JP2004244661A - Method of producing thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suitably realize an objective film thickness with minimized period of time in the method of producing a thin film using an atomic layer growth method. <P>SOLUTION: In the method of producing a thin film where AlCl3 and H2O as source materials are alternatingly fed to a substrate to deposit an Al2O3 thin film, the feeding time of AlC13 in the first cycle in the feeding cycles is made longer than the feeding time of AlC13 in the cycles on and after the second time. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a method for manufacturing a thin film in which a thin film is formed by alternately supplying a first raw material containing a metal element and a second raw material containing an element that reacts with a metal element to a substrate, a so-called thin film manufacturing method. The present invention relates to an atomic layer growth method.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an atomic layer epitaxy (ALE) method has been used when forming a thin film of a metal oxide or a metal sulfide, and has been used as a film forming method having good crystallinity and excellent film thickness controllability. (For example, see Patent Document 1).
[0003]
In this method, a first raw material containing a metal element (for example, a metal chloride or an organometallic compound) and a second raw material containing an element that reacts with the metal element (for example, an oxidized substance such as water, hydrogen sulfide, or the like) are used. ) Is simply repeated on the substrate by alternately supplying the reaction compound to the substrate, whereby the reaction compound is disposed on the substrate surface one layer at a time by the reaction on the substrate surface. It is said that the film thickness can be easily controlled.
[0004]
Various thin films can be formed using this ALE method. For example, in an electroluminescence element, there are an ATO thin film which is a composite film of aluminum oxide and titanium oxide used as an insulating layer, and zinc sulfide and strontium sulfide used as a light emitting layer.
[0005]
[Patent Document 1]
JP-A-55-130896
[Problems to be solved by the invention]
However, although the ALE method has the above advantages, it is a formation method in which atoms are arranged one by one. Therefore, if the supply time of each raw material constituting the thin film is lengthened, a large amount of ALE method is required to obtain a desired film thickness. It takes a long time.
[0007]
On the other hand, according to the study of the present inventors, for example, when forming an ATO thin film by the ALE method, when alternately laminating an Al2O3 thin film and a TiO2 thin film, when forming a TiO2 thin film on an Al2O3 thin film, If an attempt is made to reduce the film formation time when forming an Al2O3 thin film thereon, there arises a problem that the film thickness formed by the number of times of supply of the raw material calculated from the film thickness of the monomolecular layer becomes different from the target film thickness and becomes thin. Was.
[0008]
In view of the above problems, the present invention forms a thin film by alternately supplying a first raw material containing a metal element and a second raw material containing an element that reacts with a metal element to a substrate. In a method of manufacturing a thin film, it is an object to appropriately realize a target film thickness with a formation time as short as possible.
[0009]
[Means for Solving the Problems]
The present inventor has further studied the above-described problem that the thickness of the ATO thin film becomes smaller than a target film thickness.
[0010]
For example, when an Al2O3 thin film is formed on a TiO2 thin film, usually, AlCl3 which is a raw material of Al is supplied, and H2O is supplied to oxidize the Al2O3 molecule to form Al2O3 molecules.
[0011]
At this time, if the supply time of the AlCl3 raw material, that is, the supply amount of the AlCl3 raw material at one time, is small for the purpose of shortening the entire thin film formation time, the alignment of the crystals on the different kind of film (that is, the TiO2 thin film) which is the base is made. Due to worse sex, they cannot grow well. As a result, it is not possible to sufficiently cover the surface of the underlayer with AlCl3 by a single supply of the raw material.
[0012]
When the supply cycle of AlCl3 and H2O is repeated in this state, and the film growth is continued, a portion where the growth is partially fast occurs, and Al2O3 grows in a cluster. As a result, it has been found through experiments that the completed Al2O3 thin film has an uneven thickness, and a desired film thickness cannot be obtained with good control.
[0013]
Conversely, if the supply cycle of the AlCl3 raw material is set to a sufficient amount once and the supply cycle is repeated, the deposition time for obtaining a desired film thickness becomes enormous.
