Patent Application
20050023266
The present invention relates to a heat treatment apparatus and a heat treatment method for carrying out a heat treatment in a magnetic field. More specifically, the invention relates to a heat treatment apparatus and a heat treatment method for applying a heat treatment in a high magnetic field to a finely patterned material or magnetic material, particularly a magnetic material such as an MR film, a GMR film or a TMR film.
A magnetic film, such as a thin film of an Fe—Ni, Pt—Mn or Co—Fe alloy or the like, formed on a substrate by sputtering or the like, which is a magnetic material used for a magnetic head, an MRAM (Magnetic Random Access Memory) which is one of non-volatile memories or the like, can exhibit its magnetic properties by subjecting it to a heat treatment in a high magnetic field.
For this purpose, there is conventionally proposed a heat treatment apparatus in which an electric furnace, an induction heating furnace or the like is disposed to apply a heat treatment in a magnetic field formed with electromagnets or permanent magnets. A schematic configuration of a typical conventional heat treatment apparatus is illustrated in
As shown in
The holder supporting unit 3B is arranged above the vacuum vessel 2, and the holder 3A holding the object to be heat-treated, such as a magnetic material (hereinafter referred to as the “object of treatment”), is charged into the vessel by this supporting unit 3B.
The magnetic field generator 20 is provided with a pair of electromagnets 21 arranged oppositely outside the vacuum vessel 2, and the electromagnet 21 has a magnetic core 22 and a coil 23.
Heater 100 is provided between the outer surface of the vacuum vessel 2 and the end face of the magnetic core 22 of the electromagnet 21. Usually, the heater 100 is spaced apart from the outer surface of the vacuum vessel 2 by a prescribed distance, and comprises electric heater 101 arranged so as to surround the outer periphery of the vacuum vessel 2. The electric heater 101 is formed, for example as shown in
The heat-treated object is taken out of the vacuum vessel 2. Then, a new object of treatment is charged by the supporting unit 3B into the vacuum vessel 2, held by the holder 3A, and subjected to the above-mentioned heat treatment. Subsequently, the heat treatment of other objects of treatment is continued by batch treatment with the same procedure.
In the conventional art, the object of treatment is heat-treated in the heat treatment apparatus 1A usually at about 150° C. to 500° C. In some cases, heat treatment may be carried out at a high temperature of about 500° C. to 800° C. When taking the object of treatment out of the vacuum vessel 2 to the open air, after such a heat treatment in a high-temperature state, deterioration may be caused by oxidation or the like.
It is therefore necessary in the conventional art to retain the object of treatment within the vacuum vessel 2 after the heat treatment until the temperature thereof decreases to a level of about room temperature. This necessarily results in a longer single-batch treatment period. There is available a practice of cooling by providing a water-cooled jacket, but a long period of time of from 3 to 4 hours is generally required for reducing the temperature of the object of treatment to about room temperature after the heat treatment.
Further, in the conventional heat treatment apparatus 1A, as shown in
In the conventional heat treatment apparatus 1A, as described above, since a magnetic material or the like as the object of treatment has a large weight, the upper end of the vacuum vessel 2 has an opening, and the object of treatment is charged into, and discharged from, the vacuum vessel 2 through this opening.
According to the results of studies and experiments carried out by the present inventors, although the heat treatment apparatus 1A having the above-mentioned configuration is configured so as to carry out a heat treatment in a dust-free environment, deposition of dust onto the object of treatment was observed.
Further studies were carried out to solve this problem, and the results revealed the following. The conventional heat treatment apparatus 1A has the supporting unit 3B, and in addition, although not shown in
In order to prevent generation of dust from the holder supporting unit 3B and the conveyor, therefore, it is necessary to extensively make efforts to eliminate dust from the entire apparatus, and this requires a more complicated and larger-scaled apparatus structure. This results in a larger space for installation of the apparatus and in a lower degree of freedom in the apparatus arrangement.
A primary object of the present invention is therefore to provide a heat treatment apparatus and method, which permit reduction of a single-batch treatment period and increase in the throughput of the object of treatment.
Another object of the present invention is to provide a heat treatment apparatus and method, which make it difficult for dust to adhere to the object of treatment.
Still another object of the present invention is to provide a heat treatment apparatus method, which permit reduction of the installation space of the apparatus and improvement of the degree of freedom of apparatus arrangement.
The aforementioned objects of the present invention are achieved by the heat treatment apparatus and method of the invention.
In summary, a first aspect of the present invention provides a heat treatment apparatus comprising a holding unit which holds an object of treatment, a heat treatment vessel which houses the object of treatment held by the holding unit, a heater which heats the object of treatment, and a magnetic field generator which impresses a magnetic field onto the object of treatment, wherein the heat treatment apparatus further comprises:
According to a second aspect of the present invention, there is provided a heat treatment method for heat-treating an object of treatment in a magnetic field by using the above-mentioned heat treatment apparatus, which comprises:
According to one embodiment of the above-mentioned first and second aspect of the present invention, the object of treatment is deteriorated in an open-air atmosphere at a heat treatment temperature, and the treatment chamber is set to contain a non-oxidizing atmosphere.
