JP5768974B2 - Roller hearth kiln and workpiece heat treatment method using the same - Google Patents

Description

  The present invention relates to a roller hearth kiln and a heat treatment method suitable for heat treatment under conditions that require high cleanliness of a class 10 level.

  In recent years, various low-temperature polysilicon TFT manufacturing techniques for forming a silicon polycrystalline transistor on a glass substrate have been developed to cope with the increase in the size of display devices such as organic EL, light-emitting diodes, and plasma displays (for example, patent documents). 1).

  The annealing process in the low temperature polysilicon TFT manufacturing process is an important process that directly affects the transistor characteristics. In order to achieve desirable transistor characteristics, it is required to keep the cleanliness in the heating furnace at a class 10 level. For this reason, a batch-type muffle furnace is generally used in the annealing process in the low-temperature polysilicon TFT manufacturing process.

  On the other hand, from the viewpoint of further enlargement of the display device and production efficiency, it is desired to use a roller hearth kiln that is superior in mass productivity as a heating furnace in the annealing process than the batch type muffle furnace.

  A roller hearth kiln is a method of heating a workpiece by a heater provided in the furnace while inserting the roller into a plurality of insertion holes provided through the side wall of the furnace and rotating the roller to convey the workpiece in the furnace. In conventional roller hearth kilns where gas flows in and out from the gap provided between the insertion hole and the roller, heat-insulating material, and dust generated during conveyance of the roller and workpiece, clean inside the heating furnace There is a problem that it is difficult to keep the degree (US Federal Standard 209D) high at the class 10 level.

JP-A-10-104659

  The object of the present invention is to solve the above-mentioned problems and to provide a technique relating to a roller hearth kiln that can keep the cleanliness in the heating furnace high to a class 10 level. The “cleanness” of the present invention is based on the US Federal Standard 209D method, and represents the number of particles in the legislature feet with reference to particles of 0.5 μm or more.

The roller hearth kiln according to the present invention, which has been made to solve the above-mentioned problems, is used for transferring a work in a furnace space in which a ceiling part, a floor part, and left and right side wall parts are constituted by a heat insulating wall filled with a heat insulating material in a metal case. a body portion having a low dust generation roller has an outer shell that covers the entire body portion, a b Ra passing through the roller through hole formed in the right and left side wall portions of the body portion, provided on the outer shell It is supported by a low dust generation roller driving unit composed of a low dust generation bearing, a pillow bearing and a magnetic seal rotation mechanism , and a low dust generation heater is provided in the furnace space. .

  The invention according to claim 2 is the roller hearth kiln according to claim 1, wherein the metal case is provided with a pipe serving as an atmosphere discharge path from the inside to the outside of the furnace, and the inside of the metal case has a sealed structure. It is a feature.

  The invention according to claim 3 is the roller hearth kiln according to claim 1 or 2, wherein the heat insulating wall is a vacuum heat insulating wall.

  The invention according to claim 4 is characterized in that, in the roller hearth kiln according to any one of claims 1 to 3, the heat insulating wall is configured with the ceiling portion, the floor portion, and the left and right side wall portions as block bodies, respectively. is there.

  The invention according to claim 5 is the roller hearth kiln according to any one of claims 1 to 4, characterized in that the metal case is a stainless steel case or an inconel case made of stainless steel. is there.

  The invention according to claim 6 is the roller hearth kiln according to any one of claims 1 to 5, characterized in that the low dusting roller is a fused silica roller.

  The invention according to claim 7 is the roller hearth kiln according to any one of claims 1 to 6, characterized in that the low dusting heater is a stainless steel sheathed heater.

The invention according to claim 8 is the roller hearth kiln according to any one of claims 1 to 7 , characterized in that the inside of the outer shell is an airtight space having an oxygen concentration of 10 ppm or less.

Invention of Claim 9 is a method of heat-processing a workpiece | work with the roller hearth kiln in any one of Claims 1-8 , Comprising: A setterless conveyance is carried out by a roller directly, without using a setter. It is characterized by.

  A roller hearth kiln according to the present invention includes a low dust-generating roller for conveying a workpiece in a furnace space in which a ceiling portion, a floor portion, and left and right side wall portions are configured by a heat insulating wall filled with a heat insulating material in a metal case. It has a main body and an outer shell that covers the entire main body, and supports the rollers that penetrate the roller through holes formed in the left and right side walls of the main body with a low dust-generating roller drive provided in the outer shell. In the furnace space, the cleanliness in the heating furnace can be maintained at a high level of class 10 by a configuration including a low dusting heater.

  According to the second aspect of the present invention, the metal case is provided with a pipe serving as an atmosphere discharge path from the inside to the outside of the furnace, and the heat insulation filled in the metal case by making the inside of the metal case a sealed structure. Particles from the material can be prevented from scattering into the furnace.