[0014]
Furthermore, in the case of forming an Al2O3 thin film on a TiO2 thin film, if AlCl3, which is a raw material of Al, is supplied first, the molecules on the surface of the TiO2 as a base and the AlCl3 molecules undergo a substitution reaction, so that TiO2 is eroded. discovered. This is considered to be possible when the vapor pressure is relatively higher in the base film than in the thin film material.
[0015]
Therefore, when the AlCl3 raw material is supplied non-uniformly, the substitution reaction with TiO2 is performed non-uniformly, and in combination with the above-mentioned poor growth due to the poor matching of the crystal with the underlayer, the portion where the thin film growth rate is different. Was generated, resulting in a non-uniform film thickness.
[0016]
From the results of these studies, it is possible to achieve uniform film growth in the subsequent supply if the poor alignment of the crystal with the base and the non-uniform reaction between the base and the thin film raw material are eliminated in the initial stage of the supply cycle. I thought it might be. The present invention has been obtained as a result of an experimental study focusing on such points.
[0017]
That is, according to the first aspect of the invention, a thin film is formed by alternately supplying a first raw material containing a metal element and a second raw material containing an element that reacts with a metal element to a substrate. In the thin film manufacturing method described above, the supply time of the first raw material in the first cycle of the supply cycle is longer than the supply time of the first raw material in the second and subsequent cycles.
[0018]
According to this, by sufficiently increasing the supply time of the first raw material in the first cycle of the supply cycle, the base can be sufficiently covered with the first raw material containing the metal element.
[0019]
Therefore, even if the consistency between the crystal of the thin film to be formed and the underlying film is poor or the reaction between the underlying film and the thin film raw material is likely to occur, the crystal of the underlying film and the underlying film are not reconstituted after the second supply cycle. Consistency is improved, and no reaction with the underlayer occurs, so that uniform layer growth is possible.
[0020]
The supply time of the first raw material in the first cycle of the supply cycle is longer, but is shorter than that in the second and subsequent supply cycles, and can be almost the normal supply time. That's not a long time.
[0021]
Therefore, according to the present invention, a target film thickness can be appropriately realized with a formation time as short as possible.
[0022]
Here, as in the invention according to claim 2, a metal halide or an organometallic compound can be used as the first raw material.
[0023]
As the thin film, an insulator such as alumina (Al2O3) or the like, or a semiconductor such as titania (TiO2) can be used.
[0024]
It should be noted that reference numerals in parentheses of the above-described units are examples showing the correspondence with specific units described in the embodiments described later.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on specific embodiments. In this embodiment, the thin film to be formed is an ATO thin film used as an insulating film of an EL element. This is a film formed by alternately stacking a large number of Al2O3 (alumina) thin films as insulators and TiO2 (titania) thin films as semiconductors by the ALE method.
[0026]
In the ATO thin film as the insulating film of the EL element, the TiO2 thin film and the Al2O3 thin film are alternately laminated in order from the Al2O3 thin film by the ALE method, and finally, the Al2O3 thin film is formed again.
[0027]
Specifically, when an Al2O3 thin film is formed by an ALE method, AlCl3, which is a first raw material containing a metal element, and H2O, which is a second raw material containing an element that reacts with a metal element, By repeating a cycle of alternately supplying Al2O3 to the substrate, Al2O3 is grown one atomic layer at a time, and an Al2O3 thin film having a predetermined thickness is formed.
[0028]
When the TiO2 thin film is formed by the ALE method, TiCl4, which is a first raw material containing a metal element, and H2O, which is a second raw material containing an element that reacts with a metal element, are added to the substrate. By repeating the alternate supply cycle, TiO2 is grown one atomic layer at a time to form a TiO2 thin film having a predetermined thickness.
[0029]
Then, the Al2O3 thin film and the TiO2 thin film each having a predetermined film thickness are alternately laminated to form an ATO thin film.
[0030]
Here, the thickness of the Al2O3 thin film excluding the uppermost Al2O3 thin film and the lowermost Al2O3 thin film of the ATO thin film is 5 nm, and the thickness of the TiO2 thin film may be in the range of 1.5 to 5 nm. And The thickness of the uppermost and lowermost Al2O3 thin films may be in the range of 15 to 30 nm, and in this example, was 20 nm.
