JP2005129819A - Manufacturing method of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently carry out a removal process of a specific element immediately after formation of an Hf-based oxide film, and further add nitrogen to the Hf-based oxide film formed in the film-forming step to improve its thermal stability, Reduces the diffusion of impurities.
A semiconductor device manufacturing method includes a film forming step and a removing step. In the film forming process, a film forming gas is supplied into the reaction chamber 1 to form an amorphous thin film including an Hf-based oxide film on the rotating substrate 4. In the removing step, a gas containing N atoms activated by plasma is supplied to remove a specific element which becomes an impurity in the film formed in the film forming step and mix nitrogen. The film forming process and the removing process are continuously repeated a plurality of times in the same reaction chamber 1 by the control device 25.
[Selection] Figure 1

Description

  The present invention relates to a method for manufacturing a semiconductor device in which a thin film is formed on a substrate.

CVD (Chemic) that performs a predetermined film forming process on the surface of a substrate (substrate to be processed on which a fine electric circuit pattern based on silicon wafer, glass, or the like is formed) is one of the semiconductor manufacturing processes
al Vapor Deposition) process. This is because a substrate is loaded into an airtight reaction chamber, the substrate is heated by a heating means provided in the chamber, a chemical reaction occurs while introducing a film forming gas onto the substrate, and a fine electric circuit provided on the substrate. A thin film is uniformly formed on a pattern. In such a reaction chamber, the thin film is also formed on a structure other than the substrate. In the CVD apparatus shown in FIG.
A shower head 6 and a susceptor 2 are provided in the reaction chamber 1, and a substrate 4 is placed on the susceptor 2. The film forming gas is introduced into the reaction chamber 1 through the raw material supply pipe 5 connected to the shower head 6, and is supplied onto the substrate 4 through a large number of holes 8 provided in the shower head 6. The gas supplied onto the substrate 4 is exhausted through the exhaust pipe 7. The substrate 4 is heated by a heater 3 provided below the susceptor 2.

As such a CVD apparatus, an organic chemical material is used as a film forming raw material, and amorphous HfO ₂ is used.
MOC for forming a film or an amorphous Hf silicate film (hereinafter simply referred to as an Hf-based oxide film)
VD (Metal Organic Chemical Vapor Deposition) equipment and ALD (Atomic Layer Depo)
sition) equipment.

As a HfO ₂ film forming raw material,
Hf [OC (CH ₃ ) ₃ ] ₄ (hereinafter abbreviated as Hf- (OtBu) ₄ ),
Hf [OC (CH ₃ ) ₂ CH ₂ OCH ₃ ] ₄ (hereinafter abbreviated as Hf- (MMP) ₄ ),
However, MMP: methylmethoxypropoxy or the like is used.
As the Hf silicate film forming raw material, Si [O (C2H5)] ₄ (hereinafter abbreviated as TEOS) together with the HfO ₂ film forming raw material,
_{Si [OC (CH 3) 2} CH 2 OCH 3] 4 ( hereinafter, referred to as Si- _{(MMP) 4),}
However, Si raw materials such as MMP: methylmethoxypropoxy are used,
Hf [O—Si— (CH ₃ )] ₄ (abbreviated as Hf— (OSi) ₄ )
For example, raw materials containing Hf and Si atoms are used.
Hereinafter, Hf- (MMP) ₄ and Si- (MMP) ₄ are collectively referred to as MMP-based raw materials.

Among these, many organic materials such as Hf- (OtBu) ₄ and MMP raw materials are in a liquid phase at normal temperature and pressure. For this reason, for example, MMP-based raw materials are used after being heated and converted into a gas by vapor pressure. Using such a raw material, an Hf-based oxide film is formed, for example, at a substrate temperature of 450 ° C. or lower using the CVD method. This Hf-based oxide film is C
Impurities such as H and OH are contained in a large amount of several percent. As a result, the category indicating the electrical property of a substance belongs to a semiconductor or a conductor contrary to the intention.

In order to ensure the electrical insulation and stability of such a thin film, an Hf-based oxide film is added to the Of oxide film.
Converted to a dense insulator film with high density annealing by removing C and H by applying a high-speed annealing process (hereinafter abbreviated as RTA [Rapid Thermal Annealing]) at 650-800 ° C in ₂ or N ₂ atmosphere. Attempts have been made to do so. Here, the purpose of RTA is to remove impurities such as C and H in the film and to make them dense. Densification is not performed until crystallization, but is performed to reduce the average interatomic distance in the amorphous state.

Furthermore, the purpose of increasing the thermal stability of such a film, that is, the purpose of preventing crystallization and maintaining an amorphous state, or when this Hf-based oxide film is used as a gate insulating film,
-For the purpose of preventing the diffusion of impurities such as boron and phosphorus mixed in the Si electrode, a high-speed annealing process (hereinafter referred to as RTN [Rapid Thermal Nitrification]) at about 600 ° C. to 800 ° C. in an ammonia (NH ₃ ) atmosphere. ) Is attempted to nitride the Hf-based oxide film.

FIG. 11 shows a cluster device configuration in a conventional method for forming an Hf-based oxide film. The substrate is carried into the load lock chamber 32 from the outside of the apparatus, subjected to substrate surface treatment such as RCA cleaning (a typical cleaning method based on hydrogen peroxide) in the first reaction chamber 33, and the second reaction chamber 34 described above. An Hf-based oxide film is formed by the conventional equivalent method, RTA treatment (impurity removal, thermal annealing treatment) is performed in the third reaction chamber 35, and an electrode (poly-Si thin film or the like) is formed in the fourth reaction chamber 36. . The substrate on which the electrodes are formed is carried out of the apparatus from the load lock chamber 32.

In the third reaction chamber 35, when C and H are separated from the Hf-based oxide film by the RTA process, the surface state loses flatness and changes to an uneven surface state. Further, the RTA treatment causes the Hf-based oxide film to be partially crystallized, so that a large current is likely to flow through the crystal grain boundary, and there arises a problem that the insulating property and its stability are impaired. These problems are common to the thin film deposition method using the MOCVD method or the ALD method using not only an insulator but also all organic chemical materials.

In the second reaction chamber 34, a thin film is also formed on a structure other than the substrate. This is called a cumulative film, and a large amount of C and H is mixed in this cumulative film. For this reason, as the number of processed substrates increases, the amount of C and H released from the accumulated film increases, and the amount of C and H mixed in the Hf-based oxide film formed on the substrate gradually increases as the number of processed substrates increases. Will increase. This phenomenon makes it very difficult to keep the quality of the continuously produced Hf-based oxide film constant. In order to solve such a worrisome phenomenon, it is necessary to frequently perform a removal process of the accumulated film by self-cleaning, which is a factor of reducing productivity.

The following thin film forming techniques are also disclosed, but all relate to a tantalum oxide film and not to an Hf-based oxide film.

(1) In the same reaction chamber, a natural oxide film on the substrate surface is removed by plasma treatment, a tantalum film or a low-oxidation tantalum oxide film is then formed, and then O ₂ plasma treatment is performed (see Patent Document 1).

(2) After removing the natural oxide film on the substrate surface in the same reaction chamber, a TiN film (lower electrode) is formed. Then, a Ta film is formed, and RPO (remote plasma oxidation) is applied to the Ta film.
After the Ta ₂ O ₅ film is formed by processing, a Si ₃ N ₄ film is formed. This Ta
_The film forming process of the ₂ O ₅ film and the Si ₃ N ₄ film is repeatedly performed to form a Ta ₂ O ₅ / Si ₃ N ₄ film laminated film. Finally, a TiN film (upper electrode) is formed (see Patent Document 2).

