KR20230112715A - Heater control device and power control method - Google Patents

Abstract

A body, a heating element disposed in the body, and a power controller controlling AC power supplied to the heating element, wherein the power controller controls the AC power by a first control method in which a phase control method and a cyclic control method are combined, wherein the phase control method passes a current through the switching element in a passage time between a time when a trigger signal is input to the switching element and a zero cross point of the AC voltage waveform, every half cycle of the AC voltage waveform, and the cyclic control method is, every half cycle of the AC voltage waveform. , control whether output of the current passing through the switching element is possible, and the passage time is equal to or longer than a cut-off time set in advance corresponding to a fluctuation range of the zero-cross point detected by the power controller.

Description

Heater control device and power control method

The present disclosure relates to a heater control device and a power control method.

This application claims the priority based on international application PCT/JP2021/046389 of December 15, 2021, and uses all the description content described in the said international application.

Patent Literature 1 discloses a film forming apparatus for forming a metal thin film on a semiconductor wafer. This film forming apparatus includes a heating unit installed on the mounting table, a temperature detector for detecting the temperature of a semiconductor wafer placed on the mounting table, a control unit for controlling the amount of heat generated by the heating unit, and a supporting member supporting the lower portion of the mounting table. The heating means includes a first heater and a second heater for respectively heating the central portion and the peripheral portion of the semiconductor wafer. The control unit controls power supplied to the first heater based on the temperature detection value of the central portion of the mounting table. Further, the control means is configured to supply the second heater with electric power at a predetermined ratio with respect to the supplied electric power of the first heater.

Patent Literature 2 has phase control and cycle control as AC power control, and discloses a method of eliminating each other's drawbacks by switching and using these.

Patent Document 1: Japanese Unexamined Patent Publication No. 2009-74148 Patent Document 2: Japanese Utility Model Publication No. 63-122818

The heater control device of the present disclosure,

gas and

A heating element disposed in the body;

A power controller controlling AC power supplied to the heating element;

The power controller controls the AC power by a first control method in which a phase control method and a cyclic control method are combined;

The phase control method passes a current through the switching element in a passage time between a time when a trigger signal is input to the switching element and a zero cross point of the AC voltage waveform for each half cycle of the AC voltage waveform,

The cyclic control method controls the output availability of the current passing through the switching element for each half cycle of the AC voltage waveform,

The passage time is greater than or equal to a cut-off time previously set corresponding to the fluctuation range of the zero-cross point detected by the power controller.

The power control method of the present disclosure,

A power control method for controlling AC power supplied to a load, comprising:

Controlling the AC power by a first control method in which a phase control method and a cyclic control method are combined;

The phase control method passes a current through the switching element in a passage time between a time when a trigger signal is input to the switching element and a zero cross point of the AC voltage waveform for each half cycle of the AC voltage waveform,

The cyclic control method controls the output availability of the current passing through the switching element for each half cycle of the AC voltage waveform,

The passage time is equal to or longer than a preset cutoff time corresponding to the variation range of the zero-cross point.

1 is a functional block diagram of a heater control device according to Embodiment 1. FIG.
Fig. 2 is a plan view of the base showing the arrangement area of the heating element.
Fig. 3 is a longitudinal sectional view showing the arrangement of heating elements in the body.
4 is an explanatory diagram explaining the difference between the normal phase control method and the first control method.
Fig. 5 is a flowchart showing the processing sequence up to outputting the second electric power in the first embodiment.
Fig. 6 is a flowchart showing the processing procedure up to outputting the second temperature in the first embodiment.
7 is a graph showing an example of the temperature profile of the heating element in Embodiment 1.
8 is a graph showing an example of the temperature profile of the heating element during temperature maintenance.
9 is a graph showing an example of a temperature profile in the processing state of FIG. 8 in an enlarged manner.
10 is an explanatory diagram explaining a first control method of the heater control device according to the second embodiment.
11 is a functional block diagram of a heater control device according to a third embodiment.
Fig. 12 is a flowchart showing the processing sequence up to outputting the second electric power in the third embodiment.
Fig. 13 is a plan view of the body showing the arrangement area of the heating element in Modification Example 1;
Fig. 14 is a longitudinal sectional view of the base body showing the arrangement area of the heating element in Modification Example 1;
15 is a functional block diagram of a heater control device according to a second modification.
16 is a functional block diagram of a heater control device according to a third modification.

[Problems to be solved by the present disclosure]

In the film forming apparatus, it is required to control the electric power supplied to the heater installed on the mounting table with very fine precision so that the temperature of the semiconductor wafer reaches a desired temperature. That is, control with high resolution of power control and low power is required. However, in the phase control, it is difficult to control the low power due to the detection fluctuation of the zero-cross point.

One object of the present disclosure is to provide a heater control device capable of controlling power of a heating element with high resolution and low power. In addition, one of the objects of the present disclosure is to provide a power control method capable of controlling low power with high resolution of power control of a load.

[Effect of the present disclosure]

The heater control device of the present disclosure can finely control the power supplied to the heating element. The power conversion method of the present disclosure can finely control the power supplied to the load.

《Description of Embodiments of the Present Disclosure》

Hereinafter, embodiments of the present disclosure are enumerated and described.

(1) The heater control device of one aspect of the present disclosure,

gas and

A heating element disposed in the body;

A power controller controlling AC power supplied to the heating element;

The power controller controls the AC power by a first control method in which a phase control method and a cyclic control method are combined;

The phase control method passes a current through the switching element in a passage time between a time when a trigger signal is input to the switching element and a zero cross point of the AC voltage waveform for each half cycle of the AC voltage waveform,

The cyclic control method controls the output availability of the current passing through the switching element for each half cycle of the AC voltage waveform,

The passage time is greater than or equal to a cut-off time previously set corresponding to the fluctuation range of the zero-cross point detected by the power controller.

Compared to the case of only the phase control method, the first control method can effectively reduce the manipulated variable MV as a time average value even if the zero-cross point fluctuates as described later in detail. Therefore, the first control method can supply less power to the heating element compared to the case of only the phase control method. Therefore, the heater control device has high resolution of power control of the heating element and can control low power, so that it is easy to control the wafer to a desired temperature.

(2) In the heater control device of (1) above,

The cyclic control method outputs current at an output ratio of M times among the number of half cycles of N times,

The AC power supplied to the heating element may be power determined by the transit time and the output ratio in the phase control method.

In this aspect, the resolution of power control of the heating element is high, and control of low power is possible.

(3) In the heater control device of (1) or (2) above,

The power controller may perform the first control method when supplying power to the heating element corresponding to a time shorter than the cutoff time.

With the above configuration, since the power control resolution is high and low power control is possible, it is easier to control the wafer to a desired temperature.

(4) In the heater control device of any one of (1) to (3) above,

The time width of the trigger signal may be shorter than the passage time.

In this form, the time for outputting the current is longer than the time width of the trigger signal, but the power can be precisely controlled.

(5) In the heater control device of any one of (1) to (4) above,

The said passage time may have a some passage time from which the length of time differs.

Compared to the case where the length of the passage time is single, the resolution of the power control of the heating element is high and low power control is possible.

(6) In the heater control device of any one of (1) to (5) above,

The body has a disk-shaped shape,

The heating element,

A first heating element disposed in a region including the center of the gas;

having at least one second heating element disposed concentrically with the first heating element;

The power controller has a first power controller for controlling a first power supplied to the first heating element;

The first power controller may control the first power by the first control method.

In this aspect, the first power supplied to the first heating element is controlled by the first control method, so that the first power can be controlled more precisely than when the power is controlled only by the normal phase control method.

(7) In the heater control device of (6) above,

At least one current sensor for measuring the current supplied to the at least one second heating element;

Equipped with an operator for obtaining the temperature of the second heating element,

The power controller has a second power controller that controls second power supplied to the second heating element;

The second power controller controls the second power by the first control method so as to have a preset ratio with respect to the first power;

The calculating unit may calculate the temperature of the second heating element based on the measured value of the current sensor.

In this form, the temperature of the second heating element is obtained by a calculator based on the measured value of the current sensor. Therefore, the temperature of the second heating element can be grasped even without a temperature sensor for detecting the temperature of the second heating element or the zone in which the second heating element is disposed. The second electric power supplied to the second heating element is controlled to be at a preset ratio with respect to the first electric power. In this aspect, since the second power is controlled by the first control method, the temperature of the second heating element can be controlled more precisely than when the power is controlled only by the normal phase control method. As a result, the temperature of the second heating element can also be grasped very precisely.

(8) The power control method of one aspect of the present disclosure,

A power control method for controlling AC power supplied to a load, comprising:

Controlling the AC power by a first control method in which a phase control method and a cyclic control method are combined;

The phase control method passes a current through the switching element in a passage time between a time when a trigger signal is input to the switching element and a zero cross point of the AC voltage waveform for each half cycle of the AC voltage waveform,

The cyclic control method controls the output availability of the current passing through the switching element for each half cycle of the AC voltage waveform,

The passage time is equal to or longer than a preset cutoff time corresponding to the variation range of the zero-cross point.

Compared to the case of only the phase control method, the first control method can effectively reduce the manipulated variable MV as a time average value. Therefore, the power control method can supply a small amount of power to the load compared to the case of only the phase control method. Accordingly, the power control method described above has a high resolution of power control of the load and enables control of small power, so that it is easy to control the load to a desired temperature.

