JP3319138B2 - Method of forming high dielectric film containing tantalum - 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 high dielectric film containing tantalum, and the present invention can be applied to, for example, formation of a capacitor insulating film used in a semiconductor device.

[0002]

Presently, in the semiconductor device, a silicon nitride film (Si ₃ N ₄₎ is used as an insulating film or a capacitor insulating film. The capacitance insulating film is used, for example, as a capacitance for accumulating charges in a DRAM.
And, for example, next generation ULSI (particularly DRAM)
As a material of a capacitor insulating film for use, a material containing tantalum (Ta) having a higher relative dielectric constant, for example, a high dielectric film made of Ta ₂ O ₅ is being studied instead of a silicon nitride film. The capacitance of the capacitive insulating film is C, the relative permittivity is ε,
When the area is S and the thickness is d, the following relationship holds: C = ε × S / d. As semiconductor devices become denser,
It is necessary to reduce the area S of the capacitance insulating film. Therefore,
In order to keep the capacitance C of the capacitive insulating film the same, the relative dielectric constant ε of the material forming the capacitive insulating film must be increased. For example, in a bipolar transistor, when the area of the transistor element is reduced to 1/5, the area of the capacitor insulating film occupies half of the entire transistor element.

[0005] Ta ₂ O ₅ constituting a capacitive insulating film has a high relative dielectric constant of 20 to 30. By the way, Si ₃ N ₄ and SiO
The relative dielectric constants of ₂ are respectively 6 to 7, 3.7 to 3.9. Normally, CV using TaCl ₅ and O ₂ as source gas
A Ta ₂ O ₅ film is formed by Method D.

[0004]

The Ta ₂ O ₅ [0005] In this way a high dielectric constant, but is promising as a high-dielectric capacitor insulating film material, there is a problem leakage current characteristics, the breakdown voltage characteristics.
One of the methods for solving such a problem is TaC.
After a l ₅ and O ₂ was deposited the Ta ₂ O ₅ film by a CVD method on a substrate made of a silicon substrate by using as a raw material gas, the active oxygen annealing (e.g., UV / O ₂₎ processing the Ta ₂ O ₅ A method of applying the film has been proposed. T deposited by CVD method
Since a is the ₂ O ₅ film is an oxygen atom and its surrounding Ta atoms exist Ta-O _X voids missing simultaneously, the leakage current characteristics and withstand voltage characteristics are considered bad. However, the oxygen atoms diffused from the Si atom and an atmosphere which has moved from the silicon substrate by reactive oxygen annealing treatment, according Ta-O _X voids are compensated, believed to leakage current characteristics and withstand voltage characteristics are improved I have.

There has been proposed a method capable of further improving the leak current characteristic and the withstand voltage characteristic than the active oxygen annealing treatment. In this method, Ta (OC ₂ H ₅ ) ₅ and O ₂ are used as a CVD source gas,
After forming the ₂ O ₅ film, the Ta ₂ O ₅ film is subjected to high-frequency oxygen plasma treatment. By high frequency oxygen plasma treatment
While keeping the Ta ₂ O ₅ film is an amorphous phase, Ta ₂ O ₅ carbon or hydrogen in the film can diffuse outward, and since the replenishment of oxygen to the oxygen defect is made, further improvement leakage current characteristics and withstand voltage characteristics Is believed to be.

When a high dielectric film made of Ta ₂ O ₅ is formed by the CVD method, tantalum (Ta) such as Ta (OC ₂ H ₅ ) _{5 which} is easier to handle than TaCl ₅ is used as a source gas.
There is a tendency to use an organic metal compound gas. When such a Ta-based organometallic compound is used as a source gas, carbon (C) is taken into the amorphous high-dielectric film when the high-dielectric film is formed, and contamination of the high-dielectric film by carbon is caused. Is a major problem. The leakage current characteristics are also deteriorated by such carbon contamination. By high frequency oxygen plasma treatment
Although it is possible to remove carbon from the high dielectric film to some extent, it is hard to say that carbon is removed from the high dielectric film with high efficiency.

[0007] As described above, improvement in the leakage current characteristics and withstand voltage characteristics of the Ta ₂ O ₅ film by the conventional high-frequency oxygen plasma treatment also not be said to be still insufficient, Ya leakage current characteristic of the Ta ₂ O ₅ film There is a strong demand for further improving the withstand voltage characteristics. Accordingly, an object of the present invention is to provide a method for forming a high dielectric film containing tantalum, which can further improve the leakage current characteristics and the breakdown voltage characteristics.

