JP7516147B2 - Retaining device - Google Patents

Description

This disclosure relates to a holding device.

For example, an electrostatic chuck is used as a holding device for holding a wafer during semiconductor manufacturing. The electrostatic chuck is equipped with a ceramic member having an adsorption surface and a chuck electrode provided inside the ceramic member, and uses electrostatic attraction generated by applying a voltage to the chuck electrode to adsorb and hold the wafer on the adsorption surface of the ceramic member.

If the temperature of the wafer held on the adsorption surface of the electrostatic chuck does not reach the desired temperature, the accuracy of each process on the wafer (film formation, etching, etc.) may decrease. For this reason, the electrostatic chuck needs to control the temperature of the wafer, and for example, multiple heater electrodes are provided inside the ceramic member. When a voltage is applied to each heater electrode, the heater electrodes generate heat and heat the ceramic member, and this controls the adsorption surface temperature of the ceramic member (the temperature of the wafer held on the adsorption surface) to approach the desired temperature.

For example, in the electrostatic chuck shown in FIG. 2 of JP 2019-220595 A (Patent Document 1 below), multiple heater electrode layers are disposed inside a ceramic member. The heater electrode layers are disposed inside the ceramic member below the chuck electrodes. A thermistor for measuring the temperature of the heater electrode layer is provided directly below the heater electrode layer, so that the temperature of the heater electrode layer is measured by the thermistor, and the temperature of the chucking surface is controlled based on the measured temperature.

JP 2019-220595 A

However, if a refrigerant flow path is provided in the base member, and the thermistor is installed, for example, between the refrigerant flow path and the heater electrode layer, the thermistor is strongly affected by the cooling caused by the refrigerant flow path, and the temperature detected by the thermistor is likely to be low. Thus, depending on the location of the thermistor, the error between the temperature detected by the thermistor and the temperature of the adsorption surface of the ceramic member becomes large, and it is not possible to bring the temperature of the adsorption surface of the ceramic member close to the desired temperature.

The holding device disclosed herein is a holding device that includes a holding substrate having a front surface and a back surface that are substantially perpendicular to a first direction, and a base member that is arranged on the back surface side and is capable of cooling the holding substrate, and that holds an object on the front surface of the holding substrate, the holding substrate including an insulator, a heater member having a heating element arranged inside the insulator or on the back surface, and a plurality of temperature measuring elements arranged inside the insulator, the plurality of temperature measuring elements including a first temperature measuring element and a second temperature measuring element arranged on the front surface side of the first temperature measuring element in the first direction.

According to the present disclosure, the surface temperature of the holding substrate can be brought closer to the desired temperature.

FIG. 1 is a perspective view showing a part of an electrostatic chuck according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a part of the electrostatic chuck according to the embodiment, taken in a thickness direction.

[Description of the embodiments of the present disclosure]
First, embodiments of the present disclosure will be listed and described.
(1) A holding device disclosed herein comprises a holding substrate having a front and back surfaces that are approximately perpendicular to a first direction, and a base member arranged on the back surface side and capable of cooling the holding substrate, and holds an object on the front surface of the holding substrate, wherein the holding substrate comprises an insulator, a heater member having a heating element arranged inside the insulator or on the back surface, and a plurality of temperature measuring elements arranged inside the insulator, and the plurality of temperature measuring elements include a first temperature measuring element and a second temperature measuring element arranged on the front surface side of the first temperature measuring element in the first direction.

Even if the holding substrate is at the same height in the first direction, it has areas where heat dissipation is large and areas where it is small (for example, areas where the cooling effect of the base member is large and areas where it is small). Therefore, if the first temperature measuring element and the second temperature measuring element are arranged at the areas where heat dissipation is large and small, respectively, a phenomenon may occur in which the temperature measurement results of the temperature measuring elements differ even if the surface temperature of the holding substrate is the same. For example, if the first temperature measuring element is arranged at the area where heat dissipation is small and the second temperature measuring element is arranged at the area where heat dissipation is large, the temperature measurement result of the first temperature measuring element and the temperature measurement result of the second temperature measuring element can be made closer to each other. In this way, by appropriately changing the position of the temperature measuring element in the first direction according to the degree of heat dissipation, the variation in the temperature measurement results between the multiple temperature measuring elements can be reduced. Therefore, the surface temperature of the holding substrate can be easily derived based on the temperature measurement results of the temperature measuring elements, and the surface temperature of the holding substrate can be made closer to the desired temperature.

