JP3181570B2 - Method of forming metal oxide film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to, for example relates to the formation how the metal oxide film suitable for an insulating film such as tantalum oxide.

[0002]

2. Description of the Related Art In general, a semiconductor device is manufactured by repeatedly performing a film forming process and a pattern etching process on a semiconductor wafer to manufacture a desired device. The specifications are becoming stricter year by year as the integration and integration increase,
For example, a very thin oxide film such as an insulating film or a gate insulating film of a capacitor in a device is required to be further thinned, and at the same time, a higher insulating property is required.

As these insulating films, a silicon oxide film, a silicon nitride film or the like can be used.
Recently, a metal oxide film such as tantalum oxide (Ta ₂ O ₅ ) has tended to be used as a material having better insulating properties. Although this metal oxide film exhibits a highly reliable insulating property even if it is thin, it is possible to further improve the insulating property by performing a surface modification treatment after forming the metal oxide film. Discovered,
Japanese Patent No. 283022 discloses the technique.

In order to form this metal oxide film, for example, a case of forming tantalum oxide will be described. As disclosed in the above-mentioned publication, a metal alkoxide which is an organic compound of tantalum is used as a raw material for film formation. (Ta (O
C ₂ H ₅ ) ₅ ) is supplied while bubbling with nitrogen gas or the like to maintain the semiconductor wafer at a process temperature of, for example, about 400 ° C., and to perform CVD (Che) under a vacuum atmosphere.
A tantalum oxide film (Ta ₂ O ₅ ) is laminated by a physical vapor deposition. In order to further improve the insulation properties as necessary, the semiconductor wafer is carried into an atmosphere containing ozone, and the semiconductor wafer is irradiated with ultraviolet rays from a mercury lamp under atmospheric pressure to activate the active oxygen atoms. Is generated, and the active oxygen atoms are used to decompose and desorb organic impurities such as C—C bonds contained in the metal oxide film, thereby modifying the tantalum oxide film. Good insulating film is obtained.

For example, FIG. 8 shows an example of a conventional method of forming a metal tantalum film as a metal oxide film of an insulating film. First, a vaporized metal alkoxide which is an organic compound is used as a metal oxide film material in a film forming apparatus. And the alcohol in a vaporized state is supplied to the semiconductor wafer W in this vacuum atmosphere.
To form a tantalum oxide layer (Ta ₂ O ₅ ) 2 having a predetermined thickness as a metal oxide film. The process temperature at this time is, for example, about 400 ° C.

Next, the wafer is transferred to a reforming apparatus, and as shown in FIG. 8B, the wafer surface is irradiated with ultraviolet rays UV by an ultraviolet lamp in an ozone (O ₃ ) atmosphere, thereby oxidizing the wafer. The C-C bonds and hydrocarbons of the organic impurities contained in the tantalum layer 2 are cut off by the energy of ultraviolet rays or active oxygen atoms and desorbed to modify the tantalum oxide layer. The reforming process is performed at a temperature lower than the crystallization temperature, for example, about 425 ° C. so as to maintain the amorphous state of tantalum oxide (amorphous state). After the modification process is completed, the wafer is then transferred to a heat treatment apparatus and heated to a temperature higher than the crystallization temperature of the tantalum oxide layer 2 in the presence of oxygen gas, for example, 700 ° C. or higher. The layer 2 is crystallized. By this crystallization annealing, the tantalum oxide layer 2 can be densified at the molecular level and the in-plane film thickness can be made uniform, so that an insulating film having good insulating properties can be obtained.

By the way, in consideration of the amount of ultraviolet rays permeated in the thickness direction of the metal oxide film and the degree of penetration of ozone, the thinner the metal oxide film is, the more effective the desorption of organic impurities during the above-mentioned reforming treatment is. Since the film formation process and the reforming process are repeated twice, and finally the crystallization process is performed, the individual reforming processes can be effectively performed, thereby further improving the insulating property. For example, Japanese Patent Application Laid-Open No. Hei 9-121035 discloses a technique for improving the image quality. FIG. 9 shows an example of a conventional film forming method at this time. First, as shown in FIG.
8C, a film of tantalum oxide 2A was formed in the same manner as shown in FIG. 8A in the presence of a metal alkoxide and an alcohol atmosphere, and then, as shown in FIG. Tantalum oxide layer 2A by irradiating UV
Is reformed. Next, as shown in FIG.
A second tantalum oxide layer 2B is formed under the same process conditions as in FIG. 9A, and then, as shown in FIG.
The second tantalum oxide layer 2B is reformed under the same process conditions as (B).

