Holding device

Abstract

To provide a holding device capable of improving temperature uniformity across a holding surface.SOLUTION: In an electrostatic chuck 1 for holding a semiconductor wafer W on a holding surface 11 that includes: a holding surface 11; a lower surface 12 provided on the opposite side of the holding surface 11 in the thickness (Z-axis) direction; a heater electrode 60 disposed between the holding surface 11 and the lower surface 12; and resistors 81-84 connected to the heater electrode 60, the heater electrode 60 includes a plurality of heat-generating parts 61-64 connected in series, the resistors 81-84 are elements which have a resistance temperature coefficient greater than that of the heat-generating parts 61-64, and whose resistance values decrease as the temperature increases, and are connected in parallel with the respective heat-generating parts 61-64.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a holding device for holding and heating an object. [Background technology]

[0002] In a semiconductor manufacturing process, an electrostatic chuck (holding device) is used to hold a semiconductor wafer and heat it to a desired temperature. For example, an electrostatic chuck of this type is known, as described in Patent Document 1. This electrostatic chuck includes a ceramic member (plate-shaped member) that holds an object on its attraction surface (holding surface), and a metal base member bonded to the ceramic member, and a chuck electrode and a heater electrode are disposed inside the ceramic member.

[0003] In this electrostatic chuck, an object is held on the attraction surface by generating an electrostatic force using a chuck electrode, and temperature control is performed so that the temperature distribution of the object held on the attraction surface is uniform by cooling the ceramic member using a base member and heating the ceramic member using a heater electrode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-125636 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the electrostatic chuck, the heater electrode is produced by screen printing. The heater electrode is formed in a concentric pattern. However, in screen printing, it is difficult to print the concentric pattern with a uniform thickness due to printing bleeding, mesh marks due to a screen mask, and the like, and thus there are portions with a thin or thick thickness.

[0006] For this reason, heater electrodes manufactured by screen printing are prone to variations in thickness and width, and there is a risk that parts of the same circuit will have a different resistance value per unit length than other parts. If parts with different resistance values ​​are produced, for example, parts with high resistance will have less current and less heat generation, while parts with low resistance will have more current and more heat generation, resulting in a deterioration in the uniformity (thermal uniformity) of the temperature distribution on the adsorption surface (holding surface).

[0007] Therefore, the present disclosure has been made to solve the above-mentioned problems, and has an object to provide a holding device that can improve thermal uniformity on the holding surface. [Means for solving the problem]

[0008] In order to solve the above problems, one aspect of the present disclosure is to A holding device for holding an object on a first surface, a second surface provided on an opposite side to the first surface in a thickness direction, a heater electrode disposed between the first surface and the second surface, and a resistor connected to the heater electrode, comprising: The heater electrode includes a plurality of heat generating portions connected in series, The resistors are elements having a resistance temperature coefficient larger than that of the heat generating parts, and a resistance value that decreases as the temperature increases, and are characterized in being connected in parallel to each of the heat generating parts.

[0009] This holding device is equipped with a plurality of heat generating parts connected in series to heater electrodes. The resistors connected to the heater electrodes are elements whose resistance temperature coefficient is larger than that of the heat generating parts and whose resistance value decreases as the temperature increases, and are connected in parallel to each heat generating part. Therefore, when there is a variation in the amount of heat generated by each heat generating part, the resistance value of the resistors connected in parallel will decrease in the heat generating part whose temperature is higher than the others.

[0010] Therefore, in the heat generating portion whose temperature is higher than the others, the current flowing through the resistor increases and the current flowing through the heat generating portion decreases, so the amount of heat generated in the heat generating portion decreases to the same temperature as the other heat generating portions. As a result, the temperatures of the heat generating portions become almost equal, making it possible to make the temperature distribution on the first surface uniform.

[0011] In addition, even if the uniformity of temperature on the first surface is deteriorated due to heat input to the object, the temperature is adjusted in each heat generating portion in the same manner as described above. Therefore, even if heat is input to the object, the temperature distribution on the first surface can be kept uniform.