(2) The multiple temperature measuring elements are arranged on the back surface side of the heater member in the first direction, and when the distance from the back surface to the heater member is D1 and the distance from the back surface to the temperature measuring element closest to the base member is D2, it is preferable that D2 > D1 × (1/3) is satisfied.
The area of the holding substrate closer to the base member than the heater member is easily cooled, and is therefore susceptible to the effects of heat dissipation. Therefore, by setting the distance from the back surface of the holding substrate to the temperature measuring element as described above, the temperature measuring element can be placed as far away from the base member as possible, making it less susceptible to the effects of heat dissipation.

(3) It is preferable that the holding substrate is plate-shaped and joined to the base member in the first direction, the base member has a refrigerant flow path through which a refrigerant flows, the first temperature measuring element is arranged in the first direction between an area of the base member where the refrigerant flow path is not provided and the heater member, and the second temperature measuring element is arranged in the first direction between an area of the base member where the refrigerant flow path is provided and the heater member.
It is preferable to arrange the temperature measuring element as far away as possible from the base member in places where heat is removed greatly, such as directly above the refrigerant flow path, and to arrange the temperature measuring element as close as possible to the base member in places where heat is removed little. Therefore, if the first temperature measuring element is arranged between the heater member and the region of the base member where the refrigerant flow path is not provided, and the second temperature measuring element is arranged between the heater member and the region of the base member where the refrigerant flow path is provided, the variation in the temperature measurement results can be reduced.

[Details of the embodiment of the present disclosure]
Specific examples of the holding device of the present disclosure will be described with reference to the following drawings. Note that the present disclosure is not limited to these examples, but is intended to include all modifications within the meaning and scope equivalent to the claims as defined by the claims. The electrostatic chuck 10 corresponds to the "holding substrate" in the claims, and the up-down direction corresponds to the "first direction" in the claims.

<Electrostatic chuck>
The holding device of the present disclosure is an electrostatic chuck 10 capable of adsorbing and holding a semiconductor wafer, a glass substrate, or the like (hereinafter referred to as a "wafer 80"). As shown in Fig. 2, the electrostatic chuck 10 is capable of adsorbing a wafer 80, which is a heating target (workpiece), on a chuck surface 21 facing upward in the figure, and is formed by bonding a disk-shaped ceramic substrate 20 (e.g., 300 mm in diameter x 3 mm in thickness) to a disk-shaped base member 60 (e.g., 340 mm in diameter x 20 mm in thickness) with a bonding material 70. The chuck surface 21 corresponds to the "surface" in the claims, the wafer 80 corresponds to the "target" in the claims, and the ceramic substrate 20 corresponds to the "holding substrate" in the claims.

The electrostatic chuck 10 is used as a table on which the wafer 80 is placed in a process in which etching or the like is performed using plasma in a reduced pressure chamber. The electrostatic chuck 10 has a pin insertion hole 11 formed therein that penetrates both the ceramic substrate 20 and the base member 60 in the thickness direction. A lift pin (not shown) is inserted into this pin insertion hole 11, and the wafer 80 can be separated from the chuck surface 21 by moving this lift pin.

<Ceramic substrate>
The ceramic substrate 20 has an insulator 30 made of ceramic, a heater electrode 40 disposed inside the insulator 30, and a chuck electrode 50 disposed inside the insulator 30 between the heater electrode 40 and the chuck surface 21. The heater electrode 40 and the chuck electrode 50 are arranged side by side in the thickness direction of the ceramic substrate 20, with the chuck electrode 50 located on the side closer to the chuck surface 21 and the heater electrode 40 located on the side closer to the back surface 22 located opposite the chuck surface 21. The heater electrode 40 corresponds to a "heater member" in the claims, and the back surface 22 of the ceramic substrate 20 corresponds to a "back surface" in the claims.

In the following description, the direction of the axis perpendicular to the chuck surface 21 and the back surface 22 of the ceramic substrate 20 is defined as the up-down direction. Here, perpendicular includes not only the case where the axis intersects with the top surface 34 at an angle of 90 degrees, but also the case where the axis intersects with the top surface 34 at an angle of 85 to 90 degrees.

