JP2011187910A - Conveyance mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conveyance mechanism capable of highly maintaining conveying precision by suppressing a rise in temperature of an arm section itself. <P>SOLUTION: This conveyance mechanism for carrying in/out an object W to be treated with respect to a treatment apparatus which carries out heat treatment to the object to be treated in a treatment container 56 is provided with: arm sections 36A and 36B equipped with a plurality of arms 94, 96 and 98, and configured to bend/stretch and turn; fork sections 38A and 38B connected to the top ends of the arm sections, and configured to hold the object to be treated; and a heat shielding plate 104 formed at a section intruding in the treatment container in the arm sections. Thus, it is possible to highly maintain conveying precision by suppressing a rise in temperature of the arm section itself. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a transport mechanism that transports a target object such as a plate-shaped semiconductor wafer to a processing apparatus or the like.

  In general, in order to manufacture a semiconductor device or the like, various processes such as a film formation process, an etching process, an oxidative diffusion process, and a modification process are repeatedly performed on an object to be processed such as a plate-shaped semiconductor wafer or a glass substrate. It is necessary to apply. For example, when a plurality of types of processing are performed by a single-wafer processing apparatus, a plurality of processing apparatuses are connected via a gate valve around a common transfer chamber provided with a transfer mechanism inside (for example, Patent Documents). 1). Then, using the transfer mechanism in the common transfer chamber, the semiconductor wafers are sequentially transferred toward the respective processing apparatuses to sequentially perform desired processing on the semiconductor wafers.

  Here, the situation when the semiconductor wafer is transferred to the processing apparatus by the conventional transfer mechanism will be described. FIG. 12 is a schematic configuration diagram showing a positional relationship between a conventional transport device and a processing device. As shown in FIG. 12, the processing apparatus 2 has a processing container 4 that can be evacuated, and in this processing container 4, a mounting table for mounting a semiconductor wafer W thereon. 6 is provided. The mounting table 6 is provided with heating means 8 composed of a resistance heater or the like, and heats the semiconductor wafer W to be mounted.

  A shower head 10 is provided on the ceiling of the processing container 4 so as to face the mounting table 6, so that necessary gas can be introduced into the processing container 4. Further, a carry-in / out port 12 for the semiconductor wafer W is provided on the side wall of the processing container 4, and a vacuum transfer chamber (not shown) is provided in the carry-in / out port 12 via a gate valve G. A transfer mechanism 14 for transferring the semiconductor wafer W in and out of the vacuum transfer chamber is provided.

  The transport mechanism 14 includes an arm portion 16 that can be bent and stretched and turned, and a fork portion 18 connected to the tip of the arm portion 16. Then, a part of the arm portion 16 including the fork portion 18 is caused to enter the processing container 4 through the loading / unloading port 12 so that the semiconductor wafer W is loaded / unloaded. In order to place the semiconductor wafer W on the mounting table 6 here, lifting pins (not shown) are moved up and down.

JP 2004-160613 A

  By the way, when the arm portion 16 of the transport mechanism 14 is repeatedly entered into the processing container 4 as the semiconductor wafer is carried in / out as described above, the heat is generated by the radiant heat from the mounting table 6 brought into a high temperature state by the heat of the heating means 8. It is inevitable that the distal end side of the arm portion 16 is in a considerably high temperature state, for example, a high temperature state up to about 300 ° C. depending on process conditions. For this reason, the arm portion 16 itself thermally expands and warps, and the tension of the timing belt for turning provided in the arm portion 16 also changes. As a result, there is a problem that the conveyance accuracy of the arm portion 16 having a high conveyance accuracy within ± 0.05 mm per operation is lowered.

  The present invention has been devised to pay attention to the above problems and to effectively solve them. The present invention is a transport mechanism that can maintain a high transport accuracy by suppressing a temperature rise of the arm portion itself.

  According to the first aspect of the present invention, in the transport mechanism for carrying the processing object in and out of the processing apparatus that heat-treats the processing object in the processing container, the processing mechanism has a plurality of arms and can bend and stretch and turn. An arm part; a fork part connected to the tip of the arm part to hold the object to be processed; and a heat shielding plate provided in a part of the arm part that enters the processing container. It is the conveyance mechanism characterized by these.

  As described above, in the transport mechanism for carrying the workpiece in and out of the processing apparatus for performing the heat treatment on the workpiece in the processing container, the tip of the arm portion having a plurality of arms and capable of bending and stretching and turning. The fork that holds the object to be processed is connected to the arm, and the heat shielding plate is provided at the part of the arm that penetrates into the processing vessel. Can be maintained.

  According to a fifth aspect of the present invention, in the transport mechanism for carrying the processing object in and out of the processing apparatus for performing heat treatment on the processing object in the processing container, the processing mechanism has a plurality of arms and can bend and stretch and turn. A transport mechanism comprising: an arm part; a fork part connected to a tip of the arm part to hold the object to be processed; and a heat shielding layer formed on a surface of the arm part. .

  As described above, in the transport mechanism for carrying the workpiece in and out of the processing apparatus for performing the heat treatment on the workpiece in the processing container, the tip of the arm portion having a plurality of arms and capable of bending and stretching and turning. Since the fork portion for holding the object to be processed is connected to the arm portion and the heat shielding layer is formed on the surface of the arm portion, it is possible to suppress the temperature rise of the arm portion itself and maintain high conveyance accuracy. .

  According to a sixteenth aspect of the present invention, there is provided a transport mechanism for carrying the workpiece in and out of a processing apparatus for performing a heat treatment on the workpiece in a processing container. An arm part, a fork part connected to the tip of the arm part to hold the object to be processed, a heat shielding plate provided in a part of the arm part that enters the processing container, And a heat shielding layer formed on the surface.

  As described above, in the transport mechanism for carrying the workpiece in and out of the processing apparatus for performing the heat treatment on the workpiece in the processing container, the tip of the arm portion having a plurality of arms and capable of bending and stretching and turning. A fork for holding the object to be processed is connected to the arm, a heat shielding plate is provided in a portion of the arm that enters the processing container, and a heat shielding layer is formed on the surface of the arm. It is possible to suppress the temperature rise and maintain high conveyance accuracy.