(3) depositing a first tantalum oxide film (amorphous (amorphous), 3 nm), and then performing heat treatment (800 ° C., 1 minute) in a non-oxidizing atmosphere to crystallize the first tantalum oxide film; A second tantalum oxide film is deposited (polycrystal, 7 nm) on the first tantalum oxide film. And
Oxygen defects are recovered by heat treatment (500 ° C., 5 minutes) in an oxidizing atmosphere (see Patent Document 3)
.
JP-A-5-221644 JP-A-5-267567 JP-A-2001-24169

As described above, in the conventional technique for forming an amorphous thin film, the surface state of the Hf-based oxide film loses flatness due to the RTA process and changes to an uneven surface state, or the Hf-based oxide film is partially crystallized and crystallized. There was a problem that grain boundaries were generated, resulting in low insulation and stability.

In addition, in order to make the quality of the continuously produced Hf-based oxide film constant, it is necessary to frequently perform a cleaning process of the accumulated film in which a large amount of C and H is mixed, resulting in a decrease in productivity. There was a problem.

Further, when the produced Hf-based oxide film is used as a gate insulating film, the amorphous Hf-based oxide film is crystallized or activated in the gate electrode during the activation annealing of the source, drain and gate electrodes of the transistor. There is a problem that impurities such as boron and phosphorus mixed are diffused and reach the channel portion of the transistor, thereby deteriorating the transistor characteristics.

It is an object of the present invention to provide C, H without requiring RTA processing or frequent cleaning processing.
It is an object of the present invention to provide a method for manufacturing a semiconductor device capable of efficiently forming an Hf-based oxide film having a small content of a specific element (impurity) such as a substrate on a substrate. Another object of the present invention is to provide a method for manufacturing a semiconductor device that saves process time and prevents the film surface from being contaminated. Further, nitrogen is mixed in the Hf-based oxide film to improve its thermal stability and suppress impurity diffusion.

Another object of the present invention is to provide a method of manufacturing a semiconductor device capable of suppressing the formation of a cumulative film formed inside a supply port when an amorphous thin film is formed on a substrate.

Another object of the present invention is to provide a semiconductor device manufacturing method capable of improving throughput when an amorphous thin film is formed on a substrate.

Another object of the present invention is to provide a method of manufacturing a semiconductor device that can reduce the maintenance cycle of the device when an amorphous thin film is formed on a substrate.

1st invention includes the film-forming process which forms a thin film on a board | substrate, and the active gas supply process which supplies the gas activated with the plasma with respect to the film | membrane formed in the film-forming process, The said film-forming process And the active gas supply step are repeated in the same reaction chamber a plurality of times in succession. Since the amorphous Hf-based oxide film is formed in the film forming process, it is easy to remove the specific element in the film. In addition, since the film formation step and the removal step are continuously performed, the specific element in the film formed in the film formation step can be quickly removed. In addition, since the film forming process and the removing process are repeated a plurality of times in succession, a film having a predetermined film thickness can be easily formed, and a case where a film having a predetermined film thickness is formed at a time and the removing process is performed. Thus, the removal amount of the specific element in the formed film can be increased.

According to a second invention, in the first invention, in the film formation step, a film formation gas is supplied to the substrate,
In the removing step, radicals are supplied to the substrate, and the film forming step and the removing step are performed in the same reaction chamber. In the film forming process, a Hf-based oxide film is formed on the substrate by supplying a film forming gas to the substrate. In the removing step, the specific element in the Hf-based oxide film is removed by supplying radicals to the substrate. When these film forming process and removing process are performed in the same reaction chamber, the temperature of the substrate is not lowered between the steps, so that the temperature raising time for processing the substrate again becomes unnecessary, and the temperature raising time of the substrate can be saved. , Processing efficiency is good. In addition, since the substrate stops in the same reaction chamber, the film formation surface is hardly contaminated.

According to a third invention, in the second invention, the film forming gas supplied to the substrate in the film forming step and the radical supplied to the substrate in the removing step are supplied from separate supply ports, respectively. It is a manufacturing method. Since the film forming gas and the radical are supplied from separate supply ports, it is possible to suppress the formation of a cumulative film also formed inside the supply port.

A fourth invention is a method of manufacturing a semiconductor device according to the third invention, wherein the film forming step and the removing step are performed while rotating the substrate. When the substrate is rotated, the substrate can be uniformly processed, so that both the film formation process and the removal process can be effectively performed.

In a fifth aspect based on the third aspect, when the film forming gas is supplied to the substrate in the film forming step, a non-reactive gas is supplied to the radical supply port, and the radical is supplied to the substrate in the removing step. In this case, a non-reactive gas is supplied to a film forming gas supply port. In this way, when a non-reactive gas, for example, an inert gas, is supplied from a supply port that is not involved in each step, it is possible to further suppress the formation of a cumulative film inside the supply port.

In a sixth aspect based on the second aspect, when supplying the film forming gas to the substrate in the film forming step, the supply of radicals used in the removing step is allowed to flow without stopping the reaction chamber, When the radical is supplied to the substrate in the removing step, the supply of the film forming gas used in the film forming step is allowed to flow so as to bypass the reaction chamber without stopping. Thus, if the reaction chamber is bypassed without stopping the supply of the radical in the film formation step and the film formation gas in the removal step, the film formation gas or Radicals can be supplied to the substrate. Therefore, throughput can be improved.

A seventh invention is a method of manufacturing a semiconductor device according to the first and second inventions, wherein an organic material is used in the film forming step. Even when an organic material containing a large amount of a specific element such as an impurity such as C or H is used, the film formation process and the removal process are continuously repeated a plurality of times, so that the specific element in the film can be effectively removed.

An eighth invention is a method of manufacturing a semiconductor device according to the first and second inventions, wherein an MMP-based material is used in the film forming step and oxygen is not used. When an organic raw material is used, oxygen is usually used together. However, when an MMP-based raw material is used, the amount of specific elements (impurities) such as C and H can be reduced when oxygen is not used.

A ninth invention is the method of manufacturing a semiconductor device according to the first and second inventions, wherein the removing step is a plasma treatment using oxygen. The specific element removal step can be efficiently performed immediately after the formation of the Hf-based oxide film by plasma treatment using oxygen, that is, oxygen radicals generated by the plasma.

A tenth invention is a method for manufacturing a semiconductor device according to the first and second inventions, wherein the removing step is a plasma treatment using nitrogen (N). The specific element removal step can be efficiently performed immediately after the Hf-based oxide film is formed by plasma treatment using nitrogen, that is, nitrogen radicals generated by the plasma. Further, nitrogen can be mixed into the oxide film formed in the film formation step. For example, in the case of an Hf silicate film, a film such as HfSiON can be formed.

In an eleventh aspect of the invention, in the tenth aspect, the concentration of nitrogen introduced into the deposited oxide film is changed in the depth direction of the film by applying strength to the plasma treatment using nitrogen in the removal step repeated a plurality of times. It can be changed to.

A twelfth aspect of the invention is a method of manufacturing a semiconductor device according to the first and second aspects of the invention, wherein at least the removing step is performed while rotating the substrate. Since it is performed while rotating the substrate, the specific element in the film can be removed quickly and uniformly.

According to the present invention, the film forming process for forming the Hf-based oxide film by the MOCVD method and the RPN process for performing the remote plasma nitrogen treatment on the formed film are continuously repeated a plurality of times. Nitrogen can be effectively mixed therein.

Embodiments of the present invention will be described below. In the embodiment, using the MOCVD method, Hf
A case where an amorphous HfO ₂ film (hereinafter simply referred to as an HfO ₂ film) is formed among the system oxide films will be described. Here, the difference between the CVD method and the ALD method of the present invention is as follows. In the ALD method, the processing temperature and pressure are low, and films are formed one atomic layer at a time. On the contrary,
The CVD method of the present invention has a higher processing temperature and pressure than the ALD method, and forms a thin film (several atomic layers to several tens of atomic layers) a plurality of times.