[0012] Another aspect of the present disclosure made to solve the above problem is: A holding device for holding an object on a first surface, a second surface provided on an opposite side to the first surface in a thickness direction, a heater electrode disposed between the first surface and the second surface, and a resistor connected to the heater electrode, comprising: The heater electrode includes a plurality of heat generating portions connected in parallel, The resistors are elements having a resistance temperature coefficient larger than that of the heat generating parts, and a resistance value that increases as the temperature rises, and are characterized in being connected in series to the heat generating parts.

[0013] This holding device is equipped with a plurality of heat generating parts with heater electrodes connected in parallel. The resistors connected to the heater electrodes are elements with a resistance temperature coefficient larger than that of the heat generating parts and whose resistance value increases as the temperature rises, and are connected in series to each heat generating part. Therefore, when there is a variation in the amount of heat generated by each heat generating part, the resistance value of the resistors connected in series increases in the heat generating part whose temperature is higher than the others.

[0014] Therefore, in the heat generating portion where the temperature is higher than the others, the current flowing through the resistor and the heat generating portion where the temperature has risen decreases, so the amount of heat generated in the heat generating portion decreases and the temperature drops to the same level as the other heat generating portions. As a result, the temperatures of the heat generating portions become almost equal, making it possible to make the temperature distribution on the first surface uniform.

[0015] In addition, even if the uniformity of temperature on the first surface is deteriorated due to heat input to the object, the temperature is adjusted in each heat generating portion in the same manner as described above. Therefore, even if heat is input to the object, the temperature distribution on the first surface can be kept uniform.

[0016] In the holding device according to the above embodiment, The resistor is preferably an NTC thermistor.

[0017] By using an NTC thermistor as a resistor in this manner, the resolution is improved, and the temperature (current) can be adjusted more precisely so that the temperature (heat generation) of each heating element is uniform, thereby further improving the thermal uniformity on the first surface.

[0018] In the above-mentioned alternative holding device, The resistor is preferably a PTC thermistor.

[0019] By using a PTC thermistor as a resistor in this manner, the resolution is improved, and the temperature (current) can be adjusted more precisely so that the temperature (heat generation) of each heating element is uniform, thereby further improving the thermal uniformity on the first surface.

[0020] In any one of the above-mentioned holding devices, It is preferable that the number of the heat generating parts supplied with power from one external power source is 10 or less.

[0021] Here, by providing an external power source for each heat generating part, the amount of heat generated in each heat generating part can be controlled with high precision, and the amount of heat generated can be made uniform. By providing many heat generating parts with uniform heat generation, the temperature uniformity on the first surface can be improved. However, providing many heat generating parts in this way increases the number of external power sources required, which increases the equipment costs.

[0022] In contrast, in this holding device, because power is supplied to multiple heat generating parts from a single external power source, the number of external power sources required can be reduced even if many heat generating parts are provided. On the other hand, if there are only a few external power sources, it is difficult to control the amount of heat generated in each heat generating part with high precision, and there is a risk that the amount of heat generated in each heat generating part cannot be made uniform.

[0023] However, in this holding device, as described above, the temperature (current) is adjusted so that the temperature (calorific value) is uniform in each heat generating part. Here, if there are many heat generating parts (more than 10) that are powered from one external power source, the temperature difference between the heat generating parts will vary greatly, the time it takes for the temperature to become uniform will increase, and so on, resulting in a decrease in the accuracy of temperature (calorific value) adjustment in each heat generating part. For this reason, in this holding device, the number of heat generating parts that are powered from one external power source is set to 10 or less. This allows the temperature (calorific value) adjustment in each heat generating part to be performed accurately in a short time. Therefore, the amount of heat generated in many heat generating parts can be made uniform with a small number of external power sources, and the temperature uniformity in the first surface can be improved without increasing equipment costs. Effect of the Invention