  According to the invention of claim 4, each of the ceiling part, the floor part, and the left and right side wall parts is configured as a block body filled with a heat insulating material in separate metal cases, and the main body part is configured by combining these, By making each block a structure that can absorb thermal expansion without welding, the influence of deformation due to heat can be reduced.

It is a front view of the roller hearth kiln of this embodiment. FIG. 2 is a top view of FIG. 1. It is a side view of FIG. It is a principal part enlarged view of the roller hearth kiln of this embodiment. It is a front view of the roller hearth kiln in other embodiment.

  Preferred embodiments of the present invention are shown below. The roller hearth kiln of this embodiment is suitable for use in the annealing process in the low temperature polysilicon TFT manufacturing process in the manufacturing process of the organic EL, and the required level of in-furnace cleanliness (US Federal Standard 209D) is set. Class 10 is assumed. The furnace space has a size optimal for heat treatment of a so-called G8 size large substrate (2500 × 2200 mm).

  As shown in FIGS. 1 to 3, the roller hearth kiln according to the present embodiment includes a main body 1 having a low dust generation roller 6 for conveying a workpiece in a furnace space, and an outer shell that covers the entire main body. A double wall structure having 2 is adopted.

  As shown in FIG. 4, the low dust generation roller 6 that has passed through the roller through holes 12 formed in the left and right side wall portions of the main body is supported by the low dust generation roller driving unit 7 provided in the outer shell 2, As a heating means, a low dust-generating heater 8 is provided in the furnace space of the main body 1. In this embodiment, a fused silica roller is used as the low dust generation roller 6, a stainless steel sheathed heater is used as the low dust generation heater 8, and the low dust generation roller driving unit 7 is connected to the low dust generation bearing 9. And a pillow bearing 10 and a magnetic seal rotating mechanism 11. By using the magnetic seal rotating mechanism 11 in the rotating mechanism introducing portion into the furnace, the oxygen concentration in the furnace can be efficiently reduced with a smaller amount of nitrogen gas introduced.

  The low dust generation bearing 9 is a self-lubricating composite material in which a plurality of steel balls arranged between an inner ring and an outer ring are rotatably arranged, and each steel ball is positioned between the steel balls in the circumferential direction. Is set up. The pillow bearing 10 is a plummer type bearing having an oil reservoir for oil bathing the trochanter of the rolling bearing.

  The ceiling part 3, the floor part 4, and the left and right side wall parts 5 of the main body part 1 are each composed of a heat insulating wall filled with a heat insulating material in a metal case. For the metal case, a metal material such as a stainless steel case made of stainless steel or an inconel case made of Inconel is used.

  Conventionally, in the roller hearth kiln, in order to maintain the furnace temperature heated by the heater, the furnace wall has a heat insulating structure. Conventional heat insulation structure is usually made of a heat insulation wall composed of a heat insulating material layer made of ceramic fiber or the like, for example, for heating a PDP or an electronic component having a required cleanliness level in a furnace of about 1000 to 10,000. Was usable without problems. However, in the conventional structure, since particles inevitably generated from the heat insulating material exist, it is difficult to achieve a class 10 level in-furnace cleanliness.

  On the other hand, in the present invention, the ceiling part 3, the floor part 4, and the left and right side wall parts 5 are composed of a heat insulating wall filled with a heat insulating material in a metal case, so that particles from the heat insulating material It is possible to prevent scattering in the furnace. As another form, as shown in FIG. 5, the metal case is provided with a pipe 13 serving as an atmosphere discharge path from the inside to the outside of the furnace, and the inside of the metal case has a sealed structure, so that the inside of the metal case is It becomes negative pressure and can improve the heat insulation effect. Further, it is possible to more reliably avoid the phenomenon that particles from the heat insulating material filled in the metal case are scattered in the furnace. In this embodiment, the piping is connected to factory exhaust.

  The heat insulating wall may be a vacuum heat insulating wall which is further evacuated after filling a metal case with a heat insulating material. The vacuum heat insulation technology that surrounds the vacuum space with thin stainless steel has been known as a technology for avoiding heat transfer by heat conduction and convection, and has an advantage that the thickness of the heat insulation wall can be reduced. However, in the prior art in which the heat insulating material is not filled in the metal case, heat energy is transmitted through the vacuum in the metal case. Therefore, heat transfer by radiation is performed in an environment where the furnace temperature is 250 ° C. or higher. Therefore, there is a problem that a desired heat insulation effect cannot be obtained.

