JP2004158811A - Method for manufacturing semiconductor device - Google Patents

Abstract

An amorphous thin film having a low impurity content is efficiently formed on a substrate without requiring high-speed annealing or frequent cleaning.
A method for manufacturing a semiconductor device includes a film forming step and a modifying step. In the film forming process, a film forming gas from the film forming material supply unit 9 is supplied from the shower head 6 into the reaction chamber 1 to form an amorphous thin film including a hafnium oxide film (HfO ₂ film) on the rotating substrate 4. I do. In the reforming step, the radicals generated in the reactant activation unit 11 are supplied from the same shower head 6 that supplies the film-forming gas, and the specific elements that become impurities in the film formed in the film-forming step are removed. Remove. The controller 25 repeats the film forming step and the reforming step continuously in the same reaction chamber 1 a plurality of times to form a semiconductor device.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor device for forming a thin film on a substrate.
[0002]
[Prior art]
As one of semiconductor manufacturing processes, a CVD (Chemical Vapor Deposition) process of performing a predetermined film forming process on a surface of a substrate (a substrate to be processed on which a fine electric circuit pattern based on a silicon wafer, glass, or the like is formed) is provided. is there. This involves loading a substrate into an airtight reaction chamber, heating the substrate by a heating means provided in the chamber, causing a chemical reaction while introducing a film-forming gas onto the substrate, and forming a fine electric circuit provided on the substrate. This is to form a thin film uniformly on the pattern. In such a reaction chamber, a thin film is formed on a structure other than the substrate. In the CVD apparatus shown in FIG. 19, a shower head 6 and a susceptor 2 are provided in a 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 a raw material supply pipe 5 connected to a shower head 6, and is supplied onto the substrate 4 through a number of holes 8 provided in the shower head 6. The gas supplied onto the substrate 4 is exhausted through an exhaust pipe 7. The substrate 4 is heated by the heater 3 provided below the susceptor 2.
[0003]
As such a CVD apparatus, an amorphous HfO is formed by using an organic chemical material as a film forming material.₂There are a MOCVD (Metal Organic Chemical Vapor Deposition) device and an ALD (Atomic Layer Deposition) device for forming a film or an amorphous Hf silicate film (hereinafter simply referred to as an HfO film). Here, the difference between the CVD method performed by the MOCVD apparatus and the ALD method performed by the ALD apparatus is as follows. In the ALD method, the processing temperature and pressure are low, and a film is formed one atomic layer at a time. On the other hand, the CVD method has a higher processing temperature and pressure than the ALD method, and forms a film of about 1/6 atomic layer to several tens atomic layers at a time.
[0004]
As a film forming material,
Hf [OC (CH₃)₃]₄(Hereinafter, Hf- (OtBu)₄Abbreviated)
Hf [OC (CH₃)₂CH₂OCH₃]₄(Hereinafter, Hf- (MMP)₄Abbreviated)
However, MMP: methylmethoxypropoxy
Hf [O-Si- (CH₃)]₄
Etc. are used.
[0005]
Among them, for example, Hf- (OtBu)₄, Hf- (MMP)₄For example, many organic materials are in a liquid phase at normal temperature and normal pressure. Therefore, for example, Hf- (MMP)₄Is heated and converted into gas by vapor pressure for use. An HfO film is formed using such a raw material at a substrate temperature of 450 ° C. or lower, for example, by the CVD method. The HfO film contains a large amount of impurities such as CH and OH due to the organic material, which are several%. As a result, the category indicating the electrical properties of the substance belongs to a semiconductor or a conductor contrary to the intention to secure an insulator.
[0006]
In order to ensure the electrical insulation of such a thin film and its stability, the HfO film is made of O₂And N₂Attempts to remove C and H by performing high-speed annealing at about 650 ° C. to 800 ° C. in the atmosphere (hereinafter abbreviated as RTA [rapid thermal annealing]) to convert into a dense and stable insulator thin film Has been performed conventionally. Here, the purpose of the RTA is to remove impurities such as C and H in the film and to densify the film. Densification is not performed until crystallization, but is performed to reduce the average interatomic distance in the amorphous state.
[0007]
FIG. 20 shows a configuration of a cluster device in a conventional method of forming an HfO film. The substrate is carried into the load lock chamber 32 from outside 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 described above in the second reaction chamber 34. An HfO film is formed by a method equivalent to the conventional method, RTA processing (impurity removal, thermal annealing) 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 device from the load lock chamber 32. The loading / unloading is performed using a substrate transfer robot 31 provided in the substrate transfer chamber 30.
[0008]
In the third reaction chamber 35, when C and H are separated from the HfO film by the RTA process, there is a problem that the surface state loses flatness and changes to an uneven surface state. In addition, the HfO film is likely to be partially crystallized by the RTA treatment, so that a large current easily flows through the crystal grain boundary, and a problem arises that the insulating property and its stability are rather deteriorated. These problems are common to thin film deposition methods using MOCVD or ALD using all organic chemical materials, not only insulators.
[0009]
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 are mixed in this cumulative film. Therefore, 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 contained in the HfO film formed on the substrate gradually increases with the number of processed substrates. Will do. Due to this phenomenon, it is very difficult to make the quality of the HfO film produced continuously constant. In order to solve such an alarming event, it is necessary to frequently remove the accumulated film by self-cleaning, which is a factor that lowers productivity.
[0010]
In the conventional technique of forming an amorphous thin film as described above, the surface state of the HfO film loses flatness and changes to an uneven surface state by RTA treatment, or the HfO film is partially crystallized to generate crystal grain boundaries. However, there is a problem that the insulating property and the stability thereof are lowered.
[0011]
In addition, in order to keep the quality of a continuously produced HfO film constant, it is necessary to frequently carry out a cleaning process of a cumulative film containing a large amount of C and H, which lowers productivity. was there.
[0012]
Although it is not related to the HfO film, Ta thin film forming technology is used.₂O₅A method in which film formation and modification treatment are repeated a plurality of times in the same reaction chamber (for example, see Patent Document 1), formation of a high dielectric constant oxide film and a ferroelectric oxide film, and generation of plasma using an oxidizing atmosphere gas A method in which the heat treatment used is repeated a plurality of times in the same reaction chamber (for example, see Patent Document 2) and a method in which the formation of a metal film and the formation of a metal nitride film by introducing a nitriding gas are repeated a plurality of times (for example, see Patent Document 3) Are known.
[0013]
[Patent Document 1]
JP-A-2002-50622
[Patent Document 2]
JP-A-11-177057
[Patent Document 3]
JP-A-11-217672
[0014]
[Problems to be solved by the invention]
[0015]
However, even if an attempt is made to form a metal oxide film using the conventional techniques described in Patent Documents 1 to 3 described above, the metal oxide film is formed using a gas containing oxygen atoms in addition to the source gas during the film formation process. As a result, the specific element in the metal oxide film could not be effectively removed during the modification step, and the film was not sufficiently modified.
[0016]
In addition, since the film forming gas and the reactant are supplied from different supply ports, it is not possible to prevent foreign substances adhering to the inside of the supply port from falling onto the substrate. Removal of adsorbed by-products and cleaning gas was not sufficient.
[0017]
Further, when a thin film is formed and annealed by one apparatus, and then the substrate is taken out from one apparatus and an electrode is formed by another apparatus, there is a problem that the throughput is reduced.
[0018]
An object of the present invention is to provide a method for manufacturing a semiconductor device capable of effectively removing a specific element in a metal oxide film during a reforming step by solving the above-mentioned problems of the prior art. is there. Further, the object of the present invention is to prevent foreign substances adhering inside the supply port from falling onto the substrate, and to remove by-products and cleaning gas adsorbed inside the supply port by cleaning. Another object of the present invention is to provide a method of manufacturing a semiconductor device. Another object of the present invention is to provide a method for manufacturing a semiconductor device capable of quickly removing a specific element in a film containing Hf. Another object of the present invention is to provide a method for manufacturing a semiconductor device capable of improving throughput.
[0019]
[Means for Solving the Problems]
A first invention uses a raw material gas obtained by vaporizing a raw material containing oxygen atoms and metal atoms, and forms a metal oxide film on a substrate without using a gas containing oxygen atoms other than the raw material gas. And a reforming step of reforming a metal oxide film formed in a film forming step using a reactant different from the source gas is continuously repeated a plurality of times. In the film forming process, a metal oxide film is formed on the substrate without using a gas containing oxygen atoms other than the source gas, so that the source material containing oxygen atoms and metal atoms, which easily contains a specific element in the film, is vaporized. Even when the source gas is used, the specific element in the film can be effectively removed to easily modify the film. Further, since the film forming step and the modifying step are performed continuously, the specific element in the film formed in the film forming step can be quickly removed to modify the film. In addition, since the film forming step and the reforming step are continuously repeated a plurality of times, a film having a predetermined thickness can be easily formed, and the reforming step is performed after forming a film having a predetermined thickness at a time. In contrast to the case, the film can be sufficiently modified by increasing the removal amount of the specific element in the formed film.
[0020]
A second invention is characterized in that, in the first invention, the film forming step and the reforming step are performed in the same reaction chamber. When the film forming step and the reforming step are performed in the same reaction chamber, the temperature of the substrate does not decrease between the steps, so that the time for heating the substrate again becomes unnecessary, and the time for heating the substrate can be saved. Good processing efficiency. In addition, the substrate stops in the same reaction chamber, so that the film formation surface is less likely to be contaminated.
[0021]
In a third aspect based on the first aspect, the metal atom is Hf, and the metal oxide film is a film containing Hf. When a raw material containing a metal atom is used as the raw material, a gas containing an oxygen atom such as oxygen gas is usually used together. Particularly, when the metal atom is Hf and the metal oxide film is a film containing Hf, the oxygen atom is not used. When no gas is used, the specific element in the film can be effectively removed to modify the film.
[0022]
In a fourth aspect based on the first aspect, the raw material is Hf [OC (CH₃)₂CH₂0CH₃]₄Wherein the metal oxide film is a film containing Hf. When an organic raw material is used as the raw material, a gas containing an oxygen atom is usually used together, but in particular, Hf [OC (CH (CH₃)₂CH₂OCH₃]₄In the case where is used, the amount of specific elements (impurities) such as C and H can be reduced by not using a gas containing oxygen atoms.