[0008]

According to a first aspect of the present invention, there is provided a method for forming a high dielectric film, comprising: forming a high dielectric film containing tantalum (Ta) on a substrate; After that, plasma treatment is performed on the high dielectric film using a gas containing at least nitrogen (N).

In the method of forming a high dielectric film according to the first aspect of the present invention, the high dielectric film is formed on a substrate by a thermal CVD method using an organometallic material as a source gas or a plasma CVD method.
It is preferable to carry out by the VD method.

The second object of the present invention for achieving the above object is as follows.
In the method of forming a high dielectric film according to the aspect, a gas containing at least nitrogen (N) and a gas containing tantalum (Ta) are used as source gases, and a high dielectric film containing tantalum (Ta) is formed on a substrate. It is characterized by being formed by a CVD method.

In the method of forming a high dielectric film according to the second aspect of the present invention, the CVD method may be a thermal CVD method or a plasma CVD method using an organic metal material as a source gas. In addition, a mode may be included in which after forming a high dielectric film containing tantalum (Ta) on a substrate, plasma processing is performed on the high dielectric film using a gas containing at least nitrogen (N).

As the organometallic material, Ta (OC ₂ H ₅ )
₅ , Ta (OCH ₃ ) ₅ , Ta (N (CH ₃ ) ₂ ) ₅ , Ta
(OC ₂ H ₅ ) _X (N (CH ₃ ) ₂ ) _Y (where X + Y =
5) and a tantalum-based organometallic compound selected from the group consisting of Ta (OCH ₃ ) _X (N (CH ₃ ) ₂ ) _Y (where X + Y = 5).

In the method of forming a high dielectric film according to the present invention, the plasma treatment is performed in a gas containing at least nitrogen (N), more specifically, in an NH ₃ gas atmosphere or N 2 gas.
It is desirable to carry out in an H ₃ + O ₂ gas atmosphere. Other examples of the N-containing gas include N ₂ O, N ₂ H ₂ , and N ₂ .

In the method of forming a high dielectric film according to the second aspect of the present invention, examples of the gas containing at least nitrogen (N) include NH ₃ , N ₂ O, N ₂ H ₂ and N _2. Among them, NH ₃ is preferably used.

The high dielectric film formed by the method of forming a high dielectric film of the present invention is Ta ₂ O ₅ macroscopically, and contains about 1 atomic% or less of N atoms microscopically. Ta ₂ O ₅ .

[0016]

In the method for forming a high dielectric film according to the first aspect of the present invention, a gas containing at least N, for example, NH ₃
Plasma treatment is performed on the high dielectric film using a gas. Nitrogen atoms have a smaller atomic radius than oxygen atoms. Therefore, nitrogen atoms are more easily incorporated into the high dielectric film than oxygen atoms,
As a result, carbon atoms in the high dielectric film are easily extracted from the high dielectric film in the form of CN. Besides, Ta-O
Nitrogen atoms are even more effective in recovering and compensating for oxygen vacancies such as _X voids. That is, since the nitrogen atom has a smaller number of electrons in the outermost shell than the oxygen atom, the nitrogen atom has a larger number of bonds (with the Ta atom) and is easily bonded to Ta. Therefore, the leakage current characteristics and the breakdown voltage characteristics of the high dielectric film can be improved more effectively than the conventional high-frequency oxygen plasma treatment.

In the method of forming a high dielectric film according to the second aspect of the present invention, when a high dielectric film containing Ta is formed on a substrate by a thermal CVD method or a plasma CVD method, at least N is contained. Gas is used as a source gas. Nitrogen atoms have a smaller atomic radius than oxygen atoms. Therefore, during the formation of the high dielectric film, the nitrogen atoms are more easily incorporated into the high dielectric film than the oxygen atoms, and as a result, the carbon atoms in the high dielectric film become CN in the form of CN. More easily withdrawn from Moreover, in terms of recovery and compensates for oxygen defects such Ta-O _X voids, nitrogen atom is more effective. Therefore, the leak current characteristics and the breakdown voltage characteristics of the high dielectric film can be improved more effectively than the conventional high-frequency oxygen plasma treatment.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on embodiments with reference to the drawings.

