JP2007059631A - METHOD AND DEVICE FOR FORMING DIELECTRIC THIN FILM OF ABOx TYPE PEROVSKITE CRYSTAL STRUCTURE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing device for obtaining a dielectric thin film with an ABO<SB>X</SB>type perovskite crystal structure whose dielectric constant is high and leak current is little. <P>SOLUTION: A coating film formation device is constituted to have a coating unit for applying a coating liquid containing a precursor of a thin film with the crystal structure to a substrate; a heating unit for carrying out heating treatment as a pretreatment of baking; a substrate carrying means for carrying the substrate from the coating unit to the heating unit; a housing wherein the coating unit, the heating unit and the substrate carrying means are disposed; an air flow forming means for forming air flow in a carrying region; and a neutralization treatment part for neutralizing and eliminating CO<SB>2</SB>in gas taken in by the air flow forming means by alkaline component. Consequently, it is possible to restrain reaction between a compound in a coating film and CO<SB>2</SB>by carrying the substrate in the carrying region, while restraining CO<SB>2</SB>concentration in the carrying region and to form a path which induces leak current in the film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an apparatus and a method for forming a dielectric thin film made of, for example, barium titanate having an ABO _X- type perovskite structure.

  In general, a power supply system for a CPU (Central Processing Unit) of a computer is configured to be supplied with power from a capacitor on a printed circuit board in order to eliminate a voltage drop. However, since the operating speed of the CPU is rapidly increasing, the timing of power supply from the capacitor is delayed during the operation of the CPU, and as a result, the operating speed of the CPU is limited. The reason why the power supply from the capacitor cannot catch up in this way is that the distance between the capacitor and the CPU on the printed circuit board can be reduced only to some extent for the convenience of mounting. Therefore, there is an attempt to make the distance between the two substantially zero by mounting a capacitor made of a dielectric thin film on a printed circuit board and placing a CPU on the capacitor to directly connect them.

  For example, barium titanate (BaTiO3) having an ABOx type perovskite crystal structure is known as one of materials attracting attention as such a dielectric thin film, and a sol-gel method is known as its production method (Patent Literature). 1). The sol-gel method is a coating liquid containing an organometallic compound that is a precursor of barium titanate, more specifically a composition for forming a dielectric film (sol-gel material) containing, for example, a metal alkoxide containing Ba and Ti and an organic solvent. ) Is applied onto the substrate and hydrolyzed to form a metal-oxygen-metal bond to form a precursor film, which is then heated to form a sintered body made of a crystal having a perovskite structure. It is a technique to obtain. The thin film obtained by this method has low crack resistance, and when the coating film thickness is 100 nm or more once, cracks are generated, making it difficult to obtain a good coating film. For this reason, it is necessary to make the coating thickness of one coating 100 nm or less.

For this reason, multilayer coating is performed to increase the overall film thickness of the barium titanate thin film, but Ba (barium) ions, Ba (OH) 2 (barium hydroxide) or BaO (oxidation) contained in the coating film. Barium) absorbs CO2 (carbon dioxide) in the atmosphere and reacts with the CO2 to form BaCO3 (barium carbonate). Therefore, before baking the coating film, specifically when the coating film is exposed to the atmosphere, for example, when applying the coating liquid, when drying the thinner of the coating film or when transporting the substrate to the baking furnace, BaCO3 will be mixed in the barium titanate thin film formed after firing. Since BaCO3 mixed in the thin film becomes a path for carrying current, there is a problem that leakage current is increased.
Furthermore, since moisture exists in the atmosphere, CO2 and moisture react to produce H2CO3 (carbonated water). Since this carbonated water has a low surface tension, it adheres to the surface of the coating film and then enters the coating film. It is said that there is also a mechanism that penetrates and as a result CO2 is taken into the coating film. In this case, it can be said that the moisture in the air is a catalyst for taking CO2 into the membrane.

  Such incorporation of CO2 into the film occurs every time one coating film is formed. Therefore, when multiple layers are formed, the amount of CO2 incorporation increases, and as a result, leakage current tends to flow, and therefore the coating film is formed in multiple layers. It is not a good idea to make it. In order to completely decompose BaCO3 once generated in the coating film, it is necessary to heat at a high temperature of 900 ° C. or higher, for example.

Therefore, a method has been proposed in which the size of the barium titanate crystal particles is about 100 nm (Non-patent Document 2). This technique is a technique in which a material obtained by hydrolyzing and dispersing the sol-gel material under special conditions is used as a coating liquid, and particles having an average particle diameter of 100 nm or less are dispersed in the coating liquid. For convenience of explanation, when such a thin film is referred to as a nanoparticle thin film, when forming a nanoparticle barium titanate thin film, the thickness of a single coating film can be increased. The number of stacked layers can be reduced as compared with a barium titanate thin film of crystal particles on the order of several nanometers obtained by the gel method, and a single layer is also possible. For this reason, there is an advantage that the amount of CO2 taken in during the film forming process can be suppressed.
However, in order to realize the commercialization of capacitors, it is necessary to further improve the leak characteristics, and it is necessary to devise measures to further suppress the incorporation of CO2 into the thin film.

JP-A-8-316433 (paragraph 0021) Fukuoka Prefectural Industrial Technology Center research report No14 (published on the Internet in 2004)

The present invention has been made under such a background, and its object is to produce a dielectric thin film made of, for example, barium titanate having an ABO _X- type perovskite crystal structure, which has a high dielectric constant and leak. An object of the present invention is to provide an apparatus and a method for forming a dielectric thin film with low current.

The present invention relates to a coating film forming apparatus for producing a thin film having an ABOX-type perovskite structure crystal structure obtained by applying a coating solution to a substrate and further firing the substrate, and the crystal structure of the ABOX-type perovskite structure is provided. A coating unit for applying a coating liquid containing a composition for forming a dielectric film of a thin film on a substrate; a heating unit for performing a heat treatment that is a pretreatment for baking on the coating film on the substrate; A substrate transport means for transporting the substrate from the coating unit to the heating unit, a housing for a main body in which the coating unit, the heating unit and the substrate transport means are disposed, and an air flow in a transport area by the substrate transport means. An air flow forming means for forming, and a neutralization processing section for neutralizing and removing carbon dioxide in the gas taken into the air flow forming means by an alkali component; Characterized by comprising a.
Here, “sintering” means that the dielectric film-forming composition obtained by evaporating the organic solvent is crystallized from an amorphous state.
The value of X varies depending on the amount of oxygen in the processing atmosphere in each step of forming the dielectric thin film having the ABOx type perovskite structure, but is included in the range of 2.5 to 3.5.

