JPH0660406B2 - Vapor growth method of hafnium oxide film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a vapor phase growth method for a hafnium oxide film, and more particularly to a vapor phase growth method for a hafnium oxide film used for a capacitive element of a semiconductor device.

[Conventional technology]

An integrated circuit formed on a semiconductor substrate, particularly a silicon semiconductor substrate, is becoming highly integrated and has a large capacity, and the degree of integration of an integrated circuit such as a memory device is increasing to 4 Mbits or more. In order to highly integrate an IC memory composed of one transistor and one capacitance element as a basic cell such as a dynamic random access memory (RAM), reduction of the capacitance element area is the most effective means.

However, when the area of the capacitive element portion is reduced and the capacitance value is reduced, the reliability against a soft error (memory malfunction) due to α rays or the like is deteriorated, so the capacitance value needs to be 50 fF or more. Therefore, conventionally, the reduction of the capacitance value due to the area reduction has been compensated by thinning the capacitance insulating film. However, when the silicon oxide film used in the past is less than 100 Å, the withstand voltage cannot withstand the power supply voltage of 5 V and cannot be used.

Therefore, by forming a groove on the substrate and forming a capacitive element on the inner wall portion of the groove, or by forming the capacitive element into a laminated structure (stacked structure), the same capacitance value as the conventional one can be maintained while being planar. In order to achieve high integration, the area of the capacitive element portion is being reduced. Further, it is also considered to use a high dielectric constant material such as Ta ₂ O ₅ , TiO ₂ , HfO ₂ , ZrO ₂ for the capacitance film instead of the silicon oxide film.

In a large-capacity dynamic RAM of 16 Mbits or more, it is indispensable to have a capacitive element with a groove structure or a laminated structure and to use a high dielectric material for a capacitive film. Ta ₂ O ₅ , Ti
O _2, to a high dielectric constant material such as HfO ₂ is formed in the groove inside or laminated with a thin film, it is necessary to clothing of uneven portions are good, as the thus film formation method, vapor deposition method An excellent method. In addition, Ta ₂ O ₅ , TiO ₂ , HfO ₂ ,
Among high dielectric constant materials such as ZrO _2, HfO ₂ having thermodynamically stable properties is promising as a capacitance film.

The conventional method for forming an HfO ₂ film by chemical vapor deposition is
Alcoholates such as (OC ₄ H ₉ ) ₄ and Hf (OC (CH ₃ ) = CH
Generally, β-diketonate such as COCH ₃ ) ₄ is used as a raw material and grown at normal pressure. For example Proc. 2nd Int. C
onf.on CVD, LosAngeles, P619 (1970) and Thin Solid Fi
lms, 41, 247 (1977).

[Problems to be solved by the invention]

The HfO ₂ film formed by the conventional vapor phase growth method described above is
For example, when an electric field strength of 1 MV / cm is applied, a current density of 10 ^-2 A /
It has a drawback that it has a very large clique current, such as flowing cm ² . Therefore, HfO _{2 produced} by the conventional vapor deposition method is used.
The film has not yet been put to practical use as a capacitor film of a semiconductor device.

[Means for solving problems]

The vapor phase epitaxy method of the hafnium oxide film of the present invention is Hf (OC ₃ H
₇ ) Using ₄ as a raw material, grow under reduced pressure. Hf (OC ₃ H ₇ ) ₄ used as a raw material is a solid at room temperature, and this raw material is heated to 100 to 200 ° C. to be in a liquid state and an inert gas such as Ar or N ₂ is blown into the raw material for bubbling. Thus, the raw material is introduced into the reaction furnace. 0.1-10 torr
It is preferable to vapor-deposit the HfO ₂ film at a growth temperature of 400 to 600 ° C. under reduced pressure.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view of the structure of a vapor phase growth apparatus used in the first embodiment of the vapor phase growth method of the present invention. This device includes gas introduction pipes 11 and 12, carrier gas introduction pipe 13, vacuum pump 15, exhaust port 16, valves 21, 22, and 23.
24, reactor 5, heaters 6, 7, wafer 8, raw material Hf
It has a vaporization chamber 9 filled with (OC ₃ H ₇ ) ₄ .

A procedure for vapor-phase growing a hanium oxide film on a silicon substrate by the vapor-phase growth method of the present invention will be described. First, vaporization chamber 9
Hf (OC ₃ H ₇ ) as a starting material that is solid at room temperature and is filled with
₄ is heated to 100 to 200 ° C. by the heater 7 to be in a liquid state. Also, the wafer 8 in the reaction furnace is heated to 400 by the heater 6.
Heat to ~ 600 ° C in vacuum.

When the Hf (OC ₃ H ₇ ) ₄ and the wafer 8 are sufficiently heated, Ar is used as a carrier gas for carrying the raw material, and the Hf in the vaporization chamber 9 is brought into a liquid state from the gas introduction pipe 13.
By introducing the carrier gas Ar into (OC ₃ H ₇ ) ₄ and performing bubbling, a gas containing Hf (OC ₃ H ₇ ) ₄ (hereinafter abbreviated as raw material gas) is introduced into the reaction furnace 5 and Pressure is 0.1-10 Torr, and the temperature of the wafer 8 is 400-
A hafnium oxide film is grown on the wafer 8 while maintaining the temperature at 600 ° C.

At this time, O ₂ gas may be introduced into the reaction furnace 5 through the gas introduction pipe 12 in order to improve the growth rate and film quality of the hafnium oxide film. Furthermore, the pressure in the reaction furnace during film growth is set to 0.1 to
The base gas Ar may be introduced into the reaction furnace through the gas introduction pipe 11 in order to adjust the pressure to 10 torr. As an example of the flow rate of these gases, the carrier gas for raw material transportation is 100 to 20.
0 cc / min, O ₂ gas 1 / min, base Ar gas 1
/ Min. Since the total gas flow rate varies depending on the exhaust capacity of the vapor phase growth apparatus, it may be adjusted so that the pressure in the reaction furnace is 0.1 to 10 torr. The pressure may be adjusted with O ₂ gas without using the base Ar gas.