[0023]
In a fifth aspect based on the first aspect, the metal atoms are Hf and the metal oxide film is a film containing Hf, and the thickness of the metal oxide film formed in one film forming step is zero. 0.5 to 30 degrees. When the thickness of the Hf-containing film formed in one film formation step is 0.5 to 30 (Å atomic layer to 10 atomic layers), it is possible to maintain a state in which crystallization is difficult even if impurities are contained. By performing the reforming process in this state, impurities can be removed and the film can be easily reformed.
[0024]
A sixth invention is characterized in that, in the second invention, a source gas supplied to the substrate in the film forming step and a reactant supplied to the substrate in the reforming step are supplied from the same supply port. When the raw material gas supplied to the substrate in the film forming step and the reactant supplied to the substrate in the reforming step are supplied from the same supply port, foreign substances adhering to the inside of the supply port may be covered with a metal oxide film and deposited. Thus, it is possible to prevent foreign matters from falling onto the substrate. Further, when the reaction chamber is cleaned with the cleaning gas, it is possible to remove by-products and the cleaning gas adsorbed inside the supply port.
[0025]
In a seventh aspect based on the second aspect, the raw material gas supplied to the substrate in the film forming step and the reactant supplied to the substrate in the reforming step are supplied from separate supply ports, respectively. When supplying the source gas to the substrate from the gas supply port, supply a non-reactive gas to the supply port for the reactant, and supply the reactant to the substrate from the supply port for the reactant in the reforming step. A non-reactive gas is supplied to a supply port for a source gas. As described above, even when the source gas and the reactant are supplied from separate supply ports, and a non-reactive gas such as an inert gas is supplied from a supply port that does not involve each other in each step, the inside of the supply port is further increased. The formation of a cumulative film on the substrate can be suppressed.
[0026]
According to an eighth aspect, in the second aspect, when supplying a source gas to the substrate in the film forming step, the reactants used in the reforming step are evacuated so as to bypass the reaction chamber without stopping. When the reactant is supplied to the substrate in the reforming step, the source gas used in the film forming step is exhausted so as to bypass the reaction chamber without stopping. In this way, if the reactant in the film forming step and the supply of the film forming gas in the reforming step are not stopped, but are flown so as to bypass the reaction chamber, the film can be formed immediately by simply switching the flow. A gas or reactant can be supplied to the substrate. Therefore, the throughput can be improved.
[0027]
According to a ninth aspect, in the second aspect, the exhaust line for exhausting the reaction chamber in the film forming step and the exhaust line for exhausting the reaction chamber in the reforming step are provided with traps used for both steps. Features. Since the trap is provided in the exhaust line, it is possible to reduce the flow of the raw material into the exhaust pump and the abatement device connected to the exhaust line, and to reduce the maintenance cycle of the device. In addition, since the trap is used for both processes, maintenance is simplified.
[0028]
According to a tenth aspect, in the second aspect, there is further provided a cleaning step of removing a film adhered in the reaction chamber using a cleaning gas activated by plasma, and a reactant used in the reforming step is activated by plasma. A plasma source used to activate the gas in the reforming step and a plasma source used to activate the cleaning gas in the cleaning step. Since the plasma source for activating the reactant and the plasma source for activating the cleaning gas are shared, the management of the plasma source becomes easy, and the semiconductor device can be manufactured at low cost.
[0029]
An eleventh invention is characterized in that, in the first invention, the reactant contains an oxygen atom. When the reactant contains an oxygen atom, the step of reforming the specific element can be efficiently performed immediately after the formation of the metal oxide film.
[0030]
In a twelfth aspect based on the first aspect, the reactant includes a gas obtained by activating a gas containing oxygen atoms by plasma. When the reactant is a gas obtained by activating a gas containing an oxygen atom by plasma, the step of reforming the specific element can be performed more efficiently immediately after the formation of the metal oxide film.
[0031]
A thirteenth invention is characterized in that, in the first invention, the film forming step and / or the modifying step are performed while rotating the substrate. Since the rotation is performed while the substrate is rotated, the specific element in the film can be quickly and uniformly removed to modify the film.
[0032]
According to a fourteenth aspect, in the second aspect, a metal oxide film is formed on the substrate by repeating the film forming step and the modifying step, and then the substrate is exposed to the atmosphere via the transfer chamber without exposing the substrate to the atmosphere. A step of transporting to a reaction chamber, and a step of forming an electrode on a metal oxide film formed on a substrate in another reaction chamber, and after forming a metal oxide film, as a separate step from the electrode forming step The method is characterized in that the electrodes are formed without performing the annealing step, and the steps from the formation of the metal oxide film to the formation of the electrodes are performed in the same apparatus. Since the steps from the formation of the metal oxide film to the formation of the electrodes are performed in the same apparatus, the time required to raise the temperature of the substrate can be reduced as compared with the case where the electrodes are formed in different apparatuses. Further, an electrode can be formed while the surface of the film is not cleaned. In addition, since the metal oxide film is densified by the thermal annealing performed at the time of forming the electrode, the film is less likely to be contaminated.
[0033]
A fifteenth invention provides a film forming step of forming a thin film by supplying a film forming gas onto a substrate, and modifying a thin film formed in the film forming step by supplying a reactant different from the film forming gas. In the method for manufacturing a semiconductor device, wherein the reforming step and the reforming step are continuously repeated a plurality of times in the same reaction chamber, the film forming gas supplied to the substrate in the film forming step and the reactant supplied to the substrate in the reforming step are the same. It is characterized by being supplied from a supply port. Since the film forming step and the modifying step are performed continuously, the specific element in the film formed in the film forming step can be quickly removed to modify the film. Further, since the film forming step and the reforming step are continuously repeated a plurality of times, a film having a predetermined thickness can be easily formed, and the reforming step is performed after forming a film having a predetermined thickness at a time. As opposed to the case, the film can be modified by increasing the removal amount of the specific element in the formed film. In addition, when the source gas supplied to the substrate in the film forming step and the reactant supplied to the substrate in the reforming step are supplied from the same supply port, foreign substances adhering to the inside of the supply port may be deposited with a thin film. Thus, it is possible to prevent foreign matters from falling onto the substrate. Further, when the reaction chamber is cleaned with the cleaning gas, it is possible to remove by-products and the cleaning gas adsorbed in the supply port.
[0034]
The sixteenth invention is formed in a film forming step of forming a film containing Hf on a substrate using a source gas obtained by vaporizing a material containing Hf, and a film forming step using a reactant different from the source gas. The step of reforming the film containing Hf is continuously repeated a plurality of times. Since the film formation step and the modification step are performed continuously, the specific element in the Hf-containing film formed in the film formation step can be quickly removed to modify the film. Further, since the film forming step and the reforming step are continuously repeated a plurality of times, a film containing Hf having a predetermined thickness can be easily formed, and a film containing Hf having a predetermined thickness can be formed at a time. As compared with the case where the reforming step is performed, the film containing Hf can be modified by increasing the removal amount of the specific element in the formed film.
[0035]
According to a seventeenth aspect, in the sixteenth aspect, the film thickness of the Hf-containing film formed in one film forming step is 0.5 ° to 30 °. When the thickness of the Hf-containing film formed in one film formation step is 0.5 to 30 degrees, that is, 1/6 atomic layer to 10 atomic layers, it is possible to maintain a state in which crystallization is difficult even if impurities are present, By performing the reforming treatment in this state, impurities can be removed and the film can be easily reformed.
[0036]
An eighteenth invention provides a film forming step of forming a thin film by supplying a film forming gas onto a substrate, and modifying a thin film formed in the film forming step by supplying a reactant different from the film forming gas. A step of forming a thin film on a substrate by continuously repeating the reforming step and a plurality of times in the same reaction chamber, and then transferring the substrate from the reaction chamber to another reaction chamber via a transfer chamber without exposing the substrate to the atmosphere; Forming an electrode on a thin film formed on a substrate in another reaction chamber. After forming the thin film, the electrode is formed without performing an annealing step as a separate step from the electrode forming step. It is characterized in that the steps from the formation of the electrode to the formation of the electrode are performed in the same apparatus. Since the steps from the formation of the thin film to the modification of the thin film and the formation of the electrodes are performed in the same apparatus, the time required to raise the temperature of the substrate can be reduced as compared with the case where the modification of the thin film and the formation of the electrodes are performed by different apparatuses. In addition, the specific element in the film can be quickly removed to modify the film, and the electrode can be formed while the surface of the thin film is not cleaned. Further, since the thin film is densified by the thermal annealing performed at the time of forming the electrode, the thin film is less likely to be contaminated.
[0037]
A nineteenth invention is directed to a reaction chamber for processing a substrate, a first supply port for supplying a source gas obtained by vaporizing a source material containing oxygen atoms and metal atoms into the reaction chamber, and a reaction different from the gas in the reaction chamber. A second supply port for supplying a substance; and an exhaust port for exhausting the reaction chamber, forming a metal oxide film on the substrate in the reaction chamber without using a gas containing oxygen atoms other than the source gas. A control device for controlling the film forming step to be performed and the reforming step for reforming the metal oxide film formed in the film forming step using a reactant different from the source gas continuously and repeatedly a plurality of times And a substrate processing apparatus having: By providing a control device that controls the film forming step and the modifying step to be continuously repeated a plurality of times, the above-described method for manufacturing a semiconductor device can be easily implemented.
[0038]
In the first to second inventions, the sixth to fifteenth inventions, the eighteenth and nineteenth inventions described above, the film formed in the film forming step is not limited to a film containing Hf. In the third invention to the fifth invention and the sixteenth invention to the seventeenth invention, the film formed in the film forming step is limited to a film containing Hf. As an example of the film containing Hf, HfO₂, HfON, HfSiO, HfSiON, HfAlO, HfAlON, and the like. Examples of a film other than the film containing Hf include the following.
PET (Ta (OC₂H₅)₅) -Based TaO film (tantalum oxide film)
Zr- (MMP)₄(Zirconium oxide film) using ZrO
Al- (MMP)₃AlO film using aluminum (aluminum oxide film)
Zr- (MMP)₄And Si- (MMP)₄Film (Zr oxide oxide film) or ZrSiON film (Zr oxynitride silicate film)
Zr- (MMP)₄And Al- (MMP)₃ZrAlO film and ZrAlON film using
Ti- (MMP)₄TiO film (titanium oxide film)
Ti- (MMP)₄And Si- (MMP)₄Or TiSiON film using GaN
Ti- (MMP)₄And Al- (MMP)₃, TiAlON film using AlN
[0039]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. In the embodiment, the HfO film, particularly in the amorphous state, is formed using the CVD method, more specifically, the MOCVD method.₂Membrane (hereinafter simply referred to as HfO₂(Abbreviated as a film) will be described.
