Wafer heating device and wafer heating method

Abstract

This wafer heating device comprises: a mounting plate having an upper surface on which a wafer is mounted; a heater disposed inside the mounting plate; and a temperature measuring body disposed inside the mounting plate. The mounting plate has a plurality of heating zones in a top view. The temperature measuring body includes a differential thermocouple for measuring a temperature difference ΔT between a first zone and a second zone different from each other in the plurality of heating zones.

Description

Wafer heating apparatus and wafer heating method

[0001] The present disclosure relates to a wafer heating apparatus and a wafer heating method.

[0002] Patent Documents 1 to 3 disclose wafer heating devices that heat wafers, for example, when forming a coating on the wafer. The wafer heating device includes a mounting plate having an upper surface on which the wafer is placed, and a heater that heats the wafer. The mounting plate has multiple heating zones when viewed from above. The temperatures of the multiple heating zones are controlled independently.

[0003] In a wafer heating device, it is necessary to control the temperature of each of the multiple heating zones in order to heat the entire wafer uniformly. For this reason, temperature sensors are installed inside the mounting plate to measure the temperature of each heating zone. The temperature of each heating zone is adjusted based on the temperature information from each temperature sensor.

[0004] International Publication No. WO 2020 / 129641 International Publication No. WO 2020 / 129754 International Publication No. WO 2020 / 129798

[0005] The wafer heating apparatus of the present disclosure includes a wafer mounting plate having an upper surface on which a wafer is mounted, a heater disposed within the mounting plate, and a temperature sensor disposed within the mounting plate. The mounting plate has a plurality of heating zones in a top view. The temperature sensor includes a differential thermocouple that measures a temperature difference ΔT between a first zone and a second zone that are different from each other in the plurality of heating zones.

[0006] FIG. 1 is a schematic diagram of a wafer heating apparatus according to a first embodiment. FIG. 2 is a schematic diagram showing the arrangement of temperature measuring elements provided in the wafer heating apparatus shown in FIG. 1. FIG. 3 is a schematic side view of the wafer heating apparatus shown in FIG. 1. FIG. 4 is a flowchart showing an example of temperature control in the wafer heating apparatus according to the first embodiment. FIG. 5 is a flowchart showing an example of temperature control in the wafer heating apparatus according to the second embodiment. FIG. 6 is a schematic diagram showing the arrangement of temperature measuring elements provided in the wafer heating apparatus according to the third embodiment. FIG. 7 is a schematic diagram explaining the basic configuration of a differential thermocouple. FIG. 8 is a schematic diagram explaining a configuration in which a differential thermocouple includes three or more thermocouples.

[0007] [Problem to be Solved by the Present Disclosure] In conventional wafer heating devices, if there is a measurement error between the multiple temperature sensors on the mounting plate, it is difficult to accurately match the temperatures of the multiple heating zones. In addition, conventional wafer heating devices have a problem in that the total number of wires extending from the multiple temperature sensors is large, making the arrangement of the multiple wires and their connection to the detectors complicated.

[0008] An object of the present disclosure is to provide a wafer heating apparatus that has a simple configuration and is capable of matching the temperatures of multiple heating zones with high accuracy.

[0009] [Description of Embodiments of the Present Disclosure] Hereinafter, embodiments of the present disclosure will be listed and described.

[0010] A wafer heating apparatus according to an embodiment includes a mounting plate having an upper surface on which a wafer is placed, a heater disposed within the mounting plate, and a temperature sensor disposed within the mounting plate. The mounting plate has a plurality of heating zones in a top view. The temperature sensor includes a differential thermocouple that measures a temperature difference ΔT between a first zone and a second zone that are different from each other in the plurality of heating zones.

[0011] In the present disclosure, a "differential thermocouple" refers to a thermocouple configured by connecting a first thermocouple and a second thermocouple disposed at two different locations in series. A method for connecting a differential thermocouple will be described later. A differential thermocouple generates an electromotive force corresponding to the temperature difference between the location where the first thermocouple is disposed and the location where the second thermocouple is disposed. That is, a wafer heating apparatus according to an embodiment includes a first thermocouple and a second thermocouple disposed in a first zone and a second zone, respectively, and is equipped with a differential thermocouple in which the first thermocouple and the second thermocouple are connected to generate an electromotive force corresponding to the temperature difference ΔT between the first zone and the second zone.

[0012] In a wafer heating apparatus according to an embodiment, a differential thermocouple included in a temperature detector includes a first measurement unit and a second measurement unit. A differential thermocouple in which the first measurement unit is disposed in a first zone and the second measurement unit is disposed in a second zone outputs a potential difference ΔV corresponding to the temperature difference ΔT between the first zone and the second zone. The temperature difference ΔT is a function of the potential difference ΔV, and ΔT = f(ΔV) holds. If the temperature difference ΔT is zero, the potential difference ΔV is also zero. If g is an inverse function of f, ΔV = g(ΔT) holds. In other words, the temperature difference ΔT can be calculated from the potential difference ΔV, which is the output voltage of the differential thermocouple.

[0013] A typical thermocouple measures the temperature of the temperature measuring point by measuring the thermoelectromotive force generated by the temperature difference between the temperature measuring point and the terminals of a voltmeter. Creating a measurement device with the voltmeter terminals as an ideal cold junction of zero degrees Celsius is very costly. Furthermore, maintaining such a measurement device is cumbersome. Therefore, a typical thermocouple accurately measures the temperature of the voltmeter terminals and compensates for the difference between the terminal temperature and zero degrees Celsius using a cold junction compensation circuit. In this case, any measurement error in the terminal temperature directly results in a measurement error in the thermocouple. On the other hand, a differential thermocouple, which measures the temperature difference ΔT, can measure the temperature difference ΔT between two heating zones without requiring a cold junction. Therefore, a differential thermocouple does not have the problem of measurement errors between the temperature sensors that occur when measuring the temperatures of two heating zones using two independent temperature sensors. Therefore, in the wafer heating apparatus described above, the temperatures of the first and second zones can be matched with high precision by adjusting the temperatures of the first and second zones based on the temperature difference ΔT obtained by the differential thermocouple.