According to another embodiment of the above-mentioned first and second aspects of the present invention, the non-oxidizing atmosphere in the treatment chamber is a nitrogen gas or an argon gas atmosphere. The atmosphere in the treatment chamber may be in vacuum.
According to still another embodiment of the above-mentioned first and second aspects of the present invention, the treatment chamber is set at a prescribed temperature. In this case, the prescribed temperature of the treatment chamber may be room temperature.
According to a still further embodiment of the above-mentioned first and second aspects of the present invention, the treatment chamber may be arranged above, below, or on one side of the heat treatment vessel.
According to a third aspect of the present invention, there is provided a heat treatment apparatus comprising a holding unit which holds an object of treatment, a heat treatment vessel which houses the object of treatment held by the holding unit, a heater which heats the object of treatment, and a magnetic field generator which impresses a magnetic field on the object of treatment, wherein the heat treatment apparatus further comprises:
According to one embodiment of the above-mentioned third aspect of the present invention, the heat treatment vessel is a vacuum vessel evacuated by closing an opening, and the conveyor is arranged at a position below the opening of the vacuum vessel.
According to another embodiment of the third aspect of the present invention, the conveyor has a movable portion positioned below the object of treatment arranged in the dust-free chamber.
According to still another embodiment of the third aspect of the present invention, the heater and the magnetic field generator are arranged so as to surround the heat treatment vessel.
According to a still further embodiment of the third aspect of the present invention, at least the magnetic field generator is separable from the heat treatment vessel.
According to a fourth aspect of the present invention, there is provided a heat treatment method for heat-treating an object of treatment in a magnetic field by using the above-mentioned heat treatment apparatus, which comprises:
The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:
The heat treatment apparatus and the heat treatment method of the present invention will now be described further in detail with reference to the drawings.
FIGS. 1 to 4 illustrate a schematic overall configuration of one embodiment of the heat treatment apparatus 1 of the invention.
According to this embodiment, the heat treatment apparatus 1 has a vacuum vessel 2 serving as a heat treatment vessel, holding unit 3 which holds an object of treatment in the vacuum vessel 2, and magnetic field generator 20 arranged outside the vacuum vessel 2, as in the conventional heat treatment apparatus 1A. The holding unit 3 has a holder 3A which holds the object of treatment, and a holder supporting unit 3B which supports this holder 3A.
As is understood well by referring also to
In this embodiment, the upper end of the vessel is closely sealed by attaching a lid member 4 of the holder supporting unit 3B to the opening at the upper end of the vessel. An annular shoulder 2C formed between the vessel main body 2A and the vessel attachment section 2B of the vacuum vessel 2 is mounted on a vessel placing section 5a of the lower structure 5, and the vacuum vessel 2 is held there.
The vacuum vessel 2 should preferably be made of ceramics such as quartz glass for its stability during rapid cooling. In this embodiment, as described later in detail, heating in vacuum by heater 30 is accomplished mainly by radiation heat. The quartz glass should therefore preferably be an optically transparent one. The vacuum vessel 2, which may have a thickness within a range of from 2 to 6 mm, has a thickness of 3 mm in this embodiment.
The holder 3A comprises about 30 trays 6 for mounting a substrate having a diameter of about 100 to 200 mm and having, for example an Fe-Ni alloy film formed by sputtering. The trays 6 are supported by a supporting shaft 7, the upper end of which is suspension-supported by the holder supporting unit 3B.
The holder supporting unit 3B should preferably rotatably hold the holder 3A so that the direction of the object of treatment held by the holder 3A can be changed relative to the magnetic field direction. In this embodiment, therefore, a driving motor 8 is attached to the holder supporting unit 3B so that the supporting shaft 7 of the holder 3A can be rotation-driven.
The vacuum vessel 2 can be maintained in a prescribed vacuum state by evacuating the interior of the vacuum vessel 2 by means of a vacuum pump (not shown) communicating with the upper end of the vacuum vessel, after attaching the holder supporting unit 3B to the upper end of the vacuum vessel. For example, when the object of treatment is a magnetic metal thin film, the object of treatment should preferably be heat-treated in vacuum, or more specifically, in a vacuum of up to 1 Pa to avoid oxidation of the metal thin film. Preferably, the interior of the vacuum vessel 2 is filled with a non-oxidizing gas, such as nitrogen gas or argon gas, to achieve a non-oxidizing gas atmosphere in the vacuum vessel 2.