<<Details of Embodiments of the Present Disclosure>>

Details of the heater control device of the embodiment of the present disclosure will be described below. The same reference numerals in the drawings indicate the same designations. The size, positional relationship, etc. of the members shown in each drawing are expressed for the purpose of clarifying the description, and do not necessarily represent actual dimensional relationships.

<<Embodiment 1>>

[Heater control device]

Referring to FIGS. 1 to 4 , a heater control device 1 according to Embodiment 1 will be described. This heater control device 1 can be used for a film forming device that forms a thin film on the surface of a wafer. In the film forming apparatus, a substrate 10 and a support 20 are disposed in a heater control apparatus 1 in a chamber capable of controlling atmospheric gas. The illustration of the chamber is omitted. In FIG. 1, each heating element 30 has a portion in the circumferential direction of the base 10 where it is not disposed, but in an actual device, the heating element 30 is arranged throughout the base 10 without gaps.

[Full configuration]

As shown in FIG. 1, the heater control device 1 of this example includes a base 10, a support 20, a plurality of heating elements 30, a temperature sensor 40, a current sensor 50, and a controller 60. As shown in FIG. 3 , the body 10 includes a first surface 10a on which a heating object W is disposed, and a second surface 10b facing the first surface 10a. In the following description, the side of the first surface 10a of the body 10 is referred to as "upper", and the side of the second surface 10b is referred to as "lower" in some cases. The support 20 is attached to the lower side of the body 10 . As shown in FIGS. 1 and 3 , the plurality of heating elements 30 are arranged inside the body 10 . The plurality of heating elements 30 of this example include one first heating element 31 and one or more second heating elements 32 . In this example, for convenience of description, a case in which one second heating element 32 is provided will be described as an example. The temperature sensor 40 detects the temperature of the first heating element 31 . The current sensor 50 includes a first current sensor 51 that measures a first current flowing through the first heating element 31 and a second current sensor 52 that measures a second current flowing through the second heating element 32. The controller 60 mainly controls power supplied to the first heating element 31 and the second heating element 32 . One of the characteristics of the heater control device 1 of Embodiment 1 is that it has a specific power controller 63 that controls the power supplied to the heating element 30 . Hereinafter, each configuration will be described in detail.

[gas]

The body 10 of this example has a disk-like shape. The body 10 has a first surface 10a and a second surface 10b. The first surface 10a and the second surface 10b face each other. On the first surface 10a, a heating target W shown in FIG. 3 is disposed. The heating object W is, for example, a silicon or compound semiconductor wafer. A support body 20 described later is attached to the second surface 10b. A plurality of holes into which a plurality of terminals 30t shown in FIG. 3 are fitted are formed in the second surface 10b.

As shown in Fig. 2, the body 10 of this example is concentrically divided into a plurality of regions. The body 10 is partitioned into an inner region 10i and an outer region 10e. The inner region 10i is a circular region centered on the center of the body 10 . The center of the base 10 refers to the center of a circle constituted by the outline of the base 10 in a plan view of the base 10 from the first surface 10a side. The diameter of the inner region 10i is 80% or less of the diameter of the base body 10, for example. When the diameter of the inner region 10i is 80% or less of the diameter of the base body 10, an area in which one or more second heating elements 32 can be disposed outside the first heating element 31 can be secured. The diameter of the inner region 10i is further 50% or less of the diameter of the base body 10 . The diameter of the inner region 10i is 10% or more of the diameter of the base body 10, for example. When the diameter of the first heating element 31 is 10% or more of the diameter of the base body 10, an area in which the first heating element 31 can be disposed in the center of the base body 10 can be secured. That is, the diameter of the inner region 10i is 10% or more and 80% or less, and 10% or more and 50% or less of the diameter of the substrate 10. The outer region 10e is an annular region located outside the inner region 10i. Corresponding to the plurality of regions, a plurality of heat generating elements 30 described later are disposed.

The material of the body 10 is known ceramics, for example. Ceramics are, for example, aluminum nitride, aluminum oxide, and silicon carbide. The material of the body 10 may be composed of a composite material of the above ceramics and metal. The metal is, for example, aluminum, an aluminum alloy, copper, or a copper alloy. The material of the body 10 in this example is ceramics.

[support]

As shown in FIGS. 1 and 3 , the support body 20 supports the base body 10 from the second surface 10b side. The support body 20 is attached to the second surface 10b so as to surround the plurality of terminals 30t shown in FIG. 3 when the heater control device 1 is viewed as a flat surface from the first surface 10a side. The shape of the support 20 is not particularly limited. The support 20 of this example is a cylindrical member. The support 20 is arranged concentrically with the body 10 . In this example, the base body 10 and the support body 20 are connected so that the center of the cylindrical support body 20 and the center of the disk-shaped base body 10 are coaxial.

As shown in FIG. 3, the upper end of the support body 20 has a flange portion 21 bent outward. In this example, a sealing member (not shown) is disposed between the flange portion 21 of the upper end and the second surface 10b. The inside of the support body 20 is sealed by the said sealing member. Unlike this example, the flange portion 21 and the second face 10b may be bonded to each other in order to keep it airtight without using the seal member. A corrosive gas is typically filled in the chamber in which the gas 10 and the support 20 are disposed. By keeping the inside of the support body 20 airtight, the plurality of terminals 30t, the plurality of power lines 30c, and the like accommodated inside the support body 20 can be isolated from corrosive gas.

The material of the support body 20 is known ceramics, similarly to the material of the base body 10. The material of the support body 20 and the material of the body 10 may be the same or different.

[First heating element and second heating element]

One first heating element 31 and one or more second heating elements 32 are heat sources that heat the heating target W through the gas 10 . As shown in FIGS. 1 and 3 , the first heating element 31 is disposed in a circular area including the center of the body 10, that is, in an inner area 10i shown in FIG. 2 . One or more second heating elements 32 are arranged concentrically with the base body 10 and the first heating element 31 as shown in FIGS. 1 and 3 . One or more second heating elements 32 are disposed in an annular region concentric with the center of the base body 10, that is, in an outer region 10e shown in FIG. 2 . The first heat generating element 31 and one or more second heat generating elements 32 are arranged in a layered manner at intervals from each other in the thickness direction of the base body 10 . When a plurality of second heating elements 32 are provided, the individual second heating elements 32 are also arranged in layers at intervals in the thickness direction of the base body 10 . Each of the first heating element 31 and one or more second heating elements 32 is connected to the power line 30c via a terminal 30t shown in FIG. 3 . Power is supplied from an AC power source (not shown) to each of the first heating element 31 and the one or more second heating elements 32 through the power line 30c. In this example, the second heating element 32 is one. As shown in Modification 1 described later, a plurality of second heating elements 32 may be provided.

The shapes of the first heating element 31 and the second heating element 32 are not particularly limited. When the base body 10 is viewed as a plane from the first surface 10a side, the shape of the outer circumferential outline of the first heat generating element 31 and the second heat generating element 32 is generally circular. The first heating element 31 and the second heating element 32 are disposed concentrically with the base body 10 and the support body 20 . The first heating element 31 and the second heating element 32 are arranged concentrically with each other. The concentric type here means that when the heater control device 1 is viewed in a plane from the first surface 10a side, the envelopes of the first heating element 31 and the second heating element 32 have a common center, and the diameters of the respective envelopes are different. The center of each envelope coincides with the center of the body 10. The diameter of the envelope of the second heating element 32 is larger than that of the first heating element 31 . When the base body 10 is viewed in plan from the first surface 10a side, the first heating element 31 and the second heating element 32 may be arranged to partially overlap in the radial direction of each envelope circle, or may be arranged at intervals without overlapping. In this specification, the center side refers to the center side of the envelope circle, and the outer side refers to the side away from the center in the radial direction of the envelope circle.

The 1st heating element 31 and the 2nd heating element 32 are arrange|positioned inside the base body 10, as shown in FIG.1 and FIG.3. The first heat generating element 31 is disposed on the first layer located at the furthest side of the first surface 10a in the thickness direction of the base body 10 . Since the first heat generating element 31 is disposed on the first layer, a long distance between the first heat generating element 31 and the second surface 10b can be secured. In addition, since the first heating element 31 is disposed on the first floor, it is less affected by the position of the terminal 30t connected to the second heating element 32 and easier to arrange the first heating element 31 than when the first heating element 31 is disposed on a floor other than the first layer. The second heat generating element 32 is disposed closer to the second surface 10b than the first heat generating element 31 .

The material of each heating element 30 is not particularly limited as long as it is a material capable of heating the heating target W to a desired temperature. The material of each heating element 30 is a known metal suitable for resistance heating. The metal is, for example, one selected from the group consisting of stainless steel, nickel, nickel alloys, silver, silver alloys, tungsten, tungsten alloys, molybdenum, molybdenum alloys, chromium, and chromium alloys. A nickel alloy is, for example, nichrome.