[0040]
FIG. 1 is a schematic diagram illustrating an example of a single-wafer CVD apparatus that is a substrate processing apparatus according to an embodiment. In the conventional reaction chamber 1 (FIG. 19), a reactant activation unit 11, a substrate rotation unit 12, an inert gas supply unit 10, and a bypass pipe 14, which are plasma sources, are mainly added.
[0041]
As shown in the figure, a hollow heater unit 18 having an upper opening covered by a susceptor 2 is provided in the reaction chamber 1. The heater 3 is provided inside the heater unit 18, and the heater 3 heats the substrate 4 mounted on the susceptor 2. The substrate 4 placed on the susceptor 2 is, for example, a semiconductor silicon wafer, glass, or the like.
[0042]
A substrate rotation unit 12 is provided outside the reaction chamber 1, and the substrate rotation unit 12 can rotate the heater unit 18 in the reaction chamber 1 to rotate the substrate 4 on the susceptor 2. The reason why the substrate 4 is rotated is that processing on the substrate in a film forming step and a reforming step, which will be described later, is quickly and uniformly performed on the substrate surface.
[0043]
Further, a shower head 6 having a large number of holes 8 is provided above the susceptor 2 in the reaction chamber 1. A raw material supply pipe 5 for supplying a film forming gas and a radical supply pipe 13 for supplying radicals are commonly connected to the shower head 6, so that the film forming gas or radicals are showered from the shower head 6 into the reaction chamber 1. It can be squirted into the interior. Here, the shower head 6 forms the same supply port for supplying a film forming gas to be supplied to the substrate 4 in the film forming step and a radical to be supplied to the substrate 4 in the reforming step.
[0044]
A film-forming material supply unit 9 for supplying an organic liquid material as a film-forming material to the outside of the reaction chamber 1, a liquid flow control device 28 as a flow rate control means for controlling a liquid supply flow rate of the film-forming material, Is provided. An inert gas supply unit 10 for supplying an inert gas as a non-reactive gas, and a mass flow controller 46 as a flow control means for controlling a supply flow rate of the inert gas are provided. Hf- (MMP)₄Use an organic material such as In addition, as the inert gas, Ar, He, N₂And so on. The raw material 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 the raw material supply pipe connected to the shower head 6 5 are provided. The raw material supply pipe 5 has HfO₂In a film forming step of forming a film, a mixed gas of a film forming gas and an inert gas is supplied to the shower head 6. Valves 21 and 20 are provided in the source gas supply pipe 5b and the inert gas supply pipe 5a, respectively, and the supply of the mixed gas of the film forming gas and the inert gas is controlled by opening and closing these valves 21 and 20. It is possible.
[0045]
Further, a reactant activating unit (remote plasma unit) 11 serving as a plasma source for activating gas by plasma to form radicals as reactants is provided outside the reaction chamber 1. The radical used in the reforming step is Hf- (MMP) as a raw material.₄When using an organic material such as, for example, oxygen radicals are preferable. This is due to oxygen radicals, HfO₂This is because impurities such as C and H can be efficiently removed immediately after the film is formed. The radical used in the cleaning step is ClF₃Radicals are good. In the reforming step, an oxygen-containing gas (O₂, N₂A process for oxidizing a film in an oxygen radical atmosphere in which O, NO, etc. are decomposed by plasma is referred to as a remote plasma oxidation (RPO) process.
[0046]
A gas supply pipe 37 is provided upstream of the reactant activation unit 11. This gas supply pipe 37 has oxygen (O₂), An Ar supply unit 48 for supplying argon (Ar) as a gas for generating plasma, and chlorine fluoride (ClF).₃) To supply ClF₃A supply unit 49 is connected via supply pipes 52, 53, and 54 to supply O₂And Ar, and ClF used in the cleaning process₃Is supplied to the reactant activation unit 11. Oxygen supply unit 47, Ar supply unit 48, and ClF₃The supply unit 49 is provided with mass flow controllers 55, 56, and 57 as flow control means for controlling the supply flow rates of the respective gases. The supply pipes 52, 53, 54 are provided with valves 58, 59, 60, respectively.₂Gas, Ar gas, and ClF₃Supply can be controlled.
[0047]
A radical supply pipe 13 connected to the shower head 6 is provided downstream of the reactant activation unit 11 so as to supply oxygen radicals or chlorine fluoride radicals to the shower head 6 in a reforming step or a cleaning step. It has become. Further, a valve 24 is provided in the radical supply pipe 13, and the supply of radicals can be controlled by opening and closing the valve 24.
[0048]
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 (not shown). The exhaust pipe 7 is provided with a raw material recovery trap 16 for recovering a film forming raw material. This raw material recovery trap 16 is used for both the film forming step and the reforming step. The exhaust port 7a and the exhaust pipe 7 constitute an exhaust line.
[0049]
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 connected to a source recovery trap 16 provided in the exhaust pipe 7 (these may be simply referred to as the bypass pipe 14). Is provided. Valves 22 and 23 are provided on the source gas bypass pipe 14a and the radical bypass pipe 14b, respectively. When the film formation gas is supplied to the substrate 4 in the reaction chamber 1 in the film formation step by opening and closing these valves, the supply of the radicals used in the reforming step is stopped so as to bypass the reaction chamber 1. The air is exhausted through the bypass pipe 14b and the raw material recovery trap 16. Further, when supplying the radicals to the substrate 4 in the reforming step, the source gas bypass pipe 14a and the source recovery trap 16 are set so as to bypass the reaction chamber 1 without stopping the supply of the film forming gas used in the film forming step. Exhaust through.
[0050]
Then, HfO is placed on the substrate 4 in the reaction chamber 1.₂A film forming step of forming a film and HfO formed in the film forming step₂The reforming step of removing impurities such as C and H as specific elements in the film by plasma treatment using the reactant activation unit 11 is continuously performed by controlling the opening and closing of the valves 20 to 24 and the like. A control device 25 is provided for controlling the operation to be repeated a plurality of times.
[0051]
Next, using a single-wafer CVD apparatus having the configuration shown in FIG.₂1 shows a procedure for depositing a film. This procedure includes a temperature raising step, a film forming step, a purge step, and a reforming step.
[0052]
First, the substrate 4 is placed on the susceptor 2 in the reaction chamber 1 shown in FIG. 1, and while the substrate 4 is rotated by the substrate rotating unit 12, power is supplied to the heater 3 to reduce the temperature of the substrate 4 to 350 to 500. Heat uniformly to ° C. (heating step). Although the substrate temperature varies depending on the reactivity of the organic material used, Hf- (MMP)₄Is preferably in the range of 390 to 450 ° C. When the substrate 4 is transported or heated, the valve 20 provided on the inert gas supply pipe 5a is opened, and Ar, He, N₂By constantly flowing an inert gas such as this, it is possible to prevent particles and metal contaminants from adhering to the substrate 4.
[0053]
After the completion of the temperature raising step, a film forming step is started. In the film forming process, the organic liquid raw material supplied from the film forming raw material supply unit 9, for example, Hf- (MMP)₄Is flow-controlled by the liquid flow controller 28 and supplied to the vaporizer 29 to be vaporized. By opening the valve 21 provided on the source gas supply pipe 5b, the vaporized source gas is supplied onto the substrate 4 via the shower head 6. At this time, the valve 20 is kept open, and the inert gas (N₂, Etc.) are constantly flowed to stir the film forming gas. When the film forming gas is diluted with an inert gas, stirring becomes easier. The film forming gas supplied from the source gas supply pipe 5b and the inert gas supplied from the inert gas supply pipe 5a are mixed in the source supply pipe 5 and guided to the shower head 6 as a mixed gas, and a large number of Through the hole 8, the water is supplied onto the substrate 4 on the susceptor 2 in a shower shape. In this case, O₂Such as Hf- (MMP) is not supplied as a reactive gas.₄Supply only gas.
[0054]
By supplying this mixed gas for a predetermined time, HfO as an interface layer (first insulating layer) with the substrate is formed on the substrate 4.₂The film is formed at 0.5 to 30 degrees, for example, 15 degrees. During this time, since the substrate 4 is kept at a predetermined temperature (film formation temperature) by the heater 3 while rotating, a uniform film can be formed over the substrate surface. Next, the valve 21 provided on the source gas supply pipe 5b is closed, and the supply of the source gas to the substrate 4 is stopped. At this time, the valve 22 provided on the source gas bypass pipe 14a is opened, and the supply of the film forming gas is evacuated by bypassing the reaction chamber 1 by the source gas bypass pipe 14a. Do not stop the gas supply. Since it takes time to vaporize the liquid raw material and to stably supply the vaporized raw material gas, if the flow of the film forming gas is bypassed and the reaction chamber 1 is flown so as to be bypassed, the following reaction occurs. In the film process, the film formation gas can be supplied to the substrate 4 immediately by simply switching the flow.
[0055]
After the completion of the film forming process, a purge process is started. In the purging step, the inside of the reaction chamber 1 is purged with an inert gas to remove the residual gas. In the film forming step, the valve 20 is kept open, and the inert gas (N) is supplied from the inert gas supply unit 10 into the reaction chamber 1.₂And so on), the valve 21 is closed, the supply of the source gas to the substrate 4 is stopped, and the purge is performed at the same time.
