JP2002164345A - Method of depositing film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of depositing film for precisely forming a tanta lum oxidation film having a small thickness that has very high in-plane uniform ity of the thickness, very small surface roughness, and moreover satisfactory electrical properties. SOLUTION: In the method of depositing film for forming the tantalum oxidation film on a surface of a treated body W in a treatment chamber 20 using raw material gas and oxidizer gas, an oxidizer applying step, in which the oxidizer gas is applied to a surface of the treated body, and a reaction step, in which the raw material gas is caused to act upon the applied oxidizer gas, so as to form the tantalum oxidation film, are repeated in this order for two or more times. As a result, a tantalum oxidation film with a small thickness that has very high in-plane uniformity of thickness can be formed precisely, with very small surface roughness, and moreover with satisfactory electrical characteristics, even at low temperatures.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a film forming method for depositing a tantalum oxide film.

[0002]

2. Description of the Related Art In general, in order to manufacture a semiconductor device, a film forming process and a pattern etching process are repeatedly performed on a semiconductor wafer to produce a desired device. The specifications, that is, the design rules, are becoming stricter year by year as the degree of integration increases.For example, even thinner oxide films such as the insulating film and gate insulating film of a capacitor in a device need to be made thinner. And at the same time higher insulation 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, for example, a tantalum oxide film (Ta ₂ O ₅ ) has tended to be used as a material having better insulating properties. This metal oxide film can exhibit highly reliable insulation even if it is thin. This metal oxide film is formed by, for example, taking the case of forming a tantalum oxide film as an example. As a raw material for film formation, pentaethoxy tantalum (Ta (O (O)), which is a metal alkoxide of tantalum, is used.
C ₂ H ₅ ) ₅ ) (hereinafter also referred to as PET) is vaporized by a vaporizer, and is supplied to a semiconductor wafer at, for example, 410 ° C.
CVD temperature under vacuum atmosphere
(Chemical Vapor Deposition
n), a tantalum oxide film (Ta ₂ O ₅ ) is laminated.

FIG. 9 shows an example of a capacitor structure when the tantalum oxide film is used as a gate insulating film or the like. That is, the source 2 and the drain 4 are formed on the surface of a semiconductor wafer W made of, for example, a silicon substrate, and the surface between the source 2 and the drain 4 is
A tantalum oxide film 8 made of Ta ₂ O ₅ is formed as a gate insulating film via an interface film 6 made of SiO ₂ or SiON or a mixture of both. A gate electrode 12 made of, for example, Al (aluminum) or W (tungsten) is laminated on the tantalum oxide film 8 via a barrier metal layer, for example, a TiN film 10 for preventing a chemical reaction with the gate electrode. Thus, a capacitor is formed. The interface film 6 underlying the tantalum oxide film 8 is an indispensable film for matching with the underlying silicon surface because the interface state density of the tantalum oxide film 8 needs to be suppressed within a predetermined range.

[0005]

By the way, the thickness of the tantalum oxide film 8 formed on the interface film 6 is extremely thin, at most about 100 °, because the design rule is stricter as described above. ing. The film forming rate of this tantalum oxide film is, for example, a high film forming rate of about 1500 ° / min during CVD film forming at a film forming temperature of about 600 ° C., but the tantalum oxide film 8 having a film thickness of about 100 ° In order to accurately deposit a tantalum oxide film having a thickness of about 100 °, an attempt has been made to lower the deposition rate by lowering the CVD film forming temperature to, for example, about 410 ° C. I have.

However, the relationship between the deposition rate of the tantalum oxide film and the incubation time is in an opposite relationship as shown in FIG. 10. For example, when the deposition temperature is lowered, the deposition rate is correspondingly reduced. Thus, the film thickness controllability is improved, but the incubation time tends to increase. Here, the incubation time is defined as a source gas (film-forming gas) at an early stage of the film-forming process.
Means that no target film is deposited on the surface of the wafer even when the wafer flows. The film formation state at this time is schematically shown with reference to FIG. 11. As shown in FIG. 11A, during the incubation period, amorphous Ta ₂ O ₅ seeds are formed on the surface of the interface film 6 of the wafer W. 14 are formed in a dispersed state, and after the incubation period,
For the first time, a film is deposited around the seed 14 at a stretch.
As shown in FIG. 1B, a tantalum oxide film 8 is formed. At this time, the surface of the formed tantalum oxide film 8 has
Since the uneven state of the scattered species 14 is reflected, a large uneven surface is obtained. Since the size of this species 14 increases substantially in proportion to the incubation time,
When the tantalum oxide film 8 is deposited by low-temperature CVD at about 10 ° C., the surface irregularities are further increased.