FIG. 1 is a schematic view showing an example of a single wafer CVD apparatus which is a substrate processing apparatus according to an embodiment. A radical generating unit 11, a substrate rotating unit 12, an inert gas supply unit 10, and a bypass pipe 14 are mainly added to the conventional reaction chamber 1 (FIG. 10).

As shown in the figure, a hollow heater unit 18 whose upper opening is covered with a susceptor 2 is provided in the reaction chamber 1. The heater 3 is provided inside the heater unit 18, and the substrate 4 placed on the susceptor 2 is heated by the heater 3. The substrate 4 placed on the susceptor 2 is, for example, a semiconductor silicon wafer or glass.

A substrate rotation unit 12 is provided outside the reaction chamber 1, and the substrate unit 4 on the susceptor 2 can be rotated by rotating the heater unit 18 in the reaction chamber 1 by the substrate rotation unit 12. The reason why the substrate 4 is rotated is to improve the film quality of the film formed on the substrate 4 by radicals introduced from the radical generating unit 11, that is, to quickly and uniformly remove impurities in the film within the substrate surface. .

A shower head 6 having a large number of holes 8 is provided above the susceptor 2 in the reaction chamber 1. The shower head 6 is divided into a film forming shower head portion 6a and a radical shower head portion 6b by a partition plate 15, and gas can be separately ejected in a shower form from the divided shower head portions 6a and 6b. Yes.

Outside the reaction chamber 1, a film forming raw material supply unit 9 for supplying a film forming gas and an inert gas supply unit 10 for supplying an inert gas as a non-reactive gas are provided. An organic material such as Hf- (MMP) ₄ is used as a film forming gas material. In addition, as the inert gas, Ar, He, N
₂ etc. are used. The raw material gas supply pipe 5b provided in the film forming raw material supply unit 9 and the inert gas supply pipe 5a provided in the inert gas supply unit 10 are unified and connected to the film forming shower head section 6a. A raw material supply pipe 5 is provided. The raw material supply pipe 5 is formed on the substrate 4 with HfO.
_In a film forming process for forming _two films, a mixed gas of a film forming gas and an inert gas is supplied to the film forming shower head portion 6 a of the shower head 6. The source gas supply pipe 5b and the inert gas supply pipe 5a are respectively provided with valves 21 and 20, and by opening and closing these valves 21 and 20, the supply of the mixed gas of the film forming gas and the inert gas is controlled. It is possible.

In addition, a radical generation unit 11 that generates radicals is provided outside the reaction chamber 1. The radical generating unit 11 is constituted by a remote plasma processing unit. The radical used in the removal step is preferably, for example, an oxygen O ₂ radical when an organic material such as Hf- (MMP) ₄ is used as a raw material. This is because oxygen radicals can efficiently remove impurities such as C and H immediately after the formation of the HfO ₂ film. The radical used in the cleaning process is preferably a ClF ₃ radical.

A gas supply system 37 is provided on the upstream side of the radical generating unit. This gas supply system 3
The 7, oxygen _{(O 2)} oxygen supply unit 38 for supplying, and ClF ₃ is connected ClF ₃ supply unit 39 supplies a specific element in the film formed in the film forming step (C, impurities such as H ) Is selectively supplied to the radical generating unit 11 with oxygen O ₂ used in the removing step for removing the) and ClF ₃ used in the cleaning step for removing the accumulated film formed on the structure other than the substrate. ing.

A radical supply pipe 13 connected to the radical shower head unit 6b is provided on the downstream side of the radical generation unit 11, and oxygen radicals or chlorine fluoride is added to the radical shower head unit 6b of the shower head 6 in a removal process or a cleaning process. It is designed to supply radicals. Further, the radical supply pipe 13 is provided with a hull 24 and the valve 24 is opened and closed to control the supply of radicals.

A film forming shower head 6 including a raw material supply pipe 5 and a radical supply pipe 13 provided in the reaction chamber 1.
a and the radical shower head unit 6a constitute separate supply ports for supplying the film forming gas supplied to the substrate 4 in the film forming process and the radical supplied to the substrate 4 in the removing process.

An exhaust port 7 a is provided in the reaction chamber 1, and the exhaust port 7 a is connected to an exhaust pipe 7 that communicates with an abatement apparatus. The exhaust pipe 7 is provided with a raw material recovery trap 16 for recovering the film forming gas raw material. This raw material recovery trap 16 is used in common for the film forming process and the removing process. The exhaust port 7a and the exhaust pipe 7 constitute an exhaust system.

Further, the source gas supply pipe 5b and the radical supply pipe 13 have a source gas bypass pipe 14a and a radical bypass pipe 14b (these are simply referred to as a bypass pipe 14) connected to a source recovery trap 16 provided in the exhaust pipe 7. Each is provided. Valves 22 and 23 are provided in the source gas bypass pipe 14a and the radical bypass pipe 14b, respectively. Thus, when supplying the film forming gas to the substrate 4 in the reaction chamber 1 in the film forming process, the radical bypass pipe 14b and the raw material are bypassed so as to bypass the reaction chamber 1 without stopping the supply of radicals used in the removing process. The exhaust gas is exhausted through the recovery trap 16. Further, when supplying radicals to the substrate 4 in the removal step,
The supply of the film forming gas used in the film forming process is exhausted through the raw material bypass pipe 14a and the raw material recovery trap 16 so as to bypass the reaction chamber 1 without stopping.

Then, a film forming process for forming an HfO ₂ film on the substrate 4 in the reaction chamber 1, and impurities such as C and H, which are specific elements in the HfO ₂ film formed in the film forming process, are used in the radical generation unit 11. A control device 25 is provided for controlling the removal process to be removed by the plasma treatment to be repeated a plurality of times continuously by controlling the opening and closing of the valves 20 to 24 and the like.

Next, using the substrate processing apparatus having the configuration as shown in FIG.
A procedure for depositing an O ₂ film is shown.

First, the substrate 4 is placed on the susceptor 2 in the reaction chamber 1 shown in FIG. 1, and power is supplied to the heater 3 while rotating the substrate 4 by the substrate rotating unit 12, and the temperature of the substrate 4 is set to 350 to 350. 5
Heat uniformly to 00 ° C. The substrate temperature depends on the reactivity of the organic material used, but Hf
In-(MMP) ₄ , the range of 390-450 degreeC is good. Further, when the substrate 4 is transported or heated, the valve 20 provided in the inert gas supply pipe 5a is opened, and an inert gas such as Ar, He, N ₂ or the like is always allowed to flow, thereby causing particles and metal contaminants. Can be prevented from adhering to the substrate 4.

Thereafter, the film forming process is started, the valve 21 provided in the source gas supply pipe 5b is opened, and an organic material, for example, Hf- (MMP) ₄ gas is supplied from the film forming source supply unit 9 to the film forming shower head unit 6a.
Is supplied onto the substrate 4. Also at this time, the valve 20 is kept open, and an inert gas (N ₂ or the like) is always supplied from the inert gas supply unit 10 to stir the film forming gas. When the film forming gas is diluted with an inert gas, it becomes easy to stir. The film forming gas supplied from the raw material gas supply pipe 5b and the inert gas supplied from the inert gas supply pipe 5a are mixed in the raw material supply pipe 5 and led to the film forming shower head section 6a as a mixed gas. Then, it is supplied in a shower form onto the substrate 4 on the susceptor 2 via a large number of holes 8.

By supplying the mixed gas for a predetermined time, first, an HfO ₂ film as an interface layer (first insulating layer) with the substrate 4 is formed to 15 Å. Next, the source gas supply pipe 5b
And the valve 22 provided in the source gas bypass pipe 14a is opened, and the supply of the film forming gas is exhausted by bypassing the reaction chamber 1 with the source gas bypass pipe 14a. Therefore,
The supply of the deposition gas is not stopped.