The holder supporting unit 3B is arranged at the upper end of the vessel. The holder 3A can be moved, together with the holder supporting unit 3B, by a lift mechanism 10 (see
The magnetic field generator 20 is provided with a pair of electromagnets 21 oppositely arranged, and each electromagnet 21 has, as shown in
As is understood by referring also to
More specifically, the heater 30 has an electrically insulating inner cylinder 32 arranged so as to surround the outer periphery of the vacuum vessel main body 2A, and a water-cooled jacket forming a fluid cooling section 33 spaced apart from the inner cylinder 32 by a prescribed distance. The inner cylinder 32 can be manufactured from a quartz glass tube having a thickness of from 2 to 6 mm. A gap (G1) of from 2 to 4 mm is provided between the inner cylinder 32 and the outer periphery of the vacuum vessel main body 2A. In this embodiment, in which the vacuum vessel main body 2A has an outside diameter (DI) of 240 mm, the inner cylinder 32 has an inside diameter (D2) of 245 mm. The inner cylinder 32 has an axial length (L1) of 450 mm.
The water-cooled jacket 33 is a cylinder having a dual tube structure with an inner wall 34 and an outer wall 35, and the upper end and the lower end thereof are closed by an upper wall 36 and a lower wall 37, respectively. In this embodiment, as shown in
As shown in
The water-cooled jacket 33 is made of a material having a high thermal conductivity, such as a metal. In this embodiment, the inner wall 34, the outer wall 35, the upper wall 36 and the lower wall 37 are manufactured with stainless steel plates having a thickness of 3 mm. A gap (G2) of 8 to 13 mm for arranging the heater 31 is provided between the inner cylinder 32 and the inner surface of the inner wall 34 of the water-cooled jacket 33 surrounding the inner cylinder 32. In this embodiment, in which the inner cylinder 32 has an outside diameter (D3) of 253 mm, the water-cooled jacket 33 has an inside diameter (D4) of 272 mm. The inner wall 34 of the water-cooled jacket 33 has an axial length sufficient to completely cover the heater 30.
The heater 30 will be described further. According to the present invention, the heater 30 has the electric heater 31 as described above, and is spirally wound around the outer periphery of the inner cylinder 32.
According to the present invention, the electric heater 31 is formed by covering a resistance-heating wire 31A with an electrically insulating tube 31B as shown in
The resistance-heating wire 31A, being placed in the magnetic field produced by the magnetic field generator 20 as described above, is subjected to application of a force resulting from the interaction with the magnetic field caused by the current for heating, leading to contact between resistance wires. Therefore, the resistance-heating wire 31A should preferably be electrically insulated with the insulating tube 31B.
In order to reduce the force resulting from the interaction, it is desirable to adopt the so-called non-inducing winding in which the flow of current of the resistance-heating wire 31A is arranged so as to cancel the resultant magnetic field.
More specifically, as shown in
To ensure stable cancellation of such a force, the heating current should preferably be a direct current. Control means for controlling the temperature is usually provided for the heater 30 to control the energizing of the heater 31.
Usually, the heat treatment temperature is within a range of about 150° C. to 500° C. When heat-treating a magnetic film having a high ordering temperature of the structure of film, however, the temperature should be within a range of about 500° C. to 800° C. When heat-treating a magnetic film for an MR device, the cooling rate should preferably be at least 5° C./minute, or particularly, within a range of 15° C./minute to 200° C./minute.
No heat insulating material should preferably be provided around the heater 31. In this embodiment, however, as the water-cooled jacket 33 is made of stainless steel, an alumina sheet 40 (
The aforementioned heat treatment apparatus 1 further comprises a power source for the magnetic field generator 20, a magnetic field measuring controller, a control unit for the vacuum pump for evacuating the vacuum vessel 2, and a mechanism for controlling the operating sequence of the overall apparatus. These components may be ones well known by those skilled in the art. Detailed description thereof is therefore omitted here.
While the above description has explained the magnetic field generator 20 as an electromagnet 21, it may be a superconducting electromagnet. The heater 30 has been explained above as being arranged outside the vacuum vessel 2, but as required, it may be installed in the vacuum vessel 2.
The configuration displaying important features of the present invention will now be described.
According to the present invention, as is clear from FIGS. 1 to 4, a treatment chamber 50 capable of being hermetically closed, confining a space communicating with the vacuum vessel 2, is provided in the heat treatment apparatus 1.
In this embodiment, the treatment chamber 50 has a cubic box shape, and is installed above the lower structure 5 housing the vacuum vessel 2, the heater 30, the magnetic field generator 20 and the like. Therefore, the vessel attachment section 2B of the vacuum vessel 2 projects from below into the treatment chamber 50, and the vessel attachment section 2B opens into the treatment chamber 50.
According to this embodiment, the vessel attachment section 2B of the vacuum vessel 2, the holder supporting unit 3B, and the lift mechanism 10 serving as the conveyor are arranged in the treatment chamber 50.
Also in this embodiment, an intermediate chamber 70 is arranged adjacent to the treatment chamber 50. The intermediate chamber 70 is a space capable of being hermetically closed for charging or discharging the object of treatment between the treatment chamber 50 and outside. The intermediate chamber 70 shields the outside space and the treatment chamber 50 from each other, and can maintain an atmosphere in the treatment chamber 50 on a constant level without being affected by the outside, preferably by achieving a vacuum atmosphere.