According to the transport mechanism of the present invention, the following excellent effects can be exhibited.
According to the invention according to claim 1 and the claim that refers to this, the transport mechanism for carrying the processing object into and out of the processing apparatus that heat-treats the processing object within the processing container has a plurality of arms. The fork that holds the object to be processed is connected to the tip of the arm that can be bent and stretched and swiveled, and a heat shielding plate is provided at the part of the arm that enters the processing vessel. It is possible to keep the conveyance accuracy high by suppressing the temperature rise of the part itself.

  According to the invention according to claim 5 and the claim that refers to this, the transport mechanism for carrying the processing object into and out of the processing apparatus that heat-treats the processing object within the processing container has a plurality of arms. A fork that holds the object to be processed is connected to the tip of the arm that can be bent and stretched, and a heat shield layer is formed on the surface of the arm to suppress the temperature rise of the arm itself Thus, the conveyance accuracy can be maintained high.

  According to a sixteenth aspect of the present invention, and a transport mechanism for carrying in and out the object to be processed with respect to the processing apparatus for performing a heat treatment on the object to be processed in the processing container, the transport mechanism includes a plurality of arms. The fork that holds the object to be processed is connected to the tip of the arm that can be bent and stretched and swiveled, and a heat shielding plate is provided in the part of the arm that enters the processing vessel. Since the heat shielding layer is formed, the temperature rise of the arm portion itself can be suppressed and the conveyance accuracy can be maintained high.

It is a schematic plan view which shows an example of the general processing system which has the conveyance mechanism which concerns on this invention. It is a schematic sectional drawing which shows the processing system shown in FIG. It is a top view which shows 1st Example of the conveyance mechanism which concerns on this invention. It is a figure which shows a part of arm part of the conveyance mechanism which provided the heat shielding board. It is a fragmentary sectional view which shows a part of arm part of 2nd Example of the conveyance mechanism of this invention. It is sectional drawing which shows a 3rd arm. It is a top view which shows a fork part. It is a schematic perspective view which shows the part of the 2nd arm of the conveyance mechanism used for evaluation. It is a graph which shows working amount and the amount of displacement (warping amount) to the up-down direction of the arm part of a conveyance mechanism. It is a graph which shows the change to the length direction of the arm part of a conveyance mechanism. It is a graph which shows the relationship between the emissivity of an alumina layer, and the wavelength of a thermal radiation. It is a schematic block diagram which shows the positional relationship of the conventional conveying apparatus and a processing apparatus.

  Hereinafter, an embodiment of a transport mechanism according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic plan view showing an example of a general processing system having a transport mechanism according to the present invention, FIG. 2 is a schematic sectional view showing the processing system shown in FIG. 1, and FIG. FIG. 4 is a plan view showing one embodiment, and FIG. 4 is a view showing a part of an arm portion of a transport mechanism provided with a heat shielding plate.

  First, an example of a processing system having a transport mechanism according to the present invention will be described. As shown in FIGS. 1 and 2, the processing system 22 includes four processing devices 24A, 24B, 24C, and 24D that can be evacuated. As these processing apparatuses 24A to 24D, all processing apparatuses performed in a vacuum atmosphere such as a film forming process and an etching process are applied. These processing devices 24 </ b> A to 24 </ b> D are connected via a gate valve G around a hexagonal transfer chamber 26 that can be evacuated. Further, the processing system 22 includes load lock devices 30A and 30B for transferring the semiconductor wafer W as an object to be processed into the transfer chamber 26 without breaking the vacuum. The locking devices 30A and 30B are connected to the transfer chamber 26 through gate valves G, respectively.

  And in each said processing apparatus 24A-24D, the mounting bases 32A-32D for mounting the semiconductor wafer W are each provided. The transfer chamber 26 is provided with a transfer mechanism 34 according to the present invention that can be bent and stretched to transfer the semiconductor wafer W. The transfer chamber 26 is provided between the processing devices 24A to 24D and the load lock devices. The semiconductor wafer W can be transferred between 30A and 30B. Specifically, the transport mechanism 34 includes two arm portions 36A and 36B that can be bent and stretched as described above, and fork portions 38A and 38B provided at the distal ends of the arm portions 36A and 36B. The semiconductor wafer W is directly placed and held on the forks 38A and 38B, and can be transported as described above. Details of the transport mechanism 34 will be described later.

  In addition, base stands 40A and 40B are provided in the load lock devices 30A and 30B, respectively, for temporarily holding the semiconductor wafer W. A laterally long load module 42 is attached to the opposite side of the load lock devices 30A and 30B via gate valves G, respectively. A cassette (multiple wafers) can be accommodated on one side of the load module 42. There is provided an I / O port 44 on which (not shown) is placed. In the load module 42, an atmosphere-side transport mechanism 46 that can be bent and stretched is provided.

  The atmosphere-side transport mechanism 46 is mainly composed of two arm portions 48 that can be bent and stretched as described above, and two fork portions 50 provided at the distal ends of the arm portions 48. The semiconductor wafer W can be directly placed and held on these fork portions 50 and transported. The atmosphere-side transport mechanism 46 is movable along the guide rail 52 in the longitudinal direction. At one end of the load module 42, an orienter 54 for aligning and directing the semiconductor wafer W is provided. Before the semiconductor wafer W is loaded into the processing apparatuses 24A to 24D, the semiconductor wafer W is here. Are aligned and oriented.

<Transfer chamber having first embodiment of processing apparatus and transport mechanism of present invention>
Here, with reference to FIG. 2, a transfer chamber having a first embodiment of each processing apparatus and the transport mechanism of the present invention will be described. In FIG. 2, the processing device 24A is shown as a representative of the four processing devices 24A to 24D, and the mounting table 32A is provided therein.

  The processing apparatus 24A includes a processing container 56 formed into a box shape from, for example, an aluminum alloy. The mounting table 32A provided in the processing container 56 is attached to the upper end of a support column 58 erected from the bottom of the container. A heating means 60 made of, for example, a resistance heater is embedded in the mounting table 32A so that the semiconductor wafer W mounted on the mounting table 32A can be heated to a predetermined temperature. Yes. As will be described later, the arm portions 36A and 36B of the transport mechanism 34 are also heated by the heating means 60. A lifter mechanism 62 is provided on the mounting table 32A to push up and pull down the semiconductor wafer W when the semiconductor wafer W is loaded and unloaded.