When such irregularities occur, a thick portion and a thin portion of the tantalum oxide film 8 are formed. For example, even if the thickness H1 of the thick portion is about 100 °, the film of the thin portion is formed. The thickness H2 becomes about 30 °, and as a result, there is a problem that a large electric field concentration occurs in a portion where the film thickness is small, and a leak current much larger than a designed value occurs. In addition, as described above, such a problem occurs not only when a tantalum oxide film is used as a gate oxide film, but also when, for example, a tantalum oxide film is used as a capacitor insulating film. This point is MIM
(Metal Insulator Metal) A capacitor having a structure will be described as an example. In FIG. 12A, reference numeral 3 denotes a capacitor such as ruthenium (Ru).
The lower electrode 3 is made of, for example, Si.
The lower electrode 3 is formed on an interlayer insulating film 5 made of O _2, and is connected to a lower diffusion layer (not shown) through a plug 7 made of, for example, tungsten. As a structure of the lower electrode 3, for example, there is a structure in which a SiN film or the like is deposited as a reaction preventing layer on doped polysilicon.

As shown in FIG. 12B, when a tantalum oxide film 8 is deposited as a capacitor insulating film on the lower electrode 3 and the interlayer insulating film 5 as described above, the above-mentioned incubation time occurs. , Lower electrode 3
While the film formation time delay on ruthenium is almost zero minutes, the film formation delay time on the interlayer insulating film SiO ₂ is about 7 minutes at the maximum. For this reason, the tantalum oxide film 8 has grown like an eyelet.
Due to the film formation delay time, the tantalum oxide film may be partially thinned, and in particular, the insulation failure portion 9 occurs at the boundary between the lower electrode 3 and the interlayer insulating film 5. In this case, as shown in FIG. 12C, an upper electrode 11 made of, for example, ruthenium is formed thereon,
When a voltage is applied between the electrodes 11, an electric field concentration occurs in the above-described insulation failure portion 9, and the electrical characteristics deteriorate.
There was also a problem.

In order to solve the above-mentioned problems, the present applicant has first developed a film forming method capable of accurately forming a thin tantalum oxide film having high in-plane uniformity of the film thickness even at a low temperature. (Japanese Patent Application No. 2000-080904). In this film forming method, an oxidizing agent is previously attached to the surface of a semiconductor wafer prior to CVD film formation of a tantalum oxide film, and a raw material gas is acted on the oxidizing agent to form an interface layer made of a thin tantalum oxide film. I have.

By the way, according to the above-mentioned film forming method, the film thickness uniformity of the tantalum oxide film could be sufficiently improved. However, the subsequent examination revealed that the surface roughness (roughness) was rather large, Insufficient characteristics were found, and it was found that the above film formation method was not sufficient.
The present invention has been devised in view of the above problems and effectively solving them. It is an object of the present invention to accurately form a thin tantalum oxide film having a very high in-plane uniformity of the film thickness and a very small surface roughness even at a low temperature, and a good electric characteristic. It is an object of the present invention to provide a film forming method that can be used.

[0011]

The inventors of the present invention have conducted intensive studies on a method of forming a tantalum oxide film. As a result, instead of CVD film formation involving a surface reaction and a gas phase reaction, the surface temperature was reduced by lowering the process temperature. MLD (M
LD: Molecular Layer Deposi
The present invention has been achieved by obtaining the finding that an ideal tantalum oxide film can be formed by repeatedly performing film formation. That is, the invention defined in claim 1 is a film forming method for forming a tantalum oxide film on a surface of an object to be processed in a processing vessel using a source gas and an oxidizing gas, The oxidizing agent adhering step of adhering the oxidizing gas and the reaction step of forming the tantalum oxide film by causing the source gas to act on the adhering oxidizing gas are repeated a plurality of times in this order. Things.