At this time, the thicknesses of the first and second tantalum oxide layers 2A and 2B are set so that the total thickness of the tantalum oxide layers 2A and 2B is substantially the same as the thickness of the tantalum oxide layer 2 in FIG. Therefore, the thickness of each tantalum oxide layer 2A, 2B is smaller than the thickness of tantalum oxide layer 2 shown in FIG. as a result,
Since the organic impurities can be effectively desorbed at the time of the individual reforming process by the reduced thickness, the insulating properties of the tantalum oxide layers 2A and 2B can be further improved. Then, the wafer subjected to the reforming process is shown in FIG.
As shown in FIG. 8E, heat treatment is performed under the same process conditions as those described with reference to FIG.
The second tantalum oxide layers 2A, 2B are simultaneously crystallized.

[0009]

In general, when a predetermined result is obtained by performing a predetermined series of processes, naturally, the smaller the number of steps, the lower the product cost. In addition, it is possible to reduce equipment costs and to improve the throughput by reducing the number of processes. However, in the conventional film forming method as described above, each step shown in FIGS. 8B and 8C and FIG.
Since the steps similar to each other as shown in FIG. 9D and those shown in FIG. 9E are performed by different heat treatment apparatuses, the number of steps is increased, resulting in an increase in product cost and a decrease in throughput. Was the result. The present invention has been devised in view of the above problems and effectively solving them. An object of the present invention is to provide a form how the metal oxide film can be formed with a small number of steps good metal oxide film of the electrical characteristics. Another object of the present invention is to provide continuous crystallization process the reforming process in the same chamber, or formation how the metal oxide film can be performed simultaneously.

[0010]

According to a first aspect of the present invention, an initial metal oxide film is formed on a surface of an object to be processed in an atmosphere in the presence of a vaporized metal oxide film raw material and an oxidizing gas. An initial film forming step of forming, an initial film crystallization step of exposing the object to be processed to a temperature equal to or higher than a crystallization temperature of the metal oxide film, and a metal oxide film raw material in a vaporized state on the surface of the initial film. A main film forming step of forming a main film of a metal oxide film in an atmosphere in the presence of an oxidizing gas; and a main film crystal for exposing the object to be processed to a temperature higher than a crystallization temperature of the metal oxide film. And forming a metal oxide film. This makes it possible to form a metal oxide film having good electrical characteristics in a small number of steps. Further, since the main film is deposited on the crystallized initial film, the deposition density of the main film is improved, and accordingly, the electrical characteristics can be improved.

As defined in claim 2, between the main film forming step and the main film crystallization step, the object to be processed is kept under an active oxygen atom atmosphere at a temperature lower than a crystallization temperature of the main film. A main film reforming step of exposing to a state and modifying the state may be performed. According to this, the insulating property of the main film can be improved by the reforming treatment, and the active oxide atoms that permeate the main film at the time of the reforming are blocked by the crystallized initial film of the base and permeate further downward. Therefore, it is possible to further improve the electrical characteristics in combination.

As defined in claim 3, between the initial film forming step and the initial film crystallization step, the object to be processed is kept under an active oxygen atom atmosphere at a temperature lower than a crystallization temperature of the initial film. An initial film reforming step of modifying the film by exposing it to a state may be performed. According to this, since the underlying initial film is also modified prior to crystallization, it is possible to further improve the overall insulating properties. Further, the main film forming step, the main film modifying step, and the main film crystallization step may be repeatedly performed in this order a plurality of times. According to this, when forming a thick main film, it is possible to completely modify and crystallize the main film by dividing and processing the main film. It is possible to improve the electrical characteristics as compared with.

The invention defined in claim 5 is an initial film forming step of forming an initial film of a metal oxide film on the surface of the object to be processed in an atmosphere in the presence of a vaporized metal oxide material and an oxidizing gas. An initial film reforming crystallization step of exposing the object to be processed to a temperature higher than the crystallization temperature of the initial film under an atmosphere of active oxygen atoms to simultaneously perform modification and crystallization; A main film forming step of forming a main film of the metal oxide film in an atmosphere in the presence of a metal oxide film raw material and an oxidizing gas in a vaporized state, and subjecting the object to be processed to an atmosphere of an active oxygen atom. A main film reforming crystallization step of simultaneously performing the reforming and the crystallization by exposing to a state higher than the crystallization temperature is provided. According to this, each of the initial film and the main film is subjected to the respective modification treatment and crystallization treatment at the same time.
Not only can the electrical characteristics of the metal oxide film be improved, but also the throughput can be improved by greatly reducing the number of processing steps.

According to a sixth aspect of the present invention, in the modification step and the modified crystallization step, the surface of the object may be irradiated with ultraviolet rays. According to this, the reforming process can be performed quickly and completely. As a metal oxide film raw material, a metal alkoxide is used, and as the metal oxide film, for example, a tantalum oxide layer is formed. In addition, ozone can be used as an active oxygen atom. Further, when tantalum oxide is used as the metal oxide film, the process temperature in the reforming step is lower than 700 ° C., and the process temperature in the crystallization step is 700 ° C. or higher.