Then, the removal process is started, the valve 24 provided in the radical supply pipe 13 is opened, and oxygen radicals are supplied from the radical generation unit 11 onto the substrate 4 via the radical shower head 6b. During this time, the substrate 4 is kept at a predetermined temperature (the same temperature as the film forming temperature) by the heater 3 while rotating, so that impurities such as C and H can be quickly and uniformly removed from the 15 angstrom HfO ₂ film.

Thereafter, the valve 24 provided in the radical supply pipe 13 is closed, and the radical bypass pipe 14b
By opening the valve 23 provided in the base, oxygen radicals are supplied to the radical bypass pipe 14.
Bypass with b and exhaust. Accordingly, the supply of oxygen radicals is not stopped. Then, the film forming process is started again, the valve 22 provided in the source gas bypass pipe 14 is closed, and the valve 21 provided in the source gas supply pipe 5b is opened, so that the film forming gas passes through the film forming shower head 6a. The substrate 4 is supplied and a 15 angstrom HfO ₂ film is deposited on the substrate 4.

The HfO ₂ film having a predetermined film thickness with very little CH and OH mixing can be formed by a cycle process in which HfO ₂ film formation → impurity removal process → HfO ₂ film formation →... Is repeated a plurality of times.

By the way, the merit of forming an amorphous thin film and maintaining the amorphous state is as follows. Because the amorphous state has many gaps (scaly state)
It is easy to remove impurities such as C and H in the film. Conversely, the polycrystalline state is a state in which there are no gaps, so it becomes difficult to remove C, H, and the like. In addition, leakage current is less likely to flow in the amorphous state than in the polycrystalline state.

In order to perform the self-cleaning process of the accumulated film by the cleaning gas radical, the radical generation unit 11 introduces a cleaning gas (Cl ₂ , ClF _3, etc.) into the reaction chamber 1 as a radical. Here, the self-cleaning is a process of removing the accumulated film by reacting the cleaning gas with the accumulated film in the reaction chamber 1, converting it into metal chloride and volatilizing it, and exhausting it.

C and H contained in the HfO ₂ film (film thickness 10 mm) formed by such a cycle process
As shown in FIG. 2, the amount of impurities can be greatly reduced as the number of cycles increases.
The horizontal axis indicates the number of cycles, and the vertical axis indicates the total amount of C and H (arbitrary units). The number of cycles is 1
This corresponds to the conventional method.

According to FIG. 2, when the HfO ₂ film thickness is 10 nm, Hf such as CH and OH is obtained in about 7 cycles.
Since the effect of reducing the amount of impurities in the O ₂ film is lost, in the embodiment, 15 per cycle.
Thin film formation of about angstrom or less is considered effective.

The merit of repeating the HfO ₂ film formation → RPO process a plurality of times is as follows. Where RP
The O (remote plasma oxidation) process is a remote plasma oxidation process in which a film is thermally oxidized in an oxygen radical atmosphere obtained by decomposing an oxygen-containing gas (O ₂ , N ₂ O, NO, etc.) by plasma.

RPO processing on the HfO ₂ film, which is good coverage formed for deep trench when carrying out the (C, impurity removal processes such as H), thick HfO ₂ film at a time, for example RPO from the 100 angstroms formed When the process is performed, it becomes difficult for oxygen radicals to be supplied to the portion b in FIG. This is because in the process of oxygen radicals reaching b, the probability of reacting with C and H at the site a in FIG. 7 is high (because the film thickness is as thick as 100 angstroms and the amount of impurities is large accordingly) This is because the amount of radicals reaching b is relatively reduced.
Therefore, it becomes difficult to perform uniform C and H removal in a short time.

On the other hand, when forming a 100 angstrom HfO ₂ film, HfO ₂ film formation → R
When the PO process is performed in seven steps, the RPO process is performed with HfO ₂ per 15 angstroms.
It is only necessary to perform the C and H removal process only on the film. In this case, since the probability that oxygen radicals react with C and H at the site a in FIG. 7 does not increase (because the film thickness is as small as 15 angstroms and the amount of impurities is small), the radicals reach evenly to b. Will be. Therefore, uniform C and H removal can be performed in a short time.

Preferred film forming conditions when Hf- (MMP) ₄ is used are as follows. The temperature range is 400 to 450 ° C., and the pressure range is about 100 Pa or less. Regarding the temperature, when the temperature is lower than 400 ° C., the amount of impurities (C, H) taken into the film increases rapidly. When the temperature is higher than 400 ° C., the impurities are easily detached and the amount of impurities taken into the film is reduced. 4
If it is higher than 50 ° C., the step coverage becomes worse. Good step coverage can be obtained when the temperature is 450 ° C. or lower. Moreover, an amorphous state can also be maintained.

As for the pressure, for example, if the pressure is higher than 1 Torr (133 Pa), the gas becomes a viscous flow, and the gas does not enter into the depth of the groove. However, by setting the pressure to about 100 Pa or less, a molecular flow without stickiness can be obtained, and the gas reaches the depth of the groove.

In addition, RPO (removal step) that is performed continuously after the film formation step using Hf- (MMP) ₄ is performed.
The preferable conditions for the remote plasma oxidation process are a temperature range of about 390 to 450 ° C. (
The pressure range is about 100 to 1000 Pa. Further, the O ₂ flow rate for radicals is 100 sccm, and the inert gas Ar flow rate is 1 slm.

The film forming step and the removing step are preferably performed at substantially the same temperature (the heater set temperature is preferably kept constant without being changed). By not causing temperature fluctuations,
This is because particles due to thermal expansion of peripheral members such as a shower head and a susceptor are less likely to be generated, and metal jump-out (metal contamination) from metal parts can be suppressed.

By the way, when the raw material adsorbed inside the shower head 6 reacts with oxygen radicals, a cumulative film is also formed inside the shower head 6. In order to suppress the formation of this accumulated film, the shower head 6 is preferably divided into two (6a, 6b) by the partition plate 15 as described above. By partitioning the shower head 6 to which the source gas and oxygen radicals are supplied, the reaction between the source material and oxygen radicals can be effectively prevented.

In addition to partitioning the shower head 6, in the case of further flowing a film forming gas to the substrate 4, an inert gas is flowed from the radical supply side (radical generation unit 11) to the radical shower head portion 6 b, and oxygen radicals are directed to the substrate 4. When flowing, the material supply side (film formation material supply unit 9,
It is preferable to flow an inert gas from the inert gas supply unit 10) to the film forming shower head 6a. Thus, the shower head portions 6b, 6 on the side not used in the film forming step and the removing step, respectively.
If an inert gas is allowed to flow through a, it is possible to more effectively suppress the formation of a cumulative film inside the shower head 6.

Further, a raw material recovery trap 16 for recovering the raw material is installed in the exhaust pipe 7 as shown in FIG.
Since the bypass pipe 14 is connected to the raw material recovery trap 16, it is possible to convert the trapped liquid raw material into a solid with oxygen radicals and prevent the raw material from flowing into the exhaust pump (not shown) due to revaporization. It is. As a result, the raw material recovery rate is improved, and an exhaust pump and a detoxifying device (
It is possible to reduce the inflow of the raw material to (not shown), and to greatly extend the maintenance cycle of the substrate processing apparatus.

Next, a HfO ₂ film obtained by 7 cycles treatment (invention) of the embodiment, for the HfO ₂ film obtained by one cycle treatment (conventional method), the electrical insulation properties before and after RTA process Figure 3 shows. The horizontal axis represents the electric field (arbitrary unit) applied to the HfO ₂ film (10 nm), and the vertical axis represents the leakage current (arbitrary unit). Here, the RTA process is a process in which a thermal annealing process is performed at a high speed at atmospheric pressure (in an O ₂ atmosphere) while heating the substrate to around 700 ° C. In the figure, conventional HfO represents an HfO ₂ film obtained by one cycle treatment, and HfO of the present invention represents an HfO ₂ film obtained by seven cycle treatment. RTA-free means RTA
“Before processing” and “with RTA” indicate that after RTA processing. According to FIG. 3, the one obtained by one-cycle processing (conventional HfO (without RTA)) has a large amount of CH and OH mixed, and the insulation characteristics change greatly before and after RTA. The insulating film obtained by the 7-cycle treatment (the present invention HfO (without RTA)) has a small amount of CH and OH, so that the insulation characteristics at the initial stage (state where no electrical stress is applied for a long time) are almost the same before and after the RTA. I understand that there is no. From this, by performing the cycle processing of the present embodiment,
RTA required for improving the electrical insulation of the thin film and ensuring its stability can be reduced.