A terminal (not shown) is connected to the chuck electrode 50. The terminal is arranged so as to penetrate the base member 60 in the vertical direction. The terminal is connected to a power source (not shown), and power from the power source can be supplied to the chuck electrode 50 through the terminal.

<Insulator>
The insulator 30 is a laminate of a plurality of ceramic layers. As shown in Fig. 2, an upper surface 34 of the insulator 30 is located below the chuck surface 21 of the ceramic substrate 20. The insulator 30 is a sintered body mainly composed of alumina, aluminum nitride, yttria, or a composite material of alumina and silicon carbide. The thermal expansion coefficient of the insulator 30 is in the range of 6 to 8 ppm/°C (e.g., 7.6 ppm/°C), and the thermal conductivity is 18 W/m·K.

<Chuck electrode>
The chuck electrode 50 is mainly composed of tungsten, molybdenum, or an alloy thereof. The chuck electrode 50 exerts an electrostatic adsorption force by applying a voltage. The electrostatic adsorption force may be a Coulomb force, a Johnsen-Rahbek force, or a gradient force. The chuck electrode 50 of the present disclosure uses a metallization in which a conductor layer formed by printing a conductor paste and sintering the conductor layer, but may also use a metal foil, a metal mesh, or the like.

<Heater electrode>
A plurality of heating elements 41 constituting the heater electrode 40 are disposed inside the insulator 30. The heating elements 41 are mainly composed of tungsten, molybdenum, an alloy thereof, or a carbide thereof. The heating elements 41 are connected to a power source via internal wiring, vias, terminals, etc. (not shown), so that power from the power source can be supplied to the heater electrode 40.

The heater electrode 40 of the present disclosure is disposed inside the insulator 30, but may also be disposed inside a heater member (polyimide heater) separate from the rear surface 22 of the ceramic substrate 20 or the insulator 30. The heating element 41 of the present disclosure uses a metallization formed by sintering a conductor layer printed with a conductor paste, but metal foil, metal mesh, etc. may also be used.

<Base member>
The base member 60 is disposed below the ceramic substrate 20. The base member 60 is mainly composed of aluminum, an aluminum alloy, a composite of metal and ceramics (Al-SiC), or ceramics (SiC). The base member 60 has a larger diameter than the ceramic substrate 20 so that the entire ceramic substrate 20 can be placed thereon. The ceramic substrate 20 is plate-shaped and is joined to the base member 60 in the up-down direction.

The base member 60 has a refrigerant flow path 61 through which a refrigerant flows, and is capable of cooling the ceramic substrate 20. An internal hole 63 for accommodating an internal connection terminal 67, a base wiring 64, and an external connection terminal 68 is provided penetrating vertically inside the base member 60 and the bonding material 70. That is, the internal hole 63 is composed of a through hole in the base member 60 and a through hole in the bonding material 70. The base member 60 has a thermal expansion coefficient in the range of 5 to 9 ppm/°C (for example, 6.9 ppm/°C), a thermal conductivity of 180 W/m·K, and a higher thermal conductivity than the insulator 30.

The internal connection terminal 67 is provided at the upper end side of the internal hole 63 including the through hole of the bonding material 70, and the external connection terminal 68 is provided at the lower end side of the internal hole 63. The internal connection terminal 67 and the external connection terminal 68 are electrically connected by the base wiring 64. The external connection terminal 68 is connected to a power source (not shown), and power from the power source can be supplied to the thermistor 90 through the external connection terminal 68, the base wiring 64, the internal connection terminal 67, and the electrode wire 95.

<Bonding material>
A bond material 70 is disposed between the upper surface 62 of the base member 60 and the rear surface 22 of the ceramic substrate 20. The bond material 70 is mainly composed of silicone resin or epoxy resin. The bond material 70 of the present disclosure uses a silicone adhesive in a paste or sheet form. The bond material 70 not only serves to bond the ceramic substrate 20 and the base member 60, but also serves to conduct heat between the ceramic substrate 20 and the base member 60 and to relieve stress caused by thermal expansion of the ceramic substrate 20 and the base member 60. Therefore, at the position of the internal hole 63, heat cannot be exchanged between the ceramic substrate 20 and the base member 60 due to the through hole of the bond material 70.