  The airflow forming unit may form an airflow in the housing for the main body, or may be provided in combination with the substrate transfer unit. When airflow forming means is provided in the substrate transfer means, for example, a porous plate is disposed so as to face the surface of the substrate held by the transfer arm, and airflow falls on the shower from the porous plate onto the substrate. Can do. Further, the airflow forming means may include a first filter unit for removing particles.

  The neutralization processing unit includes a container that accommodates an alkaline solution, and a bubbling unit that supplies a gas into the alkaline solution for bubbling, provided in a gas supply path that sends gas to the airflow forming unit. It may be configured as a chemical filter including the second filter portion to which the alkali component is attached. In addition, it is preferable to include a circulation unit for circulating the gas supplied from the airflow forming unit to the airflow forming unit via the neutralization processing unit.

In the present invention, the coating unit uses a substrate mounting table provided in a casing for the coating unit, and a coating liquid containing a composition for forming a dielectric film of a thin film having an ABO _X- type perovskite crystal structure. Including a nozzle for coating and an airflow forming means for forming an airflow in the casing for the coating unit, and neutralizing and removing carbon dioxide in the gas taken into the airflow forming means by an alkali component It is good also as a structure which provided the sum processing part.
The heating unit is provided in the container, and includes a mounting table on which the substrate coated with the coating liquid is placed, a heating unit that heats the substrate, and an airflow forming unit that forms an airflow in the container. Further, a configuration may be provided in which a neutralization processing unit is provided for neutralizing and removing carbon dioxide in the gas taken into the airflow forming means for the heating unit with an alkali component.
Further, the neutralized gas as described above is supplied into the casing constituting the main body, and the coating unit or the heating unit may be in an inert gas atmosphere such as nitrogen gas.

Another invention is a coating film forming apparatus for manufacturing a thin film having a crystal structure of an ABOX type perovskite structure obtained by applying a coating liquid to a substrate and further baking the substrate, and the substrate provided in the housing , A nozzle for applying a coating solution containing a thin film dielectric film-forming composition having an ABO _X- type perovskite crystal structure to a substrate, and airflow formation for forming an airflow in the housing A coating unit including a means, a neutralization treatment section for neutralizing and removing carbon dioxide in the gas taken into the airflow forming means by an alkali component, and a pretreatment for baking the coating film on the substrate A heating unit for performing a certain heat treatment and a substrate transfer means for transferring the substrate from the coating unit to the heating unit are provided.
The neutralization processing unit for the coating unit may include a second filter unit to which an alkali component is attached, or a container for storing an alkaline solution, and a bubbling means for supplying gas into the alkaline solution and bubbling. It is good also as a structure provided with these.

Still another invention is a coating film forming apparatus for manufacturing a thin film having a crystal structure of an ABOX type perovskite structure obtained by applying a coating liquid to a substrate and further baking, and has a structure of an ABO _X type perovskite structure. A coating unit for coating a substrate with a coating liquid containing a composition for forming a dielectric film of a thin film having a crystal structure; a mounting table provided in a container and on which a substrate coated with the coating liquid is placed; A heating unit for performing a heat treatment that is a pretreatment for baking on the coating film on the substrate, and a heating unit for forming an airflow in the container, A neutralization treatment section for neutralizing and removing carbon dioxide in the gas taken into the airflow forming means with an alkali component; and a substrate transporting means for transporting the substrate from the coating unit to the heating unit. It is characterized by that. The neutralizing section for the heating unit is provided in a gas supply path for sending gas to the airflow forming means for the coating unit, and a bubbling for supplying and bubbling the gas into the alkaline solution. And means.
As described above, the neutralized gas is supplied into the casing in the heating unit and the coating unit, and the inside of the casing that forms the coating film forming apparatus main body has an inert gas atmosphere such as nitrogen gas. Also good.

The composition for forming a dielectric film includes (i) particles having an ABOx type crystal structure including metal species A and B, (ii) metal alkoxides including metal species A and B, metal carboxylates, metals At least one component selected from the group of complexes and metal hydroxides, and (iii) an organic solvent, may contain at least one of (i) and (ii) and (iii) . Further, for example, in the thin film having the ABO _X- type perovskite structure, the metal species A is one or more metals selected from lithium, sodium, calcium, strontium, barium, and lanthanum, and the metal species B is titanium, zirconium, and tantalum. A thin film having an ABO _X perovskite crystal structure, which is one or more metals selected from niobium, may be used.

The method of the present invention is a coating film forming method for producing a thin film having a crystal structure of an ABO _X- type perovskite structure obtained by applying a coating liquid to a substrate and further baking the substrate, and the substrate is placed on a mounting table. A thin film dielectric film having a crystal structure of an ABO _X- type perovskite structure while neutralizing and removing carbon dioxide in the gas with an alkali component and supplying the gas to the substrate on the mounting table And a step of applying a coating liquid containing a forming composition to a substrate on a mounting table.
In the method of the present invention, carbon dioxide in a gas is neutralized and removed by an alkali component, and the step of supplying the gas to the transport region of the substrate and the substrate coated with the coating liquid are applied to the coating film. And a step of conveying through the conveying region to a heating unit for performing a heat treatment that is a pretreatment for baking. In the method of the present invention, the step of transporting the substrate coated with the coating liquid to the heating unit, the carbon dioxide in the gas is neutralized and removed by the alkali component, and the gas is supplied into the heating unit. In the heating unit, a heat treatment that is a pretreatment for baking the coating film on the substrate may be included.