[0031]
Next, a specific manufacturing method of the ATO thin film will be described. Here, in the method of forming the Al2O3 thin film among the ATO thin films, the supply time of AlCl3 in the first cycle of the supply cycle is set to be longer than the supply time of AlCl3 in the second and subsequent cycles. An example in which a thin film is formed by a normal ALE method will be described.
[0032]
First, a substrate is set in a substrate holder box for fixing the substrate. At this time, in this example, the surface on which the thin film is formed on the substrate is set upright. Then, the substrate holder box on which the substrate is set is put into a load lock chamber that can be evacuated.
[0033]
Next, the load lock chamber is evacuated to 10 ⁻³ Torr or less, and nitrogen as a carrier gas for transporting the raw material is introduced. This operation is repeated, and evacuation is performed so that the load lock chamber finally becomes 10 ⁻³ Torr or less.
[0034]
Then, the substrate holder box which has been sufficiently purged with nitrogen in the load lock chamber and evacuated is moved to a deposition chamber for forming a thin film which has been previously substituted with nitrogen and evacuated.
[0035]
Then, the substrate holder box is heated by a heater installed in the film formation chamber, and the substrate temperature is set to 500 ° C., which is the temperature at the time of film formation. However, during this heating, nitrogen as a carrier gas is introduced into the substrate holder box in the same amount as during the film formation in order to prevent a temperature drop due to the supply gas at the start of the film formation.
[0036]
After the substrate temperature reaches 500 ° C. and the temperature is stabilized, first, of the following processes, first, the second process is performed, and then the third, fourth, and fifth processes are performed. The ATO thin film (laminated composite film of the Al2O3 thin film and the TiO2 thin film) is formed by repeating the process six times and finally performing the sixth process. Note that in each process, the number in parentheses indicates the supply time.
[0037]
"First process": supply of a nitrogen gas containing an AlCl3 gas (first raw material) as a source gas (9 seconds) and supply of a purge gas with a nitrogen gas for pushing out the AlCl3 gas remaining in the pipe ( 1 second), supply of nitrogen gas containing H2O (second raw material) as a source gas (2 seconds), and supply of pipe purge gas with nitrogen gas for pushing out H2O remaining in the pipe (1.5 seconds) Is performed once.
[0038]
"Second process": supply of nitrogen gas containing AlCl3 gas as a raw material gas (0.5 seconds), supply of pipe purge gas with nitrogen gas for pushing out AlCl3 gas remaining in the pipe (1 second), raw material A cycle of supplying a nitrogen gas containing H2O as a gas (0.8 seconds) and supplying a purge gas with a nitrogen gas for pushing out H2O remaining in the pipe (1.5 seconds) is repeated 333 times.
[0039]
"Third process": supply of nitrogen gas containing AlCl3 gas as a raw material gas (0.5 seconds), supply of pipe purge gas with nitrogen gas for pushing out AlCl3 gas remaining in the pipe (1 second), raw material A cycle of supplying nitrogen gas containing H2O as a gas (0.8 seconds) and supplying a purge gas with nitrogen gas for pushing out H2O remaining in the pipe (1.5 seconds) is repeated 111 times.
[0040]
"Fourth process": supply of nitrogen gas containing TiCl4 gas as a raw material gas (0.6 seconds), supply of pipe purge gas with nitrogen gas for pushing out TiCl4 gas remaining in the pipe (1 second), raw material A cycle of supplying a nitrogen gas containing H2O as a gas (0.8 seconds) and supplying a pipe purge gas with a nitrogen gas for extruding H2O remaining in the pipe (2 seconds) is repeated 51 times.
[0041]
“Fifth process”: supply of nitrogen gas containing AlCl 3 gas as a source gas (9 seconds), supply of pipe purge gas with nitrogen gas for pushing out AlCl 3 gas remaining in the pipe (1 second), A cycle of supplying a nitrogen gas containing a certain amount of H2O (2 seconds) and supplying a purge gas with a nitrogen gas for pushing out H2O remaining in the piping (1.5 seconds) is performed once.