Thus, the entire tantalum oxide film is deposited by suppressing the gas phase reaction and causing a reaction mainly based on the surface reaction to form an extremely thin film of a molecular level in a plurality of layers one by one. Therefore, it is possible to accurately form a thin tantalum oxide film having very high in-plane uniformity of the film thickness, very small surface roughness, and excellent electric characteristics. In this case, for example, as defined in claim 2, between the oxidizing agent attaching step and the reaction step, the oxidizing gas or the raw material gas introduced into the processing chamber in the immediately preceding step is filled in the processing chamber. A gas elimination step for elimination from the gas phase may be performed. According to this, since the gas removing step is performed between the oxidizing agent attaching step and the reaction step, the oxidizing gas or the raw material gas staying in the gas phase in the processing vessel can be removed almost certainly. Therefore, it is possible to perform the film formation mainly based on the surface reaction while almost certainly suppressing the occurrence of the gas phase reaction.

In this case, as defined in claim 3, the gas removing step includes a vacuum evacuation operation for evacuation of the inside of the processing container while stopping the supply of gas into the processing container. And an inert gas purge operation for exhausting a gas while introducing an inert gas into the processing container. Also, for example, the oxidizing agent adhering step and the reaction step may be performed under substantially the same pressure. According to this, since it is not necessary to raise and lower the pressure in the processing container, it is possible to improve the throughput of the film forming process.

Similarly, for example, the oxidizing agent adhering step, the gas removing step, and the reaction step may be performed under substantially the same pressure. Also in this case, since it is not necessary to raise or lower the pressure in the processing container, it is possible to further improve the throughput of the film forming process. Further, as defined in claim 6, the reaction step is performed in a temperature range in which the source gas reacts mainly by a surface reaction.

[0015] For example, the temperature range is in a range of 150 to 400 ° C. Further, for example, as defined in claim 8, the oxidizing gas is H
It is any one of ₂ O, H ₂ O ₂ and O ₃ .

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a film forming method according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing a film forming apparatus for carrying out the method of the present invention, FIG. 2 is a time chart showing a flow of a first embodiment of the method of the present invention, and FIG. 3 is a schematic diagram showing a film forming state in the method of the present invention. is there. As shown in FIG. 1, the film forming apparatus 18 has a processing vessel 20 made of quartz having a cylindrical shape with a ceiling.
Is opened at its lower end to form an opening 22. A flange 24 for joining is provided on the outer periphery. The processing vessel 20 is covered with a cylindrical heat insulating material 28 having a heater 26 disposed therein as a heating means inside, and forms a heating furnace.

On the lower side wall of the processing vessel 20, a source gas introduction nozzle (source gas supply means) 30 for introducing a source gas and an oxidant introduction nozzle (oxidant supply means) for introducing an oxidant gas are provided. 32 and N ₂ gas introduction nozzle 3
The nozzles 30, 32, and 34 extend to the ceiling along the side wall of the processing container 20, and eject each gas from the ceiling while controlling the flow rate of each gas. It is supposed to. In the first embodiment of the method of the present invention, P is used as a source gas (film forming gas).
ET (pentaethoxy tantalum: Ta (OC ₂ H ₅ )
₅ ), and H ₂ O (water vapor) is used as the oxidizing agent. Here, since the PET is a liquid at room temperature, it is vaporized by a vaporizer (not shown) and is processed in a gaseous state.
Introduce inside. Further, a relatively large-diameter exhaust port 36 for exhausting the atmosphere in the processing container 20 is formed in a lower side wall of the processing container 20, and the exhaust port 36 is provided with an exhaust pump in the drawing. Not exhaust system is connected.

The outermost periphery of the flange portion 24 of the processing vessel 20 is supported by, for example, a stainless steel base plate 38 and holds the entire processing vessel 20. The opening 22 at the lower end of the processing container 20 is made of a quartz or stainless steel cap portion 42 which can be moved up and down by an elevating mechanism 40 such as a boat elevator.
Can be opened and closed. A wafer boat 44 is mounted on the cap portion 42 via a heat retaining tube 46 as a quartz object supporting means in which semiconductor wafers W are mounted in multiple stages at a predetermined pitch. With this, it is possible to load or unload the processing container 20.

