JP3846004B2 - Membrane production method using gel substance, PZT membrane production method, and PZT membrane - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a film such as a PZT film, which is formed by depositing a gel-like substance such as a hydroxide, a hydrate or a hydrate on a substrate and then performing a heat treatment, and the production thereof. The present invention relates to a PZT film manufactured by the method.
[0002]
[Prior art]
Since PZT (lead zirconate titanate) has a high dielectric constant, it is applied as a dielectric material to electronic components such as capacitors and memories. Further, since PZT has a perovskite structure and piezoelectricity, it can be applied as an actuator element. The above-mentioned electronic components are similarly reduced in size and weight in accordance with miniaturization and weight reduction of electronic devices using the same, and PZT is also used in a film shape from a bulk shape having a certain volume. A lot is happening. Conventionally, as a method for producing a PZT film at low cost, electrolysis is performed in a nitrate bath containing lead, zirconium, and titanium, a PZT precursor is deposited on a substrate, and then heat-treated to be oxidized to obtain a PZT film. An electrolytic deposition method and a sol-gel method have been proposed.
[0003]
[Problems to be solved by the invention]
However, in the electrolytic deposition method, the precursor of PZT deposited on the substrate by electrolysis is mainly a hydrate or hydrate of lead, zirconium, titanium, and is a gel containing water immediately after electrodeposition. When the film is deposited to about 1 μm, there is a problem that the film tends to shrink during drying and cracks easily occur. Further, when the film becomes thicker, the tensile stress due to the contraction of the film exceeds the adhesion force to the substrate, and the film peels off from the substrate.
[0004]
Since the sol-gel method has the same problem, a thin gel film is laminated to obtain a thick film, but if a gel film that has not been dried is laminated continuously, the same defect as above is formed. Will occur. For this reason, the film forming step and the preliminary baking step at 400 to 500 ° C. must be repeated, which is very complicated as a manufacturing method.
[0005]
As described above, since a gel-like substance is used in the process of forming the PZT film on the substrate, defects such as cracks and peeling are likely to occur in the PZT film during or after the manufacturing process. Moreover, if it is going to prevent this defect, a manufacturing method will become very complicated. Such a problem occurs not only when the PZT film is manufactured, but also when another film using a gel substance is manufactured in the manufacturing process. For example, when LaCrO ₃ or the like that can be used as a film or the like for preventing oxidation is produced, the above-described problem may occur.
[0006]
The present invention has been made to solve the above-described problems, and even when a gel-like substance is used in the manufacturing process, it does not cause defects such as cracks and peeling, and is inexpensive and simple. A method for producing a film by a simple method is provided.
[0007]
Further, the present invention can freely set the thickness of the film without causing defects such as cracks and peeling even when a gel-like substance is used in the production process, and relatively The present invention provides a method for producing a film that enables formation of a thick film (for example, 1 μm or more).
[0008]
Furthermore, the present invention provides a method for producing a PZT film by an inexpensive and simple method without causing defects such as cracks and peeling, and a PZT film produced by such a production method.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problem, a film manufacturing method according to the invention of claim 1 includes a lamination step of alternately laminating a metal layer containing a metal and a gel layer made of a gel substance on the substrate, and the lamination A heat treatment step of performing a heat treatment in which the metal of the metal layer diffuses and the metal layer and the gel layer are mixed with respect to each metal layer and each gel layer laminated in the step.
[0010]
That is, in the laminating step, a first metal layer containing a metal is formed on the substrate, a first gel layer made of a gel material is formed on the first metal layer, and further, the first metal layer is formed. A second metal layer is formed on the gel layer, and a second gel layer is formed on the second metal layer. By repeating such film formation, metal layers and gel layers are alternately laminated. Thereby, the gel-like substance is separated into layers by the metal layer.
[0011]
Here, the thickness per layer of the gel layer in the laminating step is such that the stress caused by the shrinkage during drying of the gel layer is greater than the adhesion to the metal layer formed on the upper side or the lower side of the gel layer. Set to be smaller. Further, in the laminating step, the layer formed first on the substrate is not limited to the metal layer but may be a gel layer.
