Power supply and inspection equipment

Abstract

To provide a high efficiency and low noise power source and an inspection device.SOLUTION: A power source that supplies power to a heating mechanism used to heat a measurement target that emits a measurement signal includes an input unit that inputs an input signal obtained by reflecting a control signal in a differentiable periodic waveform with a frequency of 1 kHz or less, and a switching amplification unit that amplifies the signal input from the input unit with a switching circuit and outputs the signal.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a power supply and an inspection device.

Background Art

[0002] In a semiconductor manufacturing process, a large number of electronic devices having a predetermined circuit pattern are formed on a semiconductor wafer (hereinafter simply referred to as a wafer). The electrical characteristics of the formed electronic devices are inspected by an inspection device called a probe in the state of the wafer.

[0003] When inspecting the electrical characteristics of a device, such an inspection device is configured to control the temperature of a wafer chuck that holds the wafer by a refrigerant flow path and a heater in order to reproduce the mounting environment of the electronic device (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a measuring device such as an inspection device, a power supply that supplies power to a heater used for heating a device that emits a measurement signal is required to be highly efficient and have little noise.

[0006] The present disclosure provides a power supply and an inspection device that are highly efficient and have little noise.

Means for Solving the Problems

[0007] A power supply according to one aspect of the present disclosure is a power supply for a heating mechanism used to heat a target to be measured that emits a measurement signal, and comprises an input unit that receives an input signal in which a control signal from a temperature control unit that controls the temperature of the target to be measured is reflected in a differentiable periodic waveform with a frequency of 1 kHz or less, and a switching amplifier unit that amplifies the signal input from the input unit with a switching circuit and outputs it, wherein the switching amplifier unit comprises a digital amplifier and further comprises a series resonant circuit provided downstream of the switching amplifier unit that resonates with the frequency of the input signal Furthermore, the change in the control signal is performed at the point where the voltage of the periodic waveform, which is a voltage waveform, is zero. . [Effects of the Invention]

[0008] According to this disclosure, a highly efficient and low-noise power supply and inspection equipment are provided. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view showing the schematic configuration of an inspection device using the power supply according to this embodiment. [Figure 2] Figure 1 is a front view showing a cross-sectional view of a part of the inspection apparatus. [Figure 3] This is a plan view that schematically shows the configuration of the wafer, which is the substrate to be inspected. [Figure 4] This is a block diagram showing the first example of a power supply. [Figure 5] Block this second example of a power supply. [Figure 6] This block shows the third example of a power supply. [Figure 7] This is a block diagram showing the fourth example of a power supply. [Figure 8] This block contains the fifth example of a power supply. [Figure 9] This block shows the sixth example of a power supply. [Modes for carrying out the invention]

[0010] The embodiments will be described below with reference to the attached drawings.

[0011] <Inspection device> First, an inspection device using a power supply according to an embodiment will be described. FIG. 1 is a perspective view showing a schematic configuration of an inspection device using a power supply according to an embodiment, and FIG. 2 is a front view showing a cross section of a part of the inspection device of FIG. 1.

[0012] As shown in FIGS. 1 and 2, the inspection device 1 inspects the electrical characteristics of each of a plurality of devices formed on a wafer W as a substrate, and includes an inspection unit 2, a loader 3, and a tester 4.

[0013] <00-00081>The inspection unit 2 has a housing 11 with a hollow interior, and the housing 11 has a stage 10 on which a wafer W to be inspected is adsorbed and fixed. Further, the stage 10 is configured to be movable in the horizontal and vertical directions by a moving mechanism (not shown). The stage 10 is preferably one with as small a heat capacity as possible.

[0014] As shown in FIG. 3, the wafer W, which is a substrate to be inspected, has a plurality of devices (Dies) D formed on its surface at predetermined intervals from each other by performing an etching process and a wiring process on a substantially disk-shaped silicon substrate. Electrodes E are formed on the surface of the device D, and the electrodes E are electrically connected to circuit elements inside the device D.