Next, FIG. 9 shows a cluster device configuration in the embodiment, and it will be explained that this configuration can reduce the RTA processing.

The cluster apparatus includes a substrate transfer chamber 40 provided with a substrate transfer robot 41, a load lock chamber 42 for loading / unloading substrates to / from the apparatus, and a first reaction chamber 4 for surface-treating (RCA cleaning, etc.) the substrates.
3. A second reaction chamber 44 for forming an HfO ₂ film as a CVD reaction chamber shown in FIG. 1 and a third reaction chamber 45 for forming an electrode on the thin film are provided.

In the conventional cluster apparatus configuration (see FIG. 11), the substrate surface treatment is performed in the first reaction chamber 33, the HfO ₂ film is formed in the second reaction chamber 34, the RTA treatment is performed in the third reaction chamber 35, and the fourth reaction is performed. Chamber 3
6 formed an electrode. On the other hand, according to the embodiment of FIG. 9, after carrying the substrate into the load lock chamber 42 from outside the apparatus, the substrate surface treatment such as RCA cleaning is performed in the first reaction chamber 43,
HfO ₂ film formation and impurity removal are repeated in the second reaction chamber 44 (HfO ₂ film formation → impurity removal → HfO ₂ film formation → impurity removal →...) To form an HfO ₂ film having a predetermined thickness. Electrodes (poly-Si thin film formation and thermal annealing treatment) are formed in the reaction chamber 45. Then, the substrate on which the electrode is formed is carried out of the apparatus from the load lock chamber 42.

FIG. 4 shows the HfO of the substrate obtained by the cluster device configuration of the conventional example and the embodiment described above.
_The figure which compared the electrical property of _two films | membranes is shown. The horizontal axis indicates the capacitance (arbitrary unit), and the vertical axis indicates the leakage current (arbitrary unit) when the HfO ₂ film thickness is about 5 nm, about 10 nm, and about 15 nm.
From the figure, the characteristics obtained by the cluster apparatus of the embodiment shown in FIG. 9 (7 cycles of HfO ₂ film) are obtained from the characteristics of the HfO ₂ film obtained by the conventional tarasque apparatus (1 cycle process) shown in FIG. Indicates that it is better. This result shows that the RTA process is not required, and such a cluster configuration that does not require the RTA process can be obtained from the HfO ₂ film in the second reaction chamber 44 of FIG. This is considered to be because the CH and OH removal processing is sufficiently performed by the process according to the present embodiment.

Therefore, in this embodiment, the reaction chamber for RTA can be omitted from the cluster apparatus, and the configuration can be simplified. In addition, since RTA processing for removing CH and OH is not performed,
Without surface state of the HfO ₂ film loses flatness, HfO ₂ film that does not become lower partial insulation and its stability was crystallized.

Further, since the amount of C and H contained in the HfO ₂ film formed on the substrate can be significantly reduced by repeating the film forming process and the removing process a plurality of times in succession, the Hf produced continuously
It becomes possible to keep the quality of the O ₂ film constant. Therefore, it is not necessary to frequently perform the removal process of the accumulated film by self-cleaning as compared with the conventional case, and the production cost can be reduced.

Incidentally, when forming the HfO ₂ film, there is a case where oxygen O ₂ is mixed in the mixed gas. This is because it is generally better to add O ₂ in consideration of the adhesion to the substrate and the film formation rate. However, for Hf- _{(MMP) 4,} was experimented with and has _{O 2} without and _{O 2,} who towards _{O 2} without the improved quality reduces contamination of impurities, it was put _{O 2} conversely It has been found that the amount of impurities mixed in increases and the film quality deteriorates. Therefore, Hf as a film forming gas source
-In the embodiment using (MMP) ₄ , it is preferable not to mix oxygen O ₂ to form CH, OH in the film.
Therefore, oxygen O ₂ is not mixed.

As described above, in this embodiment using Hf- (MMP) ₄ as a film forming material, the amount of impurities mixed is reduced and the film quality is improved when oxygen O ₂ is not mixed. When Hf- (MMP) ₄ is used, the mechanism by which the amount of impurities mixed can be reduced without supplying oxygen is as follows. Comparison of ideal chemical reaction formulas with and without Hf- (MMP) ₄ oxygen is as follows.

A. When an ideal reaction occurs without oxygen (ideal self-decomposition reaction with heat alone):
2Hf [OC (CH ₃ ) ₂ CH ₂ OCH ₃ ] ₄ → 2Hf (OH) ₄ + 8C (CH ₃ ) ₂ CH ₂ OCH ₂ ↑
2Hf (OH) ₄ → 2HfO ₂ + 2HfO ₂ + 4H ₂
B. If an ideal reaction occurs with oxygen (complete combustion):
Hf [OC (CH ₃ ) ₂ CH ₂ OCH ₃ ] ₄ + 24O ₂ → HfO ₂ + 16CO ₂ ↑ + 16CO ₂ ↑ + 22H ₂ O ↑
However, ↑ means a volatile substance.
In the above reaction chemical formula, the numerical value in upper case is considered as the molar ratio of the raw material on the substrate as it is, without oxygen,
HfO ₂ : (other impurities) = 2: (8 + 4) = 1: 1
It becomes. With oxygen,
HfO ₂ : (other impurities) = 1: (16 + 22) = 1: 38.

Therefore, the total number of moles of impurities generated when 1 mol of HfO ₂ is produced is larger when oxygen is present.

Furthermore, when comparing the number of cleavages in the chemical formula for breaking each bond,
Without oxygen: 4 cuts of O-C, C-H, and 0-H each, total 12 times With oxygen: 12 times of O-C, 44 times of C-H, total of 56 cuts As the number of times increases, the amount of radicals increases, so that impurities are easily mixed into the film.

In conclusion, the film was formed without oxygen, and the above [C (CH ₃ ) ₂ CH ₂ OCH ₃ ] was volatilized at a temperature that did not decompose,
An HfO ₂ film may be formed.

In addition, it is preferable to form the HfO ₂ film without oxygen using FIGS. 5 and 6 in which the influence on the thin film due to the amount of O ₂ added is measured using FTIR (Fourier transform infrared spectroscopy). To do.

FIG. 5 shows the film quality characteristics of the thin film compared with and without oxygen. The horizontal axis represents the wave number (cm ⁻¹ ), and the vertical axis represents the absorbance at the film forming temperatures of 425 ° C. and 440 ° C. When oxygen is present, the oxygen flow rate is 0.5 SLM. In particular, as shown in FIG.
By exciting a stretch mode near cm ⁻¹ , Hf—O—H
The number of X—O—X bonds indicating f bonds is greater when oxygen is present than when oxygen is absent. That is, the film quality is good.

FIG. 6 shows the characteristics of the amount of impurities contained in the film compared with and without oxygen. The horizontal axis represents the wave number (cm ⁻¹ ), and the vertical axis represents the absorbance at the film forming temperatures of 425 ° C. and 440 ° C. When oxygen is present, the oxygen flow rate is 0.5 SLM. As shown in the figure, by exciting the stretch and wagging modes, the amount of impurities (—OH, C—H, C—O) is compared with that without oxygen when oxygen is present. As a result, the film thickness with oxygen was found to be about five times that of the film without oxygen.

