JP2001351915A - Method of manufacturing Ta1-XTiXO hybrid dielectric thin film and Ta1-XTiXO hybrid dielectric thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel dielectric material which can be suitably used as a gate insulating film of a MOS device, has a high dielectric constant, a high applied voltage resistance, and can effectively prevent a leak current. To provide a high dielectric insulating thin film. SOLUTION: On a substrate 5 heated to a predetermined temperature, tantalum alcoholate and titanium alcoholate in containers 3 and 4 are heated and vaporized in oil baths 12 and 13, respectively. Together with the nitrogen carrier gas. Then, the oxygen gas from the oxygen gas source 10 is introduced into the quartz tube 9, and the microwave generated by the microwave generator 2 is introduced to convert the oxygen gas into plasma, which is then introduced onto the substrate 5. Then, by reacting these gases on the substrate 5, Ta _1-X Ti
_An XO mixed dielectric thin film (0 <X <1) is prepared.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a Ta _1-X Ti _X
It relates O hybrid preparation and _{Ta 1-X} Ti X O hybrid dielectric thin film of a dielectric thin film, and more particularly, can be suitably used as a gate insulating film in MOS _{devices, Ta 1-X} Ti X O hybrid dielectric a manufacturing method and a _{Ta 1-X} Ti X O hybrid dielectric thin body thin film.

[0002]

2. Description of the Related Art High dielectric constant for a gate insulating film of a MOS device.
Currently, Ta is used as an electric insulator material.₂ O₅Has been commercialized
It is getting. Also, TiO₂, HfO₂, ZrO₂Such as
Metal oxide is also a gate insulating film material for next-generation MOS devices
It has been studied as

As the gate insulating film becomes thinner with the miniaturization of devices, a higher electric field is applied to the gate insulating film. In general, in a thin film made of a high dielectric constant insulating material, the permittivity and the applied voltage resistance tend to be inversely proportional. Therefore, the maximum amount of electric charge that can be stored in the thin film is determined by the voltage that can be applied to the thin film. Would.

For example, SiO₂Ta in place of₂O₅Is
Its relative permittivity ε_rIs about 25 and SiO₂(Ε_r=
3.9) is about 6 times. Therefore, sufficient applied voltage
In order to provide resistance and prevent leakage current, 130
required for the gate insulating film in next-generation devices with the nm rule.
Essential SiO₂At an equivalent film thickness of 1.5 nm, Ta₂O₅
Requires a film thickness of 9.6 nm. In addition, the first 100
6.4 nm for the nm generation and 3.2 n for the 50 nm generation
m is required. Therefore, T
a₂O₅When using, consider the prevention of leakage current
It is necessary to increase the thickness, and the fineness of the MOS device
This is contrary to the demand for thinning.

[0005]

The present invention can be suitably used as a gate insulating film of a MOS device.
It is an object of the present invention to provide a novel high dielectric insulating thin film having a high dielectric constant, a high applied voltage resistance, and capable of effectively preventing a leak current.

[0006]

In order to achieve the above object,
The present invention, on a substrate that is heated to a predetermined temperature, tantalum source, the titanium source, and supplies a microwave excited oxygen gas, Ta _{1-X Ti X O} hybrid dielectric film (0 on the substrate <X <1) (hereinafter, abbreviated, referred to as "TaTiO hybrid dielectric thin film", characterized in that there) is _formed, a method of manufacturing a _{Ta 1-X} Ti X O hybrid dielectric thin film.

The present inventors have conducted intensive studies to obtain a novel high dielectric insulating thin film having a high dielectric constant and a high applied voltage resistance. As a result, it has been found that a TaTiO mixed dielectric thin film satisfying the above requirements can be obtained by using the tantalum source and the titanium source as described above and reacting them with plasma-activated oxygen by microwave excitation. did.

Therefore, when the TaTiO mixed dielectric thin film obtained by the manufacturing method of the present invention is used as a gate insulating film of a MOS device, a sufficiently high voltage is applied even if the gate insulating film is thinned and the MOS device is downsized. Leakage current can be effectively prevented because of having voltage resistance. Furthermore, since a large amount of charges can be accumulated due to the high dielectric constant of the thin film, a relatively large current can flow between the gate electrodes even when the gate insulating film is thinned.

The TaTiO formed according to the present invention
Despite the high dielectric constant of the hybrid dielectric thin film,
It is considered that the reason for the high applied voltage resistance is that Ta ₂ O ₅ is mixed into the boundary of the TiO ₂ crystal grain boundary, and the electron conduction path is reduced.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments of the present invention. In the production method of the present invention, a tantalum source, a titanium source, and microwave-excited oxygen are used. The type of the tantalum source is not particularly limited as long as it can react with the titanium in the titanium source and oxygen activated by plasma excitation by microwave excitation to form the TaTiO mixed dielectric thin film.