[0024] According to the present disclosure, it is possible to provide a holding device capable of improving the thermal uniformity on the holding surface. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic perspective view of an electrostatic chuck according to a first embodiment. [Diagram 2] 2 is a partial cross-sectional view showing a part of an XZ cross section of the electrostatic chuck according to the first embodiment. FIG. [Diagram 3] FIG. 4 is a diagram showing the shape of a heater electrode. [Figure 4] FIG. 2 is a diagram showing a connection form between a heat generating portion and an NTC thermistor. [Diagram 5] FIG. 1 is a diagram showing a circuit configuration of a heater electrode at room temperature in a conventional electrostatic chuck. [Figure 6]FIG. 1 is a diagram showing a circuit configuration of a heater electrode after heating in a conventional electrostatic chuck. [Figure 7] FIG. 2 is a diagram showing a circuit configuration of a heater electrode at room temperature in the electrostatic chuck of the first embodiment. [Figure 8] FIG. 4 is a diagram showing a circuit configuration of a heater electrode after a temperature rise in the electrostatic chuck of the first embodiment. [Figure 9] 10 is a diagram showing a connection form between a heat generating portion and a PTC thermistor in an electrostatic chuck according to a second embodiment. FIG. [Figure 10] FIG. 11 is a diagram showing a circuit configuration of a heater electrode at room temperature in an electrostatic chuck according to a second embodiment. [Figure 11] FIG. 11 is a diagram showing a circuit configuration of a heater electrode after a temperature rise in an electrostatic chuck according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] A holding device according to an embodiment of the present disclosure will be described in detail with reference to the drawings. In this embodiment, the holding device will be described by taking as an example an electrostatic chuck used in a semiconductor manufacturing device such as a film forming device (such as a CVD film forming device or a sputtering film forming device) or an etching device (such as a plasma etching device).

[0027] (First embodiment) An electrostatic chuck 1 according to a first embodiment will now be described with reference to Fig. 1 to Fig. 4. The electrostatic chuck 1 according to this embodiment is a device that attracts and holds a semiconductor wafer W (object) by electrostatic attraction, and is used, for example, to fix the semiconductor wafer W in a vacuum chamber of a semiconductor manufacturing device. As shown in Fig. 1, the electrostatic chuck 1 has a plate-shaped member 10, a base member 20, and a bonding layer 30 that bonds the plate-shaped member 10 and the base member 20 together.

[0028] In the following description, for convenience of explanation, the X, Y and Z axes are defined as shown in Fig. 1. Here, the Z axis is an axis in the axial direction of the electrostatic chuck 1 (the vertical direction in Fig. 1) and is an example of the "thickness direction" in the present disclosure. The X and Y axes are axes in the radial direction of the electrostatic chuck 1.

[0029] As shown in Fig. 1, the plate-shaped member 10 is a disk-shaped member and is made of ceramics. Specifically, the plate-shaped member 10 has a stepped disk shape in which two disks of different diameters are overlapped with a common central axis (more specifically, a disk-shaped upper stage portion 10a having a smaller diameter is overlapped on a disk-shaped lower stage portion 10b having a larger diameter). In this way, the lower stage portion 10b is provided on the opposite side of the holding surface 11 side with respect to the upper stage portion 10a in the thickness direction of the plate-shaped member 10 (a direction that coincides with the Z-axis direction, a vertical direction), and has a larger outer periphery than the upper stage portion 10a when viewed from the thickness direction of the plate-shaped member 10.

[0030] Although various ceramics are used as the ceramics, it is preferable to use ceramics mainly composed of aluminum oxide (alumina, Al2O3) or aluminum nitride (AlN) from the viewpoints of strength, wear resistance, plasma resistance, etc. The main component here means the component with the highest content (for example, a component with a volume content of 90 vol% or more).

[0031] 1 and 2, the plate-shaped member 10 has a holding surface 11 (upper surface) that holds a semiconductor wafer W, and a lower surface 12 provided on the opposite side to the holding surface 11 in the thickness direction (i.e., the Z-axis direction) of the plate-shaped member 10. In this embodiment, the upper portion 10a has the holding surface 11, and the semiconductor wafer W is held on the holding surface 11. Note that the holding surface 11 is an example of a "first surface" in the present disclosure, and the lower surface 12 is an example of a "second surface" in the present disclosure.