Gate valves 71 and 72, capable of being opened and closed, are arranged, respectively, on a partition wall between the treatment chamber 50 and the intermediate chamber 70, and on a partition wall between the intermediate chamber 70 and the outside. A rotation-driven index table 73 is arranged in the intermediate chamber 70, and a cassette 74 containing the object of treatment can be positioned, in this embodiment, at any of four positions on the circumference. The index table 73 is vertically movable within the intermediate chamber 70 by means of a cassette elevator 75 comprising an oil hydraulic cylinder.
Handling means, e.g., a handling robot 51 is installed in the treatment chamber 50. By opening the gate valve 71, the handling robot 51 removes the objects of treatment from the cassette 74 set on the index table 73 one by one in cooperation with the cassette elevator 75 to transfer the same to the tray 6 of the holder 3A supported by the holder supporting unit 3B. Since the handling robot 51 performing such operations is well known by those skilled in the art, a detailed description thereof is omitted here.
According to this embodiment, as shown in
In this embodiment, the running device 52 comprises, as most typically represented in
In this embodiment, the lift mechanism 10 comprises a frame structure 61, which is secured to the cart 55 and extends upward, and a support 62 for supporting the holder supporting unit 3B on the frame structure 61.
The support 62 has an end fixed to the holder supporting unit 3B and the other end vertically movably attached to a guide rod 63 installed on the frame structure 61 via a bearing member 64. A parent screw shaft 65 rotation-driven by a driver is installed on the frame structure 61, and screw-engaged with a nut 66 fixed to the support 61. Therefore, the support 62 can be vertically moved relative to the frame structure 61 by driving the parent screw shaft 65 with the driver.
In the above-mentioned configuration, by driving the cart 55 by the driver along the guide stretch 53, the holder supporting unit 3B and the holder 3A can be moved between the object charging position (A) and the object receiving position (B) as an integral entity. At the object charging position (A), it is possible to insert the holder supporting unit 3B and the holder 3A into the vacuum vessel, or remove the same from the vacuum vessel 2 to outside by driving the lift mechanism 10.
A cassette charging gate valve 72 for installing the cassette in the intermediate chamber 70 is provided in the intermediate chamber 70 as described above. Therefore, an operator can install a cassette containing a prescribed number of objects of treatment on the index table 73 in the intermediate chamber 70 by opening this cassette charging gate valve 72.
Operation of the heat treatment apparatus having the above-mentioned configuration of this embodiment will now be described.
First, the holder supporting unit 3B and the holder 3A arranged at the charging position (A) are removed upwardly from the vacuum vessel 2 by driving the lift mechanism 10. Then, by causing the cart 55 to run by driving the driver, the holder supporting unit 3B and the holder 3A are stopped at the object receiving position (B) as an integral entity.
By opening the gate valve 71 provided on the partition wall between the treatment chamber 50 and the intermediate chamber 70, the handling robot 51 removes the objects of treatment one by one from the cassette 74 set on the index table 73, and transfers the same to the holder 3A.
Upon completion of transfer of the objects of treatment to the holder 3A, the gate valve 71 is closed, and the cart 55 is driven to cause the holder supporting unit 3B and the holder 3A to run to the object charging position (A) and to stop there.
Then, the holder supporting unit 3B and the holder 3A are inserted into the vacuum vessel 2 by driving the lift mechanism 10. The opening of the vacuum vessel 2 is closed by a sealing lid 4 provided on the holder supporting unit 3B.
Subsequently, the interior of the vacuum vessel 2 is evacuated to reduce pressure, and the interior of the vacuum vessel 2 is set to contain a non-oxidizing gas atmosphere in the same procedure as in the above-mentioned conventional art. Then, a heat treatment is applied to the object of treatment supported by the holder.
According to the present invention, on the other hand, the treatment chamber 50 becomes hermetically closed while the opening of the vacuum vessel 2 is closed, and is set to contain a prescribed atmosphere.
More specifically, in this embodiment, since the object of treatment is a magnetic material, such as an MR film or a GMR film, which is deteriorated by an open-air atmosphere at a treating temperature higher than room temperature, the interior of the treatment chamber 50 is set to contain a non-oxidizing atmosphere, such as nitrogen or argon. Therefore, the interior of the treatment chamber 50, after evacuation to below 1 Pa, is filled with nitrogen gas in this embodiment to achieve a nitrogen gas atmosphere at room temperature under a pressure of 1 atm (0.1 MPa). Alternatively, the interior of the treatment chamber 50 may be left in vacuum state. As the condition of atmosphere in the treatment chamber 50, a desired gas, a desired chamber temperature, a desired pressure and the like may be selected as required.
After achieving the non-oxidizing atmosphere state in the treatment chamber 50, the vacuum state in the vacuum vessel 2 is released by injecting nitrogen gas into the vacuum vessel 2 via a valve 2a, and the holder supporting unit 3B and the holder 3A are lifted up from the opening of the vacuum vessel by driving the lift mechanism 10.