[0012]
Further, in the heat treatment step subsequent to the lamination step, heat treatment is performed on each metal layer and each gel layer laminated on the substrate. Thereby, the metal of each metal layer diffuses and is mixed with the gel-like substance of each gel layer that has been separated into layers. As a result, a film composed of the metal contained in the metal layer and the substance contained in the gel layer is formed on the substrate.
[0013]
According to such a manufacturing method, since the gel-like substance is separated into layers by the metal layer in the laminating step, shrinkage of the gel-like substance at the time of drying can be reduced. Accordingly, it is possible to prevent the film from being cracked or peeled off during the manufacturing process or after the manufacturing. Further, if the metal layer and the gel layer are alternately formed many times, the film thickness can be increased. Accordingly, it is possible to form a relatively thick film (for example, 1 μm or more) while preventing the occurrence of cracks and peeling.
Method for producing a membrane according to the invention of claim 2, in the heat treatment step, thereby changing the composite oxide by mixing the said metal layer gel layer.
[0014]
According to a third aspect of the present invention, there is provided a film manufacturing method in which, in the laminating step, a metal layer containing a metal and a gel layer made of hydroxide, hydrate or hydrate are alternately laminated on a substrate. It is.
[0015]
That is, the hydroxide, hydrate or water-containing product is in a gel form. By alternately laminating gel layers and metal layers made of such a gel-like substance, the gel layers can be separated by the metal layers. Thereby, the shrinkage | contraction of the gel layer at the time of drying can be reduced, and it can prevent that a crack and peeling arise in a film | membrane during a manufacture process or after manufacture.
[0016]
According to a fourth aspect of the present invention, there is provided a method of manufacturing a PZT film comprising: a lamination step of alternately laminating a metal layer containing lead and a gel layer containing zirconium and titanium on a substrate; and each metal laminated by the lamination step. A heat treatment step for heat treating the layer and each gel layer.
[0017]
That is, in the lamination process, the gel layer containing zirconium and titanium is in a gel form. In the laminating step, the gel-like gel layer and the metal layer are alternately laminated. Thereby, the gel layer is separated into layers by the metal layer.
[0018]
Further, in the heat treatment step subsequent to the lamination step, heat treatment is performed on each metal layer and each gel layer laminated on the substrate. Thereby, the lead of each metal layer diffuses and is mixed with the zirconium and titanium of each gel layer separated into layers. As a result, a PZT film is formed on the substrate.
[0019]
According to such a manufacturing method, since the gel substance is separated into layers by the metal layer in the laminating step, the gel layer can be prevented from shrinking due to drying. Accordingly, it is possible to prevent the film from being cracked or peeled off during the manufacturing process or after the manufacturing. Further, if the metal layer and the gel layer are alternately formed many times, the film thickness can be increased. Therefore, it is possible to form a relatively thick PZT film while preventing the occurrence of cracks and peeling.
[0020]
According to a fifth aspect of the present invention, there is provided a method for producing a PZT film, wherein the thickness of each gel layer is 0.8 μm or less in the laminating step.
[0021]
Thereby, the stress produced by the shrinkage | contraction at the time of drying of a gel layer becomes smaller than the adhesive force with respect to the metal layer formed in the upper side or lower side of a gel layer. As a result, it is possible to prevent the gel-like substance from shrinking during drying and to prevent the PZT film from cracking or peeling.
[0022]
According to a sixth aspect of the present invention, there is provided a method of manufacturing a PZT film comprising: a metal layer forming step of forming a metal layer by immersing a substrate in a solution containing lead and performing electrolysis in the laminating step; A gel layer forming step of alternately forming a gel layer by immersing the substrate in the solution to be included and performing electrolysis is performed.
[0023]
Thereby, a solution containing lead and a solution containing zirconium and titanium are prepared, and the metal layer and the gel layer can be alternately laminated by simply immersing the substrate in these two types of solutions. Therefore, the equipment used for manufacturing can be greatly simplified, and the manufacturing cost can be reduced.
[0024]
The PZT film obtained by the above manufacturing method is obtained by alternately laminating a metal layer containing lead and a gel layer containing zirconium and titanium, and then subjecting each metal layer and each gel layer to heat treatment. Is.
[0025]
Such a PZT film is highly reliable without defects such as cracks and peeling even if the film thickness is large.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0027]
First, a PZT film manufacturing method will be described with reference to FIGS. 1 to 7 as a first embodiment of a film manufacturing method using a gel material according to the present invention.