Next, a first embodiment of the method of the present invention which is performed by using the film forming apparatus configured as described above will be described with reference to FIG.
This will be described with reference to FIG. First, in an unloaded state in which the elevating mechanism 40 is lowered, unprocessed semiconductor wafers W are mounted on the wafer boat 44 in multiple stages, and
Is raised. Incidentally, these semiconductor wafers W include:
In the previous step, the interface film 6 as shown in FIG. 9 is formed. By the ascending drive, the cap portion 42 is gradually raised, and the wafer boat 44 in which a large number of wafers, for example, about 50 to 100 8-inch wafers, are loaded into the processing container 20 through the lower end opening 22 and loaded. Then, finally, the opening 22 is closed by the cap portion 42 to seal the inside of the processing container 20 (point P1 in FIG. 2).

Then, while maintaining the semiconductor wafer W at about 300 ° C., the processing chamber 20 is evacuated to a predetermined pressure,
For example, it is maintained at about 40 Pa (0.3 Torr) (point P2). As described above, when the inside of the processing container 20 is evacuated to a predetermined pressure, the process proceeds to the oxidizing agent attaching step. Here, first, a predetermined amount, for example, 10
Water vapor of about 0 sccm is supplied from the oxidizing agent introduction nozzle 32, and the process temperature of 300 ° C. and the process pressure of 40 Pa are maintained. The water vapor is generated, for example, by burning H ₂ gas with O ₂ gas in a combustion chamber (not shown). By the supply of the steam, FIG.
As shown in (A), very fine water vapor molecules 48 adhere almost uniformly to the surface of the interface film 6 of each semiconductor wafer W (point P3). In this manner, the oxidizing agent attaching step of attaching the water vapor at the molecular level is performed, for example, by one step up to the point P3.
This is performed for about a minute, preferably about 0.1 to 600 seconds. At this time, the supply amount of steam is about 10 cc to 1000 cc (gas).

As described above, when the oxidizing agent attaching step is completed (point P3), the supply of steam is stopped, and then the process proceeds to the reaction step. In this reaction step, a predetermined amount of a PET gas is supplied to a point P4 using, for example, N ₂ gas as an inert gas as a carrier gas. This supply amount is 0.01c
It is about c to 3 cc (liquid). At this time, since the water vapor molecules 48 are attached to the surface of the wafer W as described above, the supplied PET gas comes into contact with the water vapor molecules 48 and is activated even at a low temperature of about 300 ° C., so that the reaction is easy. Then, as shown in FIG. 3B, a first layer of a tantalum oxide film (Ta ₂ O) having a thickness of about one molecule level (about 1 °) is formed.
₅ ) 50A is formed. The reaction formula at this time is represented as follows, and alcohol (C ₂ H ₅ OH) is generated by the reaction. 2Ta (OC ₂ H ₅ ) ₅ + 5H ₂ O → Ta ₂ O ₅ +
10C ₂ H ₅ OH ↑

The process conditions at this time are as follows: the flow rate of N ₂ gas as a carrier gas is about 1000 sccm;
The process pressure is about 40 Pa, which is the same as in the immediately preceding oxidant adhering step. Further, the process temperature is specifically set within a temperature range in which PET as a raw material gas reacts mainly by a surface reaction, for example, within a range of 150 to 400 ° C. Here, as described above, the oxidizing agent immediately before is used. Same as the adhesion process 300
Set to ° C. If the process temperature is higher than 400 ° C., it is not preferable because a CVD film mainly composed of a gas phase reaction instead of a surface reaction occurs to deteriorate the surface roughness as described later. When the process temperature is 1
If the temperature is lower than 50 ° C., the vaporized PET is reliquefied immediately after being introduced into the processing container 20, and the vaporized state cannot be maintained, and the reaction cannot be sufficiently promoted. Also. The preferred temperature range is 200-
It is in the range of 400 ° C.