The interior of the treatment chamber 50 is kept in a non-oxidizing atmosphere state at room temperature. As a result, the heat-treated object of treatment is rapidly cooled without suffering from deterioration.
According to the result of an experiment carried out by the present inventors, it took a time of about 25 minutes for an object of treatment heated to about 500° C. to 800° C. to be cooled to 50° C. As compared with the conventionally required time of 3 to 4 hours, the cooling period could be remarkably reduced. Further, physical properties of the object of treatment showed no change.
Thereafter, as described above, the cart 55 is caused to run by driving it with the driver. The holder supporting unit 3B and the holder 3A are moved as an integral entity to the object receiving position (B). The treated objects supported by the holder 3A are transferred to the intermediate chamber 70 by means of the handling robot 51. Then, the objects of treatment housed in the cassette 74 to be treated next, set in the intermediate chamber 70, are transferred to the holder 3A.
Subsequently, treatment operations for the next batch are started in the above-mentioned procedure.
According to the present invention, as described above, it is possible to greatly curtail the treatment time for a batch.
Furthermore, in order to reduce the cooling time and remarkably reduce the treatment time for a batch, the atmosphere gas in the treatment chamber 50 can be circulated in the treatment chamber 50. It is also possible to draw out the atmosphere gas to outside the treatment chamber 50 via a duct (not shown), cool the gas, and then reflux the gas again into the treatment chamber 50 through a filter F (
In the first embodiment, the description has been based on a configuration in which the treatment chamber 50 is located above the vacuum vessel 2, and the object of treatment travels between the heat treatment vessel 2 and the treatment chamber 50 by moving the same vertically via the holder supporting unit 3B and the holder 3A by the conveyor 10. In the second embodiment, in contrast, as shown in
Also in this embodiment, the same functional effects as in the first embodiment are available, and furthermore, in this embodiment, since the conveyor 10 and the like for moving the object of treatment are arranged below the vacuum vessel 2, there is available an advantage that dust is hard to adhere to the object of treatment. Particularly, the configuration in which the treatment chamber 50 is a dust-free chamber will be described further in detail in a fourth embodiment.
Unlike the first and the second embodiments, the third embodiment has a configuration in which, as shown in
In this embodiment, the object of treatment travels between the heat treatment vessel 2 and the treatment chamber 50 through horizontal displacement via the holder supporting unit 3B and the holder 3A by the conveyor 10.
Also in this embodiment, there are available the same functional effects as in the first embodiment.
In this embodiment, a heat treatment apparatus and a heat treatment method have a configuration, such that the treatment chamber 50 serving as a dust-free chamber is located below the vacuum vessel 2, as described in the second embodiment, to make it difficult for dust to adhere to the object of treatment. The heat treatment apparatus and the heat treatment method of this embodiment will now be described further in detail with reference to the drawings.
FIGS. 12 to 14 illustrate a schematic overall configuration of the heat treatment apparatus 1 of this embodiment.
According to this embodiment, the heat treatment apparatus 1 has a vacuum vessel 2 serving as a heat treatment vessel, holding unit 3 which holds an object of treatment in the vacuum vessel 2, and magnetic field generator 20 arranged outside the vacuum vessel 2, as in the conventional treatment apparatus 1A. The holding unit 3 has a holder 3A which holds the object of treatment, and a holder supporting unit 3B which supports this holder 3A. In the heat treatment apparatus 1 of this embodiment, an opening of the vacuum vessel 2 is formed at the lower end thereof. The holder supporting unit 3B is therefore arranged below the vacuum vessel 2.
In this embodiment, more particularly, the vacuum vessel 2 is a stepped cylindrical container comprising a vessel main body 2A having a smaller diameter, and a vessel attachment section 2B having a larger diameter formed integrally with the lower portion of the vessel main body 2A. In this embodiment, the upper end of the vessel main body 2A is connected to a conduit for introducing a non-oxidizing gas via a valve 2a. However, the upper end of the vessel main body 2A is substantially a closed end, and the lower end of the vessel attachment section 2B is open.
In this embodiment, the lower end of the vessel is closely sealed by attaching a lid member 4 of the holder supporting unit 3B to the opening at the lower end of the vessel. Further, an annular shoulder 2C formed between the vessel main body 2A and the vessel attachment section 2B of the vacuum vessel 2 is mounted on a vessel placing section 5a of a dust-free chamber 50 forming a lower structure 5, and the vacuum vessel 2 is held there.
The vacuum vessel 2 should preferably be made of ceramic, such as quartz glass, for its stability during rapid cooling. In this embodiment, as described later in detail, heating in vacuum by heater 30 is accomplished mainly by radiation heat as in the preceding embodiment. The quartz glass should therefore preferably be an optically transparent one. The vacuum vessel 2, which may have a thickness within a range of about 2 to 6 mm, has a thickness of 3 mm in this embodiment.