[0015] In order to implement the above-mentioned film forming method, at least one of forming a metal oxide film in an atmosphere in the presence of an oxidizing gas and a metal oxide film material vaporized state with respect to the target object A film forming apparatus, a modification step of modifying the metal oxide film by exposing the target object to active oxygen atoms, and a crystallizing process by exposing the target object to a temperature equal to or higher than a crystallization temperature of the metal oxide film. Heat treatment apparatus capable of selectively or simultaneously performing a crystallization step for performing crystallization, and a common transfer apparatus commonly connected to the film forming apparatus and the heat treatment apparatus for transferring the object to be processed. Can be used.

[0016]

Be described in detail with reference to an embodiment of the formation how the metal oxide film according to the present invention in the following DETAILED DESCRIPTION OF THE INVENTION accompanying drawings. FIG. 1 is a schematic perspective view showing a film forming system according to the present invention. As shown in the figure, the film forming processing system 3 is configured such that an object to be processed, for example, a semiconductor wafer W, is vaporized in a vacuum atmosphere in the presence of a metal oxide film raw material and an oxidizing gas. Two film forming apparatuses 4 and 6 for forming an oxide film
And modifying the metal oxide film by exposing the metal oxide film to active oxygen atoms in a vacuum atmosphere, and crystallizing the wafer by heating the wafer to a temperature equal to or higher than the crystal temperature of the metal oxide film in the active oxygen atmosphere. Two heat treatment apparatuses 8 and 10 capable of simultaneously or selectively performing the crystallization treatment to be performed, and each of these apparatuses 4, 6, 8, and 1
It is mainly connected to a common transfer device 1 that is connected in common with the unit 0 and transfers a wafer between the devices while maintaining a vacuum state. Further, here, in order to improve the efficiency of loading and unloading wafers, a cassette C which can accommodate a plurality of semiconductor wafers and is evacuated and evacuated and connected to the common transfer device 1 in the cassette accommodation chamber 14A , 14
B, which is a so-called cluster tool.

One side of the common transfer device 1 is connected to the first cassette accommodating chamber 14 via gate valves G1 and G2, respectively.
A and the second cassette storage chamber 14B are connected to each other. These two cassette storage chambers 14A and 14B
It constitutes a wafer loading / unloading port of the entire apparatus, and includes a cassette stage (not shown) which can be moved up and down and swivel. The common transfer device 1 and the two cassette storage chambers 14A and 14B are each configured in an airtight structure, and the two cassette storage chambers 14A and 14B have gate doors G3 that can be opened and closed to and from the atmosphere of an external work chamber so as to be open to the atmosphere. , G4 provided and the gate door G opened
3. The cassette C is carried in / out via G4.

Transfer arm mechanism 16 in common transfer device 1
Is composed of a multi-joint arm that can be bent and extended, and can rotate. The cassette accommodation chambers 14A and 14B and the film forming devices 4 and
The wafer is transferred between the heat treatment apparatus 6 and each of the heat treatment apparatuses 8 and 10. The common transfer device 1 is provided with the film forming device 4, the heat treatment device 8, the heat treatment device 10, and the film formation device 6 via the gate valves G5, G6, G7, and G8, respectively.
Are connected. Each of the above-described devices 1, 4,
6, 8, 10 and the cassette storage chambers 14A, 14B
An N ₂ gas supply system (not shown) for purging an inert gas, for example, N ₂ gas, and a vacuum evacuation system (not shown) for evacuating the internal atmosphere are connected to each other. Controllable.

The film forming apparatuses 4 and 6 and the heat treatment apparatuses 8 and 10
May be used as disclosed by the present inventor in an earlier application (Japanese Patent Application Laid-Open No. 10-79377). In this case, the reforming device of the earlier application is used here as a heat treatment device. Each of the film forming apparatuses 4 and 6 is for forming, for example, a tantalum oxide (Ta ₂ O ₅ ) layer as a metal oxide film in an amorphous state on a wafer surface by CVD. A liquid metal alkoxide such as T
a (OC ₂ H ₅ ) ₅ is supplied by bubbling with, for example, He gas, and a CVD film forming reaction is performed in a mixed gas atmosphere of the supplied gas and an oxidizing gas such as O ₂ . The reason why two film forming apparatuses having the same structure are provided is to improve the throughput. Further, as the oxidizing gas, O ₂
Besides, O ₃ , N ₂ O, NO, NO ₂ , alcohol in a vaporized state, or the like can be used.