  The lifter mechanism 62 has three lifting pins 64 (only two are shown in the illustrated example), and the lower ends of the lifting pins 64 are commonly supported by a lifting plate 66 having an arc shape. . The elevating plate 66 is supported by the upper end of an elevating rod (not shown) provided through the bottom of the container, and the elevating rod can be raised and lowered by an actuator (not shown).

  The mounting table 32A is provided with a pin insertion hole 68 for inserting the elevating pin 64, and the elevating pin 64 is moved up and down when the semiconductor wafer W is loaded and unloaded. It can be made to appear upwards. Further, a gas supply means 70 such as a shower head is provided on the ceiling portion of the processing container 56 so as to supply necessary gas into the processing container 56. Of course, the gas supply means 70 is limited to a shower head.

  An exhaust port 72 is provided at the bottom of the vessel, and an exhaust unit 74 for exhausting the atmosphere in the processing vessel 56 is provided at the exhaust port 72. The exhaust means 74 has a pressure adjusting valve for adjusting the pressure in the container and a vacuum pump (not shown). A loading / unloading port 76 for the semiconductor wafer W is provided on the side wall of the processing chamber 56, and the loading / unloading port 76 is connected to the transfer chamber 26 through a gate valve G. A heat treatment such as a film forming process is performed in the processing apparatus 24A thus formed.

  Further, as the other processing apparatuses 24B to 24D, processing apparatuses corresponding to various processes to be performed on the semiconductor wafer W are used as necessary, and plasma processing apparatuses can also be used. Here, the heat treatment includes all processes in such a state that the semiconductor wafer itself and the mounting table 32A are heated as a result of the processing of the semiconductor wafer W, and is not directly related to the presence or absence of plasma.

  The transfer chamber 26 has a transfer container 80 formed into a box shape from aluminum, an aluminum alloy, or the like. On the side wall of the transfer container 80, a loading / unloading port 82 for loading / unloading semiconductor wafers corresponding to the processing devices 24A to 24B and the load lock devices 30A and 30B is formed. The above devices are connected via each other.

The transfer container 80 is provided with a gas introduction port 84 and a gas discharge port 86, and for example, N ₂ gas can be introduced as an inert gas through the gas introduction port 84. The internal atmosphere can be evacuated from the gas discharge port 86. The interior of the transfer chamber 26 is always in a vacuum atmosphere during operation.

  In the transfer chamber 26, the transfer mechanism 34 according to the present invention is provided as described above. The basic structure of the transport mechanism 34 is disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-229087. Specifically, as shown in FIGS. 3 and 4, the transport mechanism 34 includes two arm portions 36 </ b> A and 36 </ b> B and fork portions 38 </ b> A and 38 </ b> B connected to the distal ends thereof as described above. It has mainly. Here, FIG. 3A shows a state where both the arm portions 36A and 36B are contracted, and FIG. 3B shows a case where one arm portion is extended.

  Specifically, the arm portions 36A and 36B are attached to a rotation base 90 provided on the bottom of the container so as to be rotatable via a drive shaft 88, respectively. The drive shaft 88 has, for example, a biaxial structure, and is driven to rotate independently by a drive source 92 made of a motor. One shaft of the drive shaft 88 of this biaxial structure is connected to the rotation base 90 so as to rotationally drive it. Each of the arm portions 36A, 36B is formed by connecting the first arm 94, the second arm 96, and the third arm 98 in series in this order so as to be bendable from the base end side, respectively. It can be expanded and contracted in the horizontal direction.

  The base end portion of the first arm 94 is rotatably supported by the rotary base 90. A driving arm 97 connected to the other driving shaft of the biaxial structure is attached to the rotating base 90. A driven arm 100 (see FIG. 3) is stretched between the distal end portion of the drive arm 97 and the central portion in the length direction of the first arm 94 of each of the arm portions 36A and 36B. Both ends of the shaft are rotatably supported. Therefore, as will be described later, the fork portions 38A and 38B are oriented by turning the rotary base 90, and the two arm portions 36A and 36B are alternately turned by turning the drive arm 97 left and right. It can be expanded and contracted selectively. In FIG. 2, one arm portion 36A is mainly shown, but the other arm portion 36B is similarly formed.

  Here, each of the first arm 94 and the second arm 96 has an arm case 99 formed in an elongated box shape from aluminum, aluminum alloy or the like, and pulleys 101A, 101B, 101C, and 101D are provided, respectively. The pulleys 101A and 101C on the turning center side are fixed to the arm cases 99 of the first arm 94 and the second arm 96, respectively, and the pulleys 101B and 101D on the opposite side are respectively arm cases via the rotation shafts 105B and 105C. 99 is rotatably provided. A rotating shaft 105A that is rotated by a driving force from a driving source 92 is provided on the upper portion of the rotating base 90, and the rotating shaft 105A is fixed to the base end side of the first arm 94.

  Timing belts 103A and 103B are stretched between the pulleys 101A and 101B and between 101C and 101D, respectively, so that the driving force is transmitted to the distal ends of the arm portions 36A and 36B.

  Further, the third arm 98 is formed in a short plate shape by aluminum, aluminum alloy or the like, and the fork portion 38A or the fork portion 38B is connected to the tip of the third arm 98 via a connecting member 102. The fork portions 38A and 38B are formed in a bifurcated shape, and this material is made of a ceramic material such as alumina, aluminum nitride, or silicon carbide. The connecting member 102 can be made of a low thermal conductivity member having a low thermal conductivity, for example, a machinable ceramic material that is improved in workability by adding an additive to alumina.

  Here, the dimensions of the respective members are as follows. When the diameter of the semiconductor wafer W to be processed is, for example, 300 mm, the first arm 94 has a length of about 370 mm, a thickness of about 10 to 20 mm, and a width of about 90 to 100 mm. The second arm 96 has a length of about 370 mm, a thickness of about 10 to 20 mm, and a width of about 80 to 90 mm. The third arm 98 has a length of about 150 mm and a thickness of about 5 to 10 mm. The width is about 80 to 90 mm.

  A heat shielding plate 104, which is a feature of the present invention, is provided at a portion of the arm portions 36A and 36B formed in this way and entering the processing container 56, and from the mounting table 32A side. The radiant heat that is mainly transmitted is cut off. Specifically, as shown in FIG. 2 to FIG. 4, here, the second arm 96 is provided at the tip, that is, the tip on the third arm 98 side. The state at this time is shown in FIG. 4, FIG. 4 (A) shows a top view, FIG. 4 (B) shows a side sectional view, and FIG. 4 (C) shows a bottom view. In FIG. 4, a side heat shield plate 104 </ b> A is provided as the heat shield plate 104 so as to surround and cover the entire side surface of the distal end portion of the second arm 96, and the entire lower surface of the distal end portion of the second arm 96 is covered. Is provided with a heat shield plate 104B for the lower surface.