Each heating element 30 can be manufactured by combining a screen printing method and a hot press joining method, for example. In the case of this example, it can manufacture in the following procedure. Three ceramic substrates and a screen mask capable of transferring each heating element 30 are prepared. As the screen mask, one capable of fabricating each circuit pattern of the first heating element 31 and the second heating element 32 is used. A screen mask of a circuit pattern to be produced is placed on each of the two ceramic substrates. The paste to be the heating element 30 is applied to the ceramic substrate on which the screen mask is placed. The heating element 30 is transferred to the ceramic substrate using a squeegee. After transferring the heating element 30, the screen mask is removed. As a result of the above, the first substrate onto which the first heating element 31 is transferred and the second substrate onto which the second heating element 32 is transferred are obtained. The first substrate, the second substrate, and the ceramic substrate on which the heating element is not transferred are sequentially bonded and bonded by hot press. By this bonding, each heating element 30 is arranged inside the base body 10 .

[temperature Senser]

The temperature sensor 40 is a sensor that measures the first temperature of the first heating element 31 . For the temperature sensor 40, a commercially available thermocouple or resistance thermometer can be suitably used. The RTD is, for example, PT100, which is a platinum RTD.

The placement location of the temperature sensor 40 is inside the body 10. In this example, the temperature sensor 40 is arrange|positioned in the area|region inside the base|substrate 10 inside the inner peripheral surface of the support body 20, when base|substrate 10 is considered flat. That is, when the support 20 is viewed in the axial direction, the temperature sensor 40 is located inside the contour of the inner circumferential surface of the support 20 . In particular, the temperature sensor 40 may be disposed near the first heating element 31 . The temperature measured by the temperature sensor 40 installed near the first heating element 31 is not the temperature of the first heating element 31 itself, but the temperature of the inner region 10i of the base body 10 in which the first heating element 31 is disposed. However, the temperature of the inner region 10i is also regarded as the first temperature of the first heating element 31 .

[current sensor]

The current sensor 50 is a sensor that measures the current flowing through the heating element 30 . In this example, the current sensor 50 includes a first current sensor 51 and a second current sensor 52 . The first current sensor 51 detects a first current flowing through the first heating element 31 . The second current sensor 52 detects a second current flowing through the second heating element 32 . When the second heating element 32 is plural, the second current sensor 52 is installed on each second heating element 32 . The first current sensor 51 is installed on the power line 30c connected to the first heating element 31 . The second current sensor 52 is installed on the power line 30c leading to the second heating element 32 . As the current sensor 50, a sensor represented by a commercially available CT (Current Transmitter) can be used. In this example, the first current or the second current is a value obtained by averaging the effective values of the currents flowing through the first heating element 31 or the second heating element 32 within a predetermined period of time and removing electrical noise.

[controller]

The controller 60 controls each part necessary for the operation of the heater control device 1 . The controller 60 includes a first temperature controller 61, a power controller 63, an arithmetic unit 65, and a memory 66. Each process by the controller 60 is realized by a processing circuit including one or a plurality of processors. In addition to the one or more processors, the processing circuit may be composed of one or a plurality of memories 66, various analog circuits, integrated circuits in which various digital circuits are combined, or the like, and may include an input/output I/F (Interface). The memory 66 stores programs (commands) for executing each of the above processes in the one or more processors. The memory 66 is typically a ROM (Read-Only Memory) or a RAM (Random Access Memory). The one or more processors may execute each process according to the program read from the one or more memories 66, or may execute each process according to a logic circuit designed to execute each process in advance. The processor may be various processors suitable for computer control, such as a central processing unit (CPU), graphics processing unit (GPU), digital signal processor (DSP), field programmable gate array (FPGA), application specific integrated circuit (ASIC), and the like. Further, the plurality of physically separated processors may cooperate with each other to execute the respective processes. For example, the processors installed in each of a plurality of physically separated computers may execute the respective processes in cooperation with each other via a network such as a LAN (Local Area Network), WAN (Wide Area Network), and the Internet. The program may be installed into the memory from an external server device or the like via the network, or may be distributed in a state stored in a recording medium such as a CD-ROM (Compact Disc Read Only Memory), DVD-ROM (Digital Versatile Disk Read Only Memory), or semiconductor memory, and installed into the memory from the recording medium. The power controller 63 of this example has a first power controller 631 and a second power controller 632 . The program includes program codes related to processing in the first temperature controller 61, the first power controller 631, the second power controller 632, and the calculator 65.

(first temperature controller)

The first temperature controller 61 outputs a first control signal so that the first temperature approaches the target temperature. For control in the first temperature controller 61, PID control can be used. PID control is a type of feedback control, and is a control method in which control of an input value is performed by three operations: a deviation (P) between an output value and a target value, and an integral (I) and derivative (D) of the output value. Smooth temperature control with little hunting can be performed by the proportional operation that outputs the manipulated variable according to the deviation. Integral operation can automatically correct the offset. It is possible to quickly respond to disturbances by differential operation.

The target temperature is a temperature set by the user. The first temperature controller 61 performs a PID operation based on the target temperature and the current temperature of the first heating element 31, that is, the first temperature, and outputs a first control signal to the first power controller 631.

(first power controller)

The first power controller 631 controls first power, that is, AC power supplied to the first heating element 31 according to a first control signal. The first power controller 631 to which the first control signal is input supplies the first power corresponding to the first control signal to the first heating element 31 . Control of the first power is performed by the first control method. The first control method is a control method in which a phase control method and a cyclic control method are combined.

The phase control method is a method of controlling current to pass through a switching element at a passage time between the time when a trigger signal is input to the switching element and the time at the zero cross point of the AC voltage waveform for each half cycle of the AC voltage waveform. As a more specific example, the phase control method changes the conduction angle by controlling the firing angle according to the timing at which the trigger signal is input to the switching element for each half cycle of the AC voltage waveform to control the current to pass until the zero cross point of the AC voltage waveform.

A specific example of the switching element is a thyristor or a triac. A triac is an element in which two thyristors are connected in anti-parallel. The triac is efficient because it can control the current in both directions by opening and closing one gate. A trigger signal is a signal with a fixed time width. The time width of the trigger signal is shorter than the passage time. A specific example of the trigger signal is a gate signal. The firing angle is the time during which the switching element is turned off. The conduction angle is the time during which the switching element is turned on. The zero cross point is detected by the detector 64. The detector 64 is provided in the first power controller 631 . A specific example of the detector 64 may be a photocoupler or an AC voltage zero-cross detection IC that does not use a photocoupler. An AC voltage zero-cross detection IC is, for example, ROHM's BM1ZxxxFJ series. By using the AC voltage zero-cross detection IC, there are advantages such as higher precision of zero-cross detection.

The passage time is the time when the switching element is turned on, and is the time t _MV during which the current actually flows. The transit time is greater than or equal to the cutoff time. The cut-off time is a time previously set corresponding to the fluctuation range of the zero-cross point detected by the detector 64 as will be described later. The range of variation of the zero cross point varies depending on the environment in which the heater control device 1 is used. Therefore, the cut-off time can be appropriately set according to the use environment of the heater control device 1 . The fluctuation range of the zero-cross point depends on the above usage environment, but is, for example, less than or equal to ±3 Hz. For example, when the frequency fluctuation range is ±3 Hz when the frequency is 60 Hz, the fluctuation range at the zero-cross point is the sum of the absolute values of the difference between the time of a half cycle of 57 Hz and the time of a half cycle of 60 Hz, and the absolute value of the difference between the time of a half cycle of 63 Hz and the time of a half cycle of 60 Hz, which is 0.835 msec. In this case, the cutoff time is 0.835 msec. That is, assuming that the frequency is 60 Hz and the upper limit of the fluctuation range of the zero-cross point is a time span corresponding to ±3 Hz, the cutoff time is 0.835 msec or less.

The output mode at the time of phase control is voltage proportional square control. The voltage proportional square control is a mode in which the square of the effective value Vrms of the output voltage is proportional to the manipulated variable MV (%) corresponding to the degree of gate opening. When the operation phase angle θ (deg) in FIG. 4 is 180 deg, the operation phase angle θ (%) is 100%. The manipulated variable MV (%) and the manipulated phase angle θ (%) have a relationship of MV = θ/100 - (1/2π) sin (2θπ/100).

The cyclic control method is a method in which the output availability of the current passing through the switching element is controlled for every half cycle of the AC voltage waveform. As a specific example, the cyclic control method is a method of controlling power output availability by turning on or off a gate at a zero cross point. That is, in the cyclic control method, current is output at an output ratio of M times among the number of half cycles of N times. N is determined as an average voltage in consideration of a time constant allowed for control objects and resolution of control. N is, for example, an integer of 5 or more and 1200 or less, and is an integer of 5 or more and 120 or less, particularly an integer of 10 or more and 30 or less. M is an integer of 1 or more and less than N.

The first power is power determined by the ratio between the transit time in the phase control method and the output ratio in the cyclic control method. The first power is calculated by multiplying the first current and the first voltage. The first current is the measured value of the first current sensor 51 as described above. The first voltage is a voltage applied to the first heating element 31 . Specifically, the first power is calculated by dividing the square of the first voltage by the resistance. More specifically, the first power is calculated by multiplying a value obtained by dividing the square of the voltage of a power supply, which is the primary side of the transformer 80 described later, by the resistance, and the manipulated variable MV (%). This calculation is obtained by an arithmetic unit 65 described later.

In particular, the control of the first electric power by the first control method is effective when the first electric power corresponding to a time shorter than the cutoff time is supplied to the first heating element 31 . When the passage time as the object of control is shorter than the cut-off time, malfunctions tend to occur as will be described later. If the first control method is used when supplying power corresponding to a time shorter than the cutoff time to the heating element, it is particularly effective for controlling low power. Depending on the configuration of the power controller 63, only the phase control method may be used for control corresponding to a time equal to or longer than the cutoff time. In this embodiment, power control is always performed by the first control method.