The heat treatment apparatuses 8 and 10 expose the surface of the wafer placed on a mounting table with a built-in heater to active oxygen atoms.
This apparatus selectively or simultaneously performs a reforming process for reforming a metal oxide film formed on a wafer surface and a crystallization process for crystallizing the metal oxide film. As active oxygen atoms, ozone (O ₃ ) may be introduced from the outside or generated internally, or active oxygen atoms may be generated using N ₂ O gas. In this case, an ultraviolet irradiation means 18 is provided on the ceiling or the like of the apparatus mainly for use in performing the reforming treatment, and the C—C bond or hydrocarbon existing in the metal oxide film is also utilized by utilizing the ultraviolet energy. And other organic impurities are decomposed and desorbed. The reason why the two heat treatment devices 8 and 10 are provided is to improve the throughput. This reforming process
In order to completely remove organic impurities, the process is mainly performed at a temperature lower than the crystallization temperature of the metal oxide film. The crystallization process is performed at a temperature equal to or higher than the crystallization temperature of the metal oxide film by increasing the power supplied to the heater. Further, when the reforming process and the crystallization process are performed simultaneously, they are performed at a temperature higher than the crystallization temperature.

Although the ultraviolet irradiation means 18 is provided to promote the processing, it is not limited to this and may not be provided. Further, a heating lamp which can quickly raise and lower the temperature of the wafer may be used instead of the heater. As the active oxygen atom, ozone (O ₃ ) may be introduced from outside or generated inside. As this heat treatment apparatus, for example, as disclosed in Japanese Patent Application Laid-Open No. H10-79377, active oxygen atoms such as ozone are generated by a plasma generation means using microwaves and introduced into a wafer in a chamber. A device adapted to do so can also be used.

Next, a film forming method of the present invention performed using the film forming system 3 configured as described above will be described. Here, a thin metal oxide film is used as an insulating film.
A description will be given by taking as an example the case of forming the initial film and the main film twice (two layers). First, the overall flow of the semiconductor wafer W will be described. On the surface of the wafer W, for example, a doped polysilicon film, a silicon nitride film, or the like is already formed in a previous step. The size of the wafer is, for example, 8
A cassette C containing, for example, 25 unprocessed wafers W is placed on a cassette stage (not shown) in the first cassette accommodating chamber 14A, and then the gate door G3 is closed. The interior of the chamber is set to an inert gas atmosphere of N ₂ gas, and the inside of the accommodation chamber 14 is evacuated.

Next, the gate valve G1 is opened, and the interior of the cassette accommodating chamber 14A is evacuated in advance and communicates with the common carrier 1 in an inert gas atmosphere. The wafer W is loaded by using. Next, the wafer W is loaded into one of the film forming apparatuses 4 which has been evacuated in advance through a gate valve G5, and as a metal oxide film as an initial film, for example, tantalum oxide (T
a ₂ O ₅ ) layer is formed. After the initial film forming step is completed, the wafer W is taken out into the common transfer apparatus 1 maintained in a vacuum state by using the transfer arm mechanism 16, and then the opened gate valve G6 is opened. Heat treatment apparatus 8 in which the wafer W is previously evacuated through
Carry in. Then, the wafer W is placed under an atmosphere of ozone or an atmosphere of an inert gas such as N ₂ here.
The initial film crystallization process is performed by holding the metal oxide film as the initial film, that is, the crystallization temperature of the tantalum oxide layer here, at a temperature raised to, for example, 700 ° C. or more, for a predetermined time and crystallizing the initial film. Perform

After the initial film crystallization step is completed, the wafer W is transferred again into the film forming apparatus 4 (or the film forming apparatus 6). Then, this wafer W
The main film forming step is performed by forming a predetermined thickness of, for example, a tantalum oxide layer as a metal oxide film serving as a main film on the surface of the substrate under the same process conditions as the initial film forming step. After the main film forming step is completed in this way,
This wafer W is again subjected to the heat treatment apparatus 8 (or the heat treatment apparatus 1).
(May be 0). Then, the wafer W is maintained at a temperature equal to or higher than the crystallization temperature of the main film for a predetermined time, and the main film is crystallized under the same process conditions as the initial film crystallization conditions, thereby performing the main film crystallization step. Do. After the main film crystallization step is completed, the processed wafer W is taken out into the common transfer device 1 and stored in the cassette C in the second cassette storage chamber 14B. become.

Next, each of the above steps will be described with reference to FIG. FIG. 2 is a diagram showing a first embodiment of the method of the present invention. First, as shown in FIG. 2A, a first tantalum oxide layer 20 is formed as an initial film on a wafer W in a first film forming apparatus 4.
Is formed with a predetermined thickness. The source gas at this time is supplied by bubbling Ta (OC ₂ H ₅ ) _5, which is a liquid metal alkoxide, with He gas, and at the same time, O ₂
Supply oxidizing gas such as. The supply amount of the metal alkoxide depends on the film formation rate, but is, for example, about several mg / min. Process pressure for film formation is 0.2-0.3 Torr
r, the process temperature is set in the range of 250 to 450 ° C., for example, 400 ° C., and the thickness t1 is, for example, 20 to 50.
The tantalum oxide layer 20 having a thickness of, for example, about 35 ° is formed. In this case, since an organic substance is used as a raw material, it is unavoidable that organic impurities are mixed in the tantalum oxide layer 20. Further, the tantalum oxide layer 20 is in an amorphous state, and as a result, The forming step is completed.