[0014] In the above-described wafer heating apparatus, the number of wires extending from the temperature sensors can be reduced. For example, if independent temperature sensors are disposed in the first and second zones, the number of temperature sensors is two, and the total number of wires extending from the two temperature sensors is four. On the other hand, the total number of wires extending from a differential thermocouple disposed across the first and second zones is two. As shown in the embodiment described below, if multiple differential thermocouples are disposed on the mounting plate, wires can be shared between different differential thermocouples. In this case, the total number of wires extending from the temperature sensors is further reduced, facilitating the arrangement of the wires and their connection to the detectors.

[0015] <2> The wafer heating apparatus described in <1> above may further include a temperature sensor disposed in the first zone, and the temperature sensor may be a resistance temperature detector or a thermocouple.

[0016] If a temperature sensor is placed in the first zone, the temperature T1 of the first zone can be measured based on the output voltage from the temperature sensor. The temperature T2 of the second zone can be calculated based on this temperature T1 and the temperature difference ΔT obtained from the differential thermocouple. By calculating the temperature T2, it is easy to match the temperature T1 of the first zone with the temperature T2 of the second zone with high accuracy.

[0017] The resistance thermometer has excellent temperature resolution, allowing it to accurately measure the temperature T1 of the first zone. The thermocouple has a simple structure, making it easy to place inside the mounting plate. In addition, the thermocouple has excellent response, allowing it to quickly measure the temperature of the heating zone where the temperature sensor is located.

[0018] <3> In the wafer heating apparatus described in <1> or <2> above, the mounting plate has a circular plate shape, and the multiple heating zones consist of a circular central zone and at least one peripheral zone arranged on the periphery of the central zone, and the central zone may be the first zone and the at least one peripheral zone may be the second zone.

[0019] In the configuration <3>, the temperature of the central zone and the temperature of the peripheral zone can be easily matched with high precision, and therefore the configuration <3> can uniformly heat the entire surface of the wafer placed on the mounting plate.

[0020] <4> In the wafer heating apparatus described in <3> above, the at least one outer peripheral zone may be composed of a plurality of outer peripheral zones surrounding the central zone, and each of the plurality of outer peripheral zones may be the second zone.

[0021] In the outer peripheral portion of the support plate, excluding the central zone, the temperature is likely to vary due to the influence of the external environment of the support plate. In the configuration of <4> above, the outer peripheral portion of the support plate is divided into multiple outer peripheral zones. Therefore, by adjusting the temperature of each of the multiple outer peripheral zones, it is easy to make the temperature of the entire outer peripheral portion of the support plate uniform.

[0022] In the configuration <4> above, each of the multiple peripheral zones is a second zone. That is, the configuration <4> above is provided with multiple differential thermocouples that measure the temperature difference ΔT between the central zone and each peripheral zone. Therefore, in the configuration <4> above, by adjusting the temperature of each heating zone based on the temperature difference ΔT between the central zone and each peripheral zone, it is easy to uniformize the temperature of the entire mounting plate. Such a wafer heating device can uniformly heat the entire wafer.

[0023] <5> In the wafer heating apparatus described in any one of <1> to <4> above, the mounting plate may include, in order from above, a top plate having the upper surface, a sensor plate having the differential thermocouple, and a heater plate having the heater. The top plate, the sensor plate, and the heater plate are joined together, and the differential thermocouple is formed by metal wires printed on the sensor plate.

[0024] The mounting plate constructed by joining the top plate, sensor plate, and heater plate is highly productive. In addition, since the differential thermocouple is constructed by printing, it is easier to position the first and second measurement parts of the differential thermocouple at the desired positions than in a configuration in which a differential thermocouple is provided separately from the mounting plate.

[0025] <6> The wafer heating apparatus described in any one of <1> to <5> above may further include a control unit that controls the heater, and the heater may include a plurality of heat generating elements arranged in each of the plurality of heating zones, and each of the plurality of heat generating elements may be controlled by the control unit.

[0026] In the configuration of <6> above, the heat generating units corresponding to the plurality of heating zones are controlled independently, so that the temperature of each heating zone can be adjusted with high precision.

[0027] <7> The wafer heating apparatus described in <6> above may further include a temperature sensor disposed in the first zone, and the control unit may determine a temperature T2 of the second zone based on a temperature T1 of the first zone obtained by the temperature sensor and the temperature difference ΔT obtained by the differential thermocouple, and control the heater so that the temperature T2 becomes a target temperature.

[0028] In the configuration <7> above, the temperature T1 of the first zone and the temperature T2 of the second zone are calculated, and then the temperature T2 is controlled to be the same as the target temperature, i.e., the temperature T1. Therefore, in this configuration, it is easy to accurately adjust both the temperatures of the first zone and the second zone to the target temperatures.

[0029] <8> In the wafer heating apparatus described in <6> above, the control unit may calculate the temperature difference ΔT based on the output voltage of the differential thermocouple, and control the heater so that the temperature difference ΔT approaches zero.

[0030] In the configuration of <8> above, the heater is controlled so that the temperature difference ΔT between the first and second zones approaches zero, which makes it easy for the temperatures of the first and second zones to quickly match. Furthermore, this configuration can be controlled by an analog circuit, which makes it easy to simplify the configuration of the control unit. Of course, this configuration is not limited to being controlled by an analog circuit, and may also be controlled by a digital circuit.

[0031] <9> A first wafer heating method according to the present embodiment is a wafer heating method for heating a wafer placed on an upper surface of a wafer mounting plate using a wafer heating device including a mounting plate, a heater disposed inside the mounting plate, and a temperature detector disposed inside the mounting plate. The mounting plate has multiple heating zones in a top view, and the temperature detector includes a differential thermocouple that measures a temperature difference ΔT between a first zone and a second zone that are independent of each other in the multiple heating zones. The first wafer heating method controls the heater so that a temperature T1 of the first zone becomes a target temperature, calculates a temperature T2 of the second zone based on the temperature T1 and the temperature difference ΔT, and controls the heater so that the temperature T2 becomes the target temperature.