[0056]
After the purging step, the reforming step is started. The reforming step is performed by a remote plasma oxidation (RPO) process. Here, the RPO treatment refers to an oxygen-containing gas (O₂, N₂O, NO, etc.) is a remote plasma oxidation process in which a film is oxidized using oxygen radicals as a reactant generated by being activated by plasma. In the reforming step, the valve 59 provided in the supply pipe 53 is opened, and the Ar supplied from the Ar supply unit 48 is flow-controlled by the mass flow controller 56 to supply the Ar to the reactant activation unit 11 to generate Ar plasma. After the Ar plasma was generated, the valve 58 provided on the supply pipe 52 was opened, and the oxygen supplied from the oxygen supply unit 47 was supplied.₂Is supplied to the reactant activating unit 11 which controls the flow rate by the mass flow controller 55 to generate Ar plasma, and₂Activate. Thereby, oxygen radicals are generated. The valve 24 provided in the radical supply pipe 13 is opened, and a gas containing oxygen radicals is supplied from the reactant activation unit 11 onto the substrate 4 via the shower head 6. 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 the HfO of 15 ° formed on the substrate 4 in the film forming process is formed.₂Impurities such as C and H can be quickly and uniformly removed from the film.
[0057]
Thereafter, the valve 24 provided on the radical supply pipe 13 is closed to stop the supply of oxygen radicals to the substrate 4. At this time, by opening the valve 23 provided in the radical bypass pipe 14b, the supply of the gas containing oxygen radicals is exhausted by bypassing the reaction chamber 1 by the radical bypass pipe 14b, and the supply of oxygen radicals is not stopped. To do. Since it takes time from the generation to the stable supply of oxygen radicals, if the supply of oxygen radicals is flown so as to bypass the reaction chamber 1 without stopping, in the next reforming step, only the flow is switched. Thus, radicals can be immediately supplied to the substrate 4.
[0058]
After the reforming step, the purge step is started again. In the purging step, the inside of the reaction chamber 1 is purged with an inert gas to remove the residual gas. In the reforming step, the valve 20 is kept open, and the inert gas (N) is supplied from the inert gas supply unit 10 into the reaction chamber 1.₂, Etc.) are constantly flowing, so that the supply of oxygen radicals to the substrate 4 is stopped and, at the same time, the purge is performed.
[0059]
After the purging step is completed, the film forming step is started again, the valve 22 provided in the source gas bypass pipe 14a is closed, and the valve 21 provided in the source gas supply pipe 5b is opened, so that the film forming gas is passed through the shower head 6. HfO of 15 °₂The film is deposited on the thin film formed in the previous film forming step.
[0060]
As described above, the cycle processing of repeating the film forming step, the purging step, the reforming step, and the purging step a plurality of times can form a thin film having a predetermined film thickness with a very small amount of CH and OH mixed therein.
[0061]
Here, Hf- (MMP)₄Preferred film forming conditions when using are as follows. The temperature range is 400 to 450 ° C., and the pressure range is about 100 Pa or less. When the temperature is lower than 400 ° C., the amount of impurities (C, H) taken into the film increases rapidly. When the temperature is 400 ° C. or higher, impurities are easily released, and the amount of impurities taken into the film decreases. When the temperature is higher than 450 ° C., the step coverage deteriorates. However, when the temperature is 450 ° C. or lower, good step coverage can be obtained, and the amorphous state can be maintained.
[0062]
When the pressure is set to a high pressure of, for example, 1 Torr (133 Pa) or more, the gas becomes a viscous flow, so that the gas does not enter the depth of the pattern groove. However, by setting the pressure to about 100 Pa or less, a molecular flow having no flow can be obtained, and the gas reaches the inside of the pattern groove.
[0063]
Also, Hf- (MMP)₄The preferable conditions of the RPO (remote plasma oxidation) treatment, which is a modification step performed continuously to the film formation step using, are as follows: a temperature range is about 390 to 450 ° C. (substantially the same as the film formation temperature); About 1000 Pa. Also, O for radicals₂The flow rate is 100 sccm, and the inert gas Ar flow rate is 1 slm.
[0064]
It is preferable that the film forming step and the reforming step be performed at substantially the same temperature (preferably, the set temperature of the heater is kept constant without being changed). This is because, by not causing a temperature change, particles due to thermal expansion of peripheral members such as a shower head and a susceptor are less likely to be generated, and it is possible to prevent metal from jumping out of a metal component (metal contamination).
[0065]
In order to perform the self-cleaning process of the accumulated film by the cleaning gas radical, the reactant activation unit 11 uses the cleaning gas (Cl₂And ClF₃) Into the reaction chamber 1 as radicals. By this self-cleaning, the cleaning gas reacts with the accumulated film in the reaction chamber 1, the accumulated film is converted into a metal chloride or the like, volatilized, and exhausted. Thereby, the accumulated film in the reaction chamber is removed.
[0066]
According to the above-described embodiment, HfO₂Film formation → reforming treatment (RPO treatment) → HfO₂Since a cycle process in which film formation → ... is repeated a plurality of times is performed, HfO of a predetermined film thickness with extremely little CH and OH contamination is used.₂A film can be formed. Hereinafter, this will be specifically described from the following viewpoints.
(1) O during film formation₂Non-use
(2) RPO processing
(3) Cycle processing
(4) Rotation mechanism
(5) Sharing a shower head
(6) Bypass pipe
(7) Trap sharing
(8) Use of plasma source
(9) Processing performed in the same device
(10) Modified example
[0067]
(1) O during film formation₂Non-use
HfO in the film forming process₂At the time of film formation, oxygen (O₂If a gas containing an oxygen atom such as) is not used, the amount of CH and OH mixed in the film can be reduced.
[0068]
HfO₂When a film is formed, O 2 is contained in a mixed gas of a source gas and an inert gas.₂In some cases. Considering the adhesion to the base and the film formation rate, this is generally O₂Because it is better to put However, the present inventors have found that Hf- (MMP)₄About O₂If no is added, the amount of impurities is reduced and the film quality is improved.₂It has been found that the amount of impurities increases and the quality of the film decreases with the addition of. Therefore, Hf- (MMP)₄In an embodiment using₂Is not mixed, the mixing amount of CH and OH in the film can be reduced.₂Not mixed.
[0069]
Hf- (MMP)₄The mechanism by which oxygen is not supplied and the amount of impurities mixed can be reduced when oxygen is used is as follows. Hf- (MMP)₄When oxygen is mixed using (hereinafter, also referred to as oxygen) and when oxygen is not mixed (hereinafter, also referred to as no oxygen), an ideal chemical reaction formula is compared as follows.
[0070]
A. If the ideal reaction occurs without oxygen (ideal autolysis reaction by heat only):
Hf [OC (CH₃)₂CH₂OCH₃]₄→ Hf (OH)₄+ 4C (CH₃)₂CH₂OCH₂↑ (1)
Hf (OH)₄→ HfO₂+ 2H₂O (2)
B. If the ideal reaction occurs with oxygen (complete combustion):
Hf [OC (CH₃)₂CH₂OCH₃]₄+ 24O₂→ HfO₂+ 16CO₂↑ + 22H₂O ↑ (3)
Here, ↑ means a volatile substance.
In the above reaction formula, the upper case numerical value is considered as the molar ratio of the raw materials on the substrate as it is, without oxygen,
HfO₂: (Other impurities) = 1: (4 + 2) = 1: 6
Becomes With oxygen,
HfO₂: (Other impurities) = 1: (16 + 22) = 1: 38.
[0071]
Therefore, one mole of HfO₂The total number of moles of impurities generated at the time of generation of oxygen is larger in the presence of oxygen.
[0072]
Furthermore, comparing the number of cleavages in the chemical formula for breaking each bond,
In the case of no oxygen: OC, CH and OH are cut 4 times each, 12 times in total
With oxygen: OC 12 times, CH 4 times, 56 times in total
As the number of cuts increases, the amount of radicals increases, so that impurities easily enter the film.
[0073]
In conclusion, a film was formed without oxygen, and [C (CH₃)₂CH₂OCH₃] At a temperature that does not decompose HfO₂A film is preferably formed.
[0074]
In addition, using FTIR (Fourier transform infrared spectroscopy),₂2 and 3 in which the effect of the addition amount on the thin film was measured, it was found that HfO₂It is supported that it is preferable to form a film.
[0075]
FIG. 2 shows the film quality characteristics of the thin film compared with the case without oxygen and the case with oxygen. The wave number (cm^-1), And the vertical axis shows the absorbance at film forming temperatures of 425 ° C. and 440 ° C. When oxygen is present, the oxygen flow rate is 0.5 SLM. As shown in FIG.^-1By exciting the nearby stretch mode, the absorbance reflecting the XOX bond indicating the Hf-O-Hf bond is higher in the absence of oxygen than in the presence of oxygen. In other words, it shows that the film quality without oxygen is better.
[0076]
FIG. 3 shows the characteristics of the amount of impurities contained in the film in comparison with the case without oxygen and the case with oxygen. The wave number (cm^-1), And the vertical axis shows the absorbance at 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 drawing, by exciting the stretch and wagging modes, the absorbance reflecting the amount of impurities (—OH, CH, CO) becomes no oxygen when oxygen is present. It was found that the film formation with oxygen was about five times as large as the film formation without oxygen. This indicates that the case without oxygen has a smaller amount of impurities and a better film quality. Therefore, HfO₂During film formation, O₂If not used, the amount of CH and OH mixed in the film can be reduced, and the film can be sufficiently modified. Note that the present invention₂This is not to be excluded at all, and O₂A small amount of O which is not substantially different from the case where no₂Is included, and even in such a case, the film can be sufficiently modified.
[0077]
Here, the mechanism of the film formation using the self-decomposition reaction, the semi-self-decomposition reaction, and the adsorption reaction of the raw material and the temperature zone will be described in relation to the invention. All the CVD reactions are in a state where the self-decomposition reaction and the adsorption reaction overlap. If the substrate temperature is lowered, the adsorption reaction becomes dominant, and if the temperature is raised, the self-decomposition reaction becomes dominant. At an intermediate temperature, a semiautolytic reaction also occurs. Hf- (MMP)₄In the case where is used, it is considered that the adsorption reaction is mainly at 300 ° C. or lower, and the self-decomposition reaction is mainly when the temperature is higher than 300 ° C. However, the adsorption reaction does not disappear at all temperature zones. Hf- (MMP)₄Are as shown in the above formulas (1) and (2). In addition, Hf- (MMP) is formed on the substrate by the adsorption reaction.₄Is adsorbed and oxidized by RPO treatment or the like to cause a film formation reaction, the reaction formula is Hf- (MMP)₄And O₂Is the same as in the case of reacting (gas phase reaction), as in the above formula (3). In MOCVD in the present invention, the effect of removing impurities by RPO can be obtained regardless of which of the above reactions is dominant. Therefore, the type of reaction is not particularly specified. Experimental results have shown that less can be achieved.