<Thermistor>
The electrostatic chuck 10 includes a thermistor 90 whose resistance value changes with temperature, and measures the temperature of the upper surface 34 of the insulator 30 by the thermistor 90. The thermistor 90 corresponds to a "temperature measuring element" in the claims, and a platinum resistance temperature measuring element or the like can be used as the "temperature measuring element" in addition to the thermistor 90. As shown in Fig. 2, the thermistor 90 is composed of a thermistor sintered body 94 and a pair of electrode wires 95 made of platinum extending from the thermistor sintered body 94. One electrode wire 95 is a positive side, and the other electrode wire 95 is a negative side.

The thermistor 90 is located between the rear surface 22 of the ceramic substrate 20 and the heater electrode 40 in the vertical direction. The insulator 30 has a recess 31 for accommodating the thermistor 90. The recess 31 is recessed upward from the rear surface 22 of the ceramic substrate 20. The thermistor 90 is attached to the bottom surface (upper surface) 32 of the recess 31, and resin 33 is embedded in the recess 31 to be resin-sealed. The lower surface of the resin 33 is arranged to be flush with the rear surface 22 of the ceramic substrate 20. Therefore, the resin 33 and the bonding material 70 are joined to each other without any gaps.

The thermistor 90 of the present disclosure includes a first thermistor 91, a second thermistor 92, and a third thermistor 93. The second thermistor 92 is located directly above the refrigerant flow path 61. The third thermistor 93 is located near the internal connection terminal 67. The thermistors 91, 92, and 93 are aligned horizontally in a parallel arrangement with the rear surface 22 of the ceramic substrate 20, and the first thermistor 91 is located between the second thermistor 92 and the third thermistor 93 in the horizontal direction.

The refrigerant flow path 61 is not formed below the second thermistor 92 in the base member 60, and the first thermistor 91 is disposed between the heater electrode 40 and an area 65 of the base member 60 where the refrigerant flow path 61 is not provided. On the other hand, the second thermistor 92 is disposed between the heater electrode 40 and an area 66 of the base member 60 where the refrigerant flow path 61 is provided. The first thermistor 91 is located farther from the internal connection terminal 67 than the third thermistor 93 in the horizontal direction.

The area around the refrigerant flow path 61 in the base member 60 is a location where heat is removed more by the refrigerant flow path 61, and is likely to become colder than other areas. The second thermistor 92 is disposed closer to the refrigerant flow path 61 in the horizontal direction than the first thermistor 91, and therefore is likely to become colder than the first thermistor 91 if it were at the same height as the first thermistor 91.

In addition, the area around the internal connection terminal 67 in the base member 60 has a through hole formed in the bonding material 70, which prevents heat from being exchanged between the ceramic substrate 20 and the base member 60, and the air layer in the internal hole 63 does not easily transfer heat, so this area has low heat dissipation and is prone to becoming hotter than other areas. The third thermistor 93 is positioned closer to the internal connection terminal 67 in the horizontal direction than the first thermistor 91, so if it were at the same height as the first thermistor 91, it would be prone to becoming hotter than the first thermistor 91.

The thermistors 91, 92, and 93 of the present disclosure are arranged at different positions in the vertical direction. The second thermistor 92 is located closer to the chuck surface 21 of the ceramic substrate 20 than the first thermistor 91 in the vertical direction. In this way, the second thermistor 92 has a weaker degree of heat dissipation, so that it is possible to prevent the temperature from becoming lower than other parts. Furthermore, the third thermistor 93 is located closer to the back surface 22 of the ceramic substrate 20 than the first thermistor 91 in the vertical direction. In this way, the third thermistor 93 has a stronger degree of heat dissipation, so that it is possible to prevent the temperature from becoming higher than other parts.

Each of the thermistors 91, 92, and 93 is disposed closer to the rear surface 22 of the ceramic substrate 20 than the heater electrode 40 in the vertical direction. If the distance from the rear surface 22 of the ceramic substrate 20 to the heater electrode 40 is D1, and the distance from the rear surface 22 of the ceramic substrate 20 to the third thermistor 93 closest to the base member 60 is D2, then the relational expression D2>D1×(1/3) is satisfied. Since the first thermistor 91 and the second thermistor 92 are located closer to the chuck surface 21 of the ceramic substrate 20 than the third thermistor 93, the first thermistor 91 and the second thermistor 92 also satisfy the above relational expression. According to the above relational expression, each of the thermistors 91, 92, and 93 can be disposed as far away as possible from the base member 60, and the effect of heat extraction by the base member 60 can be reduced.