Before explaining the first control method, a normal phase control method will be described based on the top view of FIG. 4 . Next, the first control method will be described based on the bottom view of FIG. 4 . The top view and the bottom view of FIG. 4 show the waveform of the supply voltage from an AC power supply as a sine wave. Among the sine waves in Fig. 4, the current in the region indicated by hatching is output.

In the normal phase control method shown in the top view of Fig. 4, when a gate signal having a time width tw is input to the gate of the triac at a predetermined time of each half cycle, the gate is opened. When the gate is opened, the triac is turned on and current flows. The time width tw is constant. After the gate signal of the time width tw is inputted, the gate signal is turned OFF. Even when the gate signal is off, the triac remains on and current continues to flow. When the triac senses zero voltage, the triac automatically turns off and no current flows. In each half cycle, the time during which the triac is turned on is the time during which the current actually flows, t _MV (msec). Depending on the timing of applying the gate signal, the triac can output a desired current within a predetermined range. The output current decreases as the timing for giving the gate signal is closer to the time of detecting the next zero-cross point, and the output current increases as the point is farther from the time of detecting the next zero-cross point.

If the detector 64 detects the zero-cross point before the elapse of the time width tw after the gate signal turns on, that is, when 0 < t _MV < tw, and the gate signal is kept on during the time width tw, the triac may turn on again beyond the zero-cross point. Therefore, when the zero cross point is detected, the gate signal is turned off. However, there are cases where the zero-cross point cannot be detected because the voltage waveform is distorted or the like. In this case, if the actual zero-cross point is crossed, the triac is turned on again, causing a malfunction in which current continues to flow over a period of half a cycle.

Therefore, it is conceivable to prevent the occurrence of the above malfunction by forcibly turning off the gate signal at the scheduled time of the next zero-cross point. The scheduled time to become the next zero-cross point is about 8.33 msec after the current zero-cross point in the case of, for example, 60 Hz. However, the actual time of the next zero-cross point is a time before or after the scheduled time. The reason why the time of the zero-cross point fluctuates is that there are cases where the frequency is disturbed and there are cases where the voltage waveform is deformed due to disturbance. When the time t _MV is small, if the actual time of the next zero-cross point comes earlier than the scheduled time, the above malfunction is likely to occur. Therefore, in the phase control method, as for the time t _MV that is the purpose of control, there is a practical minimum time t _MV . The cut-off time is a time determined in advance in consideration of a time corresponding to this minimum time t _MV . That is, when the manipulated variable MV becomes smaller than the value corresponding to the minimum time t _MV , it is necessary to devise not to turn on the gate signal. The cutoff time may be determined based on frequency fluctuations of AC power to be controlled. In addition, the cut-off time may be determined by actually measuring an alternating voltage waveform to be controlled by the heater control device 1 and determining the range of variation at the zero-cross point.

The first control method will be described based on the bottom view of FIG. 4 . The phase control method of the first control method is the same as the normal phase control method described above based on the top view of FIG. 4 . In the phase control method of the first control method, the time at which the gate signal is input every half cycle is "time t ₀ + half cycle (msec) - time t _MV ". Time t ₀ is the time when the zero-cross point was detected by the detector 64. The time width tw of the gate signal is shorter than the time t _MV . As described above, the cyclic control method controls whether or not the current is output for each half cycle of passing through the triac.

In the bottom view of FIG. 4, waveforms for 5 cycles are shown for convenience of description. Here, five cycles are described as one unit. Also, the number of cycles per unit can be appropriately set. The first control method can adjust the manipulated variable MV by the number of cycles per unit and the number of permitting current output per unit by the cyclic control method.

In the first control method shown in the bottom view of FIG. 4 , of the 10 half-cycle currents that have passed through the triac, the cyclic control method permits the output of 8 half-cycle currents and rejects the output of 2 half-cycle currents. In contrast, in the normal phase control system shown in the top view of Fig. 4, current was output in each of the 10 half cycles. That is, the manipulated variable MV of the first control method shown in the lower view of FIG. 4 is 8/10 times the manipulated variable MV of the normal phase control method shown in the upper view of FIG. 4 . Even if the time t _MV in units of half cycles is not changed from the normal phase control method, the manipulated variable MV in the first control method is 8/10 times the minimum manipulated amount MV in the normal phase control method. Therefore, the first control method can make the manipulated variable MV smaller than that of the normal phase control method alone.

Although not shown, the first control method may permit the output of one half-cycle current out of the 10 half-cycle currents that have passed through the triac and reject the output of nine half-cycle currents, for example, by the cyclic control method. In this case, the manipulated variable MV can be 1/10 times that in the case of only the normal phase control method. Therefore, the resolution of power control can be increased to 10 times that of only the normal phase control method. For example, when considering control of 60 Hz AC power, that is, 60 cycles of AC power for 1 second, by treating 120 half cycles as one unit, it is possible to control with a precision of 1/120 of the minimum amount of operation MV in the normal phase control method.

The first power controller 631 may use only the first control method. Alternatively, the first power controller 631 may use the first control method only when the manipulated variable MV is smaller than the manipulated variable MV of the normal phase control method only, and may use the normal phase control method or the normal cyclic control method when the manipulated amount MV is made larger than the manipulated variable MV of the normal phase control method only.

Compared to the case of only the normal phase control method, the first control method can effectively reduce the manipulated variable MV as a time average value even if the zero-cross point fluctuates. Therefore, since the first electric power supplied to the first heating element 31 is controlled by the first control method, the first control method can supply a small amount of first power to the first heating element 31 compared to the case of controlling power only by the normal phase control method. Accordingly, in the first control method, since the power control resolution of the first heating element 31 is high and low power control is possible, it is easy to control the wafer to a desired temperature.

(Second power controller)

The second power controller 632 controls the second power that is AC power supplied to the second heating element 32 . More specifically, the second power controller 632 controls the second power to have a preset ratio with respect to the first power. Control by the power ratio is less susceptible to changes in resistance due to self-heating of each heating element 30 compared to control by the current ratio. Therefore, the temperature of the second heating element 32 can be grasped accurately. This ratio is a ratio preset by the user. For example, the ratio of the first power to the second power is set to 1.0:0.8. When the number of second heating elements 32 is plural, the second power of each second heating element 32 is also controlled to be a preset ratio with respect to the first power. For example, when the number of second heating elements 32 is two, first power:second power A:second power B = 1.0:0.8:0.6. The second electric power A is the second electric power supplied to one of the two second heat generating elements 32 . The second electric power B is the second electric power supplied to the other second heating element 32 of the two second heating elements 32 .

Different ratios can be set in a series of temperature profiles of heating, maintaining, and decreasing the temperature of the heating element 30 . Usually, this ratio is different in each step at the time of temperature increase, temperature maintenance, and temperature decrease. At the time of temperature rise and the time of temperature fall, between the start and end of each step, the ratio may differ according to the temperature range. For example, from room temperature to 400°C, the first power:second power is 1.0:0.8, and from 400°C to 450°C, the first power:second power is 1.0:0.9. When the temperature rises at the same power rate and becomes high, the heating element 30 becomes excessively center-hot, and there is a possibility that it is damaged due to thermal stress due to the difference between the inside and outside of its own in-plane temperature distribution. Therefore, the ratio of the second power may be increased at a high temperature.

Control of the second power is performed by the first control method, that is, a control method in which a cyclic control method is combined with a phase control method, similarly to the control of the first power. As described above, the first control method can reduce the manipulated variable MV compared to the case of only the normal phase control method. Therefore, the second electric power supplied to the second heating element 32 is controlled by the first control method, so that a small second electric power can be supplied to the second heating element 32 similarly to the first electric power. Therefore, since the power control resolution of the second heating element 32 is high and low power control is possible, it is easy to control the wafer to a desired temperature. The second power is obtained by multiplying the second current and the second voltage. The second current is a measured value of the second current sensor 52 . The second voltage is a voltage applied to the second heating element 32 . This calculation is performed by an arithmetic unit 65 described later.

(computer)

The calculator 65 performs various calculations required by the controller 60. As described above, calculations of the first power and the second power are all performed by the calculator 65. In addition, the calculator 65 also calculates the second temperature, which is the temperature of the second heating element 32 . Therefore, even if there is no temperature sensor for detecting the temperature of the second heating element 32 or the temperature of the zone corresponding to the second heating element 32, the temperature of the second heating element 32 can be grasped.

The second temperature of the second heating element 32 is obtained using a coefficient representing the relationship between the resistance of the second heating element 32 and the resistance of the second heating element 32 and the temperature obtained in advance. That is, the second temperature is not a value measured using a temperature sensor, but a value calculated based on the power supplied to the first heating element 31 . The resistance of the second heating element 32 is obtained by dividing the second voltage of the second heating element 32 by the second current flowing through the second heating element 32 . The coefficient is obtained in advance by a preliminary test described later. This coefficient also includes a relational expression representing the relationship between the resistance of the second heating element 32 and the temperature. The coefficients are stored in the memory 66. If the relationship between the resistance and the temperature of the second heating element 32 is known in advance, when the resistance of the second heating element 32 is obtained, the second temperature of the second heating element 32 can be calculated and obtained by referring this resistance to the above relationship.