  According to the coating film forming apparatus of the present invention, the substrate transporting means for transporting the substrate from the coating unit to the heating unit, the airflow forming means for forming an airflow in the substrate transporting area by the substrate transporting means, and the airflow forming means And a neutralization treatment unit for neutralizing and removing carbon dioxide in the gas taken in, thereby forming an air stream from which carbon dioxide has been removed in the transport region, and adjusting the carbon dioxide concentration in the transport region. The substrate can be transferred in this transfer area by the substrate transfer means while being suppressed. Accordingly, since carbon dioxide is prevented from being taken into the coating film formed on the substrate during the conveyance, a product generated by the reaction between the compound contained in the coating film and carbon dioxide is mixed into the coating film. That can be suppressed. As a result, in the dielectric thin film having an ABOx type perovskite crystal structure obtained by firing the substrate thus transported, the product is prevented from being mixed in the ABOx type perovskite crystal structure film. The formation of a path for carrying a current due to the product in the crystal structure film is suppressed. As a result, it is possible to suppress the leakage current while securing a high dielectric constant while achieving a reduction in the thickness of the ABOx type perovskite crystal structure film.

According to another coating film forming apparatus, there is provided a coating unit including a substrate mounting table provided in the housing and a nozzle for supplying a coating liquid to the substrate, and means for forming an air flow in the housing; A neutralization treatment section for neutralizing and removing carbon dioxide in the gas taken in by the airflow forming means, thereby forming an airflow from which carbon dioxide has been removed in the housing to form a carbon dioxide inside the housing. An atmosphere in which the carbon concentration is suppressed can be formed, and a coating liquid can be supplied to the substrate in the atmosphere to form a coating film. Accordingly, when the coating film is formed, the carbon dioxide uptake into the coating film is suppressed, so that a product generated by the reaction between the compound contained in the coating film and carbon dioxide is mixed into the film. Can be suppressed.
Furthermore, according to the coating film forming method of the present invention, since the coating liquid is applied to the substrate in a gas atmosphere from which carbon dioxide has been removed, the same effect can be obtained.

Hereinafter, a dielectric thin film made of BaTiO3, which is an ABO _X- type perovskite film according to the present invention, is formed on a substrate W made of, for example, a silicon wafer (hereinafter referred to as a wafer) (specifically, the surface of the lower electrode film on the wafer). A coating film forming apparatus 1 used for the above will be described with reference to the drawings. FIG. 1 is a perspective view of the coating film forming apparatus 1, and FIG. 2 is a plan view thereof. The coating film forming apparatus 1 includes a substrate carrier B1 into which a substrate carrier C (hereinafter simply referred to as “carrier”) C serving as a transport container in which a plurality of, for example, 25 substrates W are stored in a shelf shape, and a substrate W. On the other hand, a processing section B2 for performing coating and heating (baking) processing and a ceiling block 4 are provided. The carrier placement section B1 is provided with a carrier station 11 on which a plurality of carriers C can be placed side by side, and a delivery means 12 for taking out the substrate W from the carrier C and delivering it to the processing section B2.

  A processing unit B2 is connected to the back side of the carrier mounting unit B1, and the processing unit B2 is surrounded by a casing (main body housing) 20 having an open top. A transport port 21 that can be opened and closed by a shutter 22 is provided on a side wall of the housing 20 that faces the carrier mounting portion B1, and the delivery means 12 enters the housing 20 through the transport port 21 and is described later. The substrate W can be delivered to the delivery unit 25 of the shelf unit 24A. For example, the shutter 22 is configured to be closed except when the delivery means 12 enters the housing 20 so that the inflow of gas from the carrier placement unit B1 to the processing unit B2 is suppressed.

  The configuration within the housing 20 of the processing unit B2 will be described with reference to FIG. FIG. 3 is an exploded view showing the main transfer arm 23, the coating unit 5 and the shelf unit 24A, which are substrate transfer means included in the processing section B2, on the same plane. In the center of the processing section B2, there is provided a main transfer arm 23 that is configured to be movable back and forth, freely movable up and down, and rotatable about a vertical axis, and on the right side of the main transfer arm 23 as viewed from the carrier placement section B1. Two coating units 5 stacked in two stages are provided so as to continue to the back side. In addition, shelf units 24A, 24B, and 24C in which heating and cooling units are stacked are provided on the front, rear, and left sides of the main transfer arm 23, respectively. The shelf unit 24A includes a plurality of heating units 6, a delivery unit 25, and the above-described units. A plurality of cooling units 26 for cooling the substrate W heated by the heating unit 6 to a predetermined temperature are stacked in this order from above. The shelf unit 24B and the shelf unit 24C are configured in the same manner as the shelf unit 24A except that the delivery unit 25 is not provided, for example, and the main transfer arm 23 includes the units constituting the shelf units 24A to 24C and the units described above. The substrate W can be delivered to the coating unit 5. 3 denotes a guide for moving the main transfer arm 23 in the vertical direction.

  For example, a plurality of exhaust ports 28 are opened at intervals at the bottom of the housing 20, and an exhaust pipe 29 is connected to each exhaust port 28. For example, the exhaust pipes 29 extend outside the housing 20 and are joined together in the middle, and the ends of the joined exhaust pipes 29 are immersed in a container 32 constituting the bubbling device 3 which is a neutralization processing part. Is provided. In the figure, reference numeral 31 denotes a pressure pump provided in the joined exhaust pipe 29, which sucks the gas in the housing 20 through the exhaust port 28 and pressurizes and supplies this gas to the downstream side of the exhaust pipe 29. It is like that.

The container 32 of the bubbling device 3 is configured such that the inside of the container 32 is hermetically sealed by closing the opening 32b with a cap 32a. For example, Ca (OH) 2 ( A solution 33 in which calcium hydroxide is dissolved is stored. The exhaust pipe 29 and a supply pipe 36 to be described later are configured to be removable from the container 32 by a joint (not shown). The cap 32a is removed and the solution 33 in the container 32 is exchanged and filled through the opening 32b. Can be done. In the figure, reference numeral 34 denotes a nozzle for bubbling connected to the end of the exhaust pipe 29. As described above, the gas pushed to the downstream side of the exhaust pipe 23 by the pressure pump 31 is supplied from the nozzle 34 to the solution 33. When discharged and bubbled, the following chemical reaction occurs and carbon dioxide (CO2) contained in the discharged gas is neutralized and removed.
Ca (OH) 2 + CO2 → CaCO2 + H2O
In addition, one end of a supply pipe 36 that is an air flow forming means for sending the gas in the container 32 to the ceiling block 4 described later is opened in the gas phase portion in the container 32. In the figure, reference numeral 35 denotes a mist filter interposed in the supply pipe 36, and the supply pipe 36 is branched on the downstream side of the mist filter 35 in accordance with the number of filter units F of the ceiling block 4 described later.