[0042]
"Sixth process": supply of nitrogen gas containing AlCl3 gas as a raw material gas (0.5 seconds), supply of pipe purge gas with nitrogen gas to push out AlCl3 gas remaining in the pipe (1 second), raw material A cycle of supplying a nitrogen gas containing H2O as a gas (0.8 seconds) and supplying a pipe purge gas with a nitrogen gas for pushing out H2O remaining in the pipe (1.5 seconds) is repeated 444 times.
[0043]
Here, by performing the first, second, and third processes once, an Al2O3 thin film (thickness: 20 nm) at the bottom of the ATO thin film is formed. Next, the fourth process is performed once to form a TiO2 thin film (2 nm thick) thereon.
[0044]
Next, the fifth process and the third process are performed once in this order, whereby an Al2O3 thin film (5 nm thick) is formed thereon. Next, a fourth process is performed once to form a TiO2 thin film (thickness: 2 nm) thereon, and then a fifth process and a third process are performed once in this order to perform a fourth process. An Al2O3 thin film (5 nm thick) is formed.
[0045]
In the present example, the third, fourth, and fifth processes are repeated 28 times. After the formation of the last TiO2 thin film, that is, the last fourth process, the fifth process and the sixth process are performed once in this order, thereby forming the uppermost Al2O3 thin film (thickness: 20 nm). Thus, the ATO thin film of this example is completed.
[0046]
Here, the raw material gas and the purge gas are each evenly distributed from above the substrate by a gas distributor installed above the substrate holder box. The distributed source gas and purge gas flow from the upper part to the lower part of the substrate on which the film formation surface is arranged vertically. That is, the gas flows along the film formation surface.
[0047]
The supply amounts of the raw materials AlCl3 and TiCl4 are respectively 7.2 × 10 ^{−6 to} 9.8 × 10 ⁻⁵ mol / pulse and 6.0 × 10 ^{−6 to} 2.4 × 10 ⁻⁴ mol / pulse. Each raw material was supplied to the substrate within a range of pulse (all calculated values).
[0048]
In the above-mentioned manufacturing method, regarding the formation of the Al2O3 thin film, the fact that the supply time of AlCl3 in the first cycle of the supply cycle is longer than the supply time of AlCl3 in the second and subsequent cycles is specifically as follows. It is like that.
[0049]
First, the lowermost Al2O3 thin film (thickness: 20 nm) is formed by performing the first, second, and third processes once, and the first to third processes are performed once. This means that the alternate supply cycle of AlCl3 and H2O is repeated (1 + 333 + 111) times, that is, 445 times.
[0050]
Here, the first supply cycle is the first process, and the supply time of AlCl3 is 9 seconds, which is longer than 0.5 second, which is the supply time of AlCl3 in the second and subsequent cycles. ing.
[0051]
In addition, in response to the increase in the supply time of AlCl3 in the first cycle, the supply time of H2O (2 seconds) in the first cycle is also increased (0.8 second) in the second and subsequent cycles. Longer than it is.
[0052]
The intermediate Al2O3 thin film (thickness: 5 nm) is formed by sequentially performing the fifth process and the third process once, and performing the fifth and third processes once. Means that the alternate supply cycle of AlCl3 and H2O is repeated (1 + 111) times, that is, 112 times.
[0053]
Here, the first supply cycle is the fifth process, and the supply time of AlCl3 is 9 seconds, which is longer than 0.5 second, which is the supply time of AlCl3 in the second and subsequent cycles. ing. Also for H2O, the supply time (2 seconds) in the first cycle is longer than the supply time (0.8 seconds) in the second and subsequent cycles.
[0054]
Further, the uppermost Al2O3 thin film is similar to the lowermost and intermediate Al2O3 thin films. As described above, in the present embodiment, in the formation of the Al2O3 thin film, the supply time of AlCl3 in the first cycle of the supply cycle is set longer than the supply time of AlCl3 in the second and subsequent cycles.