[0032] In the first heating method, the temperature T1 of the first zone is controlled, and the temperature T2 of the second zone is calculated based on the temperature T1 and the temperature difference ΔT, and the temperature T2 is controlled to be the same as the temperature T1. Therefore, the first heating method makes it easy to accurately adjust both the temperatures of the first zone and the second zone to the target temperatures.

[0033] <10> A second wafer heating method according to the present embodiment is a wafer heating method for heating a wafer placed on an upper surface of a mounting plate using a wafer heating device including a mounting plate, a heater disposed inside the mounting plate, and a temperature detector disposed inside the mounting plate. The mounting plate has multiple heating zones in a top view, and the temperature detector includes a differential thermocouple that measures a temperature difference ΔT between a first zone and a second zone that are independent of each other in the multiple heating zones. In the second wafer heating method, the heater is controlled so that the temperature difference ΔT approaches zero.

[0034] In the second heating method, the heater is controlled so that the temperature difference ΔT between the first zone and the second zone approaches zero. Therefore, the second heating method makes it easy to quickly make the temperature of the first zone and the temperature of the second zone match.

[0035] [Details of the Embodiments of the Present Disclosure] Specific examples of wafer heating apparatuses according to embodiments of the present disclosure will now be described with reference to the drawings. The same reference numerals in the figures indicate the same or equivalent parts. The sizes of the components shown in the drawings are expressed for the purpose of clarity of explanation and do not necessarily represent the actual dimensions. The present invention is not limited to these examples, but is defined by the claims, and all modifications within the meaning and scope equivalent to the claims are intended to be included.

[0036] <Embodiment 1> <Overall Configuration> The wafer heating apparatus 1 illustrated in Figure 1 is used in a film formation process for forming a coating on the surface of a wafer. The wafer heating apparatus 1 of this example includes a mounting plate 2, a heater 3, and a control unit 4. The wafer heating apparatus 1 of this example further includes a temperature detector 5 and a temperature sensor 7. Each component of the wafer heating apparatus 1 will be described in detail below.

[0037] 1, the mounting plate 2 is shown exploded into a top plate 21, a sensor plate 22, and a heater plate 23. The mounting plate 2 has an upper surface 2U that faces upward in the wafer heating apparatus 1, and a lower surface 2L that faces downward. The lower surface 2L is the surface opposite the upper surface 2U. A wafer is placed on the upper surface 2U of the mounting plate 2 when a coating is formed on the surface of the wafer using the wafer heating apparatus 1 of this example. The wafer is, for example, a silicon wafer.

[0038] In this example, the mounting plate 2 is a circular plate. The diameter of the circular plate needs only to be larger than the wafer to be mounted on the upper surface 2U, for example, 200 mm to 500 mm. The planar shape of the mounting plate 2 is not limited to a circle, but may be any shape similar to the planar shape of the wafer. For example, the planar shape of the mounting plate 2 may be a polygon such as a rectangle.

[0039] The material of the mounting plate 2 is, for example, ceramics. Examples of ceramics include aluminum nitride, aluminum oxide, and silicon carbide (SiC). The material of the mounting plate 2 may also be a composite of the above ceramics and silicon (Si). For example, the composite is Si-SiC, which is a porous SiC body impregnated with silicon.

[0040] The mounting plate 2 of this example includes, in order from the top, a top plate 21, a sensor plate 22, and a heater plate 23. The top plate 21, the sensor plate 22, and the heater plate 23 are prepared separately. The mounting plate 2 of this example is formed by joining these three plates. The joining of the three plates may be performed by adhesive bonding or by fastening with fastening members. Unlike this example, the mounting plate 2 may be formed from a single member.

[0041] The top plate 21 has a surface that forms the upper surface 2U of the mounting plate 2. The top plate 21 may be provided with a vacuum port for suctioning the wafer, or may be provided with pin holes in which lift pins that lift the wafer are disposed.

[0042] The sensor plate 22 includes a temperature detector 5 and a temperature sensor 7, which will be described later. The temperature detector 5 and the temperature sensor 7 measure the temperature at various points on the mounting plate 2. The detailed configuration and arrangement of the temperature detector 5 and the temperature sensor 7 will be described later.

[0043] The heater plate 23 includes multiple heat generating elements 3A, 3B, 3C, 3D, and 3E, which are part of the heater 3 described below. FIG. 1 shows only the area where the heat generating elements 3A, 3B, 3C, 3D, and 3E are arranged; the heat generating elements 3A, 3B, 3C, 3D, and 3E themselves are not shown. The multiple heat generating elements 3A, 3B, 3C, 3D, and 3E are independent of each other. Therefore, the temperatures of the heat generating elements 3A, 3B, 3C, 3D, and 3E can be changed independently. By making the sensor plate 22 and the heater plate 23 independent components, the temperature detector 5 and temperature sensor 7 do not interfere with the heat generating elements 3A, 3B, 3C, 3D, and 3E. This allows for a high degree of freedom in the arrangement of the temperature detector 5, temperature sensor 7, and heat generating elements 3A, 3B, 3C, 3D, and 3E.

[0044] The mounting plate 2 has, in a top view, multiple heating zones 2A, 2B, 2C, 2D, and 2E heated by multiple heat generating elements 3A, 3B, 3C, 3D, and 3E, respectively. The heating zones 2A, 2B, 2C, 2D, and 2E are virtual regions. In FIG. 1 , the heating zones 2A, 2B, 2C, 2D, and 2E are shown only on the sensor plate 22, demarcated by two-dot chain lines. In this example, the circular heating zone 2A that includes the center of the mounting plate 2 is called the central zone, and the arc-shaped heating zones 2B, 2C, 2D, and 2E that surround the circular heating zone 2A are called peripheral zones.

[0045] A coolant flow path (not shown) may be arranged inside the mounting plate 2. A coolant is supplied to the coolant flow path as needed. The coolant flow path is configured to quickly cool the mounting plate 2 heated by the heater 3. By quickly cooling the mounting plate 2, the time required to start processing a new wafer can be shortened.