  As shown in FIGS. 1 to 3, the ceiling block 4 includes a housing 40 and constitutes a ceiling portion of the processing unit B <b> 2, so that the interior of the housing 20 is generally an airtight space. In this ceiling block 4, a plurality of filter units F, which are airflow forming means, are arranged in parallel in a housing 40, and each filter unit F includes a cleaning filter 41 for removing particles, and above each filter 41. Is provided with a ventilation chamber 43 which is a space surrounded by the filter 41 and the housing 40. The ventilation chamber 43 is partitioned for each region facing each filter 41. The gas supply pipes 36 are connected to the vent chambers 43. As described above, when gas is discharged from the nozzle 34 into the solution 33 and the pressure in the container 32 is increased, CO2 is reduced by the neutralization reaction. The removed gas is supplied into the supply pipe 36. The gas passes through the mist filter 35 and flows into the ventilation chamber 43 in a state where moisture has been removed. The gas passes through the filter 41 and is downflowed to the entire area of the housing 20 to maintain a low CO2 concentration atmosphere. It is like that. The down-flowed gas flows into the exhaust pipe 29 through the exhaust port 28, and is sent again into the solution 33 by the pressure pump 31 so as to be bubbled. In this example, the supply pipe 36, the exhaust pipe 29 and the pressure pump 31 constitute a circulation means for circulating the gas in the housing 20, and the container 32 provided in the circulation path is referred to as “gas supply path” in the claims. This corresponds to the “provided configuration”.

  Next, the coating unit 5 will be described with reference to FIG. The coating unit 5 includes a housing 50. When a region in which the main transport arm 23 moves in the housing 20 is a transport path R1, the substrate W is transported to the side wall of the housing 50 facing the transport path R1. A mouth 51 is provided. The transfer port 51 is provided with a shutter 52 that can be opened and closed. The shutter 52 is closed except when the main transfer arm 23 enters the housing 50, for example. A spin chuck 53 serving as a placement portion for the substrate W is provided inside the housing 50, and the spin chuck 53 is configured to be rotatable about a vertical axis and raised and lowered by a drive unit (not shown). A cup 54 is provided around the spin chuck 53, and a drainage unit (not shown) including an exhaust pipe and a drain pipe is provided on the bottom surface of the cup 54. In the figure, reference numeral 55 denotes a coating solution supply nozzle, for example, a dielectric obtained by dissolving, for example, barium hydroxide monohydrate and isopropoxytitanium in an organic solvent, 2-methoxymethanol, for forming a precursor film of BaTiO3. The coating liquid 5A containing the film forming composition is supplied to the substrate W held on the spin chuck 53.

Further, a filter unit 6 which is an airflow forming means is provided above the casing 50. This filter unit 6 has a filter unit 61 for removing CO2 which is a neutralization processing unit, as shown in FIG. A fan 62 and a particle removing filter 63 as means are stacked in this order from the top.
When the front-side filter unit 61 is described with reference to FIG. 6, the first filter unit 61 includes a sheet body 64 as a filter medium. As the sheet body 64 in this example, a fiber network made of a material such as activated carbon fiber or olefin fiber is immersed in a solution containing Ca (OH) 2 which is an alkali component, and the solution is put in the fine pores of the fiber network. After soaking, a part of the solution in the micropores is repelled by a centrifugal separator to adsorb Ca (OH) 2 molecules on the inner wall surface of the micropores, and then the density of the micropores is increased and It is possible to use a plate formed by pressing in order to align the shapes and regularly arrange the micropores. In the figure, reference numeral 65 denotes a support frame formed so as to surround a side peripheral portion of the sheet body 64, and the sheet body 64 is connected to the crest side and valley side of the sheet body 64 in the housing 50 through the support frame 65. The portions are arranged so as to be directed in the vertical direction. In the figure, reference numeral 66 denotes a slit provided in the sheet body 64 so that the gas flowing into the first filter part 61 passes through the sheet body 64 as described later. It is the gasket attached to 62 side.

  The filter part 63 on the rear stage side is provided to remove particles contained in the gas. For example, a glass fiber is used as a material of the sheet body constituting the filter part 63 and the sheet. Except for the point that Ca (OH) 2 is not adsorbed on the body, the configuration is the same as the first filter unit 61 described above.

  In FIG. 4, reference numeral 67 denotes a ventilation chamber, which is a partitioned space surrounded by the filter unit 6 and the casing 50. The ventilation chamber 67 is connected to, for example, a gas supply duct 69 provided outside the housing 50 through a gas supply hole 68 opened on the rear side wall of the housing 50. The gas supply duct 69 is applied, for example, by coating. The unit 5 extends from the side on the back side to the bottom of the lower application unit 5 and extends out of the housing 20. In FIG. 3, 69a is an opening at the end of the gas supply duct 69. When the fan 62 rotates at a predetermined rotational speed, gas flows into the gas supply duct 69 through the opening 69a. Flows into the filter unit 6 through the ventilation chamber 67. Then, when the gas flowing into the filter unit 6 passes through the filter unit 61 in the previous stage, the CO2 contained in the gas is removed by causing the neutralization reaction as described above with the CaCO3 adsorbed on the sheet body 64. After that, the particles are removed by passing through the filter unit 63 in the subsequent stage and are down-flowed to the entire area of the housing 50, so that the inside of the housing 50 is maintained in a low CO2 concentration atmosphere.