<Effects of this embodiment>
As described above, the electrostatic chuck 10 of the present embodiment is an electrostatic chuck 10 comprising: a ceramic substrate 20 having a chuck surface 21 and a back surface 22 that are substantially perpendicular to the up-down direction; and a base member 60 that is disposed on the back surface 22 side and is capable of cooling the ceramic substrate 20. The electrostatic chuck 10 holds a wafer 80 on the chuck surface 21 of the ceramic substrate 20. The ceramic substrate 20 is provided with an insulator 30, a heater electrode 40 having a heating element 41 that is disposed inside the insulator 30 or on the back surface 22, and a plurality of thermistors 90 that are disposed inside the insulator 30. The plurality of thermistors 90 include a first thermistor 91 and a second thermistor 92 that is disposed closer to the chuck surface 21 side than the first thermistor 91 in the up-down direction.

Even if the ceramic substrate 20 is at the same height in the vertical direction, it has areas where heat dissipation is large and areas where it is small (for example, areas where the cooling effect of the base member 60 is large and areas where it is small). Therefore, if the first thermistor 91 and the second thermistor 92 are arranged at the areas where heat dissipation is large and small, respectively, a phenomenon may occur in which the temperature measurement results of the thermistor 90 differ even if the surface temperature of the ceramic substrate 20 is the same. For example, if the first thermistor 91 is arranged at an area where heat dissipation is small and the second thermistor 92 is arranged at an area where heat dissipation is large, the temperature measurement results of the first thermistor 91 and the temperature measurement results of the second thermistor 92 can be made closer to each other. In this way, by appropriately changing the position of the thermistor 90 in the vertical direction according to the degree of heat dissipation, the variation in the temperature measurement results between the multiple thermistors 91, 92, and 93 can be reduced. Therefore, the surface temperature of the ceramic substrate 20 can be easily derived based on the temperature measurement results of the thermistor 90, and the surface temperature of the ceramic substrate 20 can be made closer to the desired temperature.

The multiple thermistors 91, 92, 93 are arranged on the back surface 22 side of the heater electrode 40 in the vertical direction, and when the distance from the back surface 22 to the heater electrode 40 is D1 and the distance from the back surface 22 to the third thermistor 93 that is closest to the base member 60 is D2, it is preferable that D2 > D1 × (1/3) is satisfied.
The region of the ceramic substrate 20 closer to the base member 60 than the heater electrode 40 is easily cooled, and is therefore susceptible to the effects of heat dissipation. Therefore, by setting the distance from the rear surface 22 of the ceramic substrate 20 to the thermistor 90 as described above, the thermistor 90 can be located as far away from the base member 60 as possible, and the region can be made less susceptible to the effects of heat dissipation.

The ceramic substrate 20 is plate-shaped and is joined to a base member 60 in the vertical direction. The base member 60 has a refrigerant flow path 61 through which a refrigerant flows. The first thermistor 91 is preferably arranged in the vertical direction between a region 65 of the base member 60 where the refrigerant flow path 61 is not provided and the heater electrode 40, and the second thermistor 92 is preferably arranged in the vertical direction between a region 66 of the base member 60 where the refrigerant flow path 61 is provided and the heater electrode 40.
It is preferable to arrange the thermistor 90 as far away as possible from the base member 60 in locations where heat dissipation is large, such as directly above the refrigerant flow path 61, and to arrange the thermistor 90 as close as possible to the base member 60 in locations where heat dissipation is small. Therefore, if the first thermistor 91 is arranged between the heater electrode 40 and an area 65 of the base member 60 where the refrigerant flow path 61 is not provided, and the second thermistor 92 is arranged between the heater electrode 40 and an area 66 of the base member 60 where the refrigerant flow path 61 is provided, the variation in the temperature measurement results can be reduced.

<Other embodiments>
(1) In the above embodiment, the electrostatic chuck 10 is used to hold the wafer 80 by the chuck electrode 50. However, the present invention may be applied to a holding device that physically holds an object by means of a clamp or the like.

(2) In the above embodiment, the arrangement of the thermistor 90 is exemplified as one that satisfies the relationship D2>D1×(1/3), but it may also be one that satisfies the relationship D2>D1×(1/4).