In the embodiment, after the HfO ₂ film is formed in the second reaction chamber 44, the electrode is formed in the third reaction chamber 45 in the same cluster apparatus. As described above, when the HfO ₂ film is formed (second reaction chamber) and the electrode formation (third reaction chamber) is performed in the same apparatus,

(1) After the substrate is taken out from one apparatus and loaded into another apparatus, it is possible to save a reheating time for heating the substrate again.
(2) Since the film is densified by thermal annealing at 700 ° C. or higher at the time of electrode formation, the film surface is hardly contaminated.
(3) An electrode can be formed with the surface of the HfO ₂ film kept clean.
There is such a merit.
However, after forming the HfO ₂ film (second reaction chamber), the substrate may be taken out of the apparatus and the electrode may be formed by another apparatus. However, when forming the electrode with another device like this,

(1) When the substrate is taken out of the apparatus, a heating time for heating the substrate again is required, and wasteful processing time is generated.
(2) The surface of the HfO ₂ film formed at a low temperature is likely to be contaminated by the atmosphere outside the apparatus, and is likely to change with time (causes deterioration of the electrical characteristics of the device).
There are disadvantages.

Even in the case of the cluster apparatus shown in FIG. 9, the HfO ₂ film is formed (second reaction chamber 44).
Thereafter, for example, if the RTA treatment is performed in the third reaction chamber 45, there is no problem even if the subsequent electrode formation is performed by another apparatus. Generally, the higher the temperature, the smaller the gap between atoms, and the more difficult it is for contaminants (H ₂ O, organic substances, etc.) to diffuse into the HfO ₂ film. Therefore, the HfO ₂ film is annealed at a high temperature by the RTA process to be densified, so that it is difficult to be contaminated in the atmosphere outside the apparatus or changed with time.

The merit of performing the HfO ₂ film formation and the RPO process in the same reaction chamber is as follows.
When the HfO ₂ film is formed, the HfO ₂ film is also formed on the reaction chamber wall, shower head, susceptor and the like. This is called a cumulative film. Hf without RPO treatment when run in separate reaction chamber
In the O ₂ film reaction chamber, C and H come out of the accumulated film and the reaction chamber is contaminated. Further, the amounts of C and H coming out of the accumulated film increase as the thickness increases.
Therefore, it is difficult to keep the C and H amounts of all the substrates to be processed constant.

On the other hand, when the HfO ₂ film formation and the RPO process are performed in the same reaction chamber,
Not only C and H in the film formed on the substrate, but also C and H from the accumulated film deposited in the reaction chamber.
Can be removed (cleaning effect), the C and H contents can be kept constant for all substrates.

Further, the bypass pipe 1 is used without stopping the radical / gas used in the next step during the gas / radical supply.
The reason for exhausting air from 4 is as follows. Preparation is necessary for the supply of the raw material gas / radical, and it takes time until the supply starts. Therefore, during the treatment, the supply of the raw material gas / radical is always continued without being stopped, and is exhausted from the bypass pipe 14 when not in use. Thereby, the supply of the source gas / radical can be started immediately by simply switching the valves 21 to 24 at the time of use, and the throughput can be improved.

In the above-described embodiment, the case where the HfO ₂ film is formed on the substrate has been described, particularly in the following configurations (1) to (3).
(1) The film forming gas used in the film forming process and the radical used in the removing process are supplied by different shower heads so that they are not mixed.
(2) While supplying the gas or radical, the radical or gas used in the next step is exhausted from the bypass pipe, and the supply of the radical or film forming gas used in the next step can be started immediately by simply switching the valve. .
(3) Simplify maintenance by using a common trap for the film formation process and the removal process.
However, the present invention is not limited to the HfO ₂ film with respect to the above three constituent points. For example, the present invention can be applied to other types of films such as a Ta2O5 film.

FIG. 8 shows various shapes of the shower head 6 applied to FIG. FIG.
The showerheads of various shapes shown in (e) have the same configuration in the following points. The shower head 6 includes a shower plate 19 having a large number of holes 8, a back plate 17 and a peripheral wall 26, a gas space 27 formed therein, and a gas space 27 that divides the gas space 27 into two shower head portions 6a and 6b. The partition plate 15 is divided. The raw material supply pipe 5 and the radical supply pipe 13 are connected to the two shower head portions 6a and 6b from the back plate 17 side of the shower head 6 thus configured, respectively.

In FIG. 8A, the gas space 27 has a disk shape, and the partition plate 15 has a disk shape.
The shower head parts 6a and 6b are provided on the left and right sides. FIG.
In (b), the gas space has a disc shape, but the partition plate 15 is provided concentrically with the disc-like gas space, and the shower head portions 6a and 6b are provided in a coaxial double tube. .

In FIGS. 8A and 8B described above, the basic shape of the shower head 6 is a point-symmetrical circle. However, in this embodiment, the substrate is rotated. It is also possible to make a shape such as a semicircle or a rectangle. FIG. 8C to FIG. 8E show such an example.

In FIG. 8C, the gas space has a semi-disc shape, the partition plate 15 is provided in the radial direction of the semi-disc-shaped gas space, and the shower head portions 6a and 6b are provided on the left and right. FIG.
), The gas space has a rectangular disk shape, the partition plate 15 is provided in the central portion, and the shower head portions 6a and 6b are provided on the left and right. FIG. 8 (e) has a quadrangular disk shape, the partition plate 15 is provided at the center, and the shower head portions 6a and 6b are provided on the left and right.
Thus, the shower head 6 can be configured in various shapes.

FIG. 12 shows a new MOCVD using periodic remote plasma oxidation in this embodiment.
A method film forming sequence (a procedure of a cycle method in which film formation by MOCVD and RPO are repeated a plurality of times) is shown. Here, processing was performed using the substrate processing apparatus of FIG.

When a silicon wafer as a substrate is placed on the susceptor in the reaction chamber and the temperature of the silicon wafer is stabilized, (1) gaseous Hf- (MMP) ₄ raw material (MO-P) vaporized by a vaporizer
recursor) is introduced into the reaction chamber along with dilution N ₂ for ΔMt seconds. (2) Then
The introduction of gaseous Hf- (MMP) ₄ raw material is stopped, and the reaction chamber is purged with dilution N _{2 for} ΔIt seconds. (3) After purging the reaction chamber, oxygen (Remote Plasma Oxygen) activated by the remote plasma unit is introduced into the reaction chamber for ΔRt seconds. During this time, dilution N ₂ continues to be introduced. (4) After the introduction of oxygen activated by the remote plasma is stopped, the reaction chamber is again purged with dilution N _{2 for} ΔIt seconds. (5
) In the steps (1 cycle) from (1) to (4), the film thickness is a desired value (thickness).
It is repeated until n is reached (n cycle). In this embodiment, the flow rate of Hf- (MMP) ₄ is 0.05 g / min, and the flow rate of the dilution gas N ₂ is 0.5 SLM (standard l).
italy per minute), the flow rate of oxygen introduced into the remote plasma unit was 0.1 SLM. The pressure in the reaction chamber is determined by the APC (auto) provided in the exhaust system.
The pressure was controlled at 100 Pa by a pressure control) valve. In order to measure the deposition (deposition rate) of the HfO ₂ film, the natural oxide film on the surface of the silicon substrate was removed with a 1% diluted HF solution.

FIG. 13 shows current-voltage characteristics (IV characteristics) and capacitance-voltage characteristics (C-V characteristics).
2 shows an n-MOS capacitor structure for measuring and a manufacturing process flow thereof.