Further, by setting the process temperature and the process pressure of the oxidizing agent deposition step and the reaction step to the same value as described above, the operation of raising and lowering the process temperature and the operation of raising and lowering the process pressure are performed when the process is shifted. Since there is no need, the throughput can be improved accordingly. By carrying out this reaction treatment, for example, for about 2 minutes, preferably for about 10 seconds to 60 seconds, the water vapor molecules 48 are substantially consumed and a tantalum oxide film 50A having a thickness of about 1 ° is formed. Thus, once the reaction process is completed, P
The supply of the ET is stopped (point P4), and then the oxidizing agent attaching step (point P2-point P3) and the reaction step (point P3-point P4) as described above are again performed in this order from point P4 to point P9. 3 (C) and FIG.
(D)) The second and subsequent layers of the tantalum oxide film 50B are deposited.

The repetition of the oxidizing agent deposition step and the reaction step is repeated n times, for example, several to several tens of times, depending on the target final film thickness, as shown in FIG. Thus, a tantalum oxide film laminated as a whole is obtained. FIG.
(E) shows a state in which the above series of steps is repeated five times to obtain five layers of tantalum oxide films 50A to 50E. In this way, a target film thickness is obtained in total of the film thicknesses of all the tantalum oxide films. In this way, when the reaction step of the last cycle is completed (point P9), the temperature of the wafer W is lowered to a predetermined handling temperature (point P10), and the wafer W is unloaded and unloaded from the processing chamber 20. Will be. As described above, the process temperature is maintained at 400 ° C. or lower, and the oxidizing agent attaching step and the reaction step are repeated a plurality of times in this order. Since the films are stacked, the tantalum oxide film as a whole can maintain high in-plane uniformity of the film thickness without unevenness in thickness, and furthermore, a very thin tantalum oxide film of about several to 100 mm is used. It is possible to obtain a tantalum oxide film having a very small surface roughness and good electric characteristics without causing any irregularities on the surface with good controllability.

Further, the flow rates, process temperatures, process pressures, and the like of the respective gases in the first embodiment are merely examples, and are not limited thereto. For example, regarding the process pressure, in the oxidizing agent attaching step and the reaction step, both are 1.3 Pa (0.01 Torr) to 6 Pa.
It can be performed within a range of about 65 Pa (5 Torr). In the first embodiment, steam (H ₂ O) is used as the oxidizing gas in the oxidizing agent adhering step. However, the present invention is not limited to this, and hydrogen peroxide (H ₂ O ₂ ) and ozone (O ₂ ) may be used. ₃ ) may be used. In the first embodiment, when the oxidizing agent attaching step and the reaction step are repeatedly performed, they are respectively performed continuously. The introduced oxidizing gas or PET gas is supplied to the processing vessel 20.
A gas elimination step for elimination from the inside gas phase may be performed.

FIG. 4 is a time chart showing the flow of the second embodiment of the method of the present invention. As is clear from a comparison between FIG. 2 and FIG. 4, in the second embodiment shown in FIG. 4, between the oxidizing agent attaching step and the reacting step shown in FIG. In between, a gas elimination step is performed. In FIG. 4, this gas elimination process is performed between points P13 and P14, points P15 and P16, points P17 and P18, and points P20 and P21. In this case, the evacuation performed at the point P11-point P12 at the start of the film forming process can also be regarded as the gas removing step. In this gas removing step, the oxidizing gas or PET gas introduced into the processing container 20 in the immediately preceding step (excluding the case of the points P11 to P12) is removed from the gas phase. P13-
In the gas exclusion step shown between the points P14, in the oxidizing agent attaching step (points P12-P13) immediately before this, the processing container 20
The gas elimination step shown between the points P15 and P16 is a reaction step (point P14-point P1) immediately before this.
In step 5), the PET gas introduced into the processing container 20 and remaining in the gas phase is removed.