[0015] <0-00087>The stage 10 is provided with a temperature sensor (not shown) for measuring the temperature of the wafer W. Also, when a temperature measurement circuit is incorporated in the device D formed on the wafer W, the temperature of the device D can also be measured by the temperature measurement circuit. <0-00089> Below the stage 10, a heating mechanism (heater) 20 for heating the wafer W via the stage 10 is provided. The heating mechanism (heater) 20 may be provided inside the stage 10. The heating mechanism (heater) 20 is not particularly limited, and various ones such as a resistance heater, a lamp, and an LED can be used. The stage 10 may be provided with a refrigerant flow path (not shown) for flowing a refrigerant such as cooling water therethrough.

[0017] Above the stage 10 in the inspection unit 2, a probe card 12 is arranged so as to face the stage 10. The probe card 12 has a plurality of probes 12a which are contactors. Further, the probe card 12 is connected to the tester 4 via an interface 13. When each probe 12a contacts the electrode of each device D of the wafer W, each probe 12a supplies power to the device D from the tester 4 via the interface 13, or transmits a measurement signal from the device D to the tester 4 via the interface 13.

[0018] The loader 3 has a housing 14, and a FOUP (not shown), which is a transport container in which the wafer W is accommodated, is arranged inside the housing 14. Further, the loader 3 has a transport device (not shown), and the transport device takes out the wafer W accommodated in the FOUP and transports it to the stage 10 of the inspection unit 2. Further, the transport device transports the wafer W on the stage 10 for which the inspection of the electrical characteristics has been completed and accommodates it in the FOUP.

[0019] Inside the housing 14 of the loader 3, a power source 30 for supplying power to the heating mechanism (heater) 20 and a control unit 40 are provided. A control signal is input from the control unit 40 to the power source 30, and the power source 30 supplies power to the heating mechanism (heater) 20 based on the control signal.

[0020] Tester 4 has a test board (not shown) that reproduces a part of the circuit configuration of a motherboard on which an electronic device is mounted. The test board is connected to a tester computer 17 that detects a measurement signal emitted from the device D to be tested, formed on a wafer W, and determines whether the device D is good or bad. Tester 4 can reproduce the circuit configurations of multiple types of motherboards by changing the test board. In order to perform high-precision testing, the measurement signal from the device D is required to have as little noise as possible, especially high-frequency noise.

[0021] The probe card 12, interface 13, and tester 4 constitute the testing mechanism.

[0022] During the inspection of the electrical characteristics of device D, the tester computer 17 transmits data to a test board connected to the electronic device via each probe 12a. The tester computer 17 then determines whether the transmitted data has been processed correctly by the test board based on the electrical signals from the test board. At this time, current can be supplied to the internal circuit elements of each device D by applying a voltage to electrode E.

[0023] The control unit 40 consists of a computer and has a temperature control unit 41. The temperature control unit 41 sends a temperature control signal to the power supply 30 based on the set temperature and a temperature signal from a temperature sensor or temperature measuring circuit.

[0024] In addition to the temperature control unit 41, the control unit 40 has a main control unit which has multiple control function units that control each component of the inspection device 1, and the operation of each component of the inspection device is controlled by the main control unit. The control unit 40 also has an input device, an output device, a display device, and a storage device. The control of each component by the main control unit is executed by a processing recipe, which is a control program stored in a storage medium (hard disk, optical disk, semiconductor memory, etc.) built into the storage device.

[0025] The power supply 30 and the control unit 40 may be provided inside the housing 11 of the inspection unit 2.

[0026] The housing 11 of the inspection unit 2 is provided with a user interface unit 18, which constitutes part of the control unit 40. The user interface unit 18 is for displaying information to the user and for the user to input instructions, and consists of, for example, an input unit such as a touch panel or keyboard and a display unit such as a liquid crystal display.

[0027] <Power supply> Next, we will explain the configuration of the power supply 30. The inspection apparatus 1 of this embodiment inspects (tests) a device (Die) D formed on a wafer W, and therefore it is necessary to control the device during inspection so that the noise in the measurement signal from the device D is minimized. On the other hand, the device D is required to have a high power density, and high-speed, high-precision temperature control is necessary. Conventionally, since the amount of heat generated by the device D was relatively small, a method was used in which a material such as Cu or Al with high thermal conductivity was used as the stage 10, and the stage 10 was made thicker to ensure uniform heating and control the temperature. However, recently the amount of heat generated by the device D has increased, and with this method, the heat capacity of the stage is too large, and the temperature control performance is no longer sufficient. For this reason, this embodiment aims to improve controllability by minimizing the heat capacity of the stage 10 and shortening the control cycle.