  Next, the heating unit 7 as a heating unit will be described with reference to FIG. In FIG. 7, reference numeral 70 denotes a housing, and reference numeral 71 denotes a transfer port for the substrate W provided on the side wall of the housing 70 facing the transfer path R1. A heat plate support member 72 formed in a cylindrical shape with a bottom is provided inside the housing 70, and a circular heat plate 73, for example, is provided in the heat plate support member 72. In the figure, reference numeral 74 denotes a heater embedded in the hot plate 73. In the figure, reference numeral 75 denotes a rectifying top plate which is an air flow forming means capable of moving up and down, and is formed in a lid shape having a flange portion. In the figure, reference numeral 76 denotes an O-ring. When the substrate W is placed on the hot plate 73, the top plate 75 is lowered and the peripheral edge of the hot plate 75 and the peripheral edge of the hot plate support member 72 are interposed via the O-ring 76. A sealed space is formed around the substrate W by being in close contact with the portion.

  The top plate 75 is provided with a gas supply port 77 over the entire inner circumference of the flange portion, and one end of a gas supply pipe 77 a is connected to the gas supply port 77. The other end of the gas supply pipe 77a is connected to the upstream side of the mist filter 35 of the gas supply pipe 36 described above as shown in FIG. An exhaust port 78 is opened at the lower center of the top plate 75, and one end of an exhaust pipe 78 a is connected to the exhaust port 78. The other end of the exhaust pipe 78a is connected to the downstream side of the pressure pump 31 of the exhaust pipe 29, and the gas from which CO2 has been removed is supplied from the gas supply pipe 32 to the gas supply pipe 77a. While being discharged from 77, suction exhaust is performed from the exhaust port 78, whereby the inside of the housing 70 is maintained in a low CO2 concentration atmosphere. Further, when the substrate W is placed on the hot plate 73 and the sealed space is formed as described above, the substrate W is heated while an air flow from the outer periphery to the center of the substrate W as shown by the arrow in FIG. 7 is formed. It has come to be.

  Although a detailed description of the cooling unit 26 included in the shelf units 24A to 24C is omitted, the cooling unit 26 includes, for example, a casing 70 having a transfer port 71 opened toward the transfer path R1 like the heating unit 7, In the housing 70, for example, an apparatus having a structure including a water-cooling cooling plate is provided. In addition, the delivery unit 25 included in the shelf unit 24A includes a housing 70 similar to the heating unit 7, for example, and is provided with, for example, a circular stage for placing the substrate W inside the housing 70. The substrate W is transferred between the main transfer arm 23 of the substrate W and the transfer means 12.

  Next, the control unit provided in the coating film forming apparatus 1 will be described. This control unit has a program storage unit composed of, for example, a computer, and the program storage unit operates the coating film forming apparatus 1 as will be described later, that is, coating of the substrate W, heat treatment, delivery of the substrate W, Stored is a program made up of, for example, software in which commands are set so as to control the supply of gas in the housing of the unit and processing unit B2. When the program is read by the control unit, the control unit controls the operation of the coating film forming apparatus 1 described later. The program is stored in the program storage unit while being stored in a recording medium such as a hard disk, a compact disk, a magnetic optical disk, or a memory card.

Next, a procedure for forming a BaTiO3 film as a coating film on a substrate W on which a film made of Pt (platinum) is formed as a lower electrode on the surface using the coating film forming apparatus 1 described above will be described with reference to FIG. While explaining. FIG. 8 shows a series of processes until the capacitor structure is formed, and the process surrounded by a dotted line in FIG. 8 shows a process performed by the coating unit 5. The process surrounded by the chain line indicates a process performed by the heating unit 7, and the process indicated by a solid line surrounding the dotted line part and the chain line part indicates a process performed in the coating film forming apparatus 1.
First, for example, before the substrate W is carried into the coating film forming apparatus 1, the pressure pump 31 is operated to form a downflow in the housing 20 as described above, and the top plate in the housing 70 as described above. Gas supply from 75 and suction / exhaust are performed, and each enclosure is kept in a low CO2 concentration atmosphere. Also in the coating unit 5, as described above, the fan 62 is rotated to form a down flow in the housing 50, and the inside of the housing 50 is kept in a low CO2 concentration atmosphere.

  Then, when the carrier C is carried from the outside into the carrier placing part B1 and placed on the carrier station 11, the transfer means 12 carries the substrate W out of the carrier C. Subsequently, after the shutter 22 is opened and the transfer means 12 holding the substrate W enters the processing unit B2 and transfers the substrate W to the transfer unit 25 of the shelf unit 24A, the transfer means 12 is retracted from the processing unit B2. The shutter 22 is closed.

  Thereafter, when the main transport arm 23 receives the substrate W from the delivery unit 25, the main transport arm 23 transports the substrate W into the coating unit 5, delivers it onto the spin chuck 53, and then moves out of the coating unit 5. . Then, a coating film 5A is supplied from the supply nozzle 55 to the central portion of the substrate W while the spin chuck 53 is rotated, and a liquid film is formed on the entire surface of the substrate W by so-called spin coating in which the coating solution 5A is expanded by centrifugal force.

  When the liquid film is formed by the coating solution 5A in this way, the main transport arm 23 enters the coating unit 5 to receive the substrate W from the spin chuck 53, and transports the substrate W into the heating unit 7. When the substrate W is placed on the hot plate 73, as described above, the top plate 75 is lowered to form a sealed space around the substrate W, and the substrate W is, for example, 250 ° C. in a low CO 2 concentration atmosphere while forming an air flow. Is heated for 1 minute to evaporate 2-methoxymethanol as the organic solvent in the dielectric film forming composition 5A to form a precursor film of, for example, an amorphous BaTiO3 film.

  Thus, the substrate W that has been subjected to the heat treatment in the heating unit 7 is transported to the cooling unit 26 by the main transport arm 23, cooled to a predetermined temperature, and then transported to the delivery unit 25. Thereafter, the substrate W is returned to the original carrier C by a procedure reverse to that when the substrate W is transported to the processing section B2 by the delivery means 12.

  The substrate W returned to the carrier C is transported to a firing furnace 8A such as a vertical heat treatment apparatus, and the precursor film is crystallized by firing at, for example, 750 ° C. in the firing furnace 8A. The BaTiO 3 film 81 is formed on the Pt film 82 of the substrate W. Thereafter, a film 83 made of Ni (nickel), for example, as an upper electrode is formed on the BaTiO 3 film by vapor deposition, whereby a capacitor structure is formed on the substrate W as shown in FIG. Note that the upper electrode may be formed using, for example, Al (aluminum) instead of Ni.