(Memory)

The memory 66 is a memory for storing programs, and various nonvolatile memories can be suitably used. The memory 66 may also include a volatile memory for temporarily storing values required for a series of calculations.

[Other constituent members]

As other members, the heater control device 1 includes an external output device 70 and a transformer 80 .

The external output device 70 is a device that outputs the second temperature of the second heating element 32 obtained as described above. The external output device 70 is, for example, a display that displays the second temperature in letters or displays a change in the second temperature with time as a graph. The other external output device 70 may be a device that outputs a process result obtained by performing a predetermined process on the second temperature. A device indicating the result of this processing is, for example, an alarm device. The alarm device is a device that issues an alarm when, for example, the second temperature is out of a predetermined range. The alarm is not particularly limited as long as it can notify the user of the abnormality of the second temperature. Specific types of alarms include text display on a display, lighting of a lamp, and sounding of a buzzer. Another external output device 70 is a communication device not shown. This communication device communicates with an external device possessed by a remote user. For example, information of the second temperature may be sent to an external device by the communication device, or the alert may be transmitted to the external device as a state change of a flag by the communication device. By transmitting this information, a remote user can recognize a second temperature or an alarm.

The transformer 80 is a member for electromagnetically coupling a power source (not shown) and the controller 60 to supply power to the first heating element 31 and the second heating element 32 . The power supply side, which is the primary side of the transformer 80, and the controller 60 side, which is the secondary side of the transformer 80, are not electrically connected and are insulated from each other. Since the power source and the controller 60 are insulated from each other, it is easy to control the power to each heating element 30 . In this example, electric power is supplied to each of the heating elements 30 by branching the power line 30c on the secondary side to each of the first heating element 31 and the second heating element 32 . That is, the first heating element 31 and the second heating element 32 are not electrically insulated from each other. Since the first heating element 31 and the second heating element 32 are not insulated, the number of transformers 80 can be reduced compared to the case where both heating elements 30 are insulated.

As other members, the heater control device 1 may include an input unit not shown. The input unit is a device for inputting various conditions set by the user. Various conditions include a preset ratio with respect to the first power to define the second power. For the input unit, for example, a known input device such as a ten key, a keyboard, or a touch panel can be used. Various conditions input from the input unit are stored in the memory 66.

[processing order]

Based on FIGS. 5 and 6 , the processing procedure of the heater control device 1 will be described. 1 is referred to for each constituent member.

First, based on FIG. 5 , the processing sequence from outputting the first electric power to the first heating element 31 and outputting the second electric power to the second heating element 32 will be described. In step S1, a first temperature is obtained from the temperature sensor 40, and a first current is acquired from the first current sensor 51. In step S2, the first temperature controller 61 outputs a first control signal so that the first temperature approaches the target temperature. In step S3, the first power controller 631 outputs the first power corresponding to the first control signal to the first heating element 31. Then, in step S4, the calculator 65 calculates the second power, and further outputs the second power from the second power controller 632 to the second heating element 32. A series of processes from step S1 to step S4 are repeatedly performed at regular intervals while the heater control device 1 is being driven.

Next, based on FIG. 6, the processing procedure until a 2nd temperature is calculated|required and output is demonstrated. In step S11, a second current is acquired by the second current sensor 52. In step S12, the second resistance, which is the resistance of the second heating element 32, is calculated by the calculator 65 from the second current and the second voltage. In step S13, the second temperature is calculated by the calculator 65 using the calculated second resistance and the coefficient representing the relationship between the resistance of the second heating element 32 and the temperature obtained in advance. In step S14, the obtained second temperature is output to the external output device 70.

[Preliminary exam]

The preliminary test is a test for obtaining in advance a coefficient representing the relationship between the resistance of the second heating element 32 and the temperature. It is preferable to perform a preliminary test by different methods at the time of temperature raising and temperature lowering, and the time of temperature holding. That is, it is preferable to use different coefficients at the time of temperature rise and temperature decrease, and at the time of temperature maintenance.

Before explaining the method for obtaining this coefficient, the temperature profile from the temperature increase to the temperature decrease is explained based on FIG. 7 . FIG. 7 is a graph showing the change in temperature of the first heating element 31 in the heater control device 1 of the present example with time.

First, in the temperature raising process, the temperature of the heating element 30 rises at a substantially constant rate from room temperature to a predetermined holding temperature. The rate at which the heat generating element 30 is not damaged is selected as the temperature increase rate in this temperature increase process.

In the temperature maintenance process, the temperature of the heating element 30 is maintained at a substantially constant temperature. The temperature maintaining process includes an idle state in which no wafer is placed on the base 10 and a processing state in which a wafer is placed on the base 10 and a film is formed on the wafer. In the idle state, extremely minute temperature fluctuations occur due to gas flow in and out of the film forming apparatus and control of power supplied to each heat generating element 30 described above. In the graph of Fig. 7, the idle state is indicated by a straight line extending horizontally, but in reality, as will be described later, extremely small temperature fluctuations occur. On the other hand, in the processing state, since wafers are deposited and loaded onto the base 10 to sequentially form a film on a plurality of wafers, a larger temperature fluctuation occurs than in the idle state. The temperature change in the processing state is indicated by a broken line following the straight line in the idle state in FIG. 7 .

When the temperature is lowered, the temperature of the heating element 30 decreases at a substantially constant rate from the holding temperature to the room temperature. The rate at which the heating element 30 is not damaged is selected as the rate of temperature decrease in this temperature decrease process.

In the above temperature profile, the method of obtaining the coefficient at the time of temperature rise and the time of temperature decrease is explained first, and then the method for obtaining the coefficient at the time of temperature holding is explained.

(when the temperature is raised and when the temperature is lowered)

At the time of temperature rise and the time of temperature decrease, the amount of temperature change per unit time is large compared with the time of temperature hold|maintenance. During this temperature rise and fall, no film forming process is performed on the wafer. In this case, the temperature range from room temperature to the maintenance temperature or the temperature range from the maintenance temperature to room temperature is divided into narrower temperature regions, and the relationship between the resistance and temperature of the second heating element 32 is obtained for each divided temperature region. For example, the relationship between the resistance and temperature of the second heating element 32 is obtained for each partitioned temperature region having a range of 50°C to 100°C. More specifically, when the temperature is raised, the relationship between the resistance and the temperature of the second heating element 32 is obtained for each of the first temperature range of 50 ° C. or more and 100 ° C., the second temperature region of 100 ° C. or more and 200 ° C., the third temperature region of 200 ° C. or more and 300 ° C., the fourth temperature region of 300 ° C. or more and 400 ° C. or less, and the fifth temperature region of 400 ° C. or more and the holding temperature or less. An example of the holding temperature is 450°C. For example, in the first temperature range, the relationship between resistance and temperature at two points of 50°C and 100°C is obtained. Here, two measurement points, that is, the temperature T1 of the second heating element 32 at the resistance R(T1) on the low temperature side and the temperature T2 of the second heating element 32 at the resistance R(T2) on the high temperature side are expressed by a proportional relational expression. Using this relational expression, the temperature T of the second heating element 32 with resistance R is obtained by the following equation.

T={(T2-T1)/(R(T2)-R(T1))}×(R-R(T1))+T1

However, T1≤T≤T2, R(T1)≤R≤R(T2).

The relationship between the resistance of the second heating element 32 and the temperature may be obtained in the same way as when the temperature is increased during the temperature decrease. In this way, in each process of temperature rise and temperature decrease, the temperature range from the room temperature to the holding temperature or the temperature range from the holding temperature to the room temperature is divided into smaller temperature regions. Then, the relationship between the resistance and the temperature of the second heating element 32 is obtained for each narrow range of temperature regions. In that way, different coefficients can be used for each segmented temperature region. Therefore, the temperature of the second heating element 32 can be obtained more precisely.

In contrast, for example, the temperature of the second heating element 32 at the resistance R(Tr), that is, room temperature Tr, and the holding temperature Tk of the second heating element 32 at the resistance R(Tk) are also represented by a proportional relational expression. Using this relational expression, the temperature T of the second heating element 32 with the resistance R is obtained by the following equation.

T={(Tk-Tr)/(R(Tk)-R(Tr))}×(R-R(Tr))+Tr

However, Tr≤T≤Tk and R(Tr)≤R≤R(Tk).

In this case, in the relational expression between the resistance and temperature of the second heating element 32 obtained from two points, room temperature and holding temperature, the resistance value at the intermediate temperature cannot be expressed by linear interpolation between the two points. Therefore, it is difficult to accurately obtain the temperature of the second heating element 32 .

(when maintaining temperature)

During temperature maintenance, the rate of temperature change per unit time is extremely small compared to when the temperature is raised or when the temperature is lowered. Therefore, during temperature maintenance, the relationship between the resistance of the second heating element 32 and the temperature may be obtained in a narrower temperature band than during temperature rise or temperature decrease. As described above, the temperature maintaining process includes two temperature profiles of an idle state without a heating target W and a processing state with a heating target W. This temperature profile is demonstrated based on FIG.