[0032] Here, the diameter of the plate-shaped member 10 is larger at the lower portion 10b than at the upper portion 10a, and the upper portion 10a has a diameter of, for example, about 150 mm to 300 mm, while the lower portion 10b has a diameter of, for example, about 180 mm to 400 mm. The thickness of the plate-shaped member 10 is, for example, about 2 mm to 6 mm. The thermal conductivity of the plate-shaped member 10 is preferably within a range of 10 W / mK to 50 W / mK (more preferably, 18 W / mK to 30 W / mK).

[0033] As shown in Fig. 2, the plate-like member 10 has a heater electrode 60 therein. This heater electrode 60 is disposed on the holding surface 11 side. The heater electrode 60 has a plurality of heat generating parts 61-64 formed in the planar (XY) direction as shown in Figs. 3 and 4. In this embodiment, as shown in Fig. 3, the heat generating part 61 in a spiral pattern is disposed on the inner periphery side, and the heat generating parts 62-64 in an arc-shaped pattern are disposed on the outer periphery side. That is, three heat generating parts 62-64 are disposed around the heat generating part 61.

[0034] As shown in Fig. 4, these heat generating parts 61-64 are connected in series and are supplied with power from a single external power source. The heat generating parts 61-64 (heater electrodes 60) are made of a conductive material (e.g., tungsten or molybdenum). Specifically, the heat generating parts 61-64 (heater electrodes 60) are formed by screen printing using metallized ink. When power is supplied to the heat generating parts 61-64 (heater electrodes 60) from the external power source, the heat generating parts 61-64 generate heat and heat the semiconductor wafer W held on the holding surface 11.

[0035] NTC thermistors 81-84 are connected in parallel to the heat generating parts 61-64, respectively. In detail, NTC thermistor 81 is connected in parallel to heat generating part 61, NTC thermistor 82 is connected in parallel to heat generating part 62, NTC thermistor 83 is connected in parallel to heat generating part 63, and NTC thermistor 84 is connected in parallel to heat generating part 64. Each of NTC thermistors 81-84 is an electronic component (resistor) having a resistance temperature coefficient larger than that of heat generating parts 61-64 and a resistance value that decreases as the temperature increases, and for example, is a semiconductor ceramic whose main component is ceramics and in which oxides of manganese, nickel, cobalt, etc. are mixed and sintered, with electrodes provided on the semiconductor ceramic. Note that NTC thermistors 81-84 are the same, and their resistance values ​​are sufficiently larger than those of heat generating parts 61-64.

[0036] Furthermore, if the resistance value of the NTC thermistors 81-84 is not sufficiently higher than the resistance value of the heat generating parts 61-64, a resistor for suppressing voltage and current may be connected in series to the NTC thermistors 81-84 to provide a resistor with a sufficiently high resistance value relative to the heat generating parts 61-64. The resistor connected in series to the NTC thermistors 81-84 may be disposed on the lower surface 12 side of the plate-like member 10, similar to the NTC thermistors 81-84.

[0037] The plate-like member 10 is provided with a chuck electrode (not shown) between the holding surface 11 and the heater electrode 60, and by supplying power to the chuck electrode to generate electrostatic attraction, the semiconductor wafer W can be held on the holding surface 11 by the electrostatic attraction.

[0038] 1, the base member 20 is disposed on the side opposite to the holding surface 11 with respect to the plate-like member 10. The base member 20 is formed, for example, in a cylindrical shape. The base member 20 is formed, for example, from a metal (for example, aluminum or an aluminum alloy), but may be formed from a material other than metal.

[0039] 1 and 2, the base member 20 has an upper surface 21 and a lower surface 22 provided on the opposite side to the upper surface 21 in the thickness direction (i.e., the Z-axis direction) of the base member 20. The upper surface 21 of the base member 20 is thermally connected to the lower surface 12 of the plate-like member 10 via a bonding layer 30.