Example 1 The method for forming a high dielectric film of Example 1 relates to the first aspect of the present invention. In the first embodiment, after a high dielectric film containing Ta is formed on a substrate, plasma processing is performed on the high dielectric film using a gas containing at least N (for example, NH ₃ + O ₂ ). In Example 1, the method of forming a high dielectric film containing Ta on a substrate is as follows.
It is a known method. That is, the first embodiment is different from the prior art in that the high-dielectric film is subjected to plasma processing using a gas containing at least N.

[Step-100] Conventional Single-wafer LPCV
Using a D apparatus, TaCl ₅ or Ta (OC
₂ H _{5) 5,} and 5 reduced pressure to a volume percent O ₃ as a raw material gas (L
P) A high dielectric film containing Ta (Ta ₂ O ₅ ) was formed on the substrate by thermal CVD. The base is made of, for example, a polysilicon film. When forming the high dielectric film by the low pressure thermal CVD method, the temperature of the substrate is set to 300 ° C. to 500 ° C.
The pressure in the reaction chamber of the VD device was set to 10 to 1000 Pa. The thickness of the high dielectric film was about 10 nm. Instead of using O ₃ as the source gas, O ₃ and O ₂ may be used. Further, instead of using O ₃ as a source gas, O ₂ may be used to form a high dielectric film by a plasma CVD method. Also, a batch LPCVD apparatus can be used instead of a single wafer type LPCVD apparatus.

[Step-110] The high dielectric film thus formed is subjected to plasma processing. Specifically, NH ₃ : O ₂
A mixed gas of 1:10 was flowed in a total amount of 500 sccm, and plasma processing was performed at an RF power of 200 W for 10 minutes. At this time, the temperature of the substrate was set to 400 to 800 ° C. In addition, the time of the plasma treatment increases as the thickness of the high dielectric film increases.
It is desirable to use a long time. The plasma processing can be performed in the same CVD apparatus following [Step-100] using, for example, an LPCVD apparatus provided with an RF power supply electrode. After performing the plasma treatment, it is preferable to perform a heat treatment at about 700 ° C. on the high dielectric film to polycrystallize the amorphous high dielectric film.

The leakage current characteristic of the high dielectric film thus obtained was examined. When the applied electric field was 5 MV / cm, the current density was 10 ⁻⁵ A / cm ² or less. [Step-110]
The current density of the high dielectric film when the plasma treatment was not performed was 10 ^-1 A / cm ² or more. Further, the current density of the high dielectric film when the conventional high-frequency oxygen plasma treatment was performed was about 10 ⁻³ A / cm ² .

(Embodiment 2) The method of forming a high dielectric film of Embodiment 2 relates to the second aspect of the present invention. In the second embodiment, a gas containing at least N (for example, NH ₃ ) and an organic metal material containing Ta are used as source gases,
A high dielectric film containing a is formed on a substrate by a CVD method.
In the second embodiment, unlike the first embodiment, the plasma processing after the formation of the high dielectric film is not performed. The second embodiment is different from the prior art in that a high dielectric film is formed by a CVD method using a gas containing at least N as a part of a source gas.

[Step-200] Ta (OC ₂ H ₅ ) ₅ and NH ₃ are used as source gases in a plasma CVD method using a conventional single-wafer plasma CVD apparatus to contain Ta on a substrate. A high dielectric film (Ta ₂ O ₅ ) was formed. The base is made of, for example, a polysilicon film. O ₂ gas was further used as a source gas in the CVD method. When forming the high dielectric film by the plasma CVD method, the temperature of the substrate is set to 300 ° C. to 5 ° C.
The temperature was set to 00 ° C., and the pressure in the reaction chamber of the plasma CVD apparatus was set to 10 to 1000 Pa. At the time of film formation, NH ₃ : O ₂
= 1:10 mixed gas was flowed in a total amount of 500 sccm. The thickness of the high dielectric film was about 10 nm. The source gas is O
Instead of using ₂ , O ₃ may be used to form a high dielectric film by a low pressure thermal CVD method. After this film formation, about 700 ° C
By subjecting the high-dielectric film to the heat treatment described above, the amorphous high-dielectric film is preferably polycrystallized.
It should be noted that a batch type plasma CVD apparatus may be used instead of a single wafer type plasma CVD apparatus.