However, it is easily decomposed on a predetermined heated substrate and easily reacts with the titanium and oxygen to form Ta.
Tantalum alcoholate is preferably used because a TiO mixed dielectric thin film can be formed. Since this tantalum alcoholate is liquid at room temperature, it is vaporized by heating to a predetermined temperature, bubbling with nitrogen gas, etc., or by using them together, and supplying gaseous tantalum alcoholate onto the substrate. I do.

As such a tantalum alcoholate,
At least one of pentaethoxy tantalum, pentamethoxy tantalum, pentapropoxy tantalum and pentabutoxy tantalum can be used. These alcoholates can be easily used because they can be easily decomposed and vaporized and are relatively easily available.

Similarly, if the titanium source can react with tantalum in the tantalum source and oxygen activated by plasma by being excited by microwaves to form the TaTiO mixed dielectric thin film, it is particularly preferable. Not limited. However, it is easily decomposed on a predetermined heated substrate, and easily reacts with the tantalum and oxygen to form TaT.
Titanium alcoholate is preferably used because an iO mixed dielectric thin film can be formed. Since this titanium alcoholate is also liquid at normal temperature, it is vaporized by heating to a predetermined temperature or bubbling with a nitrogen gas or the like, or by using them in combination, so that the gaseous titanium alcoholate is deposited on the substrate. Supply.

As such a titanium alcoholate,
Tetraisopropoxy titanium, tetramethoxy titanium,
At least one of tetrapropoxy titanium and tetrabutoxy titanium can be used. These alcoholates can be easily decomposed and vaporized,
Since it is relatively easily available, it can be preferably used.

Further, the substrate on which the TaTiO mixed dielectric thin film is to be formed is to decompose the above-mentioned tantalum source and titanium source, and to obtain the tantalum and titanium obtained by decomposition and oxygen activated by plasma excitation by microwave excitation. To form a TaTiO mixed dielectric thin film, it is necessary to heat to a predetermined temperature. Specifically, it is preferable to heat to 200 to 800 ° C, and it is preferable to heat to 300 to 600 ° C when tantalum alcoholate and titanium alcoholate as described above are used.

Hereinafter, a specific operation procedure in the manufacturing method of the present invention will be described. FIG. 1 is an example of a thin film manufacturing apparatus used in the manufacturing method of the present invention. The thin film manufacturing apparatus shown in FIG. 1 includes a vacuum chamber 1, a microwave generator 2, a container 3 containing a tantalum alcohol as a tantalum source,
A container 4 containing titanium alcoholate as a titanium source.

In the vacuum chamber 1, a substrate 5 on which a TaTiO mixed dielectric thin film is to be formed is placed so as to be held by a heating holder 6. The substrate 5 is heated to a predetermined temperature by the heating holder 6. Further, a vacuum pump 8 is connected to the vacuum chamber 1 via a valve 7, and a predetermined pressure (degree of vacuum) is applied to the inside of the vacuum layer 1 prior to the formation of the TaTiO mixed dielectric thin film.
It is configured to be able to exhaust up to.

The microwave generator 2 is connected to the vacuum chamber 1 via a quartz tube 9. Then, the microwave is introduced into the quartz tube 9 to excite the oxygen gas from the oxygen gas source 10. Then, the excited oxygen gas is supplied onto the substrate 5 in the vacuum chamber 1.

Containers 3 and 4 are each provided with an oil bath 12.
And 13 so that tantalum alcoholate or the like can be heated to a predetermined temperature and vaporized. Furthermore, nitrogen gas is introduced into the containers 3 and 4 from the nitrogen gas sources 14 and 15, and the degree of vaporization of the tantalum alcoholate or the like can be adjusted by bubbling. This nitrogen gas also serves as a carrier gas such as vaporized tantalum alcoholate in addition to bubbling. The vaporized tantalum alcoholate or the like is guided into the vacuum chamber 1 through a pipe provided with the heater 16 and supplied onto the substrate 5 in order to prevent the vaporized tantalum alcoholate from condensing and liquefying.

Since the substrate 5 is preheated to a predetermined temperature, the tantalum alcoholate and the like supplied as described above decompose on the substrate and react with the plasma-activated oxygen, thereby achieving the present invention. It is possible to form a TaTiO mixed dielectric thin film having a high dielectric constant and a high applied voltage resistance, which is the object of the present invention.