The holder 3A comprises about 30 trays 6 for mounting a substrate having a diameter of about 100 to 200 mm and having, for example, an Fe-Ni alloy film formed by sputtering. The trays 6 are supported by a supporting shaft body 7, the lower end of which is connected to, and supported by, the holder supporting unit 3B.
The holder supporting unit 3B should preferably rotatably hold the holder 3A, so that the direction of the object of treatment held by the holder 3A can be changed relative to the magnetic field direction. In this embodiment, therefore, a driving motor 8 is attached to the holder supporting unit 3B, so that the supporting shaft body 7 of the holder 3A can be rotation-driven.
The vacuum vessel 2 can be maintained in a prescribed vacuum state by evacuating the interior of the vacuum vessel 2 by a vacuum pump P (see
As is well understood by referring to
The magnetic field generator 20 is provided with a pair of electromagnets 21 oppositely arranged, and each electromagnet 21 has, as showin in
This embodiment has substantially the same configuration as in the first embodiment, and as is understood by referring also to
More specifically, the heater 30 has an electrically insulating inner cylinder 32 arranged so as to surround the outer periphery of the vacuum vessel main body 2A, and a water-cooled jacket forming a fluid cooling section 33, spaced apart from the inner cylinder 32 by a prescribed distance. The inner cylinder 32 can be manufactured from a quartz glass tube having a thickness of about 2 to 6 mm. A gap (G1) of from 2 to 4 mm is provided between the inner cylinder 32 and the outer periphery of the vacuum vessel main body 2A. In this embodiment, in which the vacuum vessel main body 2A has an outside diameter (DI) of 240 mm, the inner cylinder 32 has an inside diameter (D2) of 245 mm. The inner cylinder 32 has an axial length (L1) of 450 mm.
The water-cooled jacket 33 is a cylinder having a dual tube structure with an inner wall 34 and an outer wall 35, and the upper end and the lower end thereof are closed by an upper wall 36 and a lower wall 37, respectively. In this embodiment, as shown in
A water-cooled jacket having the same configuration as that in the first embodiment may be used as the water-cooled jacket 33, and as shown in
The water-cooled jacket 33 is made of a material having a high thermal conductivity, such as a metal. In this embodiment, the inner wall 34, the outer wall 35, the upper wall 36 and the lower wall 37 are manufactured with stainless steel plates having a thickness of 3 mm. A gasp (G2) of about 8 to 13 mm for arranging the heater 31 is provided between the inner cylinder 32 and the inner surface of the inner wall 34 of the water-cooled jacket 33 surrounding the inner cylinder 32d. In this embodiment, in which the inner cylinder 32 has an outside diameter (D3) of 253 mm, the water-cooled jacket 33 has an inside diameter (D4) of 272 mm. The inner wall 34 of the water-cooled jacket 33 has an axial length sufficient to completely cover the heater 30.
The heater 30 will be described further. According to the present invention, the heater 30 has the electric heater 31 as described above, and is spirally wound around the outer periphery of the inner cylinder 32.
According to the present invention, the electric heater 31 is formed by covering a resistance-heating wire 31A with an electrically insulating tube 31B as shown in
The resistance-heating wire 31A, being placed in the magnetic field produced by the magnetic field generator 20 as described above, is subjected to application of a force resulting from the interaction with the magnetic field caused by the current for heating, leading to contact between resistance wires. Therefore, the resistance-heating wire 31A should preferably be electrically insulated with the insulating tube 31B.
In order to reduce the force resulting from the interaction, it is desirable to adopt the so-called non-inducing winding in which the flow of the current of the resistance-heating wire 31A is arranged so as to cancel the resultant magnetic field.
More specifically, as shown in
To ensure stable cancellation of such a force, the heating current should preferably be a direct current. A control for controlling the temperature is usually provided for the heater 30 to control the energizing of the heater 31.
Usually, the heat treatment temperature is within a range of about 150° C. to 500° C. When heat-treating a magnetic film having a high ordering temperature of the structure of film, however, the temperature should be within a range of about 500° C. to 800° C. When heat-treating a magnetic film for an MR device, the cooling rate should preferably be at least 5° C./minute, or preferably, within a range of about 15° C./minute to 200° C./minute.
No heat insulating material should preferably be provided around the heater 31. In this embodiment, however, as the water-cooled jacket 33 is made of stainless steel, an alumina sheet 40 (
The aforementioned heat treatment apparatus 1 further comprises a power source for the magnetic field generator 20, a magnetic field measuring controller, a control unit for the vacuum pump for evacuating the vacuum vessel 2, and a mechanism for controlling the operating sequence of the overall apparatus. These components may be ones well known by those skilled in the art. Detailed description thereof is therefore omitted here.
While the above description has explained the magnetic field generator 20 as an electromagnet 21, it may be a superconducting electromagnet. The heater 30 has been explained above as being arranged outside the vacuum vessel 2, but as required, it may be installed in the vacuum vessel 2.
The configuration displaying important features of the present invention will now be described.