  The side heat shielding plate 104A is formed in a U shape as shown in the drawing, and is slightly lifted from the side surface of the second arm 96, for example, by about 1 to 5 mm, with spacer members 106 interposed at both ends thereof. The pin 108 is attached and fixed to the second arm 96. Further, the heat shield plate 104B for the lower surface is formed in a plate shape, and is slightly lifted by, for example, about 1 to 5 mm from the lower surface of the second arm 96, and is attached to the second arm 96 by the pin 112 with the spacer member 110 interposed. Installation is fixed. Here, the heat shielding plate 104 is provided at a portion that enters the processing container 56 rather than the gate valve G with the gate valve as a boundary when the arm portion 36A is extended. As the heat shielding plate 104, a material having a small heat capacity, for example, a metal plate such as aluminum, aluminum alloy, or stainless steel, or a ceramic material such as aluminum oxide or alumina can be used.

  Further, the surface of the heat shielding plate 104 is preferably made into a mirror surface by polishing so as to easily reflect the radiant heat. The thickness of the heat shield plate 104 is about 0.5 to 2 mm, and the length L1 covering the tip of the second arm 96 depends on the length of penetration of the first arm 96 into the processing container 56. For example, it is about 120 mm. The spacer members 106 and 110 can be made of a material having low thermal conductivity, for example, a ceramic material such as alumina or aluminum nitride. Here, both the heat shield plate 104A for the side surface and the heat shield plate 104B for the lower surface are provided as the heat shield plate 104, but the present invention is not limited to this, and only one of them may be provided. In addition, although the description has been given mainly taking the one arm portion 36A as an example, it goes without saying that the heat shielding plate 104 (104A, 104B) is similarly provided on the other arm portion 36B as described above.

  Next, the operation of the transport mechanism 34 will be described as described above. First, a schematic flow of a semiconductor wafer in the processing system 22 will be described. From a cassette container (not shown) installed in the I / O port 44, an unprocessed semiconductor wafer W is taken into the load module 42 by the atmosphere-side transfer mechanism 46, and the taken semiconductor wafer W is loaded into the load module. It is conveyed to an orienter 54 provided at one end of 42, where it is positioned and oriented. The semiconductor wafer W is made of, for example, a plate-like silicon substrate.

  The semiconductor wafer W that has been positioned is transferred again by the atmosphere-side transfer mechanism 46 and is carried into one of the two load lock devices 30A and 30B. After the inside of the load lock device is evacuated, the semiconductor wafer W in the load lock device is taken into the transfer chamber 26 using the transfer mechanism 34 in the transfer chamber 26 that has been evacuated in advance.

  The unprocessed semiconductor wafer taken into the transfer chamber 26 is sequentially transferred to the processing apparatuses 24A to 24D as necessary by the transfer mechanism 34 of the present invention, and predetermined in each of the processing apparatuses 24A to 24D. Will be processed. For example, the semiconductor wafer W is subjected to a heat treatment such as a film forming process, an etching process, or an oxidation diffusion process. The semiconductor wafer W is in a high temperature state of about 300 to 700 ° C., for example, depending on the mode of processing performed here.

  The semiconductor wafer W, which has been processed after all the various processes to be performed in this way, is carried into one of the two load lock apparatuses 30A and 30B by the transfer mechanism 34. The Then, the inside of the load lock device is returned to the atmospheric pressure, and after the return to the atmospheric pressure, the semiconductor wafer W in the load lock device is taken into the load module 42 using the atmosphere side transfer mechanism 46, and further the I / O port. It is accommodated in a cassette container (not shown) for 44 processed semiconductor wafers. Then, the above operation is repeated, and the semiconductor wafer W is continuously processed.

  Here, the operation of the transport mechanism 34 in the transfer chamber 26 will be described in detail. As described above, the fork portions 38A and 38B are oriented by rotating the rotation base 90 of the transport mechanism 34, and the two arm portions 36A and 36B are alternately selected by rotating the drive arm 97 left and right. When one arm portion is extended, the other arm portion is maintained in a contracted state. FIG. 2 shows the processing apparatus 24A as an example. One arm portion 36A extends, and the tip of the arm portion 36A and the fork portion 38A are moved into the processing container 56 through the opened gate valve G. Invaded.

  Then, the semiconductor wafer W is transferred between the fork portion 38A and the mounting table 32A by moving the lifting pins of the mounting table 32A up and down. The time for which the fork portion 38A stays in the processing container 56 by this single transfer is, for example, about 1 to 2 seconds, although it depends on the conveyance speed.

  Here, the mounting table 32 </ b> A is in a high temperature state of, for example, about 300 to 700 ° C., depending on the heat treatment process conditions. Therefore, every time the semiconductor wafer W is loaded / unloaded using the transport mechanism 34, the fork portion 38A and the arm portion 36A are inevitably heated gradually by receiving radiant heat from the mounting table 32A. In particular, as shown in FIG. 2, the distal end side of the second arm 96 is closest to the mounting table 32A, and thus receives a large amount of radiant heat as shown by an arrow 120 (see FIG. 2). In this case, in the conventional transport mechanism shown in FIG. 12, since the arm portion is not provided with any protective member for blocking radiant heat, the arm portion becomes in a high temperature state, which causes inconvenience such as a decrease in transport accuracy. Has occurred.

  However, in the present invention, as described above, the heat shielding plate 104, that is, the side surface heat shielding plate 104A is provided on the distal end side of the second arm 96, which is the portion of the arm portion 36A that enters the processing container 56. And the shielding plate 104B for the lower surface, it is possible to block radiant heat as indicated by the arrow 120 radiated from the mounting table 32A. As a result, excessive temperature rise of the second arm 96 can be prevented, and not only the entire arm portion 36A can be prevented from warping due to thermal expansion, but also the timing belt provided inside can be prevented. It is possible to suppress adverse effects on the tension and the like. Therefore, it is possible to maintain high transfer accuracy of the semiconductor wafer W.