When the initial film forming step is completed as described above, the wafer W is carried into the heat treatment apparatus 8, and the process proceeds to the initial film crystallization step. In this initial film crystallization step,
As shown in FIG. 2B, for example, ozone is supplied as active oxygen atoms, or an inert gas such as N ₂ is supplied without supplying ozone, and the process pressure is set in a range of about 1 to 600 Torr. The process temperature is equal to or higher than the crystallization temperature of the tantalum oxide layer as the initial film, that is, 700 ° C.
C. or higher, for example, 800 ° C., and maintained for a predetermined time. Thus, the initial film 20 is crystallized. In this case, crystallization in an ozone atmosphere has an advantage that the generation of oxygen defects in the film can be prevented at the same time as the crystallization due to the effect of active oxygen atoms generated by the thermal decomposition of ozone.

After the initial film crystallization step is completed in this way, for example, the first
As shown in (C), a main film forming step of forming a second tantalum oxide layer 22 as a main film on the wafer W is performed. In this film forming step, a second tantalum oxide layer 22 in an amorphous state is formed as a main film as shown in FIG. The film forming conditions at this time are the same as those in the case of the initial film forming step performed previously, such as the raw material gas, the flow rate, the process pressure, the process temperature, etc., and the film thickness t2 is also the same as t1. For example, it is set to 20 to 50 degrees, for example, about 35 degrees. As described above, since the main film 22 is deposited on the crystallized initial film 20, the atoms of the main film 22 are arranged so as to follow the initial film in the crystallized state. It becomes possible to make it.

After the main film forming step is completed, the wafer W is transferred again, for example, into the heat treatment apparatus 8 and the main film 22 is crystallized as shown in FIG. Perform In this case, the process is performed under the same process conditions as the initial film crystallization step, the wafer W is set at a temperature higher than the crystallization temperature of the tantalum oxide layer, for example, 800 ° C., and maintained for a predetermined time, and the main film 22 is crystallized. I do. As a result of evaluating the insulating properties of the tantalum oxide layer thus formed, the leak current was very small, and the electrical characteristics could be improved. It is considered that the reason is that the main film 22 is formed on the crystallized initial film 20, so that the main film 22 is densified and contributes to the improvement of the electrical characteristics as described above.
Although the thickness t1 of the initial film 20 and the thickness t2 of the main film 22 are the same here, t1 <t2 may be satisfied. In this case, the initial film 20 is crystallized and becomes dense. Therefore, even if the main film 22 is sufficiently crystallized, there is an advantage that the oxidation of the interface between tantalum oxide and silicon can be suppressed, and an effective thinning can be achieved. This is the same in the other embodiments described below. In the first embodiment, the modification treatment of the tantalum oxide layer was not performed.
The tantalum oxide layer, which is the main film, may be modified.

FIG. 3 shows a second embodiment of the method of the present invention. In the second embodiment, between the main film forming step and the main film crystallization step of the first embodiment, the wafer is exposed to a state below the crystallization temperature of the main film in an atmosphere of active oxygen atoms. The main film reforming step of reforming the main film is performed. Therefore, each step of FIGS. 2A, 2B, 2C, and 2D
Corresponding to the steps of FIGS. 3A, 3B, 3C, and 3E, only the main film reforming step shown in FIG. 3D is added.
Here, the main film reforming step shown in FIG.
An example in which the main film reforming step shown in (1) is continuously performed in the same heat treatment apparatus will be described. That is, this second
In the embodiment, when the main film forming step is completed as shown in FIG. 3C, the wafer W is loaded into the heat treatment apparatus 8 and the process proceeds to the main film modifying step.

In this main film reforming step, FIG.
As shown in (1), for example, ozone is supplied as active oxygen atoms, and a large amount of ultraviolet light is irradiated from the ultraviolet irradiation means 18. As a result, the ozone is excited by the irradiation of ultraviolet rays, and further generates a large amount of active oxygen atoms, which oxidize organic impurities in the tantalum oxide layer 22 of the main film formed on the wafer surface, and at the same time, The energy of ultraviolet rays cuts and decomposes the C—C bond and the like of the organic impurity, and as a result, the organic impurity can be almost completely eliminated.
At this time, the wavelength of the ultraviolet light is 185 nm, 254 nm.
Irradiates a large amount of ultraviolet light mainly composed of
The process temperature is lower than 700 ° C., which is the crystallization temperature of the tantalum oxide layer 22, within the range of about −600 Torr.
For example, it is set to about 425 ° C. within a range of 320 to 700 ° C. If the process temperature is lower than 320 ° C., the withstand voltage is not sufficient. If the process temperature exceeds 700 ° C., crystallization starts and sufficient reforming cannot be performed. Although the modification time depends on the film thickness, it is preferably performed for 30 seconds or more, and here, for example, about 60 seconds.