[0046] In this example, the mounting plate 2 is supported by a cylindrical support 9. As shown in FIG. 3, the support 9 supports the lower surface 2L of the mounting plate 2. FIG. 3 is a side view of the mounting plate 2 and its vicinity in the wafer heating apparatus 1, with the support 9 shown cut along a plane along its axis. The shape of the support 9 is not particularly limited. In this example, the support 9 is cylindrical. The support 9 is disposed roughly concentrically with the mounting plate 2. In this example, the mounting plate 2 is attached to the support 9 so that the central axis of the cylindrical support 9 is coaxial with the central axis of the disk-shaped mounting plate 2. Inside the support 9, conductors 51W, 52W, 53W, 54W, and 55W extending from the temperature detector 5 and a sensor wire 7W extending from the temperature sensor 7 are disposed. In FIG. 1, only conductor 51W is shown.

[0047] The material of the support 9 is, for example, ceramics. The material of the support 9 may be the same as or different from the material of the mounting plate 2.

[0048] <Heater> As shown in FIG. 1, the heater 3 includes a power supply 30 and a plurality of heat generating elements 3A, 3B, 3C, 3D, and 3E that generate heat using power supplied from the power supply 30. As described above, the plurality of heat generating elements 3A, 3B, 3C, 3D, and 3E are disposed inside the mounting plate 2. Each of the heat generating elements 3A, 3B, 3C, 3D, and 3E is connected to the power supply 30 by a power line 3W that is independent of the others. Only one power line 3W is shown in FIG. 1. The power line 3W is disposed inside the support 9 shown in FIG. 3. The amount of power supplied to each of the heat generating elements 3A, 3B, 3C, 3D, and 3E is adjusted by the control unit 4, which will be described later. The heat generated by the heat generating elements 3A, 3B, 3C, 3D, and 3E is transferred from inside the mounting plate 2 to the upper surface 2U, heating the wafer.

[0049] In this example, the heating elements 3A, 3B, 3C, 3D, and 3E are resistance heating elements. The resistance heating elements in this example are circuit patterns formed by printing on the upper surface of the heater plate 23. In this case, holes are formed in the heater plate 23 that penetrate from the circuit pattern to the lower surface of the heater plate 23. Power lines 3W pass through these holes to connect to each of the heating elements 3A, 3B, 3C, 3D, and 3E. The material of the resistance heating elements is, for example, one selected from the group consisting of stainless steel, nickel, nickel alloy, silver, silver alloy, tungsten, tungsten alloy, molybdenum, molybdenum alloy, chromium, and chromium alloy. The nickel alloy is, for example, nichrome.

[0050] Unlike this example, heat generating portions 3A, 3B, 3C, 3D, and 3E may be configured independent of heater plate 23. For example, a heater sheet including heat generating portions 3A, 3B, 3C, 3D, and 3E may be disposed on the upper surface of heater plate 23. The heater sheet has a configuration in which heat generating portions 3A, 3B, 3C, 3D, and 3E formed by circuit patterns are sandwiched between two polyimide sheets.

[0051] <Temperature Detector> The temperature detector 5 includes a differential thermocouple 6 that measures the temperature difference ΔT between two different zones. Here, the basic configuration of the differential thermocouple 6 will be described with reference to FIG. 7 . The differential thermocouple 6 is configured by connecting a first metal wire 61, a second metal wire 62, and a third metal wire 63 in series. Conductor wires 61W and 63W are connected to the first metal wire 61 and the third metal wire 63, respectively. The first metal wire 61 and the second metal wire 62 are configured from different metals, and the second metal wire 62 and the third metal wire 63 are configured from different metals. The first metal wire 61 and the third metal wire 63 are configured from the same metal, and the conductive wires 61W and 63W are configured from the same metal. The joint between the first metal wire 61 and the second metal wire 62 is a first measuring portion 65, and the joint between the second metal wire 62 and the third metal wire 63 is a second measuring portion 66. In the differential thermocouple 6 having such a configuration, a potential difference ΔV is generated between the conductors 61W and 63W in accordance with the temperature difference ΔT between the first zone Z1 in which the first measuring unit 65 is disposed and the second zone Z2 in which the second measuring unit 66 is disposed. The potential difference ΔV is a function of the temperature difference ΔT, and ΔT = f(ΔV) holds. If g is an inverse function of f, then ΔV = g(ΔT) holds. In other words, the temperature difference ΔT can be calculated from the potential difference ΔV, which is the output voltage of the differential thermocouple.

[0052] The combination of two metal wires to be connected is, for example, a combination of copper and constantan, a combination of alumel and chromel, a combination of tungsten and tungsten-rhenium, or a combination of platinum and rhodium.

[0053] The metals constituting the first metal wire 61 and the conducting wire 61W may be the same metal or different metals. The third metal wire 63 and the conducting wire 63W may be the same metal or different metals. When the first metal wire 61 and the conducting wire 61W are made of different metals, positioning the joint between the first metal wire 61 and the conducting wire 61W in the first zone Z1 improves measurement accuracy. Similarly, when the third metal wire 63 and the conducting wire 63W are made of different metals, positioning the joint between the third metal wire 63 and the conducting wire 63W in the second zone Z2 improves measurement accuracy.

[0054] Furthermore, when the temperature difference between the first measuring unit 65 and the second measuring unit 66 is small and the potential difference ΔV, which is the output voltage, is small, the differential thermocouple 6 may have a configuration in which three or more thermocouples are connected in series, as shown in FIG. 8 . The differential thermocouple 6 in FIG. 8 has a first metal wire 61, a second metal wire 62, a first metal wire 61, a second metal wire 62, and a third metal wire 63 connected in series, starting from the conductor 61W. In this case, two first measuring units 65, 65 and two second measuring units 66, 66 are formed. The two first measuring units 65, 65 are arranged in a first zone Z1, and the two second measuring units 66, 66 are arranged in a second zone Z2. The potential difference ΔV increases depending on the number of thermocouples connected in series.

[0055] Based on the basic configuration of the differential thermocouple 6, the configuration of the temperature sensor 5 in this example will be described with reference to Fig. 2. Here, the position of each part of the temperature sensor 5 will be described by likening the top surface of the sensor plate 22 to the face of a clock.