  Specifically, it is possible to achieve a transport accuracy within ± 0.05 mm with a single transport operation. In this case, since the surface of the heat shielding plate 104 is made into a mirror surface by a polishing process, the effect of blocking radiant heat can be further improved. In particular, since the width of the loading / unloading ports 76 and 82 of the processing container 56 and the transfer container 80 is about 36 mm, the effect of suppressing the warping of the arm portion 36A as described above is particularly effective.

  Further, the fork unit 38 itself is brought into a high temperature state by the radiant heat from the mounting table 32A and the heat conduction from the high temperature semiconductor wafer W by the transfer processing of the semiconductor wafer W. In this embodiment, the third arm 98 and the fork unit Since a material having low thermal conductivity, such as a machinable ceramic material, is used as the connecting member 102 that connects to 38A, the heat conduction to the third arm 98 and second arm 96 side is suppressed, and the second The temperature rise of the arm 96 can be further suppressed.

  Here, one arm portion 36A has been described, but it is needless to say that the same effect can be achieved in the other arm portion 36B. In addition, in the other processing apparatuses 24B to 24D, when performing heat treatment such that the temperature of the semiconductor wafer W or the mounting table is in a high temperature state, it is needless to say that the same effect as described above can be exhibited.

  As described above, according to the first embodiment of the present invention, a plurality of arms are provided in the transfer mechanism for transferring the object to be processed to / from the processing apparatus that heat-treats the object to be processed, for example, a semiconductor wafer, in the processing container 56. The forks 38A and 38B for holding the object to be processed are connected to the tips of the arms 36A and 36B having 94, 96 and 98 that can bend and extend and swivel, and enter the processing container within the arms. Since the heat shielding plate 104 is provided in the part to be performed, the temperature rise of the arm part itself can be suppressed and the conveyance accuracy can be maintained high.

  In the above embodiment, the heat shield plate 104 is provided on the tip end side of the second arm 96, but the present invention is not limited to this. The heat shield plate 104 is provided on the entire lower surface or the entire side surface of the second arm 96. Alternatively, it may be provided on both the entire surfaces.

<Second embodiment>
Next, a second embodiment of the transport mechanism of the present invention will be described. In the case of the first embodiment, the heat shield plate 104 is provided on the arm portion of the transport mechanism. Instead, a heat shield layer having high heat insulation is formed on the surface of the transport mechanism. . FIG. 5 is a partial cross-sectional view showing a part of the arm portion of the second embodiment of the transport mechanism of the present invention, FIG. 6 is a cross-sectional view showing the third arm, and FIG. 7 is a plan view showing the fork portion. is there. The same components as those shown in FIGS. 1 to 5 are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 5, here, a heat shielding layer 121 having a low thermal conductivity is formed on the surface of the arm portion 36A of the transport mechanism. Here, for example, a ceramic sprayed layer 122 is used as the heat shielding layer 121. Specifically, the side surface ceramic sprayed layer 122A is provided on the entire side surface of the arm case 99 of the second arm 96 of the arm portion 36A, and the lower surface ceramic sprayed layer 122B is formed on the entire lower surface of the arm case 99. Therefore, the temperature rise inside the second arm 96 is suppressed. As a material of the ceramic sprayed layer 122, a ceramic material such as alumina, aluminum nitride, or silicon carbide can be used. The thickness of the ceramic sprayed layer 122 is, for example, about 0.35 to 0.45 mm.

  Further, the ceramic sprayed layer 122 may have a multilayer structure by laminating a plurality of very thin ceramic sprayed layers. At this time, the material of the ceramic material may be changed for each layer. In this case, the thermal conductivity can be further reduced. Of course, not only the arm portion 36A but also the other arm portion 36B is configured in the same manner as described above. Here, the heat shielding layer 121 has such a characteristic that the emissivity with respect to heat rays in the wavelength range of 7 to 10 μm is larger than the emissivity with respect to heat rays in the wavelength range of 1 to 4 μm. Use what you have. Specifically, the radiation rate for heat rays in the range of 7 to 10 μm is greater than 66%, and the radiation rate for heat rays in the range of 1 to 4 μm is 66% or less. A heat shielding layer 121 is used. The ceramic sprayed layer 122 has characteristics satisfying the above characteristics. As a result, when the second arm 96 approaches the mounting table 32A in the high temperature state, the emissivity is small (reflectance is high), so that the second arm 96 is difficult to be heated, whereas the second arm 96 is in the low temperature state transfer chamber 26. When entering, since the emissivity is large (low reflectivity), it is easy to dissipate heat and is cooled quickly.

  Even in the case of the second embodiment, similarly to the first embodiment, even if the second arm 96 approaching the mounting table 32A as shown in FIG. The thermal conductivity of the ceramic sprayed layer 122 (122A, 122B) provided here is low, and as described above, for heat rays having a wavelength in the range of 1 to 4 μm (heat source temperature is about 450 to 2500 ° C.). Since the emissivity is small, it is difficult to be heated by reflecting the heat rays, and heat can be prevented from being transmitted to the inside of the second arm 96. Moreover, since the emissivity is large with respect to the heat ray (heat source temperature is about 15-140 degreeC) in the range whose wavelength is 7-10 micrometers, it is in the state which is easy to discharge | release a heat ray and is easy to cool. As a result, similarly to the first embodiment, it is possible to prevent the second arm 96 from being excessively heated, and to prevent the entire arm portion 36A from warping due to thermal expansion. In addition, adverse effects on the tension of the timing belt provided inside can be suppressed. Therefore, it is possible to maintain high transfer accuracy of the semiconductor wafer W. Specifically, it is possible to achieve a transport accuracy within ± 0.05 mm with a single transport operation.

  As described above, according to the second embodiment of the present invention, in the transfer mechanism for transferring the object to be processed to and from the processing apparatus for performing the heat treatment on the object to be processed in the processing container 56, the plurality of arms 94, 96, Fork portions 38A and 38B for holding the object to be processed are connected to the tips of the arm portions 36A and 36B that are capable of bending and swiveling with 98, and a heat shielding layer 121 such as a ceramic sprayed layer is formed on the surface of the arm portion. Since 122 is formed, it is possible to suppress the temperature rise of the arm portion itself and maintain high conveyance accuracy.