[0028]
FIG. 1 shows an outline of a method for manufacturing a PZT film according to the present embodiment. As shown in FIG. 1, the PZT film manufacturing method according to the present embodiment includes a lower electrode forming step 51, a metal layer forming step 52, a gel layer forming step 53, a drying step 54, a firing step 55, and an upper electrode forming step 56. Composed.
[0029]
Hereinafter, each step will be described in detail. Since the PZT film requires electrodes on the upper and lower sides in any application of actuators, capacitors, and memories, first, in the lower electrode formation step 51, as shown in FIG. 2, the PZT film has conductivity on the ceramic substrate 1. The lower electrode 2 is formed. As for the method of forming the lower electrode 2, there is a conductive property on a part of the substrate 1 that is an insulator, such as a film forming method such as electroless plating, vapor deposition, sputtering, or bonding a film-like or sheet-like conductive material. There is no particular limitation as long as it can be applied. As the conductive material used for the lower electrode 2, an oxidation-resistant metal material (gold, platinum, etc.) is desirable because firing is required in a later step. The thickness of the lower electrode 2 is not particularly limited, but is 1 μm, for example, in the present embodiment.
[0030]
Next, in the metal layer forming step 52, as shown in FIG. 3, a metal layer 3 made of metal Pb (lead) is formed on the lower electrode 2 formed on the substrate 1. In this case, since it is necessary to form the metal Pb in layers, the method for forming the metal layer 3 is preferably a film forming method such as electroplating, electroless plating, vapor deposition, or sputtering. The film thickness per layer of the metal layer 3 is determined by the final thickness of the PZT film, the number of layers of the metal layer and the gel layer, and the like. The film thickness of the metal layer 3 in this embodiment is about 0.5 μm.
[0031]
Next, in the gel layer forming step 53, as shown in FIG. 4, the gel layer 4 made of a hydroxide, hydrate or hydrate of Zr (zirconium) and Ti (titanium) is formed on the metal layer 3. Form. The gel layer 4 can be formed by a sol-gel method or an electrodeposition method. In the present embodiment, the sol-gel method is used. Further, the film thickness per layer of the gel layer 4 is such that the stress generated by the shrinkage when the gel layer 4 is dried is smaller than the adhesion force to the metal layer 3 formed on the upper side or the lower side of the gel layer 4. Set to. Specifically, the film thickness per layer of the gel layer 4 is set to 0.8 μm or less. The film thickness per layer of the gel layer 4 in this embodiment is about 0.5 μm.
[0032]
As shown in FIG. 4, the metal layer 3 and the gel layer 4 are deposited one layer at a time so far, and the total thickness is about 1 μm. When finally forming a PZT film having a film thickness of about 5 μm, for example, as shown in FIG. 1, the metal layer forming step 52 and the gel layer forming step 53 are repeated, as shown in FIG. Metal layers 3 and gel layers 4 are alternately formed in five layers. When a PZT film having a thickness of about 10 μm is finally formed, for example, the metal layer forming step 52 and the gel layer forming step 53 as shown in FIG. Four layers may be formed alternately by four layers. Thus, the final film thickness of the PZT film can be freely set by the number of layers of the metal layer 3 and the gel layer 4.
[0033]
Next, in the drying step 54, the laminated film formed of each metal layer 3 and each gel layer 4 formed as shown in FIG. 5 is dried at 100 ° C. for about 10 minutes. In the next firing step 55, the laminated film is fired to form PZT, which is a composite oxide of Pb, Zr, and Ti, as shown in FIG. Firing is performed in the atmosphere at a temperature of about 500 to 900 ° C. for 10 minutes or more. As a result, the metal Pb of the metal layer 3 diffuses and is mixed with the gel layer that has been separated into layers, and the hydroxide, hydrate, or hydrated substance of the gel layer changes to an oxide.
[0034]
Finally, in the upper electrode step 56, the upper electrode 6 is formed on the PZT film 5 as shown in FIG. The method for forming the upper electrode 6 is the same as the method for forming the lower electrode 2 described above.