[0078]
(2) RPO processing
By the RPO treatment used in the reforming step after the film formation, impurities such as hydrogen (H) and carbon (C) in the film can be effectively removed and the concentration thereof can be reduced, so that electric characteristics can be improved. In addition, elimination of hydrogen (H) suppresses movement of Hf atoms, prevents crystallization, and improves electrical characteristics. Further, oxidation of the film can be promoted, and oxygen defects in the film can be repaired. In addition, the amount of gas released from the accumulated film deposited on portions other than the substrate such as the inner wall of the reaction chamber and the susceptor can be reduced quickly, and the film thickness can be controlled with high reproducibility.
[0079]
In the embodiment, the RPO process is used in the reforming step, but the present invention is not limited to this. As an alternative to the RPO process ((1) below), for example, there are the following ((2) to (8) below).
(1) O to Ar (inert gas)₂Processing performed by mixing
(2) N in Ar₂RPN processing performed by mixing
(3) N in Ar₂And H₂RPNH treatment performed by mixing
(4) H in Ar₂RPH treatment performed by mixing
(5) H in Ar₂RPOH treatment performed by mixing O
(6) O for Ar₂And H₂RPOH treatment performed by mixing
(7) N in Ar₂RPON process performed by mixing O
(8) N in Ar₂And O₂RPON process performed by mixing
[0080]
In the embodiment, HfO is used in the same reaction chamber.₂The film formation and the RPO process are performed, and the merits are as follows. HfO₂When a film is formed, HfO is applied to the reaction chamber wall, shower head, susceptor, and the like.₂A film is formed. This is called a cumulative formation film. HfO without RPO treatment when performed in separate reaction chambers₂In the film reaction chamber, C and H come out of the accumulated film and contaminate the reaction chamber. Further, the amounts of C and H coming out of the accumulated film increase as the thickness thereof increases. Therefore, it is difficult to keep the C and H amounts of all the substrates to be processed constant.
[0081]
In contrast, HfO₂When the film formation and the RPO treatment are performed in the same reaction chamber, C and H can be removed not only from C and H in the film formed on the substrate but also from the accumulated film adhered in the reaction chamber (cleaning). Effect), C and H contents can be kept constant for all substrates.
[0082]
(3) Cycle processing
By the cycle processing, the impurity removal efficiency in the film can be improved as described above. Further, the film can be maintained in an amorphous state, and as a result, a leak current can be reduced. Further, the flatness of the film surface can be improved, and the uniformity of the film thickness can be improved. In addition, the film can be densified (maximizing the effect of repairing defects), and the deposition rate can be precisely controlled. Furthermore, an undesired interface layer formed at the interface between the film formation base and the film to be deposited can be thinned.
[0083]
HfO formed by cycle processing₂The amounts of C and H impurities contained in the film (for example, a film thickness of 10 nm) can be significantly reduced as the number of cycles increases as shown in FIG. The horizontal axis indicates the number of cycles, and the vertical axis indicates the total amount of C and H (arbitrary units). Incidentally, the case where the number of cycles is 1 corresponds to the case of the conventional method.
[0084]
According to FIG. 4, HfO formed by cycle processing₂When the total film thickness is 10 nm (100 °), HfO such as CH or OH is₂Since the effect of reducing the amount of impurities in the film is increased, the film thickness per cycle is preferably about 30 ° or less. Note that in CVD, the film thickness that can be formed by one film formation is about 0.5 °, and therefore the film thickness per cycle is preferably 0.5 ° to 30 °. In particular, HfO such as CH and OH in about 7 cycles₂The effect of reducing the amount of impurities in the film becomes extremely large. Even if the number of cycles is further increased, the effect of reducing the amount of impurities is slightly improved, but the change does not change so much. Atomic layer) is considered more preferred. If 30 ° or more is deposited in one cycle, impurities in the film increase, and the film is immediately crystallized to be in a polycrystalline state. Since there is no gap in the polycrystalline state, it is difficult to remove C, H, and the like. However, when the film thickness formed by one cycle is less than 30 °, it is difficult to form a crystallized structure, and the thin film can be maintained in an amorphous state even if impurities exist. Since the amorphous state has many gaps (a sparse state), a thin film is deposited while maintaining the amorphous state, and RPO treatment is performed before the thin film is crystallized to remove impurities such as C and H in the film. Easier to do. That is, the film obtained by performing the cycle processing a plurality of times with the film thickness per cycle being about 0.5 ° to 30 ° is hardly crystallized. Note that the amorphous state has an advantage that a leak current is less likely to flow than the polycrystalline state.
[0085]
Note that HfO₂By repeating film formation → RPO processing a plurality of times, HfO₂The reason why the efficiency of removing impurities from the film can be increased is as follows. HfO formed with good coverage for deep pattern grooves₂When performing RPO treatment (reforming treatment of C, H, etc.) on the film, HfO₂When the RPO process is performed after forming the film to a large thickness, for example, 100 °, it becomes difficult to supply oxygen radicals to the deep portion b of the groove in FIG. This is because the probability that oxygen radicals react with C and H at the portion of the surface a in FIG. 5 in the process of reaching the depth b of the groove increases (the film thickness is as large as 100 ° and the impurity amount is correspondingly large). This is because the amount of radicals reaching the depth b of the groove is relatively reduced. Therefore, it is difficult to uniformly remove C and H in a short time.
[0086]
100% HfO₂When forming a film, HfO₂In the case where the film formation → the RPO process is performed in seven steps, the RPO process is performed using HfO per 15 °.₂The C and H removal processes need only be performed on the film. In this case, the probability that oxygen radicals react with C and H at the portion of the plane a in FIG. 5 does not increase (because the film thickness is as thin as 15 ° and the amount of impurities is accordingly small), so that the depth b of the groove is also uniform. The radicals will arrive. Therefore, HfO₂By repeating film formation → RPO processing a plurality of times, uniform C and H removal can be performed in a short time.
[0087]
Further, by performing a cycle process in which the film forming step and the reforming step are continuously repeated a plurality of times, the amount of impurities such as C and H contained in the accumulated film adhered in the reaction chamber can be significantly reduced. Since the gas released from the accumulated film can be greatly reduced, HfO continuously produced₂The quality of the film can be kept constant. Therefore, it is not necessary to frequently perform the process of removing the accumulated film by self-cleaning as compared with the related art, and the production cost can be reduced.
[0088]
(4) Rotation mechanism
In the embodiment, since the substrate 4 is rotated by the substrate rotation unit 12, the source gas introduced from the film forming source supply unit and the gas activated by the plasma as the reactant introduced from the reactant activation unit 11 ( Hereafter, the radicals can spread quickly and uniformly on the substrate surface, and the film can be uniformly deposited on the substrate surface, and the impurities in the film can be quickly and uniformly removed on the substrate surface to form the entire film. Can be modified.
[0089]
(5) Sharing a shower head
When a film forming gas supplied to the substrate in the film forming step and a radical as a reactant to be supplied to the substrate in the reforming step are supplied from the shower head 6 serving as the same supply port, the foreign matter attached inside the shower head 6 ( HfO (particle source)₂The coating can be performed by covering with a film, and foreign substances can be prevented from falling onto the substrate 4. Further, the film coated inside the showerhead is exposed to a reactant after coating, whereby the amount of impurities such as C and H contained in the coating film inside the showerhead can be significantly reduced. Further, the reaction chamber 1 is₃When cleaning is performed with a gas containing Cl such as, for example, by-products and cleaning gas remaining in the reaction chamber 1 and the shower head 6 are adsorbed (this is referred to as a cleaning residue), supply of a raw material gas and a reactant is performed. By sharing the mouth, the cleaning residue can be effectively removed. .
[0090]
(6) Bypass pipe
In the embodiment, the bypass pipes 14 (14a, 14b) are installed in each of the film forming gas and the radical supply system, and the radical / gas used in the next step is exhausted from the bypass pipe 14 without stopping during gas / radical supply. I am trying to do it. Preparation is required for the supply of the raw material gas / radical, and it takes time until the supply is started. Therefore, during the processing, the supply of the source gas / radical is not stopped, but is continuously supplied. When the source gas / radical is not used, the source gas / radical is immediately exhausted by simply switching valves 21 to 24 at the time of use. Supply can be started, and the throughput can be improved.
[0091]
(7) Trap sharing
In the embodiment, the trap 16 is shared by the film formation gas and the radical exhaust system. That is, as shown in FIG. 1, a raw material recovery trap 16 for recovering the raw material is provided in the exhaust pipe 7, and the bypass pipe 14 is connected to the raw material recovery trap 16, so that the trapped liquid raw material is converted to oxygen radicals. It is possible to convert the raw material into a solid and prevent the raw material from flowing into an exhaust pump (not shown) due to re-vaporization. As a result, the raw material recovery rate can be improved, the flow of the raw material into the exhaust pump and the abatement apparatus (not shown) can be reduced, and the maintenance cycle of the substrate processing apparatus can be greatly extended.
[0092]
(8) Use of plasma source
In the embodiment, the plasma source used for activating the gas in the RPO process in the reforming process and the plasma source used for activating the cleaning gas in the cleaning process are shared. In the cleaning step, the film adhered in the reaction chamber 1 is removed using a cleaning gas activated by the plasma generated in the reactant activation unit 11, and the plasma generated in the reactant activation unit 11 is also used in the reforming step. The film is reformed using the reactant activated by, and the plasma source for reactant activation and cleaning gas activation is shared, making it easier to manage the plasma source and reducing the cost of the semiconductor device. Can be manufactured.
[0093]
(9) Processing performed in the same device
According to the embodiment, (HfO₂Since the process from the formation of the metal oxide film to the electrode formation by (film formation → RPO process) × n cycles is performed in the same apparatus, the time required for raising the temperature of the substrate can be saved as compared with the case where the electrodes are formed by different apparatuses. Further, an electrode can be formed while the surface of the film is not cleaned. In addition, since the metal oxide film is densified by thermal annealing performed at the time of electrode formation, an electrode can be formed without performing an annealing step as a step separate from the metal oxide film electrode formation step after the metal oxide film formation. Is less likely to be contaminated. Hereinafter, this will be described in detail.