The leakage current characteristics of the thus obtained high dielectric film were examined. As a result, it was found that the high dielectric film had substantially the same leakage current characteristics as the high dielectric film obtained in Example 1. The method of forming a high dielectric film described in the second embodiment has an advantage that the throughput is improved because the plasma treatment after the formation of the high dielectric film can be omitted.

The [Step-110] of the first embodiment may be executed following the [Step-200]. In this case, although an improvement in throughput cannot be expected, it is possible to further improve the leak current characteristics and the breakdown voltage characteristics of the high dielectric film.

(Embodiment 3) A DRAM having a stacked capacitor cell structure provided with a high dielectric capacitance insulating film made of Ta ₂ O ₅ formed by applying the method of forming a high dielectric film of the present invention. FIG. 1 is a schematic partial cross-sectional view of a semiconductor device. An outline of a method for manufacturing the semiconductor device illustrated in FIG. 1 is as follows. (A) An element isolation region 12 having a LOCOS structure is formed in a silicon semiconductor substrate 10. (B) The gate electrode 14 and the gate wiring 14A (word line) are formed of, for example, polysilicon. (C) The source / drain regions 16 are formed. (D) After an interlayer insulating layer 18 made of, for example, SiO ₂ is formed on the entire surface, an opening is provided in the interlayer insulating layer 18 above the source / drain region 16, and the opening and the interlayer insulating layer 1 are formed.
An electrode 20 for a capacitor made of, for example, polysilicon is formed on 8. (E) The method of forming a high dielectric film according to the present invention
A high dielectric film 22 made of Ta ₂ O ₅ is formed on the first insulating layer 18 and the interlayer insulating layer 18. In this case, the electrode 20 made of polysilicon and the interlayer insulating layer 18 correspond to the base. Further, the high dielectric film 22 corresponds to a capacitance insulating film. (F) Next, the electrode 24 for the capacitor made of ONO
To form (G) Finally, a passivation film 30 made of SiN
Is formed on the entire surface.

Although the present invention has been described based on the preferred embodiments, the present invention is not limited to these embodiments. The source gas and film forming conditions described in the examples are
It can be changed as appropriate depending on the CVD equipment used.

[0029]

According to the present invention, after forming the high dielectric film, the high dielectric film is subjected to plasma treatment using a gas containing at least nitrogen (N), or the high dielectric film is formed on the substrate. When forming by a CVD method, a gas containing at least nitrogen (N) is used as a source gas. Therefore, during or after film formation, carbon is effectively extracted from the high dielectric film, and oxygen defects are effectively compensated, so that the high dielectric film has excellent leakage current characteristics and withstand voltage characteristics. Can be granted.

The method of forming a high dielectric film according to the second aspect of the present invention is different from the method of forming a high dielectric film according to the first aspect of the present invention, in which a high dielectric film is formed. Basically, a plasma processing step is not required, and the manufacturing process of the semiconductor device can be simplified.

[Brief description of the drawings]

FIG. 1 is a schematic partial cross-sectional view of a semiconductor device on which a capacitance insulating film made of a silicon nitride film is formed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Silicon semiconductor substrate 12 Element isolation region 14, 14A Gate electrode and gate wiring 16 Source / drain 18 Interlayer insulating layer 20, 24 Capacitor electrode 22 Silicon nitride film 30 Passivation film

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI H01L 27/04 27/108

Claims (3)

(57) [Claims] 1. A gas containing at least nitrogen, and using a gas containing tantalum raw material gas, after the high-dielectric film containing tantalum is formed by a CVD method on the substrate, less the
Plasma treatment on the high dielectric film using a gas containing nitrogen
A method of forming a high dielectric film. 2. A CVD method, a method of forming the high dielectric film according to claim 1, wherein the organometallic material is a thermal CVD method or a plasma CVD method as a raw material gas. 3. The organic metal material is Ta (OC ₂ H ₅ ) ₅ ,
a (OCH ₃ ) ₅ , Ta (N (CH ₃ ) ₂ ) ₅ , Ta (OC _{2
H 5) X (N (CH} 3) 2) Y ( where, X + Y = 5), and _{Ta (OCH 3) X (N} (CH 3) 2) Y ( where, X + Y =
3. The method for forming a high dielectric film according to claim 2 , comprising a tantalum-based organometallic compound selected from the group consisting of (5).