8 is a graph showing changes in the temperature of the first heating element and the temperature of the second heating element over time. The temperature of the first heating element 31 is a temperature determined based on the resistance of the first heating element 31 determined from the first current and the first voltage and the above coefficient. The temperature of the second heating element 32 is a temperature determined based on the coefficient and the resistance of the second heating element 32 determined from the second current and the second voltage. In this graph, the change over time of the measured value of the temperature sensor 40 is also shown together. All graphs have overlapping lines. In this graph, the process in the idle state is referred to as Case 1, and the process in the processing state is referred to as Case 2. As shown in this graph, in the idle state, gas flows in and out of the chamber of the film forming apparatus, and as a result of temperature control by the first temperature controller 61, an extremely small temperature movement is confirmed. On the other hand, in the processing state, since wafers are loaded and unloaded into the chamber, a greater temperature movement is observed than in the idle state. Since a plurality of overlapping lines appear in the graph of FIG. 8 , for example, the temperature amplitude in an idle state in which a plurality of overlapping lines appears is large. However, the amplitudes of the individual graph lines are smaller. In particular, the amplitude of each graph is clearly smaller in the idle state than in the processing state. In this temperature maintenance process, there are a method for obtaining a coefficient based on a temperature profile in a processing state and a method for obtaining a coefficient based on a temperature profile in an idle state. Hereinafter, each is explained in order.

<Method A (Processing state: with heating target)>

First, the resistance value Rmax of each heating element 30 at the time of the maximum temperature Tmax and the resistance value Rmin of each heating element 30 at the time of the minimum temperature Tmin are confirmed from the change over time of the measured value of the temperature sensor 40 within a predetermined time in the processing state. The predetermined time is selected from a range of about 500 seconds to about 1000 seconds. The predetermined time in this example is 600 seconds. Within this predetermined time, film formation is performed on one wafer. FIG. 9 is an enlarged view of a part of the temperature change in the processing state of FIG. 8 . The minimum temperature Tmin is a valley temperature between taking out a wafer on which the film formation process has been completed and from now until the current wafer to be subjected to the film formation process is placed on the substrate 10 . The maximum temperature Tmax is the peak temperature while film formation processing is being performed on the current wafer. 9 shows that the minimum temperature Tmin is 449.4°C and the maximum temperature Tmax is 450.3°C. The resistance value Rmax and the resistance value Rmin of each heating element 30 are values obtained by dividing the first voltage at each point in time by the first current, or the value obtained by dividing the second voltage at each point in time by the second current. Using these maximum temperature Tmax, resistance value Rmax, minimum temperature Tmin and resistance value Rmin, the relational expression of the temperature and resistance value of each heating element 30 is calculated|required. This relational expression is obtained in the same way as the relational expression shown at the time of temperature rise and the time of temperature decrease.

In method A, since the relational expression is obtained based on the resistance value Rmax, the maximum temperature Tmax, the minimum temperature Tmin, and the resistance value Rmin in the processing state of the wafer, the temperature of the second heating element 32 obtained using the relational expression can be grasped very precisely.

When the relationship between the resistance and the temperature of the heat generating element 30 is obtained in the preliminary test by the above method A, the relationship is obtained based on the temperature profile in a state simulating actual film formation. Therefore, the temperature of the second heat generating element 32 can be grasped with high accuracy.

<Method B (Processing state: With heating target)>

First, the average resistance Rave within a predetermined period of time is obtained from the change over time in the resistance value of each heating element 30 within a predetermined period of time in a processing state. The predetermined time is appropriately selected from, for example, a range of about 5000 seconds to about 10000 seconds. In this example, the predetermined time is 8000 seconds. Within this predetermined time, film formation is performed on 10 or more wafers. Next, the change rate ΔR/R of the resistance of each heating element 30 within a predetermined time is set in advance. First, the maximum resistance Rmax and the minimum resistance Rmin within a predetermined time are determined, and the difference ΔR between the maximum resistance Rmax and the minimum resistance Rmin and the ratio ΔR/Rave of the difference ΔR to the average resistance Rave are obtained. Let this ratio (DELTA)R/Rave be the change rate (DELTA)R/R. For example, here, the rate of change ΔR/R is set to 0.02. On the other hand, the average temperature Tave within a predetermined time is similarly obtained for the measured value of the temperature sensor 40. In addition, the temperature change amount ΔT within a predetermined time is set in advance. As for the temperature change amount ΔT, first, the difference between the maximum temperature Tmax and the minimum temperature Tmin within a predetermined time is obtained as the temperature change amount ΔT. For example, here, the temperature change amount ΔT is 0.88°C. The ratio ΔR/R and the amount of change in temperature ΔT can be considered to be substantially constant for each heating element 30, provided that the holding temperature does not change greatly. The fact that the holding temperature does not change significantly means, for example, that the amount of change in the holding temperature is 100°C or less.

In the subsequent film formation, the average resistance Rave and the average temperature Tave of each heating element 30 may be obtained. That is, the maximum resistance Rmax, the minimum resistance Rmin, the maximum temperature Tmax, and the minimum temperature Tmin after the next time are obtained as follows.

ΔR=Rave×0.02

Maximum resistance Rmax=Rave+ΔR/2

Minimum resistance Rmin=Rave-ΔR/2

Maximum temperature Tmax=Tave+ΔT/2

Minimum temperature Tmin=Tave-ΔT/2

In this way, before the first film formation, it is necessary to obtain the maximum resistance Rmax, minimum resistance Rmin, maximum temperature Tmax, and minimum temperature Tmin in advance. However, in the second and subsequent film formation, the maximum resistance Rmax, the minimum resistance Rmin, the maximum temperature Tmax, and the minimum temperature Tmin can be obtained using the known resistance change rate ΔR/R and temperature change ΔT. When each of these parameters is obtained, the correlation between the resistance and temperature of the heating element 30 can be obtained.

<Method C (idle state: no heating target)>

First, the average resistance Rave within a predetermined period of time is obtained from the change over time in the resistance value of each heating element 30 within a predetermined period of time in an idle state. The predetermined time is appropriately selected from, for example, a range of about 5000 seconds to about 10000 seconds. In this example, the predetermined time is 10000 seconds. Next, the change rate ΔR/R of the resistance of each heating element 30 within a predetermined time is set in advance. First, the maximum resistance Rmax and the minimum resistance Rmin within a predetermined time are determined, and the difference ΔR between the maximum resistance Rmax and the minimum resistance Rmin and the ratio ΔR/Rave of the difference ΔR to the average resistance Rave are obtained. Let this ΔR/Rave be the resistance change rate ΔR/R. For example, here, the rate of change ΔR/R is set to 0.02. On the other hand, the average temperature Tave within a predetermined time is similarly obtained for the measured value of the temperature sensor 40. In addition, the temperature change amount ΔT within a predetermined time is set in advance. As for the temperature change amount ΔT, first, the difference between the maximum temperature Tmax and the minimum temperature Tmin within a predetermined time is obtained as the temperature change amount ΔT. For example, here, the temperature change amount ΔT is 0.88°C. The ratio ΔR/R and the amount of change in temperature ΔT can be considered to be substantially constant for each heating element 30, provided that the holding temperature does not change greatly. The fact that the holding temperature does not change significantly means, for example, that the amount of change in the holding temperature is 100°C or less.

In the subsequent film formation, the average resistance Rave and the average temperature Tave of each heating element 30 may be obtained. That is, the maximum resistance Rmax, the minimum resistance Rmin, the maximum temperature Tmax, and the minimum temperature Tmin after the next time are obtained as follows.

ΔR=Rave×0.02

Maximum resistance Rmax=Rave+ΔR/2

Minimum resistance Rmin=Rave-ΔR/2

Maximum temperature Tmax=Tave+ΔT/2

Minimum temperature Tmin=Tave-ΔT/2

In this way, before the first film formation, it is necessary to obtain the maximum resistance Rmax, minimum resistance Rmin, maximum temperature Tmax, and minimum temperature Tmin in advance. However, in the second and subsequent film formation, the maximum resistance Rmax, the minimum resistance Rmin, the maximum temperature Tmax, and the minimum temperature Tmin can be obtained using the known resistance change rate ΔR/R and temperature change ΔT. In addition, since the temperature of the second heating element 32 can be obtained based on the coefficient obtained when there is no object W to be heated in the idle state, there is no need to prepare a wafer in obtaining the coefficient. When each of these parameters is obtained, the correlation between the resistance and temperature of the heating element 30 can be obtained.

When the temperature is maintained, the temperature of the second heating element 32 can be accurately obtained by using the coefficient according to the fine temperature range of the maximum temperature and the minimum temperature in the process.

At the time of the preliminary test, by obtaining the coefficient in a state where the wafer is not placed on the base body 10, there is no need to prepare the wafer. Further, in the preliminary test, the waste of the wafer can be reduced compared to the case where the wafer is formed into a film and the coefficient is obtained.

If the relationship between the resistance and the temperature of the heating element 30 is determined by the method B and method C described above in the preliminary test, it is not necessary to actually measure the maximum resistance Rmax, the minimum resistance Rmin, the maximum temperature Tmax, and the minimum temperature Tmin during the second and subsequent operation of the heater control device 1. Therefore, the temperature of the 2nd heating element 32 can be calculated|required more simply.

<<Embodiment 2>>

[Heater control device]

Referring to Fig. 10, a heater control device according to Embodiment 2 will be described. In FIG. 10, as in FIG. 4, waveforms for 5 cycles are shown for convenience of description. Embodiment 1 explained an example in which the length of the passage time, that is, the length of time t _MV is constant in the first control method. In contrast to this, in Embodiment 2, in the first control method, the length of the passage time, that is, the length of time t _MV includes a plurality of passage times different from each other. The following description is mainly made on differences from Embodiment 1. Description of common points with Embodiment 1 is omitted.