[0094]
FIG. 6 shows HfO obtained by the seven-cycle process (the present invention) of the embodiment.₂Membrane and HfO obtained by one cycle treatment (conventional method)₂The film shows the electrical insulation characteristics before and after the RTA treatment. HfO on horizontal axis₂The electric field (arbitrary unit) applied to the film (10 nm) is shown, and the vertical axis shows the leak current (arbitrary unit). Here, the RTA process means that the substrate is heated to about 700 ° C. while the atmospheric pressure (O₂(In an atmosphere) at a high speed. In the figure, the conventional HfO₂Means HfO obtained by one cycle processing₂HfO of the present invention₂Means HfO obtained by 7 cycle processing₂Represents a membrane. Also, “without RTA” means that before RTA processing, and “with RTA” means that after RTA processing. According to FIG. 6, the one obtained by one-cycle processing (conventional HfO (without RTA)) has a large amount of CH and OH mixed therein, and the insulation characteristics change significantly before and after RTA. Since the insulating film obtained by the 7-cycle process (HfO of the present invention (without RTA)) has a small amount of CH and OH mixed therein, the insulating characteristics in the initial stage (in a state where no long-time electrical stress is applied) are almost unchanged before and after RTA. I understand that there is no. Thus, by performing the cycle processing of the present embodiment, it is possible to improve the electrical insulation of the thin film and to reduce the RTA processing required for securing the stability.
[0095]
By reducing the RTA processing, the configuration of the cluster device can be simplified. This will be described with reference to FIG. 7 showing the configuration of a cluster device.
[0096]
The cluster apparatus includes a substrate transfer chamber 40 provided with a substrate transfer robot 41, a load lock chamber 42 for loading / unloading a substrate to / from the apparatus, a first reaction chamber 43 for performing surface treatment (such as RCA cleaning) on the substrate, and FIG. HfO as shown CVD reaction chamber₂A second reaction chamber 44 for forming a film and a third reaction chamber 45 for forming an electrode on the thin film are provided.
[0097]
In the conventional cluster device configuration (see FIG. 20), the substrate surface treatment is performed in the first reaction chamber 33 and the HfO₂A film was formed, RTA processing was performed in the third reaction chamber 35, and an electrode was formed in the fourth reaction chamber 36. In contrast, according to the embodiment of FIG. 7, after the substrate is carried into the load lock chamber 42 from outside the apparatus, the substrate is subjected to substrate surface treatment such as RCA cleaning in the first reaction chamber 43 and HfO₂The film formation and the modification treatment are repeated (HfO₂Film formation → reforming → HfO₂Film formation → reforming → →), HfO with a predetermined thickness₂A film is formed, and an electrode (poly-Si thin film formation and thermal annealing treatment) is formed in the third reaction chamber 45. Then, the substrate on which the electrodes are formed is carried out of the device from the load lock chamber 42.
[0098]
FIG. 8 shows the HfO of the substrate obtained by the above-described conventional example and the cluster device configuration of the embodiment.₂FIG. 2 shows a diagram comparing electrical characteristics of films. The horizontal axis is the capacitance (arbitrary unit), and the vertical axis is HfO₂It shows the leakage current (arbitrary unit) when the film thickness is about 5 nm, about 10 nm, and about 15 nm. As can be seen from the figure, the HfO obtained by the conventional tarasque device (1 cycle process) shown in FIG.₂From the film characteristics (open dots in the figure), the cluster device (HfO) of the embodiment shown in FIG.₂This shows that the characteristics (black dots in the figure) obtained by the film (7-cycle treatment) are better. This result indicates that the RTA processing is not required, and such a cluster configuration that does not require the RTA processing can be realized by using the HfO 2 in the second reaction chamber 44 in FIG.₂It is considered that this is because the removal of CH and OH from the film is sufficiently performed by the process according to the present embodiment.
[0099]
Therefore, in this embodiment, the reaction chamber for RTA can be omitted from the cluster device, and the configuration can be simplified. In addition, since the RTA process for removing CH and OH is not performed, HfO₂The surface condition of the film does not lose its flatness, and HfO₂The film does not partially crystallize and the insulating property and its stability are not reduced.
[0100]
In the embodiment, HfO₂After the film is formed in the second reaction chamber 44, the electrodes are formed in the third reaction chamber 45 in the same cluster device without performing the RTA process. Thus, HfO₂After the film is formed (second reaction chamber), when the process up to electrode formation (third reaction chamber) is performed in the same apparatus,
[0101]
{Circle around (1)} The substrate can be taken out of one apparatus and loaded into another apparatus, and then the temperature of the substrate can be raised again.
{Circle around (2)} HfO is formed by thermal annealing at 700 ° C. or more performed during electrode formation.₂Since the film is densified, the surface of the film is less likely to be contaminated.
(3) HfO₂Electrodes can be formed while the surface of the film is kept clean.
There are such advantages.
Note that HfO₂After the film is formed (the second reaction chamber), the substrate may be taken out of the apparatus and the electrode may be formed by another apparatus. However, when the electrodes are formed by another apparatus as described above,
[0102]
{Circle around (1)} When the substrate is taken out of the apparatus, a heating time for heating the substrate again is required, resulting in unnecessary processing time.
(2) HfO formed at low temperature₂The surface of the film is easily contaminated by the atmosphere outside the apparatus, and is liable to change with time (which causes deterioration of the electrical characteristics of the device).
There are disadvantages like this.
[0103]
To eliminate this disadvantage, RTA processing may be performed before forming the electrodes. Even in the case of the cluster device shown in FIG.₂If the RTA process is performed in the third reaction chamber 45 after the film is formed (the second reaction chamber 44), there is no problem even if the subsequent electrode formation is performed by another apparatus. In general, the higher the density is at a higher temperature, the smaller the gap between the atoms becomes, and contaminants (H₂O and organic substances) are HfO₂It is difficult to diffuse into the film. Therefore, HfO₂This is because the film is annealed at a high temperature by the RTA process and densified, so that the film is less likely to be contaminated in an atmosphere outside the device or to be changed with time.
[0104]
(10) Modified example
In the above-described embodiment, the source gas supplied to the substrate in the film forming step and the oxygen radical as the reactant supplied to the substrate in the reforming step react from the same supply port by sharing the shower head. Although the interior is supplied indoors, the interior space of the shower head may be divided into one for film formation and one for reactants, and the source gas and the reactants may be supplied from separate supply ports. In this case, when supplying the source gas to the substrate from the supply port for the source gas in the film forming step, a non-reactive gas is supplied to the supply port for the reactant, and the substrate is supplied from the supply port for the reactant in the reforming step. When supplying a reactant to the reactor, a non-reactive gas may be supplied to the supply port for the raw material gas. In this way, when the source gas and the reactant are supplied from separate supply ports, and a non-reactive gas such as an inert gas is supplied from a supply port that is not involved in each step in each step, the supply gas is supplied to the inside of the supply port. Accumulative film formation can be sufficiently suppressed. Hereinafter, this will be described in detail with reference to FIG. The configuration shown in FIG. 9 is the same as the configuration shown in FIG. 1 except that a partition plate 15 is provided on the shower head 6.
[0105]
When the raw material adsorbed in the showerhead 6 reacts with oxygen radicals as a reactant, an accumulated film is formed also in the showerhead 6. In order to suppress the formation of the accumulated film, the shower head 6 is divided into two (6a, 6b) by the partition plate 15. By partitioning the shower head 6 to which the source gas and the oxygen radical are supplied, the reaction between the source and the oxygen radical can be effectively prevented.
[0106]
In addition to partitioning the shower head 6, when flowing a film-forming gas further to the substrate 4, an inert gas is flowed from the radical supply side (reactant activation unit 11) to the activation gas shower head 6 b, and the oxygen radical When flowing to the substrate 4, it is preferable to flow an inert gas from the material supply side (the film formation material supply unit 9 and the inert gas supply unit 10) to the film formation shower head 6 a. In this way, when the inert gas is supplied to the shower head portions 6b and 6a not used in the film forming step and the reforming step, the formation of the accumulated film inside the shower head 6 can be more effectively suppressed. it can.
[0107]
The shower head 6 applied to FIG. 9 can be configured in various shapes. FIG. 10 shows various shapes of such a shower head 6. The shower heads of various shapes shown in FIGS. 10A to 10E have the same configuration in the following points. The shower head 6 has 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 two shower head portions 6a and 6b which partition the gas space 27. And a partition plate 15 to be divided. The raw material supply pipe 5 and the radical supply pipe 13 are connected to the two shower heads 6a and 6b from the back plate 17 side of the shower head 6 configured as described above.
[0108]
In FIG. 10A, the gas space 27 has a disk shape, the partition plate 15 is provided in the diameter direction of the disk shape gas space 27, and the shower head portions 6a and 6b are provided on the left and right. In FIG. 10B, the gas space has a disk shape, but the partition plate 15 is provided concentrically with the disk-shaped gas space, and the shower head portions 6a and 6b are provided in a coaxial double tubular shape. ing.
[0109]
In FIGS. 10A and 10B described above, the basic shape of the shower head 6 is a point-symmetric circle, but in this embodiment, the substrate is rotated. It is also possible to take a shape such as a semicircle or a rectangle. FIGS. 10C to 10E show such an example.
[0110]
In FIG. 10C, 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 shower heads 6a and 6b are provided on the left and right. In FIG. 10D, the gas space has a rectangular disk shape, the partition plate 15 is provided in the center, and the shower heads 6a and 6b are provided on the left and right. FIG. 10 (e) has a square disk shape, the partition plate 15 is provided in the center, and the shower heads 6 a and 6 b are provided on the left and right. Thus, the shower head 6 can be configured in various shapes.
[0111]
In the above-described embodiment, particularly, in a configuration including the following (1) to (3), HfO₂The case of forming a film has been described.
(1) A film forming gas used in the film forming step and a radical as a reactant used in the reforming step are supplied from the same supply port (shower head) so that both are mixed. In a modified example, they are supplied at different supply ports (separated shower heads) so that they are not mixed.
(2) During the supply of the film forming gas or the oxygen radical as the reactant, the oxygen radical or the film forming gas as the reactant to be used in the next step is exhausted from the bypass pipe, and the valve is switched to immediately perform the next step. Supply of oxygen radicals or film forming gas used in step (1).
(3) Simplify maintenance by using a common trap for the film forming step and the reforming step.