  In the second embodiment, the case where the ceramic sprayed layer 122 is formed on the entire side surface and the entire lower surface of the second arm 96 has been described as an example. However, as in the case of the heat shielding plate 104 of the first embodiment, Alternatively, the ceramic sprayed layer 122 may be provided as the heat shielding layer 121 on the entire upper surface of the second arm 96 in addition to the entire side surface and the entire lower surface. May be. Further, in addition to the above configuration, as shown in FIG. 6, a ceramic sprayed layer 124 may be formed as the heat shielding layer 121 on the entire surface of the third arm 98, that is, the lower surface, the side surface, and the upper surface. In this case, it may be formed on any one or more of the lower surface, the side surface, and the upper surface, and if it is formed on at least the lower surface, it is particularly effective from the viewpoint of heat insulation.

  Further, in addition to the above-described components, a ceramic sprayed layer 126 may be provided as the heat shielding layer 121 on the entire surface of the fork portion 38A (38B), that is, the lower surface, the side surface, and the upper surface as shown in FIG. Also in this case, it may be formed on one or more of the lower surface, the side surface, and the upper surface, and if it is formed on at least the lower surface, it is particularly effective from the viewpoint of heat insulation. Although not shown here, a ceramic sprayed layer may be formed as the heat shielding layer 121 on the surface of the first arm 94 in addition to the above components. In the above embodiment, the case where the ceramic sprayed layer 122 is provided as the heat shielding layer 121 has been described as an example. However, the present invention is not limited to this. For example, a paint layer formed by applying paint may be provided. Any material may be used as long as it has a radiation rate with respect to the wavelength as described above. This also applies to the embodiments described below.

<Third embodiment>
Next, a description will be given of a third embodiment of the transport mechanism of the present invention. In the first and second embodiments, the heat shielding plate 104 and the ceramic sprayed layer 122 which is the heat shielding layer 121 are separately provided, but the present invention is not limited to this, and the above-described heat is used as the third embodiment. Both the shielding plate 104 and the ceramic sprayed layer 122 which is the heat shielding layer 121 may be provided. In this case, the combination of the heat shielding plate 104 of the first example and the ceramic sprayed layer 122 which is the heat shielding layer 121 of the second example is described in the various embodiments and the second example described in the first example. The various embodiments described above may be arbitrarily selected and applied.

  According to this, in the transfer mechanism for carrying the processing object in and out of the processing apparatus that heat-treats the processing object in the processing container 56, the plurality of arms 94, 96, 98 can be bent and swung. The fork portions 38A and 38B for holding the object to be processed are connected to the tips of the arm portions 36A and 36B, and a heat shielding plate 104 is provided in a portion of the arm portion that enters the processing container. Since the ceramic sprayed layer 122 is formed on the surface as the heat shielding layer 121, the temperature rise of the arm portion itself can be suppressed and the conveyance accuracy can be maintained high.

  In particular, by combining the heat shielding plate 104 and the ceramic sprayed layer 122 which is the heat shielding layer 121, as will be described later, the temperature rise of the arm portion itself can be further suppressed, and the displacement amount of the arm portion ( Warping amount) and the amount of thermal expansion in the length direction can be greatly suppressed.

<Evaluation of heat shield plate and ceramic sprayed layer>
Next, the first embodiment of the present invention in which the heat shielding plate 104 is provided and the third embodiment of the present invention in which both the heat shielding plate 104 and the ceramic sprayed layer 122 used as the heat shielding layer 121 are provided. Since an experiment for actually operating each transport mechanism 34 was performed, the evaluation result will be described. Here, as the first embodiment, a transport mechanism in which only the side surface heat shield plate 104A is provided as the heat shield plate 104 and the lower surface heat shield plate 104B is not provided in the transport mechanism is used. Further, as a second embodiment, a conveyance mechanism in which a ceramic spray layer 122A for a side surface and a ceramic spray layer 122B for a bottom surface are formed as a ceramic spray layer 122, which is an example of a heat shielding layer 121, as shown in FIG. Using.

  FIG. 8 is a schematic perspective view showing a portion of the second arm of the transport mechanism used for the evaluation. Further, as shown in FIG. 8 as the third embodiment, here, only the side surface heat shielding plate 104A is provided as the heat shielding plate 104, and the lower side heat shielding plate 104B is not provided. Further, the transport mechanism of the third embodiment is provided with both the side surface ceramic spray layer 122A and the bottom surface ceramic spray layer 122B as the ceramic spray layer 122 as an example of the heat shielding layer 121 as shown in FIG. .

  Further, the temperature of the mounting table 32A of the processing apparatus 24A was set to 700 ° C., and the semiconductor wafer was repeatedly carried in and out. FIG. 9 is a graph showing the operating time at this time and the amount of displacement (warpage) in the vertical direction of the arm portion of the transport mechanism. For comparison, data of a conventional transport mechanism that does not include a heat shielding plate and a ceramic sprayed layer are also shown.

  As is apparent from the data shown in FIG. 9, when the transfer operation is started, the temperatures of the arm portions of all the transfer mechanisms gradually increase, so that the vertical displacement amount (warp amount) gradually increases. In this case, in the conventional transport mechanism, the amount of increase in displacement is very large and increases rapidly. And when operating for about 300 minutes, the displacement amount reaches about 1 mm and is saturated. On the other hand, in both the first and third embodiments of the present invention, the amount of increase in displacement is considerably small. In the case of the first embodiment, the displacement amount reaches about 0.7 mm and is saturated when operated for about 300 minutes. In the case of the third embodiment, the displacement amount reaches about 0.45 mm and is saturated when operated for about 240 minutes.

  Thus, in the case of the first embodiment of the present invention, the amount of displacement is about 0.3 mm less than that of the conventional transport mechanism, and in the case of the third embodiment, the amount of displacement is further 0 than in the first embodiment. It was found to be about 25 mm less. Since the upper limit value of the vertical displacement amount of the arm portion is ± 1.0 mm, it has been found that the displacement amount can be sufficiently suppressed in the first and third embodiments. In addition, it can be recognized that the difference in the displacement amount between the first and third embodiments is the effect of the second embodiment of the present invention in which the ceramic sprayed layer is provided on the arm portion.

  Further, even when the heat shielding plate 104 or the ceramic sprayed layer 122 is used alone, the vertical displacement of the arm portion can be suppressed to some extent as described in the first and second embodiments. It has been found that by applying both the heat shielding plate 104 and the ceramic sprayed layer 122 as in the third embodiment, a greater effect can be exhibited.