For the manufacture of the n-MOS capacitor, first, a p-type silicon wafer separated by LOCOS method was used. Prior to the formation of the HfO ₂ film, the silicon surface was etched with a 1% diluted HF solution to remove the natural oxide film and contaminants (Cleaning-D
HF + DIW + IPA). Subsequently, the silicon surface was nitrided (Surface Nitride) by performing thermal thermal annealing at 600 ° C. for 30 seconds in an NH 3 atmosphere. Then, the above cycle processing (
HfO ₂ deposition by MOCVD via cyclic RPO)
Then, an HfO ₂ film was formed and annealed at 650 ° C. for 15 minutes in a N ₂ atmosphere (post deposition annealing). Subsequently, a TiN film having a thickness of 80 nm was formed at 650 ° C. using TiCl 4 and NH 3 to form a gate electrode.
Growing by VD (chemical vapor deposition) method (Ga
(te Electrode-CVD TiN), a mask electrode by photolithography, and a gate electrode of a MOS capacitor having an area of 1000 to 10000 μm ² was formed by etching. The equivalent oxide thickness (EOT) of the HfO ₂ film was determined using a CVC program developed by NCSU on a CV curve measured with an electrode having an area of 10,000 μm ² . The IV characteristics were measured at a temperature of 100 ° C. using an electrode having an area of 1000 μm ² . In addition, in order to examine the quality of the film, TDS (thermal desorption spectrosco)
py) characteristics and SIMS (Secondary Ion Mass Spectrosco)
(py) Profile was also measured. Also, in order to investigate the crystal structure of the film, a high-resolution TEM
(HRTEM (cross-section high-resolution tra
nsmission electron microscopy)) images were also observed.

FIG. 14 shows the substrate temperature dependence of the growth rate of the HfO ₂ thin film formed by using the above cycle method (black points in the figure). The vertical axis is the growth rate (Growth Rate), and the horizontal axis is the temperature (T
temperature). Each step time of ΔMt, ΔIt, and ΔRt in the cycle method was 30 seconds. As a comparative example, HfCl ₄ and H ₂ performed by Cho et al.
Also shown is data (open dots in the figure) in which HfO ₂ is formed by ALD using O.
The film formation rate is expressed in units of nm / min for comparison with the data of Cho et al.

In the case of ALD using HfCl ₄ and H ₂ O, the film formation rate is 1 for the substrate temperature (growth temperature).
1.2 nm / min to 0.36 nm as the temperature is changed (increased) from 80 ° C. to 400 ° C.
/ Min. This is because in the case of ALD, the amount of raw material adsorbed on the wafer surface decreases as the substrate temperature is increased. However, in the case of the new cycle method devised by the present inventors, the film formation rate increases from 0.3 nm / min (0.6 nm / cycle) to 1 as the substrate temperature (growth temperature) is increased from 300 ° C. to 490 ° C. .5 nm / min (
3nm / cycle). This is because the self-decomposition of the raw material is promoted by increasing the film forming temperature. In addition, since it takes time until the flow rate is stabilized in the used liquid mass flow controller, it is known that only ΔS of 30 seconds actually contributes to the film formation for 8 seconds. Therefore, the film formation rate is lower than that of ALD at low temperatures. If the time that the raw material actually contributes to the film formation can be increased, the film formation speed is AL even at a low temperature.
It can be larger than D.

Using a cycle method, an HfO ₂ thin film having a film thickness of 30 nm formed with different number of cycles was changed to T
Assessed by DS. FIGS. 15A, 15B, and 15C show TDS spectra of hydrogen, H ₂ O, and CO, respectively, of the HfO ₂ thin film. 4 in the same figure (a), (b), (c)
The two spectra relate to HfO ₂ thin films deposited by the cyclic method at 425 ° C. at 1, 10, 20, and 40 cycles, respectively. The step times of 1, 10, 20, and 40 cycle processing are 1200, 120, 60, and 30 seconds, respectively. In other words, films formed in 1, 10, 20, 40 cycles are 30, 3, 1.5, respectively.
The RPO process is performed every 0.75 nm.

From FIG. 15 (a), it can be seen that the hydrogen desorption from the 10, 20, and 40 cycle samples is dramatically reduced compared to the one cycle sample. 15 (b) and (
From c), it can be seen that the desorption of CO hardly changes depending on the number of cycles, whereas the desorption of H ₂ O gradually decreases as the number of cycles increases. We compared the TDS spectra of samples that were previously RPO treated and those that were not,
It has been found that RPO after forming a HfO ₂ thin film is effective in reducing the mixing of hydrogen and H ₂ O. From these facts, it can be said that periodic RPO is effective in reducing the mixing of hydrogen and H ₂ O.

Further, in order to investigate the mechanism of mixing of impurities into the HfO ₂ thin film by _{Hf- (MMP) 4, Hf- (} MMP) 4 of the self-decomposition reaction was investigated as follows.

First, the Hf- (MMP) ₄ solution was allowed to stand in Ar gas at 300 ° C. for 5 hours, and then diluted with toluene to obtain a GC-MS (Gas Chromatography-Mass Sp).
analysis). The detected by-products were Hf- (MMP) ₄ , (CH ₃
) ₂ C = CHOCH ₃ (olefin), (CH ₃ ) ₂ CHCHO (isobutylaldehyde), (CH ₃ ) ₂ CHCH ₂ OH (isobutanol), C
H ₃ OH (methanol) and CH ₃ C (═O) CH ₃ (acetone). Olefin is produced by separation of HfO-C bond and hydrogen (H) bonded to carbon (C) at β-position of MMP. Isobutylaldehyde, isobutanol, methanol, and acetone are thought to be formed by decomposition of H-MMP and olefin. As a reaction model of Hf- (MMP) ₄ , the following equation is considered appropriate.
Hf (MMP) 4 → Hf (OH) + 4Olefin
Or
_{Hf (MMP) 4 → HfO 2} + 2H (MMP) + 2Olefin
Here, from the first equation, it is expected that hydrogen easily enters HfO _{2 formed} by MOCVD using Hf- (MMP) ₄ . This is also confirmed from the TDS spectrum of the HfO ₂ film formed by MOCVD measured previously, and is consistent with the fact. However, as shown in FIG. 15, in the film subjected to RPO treatment for every film thickness of 3 nm or less, almost no hydrogen is mixed. Therefore, RPO treatment completely oxidizes Hf (OH) as shown by It seems to be doing.
Hf (OH) + O * → HfO ₂ + 1 / 2H ₂
Or
2Hf (OH) + 3O * → 2 HfO 2 + H 2 O
Here, if the fourth type of reaction occurs on the surface of the deposited film, it is considered that the generated H ₂ O is exhausted from the surface of the thin film. However, since oxygen radicals (O *) also react with Hf (OH) present in the film, H ₂ O is taken into the HfO ₂ thin film. As a result, as shown in FIG. 15, the HfO ₂ film formed using the cycle method was used.
Even in a thin film, H ₂ O is present in the film, and the contamination due to the mixing of H ₂ O decreases as the film thickness subjected to the RPO treatment decreases every cycle.

FIG. 16 shows a sample of HfO ₂ (MO) formed at 425 ° C. by a conventional MOCVD method.
CVD (425 ° C.) and carbon ((a) carbon) and hydrogen ((b) hydrogen) of HfO ₂ sample (Cyclic Method at 300 ° C., 425 ° C.) deposited at 300 ° C. and 425 ° C. by a cyclic method. This shows the SIMS profile. The film thickness of these samples is about 5 nm. Samples at 300 ° C. and 425 ° C. were deposited in 100 and 10 cycles, respectively, with a step time of 30 seconds.