[0035]
According to the manufacturing method as described above, since the laminated film which is a precursor of PZT is formed by alternately laminating the metal layer 3 and the gel layer 4, the gel layer 4 which is not dried is formed into the metal layer. 3 can be separated. That is, as shown in FIG. 5, a lower electrode 2 mainly composed of gold is formed on a ceramic substrate 1 with a thickness of 1 μm, and a metal Pb with a thickness of 0.5 μm is formed on the lower electrode 2. The metal layers 3 and the gel layers 4 made of Zr and Ti hydroxides, hydrates or hydrates having a thickness of 0.5 μm are alternately laminated to form five layers. Thus, according to the manufacturing method according to the present embodiment, Zr and Ti hydroxides, hydrates or hydrates can be separated into layers by the metal layer 3. Therefore, shrinkage of the gel layer 4 during drying can be suppressed, and cracking or peeling can be prevented from occurring in the gel layer 4 or the like. In particular, in this embodiment, since the thickness per one layer of the gel layer 4 is set to 0.8 μm or less (about 0.5 μm), the gel layer is compared with the adhesion to the upper or lower metal layer 3 of the gel layer 4. 4 can reduce the stress due to shrinkage during drying, and more reliably prevent defects such as cracks.
[0036]
Moreover, according to the manufacturing method by this embodiment, it is not necessary to perform the temporary baking process every time the gel layer 4 is formed, and the whole process can be simplified.
[0037]
Next, as a second embodiment of the method for producing a film using a gel material according to the present invention, a method for producing a PZT film will be described with reference to FIGS. The feature of this embodiment is that the electrolytic deposition method is used for forming a metal layer containing metal Pb and a gel layer made of a hydroxide, hydrate or hydrate of Zr and Ti. In the present embodiment, the same components as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted.
[0038]
Similar to the first embodiment described above, after forming the lower electrode 2 on the substrate 1, the metal layer 3 containing the metal Pb is formed on the lower electrode 2. In this metal layer forming step, as shown in FIG. 8, the substrate 1 on which the lower electrode 2 is formed is immersed in a lead electrodeposition bath 12 together with a platinum counter electrode 11. The lead electrodeposition bath 12 contains lead nitrate at a concentration of 0.002 to 0.2M. A DC power supply 13 is connected so that the substrate 1 is a cathode and the platinum counter electrode 11 is an anode, and electrolysis is performed by the DC power supply 13. When electrolysis is performed by the DC power source 13, lead ions are reduced at the cathode and metal Pb is deposited on the lower electrode 2 of the substrate 1. Electrolysis is performed at a potential of -700 mV. Thereby, the metal layer 3 having a thickness of about 0.5 μm can be obtained by electrolysis for 5 minutes. In addition, the electrolyte solution used for electrodeposition is not restricted to the above-mentioned thing, Other solutions may be sufficient if it is a liquid which can deposit metal lead. The electrolysis conditions are appropriately set so as to be suitable for the electrolytic solution used for electrodeposition. When the electrolysis is completed, the substrate 1 and the platinum counter electrode 11 are pulled up from the lead electrodeposition bath 12.
[0039]
Next, the gel layer 4 is formed on the metal layer 3. In this gel layer forming step, as shown in FIG. 9, the substrate 1 and the platinum counter electrode 11 are immersed in a zirconium + titanium electrodeposition bath 14 while the substrate 1 and the platinum counter electrode 11 are connected to the DC power source 13, and electrolysis is performed. Do. This zirconium + titanium electrodeposition bath 14 contains zirconyl nitrate at a concentration of 0.001 to 0.1M and titanium trichloride at a concentration of 0.001 to 0.1M. Electrolysis is performed at a potential of -4V. Thereby, the gel layer 4 having a film thickness of about 0.5 μm is obtained by electrolysis for 30 seconds. Note that the electrolytic solution used for electrodeposition in this step is not limited to the above-described one, and other solutions may be used as long as they generate titanium oxide ions and zirconyl ions in the bath. The electrolysis conditions are also set accordingly. When the electrolysis is completed, the substrate 1 and the platinum counter electrode 11 are pulled up from the zirconium + titanium electrodeposition bath 14.