  According to the coating film forming apparatus 1, the filter unit F for forming a down flow in the transport path R 1 of the main transport arm 23 that transports the substrate W from the coating unit 5 to the heating unit 7, and the filter unit F Since the bubbling device 3 for neutralizing and removing CO2 in the gas taken in is provided, a downflow is formed by the gas from which CO2 has been removed in the transport path R1, and the transport path R1 is lowered. While maintaining the CO2 concentration atmosphere, the main transfer arm 23 can transfer the substrate W in the transfer path R1. As a result, since CO2 is prevented from being taken into the surface of the coating film formed on the substrate W while the substrate W is transported through the transport path R1, mixing of BaCO3 in the coating film is suppressed. Therefore, the substrate W is baked to form a dielectric thin film having a BaTiO3 type perovskite structure, and the capacitor structure formed using this film can suppress the mixing of BaCO3 in the BaTiO3 film. As a result, the leakage current can be suppressed while achieving a thin BaTiO3 film and ensuring a high dielectric constant.

  Further, according to the coating film forming apparatus 1, the coating unit 5 including the stage 53 and the nozzle 55 for supplying the coating liquid to the substrate W is provided in the casing 50, and a downflow is formed in the casing 50. The filter unit 6 includes a first filter unit 61 that neutralizes and removes CO2 in the gas flowing into the filter unit 6. Accordingly, by forming a downflow due to the gas from which CO2 has been removed in the housing 50, the inside of the housing 50 can be made into a low CO2 concentration atmosphere, and a coating film can be formed on the substrate W in that atmosphere. It is possible to prevent BaCO3 from being mixed into the coating film by incorporating CO2 into the film. As a result, the BaCO3 is prevented from being mixed in the BaTiO3 film formed by being transferred to the heating unit 7 by the main transfer arm 23 after the coating film is formed, subjected to the heat treatment, and further subjected to the baking treatment.

  Further, according to the coating film forming apparatus 1, the heating unit 7, the top plate 75 that forms an air flow in the housing 70 of the heating unit 7, and the CO 2 in the gas taken into the top plate 75 are neutralized and removed. By providing the bubbling device 3, the air flow by the gas from which CO 2 has been removed can be formed in the housing 70, whereby the inside of the housing 70 can be made a low CO 2 concentration atmosphere, and the substrate W can be formed in the low CO 2 concentration atmosphere. Heat treatment which is pretreatment for baking can be performed. Accordingly, since CO2 is prevented from being taken into the coating film formed on the substrate W in this heat treatment, mixing of the BaCO3 in the BaTiO3 film formed after firing is suppressed.

  In the present embodiment, the inside of the coating unit 5 or the heating unit 7 may be an inert gas atmosphere such as N2 gas instead of the atmosphere in which air is neutralized, and the casing which is the main body of the processing unit B2 as described above. By setting the atmosphere in the atmosphere 20 to a low CO2 concentration, there is an effect that normal atmosphere containing a large amount of CO2 flows from the outside of the coating unit 5 and the heating unit 7 and the processing atmosphere is not disturbed. In addition, in the coating unit 5, a technique that can prevent the CO 2 from being entrained in the coating film by devising the coating method even in an air atmosphere, for example, on a substrate in advance, even if the atmosphere is not a low CO 2 concentration atmosphere. We know that the technique of spin coating after applying thinner is effective. As described above, the method of setting the atmosphere within the housing 20 which is the main body of the processing unit B2 to have a low CO2 concentration atmosphere has an advantage that the atmosphere in the coating unit 5 and the heating unit 7 is not disturbed, and particularly contains a lot of thinner. In other words, there is a great concern that CO2 will be taken into the liquid film when moving while cutting the wind with the transfer arm in the state of the liquid film. There is an advantage that the amount of CO2 taken into the liquid film can be reduced.

  Further, in this coating film forming apparatus 1, since the bubbling device 3 is provided outside the processing unit B2 and the air is neutralized, the alkali component in the alkaline solution 33 is reduced and the neutralization ability is lowered. The alkaline solution 33 can be easily replaced. Further, since air is circulated between the coating film forming apparatus 1 and the bubbling apparatus 3, the air supplied into the bubbling apparatus 3 even if new outside air enters the circulation path from the gap of the coating film forming apparatus 1. Since the CO2 concentration in the atmosphere is smaller than the CO2 concentration in the atmosphere, consumption of alkali components can be suppressed.

  Further, when the bubbling device 3 is used as the neutralization processing unit, the first bubbling device 3A and the second bubbling device 3B are used as the bubbling device as shown in FIG. For example, when performing maintenance such as replacement of an alkaline solution for one bubbling device 3A (3B), continuous operation is performed without stopping the supply of neutralized airflow by using the other bubbling device 3B (3A). can do.

  By the way, instead of providing the filter block 6 in the coating unit 5 in the coating film forming apparatus 1 described above, a filter unit similar to the filter unit F provided in the ceiling block 4 is provided, and the filter unit and the gas supply pipe 36 are further provided. When the down flow is formed in the housing 20 by connecting with the side pipe, the gas from which CO2 has been removed from the gas supply pipe 36 flows into the filter unit via the side pipe, and the filter unit The inside of the housing 50 may be kept in a low CO2 concentration atmosphere by downflowing the gas into the housing 50.

  The ceiling block 4 includes, for example, a casing having an opening at the top, and a plurality of filter units configured in the same manner as the filter unit 6 provided in the coating unit 5 are provided in parallel to the casing, Gas outside the processing unit B2 flows into each filter unit, and after the CO2 and particles contained in the gas are removed by the filter unit, the gas is downflowed into the housing 20. Thus, the inside of the housing 20 may be kept in a low CO2 concentration atmosphere.

  Since the solution filled in the container 32 only needs to neutralize CO2 in the gas flowing into the container 32, CaO (calcium oxide) or LiOH (lithium hydroxide) can be used as an alkali component instead of Ca (OH) 2. An aqueous solution containing s may be stored.