[0056] First, the arrangement of heating zones 2A, 2B, 2C, 2D, and 2E on the sensor plate 22 will be described. Heating zone 2A, located at the center of the sensor plate 22, is a circular central zone. The four heating zones 2B, 2C, 2D, and 2E, located around the periphery of heating zone 2A, are arc-shaped peripheral zones with a certain width. Heating zone 2B is located from 12 o'clock to 3 o'clock, heating zone 2C is located from 3 o'clock to 6 o'clock, heating zone 2D is located from 6 o'clock to 9 o'clock, and heating zone 2E is located from 9 o'clock to 12 o'clock.

[0057] The temperature detector 5 includes a plurality of metal wires 5X, 5Y, 5A, 5B, 5C, 5D, and 5E arranged on the upper surface of the sensor plate 22. The metal wire 5X extends from the heating zone 2B through the heating zone 2A to the heating zone 2D. The metal wire 5Y extends from the heating zone 2C through the heating zone 2A to the heating zone 2E. The metal wires 5X and 5Y are electrically connected at an intersection 50. The intersection 50 is arranged in the heating zone 2A. The metal wires 5X and 5Y are made of the same metal.

[0058] Metal wire 5A extends from intersection 50 to a position near intersection 50. Metal wire 5B extends from a first end of metal wire 5X located in heating zone 2B to a position near intersection 50. Metal wire 5C extends from a first end of metal wire 5Y located in heating zone 2C to a position near intersection 50. Metal wire 5D extends from a second end of metal wire 5X located in heating zone 2D to a position near intersection 50. Metal wire 5E extends from a second end of metal wire 5Y located in heating zone 2E to a position near intersection 50. The ends of metal wires 5A, 5B, 5C, 5D, and 5E indicated by black circles may be located anywhere within heating zone 2A. Metal wires 5A, 5B, 5C, 5D, and 5E are made of the same metal. The metal wires 5A, 5B, 5C, 5D, and 5E and the metal wires 5X and 5Y are made of different metals.

[0059] The ends of metal wires 5A, 5B, 5C, 5D, and 5E, indicated by black circles, are connected to conductors 51W, 52W, 53W, 54W, and 55W, indicated by dashed lines. The conductors 51W, 52W, 53W, 54W, and 55W are disposed inside support 9 as shown in FIG. 3. The ends of conductors 51W, 52W, 53W, 54W, and 55W, indicated by hatched circles, are connected to detector 8 shown in FIG. 1. Detector 8 in this example is a voltmeter capable of measuring the voltage between any two conductors. Note that the temperature detector 5 is simplified in FIG. 3.

[0060] The temperature detector 5 having the above configuration has five measurement sections 51, 52, 53, 54, and 55, indicated by white circles. Measurement section 51 is the joint between metal wire 5X and metal wire 5A, and is also an intersection 50 between metal wire 5Y and metal wire 5A. Measurement section 52 is the joint between metal wire 5X and metal wire 5B. Measurement section 53 is the joint between metal wire 5Y and metal wire 5C. Measurement section 54 is the joint between metal wire 5X and metal wire 5D. Measurement section 55 is the joint between metal wire 5Y and metal wire 5E. With this type of temperature detector 5, the temperature difference ΔT between two different measurement sections can be measured. Specifically, the temperature detector 5 of this example can measure four types of temperature differences ΔT: between the measuring units 51 and 52, between the measuring units 51 and 53, between the measuring units 51 and 54, and between the measuring units 51 and 55. In other words, the temperature detector 5 of this example includes four differential thermocouples 6.

[0061] Here, the temperature measuring element 5 having the above configuration can also measure the temperature differences ΔT between the measuring units 52 and 53, between the measuring units 52 and 54, between the measuring units 52 and 55, between the measuring units 53 and 54, between the measuring units 53 and 55, and between the measuring units 54 and 55. However, in this example, these temperature differences ΔT are not used to control the heater 3.

[0062] The temperature difference ΔT between two different measurement units is determined by the potential difference ΔV between the two different measurement units. For example, to determine the temperature difference ΔT between measurement unit 51 and measurement unit 52, i.e., the temperature difference ΔT between heating zone 2A and heating zone 2B, it is sufficient to measure the potential difference ΔV between conductor 51W and conductor 52W. In this case, heating zone 2A and heating zone 2B correspond to first zone Z1 and second zone Z2 in Figure 7, respectively.

[0063] The metal wires 5X, 5Y, 5A, 5B, 5C, 5D, and 5E that make up the temperature detector 5 are formed, for example, by embedding them in the mounting plate 2 or by printing them on the sensor plate 22. In the former case, grooves are formed in the surface of the sensor plate 22, and the metal wires 5X, 5Y, 5A, 5B, 5C, 5D, and 5E are disposed in the grooves. The sensor plate 22 is then sandwiched between the top plate 21 and the heater plate 23, so that the metal wires 5X, 5Y, 5A, 5B, 5C, 5D, and 5E are embedded in the mounting plate 2. The grooves may be formed on either the upper or lower surface of the sensor plate 22. Examples of printing methods include screen printing, flexographic printing, gravure printing, gravure offset printing, dispenser printing, and inkjet printing. In these printing methods, a conductive paste containing metal particles dispersed in a binder is applied to the upper or lower surface of the sensor plate 22. By hardening or dissolving the binder, metal wires 5X, 5Y, 5A, 5B, 5C, 5D, and 5E are formed. By forming the temperature sensor 5 by printing, it is easy to arrange each of the measuring parts 51, 52, 53, 54, and 55 at the desired positions.

[0064] When the temperature detector 5 is formed by printing, holes are formed from the ends of the metal wires 5A, 5B, 5C, 5D, and 5E, indicated by black circles, to the underside 2L of the mounting plate 2. The conductor wires 51W, 52W, 53W, 54W, and 55W pass through these holes and are connected to the ends of the metal wires 5A, 5B, 5C, 5D, and 5E. Because the ends of the metal wires 5A, 5B, 5C, 5D, and 5E are gathered at the center of the mounting plate 2, the conductor wires 51W, 52W, 53W, 54W, and 55W are simply pulled out of the holes and placed inside the support 9 (FIG. 3).