[0040] The diameter of the base member 20 is, for example, about 180 mm to 400 mm. The thickness (dimension in the Z-axis direction) of the base member 20 is, for example, about 20 mm to 50 mm. The thermal conductivity of the base member 20 (assumed to be aluminum) is desirably within the range of 160 mm to 250 W / mK (preferably, about 230 W / mK).

[0041] Further, a coolant flow passage 23 for flowing a coolant (e.g., a fluorine-based inert liquid, water, etc.) is formed in the base member 20. By flowing a coolant in this coolant flow passage 23, the base member 20 is cooled, and the plate-like member 10 is cooled via the bonding layer 30. This allows the semiconductor wafer W held on the holding surface 11 to be cooled, and by heating with the heater electrode 60, the electrostatic chuck 1 allows the temperature of the semiconductor wafer W to be controlled.

[0042] As shown in Figs. 1 and 2, the bonding layer 30 is disposed between the lower surface 12 of the plate-like member 10 and the upper surface 21 of the base member 20, and bonds the plate-like member 10 and the base member 20 in a heat-transferable manner. The bonding layer 30 is made of a resin adhesive such as silicone resin, acrylic resin, or epoxy resin. The thickness (dimension in the Z-axis direction) of the bonding layer 30 is, for example, about 0.1 mm to 1.5 mm. The thermal conductivity of the bonding layer 30 is, for example, 1.0 W / mK. The thermal conductivity of the bonding layer 30 (assuming a silicone resin) is desirably within a range of 0.1 W / mK to 2.0 W / mK (preferably, 0.5 W / mK to 1.5 W / mK).

[0043] Here, since the heating parts 61 to 64 (heater electrodes 60) are formed by screen printing, it is difficult to print with a uniform thickness due to printing bleeding, mesh marks caused by the screen mask, and the like. Therefore, in each of the heating parts 61 to 64, there may be portions where the thickness is locally thin or thick, resulting in variations in thickness and width. When such variations occur, portions with different resistance values per unit length are formed locally, and the resistance value of that heating part will not be the same as the resistance values of other heating parts.

[0044] When heating parts with different resistance values are formed in this way, an electric circuit as shown in FIG. 5 is configured. Here, for the sake of simplicity of explanation, a case where there are two heating parts is assumed. In FIG. 5, R1, R2 (R1 < R2) are the resistance values at normal temperature (temperature T), I is the current value, and V is the voltage value. Here, the power W1, W2 applied to R1, R2 are W1 = R1·I 2 , and the power W2 applied to R2 = R2·I 2 becomes. At this time, if the temperatures after the change (after temperature rise) due to power supply are T1, T2, then since the temperature is proportional to the power, T1 = α·W1, T2 = α·W2 (α is a constant).

[0045] And since R1 < R2, W1 < W2, and T1 < T2. If the resistance values in each heating part after the temperature change (temperature rise) are R1', R2', then as shown in FIG. 6, the resistance values R1', R2' are R1' = R1 + R1·A·T1 R2' = R2 + R2·A·T2 become. Here, A is the temperature coefficient of resistance of the heater electrode (heating part), and I' is the current value after temperature rise.

[0046] That is, in the heat generating portion where the resistance value has increased, the temperature after the temperature rise becomes higher, and the variation in the resistance value due to the temperature change determined by the resistance temperature coefficient also becomes larger. As a result, the difference between the two resistance values further expands due to the temperature rise (heat generation in the heat generating portion). Due to this variation in the resistance value, the temperature difference in the heat generating portion further widens. Therefore, in the conventional electrostatic chuck, when heating is performed by the heater electrode, it will exacerbate the deterioration of the uniformity (isothermal property) of the temperature distribution on the holding surface 11 caused by the variations in thickness and width that occur during screen printing.