The TaTi thus obtained can be obtained.
As is apparent from the following examples, the O-hybridized dielectric thin film has a relative dielectric constant of 35 at a thickness of 30 to 60 nm.
~ 55, Si substrate / TaTiO hybrid dielectric thin film 3
In a MOS structure of 0 to 60 nm / 200 nm Al electrode, 1 A / cm ² or less (0.25 MV /
(when a voltage of 1 cm is applied). Furthermore, according to the manufacturing method of the present invention, when the thickness is 30 to 60 nm,
In a MOS structure having a relative dielectric constant of 35 to 55 and similar to the above, 0.1 A / cm ² or less (0.25 M / unit thickness)
TaTi having a leakage current (when a voltage of V / cm is applied)
An O mixed dielectric thin film can be obtained.

[0022]

EXAMPLES Specific examples of the present invention are shown in the following examples. In this embodiment, a Si substrate is used as the substrate,
Pentaethoxytantalum was used as a tantalum source, and tetraisopropoxytitanium was used as a titanium source. The formation of the TaTiO mixed dielectric thin film was performed using the apparatus shown in FIG.

The vacuum chamber 1 was evacuated to 8 × 10 ⁻⁴ Pa by a vacuum pump 8 through a valve 7. Si substrate 1
Are set on the heating holder 6 in the vacuum chamber 1 and 400 to 4
Heated to 50 ° C. Then, pentaethoxytantalum and tetraisopropoxytitanium are put in containers 3 and 4, respectively, and these containers are put in oil baths 12 and 13, respectively.
It was kept at 65 ° C.

Next, a nitrogen gas is introduced into the containers 3 and 4 from the nitrogen gas sources 14 and 15, and the flow rate of the nitrogen gas is changed within a range of 15 to 80 cc / min to supply the pentagon to the substrate 5. The amounts of ethoxy tantalum and tetraisopropoxy titanium were varied. Next, oxygen gas is introduced at 200 cc / min from the oxygen gas source 10, and 200 W microwaves are introduced from the microwave generator 2 into the quartz tube 9, thereby turning the plasma into plasma. Supplied to

Then, by reacting on the substrate 5 for 3 to 6 minutes, a TaTiO mixed dielectric thin film having a thickness of 30 to 60 nm was formed. During the reaction, the opening degree of the valve 7 was appropriately adjusted so that the pressure in the vacuum chamber 1 was 133 Pa.

Ta of the obtained TaTiO mixed dielectric thin film
The composition ratio of Ti and Ti was estimated from the respective growth rates of Ta ₂ O ₅ and TiO ₂ , and was controlled by the flow control valves 17 and 18. Also, A on the TaTiO mixed dielectric thin film
A thin film was formed to a thickness of 200 nm to form a MOS structure, and the leakage current was examined. Further, the relative permittivity ε _r was examined by capacitance-voltage characteristics.

FIG. 2 is a graph showing the relative permittivity ε _r and the magnitude of the leak current measured using the composition ratio of Ta and Ti as parameters. The leak current in FIG. 2 has a voltage value per unit film thickness of 0.25 MV / cm.
This was performed by applying a voltage having a magnitude such that As apparent from FIG. 2, the TaTiO mixed dielectric thin film manufactured according to the manufacturing method of the present invention has a high relative dielectric constant ε _r of 35 to 55 over the entire composition range thereof and has a dielectric constant of 1 A / cm ² or less. It can be seen that the leakage current value is low. Further, it can be seen that when Ta is contained in an amount of 10 to 20 atomic%, the leak current is extremely low at about 0.1 A / cm ² or less.

FIG. 3 shows a TaTiO layer having a thickness of 42 to 58 nm.
In the MOS structure using the hybrid dielectric thin film, a change in a leakage current value when a gate voltage value is changed is shown. As is clear from FIG. 3, the TaTiO mixed dielectric thin film manufactured by the manufacturing method of the present invention shows a leak voltage value that is approximately one digit lower than that of Ta ₂ O ₅ over almost the entire range of the applied gate voltage.

Therefore, as is apparent from FIGS. 2 and 3, TaTiO manufactured according to the manufacturing method of the present invention is used.
The hybrid dielectric thin film has a higher relative dielectric constant ε _r than Ta ₂ O _5.
It can be seen that the leakage current value is lower by about one digit. Therefore, by using the TaTiO mixed dielectric thin film as a gate insulating film of a MOS device, miniaturization of the device can be achieved while maintaining a low leak current value.

As described above, the present invention has been described in detail based on the embodiments of the present invention with specific examples. However, the present invention is not limited to the above contents, and the present invention is not limited thereto. All modifications and changes are possible.

For example, in the above, the TaTiO mixed dielectric thin film is formed by heating the substrate, but instead of heating the substrate, plasma is introduced onto the substrate,
It can also be formed by decomposing tantalum alcoholate and reacting with oxygen excited by plasma.

In the above manufacturing method, a dielectric thin film containing a metal such as hafnium or zirconium can be formed by appropriately selecting a hafnium source and a zirconium source. As a result, a dielectric thin film having a higher dielectric constant and a higher applied voltage resistance can be provided.