A specific operation in this gas elimination step is as follows. In a state where supply of all gases to the processing vessel 20 is stopped, the inside of the processing vessel 20 is evacuated to a base pressure, for example, 0.4 Pa (0 Pa). .003 Torr) by evacuation to remove PET gas and water vapor by reducing the pressure to 0.003 Torr, and introducing an inert gas such as N ₂ gas into the processing vessel 20 while evacuating the processing vessel 20. This makes it possible to selectively perform a gas exhaust inert gas purge operation for eliminating PET gas and water vapor. In this case, the gas removing step may be performed, for example, for about 1 to 2 minutes. As described above, by performing the gas removing step, the PET gas or water vapor introduced into the processing container 20 in the immediately preceding step and remaining in the gas phase is removed. When water vapor or PET gas is introduced into the processing vessel 20, no gas contributing to the film formation reaction remains in the gas phase, so that a gas phase reaction that causes deterioration in surface roughness does not occur, and In addition, it becomes possible to suppress the surface roughness of the finally obtained tantalum oxide film very small.

Here, in the case where an inert gas purging operation for gas exhaustion is performed as a gas elimination step, the pressure in the processing vessel 20 at this time is changed to the pressure during the oxidizing agent deposition step and the reaction step before and after this step. If the pressure is maintained at the same value, for example, 40 Pa, the same pressure value will be obtained throughout the entire process, so that it is not necessary to adjust the pressure for each process, and accordingly,
The processing speed is increased, and the throughput can be improved. In the second embodiment shown in FIG. 4 described above, in the gas elimination step, either one of the vacuum evacuation operation for gas exhaust and the inert gas purging operation for gas exhaust is selectively performed. However, the present invention is not limited thereto, and these two operations may be performed continuously.

FIG. 5 is a time chart showing the flow of the third embodiment of the method of the present invention. As is apparent from a comparison between FIG. 4 and FIG. 5, in the third embodiment shown in FIG. 5, in the gas elimination step shown in FIG. Performs an inert gas purge operation for gas exhaust while also having a function of pressure recovery (adjustment). In FIG. 5, the evacuation operation for gas exhaust is performed at points P11-P11-1, P13-
The processing is performed between point P13-1, point P15-point P15-1, point P17-point P17-1, and point P20-point P20-1. In addition, the inert gas purge operation for gas exhaust is performed at the point P
11-1-point P12, point P13-1-point P14, point P1
5-1-point P16, point P17-1-point P18, and point P2
It is performed between 0-1 and point P21. Here, each operation of the evacuation operation for gas exhaustion and the inert gas purge operation for gas exhaustion may be performed for, for example, about one minute. As described above, in the gas elimination step, if the evacuation operation for gas exhaustion and the inert gas purge operation for gas exhaustion are continuously performed, the gas phase in the processing container 20 contributes to the film formation reaction. Since the gas is almost completely absent,
It is possible to further reduce the surface roughness of the finally obtained tantalum oxide film.

Next, MLD film formation according to the method of the present invention and conventional C
The evaluation of the surface roughness of the tantalum oxide film obtained by VD film formation (including the method disclosed in the above-mentioned Japanese Patent Application No. 2000-80904) and the evaluation of the carbon concentration in the film were performed. explain. FIG. 6 shows the case where the CVD film formation was performed at a temperature of 410 ° C. (including the method disclosed in Japanese Patent Application No. 2000-80904), and the MLD film formation of the present invention was performed at a temperature of 200 ° C. and 300 ° C., respectively. 4 is a graph showing the surface roughness of each film at the time. In addition, all the formed film thicknesses are substantially the same. In the graph shown in FIG. 6, the results A and B show the results when the film was formed by the method of the third embodiment of the present invention shown in FIG. 5, respectively.
When B is repeated 100 times while maintaining the overall process temperature at 200 ° C., the result B is that the overall process temperature is 300 ° C.
Are repeated 50 times while maintaining the same. In addition, the result C is based on the prior application (Japanese Patent Application No. 2000-8090).
This shows a case where a film is formed by the method disclosed in 4), and the process temperature is 410 ° C. Further, result D shows a case where a film is formed by a conventional general CVD, and the process temperature is 410 ° C.