[0047] Therefore, in the electrostatic chuck 1 of the present embodiment, in the heater electrode 60, each of the heat generating portions 61 to 64 is connected in series, and NTC thermistors 81 to 84 are connected in parallel to each of the heat generating portions 61 to 64. As shown in FIG. 7, assuming that the resistance values of the heat generating portions 61 to 64 are R1 to R4 and the resistance values of the NTC thermistors 81 to 84 are r, since the resistance value r is sufficiently larger than the resistance values R1 to R4 (r >> R), the powers W1 to W4 applied to the heat generating portions 61 to 64 are W1 = R1·I 2 , W2 = R2·I 2 , W3 = R3·I 2 , W4 = R4·I 2 where R1 to R4 are the resistance values at normal temperature (temperature T), I is the current value, and V is the voltage value.

[0048] Here, for the sake of simplicity of explanation, for example, assume that the resistance value R2 of the heat generating portion 62 is larger than those of the other heat generating portions 61, 63, 64 (assuming that the resistance values of the heat generating portions 61, 63, 64 are the same) (R1 = R3 = R4 < R2). At this time, the temperatures T1 to T4 of the heat generating portions 61 to 64 changed by power supply are such that since the temperature is proportional to the power, when R1 = R3 = R4 < R2, T1 = T3 = T4 < T2.

[0049] The increase in resistance value due to the temperature rise in these heating parts 61 to 64 is R1·A·T1, R2·A·T2, R3·A·T3, and R4·A·T4 respectively. Since T1 = T3 = T4 < T2, the increase in resistance value in the heating part 62 is larger than the increase in resistance value in the other heating parts 61, 63, and 64 (the increase in resistance value of these heating parts is the same). Here, A is the resistance temperature coefficient of the heater electrode (heating part).

[0050] And since the resistance values of the NTC thermistors 81 to 84 decrease as the temperature rises, the resistance value variation due to temperature becomes a negative value. So, the respective resistance value variations are -r·B·T1, -r·B·T2, -r·B·T3, and -r·B·T4. Since T1 = T3 = T4 < T2, the resistance value variation in the NTC thermistor 82 is larger than the resistance value variations in the other NTC thermistors 81, 83, and 84 (the resistance value variations of these NTC thermistors are the same). Here, B is the resistance temperature coefficient of the NTC thermistor.

[0051] In this way, in the heating part 62 where the temperature is higher than that of the other heating parts 61, 63, and 64, the decrease in the resistance value of the NTC thermistor 82 is larger than that of the others. Therefore, the current flowing through the NTC thermistor 82 increases, and the current flowing through the heating part 62 decreases. That is, the current flowing through the heating part 62, which is higher in temperature than the other heating parts 61, 63, and 64, becomes smaller, the temperature automatically drops, and it becomes almost the same temperature as the other heating parts 61, 63, and 64. And since such temperature adjustment is performed among the heating parts 61 to 64, the temperatures in the heating parts 61 to 64 can be made uniform.

[0052] Here, if a large number of heat generating parts (for example, more than 10 parts) are connected to one external power source, the accuracy of the above-mentioned automatic temperature adjustment may decrease, for example, because the temperature difference between the heat generating parts may vary widely or the time required for the temperature to become uniform may become longer. Therefore, in the present disclosure, the number of heat generating parts powered by one external power source is set to 10 or less (four in this embodiment) so that the above-mentioned automatic temperature adjustment can be performed with high accuracy. This allows the temperature in each of the heat generating parts 61 to 64 to be uniform with high accuracy, thereby improving the temperature uniformity on the holding surface 11.

[0053] In addition, even if the heat input to the semiconductor wafer W deteriorates the thermal uniformity on the holding surface 11 during various process treatments on the semiconductor wafer W, the above-mentioned automatic temperature control function automatically adjusts the temperature in each of the heat generating parts 61 to 64, so that the temperature distribution on the holding surface 11 can be maintained uniform.

[0054] As described above, according to the electrostatic chuck 1 of the present embodiment, by connecting the NTC thermistors 81-84 in parallel to the heat generating parts 61-64, respectively, which are connected in series, it is possible to automatically adjust the temperature in each of the heat generating parts 61-64 uniformly. Therefore, it is possible to improve the temperature uniformity on the holding surface 11.