According to the present invention, the dust-free chamber 50 capable of being hermetically closed, confining a dust-free space communicating with the lower opening of the vacuum vessel 2, which serves also as a treatment chamber, is provided in the heat treatment apparatus 1. In this embodiment, the electromagnet 21 and the like arranged to surround the vacuum vessel 2 high in weight are not installed on the dust-free chamber 50, but attached to a base structure 5 installed to surround the dust-free chamber 50.
In this embodiment, the dust-free chamber 50 has a cubic box shape, and is installed below the vacuum vessel 2, the heater 30, the magnetic field generator 20 and the like. Therefore, the vessel attachment section 2B of the vacuum vessel 2 projects downward into the dust-free chamber 50, and the opening of the vessel attachment section 2B opens into the dust-free chamber 50.
According to this embodiment, the vessel attachment section 2B of the vacuum vessel 2, the holder supporting unit 3B, and the lift mechanism 10 serving as the conveyor are arranged in the dust-free chamber 50.
Also in this embodiment, an intermediate chamber 70 is arranged adjacent to the dust-free chamber 50. The intermediate chamber 70 is a space capable of being hermetically closed for charging or discharging the object of treatment between the dust-free chamber 50 and outside. The intermediate chamber 70 shields the outside space and the dust-free chamber 50 from each other, and can maintain an atmosphere in the dust-free chamber 50 on a constant level without being affected by outside, preferably by achieving a vacuum atmosphere.
Gate valves 71 and 72, capable of being opened and closed are arranged, respectively, on a partition wall between the dust-free chamber 50 and the intermediate chamber 70, and on a partition wall between the intermediate chamber 70 and the outside. A rotation-driven index table 73 is arranged in the intermediate chamber 70, and a cassette 74 containing the object of treatment can be positioned, in this embodiment, at any of four positions on the circumference. The index table 73 is vertically movable within the intermediate chamber 70 by means of a cassette elevator 75 comprising an oil hydraulic cylinder.
Handling means, e.g., a handling robot 51 is installed in the dust-free chamber 50. By opening the gate valve 71, the handling robot 51 removes the objects of treatment from the cassette 74 set on the index table 73 one by one in cooperation with the cassette elevator 75 to transfer the same to the tray 6 of the holder 3A supported by the holder supporting unit 3B. Since the handling robot 51 performing such operations is well known by those skilled in the art, a detailed description thereof is omitted here.
In this embodiment, as will be understood more clearly by referring to FIGS. 12 to 14, the lift mechanism 10 comprises a frame structure 61, which is secured to the bottom wall of the dust-free chamber 50 and extends upward, and support 62 for supporting the holder supporting unit 3B on the frame structure 61.
The support 62 has an end fixed to the holder supporting unit 3B and the other end vertically movably attached to a guide rod 63 installed on the frame structure 61 via a bearing member 64. A parent screw shaft 65 rotation-driven by driver is installed on the frame structure 61, and screw-engaged with a nut 66 fixed to the support 62. Therefore, the support 62 can be vertically moved relative to the frame structure 61 by driving the parent screw shaft 65 with a driver.
In the above-mentioned configuration, it is possible to insert the holder supporting unit 3B and the holder 3A into the vacuum vessel 2, or remove the same from the vacuum vessel 2 to outside by driving the lift mechanism 10.
A cassette charging gate valve 72 for installing the cassette in the intermediate chamber 70 is provided in the intermediate chamber 70 as described above. Therefore, an operator can install a cassette containing a prescribed number of objects of treatment on the index table 73 in the intermediate chamber 70 by opening this cassette charging gate valve 72.
Operation of the heat treatment apparatus having the above-mentioned configuration of this embodiment will now be described.
First, the holder supporting unit 3B and the holder 3A are moved downward from the interior of the vacuum vessel 2 by driving the lift mechanism 10 to expose the same outside the vacuum vessel 2.
By opening the gate valve 71 provided on the partition wall between the dust-free chamber 50 and the intermediate chamber 70, the handling robot 51 removes the objects of treatment one by one from the cassette 74 set on the index table 73, and transfers the same to the holder 3A.
Upon completion of transfer of the objects of treatment to the holder 3A, the gate valve 71 is closed.
Then, the holder supporting unit 3B and the holder 3A are inserted from below into the vacuum vessel 2 above by driving the lift mechanism 10. The opening of the vacuum vessel 2 is closed by a sealing lid 4 provided on the holder supporting unit 3B.
Subsequently, the interior of the vacuum vessel 2 is evacuated to reduce pressure, and the interior of the vacuum vessel 2 is set to contain a non-oxidizing gas atmosphere in the same procedure as in the above-mentioned conventional art. Then, a heat treatment is applied to the object of treatment supported by the holder 3A.
According to this embodiment, on the other hand, the dust-free chamber 50, serving also as the treatment chamber described in the preceding embodiment, becomes hermetically closed, while the opening of the vacuum vessel 2 is closed, into a vacuum state. It is set to contain a prescribed atmosphere as required.