  Incidentally, the baking furnace 8A may be connected to the coating film forming apparatus 1. FIG. 11 shows an example of such a coating film forming apparatus. In this coating film forming apparatus T1, the baking furnace 8A is connected to the back side of the processing section B2 of the coating film forming apparatus 1 described above via the interface section B3. The baking part B4 provided with is connected. The processing unit B2 in the coating film forming apparatus T1 is configured in substantially the same manner as the processing unit B2 in the coating film forming apparatus 1 described above, but the shelf unit 24C includes a delivery unit 25. The interface unit B3 includes, for example, a housing 90 having a substantially airtight space inside, and an interface arm 91 for delivering the substrate W from the processing unit B2 to the baking unit B4 is provided in the housing 90. The substrate W is transferred between the interface arm 91 and the transfer unit 25.

  The firing section B4 includes a housing 94 having a substantially airtight space inside. The firing furnace 8A and a loading / unloading mechanism (non-loading / unloading mechanism) for loading / unloading the substrate W into / from the firing furnace 8A. The substrate W is transferred between the interface arm 91 and the loading / unloading mechanism.

  A plurality of filter units F similar to those provided in the processing unit B2, for example, are arranged in parallel on the upper portions of the housings 90 and 94, respectively. In addition, for example, a plurality of exhaust ports (not shown) are opened at intervals at the bottoms of the casings 90 and 94, and exhaust pipes 92 and 95 are connected to the respective exhaust ports. The exhaust pipes 92 and 95 are joined together while extending to the outside of the housings 90 and 94, and the ends of the exhaust pipes 92 and 95 are respectively connected to the downstream side of the pressure pump 31 of the exhaust pipe 29 of the processing section B2. Has been. The gas supply pipe 36 of the bubbling device 3 of the coating film forming apparatus T1 is branched according to the blocks B2, B3, and B4 on the downstream side of the portion where the mist filter 35 is interposed, and the end portion of each gas supply pipe 36 is divided into blocks. When the pressure pump 31 of the bubbling device 3 is operated, the gas in each enclosure is sucked and exhausted from the exhaust port of each block and at the same time through the gas supply pipe 36. A gas from which CO2 has been removed is supplied to the filter unit F of each housing, and the gas is down-flowed into each housing. The gas sucked from the exhaust port of each chassis is bubbled by the bubbling device 3 and then flows again into the filter unit F of each chassis via the gas supply pipe 36 so that each chassis has a low CO2 concentration atmosphere. It is configured.

  In the coating film forming apparatus T1 shown in FIG. 11, the substrate W carried into the carrier platform B1 while being stored in the carrier C from the outside is transported along the same path as the coating film forming apparatus 1 described above. The substrate W is subjected to a coating process and a heating process. When the substrate W is cooled by the cooling unit 26 after the heating process, the substrate W is transferred to the delivery unit 25 of the shelf unit 24C by the main transfer arm 23. Thereafter, the substrate W is transferred to the carry-in / out mechanism of the firing section B4 via the interface arm 61, and then carried into the firing furnace 8A and subjected to a firing process to form a BaTiO3 film. The fired substrate W is transported in the order of the carry-in / out mechanism → interface arm 61 → delivery unit 25 of the shelf unit 24C → main transport arm 23 → delivery unit 25 of the shelf unit 24A → delivery means 12 and is stored in the carrier C. Is done. In such a transfer method using the coating film forming apparatus T1, a low CO2 concentration atmosphere is maintained after the substrate W is heated by the heating unit 7 to form the BaTiO3 film precursor film and before the BaTiO3 film is formed. In this way, since the substrate W is transported, it is possible to more reliably prevent CO2 from being taken into the BaTiO3 film.

In the above-described embodiment, the step of forming a BaTiO3 film as the ABO _X- type perovskite crystal structure film has been shown. As the metal species A of ABO _X- type perovskite, for example, Li (lithium), Na (sodium), Ca ( One or more metals selected from calcium), Sr (strontium), Ba, and La (lanthanum). Examples of the metal species B include Zr (zirconium), Ta (tantalum), Nb (niobium), and Ti. The composition for forming a dielectric film contained in the coating solution 5A may be selected in accordance with the ABO _X- type perovskite crystal structure film containing one or more selected metals. Examples of the composition for forming a dielectric include (i) particles having an ABOx type crystal structure containing a metal species A and a metal species B; ii) at least one component selected from the group consisting of metal alkoxides, metal carboxylates, metal complexes and metal hydroxides containing metal species A and B, and (iii) solvents such as alcohols, esters, ethers, etc. A solution containing at least one of (i) and (ii) and (iii) from among organic solvents can be used.

1 is a perspective view of a coating film forming apparatus used for forming a barium titanate film according to the present invention on a wafer. It is a top view which shows the said coating film formation apparatus. It is an expanded view which shows the process part of the said coating film formation apparatus. It is a vertical side view of the coating unit provided in the coating film forming apparatus. It is explanatory drawing which showed the structure of the filter unit provided in the said application | coating unit. It is a perspective view which shows the structure of the 1st filter part with which the said filter unit was equipped. It is a vertical side view of the heating unit provided in the coating film forming apparatus. It is explanatory drawing which showed the process of forming the capacitor | condenser structure containing the said barium titanate film | membrane in a board | substrate. It is the vertical side view which showed the said capacitor | condenser structure. It is the schematic diagram which showed an example of the other coating film forming apparatus. It is a top view which shows an example of the coating film forming apparatus which connected the baking furnace to the coating film forming apparatus as stated above.