As is clear from this graph, the results A and B of the method of the present invention show 1.2 ° and 1.5 °, respectively, with respect to the surface roughness.
The surface roughness was considerably smaller than 4.5 ° of the result D by the film formation and 2 ° of the result C by the method of the prior application, and it was found that good results could be obtained. In the method of the present invention, the growth rate of the film thickness when the process temperature is 200 ° C. is about 0.5 ° per time,
In the case of ° C, it was about 1.0 °. FIG. 7 is a graph showing the carbon concentration in each of the films when the CVD film was formed at a temperature of 410 ° C. and when the MLD film of the present invention was formed. In the graph shown in FIG. 7, a characteristic A shows a result (process temperature is 300 ° C.) when a film is formed by the method of the third embodiment of the present invention shown in FIG. C
Result when performing VD film formation (process temperature is 410 ° C)
Is shown.

As is clear from this graph, at least the thickness 50 which is expected to be used in the future use of the tantalum oxide film.
Up to Å, it was found that the carbon concentration of the property A of the present invention was sufficiently smaller than that of the property B, and thus the electrical properties of the film according to the method of the present invention were considerably better. . Note that, in each of the above-described embodiments, in the reaction process, the N ₂ gas is used as the carrier gas together with the PET gas, but another inert gas, for example, He, Ne, or Ar gas may be used. Further, the source gas is not limited to PET gas, and another source gas containing tantalum may be used.

In each of the above embodiments, the case where a tantalum oxide film is deposited on the surface of the semiconductor wafer has been described as an example. However, as another example, specifically, as shown in FIG. The method of the present invention can be applied to the case where a tantalum oxide film 8 is deposited as a capacitor insulating film of the capacitor of FIG. That is, as shown in FIG. 8A, the lower electrode 3 made of, for example, ruthenium formed on the interlayer insulating film 5 made of SiO ₂ or the like, as shown in FIG.
When forming the tantalum oxide film 8 as a capacitor insulating film as shown in FIG. 3B, the method of the present invention is used under the same process conditions as described above, such as temperature and pressure. This allows
The incubation time is eliminated, so that not only can the tantalum oxide film 8 of the same thickness be deposited on the lower electrode 3 and the interlayer insulating film 5, but also the tantalum has good electrical characteristics and very small surface roughness. An oxide film can be obtained. Therefore, as shown in FIG. 8C, even if the upper electrode 11 is deposited on this upper layer and a voltage is applied between the two electrodes 3 and 11, unlike the case described above with reference to FIG. Since 9 (see FIG. 12) has not occurred,
The electrical characteristics can be maintained high. still,
This capacitor has an MIM structure, but is not limited to this. For example, a MIS (Metal Insulator)
The present invention can also be applied to a capacitor having a semiconductor (Semiconductor) structure.

Here, a single tube structure can be used to process a large number of semiconductor wafers at once.
Although a batch type film forming apparatus has been described as an example, the present invention is not limited to this, and is also applicable to a batch type film forming apparatus having a double pipe structure and a so-called single wafer type film forming apparatus which processes semiconductor wafers one by one. Of course, the present invention can be applied. Further, the object to be processed is not limited to a semiconductor wafer, and it goes without saying that the present invention can be applied to an LCD substrate, a glass substrate, and the like.

[0035]

As described above, according to the film forming method of the present invention, the following excellent functions and effects can be exhibited. According to the inventions defined in claims 1, 3, 5, 6, 7, and 8, a gas phase reaction is suppressed to cause a reaction mainly based on a surface reaction, and an extremely thin film at a molecular level is formed into a plurality of layers one by one. Since the entire tantalum oxide film is deposited by forming over the entire surface, the in-plane uniformity of the film thickness is very high, the surface roughness is very small, and the electric characteristics are good. A tantalum oxide film can be accurately formed. According to the invention defined in claim 2, since the gas removing step is performed between the oxidizing agent attaching step and the reaction step, the oxidizing gas or the raw material gas staying in the gas phase in the processing vessel Can be almost certainly eliminated, and therefore, the formation of a gas phase reaction can be almost certainly suppressed, and a film can be formed mainly by a surface reaction. According to the invention defined in claim 4, since it is not necessary to raise or lower the pressure in the processing container, it is possible to improve the throughput of the film forming process.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a film forming apparatus that performs a method of the present invention.

FIG. 2 is a time chart showing a flow of the first embodiment of the method of the present invention.

FIG. 3 is a schematic diagram showing a film formation state in the method of the present invention.

FIG. 4 is a time chart showing a flow of a second embodiment of the method of the present invention.