  The reason why such a large operational effect can be exhibited is that the radiant heat transmitted from the mounting table side is first reflected or blocked by the heat shielding plate 104 to suppress the amount of heat input to the second arm 94 side and the second arm. Even if heat enters the surface of 94, the heat entering the second arm 94 is suppressed by the action of the ceramic sprayed layer 122 having low thermal conductivity formed on the surface. It is presumed that the above-mentioned great effects are exhibited.

  Also, during this experiment, the amount of thermal expansion in the length direction of the conventional transport mechanism and the transport mechanism of the third embodiment of the present invention was examined. FIG. 10 is a graph showing changes in the length direction of the arm portion of the transport mechanism. As shown in FIG. 10, the thermal expansion amount in the length direction of the arm portion is about 4 hours as the operation time increases in the case of the arm portion of the conventional transport mechanism. It can be seen that the time has changed to about 1.4 mm. On the other hand, in the case of the invention of the present application, even if the operation time is increased, the thermal expansion amount does not change so much and is about 0.4 mm. Therefore, the third embodiment of the transport mechanism of the present invention has a smaller amount of thermal expansion than the conventional transport mechanism by about 1 mm, and it can be seen that the third embodiment of the present invention is particularly superior.

  At this time, the temperature of each part was examined using a thermolabel. The locations where this temperature was examined are the three points P1, P2, and P3 in FIG. 3B. Point P1 is the base end of the third arm 98, and point P2 is the tip of the second arm 96. In the arm cover, the point P 3 is in the arm cover at the base end portion of the second arm 96. In the case of the conventional transport mechanism, the temperatures of the above points P1 to P3 were 272 ° C., 193 ° C. and 189 ° C., respectively, but in the case of the third embodiment of the present invention, 204 ° C. and 148 ° C., respectively. And 137 ° C. Thus, in the case of the third embodiment of the present invention, it has been found that the temperature can be greatly reduced at each of the points P1 to P3.

<Action analysis of ceramic sprayed layer>
Next, the cause of the thermal spraying effect of the ceramic sprayed layer as described above was examined and analyzed, and the result of the study will be described.

The present inventors investigated the relationship between the radiation rate of the ceramic sprayed layer and the heat radiation based on the assumption that the radiation rate of the ceramic sprayed layer has a great influence on the heat shielding effect. Here, an alumina (Al ₂ O ₃ ) layer was used as the ceramic sprayed layer. FIG. 11 is a graph showing the relationship between the emissivity of the alumina layer and the wavelength of thermal radiation. The horizontal axis shows the heat source temperature corresponding to the wavelength of the heat radiation. As is well known, the emissivity of a black body is “1”, and the emissivity of the alumina layer varies considerably depending on the wavelength of thermal radiation received by the alumina layer as shown in the graph of FIG. Although the unevenness of the characteristics is somewhat generated in the vicinity of the wavelength of 2.5 to 3.5 μm, the tendency is that the emissivity increases as the wavelength increases from 1 μm to 10 μm.

  Here, the arm portion of the transfer mechanism repeatedly reciprocates between the high temperature processing chamber 56 and the room temperature transfer chamber 26 for transferring the semiconductor wafer. The processing container 56 approaches the mounting table 32A heated to a high temperature, and the transfer chamber 26 is surrounded by a transfer container 80 at room temperature.

Then, heat radiation corresponding to the temperature is made from the mounting table 32A which is a “heat source” in the processing container 56, and the wavelength of the heat radiation is in the range of about 1 to 4 μm depending on the process temperature. This corresponds to a heat source temperature range of 450 to 2500 ° C., which is a process temperature. Here, the actual use temperature in the processing vessel 56 is generally in the range of about 500 to 1000 ° C., for example.
On the other hand, in the transfer chamber 26, heat radiation corresponding to the temperature is made from the transfer container 80 serving as a “heat source”, and the wavelength of the heat radiation is in the range of about 7 to 10 μm. This corresponds to a heat source temperature range of 15 to 140 ° C. Here, the actual use temperature in the transfer chamber 26 is generally in the range of about 50 to 100 ° C., for example.

  In such a state, when the arm having the ceramic sprayed layer having the characteristics shown in FIG. 11 moves back and forth in the transfer chamber 26 and the processing container 56, the heat source temperature is high in the processing container 56, so that heat radiation is generated. Since the wavelength is in the range of 1 to 4 μm, for example, as described above, the emissivity of the ceramic sprayed layer is relatively low for this wavelength, for example, 66% or less. As a result, since the reflectance of the ceramic sprayed layer is high, the ceramic sprayed layer tends to reflect and block the thermal radiation, and the arm itself can be prevented from being heated.

  On the other hand, since the heat source temperature is low (about room temperature) in the transfer chamber 26, the wavelength of the heat radiation is in the range of, for example, 7 to 10 μm as described above. The emissivity is higher than that in the above case, for example, greater than 66%. As a result, since the reflectance of the ceramic sprayed layer is low, the ceramic sprayed layer becomes difficult to reflect the heat radiation and easily radiates heat. As a result, heat dissipation from the ceramic sprayed layer is promoted, and the arm itself is efficiently cooled. By such a phenomenon, it is possible to understand the principle capable of suppressing the temperature rise of the arm itself as described above.

  Furthermore, the heat shielding layer is not limited to the ceramic sprayed layer, but has a high emissivity with respect to the characteristics shown in FIG. 11, that is, the wavelength of heat radiation from a heat source of about room temperature (about 7 to 10 μm), In addition, by using as the heat shielding layer 121 a material having such a characteristic that the radiant heat becomes low with respect to the wavelength (about 1 to 4 μm) of heat radiation from the heat source at the process temperature, the action of the present invention as described above. Can understand that it can be effective.

  In each of the embodiments described above, the case where the heat shielding plate 104 and the heat shielding layer 121 are separately provided has been described as an example. However, the present invention is not limited thereto, and the surface of the heat shielding plate 104 is the heat shielding layer. 121 may be formed to further increase the heat shielding effect.

  In each of the above-described embodiments, the case where the third arm is provided as the arm portion in addition to the first arm and the second arm has been described as an example. The present invention can also be applied to a transport mechanism in which a fork portion is directly connected to the tip of an arm. In each of the above embodiments, the case where the transport mechanism of the present invention is used for a processing apparatus that performs heat treatment in a vacuum atmosphere has been described as an example. However, the present invention is not limited to this, and the transport mechanism of the present invention may be atmospheric pressure or The present invention can also be applied to a processing apparatus that performs heat treatment in an atmosphere close to.