[0040]
Further, the substrate 1 and the platinum counter electrode 11 are alternately immersed in a lead electrodeposition bath 12 and a zirconium + titanium electrodeposition bath 14 to repeatedly perform electrolysis. Thereby, the metal layers 3 and the gel layers 4 are alternately stacked on the substrate 1. By repeating such a process until the laminated film of the metal layer 3 and the gel layer 4 reaches a desired film thickness, the PZT film 5 is formed. For example, by repeating five cycles of alternating electrolysis using the lead electrodeposition bath 12 and the zirconium + titanium electrodeposition bath 14, the metal layer 3 having a thickness of about 0.5 μm and the thickness per layer of about 0.5 μm. A laminated film having a film thickness of about 5 μm composed of the 5 μm gel layer 4 is obtained. Thereafter, similarly to the first embodiment described above, the PZT film 5 is formed through the drying process and the baking process, and then the upper electrode 6 is formed on the PZT film 5.
[0041]
Thus, in this embodiment, since the electrodeposition method is used to form the metal layer 3 and the gel layer 4, the PZT film can be formed very simply by changing the electrolytic bath used for electrodeposition. Therefore, the equipment for manufacturing the PZT film can be simplified, and the manufacturing cost can be reduced.
[0042]
In each of the above embodiments, the metal layer 3 is first formed on the substrate 1 and then the gel layer 4 is formed thereon. Thereafter, the metal layer 3 and the gel layer 4 are laminated in this order. However, the present invention is not limited to this, and the metal layer 3 may be formed after the gel layer 4 is first formed on the substrate 1, and then the gel layer 4 and the metal layer 3 may be alternately stacked.
[0043]
In each of the above embodiments, the method for producing a PZT film is taken as an example of the method for producing a film using a gel substance, but the present invention is not limited to this. For example, when manufacturing a film made of LaCrO ₃ that can be used as a film for preventing oxidation, the manufacturing method as described above can be applied. In this case, a film made of LaCrO ₃ is manufactured by alternately laminating metal layers containing Cr (chromium) and gel layers containing La (lanthanum).
[0044]
【The invention's effect】
As described above in detail, according to the film manufacturing method of the invention of claim 1, a lamination step of alternately laminating a metal layer containing a metal and a gel layer made of a gel substance on the substrate, and the lamination Since each metal layer and each gel layer laminated by the process includes a heat treatment step of performing a heat treatment in which the metal of the metal layer diffuses and the metal layer and the gel layer are mixed , In the process, the gel layer made of the gel substance can be separated by the metal layer, and the substance on the gel can be prevented from shrinking during drying. Accordingly, it is possible to prevent the film from being cracked or peeled off during the manufacturing process or after the manufacturing.
[0045]
Further, if the metal layer and the gel layer are alternately formed many times, the film thickness can be increased. Therefore, it is possible to form a relatively thick film while preventing the occurrence of cracks and peeling.
[0046]
Furthermore, since it is not necessary to perform firing or the like each time a gel layer is formed, the manufacturing process is simple and the manufacturing cost is low.
[0047]
According to the film manufacturing method of the invention of claim 3, in the laminating step, a metal layer containing metal and a gel layer made of hydroxide, hydrate or hydrate are alternately laminated on the substrate. Thus, the hydroxide, hydrate or hydrate can be separated into layers by the metal layer. Thereby, it can prevent that the gel layer which consists of a hydroxide, a hydrate, or a hydrate contains shrinkage | contraction by drying, and can prevent that a film | membrane cracks and peels after a manufacture process or manufacture.
[0048]
According to the method of manufacturing a PZT film according to the invention of claim 4 , lamination is performed by alternately laminating a metal layer containing lead and a gel layer containing zirconium and titanium on the substrate, and the lamination step. Since each metal layer and each gel layer are configured to include a heat treatment step for performing heat treatment, in the lamination step, the gel layer containing zirconium and titanium can be separated into layers by the metal layer. Thereby, it can prevent that a gel layer shrink | contracts by drying, and can prevent that a crack (crack) and peeling arise in a film | membrane after a manufacture process or manufacture.
[0049]
Further, if the metal layer and the gel layer are alternately formed many times, the film thickness can be increased, and a relatively thick PZT film can be formed while preventing the occurrence of cracks and peeling.