[0065] <Temperature Sensor> The wafer heating apparatus 1 of this embodiment further includes a temperature sensor 7 that measures the temperature of one of the heating zones 2A, 2B, 2C, 2D, and 2E. In this embodiment, the temperature sensor 7 is disposed in the heating zone 2A, which is the central zone. Unlike this embodiment, the temperature sensor 7 may be disposed in the peripheral zone. The temperature sensor 7 is, for example, a resistance temperature detector or a thermocouple. A resistance temperature detector has excellent temperature resolution. A thermocouple has a simple structure and is therefore easy to place inside the mounting plate 2. Furthermore, a thermocouple has excellent responsiveness, allowing the temperature of the heating zone 2A to be measured quickly.

[0066] The temperature sensor 7 measures the temperature T1 of the heating zone 2A in which the temperature sensor 7 is located. The temperature T1 is used as a reference for adjusting the temperatures of the remaining heating zones 2B, 2C, 2D, and 2E in which the temperature sensor 7 is not located.

[0067] 3, a sensor wire 7W connected to the temperature sensor 7 passes through a hole in the mounting plate 2 (not shown) and is drawn into the support body 9. The sensor wire 7W has a configuration in which two conducting wires are combined into one by an insulating coating.

[0068] 1 controls the heater 3 based on the measurement results of the differential thermocouple 6 and the temperature sensor 7. Specifically, the control unit 4 controls the power supply 30 to control the power supplied to the heat generating units 3A, 3B, 3C, 3D, and 3E. In addition to controlling the heater 3, the control unit 4 may also control components other than the heater 3 in the wafer heating apparatus 1.

[0069] Each process performed by the control unit 4 is realized by a processing circuit including at least one processor. The processing circuit may be configured as an integrated circuit that combines at least one processor, at least one memory, various analog circuits, and various digital circuits. The at least one memory stores a program (instruction) that causes the at least one processor to execute each of the processes. The at least one processor may execute each of the processes according to the program read from the at least one memory, or according to a logic circuit designed in advance to execute each of the processes. The processor may be, for example, a CPU or a GPU, or any other processor suitable for computer control. Note that the processes may be executed by multiple physically separate processors working together.

[0070] <Wafer Heating Method> An example of a wafer heating method for heating a wafer placed on the upper surface of a mounting plate 2 using the wafer heating apparatus 1 according to embodiment 1 will be described. In the following description, an example will be described in which the control unit 4 of the wafer heating apparatus 1 controls the heating zone 2A and the heating zone 2B, mainly with reference to Figures 1 and 2. In this case, the heating zone 2A is the first zone Z1, and the heating zone 2B is the second zone Z2.

[0071] In this example, the heater 3 is controlled so that the temperature T1 of the first zone Z1 becomes the target temperature, the temperature T2 of the second zone Z2 is calculated based on the temperature T1 and the temperature difference ΔT, and the heater 3 is controlled so that the temperature T2 becomes the target temperature.

[0072] First, the control unit 4 supplies power to the heat generating unit 3A to heat the first zone Z1, and supplies power to the heat generating unit 3B to heat the second zone Z2. Furthermore, the control unit 4 adjusts the temperature so that the difference between the temperature T1 and the temperature T2 becomes small. The temperature adjustment is performed, for example, according to the flowchart of FIG.

[0073] The control unit 4 determines the temperature T1 of the first zone Z1 based on real-time information from the temperature sensor 7 measured by the detection unit 8 (step S1 in FIG. 4 ). The control unit 4 maintains the temperature T1 at a target temperature by adjusting the amount of power supplied to the heat generating unit 3A. The target temperature is, for example, in the range of 500°C to 600°C. The control unit 4 further determines the temperature difference ΔT between the temperature T1 of the first zone Z1 and the temperature T2 of the second zone Z2 based on real-time information from the differential thermocouple 6 measured by the detection unit 8 (step S2). Here, the information from the temperature sensor 7 and the differential thermocouple 6 measured by the detection unit 8 is a voltage value. The voltage value information is converted into temperature information by a computer constituting the control unit 4.

[0074] The control unit 4 calculates the temperature T2 of the second zone Z2 based on the temperature T1 obtained by the temperature sensor 7 and the temperature difference ΔT obtained from the differential thermocouple 6 (step S3). Specifically, the temperature T1 of the temperature sensor 7 disposed near the measurement unit 51 is regarded as the temperature T1 at the measurement unit 51, and the temperature T2 is calculated.

[0075] The control unit 4 determines whether the difference between the temperature T2 and the target temperature exceeds a predetermined value (step S4). The predetermined value may be zero. If the predetermined value is set to a small value, the temperature T1 of the first zone Z1 and the temperature T2 of the second zone Z2 can be made to match with high accuracy. The target temperature of the temperature T2 is the same as the target temperature of the temperature T1. If the difference between the temperature T2 and the target temperature is equal to or less than the predetermined value, the control unit 4 maintains the amount of power supplied to the heater 3 without changing it, and returns to the processing of step S1.

[0076] If the difference between temperature T2 and the target temperature exceeds a predetermined value, control unit 4 controls power supply 30 of heater 3 to adjust the amount of power supplied to heat generating unit 3B (step S5). For example, if temperature T2 is higher than temperature T1, the power supplied to heat generating unit 3B is reduced or the power supply to heat generating unit 3B is stopped. If temperature T2 is lower than temperature T1, the power supplied to heat generating unit 3B is increased.

[0077] After controlling the heater 3, the control unit 4 determines whether or not the heating of the wafer has been completed (step S6). The completion of heating is determined, for example, by the passage of time. If the time since the start of the wafer heat treatment has reached a predetermined time or more, it is determined that the processing such as film formation on the wafer has been completed, i.e., that it is no longer necessary to heat the wafer. If the heating of the wafer has not been completed, the control unit 4 returns to the processing of step S1. If the heating of the wafer has been completed, the control unit 4 ends the temperature adjustment.