  In each of the above embodiments, the transport mechanism using the drive arm and the conventional arm in addition to the two arm portions has been described as an example. However, the present invention is not limited to this, and the present invention is a so-called frog-leg transport mechanism. The present invention can be applied to all types of transport mechanisms, such as, and scalar type transport mechanisms. Further, in each of the above embodiments, the semiconductor wafer is described as an example of the object to be processed. However, the present invention is not limited to this, and the present invention can be applied to a glass substrate, an LCD substrate, a ceramic substrate, and the like.

DESCRIPTION OF SYMBOLS 22 Processing system 24A-24D Processing apparatus 26 Transfer chamber 32A-32D Mounting stand 34 Transfer mechanism 36A, 36B Arm part 38A, 38B Fork part 56 Processing container 60 Heating means 74 Exhaust means 80 Transfer container 90 Rotation base 92 Drive source 94 First arm 96 Second arm 97 Drive arm 98 Third arm 99 Arm case 110 Drive arm 102 Connecting member 104 Heat shield plate 104A Side heat shield plate 104B Bottom heat shield plate 121 Heat shield layer 122, 124, 126 Ceramic spraying Layer 122A Ceramic spray layer for side surface 122B Ceramic spray layer for bottom surface W Semiconductor wafer (object to be processed)

Claims (30)

In a transport mechanism for transporting the processing object into and out of a processing apparatus for performing a heat treatment on the processing object in a processing container,
An arm portion having a plurality of arms and capable of bending and stretching; and
A fork part connected to the tip of the arm part to hold the object to be processed;
A heat shielding plate provided in a portion of the arm portion that enters the processing container;
A transport mechanism comprising: 2. The transport mechanism according to claim 1, wherein the plurality of arms include a first arm, a second arm, and a third arm, and are connected in series so that they can be bent in this order. The transport mechanism according to claim 2, wherein the heat shielding plate is provided at a tip of the second arm on the third arm side. The transport mechanism according to claim 3, wherein the heat shielding plate is provided on a lower surface side and / or a side surface side of the second arm. In a transport mechanism for transporting the processing object into and out of a processing apparatus for performing a heat treatment on the processing object in a processing container,
An arm portion having a plurality of arms and capable of bending and stretching; and
A fork part connected to the tip of the arm part to hold the object to be processed;
A heat shielding layer formed on the surface of the arm portion;
A transport mechanism comprising: 6. The transport mechanism according to claim 5, wherein the plurality of arms include a first arm, a second arm, and a third arm, and are connected in series so that they can be bent in this order. The transport mechanism according to claim 6, wherein the ceramic sprayed layer is provided on the second arm. The transport mechanism according to claim 6, wherein the ceramic sprayed layer is provided on the second arm and the third arm. The transport mechanism according to claim 7 or 8, wherein the ceramic sprayed layer is provided on a lower surface and a side surface of the second arm. The transport mechanism according to claim 8 or 9, wherein the ceramic sprayed layer is provided on the entire surface of the third arm. The transport mechanism according to claim 5, wherein a heat shielding layer is further provided on the surface of the fork portion. The heat shielding layer has such a characteristic that the radiation rate for heat rays in the wavelength range of 7 to 10 μm is larger than the radiation rate for heat rays in the wavelength range of 1 to 4 μm. The transport mechanism according to any one of claims 5 to 11, wherein the transport mechanism is characterized in that: 13. The emissivity for heat rays in the range of 7 to 10 [mu] m is greater than 66%, and the emissivity for heat rays in the range of 1 to 4 [mu] m is 66% or less. Transport mechanism. The transport mechanism according to claim 5, wherein the heat shielding layer is made of a ceramic sprayed layer. The transport mechanism according to claim 5, wherein the heat shielding layer is formed of a paint layer formed by applying a paint. In a transport mechanism for transporting the processing object into and out of a processing apparatus for performing a heat treatment on the processing object in a processing container,
An arm portion having a plurality of arms and capable of bending and stretching; and
A fork part connected to the tip of the arm part to hold the object to be processed;
A heat shielding plate provided in a portion of the arm portion that enters the processing container;
A heat shielding layer formed on the surface of the arm portion;
A transport mechanism comprising: The transport mechanism according to claim 16, wherein the plurality of arms include a first arm, a second arm, and a third arm, and are connected in series so as to be bent in this order. The transport mechanism according to claim 17, wherein the heat shielding plate is provided at a tip of the second arm on the third arm side. The transport mechanism according to claim 18, wherein the heat shielding plate is provided on a lower surface side and / or a side surface side of the second arm. The transport mechanism according to any one of claims 16 to 19, wherein the heat shielding layer is provided on the second arm. The transport mechanism according to any one of claims 16 to 19, wherein the heat shielding layer is provided on the second arm and the third arm. The transport mechanism according to claim 20 or 21, wherein the heat shielding layer is provided on a lower surface and a side surface of the second arm. The transport mechanism according to claim 21 or 22, wherein the heat shielding layer is provided on the entire surface of the third arm. The transport mechanism according to any one of claims 16 to 23, wherein a heat shielding layer is further provided on a surface of the fork portion. The heat shielding layer has such a characteristic that the radiation rate for heat rays in the wavelength range of 7 to 10 μm is larger than the radiation rate for heat rays in the wavelength range of 1 to 4 μm. The transport mechanism according to any one of claims 16 to 24, characterized in that: 26. The radiation rate for heat rays in the wavelength range of 7 to 10 [mu] m is greater than 66%, and the radiation rate for heat rays in the wavelength range of 1 to 4 [mu] m is 66% or less. Transport mechanism. 27. The transport mechanism according to claim 16, wherein the heat shielding layer is made of a ceramic sprayed layer. The transport mechanism according to any one of claims 16 to 26, wherein the heat shielding layer is formed of a paint layer formed by applying a paint. The transport mechanism according to any one of claims 1 to 26, wherein the heat shield plate is made of one material selected from the group consisting of stainless steel, aluminum, an aluminum alloy, and a ceramic material. The transport mechanism according to any one of claims 1 to 27, wherein the arm portion and the fork portion are connected by a low thermal conductive member having a low thermal conductivity.

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