The plurality of passage times of this embodiment include two passage times of a first passage time and a second passage time. The first transit time is time t _MV1 . The second transit time is time t _MV2 . Time t _MV2 is shorter than time t _MV1 . In other embodiments different from the present embodiment, the plurality of passage times may include three or more passage times having different lengths of time t _MV .

In the first control method shown in FIG. 10 , as in the bottom view of FIG. 4 , among the 10 half-cycle currents that have passed through the triac, the cyclic control method permits the output of 8 half-cycle currents and rejects the output of 2 half-cycle currents. Among the currents of the eight half cycles for which output is allowed, the time during which the current flows in each of the six half cycles is time t _MV1 , and the time during which the current flows in each of the two half cycles is time t _MV2 . The manipulated variable MV in this case is “(first manipulated variable MV1×6+second manipulated variable MV2×2)/10”. The first manipulated variable MV1 is a value corresponding to time t _MV1 which is the first passage time. The second manipulated variable MV2 is a value corresponding to time t _MV2 which is the second passage time. When the time t _MV1 shown in FIG. 10 is equal to the time t _MV shown in the bottom view of FIG. 4 , the manipulated variable MV of the first control method shown in FIG. 10 is smaller than the manipulated variable MV of the first control method shown in the bottom view of FIG. 4 . That is, the heater control device of the present embodiment can increase the resolution of power control of the heating element and can control low power compared to the heater control device of the first embodiment. If it is a heater control device according to another embodiment including three or more passage times with different lengths of time t _MV , the resolution of the power control of the heating element can be further increased and the control of low power is possible.

<<Embodiment 3>>

[Heater control device]

Referring to Fig. 11, a heater control device 1 according to Embodiment 3 will be described. In Embodiment 1, the heater control device 1 capable of grasping the second temperature, which is the temperature of the second heating element 32, or monitoring that the second temperature becomes an abnormal temperature, has been described. On the other hand, in Embodiment 3, the heater control device 1 capable of controlling the temperature of the second heating element 32 by controlling the second electric power by changing the ratio described above will be described. The following description is mainly made about the difference from Embodiment 1. Description of common points with Embodiment 1 is omitted.

The heater control device 1 of Embodiment 3 further includes a second temperature controller 62 in addition to the configuration of Embodiment 1. The second temperature controller 62 outputs a second control signal for adjusting the ratio so that the second temperature approaches the target temperature. Control for adjusting this ratio can also use PID control. According to the second control signal, the second power controller 632 adjusts a ratio for obtaining the second power. Although the ratio is first power : second power = 1.0 : 0.8, when the second temperature is lower than the target temperature, it is necessary to increase the second power. In this case, for example, first power:second power = 1.0:0.81. Conversely, when the second temperature is higher than the target temperature, it is necessary to lower the second power. In this case, for example, first power:second power = 1.0:0.79. The fluctuation range of this ratio can be appropriately set, but it may be within 5% of the ratio of the second electric power before the change. In the above example, since the ratio of the second power before the change is 0.8, the ratio of the second power after the change is changed between 0.76 and 0.84. When a power fluctuation deviating from the fluctuation range of this ratio occurs, a warning device (not shown) issues a warning to the user. With this warning, the user can detect an abnormality and deal with it appropriately.

The processing procedure in Embodiment 3 will be described based on FIG. 12 . This processing sequence is performed subsequent to step S3 in FIG. 5 . In step S21, the second control signal for adjusting the ratio is output by the second temperature controller 62 so that the second temperature approaches the target temperature. In step S22, the calculator 65 calculates the second power according to the adjusted ratio. Then, the second power is output from the second power controller 632 to the second heating element 32 .

The heater control device 1 of Embodiment 3 can not only display the second temperature of the second heating element 32 on the external output device 70, but also can control the temperature of the second heating element 32.

<<Embodiment 4>>

[Heater control device]

In Embodiment 4, the ratio for obtaining the second power is controlled so that the difference between the second temperature and the first temperature becomes zero as much as possible. The configuration of the heater control device of Embodiment 4 is the same as that of the heater control device 1 of Embodiment 3 described with reference to FIG. 11 . In Embodiment 3, the temperature Ts measured by the temperature sensor 40 is regarded as the temperature Th of the first heating element 31 itself, and is set as the first temperature. That is, strictly speaking, the temperature Th of the first heating element 31 is different from the temperature Ts measured by the temperature sensor 40 . This is because the temperature Ts transiently includes a temperature increase due to heat generation of the first heating element 31 itself.

In order to more accurately control the temperature distribution of each heating element 30, it is necessary to consider that the first temperature and the second temperature include a minute temperature increase due to self-heating of the heating element 30. Therefore, the difference between the second temperature and the first temperature is regarded as a difference in temperature distribution within the first surface 10a. Strictly speaking, the first temperature and the second temperature each have different target temperatures. By controlling the second power by adjusting the ratio so that the difference in the temperature distribution is the difference between the respective target temperatures of the second temperature and the first temperature, more precise temperature control of each heating element 30 is possible. As in Embodiment 3, when a power fluctuation deviating from the fluctuation range of this ratio occurs, an alert device (not shown) issues a warning to the user. With this warning, the user can detect an abnormality and deal with it appropriately.

<<Modified example 1>>

[Heater control device]

Referring to Figs. 13 and 14, the heater control device 1 of Modification 1 will be described. Modification 1 is a configuration that can be applied to any of Embodiments 1 to 4. In Modification 1, there are 6 independently temperature-controlled zones in the body 10. That is, the body 10 is provided with a circular inner region 10i located in the center of the body 10, an intermediate region 10m located outside the inner region 10i, and an outer region 10e located outside the intermediate region 10m. In Modification 1, the outer region 10e is divided in the circumferential direction of the body 10. The number of second heating elements 32 provided in the divided outer region 10e may be plural. The number of divisions in this example is four. Each zone of the outer region 10e is a fan-shaped zone obtained by dividing the annular region into quarters. A first heating element 31 is provided in the inner region 10i, one second heating element 32 is provided in the middle region 10m, and four second heating elements 32 are provided in the outer region 10e. Second heating elements 32 are disposed in each zone of the outer region 10e divided into quarters. Each heating element 30 can independently control the supplied power. A current sensor (not shown) is installed on each power line 30c connected to each heating element 30 .

In the heater control device 1 of Modification 1, by using the second power controller 632, it is possible to realize heating of the substrate 10 by using more heating elements 30 than in the first to third embodiments.

<<Modification 2>>

[Heater control device]

Referring to Fig. 15, the heater control device 1 of Modification 2 will be described. Modification 2 is a modification of Embodiment 1, and has a configuration in which the first heating element 31 and the second heating element 32 are insulated.

As shown in Fig. 15, in Modification 2, a first transformer 81 and a second transformer 82 are provided between the first heating element 31 and the power supply and between the second heating element 32 and the power supply, respectively. That is, the primary sides of the first transformer 81 and the second transformer 82 are connected to a power line branched from a power source. Meanwhile, the secondary sides of the first transformer 81 and the second transformer 82 are connected to power lines 30c independent of each other. Therefore, the first heating element 31 and the second heating element 32 are insulated from each other.

The heater control device 1 of the modified example 2 can insulate the first heat generating element 31 and the second heat generating element 32 more reliably in addition to the same effect as that of the first embodiment.

<<Modified Example 3>

[Heater control device]

Referring to FIG. 16, the heater control device 1 of Modification Example 3 will be described. Modification 3 is a modification of Embodiment 3 or Embodiment 4, and has a configuration in which the first heating element 31 and the second heating element 32 are insulated.

As shown in Fig. 16, in Modification 3, a first transformer 81 and a second transformer 82 are provided between the first heating element 31 and the power supply and between the second heating element 32 and the power supply, respectively. That is, the primary sides of the first transformer 81 and the second transformer 82 are connected to a power line branched from a power source. Meanwhile, the secondary sides of the first transformer 81 and the second transformer 82 are connected to power lines 30c independent of each other. Therefore, the first heating element 31 and the second heating element 32 are insulated from each other.

The heater control device 1 of Modification Example 3 can insulate the first heating element 31 and the second heating element 32 more reliably, in addition to the same effects as those of the third or fourth embodiment.

<Example 1>

In Embodiment 1, the difference in power control capability between the first control method described in Embodiment 1 and the normal phase control method is explained.

In this example, an example in which the number of half cycles per unit is set to 15 in a 60 Hz AC voltage waveform will be described. Set the fluctuation width of the zero-cross point to a time equivalent to ±3 Hz. That is, the cutoff time is set to a time equivalent to ±3 Hz. The specific cutoff time is the sum of the absolute value of the difference between the half cycle time of 57 Hz and the half cycle time of 60 Hz and the absolute value of the difference between the time of the half cycle of 63 Hz and the half cycle time of 60 Hz. The cutoff time in this example is 0.835 msec. Since the manipulated variable MV corresponding to this cutoff time is 0.649%, the minimum set manipulated variable MV of the triac is set to 0.65%. That is, the set manipulated variable MV can be set to 0.65% or more, but cannot be set to less than 0.65%.