[0055]
Here, FIG. 1 shows a supply timing chart of the AlCl3 raw material, the H2O raw material, and the respective purge gas from the initial stage to the third supply cycle in the above-described formation of the Al2O3 thin film of the present example on a coaxial time axis. In FIG. 1, the horizontal axis indicates a time axis, and the vertical axis indicates a pulse waveform indicating material supply.
[0056]
FIG. 2 is a diagram schematically showing a state of film growth in the case where an intermediate Al2O3 thin film (thickness: 5 nm) is formed by the above manufacturing method, as behaviors of Al, O, and Cl on the surface of the thin film. . In this case, the base is a TiO2 thin film, and the films grow in the order of steps 1, 2, 3, and 4 in the initial stage.
[0057]
Further, FIG. 3 is a diagram showing a supply timing chart of each raw material in forming an Al2O3 thin film by the conventional ALE method as a comparative example with respect to FIG. In this case, all the supply cycles of the Al2O3 thin film are performed according to the material supply time shown in the third process.
[0058]
FIG. 4 is a diagram schematically showing, at a molecular level, a growth state of a film when an intermediate Al2O3 thin film (5 nm thick) is formed by a conventional ALE method as a comparative example with respect to FIG. It is.
[0059]
In the conventional manufacturing method shown in FIG. 4, since the supply time of AlCl3 in the first cycle is short and insufficient, as shown in Step 1, AlCl3 molecules are partially arranged (substituted) randomly on the surface of the TiO2 thin film. ) Is done. Therefore, in the subsequent material supply cycle, as shown in the order of steps 2, 3, and 4, the Al2O3 thin film grows in an island shape. Therefore, the film thickness becomes uneven.
[0060]
On the other hand, in the embodiment shown in FIG. 2, when AlCl 3, which is a raw material containing a metal element, is disposed on the TiO2 thin film, the supply time of the AlCl 3 raw material, which is usually 0.5 seconds, is 9 deg. It is a long material supply time of seconds.
[0061]
That is, in contrast to the conventional manufacturing method, the manufacturing method of the Al2O3 thin film of the present embodiment is a unique method in which the first process and the fifth process are included in the first supply cycle.
[0062]
Therefore, as shown in step 1 of FIG. 2, the first supply of AlCl 3 causes the AlCl 3 molecules to be arranged neatly on the surface of the TiO 2 thin film, and in the subsequent repetition cycle of the normal raw material supply time (0.5 seconds), Al and O are arranged neatly. Thus, according to the present embodiment, a uniform film thickness can be obtained according to the number of supply cycles of the raw material.
[0063]
FIG. 5 is a diagram showing the result of examining the relationship between the number of supply times (number of supply cycles) of the raw material (AlCl 3, H 2 O) and the thickness of Al 2 O 3 when an Al 2 O 3 thin film is formed by the above-described manufacturing method of the present embodiment. It is. In addition, FIG. 5 also shows the result of an examination on a case where an Al2O3 thin film is formed by the above-described conventional method.
[0064]
As can be seen from FIG. 5, when the film was formed by the conventional method, the film formation rate at the initial stage of the thin film formation was unstable, and the film formation rate thereafter was also unstable, and a stable film thickness could not be obtained. Was. On the other hand, by using the manufacturing method of the present embodiment, the initial speed of forming the thin film was stabilized, and as a result, there was almost no variation in the film thickness, and a stable film supply became possible.
[0065]
For example, when an Al2O3 thin film having a thickness of 5 nm is formed, in the conventional manufacturing method, a variation in the film thickness distribution of about 1 nm occurs with respect to the target film thickness of 5 nm, but in the manufacturing method of the present embodiment, It was possible to suppress the variation to about 0.3 nm with respect to the target film thickness of 5 nm.
[0066]
That is, in the conventional method, the film formation state at the initial stage of film formation was poor, and the film thickness distribution was poor because the raw material was partially disposed on the surface. On the other hand, when the film is formed by the manufacturing method of the present embodiment, the film thickness can be accurately controlled with respect to the number of times of supply of the raw material, and since the AlCl 3 is uniformly disposed, the film thickness distribution state is also good. Can be something.