FIG. 5 is a time chart showing a flow of a third embodiment of the method of the present invention.

FIG. 6 is a graph showing the surface roughness of each film when a CVD film is formed at a temperature of 410 ° C. and when the MLD film of the present invention is formed at a temperature of 200 ° C. and 300 ° C., respectively. .

FIG. 7 is a graph showing the carbon concentration in each film when a CVD film is formed at a temperature of 410 ° C. and when an MLD film is formed according to the present invention.

FIG. 8 is a diagram illustrating a case where a tantalum oxide film is deposited as a capacitor insulating film of a capacitor having an MIM structure.

FIG. 9 is a cross-sectional view showing an example of a capacitor structure when a tantalum oxide film is used as a gate insulating film or the like.

FIG. 10 is a graph showing a relationship between a deposition rate of a tantalum oxide film and an incubation time.

FIG. 11 is a schematic diagram showing a film formation state during an incubation time.

FIG. 12: MIM (Metal Insulator)
FIG. 3 is a diagram for describing an insulating film of a capacitor having a (Metal) structure.

[Explanation of symbols]

 2 Source 4 Drain 8 Tantalum oxide film 10 TiN film 12 Gate electrode 20 Processing vessel 26 Heater (heating means) 30 Source gas introduction nozzle (source gas supply means) 32 Oxidant introduction nozzle (oxidant supply means) 34 Oxygen introduction nozzle 44 wafer boat 48 steam gas 50A-50D tantalum oxide film W semiconductor wafer (object to be processed)

Continuing from the front page (72) Inventor Yoshitaka Tsunashima 8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Inside the Toshiba Yokohama Office (72) Inventor Yuichiro Ryuko 650 Mitsuzawa, Hosaka-cho, Nirasaki, Yamanashi Prefecture Tokyo Electron Yamanashi Co., Ltd. (72) Inventor Choi Dong-yun 650 Mitsuzawa, Hosaka-cho, Nirasaki-shi, Yamanashi Prefecture Inside Tokyo Electron Yamanashi Co., Ltd. (72) Inventor Kazuhide Hasebe 650 Mitsuzawa, Hosaka-cho, Nirasaki-shi, Yamanashi Prefecture Tokyo Electron Yamanashi F-term ( 4K030 AA11 AA14 AA18 BA42 CA04 EA01 FA10 JA10 LA15 5F045 AA03 AA15 AB31 AC07 AD06 AD07 AE19 BB02 BB16 DC61 DP19 EE02 EE14 EE18 EE19 EF02 EG05 EK06 EM10 EN05 5F058 BC03 BD05 BF29 BF29 BF29 BF29 BF29 BF29

Claims (8)

[Claims] 1. A film forming method for forming a tantalum oxide film on a surface of an object in a processing vessel using a source gas and an oxidizing gas, wherein the oxidizing gas is attached to the surface of the object. And a reaction step of forming a tantalum oxide film by causing the source gas to act on the attached oxidant gas in this order. Membrane method. 2. A method for removing an oxidizing gas or a raw material gas introduced into the processing vessel in the immediately preceding step from the gas phase in the processing vessel between the oxidizing agent attaching step and the reaction step. 2. The film forming method according to claim 1, wherein a gas removing step is performed. 3. The method according to claim 2, wherein the gas removing step includes a gas exhaust vacuum operation for evacuating the inside of the processing container while stopping the supply of gas into the processing container, and / or an inert gas into the processing container. 3. The film forming method according to claim 2, further comprising an inert gas purging operation for exhausting a gas while introducing a vacuum. 4. The film forming method according to claim 1, wherein the oxidizing agent attaching step and the reacting step are performed under substantially the same pressure. 5. The film forming method according to claim 2, wherein the oxidizing agent attaching step, the gas removing step, and the reaction step are performed under substantially the same pressure. 6. The film forming method according to claim 1, wherein the reaction step is performed in a temperature range in which the source gas reacts mainly by a surface reaction. . 7. The film forming method according to claim 6, wherein the temperature range is in a range of 150 to 400 ° C. 8. The oxidizing gas is H ₂ O, H ₂ O ₂ ,
The film forming method according to claim 1, wherein the film is one of O ₃ .