Explanation of symbols

W substrate B2 processing unit 1 coating film forming apparatus 4 ceiling block 5 coating unit 7 heating unit

Claims (19)

A coating film forming apparatus for producing a thin film having a crystal structure of an ABO _X- type perovskite structure obtained by applying a coating solution to a substrate and further baking the coating solution,
A coating unit for coating a substrate with a coating solution containing a composition for forming a dielectric thin film of a thin film having an ABO _X- type perovskite crystal structure;
A heating unit for performing a heat treatment that is a pretreatment for baking the coating film on the substrate;
Substrate transport means for transporting the substrate from the coating unit to the heating unit;
A main body housing in which the coating unit, the heating unit, and the substrate transfer means are disposed;
An airflow forming means for forming an airflow in a transfer region by the substrate transfer means;
An apparatus for forming a coating film, comprising: a neutralization processing unit that neutralizes and removes carbon dioxide in a gas taken into the airflow forming means by an alkali component.   The coating film forming apparatus according to claim 1, wherein the airflow forming unit forms an airflow in the housing for the main body.   The coating film forming apparatus according to claim 1, wherein the airflow forming unit includes a first filter unit for removing particles.   The neutralization processing unit is provided with a container for storing an alkaline solution, provided in a gas supply path for sending gas to the airflow forming means, and bubbling means for supplying and bubbling gas into the alkaline solution. The coating film forming apparatus according to claim 1, wherein the coating film forming apparatus is a film forming apparatus.   The coating film forming apparatus according to claim 1, wherein the neutralization processing unit includes a second filter unit to which an alkali component is attached.   6. A circulation means for circulating the gas supplied from the air flow formation means back to the air flow formation means through the neutralization processing section. The coating film formation apparatus as described in any one. The coating unit is for applying a coating liquid containing a substrate mounting table provided in a casing for the coating unit and a thin film dielectric thin film forming composition having a crystal structure of an ABO _X- type perovskite structure to the substrate. A nozzle, and an airflow forming means for forming an airflow in the casing for the coating unit,
The neutralization process part which neutralizes and removes the carbon dioxide in the gas taken in into the airflow formation means provided in the said application unit by an alkali component is provided. The coating film forming apparatus as described in 2. above. The heating unit is provided in the container, and includes a mounting table on which the substrate coated with the coating liquid is placed, a heating unit that heats the substrate, and an airflow forming unit that forms an airflow in the container. ,
The neutralization processing part which neutralizes and removes the carbon dioxide in the gas taken in into the airflow formation means for a heating unit with an alkali component is provided. Coating film forming device. A coating film forming apparatus for producing a thin film having a crystal structure of an ABO _X- type perovskite structure obtained by applying a coating solution to a substrate and further baking the coating solution,
A substrate mounting table provided in the housing, a nozzle for applying a coating liquid containing a thin film dielectric thin film forming composition having a crystal structure of ABO _X- type perovskite structure to the substrate, and an air flow in the housing An application unit including an airflow forming means for forming
A neutralization treatment section for neutralizing and removing carbon dioxide in the gas taken into the airflow forming means by an alkali component;
A heating unit for performing a heat treatment that is a pretreatment for baking the coating film on the substrate;
And a substrate transfer means for transferring the substrate from the coating unit to the heating unit.   The coating film forming apparatus according to claim 7 or 9, wherein the neutralizing section for the coating unit includes a second filter section to which an alkali component is attached.   The neutralizing section for the coating unit is provided in a gas supply path for sending gas to the airflow forming means for the coating unit, and a bubbling for supplying and bubbling the gas into the alkaline solution. And a coating film forming apparatus according to claim 7 or 9. A coating film forming apparatus for producing a thin film having a crystal structure of an ABO _X- type perovskite structure obtained by applying a coating solution to a substrate and further baking the coating solution,
A coating unit for coating a substrate with a coating solution containing a composition for forming a dielectric thin film of a thin film having an ABO _X- type perovskite crystal structure;
A mounting table that is provided in the container and on which the substrate coated with the coating liquid is placed; a heating unit that heats the substrate; and an airflow forming unit that forms an airflow in the container. A heating unit for performing a heat treatment that is a pretreatment for baking the coating film;
A neutralization treatment section for neutralizing and removing carbon dioxide in the gas taken into the airflow forming means by an alkali component;
And a substrate transfer means for transferring the substrate from the coating unit to the heating unit. The neutralizing section for the heating unit is provided in a gas supply path for sending gas to the airflow forming means for the coating unit, and a bubbling for supplying and bubbling the gas into the alkaline solution. The coating film forming apparatus according to claim 8 or 12, further comprising: means.
The dielectric film forming composition is:
(i) particles having an ABOx type crystal structure containing metal species A and metal species B;
(ii) at least one component selected from the group consisting of metal alkoxides containing metal species A and B, metal carboxylates, metal complexes and metal hydroxides;
(iii) an organic solvent,
The coating film forming apparatus according to claim 1, comprising at least one of (i) and (ii) and (iii). The thin film having a crystal structure of the ABO _X- type perovskite structure is such that the metal species A is one or more metals selected from lithium, sodium, calcium, strontium, barium, and lanthanum, and the metal species B is titanium, zirconium, tantalum, niobium. 15. The coating film forming apparatus according to claim 1, wherein the coating film forming apparatus is a thin film having an ABO _X perovskite crystal structure, which is one or more metals selected from the group consisting of: A method for forming a coating film for producing a thin film having a crystal structure of an ABO _X- type perovskite structure obtained by applying a coating liquid to a substrate and further baking it,
A step of mounting the substrate on the mounting table;
Coating containing a composition for forming a dielectric of a thin film having a crystal structure of ABO _X- type perovskite structure while neutralizing and removing carbon dioxide in the gas with an alkali component and supplying the gas to the substrate on the mounting table And a step of applying a liquid on a substrate on a mounting table. Neutralizing and removing carbon dioxide in the gas with an alkali component, and supplying the gas to the transport area of the substrate;
And a step of transporting the substrate coated with the coating liquid through the transport region to a heating unit for performing a heat treatment that is a pretreatment for baking the coating film. The coating film formation method of description. Transporting the substrate coated with the coating liquid to the heating unit;
The carbon dioxide in the gas is neutralized and removed by an alkali component, and while the gas is supplied into the heating unit, the coating film on the substrate is heated in the heating unit, which is a pretreatment for baking. The method for forming a coating film according to claim 16, further comprising a step of performing. The step of neutralizing and removing carbon dioxide is a step selected from a step of supplying a gas into an alkaline solution in a container and bubbling, and a step of allowing the gas to pass through a filter part to which an alkali component is attached. Item 19. The coating film forming method according to any one of Items 16 to 18.

Images