However, the present invention relates to HfO₂It is not limited to the formation of a film. For example, Ta₂O₅It is also applicable to the formation of other types of films such as films.
[0112]
【Example】
FIG. 11 shows a film formation sequence of a new MOCVD method using periodic remote plasma oxidation (RPO) in this embodiment (a procedure of a cycle method in which film formation by MOCVD and RPO are repeated a plurality of times). Here, the processing was performed using the substrate processing apparatus of FIG.
[0113]
Place a silicon wafer as a substrate on the susceptor in the reaction chamber, and when the temperature of the silicon wafer is stabilized,
(1) Gaseous Hf- (MMP) vaporized by a vaporizer₄Raw material (MO-Precursor) or dilution N₂At the same time, and is introduced into the reaction chamber for ΔMt seconds.
(2) Then, gaseous Hf- (MMP)₄The introduction of the raw materials is stopped, and the reaction chamber is diluted with N₂Purged 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 △ Rt seconds. During this time, dilution N₂Is being introduced.
(4) After the introduction of oxygen activated by the remote plasma is stopped, the reaction chamber is again diluted with N₂Purged for ΔIt seconds.
(5) Steps (1 cycle) from (1) to (4) are repeated (n cycle) until the film thickness reaches a desired value (thickness).
In this embodiment, Hf- (MMP)₄Flow rate of 0.05 g / min, diluent gas N₂Was set to 0.5 SLM (standard liter per minute), and the flow rate of oxygen introduced into the remote plasma unit was set to 0.1 SLM. The pressure in the reaction chamber was controlled to be kept at 100 Pa by an APC (auto pressure control) valve provided in the exhaust line. HfO₂In order to measure the deposition rate (film formation rate) of the film, the silicon substrate was used after removing the natural oxide film on the surface with a 1% diluted HF solution.
[0114]
FIG. 12 shows an n-MOS capacitor structure for measuring current-voltage characteristics (IV characteristics) and capacitance-voltage characteristics (CV characteristics), and a manufacturing process flow thereof.
[0115]
First, a p-type silicon wafer whose elements were separated by the LOCOS method was used for manufacturing an n-MOS capacitor. HfO₂Prior to film formation, the silicon surface was etched with a 1% diluted Hf solution to remove the native oxide and contaminants (Cleanning-DHF + DIW + IPa). Subsequently, NH₃The silicon surface was nitrided by performing rapid thermal annealing at 600 ° C. for 30 seconds in an atmosphere (Surfacen nitridation). Thereafter, the cycle processing (HfO₂  HfO by deposition by MOCVD via cyclic RPO)₂A film is formed and N₂Annealing was performed at 650 ° C. for 15 minutes in an atmosphere (post deposition annealing). Subsequently, a TiN film having a thickness of 80 nm was formed on the TiCl film to form a gate electrode.₄And NH₃Is grown at 650 ° C. by a chemical vapor deposition (CVD) method (Gate Electrode-CVD TiN), and a mask is formed by photolithography and the area is 1000 to 10000 μm by etching.²The gate electrode of the MOS capacitor was formed. HfO₂The equivalent oxide thickness (EOT) of the film is 10,000 μm in area²CV curve was measured using the CVC program developed by NCSU. The IV characteristic has an area of 1000 μm²Was measured at a temperature of 100 ° C. Further, in order to examine the quality of the film, TDS (thermal desorption spectroscopy) characteristics and SIMS (Secondary Ion Mass Spectroscopy) profiles were also measured. In addition, a high-resolution TEM ([HRTEM] cross-section high-resolution transmission electron microscopy) image was also observed to examine the crystal structure of the film.
[0116]
FIG. 13 shows a HfO film formed using the above-described cycle method.₂The substrate temperature dependence of the growth rate of the thin film is shown (black dots in the figure). The vertical axis shows the growth rate (Growth Rate), and the horizontal axis shows the temperature (Temperature). Each step time of △ Mt, △ It, and △ Rt in the cycle method was 30 seconds. HfCl performed by Cho et al. As a comparative example₄And H₂HfO by ALD using O₂Are also shown (open dots in the figure). The film formation rate is expressed in units of nm / min for comparison with data such as Cho.
[0117]
HfCl₄And H₂In the case of ALD using O, the film formation rate decreased from 1.2 nm / min to 0.36 nm / min as the substrate temperature (growth temperature) was changed (increased) from 180 ° C. to 400 ° C. This is because, in the case of ALD, the amount of the raw material adsorbed on the wafer surface is reduced by increasing the substrate temperature. However, in the case of the new cycle method invented by the present inventors, the film formation rate changes from 0.3 nm / min (0.6 nm / cycle) to 1 as the substrate temperature (growth temperature) is raised from 300 ° C. to 490 ° C. It increased to 0.5 nm / min (3 nm / cycle). This is because the self-decomposition of the raw material is promoted by increasing the film forming temperature. Since it takes time for the flow rate to stabilize in the used liquid mass flow controller, it is known that, of the ΔMt of 30 seconds, only 8 seconds actually contributes to the film formation. Therefore, at a low temperature, the deposition rate is lower than that of ALD. If the time during which the raw material actually contributes to film formation can be increased, the film formation rate can be made higher than that of ALD even at a low temperature.
[0118]
HfO with a film thickness of 30 nm formed by different number of cycles using a cycle method₂The thin films were evaluated by TDS. FIGS. 14 (a), (b) and (c) respectively show HfO₂Thin film hydrogen, H₂2 shows TDS spectra of O and CO. The four spectra in the figures (a), (b) and (c) are HfO films formed by the cycle method at 425 ° C. at 1, 10, 20, and 40 cycles, respectively.₂It concerns a thin film. Further, the step times of the 1, 10, 20, and 40 cycle processes are 1200, 120, 60, and 30 seconds, respectively. In other words, the films formed in 1, 10, 20, and 40 cycles have been subjected to the RPO processing for every 30, 3, 1.5, and 0.75 nm, respectively.
[0119]
From FIG. 14A, it can be seen that the desorption of hydrogen from the sample of 10, 20, and 40 cycles is dramatically reduced as compared with the sample of 1 cycle. 14 (b) and 14 (c) that the desorption of CO hardly changes with the number of cycles,₂It can be seen that the desorption of O gradually decreases as the number of cycles increases. The present inventors compared the TDS spectra of the sample that had been previously subjected to the RPO treatment and the sample that had not been subjected to the RPO treatment, and₂The RPO after thin film formation is composed of hydrogen and H₂It was determined that it was effective in reducing O contamination. From these facts, the periodic RPO is not hydrogen or H₂It can be said that it is effective in reducing the mixing of O.
[0120]
Also, Hf- (MMP)₄HfO by₂In order to investigate the mechanism of impurity contamination in the thin film, Hf- (MMP)₄Was investigated as follows.
[0121]
First, Hf- (MMP)₄The solution was left at 300 ° C. for 5 hours in Ar gas, then diluted with toluene, and analyzed by GC-MS (Gas Chromatography-Mass Spectroscopy). The by-product detected was Hf- (MMP)₄, (CH₃)₂C = CHOCO₃(Olefin), (CH₃)₂CHCHO (isobutylaldehyde), (CH₃)₂CHCH₂OH (isobutanol), CH₃OH (methanol), CH₃C (= 0) CH₃(Acetone). Olefin is generated by separating the HfO-C bond and separating hydrogen (H) bonded to carbon (C) at the β-position of MMP. Isobutyraldehyde, isobutanol, methanol, and acetone are considered to be formed by decomposition of H-MMP and olefin. Hf- (MMP)₄The following equation is considered appropriate as a reaction model for
Hf (MMP)₄→ Hf (OH) + 4olefin (4)
Or
Hf (MMP)₄→ HfO₂+ 2H (MMP) + 2olefin (5)
Here, from equation (4), Hf− (MMP)₄HfO deposited by MOCVD using₂It is expected that hydrogen will enter easily. This means that the previously measured MOCVD HfO₂It is also confirmed from the TDS spectrum of the film, which is consistent with the fact. However, according to FIG. 14, since the film subjected to the RPO treatment for each film thickness of 3 nm or less hardly contains hydrogen, the RPO treatment completely oxidizes Hf (OH) as shown in the following equation. Seems to be doing.
Hf (OH) + O * → HfO₂+ 1 / 2H₂                        (6)
Or
2Hf (OH) + 3O * → 2HfO₂+ H₂O (7)
O * is an oxygen radical.
Here, even if the reaction of the formula (7) occurs on the surface of the deposited film, H₂Since O is exhausted, it is considered that O is hardly taken into the film. However, since oxygen radicals (O *) also react with Hf (OH) present in the film, HfO₂H in the thin film₂O will be taken in. As a result, as shown in FIG. 14, the HfO film formed by using the cycle technique is formed.₂Even in thin films, H₂O exists and its H₂The contamination due to the incorporation of O decreases as the film thickness in one cycle of the RPO process decreases.
[0122]
FIG. 15 shows a HfO film formed at 425 ° C. by a conventional MOCVD method.₂(MOCVD at 425 ° C.) and HfO films formed at 300 ° C. and 425 ° C. by a cyclic method₂3 shows SIMS profiles of carbon ((a) carbon) and hydrogen ((b) hydrogen) of a sample (Cyclic Method at 300 ° C., 425 ° C.). The thickness of these samples is about 5 nm. Samples at 300 ° C. and 425 ° C. were deposited at 100 and 10 cycles, respectively, with a step time of 30 seconds.