From FIG. 16, the mixing amounts of carbon (C) in the MOCVD method, 300 ° C. of the cycle method, and 425 ° C. of the cycle method are 1.4, 0.54, and 0.28 at. %. In addition, the amounts of hydrogen (H) mixed in the sample of MOCVD, 300 ° C. of the cycle method, and 425 ° C. of the cycle method are 2.6, 0.8, and 0.5 at. %. The result that the mixing of C and H is less in the cycle method than in the MOCVD method indicates that the cycle method is effective in reducing the mixing of C and H. According to the report of Kukli et al., The amount of hydrogen mixed in films formed by ALD at 300 ° C. and 400 ° C. is 1
. 5 and 0.5 at. %Met. This indicates that the amount of hydrogen mixed in the film formed by the cycle method is not inferior to that of ALD. The reason why the amount of carbon contamination is reduced is as follows. As shown in the first and second equations above, Hf
-(MMP) After introducing ₄ , olefin and H-MMP are produced. Various types of alcohols are also produced by the decomposition of olefin and H-MMP. Most of these by-products are exhausted from the surface of the thin film, but some is adsorbed on the thin film surface. Where RPO
These adsorbates are decomposed into CO, CO ₂ , H ₂ O and the like by the step, and are exhausted from the surface of the thin film by the next purge step. Chen et al. Formed a ZrO ₂ thin film in “pulse mode”, such as introducing MO raw material and oxygen through 15 seconds of exhaust, and the amount of mixed C was 0.1 at. %, But this is also considered to be caused by the decomposition of organic substances in the oxygen introduction step and the exhaust in the subsequent exhaust step. Further, it can be seen that the amount of impurities in the cycle method is decreased by increasing the film formation temperature. This is because the amount of adsorption of by-products decreases as the film formation temperature rises. For these reasons, it can be concluded that in the cycle method, it is better to shorten the material introduction time ΔMt and to increase the remote plasma irradiation time ΔRt. Further, it can be said that the film formation temperature should be higher as long as the raw material is not decomposed in the gas phase.

FIGS. 17A and 17B are HRTEM images of samples formed at 425 ° C. in 1 and 4 cycles with step times of 120 seconds and 30 seconds, respectively. Before forming the HfO ₂ thin film, an interface layer of 0.8 nm is formed by NH ₃ annealing.

17 (a) and 17 (b), the interface layers of 1 and 4 cycles are 1.7 nm and 1.6 n.
Therefore, it is considered that the step time of the RPO process does not affect the formation of the interface layer. However, in another experiment, it has been confirmed that the thickness of the interface layer formed between the underlayer and the HfO ₂ film can be made thinner than that by the conventional MOCVD method by the cycle method. From FIG. 17, the HfO ₂ thin film formed in one cycle is more crystallized,
It can be seen that the HfO ₂ thin film formed in 4 cycles has an amorphous structure. Kuk
reported that the ZrO ₂ film formed by ALD had an amorphous structure at 210 ° C., but crystallized at 300 ° C. In addition, Arik et al.
It was reported that the HfO ₂ film formed by 1 was crystallized. From these facts, the cycle method of the present invention can be said to be a method suitable for maintaining the film in an amorphous structure. When the film thickness uniformity was examined, it was confirmed that the film formation in 4 cycles was better than the film formation in 1 cycle.

FIG. 18 shows the relationship between the EOT of the HfO ₂ capacitor formed at 425 ° C. by the MOCVD method and the cycle method and the leakage current measured at −1V. The vertical axis represents leakage current (jg @ -1V
), The horizontal axis indicates EOT. Before the HfO ₂ thin film is formed, NH 3 annealing is performed to obtain 0.8
An interfacial layer of nm is formed. The film thickness of the HfO ₂ thin film formed by the cycle method is 2.3, 3.1, 3.8, and 4.6 nm, respectively. Of the HfO ₂ films formed by MOCVD with different film thicknesses, the CV characteristics were obtained only for those having a film thickness of 5 nm or more. White dots and black dots indicate the results when the films are formed by the MOCVD method and the cycle method, respectively.

FIG. 8 shows that the leakage current of the HfO ₂ thin film formed by the cycle method is 1/100 or less that of the film formed by the MOCVD method. The reason why the leakage current is reduced by the cycle method is that impurities in the HfO ₂ film are reduced and the film structure is in an amorphous state.

As described above, the present inventors have found an advantage of a new MOCVD method using periodic RPO. That is, in the case of the cycle method, it has been found that the amount of impurities contained in the film can be reduced by raising the film formation temperature and shortening the introduction time of the raw material. It has also been found that the film formed by the cycle method has an amorphous structure, and the cycle method is preferable for maintaining the amorphous structure. As a result, the leakage current of the HfO ₂ film was reduced. It was also found that the cycle method can improve the film thickness uniformity over the conventional MOCVD film formation, and further reduce the thickness of the interface layer formed between the film formation base and the HfO ₂ film. did.

In addition, in order to compare the film quality of Hf silicate film by MOCVD method using periodic RPO and the Hf silicate film by MOCVD method using RPN instead of the RPO, the SIMS The lateral profile was measured. FIG. 19 shows the profile in the depth direction of C, which is an impurity contained in the film, but there is almost no difference between the case of using RPO and the case of using RPN, and the effect of removing impurities is almost the same. It turns out that it is obtained. On the other hand, FIG. 20 shows the profile in the depth direction of N contained in the film. The difference in N concentration contained in the film is obvious due to the difference between RPO and RPN, and RPN is Hf. It can be seen that it works effectively during silicate film formation.

It is outline | summary explanatory drawing of the reaction chamber in embodiment. 6 is a graph showing the relationship between the number of cycles and the total amount of C and H impurities in the HfO ₂ film. It is a graph which shows the relationship between the number of cycles and an insulation characteristic. Is a graph showing electric characteristics of the HfO ₂ film by the cluster tool configuration in the embodiment and the conventional example. The coupling degree of HfO-Hf bond, in forming a HfO ₂ film, is a graph comparing with the case of forming by there oxygen as in forming without oxygen. The amount of impurities contained in the HfO ₂ film (-OH, C-H, C -O) a, in forming a HfO ₂ film, in FIG compared with the case of forming by there oxygen as in forming without oxygen is there. Is a sectional view showing a state in which a HfO ₂ film on the substrate. It is explanatory drawing which shows the various examples of the shower head shape by embodiment. It is a conceptual diagram which shows the cluster apparatus structure in embodiment. It is a conceptual explanatory view of a CVD reaction chamber in a conventional example. It is a conceptual diagram which shows the cluster apparatus structure in a prior art example. It is a figure which shows the film-forming sequence by the cycle process of MOCVD and RPO in an Example. It is a figure explaining the n-MOS capacitor structure used for the measurement of the CV characteristic and IV characteristic in an Example, and its manufacture procedure. It is a diagram showing a substrate temperature dependence of the growth rate of the HfO ₂ film formed by the cycle process. Hydrogen HfO ₂ film was deposited by changing the number of cycles _is a diagram showing the TDS spectra of H 2 O, CO. It is a figure which shows the SIMS profile of (a) carbon of the sample formed by the conventional MOCVD method and the cycle process in an Example, and (b) hydrogen. It is a figure which shows the HRTEM image of the sample formed in 1 cycle and 4 cycles. It is a diagram showing the relationship between HfO ₂ capacitors EOT and leakage current formed by cycling process in an embodiment conventional MOCVD method. It is a figure which shows the depth direction profile of C SIMS when the remote plasma oxygen is used for the impurity removal process and when the remote plasma nitrogen is used when the Hf silicate film is formed by the cycle process. It is a figure which shows the depth direction profile of N SIMS when the remote plasma oxygen is used for the impurity removal process and when the remote plasma nitrogen is used when the Hf silicate is formed by cycle processing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reaction chamber 4 Substrate 5 Raw material supply pipe 6 Shower head 7 Exhaust pipe 9 Film-forming raw material supply unit 11 Radical generation unit 14 Bypass pipe 15 Partition plate 16 Trap 25 Controller

Claims (1)

A film forming process for forming a thin film on the substrate; and an active gas supply process for supplying a gas containing nitrogen atoms activated by plasma to the film formed in the film forming process, the film forming process and the activity A method for manufacturing a semiconductor device, wherein the gas supply step is repeated a plurality of times continuously in the same reaction chamber.

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