[0050]
Furthermore, since it is not necessary to perform firing or the like each time a gel layer is formed, the manufacturing process is simple and the manufacturing cost is low.
[0051]
Further, according to the method of manufacturing a PZT film according to the invention of claim 5 , since the thickness of each gel layer is 0.8 μm or less in the laminating step, the stress caused by the shrinkage during drying of the gel layer is reduced. It can be made smaller than the adhesion force to the metal layer formed on the upper side or the lower side. Thereby, it can prevent that a gel-like substance shrink | contracts at the time of drying, and can prevent that a crack and peeling arise in a PZT film | membrane.
[0052]
According to the method for producing a PZT film of the invention of claim 6 , in the laminating step, a metal layer forming step of forming a metal layer by immersing the substrate in a solution containing lead and performing electrolysis, zirconium and titanium Since the gel layer forming step of alternately forming a gel layer by immersing the substrate in a solution containing selenium and performing electrolysis is performed, the substrate is alternately turned into a solution containing lead and a solution containing zirconium and titanium. A metal layer and a gel layer can be alternately laminated and formed only by being immersed. Therefore, the equipment used for manufacturing can be greatly simplified, and the manufacturing cost can be reduced.
[0053]
According to the PZT film obtained by the above-described manufacturing method, the metal layers containing lead and the gel layers containing zirconium and titanium are alternately laminated, and then the metal layers and the gel layers are subjected to heat treatment. Therefore, even if the film thickness is large, there are no defects such as cracks and peeling. Therefore, reliability can be improved.
[Brief description of the drawings]
FIG. 1 is a flowchart showing a method of manufacturing a PZT film according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a state in which a lower electrode is formed on a substrate in the first embodiment of the present invention.
FIG. 3 is a cross-sectional view showing a state in which a metal layer is formed on the lower electrode in the first embodiment of the present invention.
FIG. 4 is a cross-sectional view showing a state in which a gel layer is formed on a metal layer in the first embodiment of the present invention.
FIG. 5 is a cross-sectional view showing a state in which metal layers and gel layers are alternately stacked on a substrate in the first embodiment of the present invention.
FIG. 6 is a cross-sectional view showing a state in which a PZT film is formed on a substrate in a firing step according to the first embodiment of the present invention.
FIG. 7 is a cross-sectional view showing a state in which an upper electrode is formed on a PZT film in the first embodiment of the present invention.
FIG. 8 is an explanatory diagram showing a step of forming a metal layer by electrolytic deposition in the second embodiment of the present invention.
FIG. 9 is an explanatory view showing a step of forming a gel layer by electrolytic deposition in the second embodiment of the present invention.
[Explanation of symbols]
1 Substrate 2 Lower electrode 3 Metal layer 4 Gel layer 5 PZT film 6 Upper electrode 12 Lead electrodeposition bath 14 Zirconium + titanium electrodeposition bath

Claims (6)

A method for producing a film using a gel-like substance,
Lamination process of alternately laminating a metal layer containing metal and a gel layer made of the gel material on the substrate;
Production of a film comprising a heat treatment step of performing a heat treatment in which the metal of the metal layer diffuses and the metal layer and the gel layer are mixed with each metal layer and each gel layer laminated by the lamination step Method. The method for producing a film according to claim 1, wherein in the heat treatment step, the metal layer and the gel layer are mixed and changed into a composite oxide. Wherein in the laminating step, a metal layer comprising a metal on a substrate, a hydroxide method of film according to claim 1 or 2, laminating a gel layer composed of a hydrate or a hydrous substance alternately. Lamination process of alternately laminating a metal layer containing lead and a gel layer containing zirconium and titanium on a substrate;
The manufacturing method of a PZT film | membrane provided with the heat processing process which heat-processes with respect to each metal layer and each gel layer which were laminated | stacked by the said lamination process. The method for producing a PZT film according to claim 4 , wherein in the laminating step, the thickness of each gel layer is set to 0.8 μm or less. The laminating step includes a metal layer forming step of forming a metal layer by immersing the substrate in a solution containing lead and performing electrolysis, and a gel layer by immersing the substrate in a solution containing zirconium and titanium and performing electrolysis. The method for producing a PZT film according to claim 4 or 5 , wherein the gel layer forming step for forming the film is alternately performed.

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