[0123]
From FIG. 15, the amounts of carbon (C) mixed in the MOCVD method and the cycle method at 300 ° C. and the cycle method at 425 ° C. are 1.4, 0.54 and 0.28 at. %. The amount of hydrogen (H) mixed in the sample at 300 ° C. in the MOCVD and the cycle method and at 425 ° C. in the cycle method was 2.6 and O. 8, 0.5 at. %. The result that the cyclic method has less contamination of C and H than the MOCVD method indicates that the cyclic method is effective in reducing the contamination of C and H. According to a report by Kukli et al., The amount of hydrogen mixed into films formed at 300 ° C. and 400 ° C. by ALD 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 cause of the decrease in the amount of carbon contamination is as follows. As shown in the above equations (4) and (5), Hf- (MMP)₄Is introduced, Olefin and H-MMP are generated. Also, various types of alcohols are produced by the decomposition of Olefin and H-MMP. Most of these by-products are exhausted from the surface of the film, but some adsorb to the surface. Here, by the RPO step, these adsorbed substances become CO, CO₂, H₂It is decomposed into O and the like, and is exhausted from the thin film surface in the next purge step. Chen et al. Introduced ZrO in a “pulse mode” such as introducing MO material and oxygen with a 15-second exhaust gas.₂A thin film is formed, and the amount of C mixed is 0.1 at. %, But this is also thought to be due to the decomposition of organic matter in the oxygen introduction step and the evacuation in the subsequent evacuation step. However, the present invention is advantageous over the method of Chen et al. In that remote plasma oxygen, which is more active than oxygen, is used, and the decomposition efficiency of alcohol and the like is high. Further, it can be seen that the amount of impurities in the cycle method is reduced by increasing the film forming temperature. This is because the amount of by-product adsorbed decreases as the film formation temperature increases. For these reasons, it is concluded that in the cycle method, it is better to increase the material introduction time ΔMt and increase the remote plasma introduction time ΔRt. Also, it can be said that the higher the film forming temperature is, the higher the temperature is, unless the raw material is decomposed in the gas phase.
[0124]
HfO₂Many metal oxides such as films have a property that a crystallized structure is easily formed in the film when the temperature is increased as shown in FIG. In the conventional MOCVD method, a large number of crystallized portions were already contained in the film by deposition at 300 ° C. or higher. However, in the present invention, the crystallization temperature is shifted to a higher temperature side as shown in FIG.₂It has been found that a film is obtained. The TEM photograph shown in FIG. 17 shows one example, and it has been found that the amorphous structure is maintained even at a temperature at which crystallization has conventionally been performed.
[0125]
FIGS. 17 (a) and (b) are HRTEM images of samples deposited at 425 ° C. for 1 and 4 cycles, with step times of 120 and 30 seconds, respectively. HfO₂Before thin film formation, NH₃The annealing forms an interface layer of 0.8 nm. In the TEM image, the black portion is HfO containing Hf₂It is a film (heavier atoms look blacker). Generally, it is called amorphous if there is no regularity in that part, and it is said to be crystallized if there is regularity. However, it can be considered that the film is amorphous even if it is partially crystallized in the whole film (in a large meaning).
[0126]
From FIGS. 17A and 17B, since the interface layers in the first and fourth cycles are 1.7 nm and 1.6 nm, the step time of the RPO process affects the formation of the interface layer. It is thought that there is no. However, in another experiment, the base material and HfO₂It has been confirmed that the thickness of an undesired interface layer formed between the films can be made smaller than that of a film formed by the conventional MOCVD method. From FIG. 17, HfO deposited in one cycle₂HfO formed in 4 cycles while the thin film is more crystallized₂It can be seen that the thin film has an amorphous structure. Kukli et al. Reported that ZrO formed by ALD₂The film reportedly had an amorphous structure at 210 ° C., but crystallized at 300 ° C. Aarik et al. Have developed HfO films formed at 300 ° C. by ALD.₂It reports that the membrane had been turned off. From these facts, it can be said that the cycle method of the present invention is a method suitable for maintaining a film in an amorphous structure. In addition, when the film thickness uniformity was examined, it was also confirmed that the film formed in four cycles was better than the film formed in one cycle.
[0127]
FIG. 18 shows a HfO film formed at 425 ° C. by the MOCVD method and the cycle method.₂4 shows the relationship between the EOT of the capacitor and the leakage current measured at -1V. The vertical axis indicates the leak current (Jg ＠ -1 V), and the horizontal axis indicates EOT. HfO₂Before thin film formation, NH₃The annealing forms an interface layer of 0.8 nm. HfO formed by cycle method₂The thicknesses of the thin films are 2.3, 3.1, 3.8, and 4.6 nm, respectively. HfO formed with different thickness by MOCVD method₂Among the films, only those having a film thickness of 5 nm or more were obtained from the CV characteristics. The white dots and the black dots indicate the results when the films were formed by the MOCVD method and the cycle method, respectively.
[0128]
As shown in FIG. 18, HfO deposited by the cycle method₂It can be seen that the leakage current of the thin film is 1/100 or less of the film formed by the MOCVD method. The reason that the leak current was reduced by the cycle method is that HfO₂This means that impurities in the film are reduced and the film structure is in an amorphous state.
[0129]
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 forming temperature and shortening the time for introducing the raw material. It was also found that the film formed by the cycle method had an amorphous structure, and the cycle method was preferable to maintain the amorphous structure. As a result, HfO₂The leakage current of the film decreased. Further, by the cycle method, the film thickness uniformity can be improved as compared with the conventional film formation by MOCVD.₂It has also been found that the thickness of the interface layer formed between the films can be reduced.
[0130]
【The invention's effect】
According to the present invention, a metal oxide film is formed without using a gas containing an oxygen atom in a film forming process, so that a specific element in the metal oxide film is effectively removed in a reforming process to remove the film. It can be easily modified.
[0131]
In addition, since the film forming gas and the reactant are supplied from the same supply port, the foreign matter attached to the inside of the supply port can be covered with a thin film, and the foreign matter can be prevented from falling onto the substrate. By-products and cleaning gas adsorbed inside the supply port can be removed.
[0132]
In particular, when the formation of the Hf-containing film and the modification of the film using the reactant are continuously performed, the specific element in the Hf-containing film formed in the film formation step is promptly removed to form the film. Can be modified. In this case, when the thickness of the Hf-containing film formed at one time is 0.5 to 30 (1/6 atomic layer to 10 atomic layer), the modification treatment can be performed in a state where crystallization is difficult. The film can be modified by effectively removing impurities.
[0133]
Further, after forming the thin film, if the electrodes are formed without performing an annealing step as a separate step from the electrode forming step, and the processes from the formation of the thin film to the formation of the electrodes are performed in the same apparatus, the throughput can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view of a reaction chamber in an embodiment.
FIG. 2 shows the degree of Hf—O—Hf bond as HfO₂FIG. 7 is a diagram comparing a case where a film is formed without oxygen and a case where a film is formed with oxygen when forming a film.
FIG. 3 HfO₂The amount of impurities (—OH, CH, CO) contained in the film is determined by HfO₂FIG. 7 is a diagram comparing a case where a film is formed without oxygen and a case where a film is formed with oxygen when forming a film.
FIG. 4 Cycle number and HfO₂5 is a graph showing the relationship between the total amount of C and H impurities in a film.
FIG. 5: HfO on substrate₂It is sectional drawing which shows the state in which the film was formed.
FIG. 6 is a graph showing the relationship between the number of cycles and insulation characteristics.
FIG. 7 is a conceptual diagram showing a configuration of a cluster device according to an embodiment.
FIG. 8 shows an HfO with a cluster device configuration according to a conventional example and an embodiment.₂4 is a graph showing electrical characteristics of a film.
FIG. 9 is a schematic explanatory view of a reaction chamber in a modified example.
FIG. 10 is an explanatory diagram showing various examples of a shower head shape according to the embodiment.
FIG. 11 is a diagram showing a film forming sequence by a cycle process of MOCVD and RPO in the example.
FIG. 12 is a diagram illustrating an n-MOS capacitor structure used for measurement of CV characteristics and IV characteristics in an example and a manufacturing procedure thereof.
FIG. 13 shows a HfO film formed by a cycle process.₂FIG. 4 is a diagram showing the substrate temperature dependence of a film growth rate.
FIG. 14 shows a HfO film formed by changing the number of cycles.₂Hydrogen in the film, H₂It is a figure which shows the TDS spectrum of O and CO.
FIG. 15 is a diagram showing SIMS profiles of (a) carbon and (b) hydrogen of a sample formed by a conventional MOCVD method and a cycle process in an example.
FIG. 16 is a comparison diagram of a conventional example showing the temperature characteristics of the degree of crystallization and the present invention.
FIG. 17 is a diagram showing HRTEM images of samples formed in one cycle and four cycles.
FIG. 18 shows a conventional MOCVD method and HfO formed by a cycle process in the embodiment.₂FIG. 4 is a diagram showing a relationship between EOT of a capacitor and a leakage current.
FIG. 19 is a conceptual explanatory view of a CVD reaction chamber in a conventional example.
FIG. 20 is a conceptual diagram showing a configuration of a cluster device in a conventional example.
[Explanation of symbols]
1 Reaction chamber
4 Substrate
5 Raw material supply pipe
6 shower head
7 Exhaust pipe
9 Film forming material supply unit
11 Reactant activation unit
14 Bypass pipe
15 Partition plate
16 traps
25 Control device

Claims (5)

A film forming step of forming a metal oxide film on a substrate using a source gas obtained by vaporizing a source material containing oxygen atoms and metal atoms without using a gas containing oxygen atoms other than the source gas;
A reforming step of reforming the metal oxide film formed in the film forming step using a reactant different from the source gas,
Is repeated a plurality of times continuously. The film forming step of supplying a film forming gas on the substrate to form a thin film and the reforming step of supplying a reactant different from the film forming gas to reform the thin film formed in the film forming step are the same. In a method for manufacturing a semiconductor device that is continuously repeated a plurality of times in a reaction chamber,
A method for manufacturing a semiconductor device, wherein a film forming gas supplied to a substrate in the film forming step and a reactant supplied to the substrate in a reforming step are supplied from the same supply port. A film forming step of forming a film containing Hf on a substrate by using a material gas obtained by vaporizing a material containing Hf;
A reforming step of reforming a film containing Hf formed in a film forming step using a reactant different from the source gas;
Is repeated a plurality of times continuously. 4. The method according to claim 3, wherein the thickness of the Hf-containing film formed in one film forming step is 0.5 to 30 degrees. The film forming step of supplying a film forming gas on the substrate to form a thin film and the reforming step of supplying a reactant different from the film forming gas to reform the thin film formed in the film forming step are the same. After forming a thin film on the substrate by continuously repeating a plurality of times in the reaction chamber, a step of transferring the substrate from the reaction chamber to another reaction chamber via the transfer chamber without exposing the substrate to the atmosphere,
Forming an electrode on a thin film formed on a substrate in another reaction chamber. A method for manufacturing a semiconductor device, wherein a process from formation to formation of an electrode is performed in the same device.

Images