[0028] A power supply 30 for the heating mechanism (heater) 20 that can achieve such temperature control could be a linear amplifier without switching, but even the most efficient Class B linear amplifier has an efficiency limit of 75%. On the other hand, nonlinear amplifiers such as switching amplifiers are efficient but have a lot of noise, which may reduce the accuracy of the measurement signal from device D.

[0029] From this perspective, in this embodiment, the power supply 30 has an input section that receives an input signal in which a control signal U(t) is reflected in a differentiable periodic waveform with a frequency of 1 kHz or less, and a switching amplifier section that amplifies the signal input from the input section with a switching circuit and outputs it.

[0030] This configuration allows for a highly efficient and low-noise power supply while maintaining good control characteristics. At this time, changes in the control signal are: A voltage waveform is a periodic waveform The operation is performed at a point where the voltage is zero. The control signal is output as a manipulated variable (%).

[0031] A differentiable periodic waveform is a waveform that can be repeatedly differentiated, such as a sine wave, a cosine wave, or a waveform that combines these. By using such a differentiable periodic waveform and keeping the frequency below 1 kHz, radiated noise can be reduced. According to Ampere's law, rotH = i + (∂D / ∂t) (where H is the magnetic field, i is the conduction current, ∂D / ∂t is the displacement current, and D is the magnetic flux density), and radiated noise increases as ∂D / ∂t increases. To reduce ∂D / ∂t, the waveform and frequency are important, and radiated noise can be reduced by using a differentiable periodic waveform that does not have abrupt current fluctuations and setting the frequency to a relatively low value of 1 kHz or less.

[0032] Furthermore, using a switching amplifier as the amplifier yields higher efficiency than a linear amplifier. In other words, because a switching amplifier functions as a switch that directs current to the load, the power wasted by the output transistor is minimized, resulting in high efficiency. To further increase efficiency, it is important to time-shift the point of maximum voltage and the point of maximum current. That is, the imaginary part of the load impedance as seen from the output transistor side of the switching amplifier becomes zero. Generally, the inductance and capacitance components corresponding to the imaginary part change with frequency, so the frequency must be specified as a single value.

[0033] By placing a series resonant circuit that resonates at the input signal frequency, for example 100Hz, on the downstream side of a switching amplifier, the voltage and current become in phase, and theoretically only the resistance of the resonant circuit remains. Therefore, the total impedance is the sum of the resistance of the resonant circuit and the resistance impedance of the load. In addition, noise other than 100Hz is removed by the series resonant circuit, resulting in a lower-noise signal.

[0034] Furthermore, from the perspective of removing high-frequency noise that may affect the inspection, it is preferable to provide a low-pass filter using inductance and capacitance on the downstream side of the switching amplifier. A low-pass filter has almost no resistance up to its cutoff frequency, and attenuation occurs at frequencies above the cutoff frequency. As a result, harmonic components are reflected and not transmitted to the load. In other words, high-frequency noise can be removed, and a lower-noise signal can be achieved.

[0035] From the perspective of removing noise and improving the inspection accuracy of inspection device 1, a series resonant circuit that can remove not only high-frequency noise but also low-frequency noise is more advantageous. Furthermore, the noise removal effect can be further enhanced by using both a low-pass filter and a series resonant circuit.

[0036] The input section may have a signal source that generates a differentiable periodic waveform signal with a frequency of 1 kHz or less, and a multiplier that multiplies the control signal U(t) from the temperature control unit 41 of the control unit 40 by the signal from the signal source.