When the thickness t1 of the tantalum oxide layer 20 is smaller than the above-described thickness, the reforming process may be performed by supplying only ozone without performing ultraviolet irradiation. When the main film reforming step is completed in this manner, the temperature of the wafer is rapidly increased in the same heat treatment apparatus 8 to increase the crystallization temperature to 700 ° C. or more, for example, 800 ° C.
The process proceeds to the main film crystallization step as shown in (D). Thereby, the second tantalum oxide layer 2 which is a metal oxide film of the main film is formed.
2 is modified, and the tantalum oxide layer 22 is crystallized at a crystallization temperature of 700 ° C. or higher. That is, in this step, it is possible to continuously perform the modification process and the crystallization process of the metal oxide film 22 as the main film in the same chamber. The process temperature at this time will be described in more detail with reference to FIG. 4. When the wafer W is loaded into the heat treatment apparatus 8 with both the temperature of the wafer W and the temperature in the heat treatment apparatus 8 being about 450 ° C., The state is maintained for a predetermined time, for example, about 2 minutes, and the reforming process of the main film 22 is performed. Then, immediately thereafter, the power supply to the heater in the apparatus is increased to rapidly raise the temperature of the wafer W. , 700 ° C or higher,
For example, the temperature is raised to 750 ° C. At this time, the heating rate is, for example, 100 ° C./sec.

At this time, the reforming process is performed on the tantalum oxide layer 22 of the main film while the temperature is raised to about 600 ° C. Then, in a temperature region exceeding 700 ° C., the crystallization of the tantalum oxide layer 22 is performed. Note that there is a width of about 100 ° C. between the upper limit of the reforming temperature of the tantalum oxide layer, 600 ° C., and the crystallization temperature of 700 ° C., because the crystallization occurs instantaneously after a certain temperature. Rather, it proceeds gradually with a certain temperature range. Therefore, this 600-700 ° C
During this time, the tantalum oxide layer 22 is reformed, and at the same time, crystallization is also started gradually, so that both processes proceed simultaneously and in parallel.

In this case, the time T1 for the modification of the tantalum oxide layer 22 depends on the thickness of the layer.
At about Å, set to about 120 sec. On the other hand, since the crystallization phenomenon occurs almost instantaneously,
The length of the above time T2 may be set to, for example, about 60 seconds. Further, the crystallization temperature is preferably in the range of 700 to 800 ° C. If the crystallization temperature is higher than 800 ° C., the base of the tantalum oxide layer is more oxidized, and the effective film thickness tends to increase.
In addition, there is an inconvenience that the thermal effect on the semiconductor device is large and the characteristics are deteriorated. The processed wafer is
At the same time as performing N ₂ gas purging in the heat treatment apparatus 8,
After the temperature is lowered to about 5 ° C. and the pressure is adjusted, it is carried out of the device 8.

In this case, the active oxygen atoms used for modifying the main film 22 penetrate the two tantalum oxide layers 20 and 22 and reach the lower layer, for example, the SiO ₂ film to promote the thickness of the SiO ₂ film. However, since the initial film 20 below the main film 22 has been subjected to the crystallization annealing treatment as described above, this crystallized initial film 20 is a protective film against active oxygen atoms, that is, It acts as a barrier and prevents further penetration of active oxygen atoms.
Therefore, by modifying the main film 22, it is possible to further improve the insulating properties (electrical properties) of the entire tantalum oxide layers 20, 22. In this case, in order for the crystallized initial film 20 to act as a barrier layer against active oxygen atoms, the thickness must be at least about 10 to 15 °.

Here, in order to evaluate the characteristics of the second embodiment, the entire tantalum oxide layers 20, 22 (70 mm =
(35 mm + 35 mm). For comparison, a 70 mm tantalum oxide layer is deposited at a time, not modified and crystallized, instead of being divided into two as an initial film and a main film as in the present invention. The insulation layer was evaluated. FIG. 5 is a graph showing the evaluation of the second embodiment and the evaluation of the comparative example at this time. The evaluation was performed both when the device was at room temperature and when it was at 90 degrees. As is clear from this figure, in the case of the comparative example, when the applied voltage is positive and negative at both room temperature and 90 degrees,
In both cases, the leakage current increases linearly in proportion to the applied voltage, which is not preferable in terms of characteristics. On the other hand, in the case of the second embodiment, the leakage current is very small up to about 1.5 V regardless of whether the applied voltage is positive or negative at both room temperature and 90 degrees, and good characteristics are obtained. It turned out to be showing.

In the second embodiment, the main film forming step, the main film reforming step, and the main film crystallization step are performed only once, but the reforming time depends on the thickness of the main film. If the main film is thick, for example, 50 ° or more, the main film is divided so that the thickness of one main film becomes 50 ° or less in order to shorten the entire processing time. Then, the above three steps may be repeated a plurality of times in that order to obtain a tantalum oxide layer having a desired thickness. In the second embodiment, the reforming process is performed only on the main film 22, but the reforming process may also be performed on the initial film 20.