[0078] The differential thermocouple 6 that measures the temperature difference ΔT does not have the problem of measurement error of each temperature sensor 7 that occurs when measuring the temperature T1 of the first zone Z1 and the temperature T2 of the second zone Z2 using two independent temperature sensors 7. Therefore, in the wafer heating apparatus 1 of this example, the temperature T1 of the first zone Z1 and the temperature T2 of the second zone Z2 can be made to match with high precision based on the temperature difference ΔT obtained by the differential thermocouple 6. In particular, in a configuration in which the temperature T1 of the first zone Z1 is controlled and the temperature T2 of the second zone Z2 obtained based on the temperature T1 and the temperature difference ΔT is controlled, both the temperature T1 of the first zone Z1 and the temperature T2 of the second zone Z2 are easily adjusted to the target temperatures accurately.

[0079] By carrying out the above-described temperature adjustment control for all of the outer peripheral zones, it is possible to make the temperature of the entire mounting plate 2 almost uniform. Therefore, the wafer heating apparatus 1 of this embodiment can heat the entire wafer uniformly.

[0080] In this example, the total number of wires extending from the configuration for measuring the temperatures of the five heating zones is seven. Specifically, the number of wires extending from the temperature detector 5 is five (51W, 52W, 53W, 54W, 55W), and the number of wires extending from the temperature sensor 7 is two. If a temperature sensor 7 were to be disposed in each of the five heating zones, the total number of wires would be ten, and connecting the wires to the detection unit 8 would be complicated.

[0081] Second Embodiment In a second embodiment, a wafer heating apparatus 1 will be described in which the temperature sensor 7 is removed from the configuration of the first embodiment.

[0082] The wafer heating apparatus 1 of the second embodiment does not include a temperature sensor 7. Therefore, the wafer heating apparatus 1 of this example does not require the time and effort of preparing the temperature sensor 7 and connecting the sensor wire 7W (FIG. 3) extending from the temperature sensor 7 to the detection unit 8.

[0083] Heating zone 2A, which is a central zone located in the center of mounting plate 2, is surrounded by heating zones 2B, 2C, 2D, and 2E, which are peripheral zones. This makes it easy to stabilize the temperature of heating zone 2A, and the amount of power supplied to heat generating unit 3A that heats heating zone 2A and the temperature of heating zone 2A tend to correlate. For example, by supplying power to heat generating unit 3A according to a predetermined power supply pattern, the temperature of heating zone 2A is easily maintained at the target temperature. Therefore, heating zone 2A can be maintained at the target temperature even without a temperature sensor 7 for measuring the temperature of heating zone 2A.

[0084] On the other hand, the temperature of the peripheral zone is easily affected by the external environment and therefore fluctuates. Therefore, in this example, the heater 3 is controlled based on the temperature difference ΔT between the central zone and each peripheral zone so that the temperature of the peripheral zone approaches the temperature of the central zone. An example of a wafer heating method based on this control will be described with reference to the flowchart of FIG. 5. In the following description, an example will be described in which the control unit 4 of the wafer heating apparatus 1 controls the heating zones 2A and 2B. In this case, the heating zone 2A is the first zone Z1, and the heating zone 2B is the second zone Z2.

[0085] The control unit 4 determines the temperature difference ΔT between the temperature T1 of the first zone Z1 and the temperature T2 of the second zone Z2 based on real-time information from the differential thermocouple 6 measured by the detection unit 8 (step S1 in Figure 5).

[0086] The control unit 4 determines whether the temperature difference ΔT exceeds a predetermined value (step S2). The predetermined value may be zero. If the predetermined value is set to a small value, the temperature T1 of the first zone Z1 and the temperature T2 of the second zone Z2 can be made to match with high accuracy. If the temperature difference ΔT is equal to or less than the predetermined value, the control unit 4 maintains the amount of power supplied to the heater 3 without changing it, and returns to the processing of step S1.

[0087] If the temperature difference ΔT exceeds a predetermined value, the control unit 4 controls the power supply 30 of the heater 3 so that the temperature difference ΔT approaches 0, and adjusts the amount of power supplied to the heat generating unit 3B (step S3). For example, if the temperature T2 is higher than the temperature T1, the amount of power supplied to the heat generating unit 3B is reduced or power supply to the heat generating unit 3B is stopped. If the temperature T2 is lower than the temperature T1, the amount of power supplied to the heat generating unit 3B is increased.

[0088] After controlling the heater 3, the control unit 4 determines whether or not the heating of the wafer has been completed (step S4). If the heating of the wafer has not been completed, the control unit 4 returns to the process of step S1. If the heating of the wafer has been completed, the control unit 4 ends the temperature adjustment.

[0089] By carrying out the above-described temperature adjustment control for all of the outer peripheral zones, it is possible to make the temperature of the entire mounting plate 2 almost uniform. Therefore, the wafer heating apparatus 1 of this embodiment can heat the entire wafer uniformly.

[0090] <Embodiment 3> In embodiment 3, a wafer heating apparatus 1 having a different configuration of the temperature detector 5 from embodiment 1 will be described with reference to Figure 6. The way to view Figure 6 is the same as in Figure 2. In this example, differences from embodiment 1 will be described, and a description of the same configuration as embodiment 1 will be omitted. In describing this example, Figure 1 will be referred to as appropriate.

[0091] The temperature detector 5 shown in Fig. 6 differs from the temperature detector 5 of the first embodiment in that it does not have the metal wire 5A and the lead wire 51W shown in Fig. 2. In this configuration, the temperature difference ΔT between any two of the four measuring units 52, 53, 54, and 55 is measured. For example, the temperature difference ΔT between measuring unit 52 and measuring unit 53 is measured.

[0092] In the wafer heating apparatus 1 of this example, the temperature of the central heating zone 2A is managed based on information from the temperature sensor 7. Meanwhile, the temperatures of the peripheral heating zones 2B, 2C, 2D, and 2E are managed based on information from the differential thermocouples 6 that constitute the temperature measuring element 5. As an example of the management of the temperatures of the peripheral zones, an example will be described in which the control unit 4 of the wafer heating apparatus 1 controls the heating zones 2B and 2C. In this case, the heating zone 2B is the first zone Z1, and the heating zone 2C is the second zone Z2.