  On the other hand, heat transfer by radiation is effectively suppressed even in an environment where the furnace temperature becomes 250 ° C. to 600 ° C. by further filling a metal case made into a vacuum space with a heat insulating material. Can do. As a means for constituting the vacuum heat insulating wall, the inside of the metal case filled with the heat insulating material is evacuated by using a vacuum pump, and the vacuum valve 14 connected to the metal case is shut off to make the inside vacuum. In addition to means for sealing, a means for evacuating the inside of the metal case at all times during the heat treatment by connecting a vacuum pipe to the metal case can also be employed.

  By the way, in the environment where the furnace temperature of the main body 1 is 250 ° C. to 600 ° C., the deformation of the metal case constituting the ceiling 3, floor 4, and left and right side walls 5 of the main body 1 is very large. It becomes a problem.

  On the other hand, in this embodiment, the ceiling part 3, the floor part 4, and the left and right side wall parts 5 are each configured as a block body in which a separate metal case is filled with a heat insulating material, and these are combined to form a main body part. doing. Each block is not welded and has a structure capable of absorbing thermal expansion, thereby reducing the influence of deformation due to heat. On the other hand, when the block structure is adopted, there arises a new problem that it becomes difficult to maintain the atmosphere in the furnace. In this embodiment, the entire main body is covered with the outer shell 2 and the gap between the outer shells is sealed with packing. By making the inside of the outer shell into a sealed space and maintaining the inside of the furnace at a positive pressure, particles existing in the outer shell having a cleanness of class 100 level are placed in the inner space of the main body 1. The phenomenon of flowing in is avoided and the atmosphere inside the furnace is maintained.

  In addition, the rust of the metal case can be suppressed by setting the inside of the outer shell to a low oxygen atmosphere having an oxygen concentration of 10 ppm or less. In the present invention, the entire main body is covered with the outer shell 2, and the space between the outer shells is sealed with packing, thereby forming the sealed space inside the outer shell.

  In an organic EL device that emits light by itself, it is necessary to supply a current of 10 μA or more for each pixel as energy for light emission. Therefore, it is very important to form a thin film transistor (TFT). The roller hearth kiln of the present invention is suitable for use in the annealing process of the low-temperature polysilicon TFT manufacturing process for forming silicon polycrystal on the glass substrate, and also causes the back surface of the glass substrate to be generated during conveyance in the furnace. Although sufficient care is required, the roller hearth kiln according to the present invention achieves a class 10 level in-furnace cleanliness with the above-mentioned configuration, and therefore, a glass substrate is directly placed on a fused silica roller and setterless. Can be transported. According to the setterless conveyance, dust generation due to friction between the roller and the setter can be suppressed, the weight of the conveyed product can be reduced, and the thermal efficiency can be improved.

DESCRIPTION OF SYMBOLS 1 Main-body part 2 Outer shell 3 Ceiling part 4 Floor part 5 Left-right side wall part 6 Low dust generation roller 7 Low dust generation roller drive part 8 Low dust generation heater 9 Low dust generation bearing 10 Pillow bearing 11 Magnetic seal rotation mechanism 12 Roller through hole 13 Piping 14 Vacuum valve

Claims (9)

A main body provided with a low dust-generating roller for work transfer in a furnace space in which a ceiling part, a floor part, and left and right side wall parts are constituted by a heat insulating wall filled with a heat insulating material in a metal case, and the whole main body part A low-dust bearing composed of a low dust-generating bearing, a pillow bearing, and a magnetic seal rotating mechanism provided on the outer shell, with a roller having a covering outer shell and penetrating a roller through hole formed in the left and right side wall portions of the main body. A roller hearth kiln supported by a dust-generating roller drive and equipped with a low dust-generating heater in the furnace space.   The roller hearth kiln according to claim 1, wherein the metal case includes a pipe serving as an atmosphere discharge path from the inside to the outside, and the inside of the metal case has a sealed structure.   The roller hearth kiln according to claim 1 or 2, wherein the heat insulating wall is a vacuum heat insulating wall.   The roller hearth kiln according to any one of claims 1 to 3, wherein a heat insulating wall is formed by using a ceiling part, a floor part, and left and right side wall parts as block bodies.   The roller hearth kiln according to any one of claims 1 to 4, wherein the metal case is a stainless steel case or an inconel inconel case.   The roller hearth kiln according to any one of claims 1 to 5, wherein the low dusting roller is a fused silica roller.   The roller hearth kiln according to any one of claims 1 to 6, wherein the low dust generating heater is a stainless steel sheathed heater. The roller hearth kiln according to any one of claims 1 to 7 , wherein the outer shell is an airtight space having an oxygen concentration of 10 ppm or less . A method for heat-treating a workpiece with the roller hearth kiln according to any one of claims 1 to 8, wherein the workpiece is setterlessly conveyed by a roller directly without using a setter. Heat treatment method.

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