FIG. 2 shows the leak current characteristics of the hafnium oxide film formed by the vapor phase epitaxy method of the present invention described above. In the figure, the horizontal axis represents the electric field intensity applied to the hafnium oxide film, and the vertical axis represents the current density flowing in the hafnium oxide film. The leakage current characteristics of the film formed by the conventional vapor deposition method are also shown in FIG. The hafnium oxide film formed by the vapor phase epitaxy method of the present invention was able to greatly reduce the leakage current by several orders of magnitude as compared with the conventional method.

The relative permittivity of the obtained hafnium oxide film is 20 to 2
5, which is almost the same as the relative permittivity of the film obtained by the conventional method.

Thus, the vapor phase growth method of the present invention can form a hafnium oxide film having a high dielectric constant and a small leak current.

Next, as a second embodiment of the present invention, a film forming procedure for vapor phase growing a hafnium oxide film on a refractory metal electrode provided on a silicon substrate will be described. The vapor phase growth apparatus used in the second embodiment is the same as the vapor phase growth apparatus shown in FIG.

Similar to the first embodiment, first, the raw material Hf (OC ₃ H ₇ ) ₄ filled in the vaporization chamber 9 is heated to 100 to 20 by the heater 7.
Heat to 0 ° C. to make it liquid. The wafer 8 in the reaction furnace is also heated by the heater 6 to 400 to 600 ° C. in vacuum. Hf
When the (OC ₃ H ₇ ) ₄ and the wafer 8 are sufficiently heated, Ar is used as a carrier gas for carrying the raw material, and Hf which is in a liquid state in the vaporization chamber 9 from the gas introduction pipe 13 is used.
A carrier gas Ar is blown into (OC ₃ H ₇ ) ₄ to bubble the raw material gas into the reaction furnace 5. The pressure in the reaction furnace 5 is 0.1 to 10 Torr, and the temperature of the wafer 8 is 400 to 600. A hafnium oxide film is grown on the refractory metal electrode on the wafer 8 while maintaining the temperature at ℃.

In the present embodiment, when O ₂ gas is contained in the reaction furnace, the refractory metal is easily oxidized by O ₂ gas, so unlike the first embodiment, the O ₂ gas is not introduced into the reaction furnace to form a film. Grow. That is, the pressure in the reaction furnace at the time of film growth is 0.1 to 10
Base gas Ar is introduced into the gas introduction pipe 11 to adjust torr.
And the raw material gas is introduced into the reaction furnace to grow the film.

In this embodiment, since O ₂ gas is not used for film growth, the growth rate and film quality of the film are slightly lower than those of the first embodiment, but compared with the leak current of the film by the conventional vapor phase growth method, The leak current of the film of this example is extremely small.

By the vapor phase growth method of the present invention, a hafnium oxide film having a small leak current and a high dielectric constant can be formed on the refractory metal electrode as in the first embodiment.

Further, in the case of forming a hafnium oxide film on the refractory metal electrode, the vapor phase growth method which does not use O ₂ gas has been described in this embodiment, but in order to prevent the refractory metal electrode from being oxidized, By introducing only the base Ar gas and the raw material gas without introducing O ₂ gas into the reactor at the initial stage of growth, after vapor phase growth of the hafnium oxide film by about 50 to 100 Å, O ₂ gas is also added in addition to the above gas. It is also one method to introduce a hafnium oxide film with good film quality into a reaction furnace and vapor-phase grow it. Furthermore, the effect of the present invention does not change even if the timing of introducing the O ₂ gas into the reaction furnace is delayed by several seconds from the timing of introducing the raw material gas.

Although the hafnium oxide film is formed on the silicon substrate or the refractory metal in the first and second embodiments, the effect of the present invention can be obtained even if the hafnium oxide film is formed on another semiconductor substrate, polycrystalline silicon, silicide or polycide. Are the same. Further, although Ar was used as the carrier gas in the vapor phase growth method of the present invention, an inert gas such as N ₂ or He may be used. The vapor phase growth apparatus used in the present invention may be either a cold wall type or a hot wall type.

〔The invention's effect〕

As described above, the present invention uses Hf (OC ₃
Using H _{7) 4,} and heating the material to 100 to 200 ° C., an inert gas such as Ar and N ₂ by introducing a material into the reactor by bubbling blowing in the in the raw material, 0.
By vapor-depositing a hafnium oxide film at a growth temperature of 400 to 600 ° C. under a reduced pressure of 1 to 10 torr, the leakage current of the hafnium oxide film can be greatly reduced, and a low leakage current and high dielectric constant capacitance film. There is an effect that can be formed.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of a vapor phase growth apparatus used in the vapor phase growth method of the present invention, and FIG. 2 is a diagram showing leak current characteristics of a hafnium oxide film formed by the vapor phase growth method of the present invention. . 11, 12 ... Gas inlet pipe, 13 ... Carrier gas inlet pipe, 15 ... Vacuum pump, 16 ... Exhaust port,
21, 22, 23, 24 ... Valve, 5 ... Reactor,
6, 71 ... Heater, 8 ... Wafer, 91 ... 1 Vaporization chamber filled with Hf (OC ₃ H ₇ ) ₄ raw material.

Claims (1)

[Claims] 1. A vapor phase growth method for a hafnium oxide film, which comprises using Hf (OC ₃ H ₇ ) ₄ as a raw material and performing growth under reduced pressure.