[0093] The control unit 4 supplies power to the heat generating unit 3B to heat the first zone Z1 and to the heat generating unit 3C to heat the second zone Z2. The correlation between the amount of power supplied to the heat generating unit 3A and the temperature T1 of the first zone Z1, and the correlation between the amount of power supplied to the heat generating unit 3C and the temperature T2 of the second zone Z2 are determined in advance. The control unit 4 adjusts the amount of power based on these correlations, thereby adjusting the temperatures T1 and T2 to values ​​that are generally close to the target temperatures. Therefore, in this example, the heater 3 is controlled so that the temperatures T1 and T2 are approximately the same. Specifically, the heater 3 is controlled so that the temperature difference ΔT between the first zone Z1 and the second zone Z2 approaches zero, according to the flowchart of FIG. 5 described in the second embodiment.

[0094] By carrying out the above-described temperature adjustment control for all outer peripheral zones, it is possible to make the temperature of the entire mounting plate 2 uniform. The temperature adjustment control of this example is simple, and it is easy to quickly make the temperature of the entire mounting plate 2 uniform.

[0095] Other Embodiments The wafer heating apparatus 1 equipped with the temperature detector 5 may be used for pre-baking in a photolithography process, or for an inspection process for measuring the electrical characteristics of a wafer.

[0096] If the mounting plate 2 is equipped with a cooling mechanism, the temperature of the heating zones 2A, 2B, 2C, 2D, and 2E may be adjusted by the cooling mechanism. In this case, the heat generating portion of the heater 3 may be a single heat generating portion disposed on the entire surface of the heater plate 23.

[0097] Additionally, in the wafer heating apparatus 1 equipped with the temperature detector 5, the temperatures of the heating zones 2A, 2B, 2C, 2D, and 2E can be controlled to be different from one another by changing the control program of the control unit 4. For example, the temperature of the central heating zone 2A can be made higher or lower than the temperatures of the other heating zones 2B, 2C, 2D, and 2E.

[0098] REFERENCE SIGNS LIST 1 Wafer heating device 2 Placement plate 2A, 2B, 2C, 2D, 2E Heating zone 2L Lower surface 2U Upper surface 21 Top plate 22 Sensor plate 23 Heater plate 3 Heater 3A, 3B, 3C, 3D, 3E Heat generating part 3W Power line 30 Power supply 4 Control part 5 Temperature measuring element 5A, 5B, 5C, 5D, 5E, 5X, 5Y Metal wire 50 Intersection 51, 52, 53, 54, 55 Measuring part 51W, 52W, 53W, 54W, 55W Conductor 6 Differential thermocouple 61 First metal wire 62 Second metal wire 63 Third metal wire 65 First measuring part 66 Second measuring part 61W, 63W Conductor 7 Temperature sensor 7W Sensor wire 8 Detection part 9 Support Z1 First Zone Z2 Second Zone

Claims

1. A wafer heating apparatus comprising: a mounting plate having an upper surface on which a wafer is placed; a heater disposed inside the mounting plate; and a temperature sensor disposed inside the mounting plate, wherein the mounting plate has a plurality of heating zones when viewed from above, and the temperature sensor includes a differential thermocouple that measures a temperature difference ΔT between a first zone and a second zone which are different from each other in the plurality of heating zones.

2. The wafer heating apparatus according to claim 1, further comprising a temperature sensor disposed in said first zone, said temperature sensor being a resistance temperature detector or a thermocouple.

3. A wafer heating apparatus as described in claim 1 or claim 2, wherein the support plate has a circular plate shape, the plurality of heating zones comprise a circular central zone and at least one peripheral zone arranged on the periphery of the central zone, the central zone being the first zone, and the at least one peripheral zone being the second zone.

4. The wafer heating apparatus according to claim 3, wherein said at least one peripheral zone comprises a plurality of peripheral zones surrounding said central zone, and each of said plurality of peripheral zones is said second zone.

5. A wafer heating device as described in any one of claims 1 to 4, wherein the mounting plate comprises, in order from above, a top plate having the upper surface, a sensor plate having the differential thermocouple, and a heater plate having the heater, the top plate, the sensor plate, and the heater plate are joined together, and the differential thermocouple is formed by a metal wire printed on the sensor plate.

6. A wafer heating apparatus as described in any one of claims 1 to 5, further comprising a control unit for controlling the heater, the heater comprising a plurality of heat generating elements disposed in each of the plurality of heating zones, each of the plurality of heat generating elements being controlled by the control unit.

7. A wafer heating apparatus as described in claim 6, further comprising a temperature sensor disposed in the first zone, wherein the control unit determines a temperature T2 of the second zone based on a temperature T1 of the first zone obtained by the temperature sensor and the temperature difference ΔT obtained by the differential thermocouple, and controls the heater so that the temperature T2 becomes a target temperature.

8. The wafer heating apparatus according to claim 6, wherein the control unit determines the temperature difference ΔT based on an output voltage of the differential thermocouple, and controls the heater so that the temperature difference ΔT approaches zero.

9. A wafer heating method for heating a wafer placed on an upper surface of a mounting plate using a wafer heating device comprising a mounting plate, a heater arranged inside the mounting plate, and a temperature measuring element arranged inside the mounting plate, wherein the mounting plate has a plurality of heating zones when viewed from above, and the temperature measuring element includes a differential thermocouple for measuring a temperature difference ΔT between a first zone and a second zone which are independent from each other in the plurality of heating zones, the method comprising: controlling the heater so that a temperature T1 of the first zone becomes a target temperature; determining a temperature T2 of the second zone based on the temperature T1 and the temperature difference ΔT, and controlling the heater so that the temperature T2 becomes the target temperature.

10. A wafer heating method for heating a wafer placed on an upper surface of a mounting plate using a wafer heating device comprising a mounting plate, a heater arranged inside the mounting plate, and a temperature measuring element arranged inside the mounting plate, wherein the mounting plate has a plurality of heating zones when viewed from above, the temperature measuring element includes a differential thermocouple that measures a temperature difference ΔT between a first zone and a second zone that are independent of each other in the plurality of heating zones, and the heater is controlled so that the temperature difference ΔT approaches zero.

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