[0067]
In the above example, the supply time of the first raw material containing the metal element in the first cycle of the supply cycle is set to the supply time in the second and subsequent cycles, compared to the method of forming the Al2O3 thin film in the ATO thin film. Although the example in which the manufacturing method of making the length longer is applied has been described, it goes without saying that the same method may be applied to the formation of the TiO2 thin film.
[0068]
In this case, the supply time of TiCl4 in the first cycle of the supply cycle may be longer than the supply time of TiCl4 in the second and subsequent cycles. Thereby, the same effect as in the case of the Al2O3 thin film described above was obtained.
[0069]
As described above, according to this embodiment, the first raw material containing the metal element and the second raw material containing the element that reacts with the metal element are alternately supplied to the substrate. In the method of manufacturing a thin film for forming a thin film, the supply time of the first raw material in the first cycle of the supply cycle is longer than the supply time of the first raw material in the second and subsequent cycles. A method for producing a thin film is provided.
[0070]
According to this, by sufficiently increasing the supply time of the first raw material in the first cycle of the supply cycle, the base can be sufficiently covered with the first raw material containing the metal element.
[0071]
Therefore, even if the consistency between the crystal of the thin film to be formed and the underlying film is poor or the reaction between the underlying film and the thin film raw material is likely to occur, the crystal of the underlying film and the underlying film are not reconstituted after the second supply cycle. Consistency is improved, and no reaction with the underlayer occurs, so that uniform layer growth is possible.
[0072]
The supply time of the first raw material in the first cycle of the supply cycle is longer, but is shorter than that in the second and subsequent supply cycles, and can be made almost the normal supply time. The whole is not very long.
[0073]
Therefore, according to the present embodiment, the target film thickness can be appropriately realized while the formation time of the thin film is made as short as possible.
[0074]
In addition, in the second and subsequent supply, the supply time of the first raw material may be shortened as going to a later cycle. For example, the supply time of AlCl3 in the second cycle may be longer than the supply time of AlCl3 in the third and subsequent cycles. However, it is necessary to make the supply time of the first cycle the longest.
[0075]
In addition, the manufacturing method of the present invention includes not only the above-described process of forming an Al2O3 thin film on a TiO2 thin film, but also a process of forming a TiO2 thin film on an Al2O3 thin film, a process of forming an Al2O3 thin film on a glass substrate, and a process such as ZnS. The present invention can be applied to a process of forming an Al2O3 thin film on a light emitting layer, a process of forming an oxide thin film using a halide such as an organic complex or a chloride as a starting material by an ALE method, and the like.
[Brief description of the drawings]
FIG. 1 is a diagram showing a supply timing chart of each raw material in forming an Al2O3 thin film according to an embodiment of the present invention.
FIG. 2 is a diagram schematically showing, at a molecular level, how a film grows when an Al2O3 thin film is formed in the embodiment.
FIG. 3 is a diagram showing a supply timing chart of each raw material in forming an Al2O3 thin film by a conventional manufacturing method.
FIG. 4 is a diagram schematically showing a state of film growth at the molecular level when an Al2O3 thin film is formed in a conventional manufacturing method.
FIG. 5 is a diagram showing the result of examining the relationship between the number of times of supply of a raw material and the film thickness when an Al2O3 thin film is formed by the manufacturing method of the embodiment.

Claims (6)

In a method for producing a thin film, a first raw material containing a metal element and a second raw material containing an element that reacts with the metal element are alternately supplied to a substrate to form a thin film.
A method for producing a thin film, wherein the supply time of the first raw material in the first cycle of the supply cycle is longer than the supply time of the first raw material in the second and subsequent cycles. 2. The method according to claim 1, wherein a metal halide or an organometallic compound is used as the first raw material. The method according to claim 1, wherein the thin film is an insulator. The method according to claim 3, wherein the insulator is alumina. 3. The method according to claim 1, wherein the thin film is a semiconductor. The method according to claim 5, wherein the semiconductor is titania.

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