[0055] [Second embodiment] Next, a second embodiment will be described. In the second embodiment, the basic configuration is the same as in the first embodiment, but the method of connecting the heat generating parts 61 to 64 and the type of thermistor are different. Therefore, the same reference numerals are used for the same configuration as in the first embodiment, and the description is omitted as appropriate, and the differences from the first embodiment will be mainly described.

[0056] In the electrostatic chuck according to the second embodiment, as shown in FIG. 9, the heating units 61 to 64 are connected in parallel and are powered by one external power supply. And, PTC thermistors 91 to 94 are connected in series to the respective heating units 61 to 64. Specifically, the PTC thermistor 91 is connected in series to the heating unit 61, the PTC thermistor 92 is connected in series to the heating unit 62, the PTC thermistor 93 is connected in series to the heating unit 63, and the PTC thermistor 94 is connected in series to the heating unit 64. Each of the PTC thermistors 91 to 94 is an electronic component (resistor) having a resistance temperature coefficient smaller than that of each of the heating units 61 to 64 and whose resistance value increases as the temperature rises. Note that the PTC thermistors 91 to 94 are the same.

[0057] As shown in FIG. 10, assuming that the resistance values of the heating units 61 to 64 are R1 to R4 and the resistance values of the PTC thermistors 91 to 94 are r, the powers W1 to W4 applied to the heating units 61 to 64 are W1 = V 2 / (R1 + r), W2 = V 2 / (R2 + r), W3 = V 2 / (R3 + r), W4 = V 2 / (R4 + r).

[0058] Here, for the sake of simplicity of explanation, for example, assume that the resistance value R2 of the heating unit 62 is larger than that of the other heating units 61, 63, 64 (the resistance values of the heating units 61, 63, 64 are the same) (R1 = R3 = R4 < R2). In this case, the relationship of the powers W1 to W4 applied to the heating units 61 to 64 is W2 < W1 = W3 = W4. And, the temperatures T1 to T4 of the respective heating units 61 to 64 changed by the power supply are T2 < T1 = T3 = T4. That is, when the heater electrode 60 is heated, the temperature in the heating unit 62 becomes lower than the temperatures of the other heating units 61, 63, 64.

[0059] And the increase in resistance value due to the temperature rise in the heating parts 61 to 64 is R1·A·T1, R2·A·T2, R3·A·T3, R4·A·T4 respectively. However, since R2 > R1(=R3 = R4) and T2 < T1(=T3 = T4), it is unclear which is larger between R2·A·T2 and R1·A·T1(=R3·A·T3 = R4·A·T4). Here, A is the temperature coefficient of resistance of the heating part.

[0060] On the other hand, the increase in resistance value accompanying the temperature rise in the PTC thermistors 91 to 94 is r·B·T2 < r·B·T1(=r·B·T3 = r·B·T4), and the increase in resistance value of the PTC thermistor 92 becomes larger than that of the other PTC thermistors 91, 93, 94. Here, B is the temperature coefficient of resistance of the PTC thermistor.

[0061] And because the temperature coefficient of resistance B of the PTC thermistors 91 to 94 is larger than the temperature coefficient of resistance A of the heating parts 61 to 64, when the resistance value R2 of the heating part 62 is larger than the resistance values R1, R3, R4 of the other heating parts 61, 63, 64 (R2 > R1 = R3 = R4), due to the temperature rise, the increase in the resistance value R1’(R3’, R4’) of the circuit composed of the heating part 61(63, 64) and the PTC thermistor 91(93, 94) becomes larger than the increase in the resistance value R2’ of the circuit composed of the heating part 62 and the PTC thermistor 92. Therefore, the difference between the resistance value R2’ and the resistance values R1’(R3’, R4’) becomes smaller.