FIG. 6 is a diagram showing a third embodiment of the method of the present invention. In the third embodiment, an initial film modifying step is performed between an initial film forming step and an initial film crystallization step in addition to the steps of the second embodiment. Accordingly, each of the steps of FIGS. 3A, 3B, 3C, 3D, and 3E corresponds to the steps of FIGS. 6A, 6C, 6D, 6E, and 6F. Corresponding to each step, only the initial film modification step shown in FIG. 6B is added. The process conditions of the initial film reforming step are the same as those of the main film reforming step of the second embodiment. That is, when the initial film forming step is completed as shown in FIG. 6A, the wafer W is loaded into the heat treatment apparatus 8 and the process proceeds to the initial film modifying step.

In this initial film reforming step, FIG.
As shown in (B), for example, ozone is supplied as active oxygen atoms, and a large amount of ultraviolet light is irradiated from the ultraviolet irradiation means 18. As a result, the ozone is excited by the irradiation of the ultraviolet rays, and further generates a large amount of active oxygen atoms, which oxidize the organic impurities in the tantalum oxide layer 20 of the initial film formed on the wafer surface, and at the same time, The energy of ultraviolet rays cuts and decomposes the C—C bond and the like of the organic impurity, and as a result, the organic impurity can be almost completely eliminated. At this time, the wavelength of the ultraviolet light is 185 nm, 2
A large amount of ultraviolet light having a wavelength of 54 nm is irradiated, the process pressure is in the range of about 1 to 600 Torr, and the process temperature is lower than 700 ° C., which is the crystallization temperature of the tantalum oxide layer 20, for example, in the range of 320 to 700 ° C. About 425 ° C. If the process temperature is lower than 320 ° C., the withstand voltage is not sufficient. If the process temperature exceeds 700 ° C., crystallization starts and sufficient reforming cannot be performed. Also,
Although the modification time depends on the film thickness, it is preferably performed for 30 seconds or more, and here, for example, about 60 seconds.

When the initial film reforming step is completed in this way, the wafer temperature is rapidly increased in the same heat treatment apparatus 8 as in the case of the transition to the main film crystallization step of the second embodiment. The temperature is raised to a crystallization temperature of 700 ° C. or more, for example, 800 ° C.
Then, the process proceeds to the initial film crystallization step as shown in FIG. In this case, since the initial film 20 is also modified, the quality of the initial film 20 is improved accordingly, and the characteristics of the entire insulating film can be further improved. Further, in the third embodiment, the modification process and the crystallization process of the tantalum oxide films 20 and 22 are performed continuously. However, the present invention is not limited to this, and in order to further shorten the processing time. Alternatively, the modification process and the crystallization process may be performed simultaneously.

FIG. 7 is a diagram showing a fourth embodiment of such a method of the present invention. In the fourth embodiment, the process shown in FIG. 6B and the process shown in FIG. 6C of the previous third embodiment are combined and represented as an initial film modification crystallization process (FIG. 7B). Further, the step shown in FIG. 6E and the step shown in FIG. 6F are combined to form a main film modifying crystallization step (FIG. 7D). In this case, both process temperatures are naturally set to 700 ° C. or more, for example, 800 ° C., which is the crystallization temperature of the tantalum oxide film, and ozone or the like is supplied as active oxygen atoms, or while ozone is supplied. Irradiates ultraviolet rays.

As described above, when the reforming process and the crystallization process are performed simultaneously, the number of steps is greatly reduced, and the throughput can be greatly improved. In the second and third embodiments, the reforming step and the crystallization step are performed continuously in the same chamber. However, both of these steps may be performed in different chambers. In the above embodiment, the case where the tantalum oxide layer is formed as the metal oxide film has been described as an example. However, the present invention is not limited to this. The titanium oxide layer, the zirconium oxide layer, the barium oxide layer, the strontium oxide layer, or the barium / strontium oxide layer is used. titanium oxide layer _{(Ba X Sr 1-X Ti} Y O
₃ ), PZT oxide layer (PbZr _1-x Ti _x O ₃ ), S
BT oxide (Sr _X Bi _1-x Ta _Y O _Z ), ZrSiO
Of course, the present invention can be applied to the case of forming a metal silicate layer such as ₄ or HfSiO ₄ and a compound layer of these oxides.