(3) In the above embodiment, cooling by the refrigerant flow path 61 was given as an example of a factor that increases heat removal, but cooling by air cooling with cooling fins may also be used.

(4) In the above embodiment, the air layer in the internal hole 63 is given as an example of a factor that reduces heat dissipation, but an air layer other than the internal hole 63 may also be used.

(5) In the above embodiment, the height of the thermistor 90 is determined by the arrangement of the refrigerant flow path 61 and the internal connection terminal 67. However, the height of the thermistor 90 may be determined by observing the temperature distribution of the base member 60 through a simulation. In addition, the height of the thermistor 90 may be determined by actually measuring the degree of heat dissipation.

(6) In the above embodiment, the thermistor 90 is positioned below the heater electrode 40, but the thermistor 90 may be positioned between the heater electrode 40 and the chuck electrode 50. By positioning the thermistor 90 above the heater electrode 40, it is less susceptible to the effect of heat dissipation by the base member 60, and temperature variation can be further reduced. Therefore, the temperature measurement result can be fine-tuned by changing the height of the thermistor 90.

(7) In the above embodiment, the temperature measurement result is fine-tuned by changing the height of the thermistor 90. However, the temperature measurement result may also be fine-tuned by changing the position of the thermistor 90 in the horizontal direction (XY direction) as well as the height of the thermistor 90.

10: electrostatic chuck (holding device) 11: pin insertion hole 20: ceramic substrate (holding substrate) 21: chuck surface (front surface) 22: back surface 30: insulator 31: recess 32: bottom surface 33: resin 34: top surface 40: heater electrode (heater member) 41: heating element 50: chuck electrode 60: base member 61: coolant flow path 62: top surface 63: internal hole 64: base wiring 65: area where coolant flow path is not provided 66: area where coolant flow path is provided 67: internal connection terminal 68: external connection terminal 70: bonding material 80: wafer (target object)
90: Thermistor (temperature measuring element) 91: First thermistor (first temperature measuring element) 92: Second thermistor (second temperature measuring element) 93: Third thermistor (third temperature measuring element) 94: Thermistor sintered body 95: Electrode wire D1: Distance from the back surface to the heater electrode D2: Distance from the back surface to the third thermistor

Claims (3)

a holding substrate having a front surface and a back surface substantially perpendicular to a first direction;
a base member disposed on the rear surface side and capable of cooling the holding substrate; and a holding device for holding an object on the front surface of the holding substrate,
the holding substrate includes an insulator, a heater member having a heating element disposed inside the insulator or on the back surface thereof, and a plurality of temperature measuring elements disposed inside the insulator;
the plurality of temperature measuring elements include a first temperature measuring element and a second temperature measuring element arranged closer to the front surface than the first temperature measuring element in the first direction;
the holding substrate is plate-shaped and joined to the base member in the first direction,
The base member has a coolant flow path through which a coolant flows,
the first temperature measuring element is disposed between a region of the base member in which the refrigerant flow path is not provided and the heater member in the first direction;
A holding device , wherein the second temperature measuring element is disposed between a region of the base member in which the refrigerant flow path is provided and the heater member in the first direction . a holding substrate having a front surface and a back surface substantially perpendicular to a first direction;
a base member having a through hole penetrating in the first direction, the base member being disposed on the rear surface side and capable of cooling the holding substrate;
A holding device that holds an object on the surface of the holding substrate, the holding device comprising : a through hole that is connected to the through hole of the base member; and a bonding material that bonds the holding substrate and the base member, the holding device comprising:
the holding substrate includes an insulator, a heater member having a heating element disposed inside the insulator or on the back surface thereof, and a plurality of temperature measuring elements disposed inside the insulator;
the plurality of temperature measuring elements include a third temperature measuring element and a first temperature measuring element arranged closer to the front surface than the third temperature measuring element in the first direction;
an internal hole is formed by the through hole of the base member and the through hole of the bonding material;
A holding device , wherein the third temperature measuring element is arranged at a position closer to the internal hole than the first temperature measuring element in a direction perpendicular to the first direction. the plurality of temperature measuring elements are disposed on the rear surface side of the heater member in the first direction,
The holding device of claim 1 or claim 2, wherein when the distance from the back surface to the heater member is D1 and the distance from the back surface to the temperature measuring element closest to the base member is D2, D2 > D1 x (1/3) is satisfied.

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