In the normal phase control method, the set manipulated variable MV and the assumed manipulated variable MV created when the set manipulated variable MV are equal to each other. This is because in the normal phase control method, all currents of 15 half cycles passing through the triac are output. That is, in the normal phase control method, if the set manipulated variable MV is 0.65%, for example, the assumed manipulated variable MV is 0.65%. The assumed manipulated variable MV is actually output power. As described above, since the set manipulated variable MV cannot be made less than 0.65%, the assumed manipulated variable MV cannot be made less than 0.65% only with the normal phase control method. If the assumed power output when the assumed manipulated variable MV is 0.65% is 30.0 W, the normal phase control method cannot make the assumed power less than 30.0 W.

Meanwhile, in the first control method, the set manipulated variable MV and the assumed manipulated variable MV may be different from each other. In the first control method, the set manipulated variable MV cannot be less than 0.65% as described above, but unlike the normal phase control method, as shown in Table 1, the assumed manipulated variable MV can be made less than 0.65%. Table 1 shows an example in which the assumed manipulated variable MV is changed in units of 0.01% from 0.65% to 0.05%. In the first control method of this example, as shown in Table 1, the assumed power can be less than 30.0 W. Table 1 shows an example in which the assumed electric power is changed in units of 0.5 W or 0.4 W from 30.0 W to 2.3 W. The number of times of output is the number of times that output of current is permitted by the cyclic control system among the currents of 15 half cycles that have passed through the triac. The number of times of no output is the number of times the current output is rejected by the cyclic control method among the 15 half-cycle currents that have passed through the triac. For example, if the number of times of output is 14 and the number of times of no output is 1, it means that among the 15 half-cycle currents that have passed through the triac, the output of 14 half-cycle currents is permitted and the output of one half-cycle current is rejected by the cyclic control method.

For example, as shown in the second row from the top of Table 1, when the set manipulated variable MV is set to 0.69%, the number of outputs is 14, and the number of non-outputs is set to 1, the assumed manipulated variable MV can be set to 0.64% (= 0.69×(14/15)). The assumed electric power when the assumed manipulated variable MV is 0.64% is 29.5 W (= 30.0 × (0.64/0.65)). In this way, it is possible to output desired electric power with high resolution by combining the set manipulated variable MV by the phase control method and output control by the cyclic control method.

In this way, according to the first control method of Embodiment 1, by setting the cutoff time to a time equivalent to ±3 Hz, the above-described malfunction does not occur, and the resolution of the assumed manipulated variable MV can be increased compared to the normal phase control method, and low power can be controlled. In addition, even in the first control method in the heater control device 1, when a frequency fluctuation equivalent to ±4 Hz is given, the above-described malfunction occurs.

《Example 2》

In Embodiment 2, the power control capability by the first control method described in Embodiment 2 is described.

In this example, as in the first embodiment, an example in which the number of half cycles per unit is set to 15 in a 60 Hz AC voltage waveform will be described. Set the fluctuation width of the zero-cross point to a time equivalent to ±3 Hz. That is, the cutoff time is set to a time equivalent to ±3 Hz. As described above, the cutoff time in this example is 0.835 msec. Since the manipulated variable MV corresponding to this cutoff time is 0.649%, the minimum set manipulated variable MV of the triac is set to 0.65%. That is, the set manipulated variable MV can be set to 0.65% or more, but cannot be set to less than 0.65%.

In the first control method of this example, as shown in Table 2, as in the first embodiment, the assumed manipulated variable MV can be less than 0.650%. In this example, unlike Example 1, as shown in Table 2, an example in which the assumed manipulated variable MV is changed from 0.650% to 0.043% in units of 0.001% is shown. In the first control method of this example, as shown in Table 2, the assumed electric power can be less than 30.00 W. Table 2 shows an example in which the assumed electric power is changed in increments of 0.05 W or 0.04 W from 30.00 W to 1.98 W. In this example, as shown in Table 2, the set manipulated variables are set to two different set manipulated variables, the first set manipulated variable MV1 and the second set manipulated variable MV2. The number of outputs of MV1 is the number of times that output of a current corresponding to the first set manipulated variable MV1 is permitted by the cyclic control system among the 15 half-cycle currents that have passed through the triac. The number of outputs of MV2 is the number of times that output of a current corresponding to the second set manipulated variable MV2 is permitted by the cyclic control system among the 15 half-cycle currents that have passed through the triac. The number of times of no output is the number of times the current output is rejected by the cyclic control method among the 15 half-cycle currents that have passed through the triac. For example, if the number of outputs of MV1 is 11 times, the number of outputs of MV2 is 2 times, and the number of times of no output is 2 times, it means that among the currents of 15 half cycles that have passed through the triac, the output of the current corresponding to the first set manipulated variable MV1 of 11 half cycles is permitted, the output of the current corresponding to the second set manipulated variable MV2 of two half cycles is permitted, and the output of the current of two half cycles is not permitted.

For example, as shown in the second row from the top of Table 2, when the first set manipulated variable MV1 is 0.75% and the second set manipulated variable MV2 is 0.74%, the number of outputs of MV1 is 11 times, the number of outputs of MV2 is 2 times, and the number of non-outputs is 2 times, the assumed manipulated variable MV is 0.649% (= (0.75 × 11 + 0.74 × 2) / 15) can be done with The assumed electric power when the assumed manipulated variable MV is 0.649% is 29.95 W (= 30.00 × (0.649/0.650)). In this way, it is possible to output desired electric power with high resolution by combining the first set manipulated variable MV1 and the second set manipulated variable MV2 by the phase control method and output control by the cyclic control method.

Thus, according to the first control method of Embodiment 2, the above-described malfunction does not occur, and compared to Embodiment 1, the resolution of the assumed manipulated variable MV can be increased by one digit, and low power can be controlled.

This invention is not limited to these examples, It is shown by the claim, and it is intended that the meaning of a claim and equality and all the changes within the range are included. For example, the first control method may be a control method in which a cyclic control method is combined with an antiphase control method. The anti-phase control method controls the timing at which a trigger signal is input to the switching device so as to cut off the current passing through the switching device every half cycle of the AC voltage waveform. The cyclic control method is a method of controlling the output availability of the current for each half cycle that has passed through the switching element.

1: Heater control unit
10: gas, 10a: first surface, 10b: second surface
10i: inner region, 10m: middle region, 10e: outer region
20: support, 21: flange
30: heating element, 31: first heating element, 32: second heating element
30t: terminal, 30c: power line
40: temperature sensor
50: current sensor, 51: first current sensor, 52: second current sensor
60: controller
61: first temperature controller, 62: second temperature controller, 63: power controller
631: first power controller, 632: second power controller
64: detector, 65: calculator, 66: memory
70: external output device
80: trans, 81: first trans, 82: second trans
W: heating object
tw : time width, t _MV , t _MV1 , t _MV2 : time, θ : operation phase angle

Claims (8)

In the heater control device,
gas and
A heating element disposed in the body;
A power controller controlling AC power supplied to the heating element
including,
The power controller controls the AC power by a first control method in which a phase control method and a cyclic control method are combined;
The phase control method passes a current through the switching element in a passage time between a time when a trigger signal is input to the switching element and a zero cross point of the AC voltage waveform for each half cycle of the AC voltage waveform,
The cyclic control method controls the output availability of the current passing through the switching element for each half cycle of the AC voltage waveform,
The heater control device, wherein the passage time is equal to or longer than a cutoff time previously set in response to a fluctuation range of the zero cross point detected by the power controller. According to claim 1,
The cyclic control method outputs current at an output ratio of M times among the number of half cycles of N times,
The heater control device according to claim 1 , wherein the alternating current power supplied to the heating element is power determined by the passage time in the phase control method and the output ratio. According to claim 1 or 2,
The heater control device, wherein the power controller performs the first control method when supplying power to the heating element corresponding to a time shorter than the cutoff time. According to any one of claims 1 to 3,
The time width of the trigger signal is shorter than the passing time, the heater control device. According to any one of claims 1 to 4,
The heater control device, wherein the passage time has a plurality of passage times having different lengths of time. According to any one of claims 1 to 5,
The body has a disk-shaped shape,
The heating element,
A first heating element disposed in a region including the center of the gas;
At least one second heating element disposed concentrically with the first heating element
have
The power controller has a first power controller for controlling a first power supplied to the first heating element;
The heater control device, wherein the first power controller controls the first power by the first control method. According to claim 6,
At least one current sensor for measuring the current supplied to the at least one second heating element;
Calculator for obtaining the temperature of the second heating element
including,
The power controller has a second power controller that controls second power supplied to the second heating element;
The second power controller controls the second power by the first control method so as to have a preset ratio with respect to the first power;
The heater control device, wherein the calculator calculates the temperature of the second heating element based on the measured value of the current sensor. A power control method for controlling AC power supplied to a load,
Controlling the AC power by a first control method in which a phase control method and a cyclic control method are combined;
The phase control method passes a current through the switching element in a passage time between a time when a trigger signal is input to the switching element and a zero cross point of the AC voltage waveform for each half cycle of the AC voltage waveform,
The cyclic control method controls the output availability of the current passing through the switching element for each half cycle of the AC voltage waveform,
The power control method of claim 1 , wherein the passing time is greater than or equal to a cutoff time previously set corresponding to the range of variation of the zero cross point.