid metal and a nitrogen component capable of hydrogen bonding to the alkyl acid metal. The method for forming a metal oxide film according to claim 1, wherein the nitrogen compound gas is an ammonia gas. The method of claim 1, wherein the vapor of the metal alkylate and the nitrogen compound gas are in contact with the substrate at the same time. The method of claim 1, wherein the vapor of the metal alkylate and the nitrogen compound gas alternately contact the substrate. The method for forming a metal oxide film according to claim 1, wherein the metal alkylate is titanium isopropyl acid or tantalum ethyl acetate.