[0042]

As described in the foregoing, according to the formation how the metal oxide film of the present invention can exhibit excellent effects and advantages as follows. When forming the metal oxide film, after forming and crystallizing the initial film, the main film is formed thereon, so that the deposition density of the main film increases, and as a result,
Insulation characteristics can be improved and the number of entire steps can be reduced. In addition, by crystallizing the initial film, even if a modification process is performed in a later step, the initial film acts as a barrier against active oxygen atoms, and as a result, the characteristics of the insulating film can be maintained high. it can. Furthermore, by modifying the metal oxide film prior to crystallization, the quality of the film can be improved and the insulating property can be improved. In particular, by irradiating ultraviolet rays during the modification process or the crystallization process,
The modification of the metal oxide film on the surface can be performed quickly.
As a result, the product cost can be eliminated and the throughput can be improved. Further, by simultaneously performing the modification treatment and the crystallization treatment, the throughput can be further improved.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a film forming system according to the present invention.

FIG. 2 is a diagram showing a first embodiment of the method of the present invention.

FIG. 3 is a diagram showing a second embodiment of the method of the present invention.

FIG. 4 is a graph showing a change in process temperature when a reforming process and a crystallization process are continuously performed.

FIG. 5 is a graph showing the evaluation of the second embodiment and the evaluation of the comparative example.

FIG. 6 is a diagram showing a third embodiment of the method of the present invention.

FIG. 7 is a diagram showing a fourth embodiment of the method of the present invention.

FIG. 8 is a view showing an example of a conventional method for forming a metal tantalum film as a metal oxide film of an insulating film.

FIG. 9 is a view showing an example of a conventional film forming method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Common transfer chamber 3 Film-forming processing system 4,6 Film-forming apparatus 8,10 Heat treatment apparatus 16 Transfer arm mechanism 20 Initial film (first tantalum oxide layer) 22 Main film (second tantalum oxide layer) W Semiconductor Wafer (workpiece)

Continuation of front page (56) References JP-A-10-79377 (JP, A) JP-A-7-122621 (JP, A) JP-A-2-283022 (JP, A) JP-A 9-121035 (JP) JP-A-2000-164831 (JP, A) JP-A-2000-200889 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/316 H01L 21/31 C23C 16 / 00-16/56

Claims (11)

(57) [Claims] An initial film forming step of forming an initial film of a metal oxide film in an atmosphere in the presence of a raw material of a metal oxide film in a vaporized state and an oxidizing gas on a surface of the object to be processed; An initial film crystallization step in which the metal oxide film is exposed to a temperature equal to or higher than the crystallization temperature of the metal oxide film; and a metal oxide film is formed on the surface of the initial film in an atmosphere in the presence of a vaporized metal oxide film raw material and an oxidizing gas. A metal oxide film, comprising: a main film forming step of forming a main film of a film; and a main film crystallization step of exposing the object to be processed to a temperature equal to or higher than a crystallization temperature of the metal oxide film. Formation method. 2. Between the main film forming step and the main film crystallization step, the object to be processed is exposed to a temperature lower than the crystallization temperature of the main film in an active oxygen atom atmosphere to improve the condition. 2. The method for forming a metal oxide film according to claim 1, wherein a main film reforming step is performed. 3. An object to be processed is exposed to a temperature lower than a crystallization temperature of the initial film in an active oxygen atom atmosphere between the initial film forming step and the initial film crystallization step to improve the condition. 3. The method for forming a metal oxide film according to claim 1, wherein an initial film reforming step is performed. 4. The metal oxide film according to claim 2, wherein the main film forming step, the main film modifying step, and the main film crystallization step are repeated a plurality of times in this order. Forming method. 5. An initial film forming step of forming an initial film of a metal oxide film in an atmosphere in the presence of a metal oxide film raw material in a vaporized state and an oxidizing gas on a surface of the object to be processed; An initial film reforming and crystallization step of simultaneously performing modification and crystallization by exposing the film to a temperature higher than the crystallization temperature of the initial film under an active oxygen atom atmosphere, and forming a vaporized metal oxide film material on the surface of the initial film. A main film forming step of forming a main film of a metal oxide film in an atmosphere in the presence of an oxidizing gas; and setting the object to be processed in a state of at least the crystallization temperature of the main film in an active oxygen atom atmosphere. A method for forming a metal oxide film, comprising: a main film reforming crystallization step of simultaneously performing reforming and crystallization by exposure. 6. The method for forming a metal oxide film according to claim 2, wherein in the modifying step and the modified crystallization step, a surface of the object is irradiated with ultraviolet rays. 7. The method for forming a metal oxide film according to claim 1, wherein the metal oxide film raw material is a metal alkoxide. 8. The method according to claim 1, wherein the metal oxide film is made of tantalum oxide. 9. The method according to claim 2, wherein said active oxygen atoms are formed by ozone. 10. The process temperature of the reforming step is 70
The method for forming a metal oxide film according to claim 2, wherein the temperature is lower than 0 ° C., and the process temperature of the crystallization step is 700 ° C. or higher. 11. The oxidizing gas may be O ₂ , O ₃ , N
_{Of the 2} O, NO, NO ₂ and alcohol in the vaporized state,
The method for forming a metal oxide film according to any one of claims 1 to 10, wherein at least one of the metal oxide films is included.