[0033]

As described in the foregoing, according to the production method of the present invention, than Ta ₂ O ₅ which is being put to practical use in place of the SiO ₂ in the MOS devices, high dielectric constant epsilon _r, high applied Ta with low leakage current due to voltage tolerance
_1-X Ti _X O hybrid dielectric thin film (0 <X <1) can be produced. Therefore, by using this thin film as the gate insulating film, it is possible to effectively prevent the leakage current even when the device is miniaturized in response to the demand for the next-generation device. Further, since the electric charge can be accumulated in a large capacity due to the high dielectric constant of the thin film, even if the gate insulating film made of the thin film is thinned by miniaturization of the device, the space between the gate electrodes is relatively small. A large current can flow.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a thin film manufacturing apparatus that can be used in the manufacturing method of the present invention.

FIG. 2 shows Ta obtained by the production method of the present invention.
_1-X Ti X O hybrid dielectric thin film is a graph showing the relative dielectric constant epsilon _r and the leak current value (0 <X <1).

FIG. 3 shows Ta obtained by the production method of the present invention.
₄ is a graph showing the gate voltage dependence of the leakage current in a _1-X Ti _X O hybrid dielectric thin film (0 <X <1).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum tank 2 Microwave generator 3, 4 Container 5 Substrate 6 Heating holder 7 Valve 8 Vacuum pump 9 Quartz tube 10 Oxygen gas source 11, 14, 15 Nitrogen gas source 12, 13 Oil bath 16 Heater 17, 18 Flow control valve

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01B 3/12 304 H01B 3/12 304 312 312 H01L 29/78 H01L 29/78 301G 301F (72) Inventor Hiroya Ikeda Aichi 1-1312 Uedayama, Tenpaku-ku, Nagoya-shi, Japan AB01 AB06 AB20 BA03 CA01 CB33 CB35 DA01 DA06

Claims (11)

[Claims] 1. A tantalum source, a titanium source, and a microwave-excited oxygen gas are supplied to a substrate heated to a predetermined temperature, and a Ta _1-X Ti _X O hybrid dielectric film ( 0 <X <1), wherein Ta
_1-X Ti X O hybrid method for manufacturing a dielectric thin film. 2. The Ta _1-X Ti according to claim 1, wherein the tantalum source is tantalum alcoholate, and the tantalum alcoholate is supplied onto the substrate by vaporizing the tantalum alcoholate. _A method for producing an XO mixed dielectric thin film. 3. The tantalum alcoholate according to claim 1, wherein
Toxitantalum, Pentamethoxytantalum, Pentapro
Selected from Poxytantalum and Pentaboxytantalum
3. The method according to claim 2, wherein the at least one kind is
Ta described_1-X Ti_XA method for producing an O-hybrid dielectric thin film. 4. The Ta _{1-1 according} to claim 1, wherein the titanium source is titanium alcoholate, and the titanium alcoholate is supplied onto the substrate by vaporizing the titanium alcoholate. _A method for producing an _X Ti _X O hybrid dielectric thin film. Wherein said titanium alcoholate, characterized in that at least one selected tetraisopropoxytitanium, tetramethoxy titanium, tetrapropoxytitanium and tetrabutoxytitanium, according to claim 4 Ta _{1- A} method for producing an _X Ti _X O hybrid dielectric thin film. 6. characterized by heating the substrate to 200 to 800 ° C., the manufacturing method of the _{Ta 1-X} Ti X O hybrid dielectric thin film according to any one of claims 2-5. 7. A Ta _1-X Ti _X O mixed dielectric thin film for a gate insulating film of a MOS device, which is manufactured by the method according to claim 1. 8. The method according to claim 1, wherein:
Ta manufactured by_1-X Ti_XO mixed dielectric thin film
MOS device characterized in that it is used as a gate insulating film.
Su. 9. A Ta ₁ having a relative permittivity of 35 to 55 at a thickness of 30 to 60 nm and a leak current of 1 A / cm ² or less when a MOS structure is formed at the thickness. _-X Ti _X O hybrid dielectric thin film. 10. A MOS device having a relative dielectric constant of 35 to 55 at a thickness of 30 to 60 nm and a leakage current of 1 A / cm ² or less when a MOS structure is formed at the thickness. Ta for gate insulating film
_1-X Ti X O hybrid dielectric thin film. 11. Ta having a relative dielectric constant of 35 to 55 at a thickness of 30 to 60 nm and a leakage current of 1 A / cm ² or less when a MOS structure is formed at the thickness.
Characterized in that it comprises the _1-X Ti X O hybrid dielectric thin film as a gate insulating film, MOS devices.