More specifically, in this embodiment, since the object of treatment is a magnetic material, such as an MR film or a GMR film, which is deteriorated by an open-air atmosphere at a treating temperature higher than room temperature, the interior of the dust-free chamber 50 is set to contain a non-oxidizing atmosphere, such as nitrogen or argon. Therefore, the interior of the dust-free chamber 50, after evacuation to below 1 Pa, is filled with nitrogen gas in this embodiment to achieve a nitrogen gas atmosphere at room temperature under a pressure of 1 atm (0.1 MPa). Alternatively, the interior of the dust-free chamber 50 may be left in the vacuum state. As the condition of atmosphere in the dust-free chamber 50, a desired gas, a desired chamber temperature, a desired pressure, and the like may be selected as required.
After achieving the non-oxidizing atmosphere state in the dust-free chamber 50, the vacuum state in the vacuum vessel 2 is released by injecting nitrogen gas into the vacuum vessel 2 via the valve 2a, and the holder supporting unit 3B and the holder 3A are lowered from the lower-end opening of the vacuum vessel by driving the lift mechanism 10.
The interior of the dust-free chamber 50 is kept in a non-oxidizing atmosphere state at room temperature, thus permitting rapid cooling the heat-treated object of treatment without suffering from deterioration.
Thereafter, the treated objects supported by the holder 3A are transferred to the intermediate chamber 70 by means of the handling robot 51. Then, the objects of treatment housed in the cassette to be treated next, set in the intermediate chamber 70, are transferred to the holder 3A.
Subsequently, treatment operation for the next batch is started in the above-mentioned procedure.
According to this embodiment, as described above, the dust-free chamber 50 is provided below the heat treatment vessel, such as the vacuum vessel 2. In addition, at least the movable portion of the conveyor 10 for moving the object of treatment is arranged below the vacuum vessel 2, or more preferably below the object of treatment. Therefore, the movable portion of the conveyor 10 which is a source of dust, can be arranged below the object of treatment, thus permitting a remarkable decrease in adhesion of dust to the object of treatment as compared with the conventional apparatus.
In this configuration, the movable portion of the conveyor 10 which is a source of dust, is arranged below the vacuum vessel 2, or more particularly below the object of treatment. This leads to a higher degree of freedom for the arrangement of the conveyor 10 and the like, thereby permitting setting the same at an arbitrary position in the heat treatment apparatus 1, and reduction of size. It is therefore possible to reduce the installation space of the entire heat treatment apparatus and to improve the degree of freedom of the apparatus layout.
Furthermore, in order to reduce the cooling time and remarkably reduce the treatment time for a batch, the atmosphere gas in the dust-free chamber 50 can be circulated in the dust-free chamber 50. It is also possible to draw out the atmosphere gas to outside the dust-free chamber 50 via a duct, cool the gas, and then reflux the gas again into the dust-free chamber 50 through a filter to avoid mixing of dust. In all cases, direct blowing of the atmosphere gas onto the object of treatment permits further acceleration of the cooling rate.
In the above-mentioned embodiment, the electromagnet 21, the heater 30, the water-cooled jacket 33 and the like, which are disposed around the vacuum vessel 2, are attached to the base structure 5 installed around the dust-free chamber 50. Therefore, by adopting a divisible structure at least for the electromagnet 21, or preferably, the heater 30, the fluid cooling section 33, and the like, it is possible to cause divisional displacement of the electromagnet 21, the heater 30, the water-cooled jacket 33 and the like after the heat-treating step, as shown by the dash-dotted line in
According to one embodiment of the present invention, as described above, the heat treatment apparatus comprises: a treatment chamber, arranged adjacent to the heat treatment vessel, for which an internal space can be set to contain a prescribed atmosphere; and a conveyor, which causes the object of treatment to move between the heat treatment vessel and the treatment chamber. It is possible to convey the heat-treated object of treatment to the treatment chamber set to contain a prescribed atmosphere, and rapidly cool the object. It is therefore possible to reduce the treatment period for one batch, and increase the throughput of objects of treatment.
According to another embodiment of the present invention, the heat treatment apparatus comprises: a dust-free chamber, arranged below the heat treatment vessel, in which an opening formed at the lower end of the heat treatment vessel opens; and a conveyor, arranged in the dust-free chamber, which acts on the holding unit, which holds the object of treatment, to cause the object of treatment to move between the heat treatment vessel and the dust-free chamber. It is possible to charge the object of treatment into the heat treatment vessel from below to carry out a heat treatment in a magnetic field, and to remove the heat-treated object of treatment from the heat treatment vessel by conveying the same downward into the dust-free chamber. There are therefore available the following advantages:
It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2002-48629 | Feb 2002 | JP | national |
| 2002-48634 | Feb 2002 | JP | national |
This application is a continuation of International Application No. PCT/JP03/01950, filed Feb. 21, 2003, the disclosure of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP03/01950 | Feb 2003 | US |
| Child | 10924537 | Aug 2004 | US |