[0062] As a result, current easily flows through the circuit on the heating part 62 side, while it becomes difficult for current to flow through the circuit on the heating part 61(63, 64) side. Therefore, the calorific value of the heating part 62 increases, the calorific value of the heating part 61(63, 64) decreases, and the difference between the temperature of the heating part 62 and the temperature of the heating part 61(63, 64) becomes smaller and almost the same. And because such temperature adjustment is performed among the heating parts 61 to 64, the temperatures of the heating parts 61 to 64 can be made uniform.

[0063] Furthermore, in this embodiment, even if the heat input to the semiconductor wafer W deteriorates the thermal uniformity on the holding surface 11, the above-mentioned temperature adjustment is automatically performed in each heat generating portion 61 to 64, so that the temperature distribution on the holding surface 11 can be maintained uniform.

[0064] As described above, according to the electrostatic chuck of the second embodiment, by connecting the NTC thermistors 81-84 in parallel to the heat generating parts 61-64, respectively, which are connected in series, it is possible to automatically adjust the temperature in each of the heat generating parts 61-64 uniformly. Therefore, it is possible to improve the temperature uniformity on the holding surface 11.

[0065] It should be noted that the above-mentioned embodiments are merely examples and do not limit the present disclosure in any way, and it goes without saying that various improvements and modifications are possible without departing from the scope of the present disclosure. For example, in the above-mentioned first embodiment, the case where NTC thermistors 81-84 are used as resistors connected in parallel to the heat generating parts 61-64 is illustrated, but the resistors connected in parallel to the heat generating parts 61-64 are not limited to NTC thermistors, and may be any element (e.g., silicon-based semiconductor, perovskite semiconductor, etc.) that has a higher resistance temperature coefficient than the heat generating parts and whose resistance value decreases as the temperature increases.

[0066] In addition, in the above second embodiment, an example is given of the case where PTC thermistors 91-94 are used as resistors connected in series to the heat generating portions 61-64, but the resistors connected in series to the heat generating portions 61-64 are not limited to PTC thermistors, and may be any element (e.g., a platinum resistance thermometer) whose resistance temperature coefficient is smaller than that of the heat generating portions and whose resistance value increases as the temperature rises.

[0067] Furthermore, in the above embodiment, the case where one external power source is used to supply power to the heater electrode is exemplified, but two or more external power sources may be provided, and even more heat generating parts (more than 10 to about 50) may be provided. This allows the temperature distribution on the holding surface 11 to be made even more uniform. [Explanation of symbols]

[0068] 1. Electrostatic chuck 10 Plate-shaped member 11 Holding surface 12 Bottom side 20 Base material 30 Bonding layer 60 Heater electrode 61~64 Heating part 81~84 NTC thermistor 91~94 PTC thermistor W Semiconductor wafer

Claims

1. A holding device for holding an object on the first surface, the holding device comprising: a first surface; a second surface provided on an opposite side to the first surface in a thickness direction; a heater electrode disposed between the first surface and the second surface; and a resistor connected to the heater electrode, the holding device holding an object on the first surface, The heater electrode includes a plurality of heat generating portions connected in series, The resistors are elements whose resistance temperature coefficient is larger than that of the heat generating parts and whose resistance value decreases as the temperature increases, and are connected in parallel to the heat generating parts. A holding device characterized in that

2. A holding device for holding an object on the first surface, the holding device comprising: a first surface; a second surface provided on an opposite side to the first surface in a thickness direction; a heater electrode disposed between the first surface and the second surface; and a resistor connected to the heater electrode, the holding device holding an object on the first surface, The heater electrode includes a plurality of heat generating portions connected in parallel, The resistors are elements whose resistance temperature coefficient is smaller than that of the heat generating parts and whose resistance value increases as the temperature rises, and are connected in series to the heat generating parts. A holding device characterized in that

3. 2. The holding device according to claim 1, The resistor is an NTC thermistor. A holding device characterized in that

4. 3. The holding device according to claim 2, The resistor is a PTC thermistor. A holding device characterized in that

5. In any one of the holding devices according to claims 1 to 4, The number of the heat generating parts supplied with power from one external power source is 10 or less. A holding device characterized in that

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