[0037] A switching amplifier can be an analog amplifier using PWM (Pulse Width Modulation), or a digital amplifier using ΔΣ conversion (ΔΣ modulation). In the case of an analog amplifier, a low-pass filter is used as a smoothing circuit after the output transistor. This low-pass filter also functions as a noise reduction circuit to remove harmonic noise. In the case of a digital amplifier using ΔΣ conversion, the ΔΣ conversion has a noise shaping function, which can move noise to high frequencies. Therefore, the noise reduction effect can be enhanced by providing a low-pass filter or a series resonant circuit.

[0038] [Example 1 of a power supply] Next, we will describe a first example of the power supply 30. This example describes a case where an analog amplifier is used as the switching amplifier section.

[0039] Figure 4 is a block diagram showing a first example of the power supply 30. In this example, the power supply 30 has an input section 31 and a switching amplifier section 32.

[0040] The input unit 31 includes a signal source 51 that emits a differentiable periodic waveform, such as a sine wave, at a specific frequency of 1 kHz or less, and a multiplier 52 that multiplies the control signal (U(t)) from the control unit 40 by the waveform of the signal source 51. The input unit 31 inputs a periodic waveform with a amplitude corresponding to the manipulated variable to the switching amplifier unit 32. The control signal is output from the control unit 40 as a manipulated variable (%).

[0041] The switching amplifier section 32 is configured as an analog amplifier using PWM, i.e., a PWM amplifier. The switching amplifier section 32 includes a triangular wave generator 53, a comparator 54, a PWM driver 55, output transistors 56a and 56b, and a low-pass filter 57.

[0042] The comparator 54 receives the input signal from the input unit 31 and the triangular wave generated by the triangular wave generator 53. The comparator 54 compares these signals and outputs a "1" or "0" signal depending on their magnitude. This signal is sent to the PWM driver 55, where it is set to the desired duty cycle, and the desired square wave is output via the output transistors 56a and 56b. The square wave is converted back to a differentiable waveform similar to the input waveform, such as a sine wave, by a smoothing circuit, a low-pass filter 57, and supplied to the heating mechanism (heater) 20. The low-pass filter 57 has a coil 57a and a capacitor 57b. Although the output transistors 56a and 56b are depicted as having the same structure for convenience, they actually have different conductivity types. The output transistors 56a and 56b may have the same conductivity type, in which case an inverter is provided on one of them.

[0043] Thus, by using a switching amplifier as the amplifier, efficiency is improved, and by using a differentiable periodic waveform and keeping the frequency below 1 kHz, radiated noise can be reduced.

[0044] [Second example of a power supply] Next, a second example of the power supply 30 will be described.

[0045] Figure 5 is a block diagram showing a second example of the power supply 30. In this example, the only difference from the first example is that a series resonant circuit 33 that resonates with the frequency of the input signal is provided on the downstream side of the switching amplifier section 32. The series resonant circuit 33 consists of a coil 33a and a capacitor 33b connected in series. As described above, by providing the series resonant circuit 33, the voltage and current become in phase, and theoretically only the resistance of the resonant circuit remains. In addition, noise other than the frequency of the input signal is removed.

[0046] [Third example of a power supply] Next, a third example of the power supply 30 will be described.

[0047] Figure 6 is a block view of the third example of power supply 30. In this example, the only difference from the first example is that a switching amplifier section 32a is used, which is configured by adding a feedback network (feedback circuit) 58 and an error amplifier 59 to the switching amplifier section 32 of the first example. In this configuration, the output signal is fed back by the feedback network 58, and the difference with the input signal is amplified by the error amplifier 59 and input to the comparator 54. With this configuration, higher speed can be achieved. A series resonant circuit 33 may also be added to the configuration in Figure 6.

[0048] [Fourth example of a power supply] Next, a fourth example of the power supply 30 will be described.

[0049] Figure 7 is a block diagram of the fourth example of power supply 30. In this example, the power supply 30 has an input section 31, a switching amplifier section 32 similar to that in the first example, and another switching amplifier section 32'. The switching amplifier section 32' has the same structure as the switching amplifier section 32. That is, the switching amplifier section 32' has a triangular wave generator 53', a comparator 54', a PWM driver 55', output transistors 56a', 56b', and a low-pass filter 57' (coil 57a', capacitor 57b'). The input signal from the input section 31 is input directly to one switching amplifier section 32, and to the other switching amplifier section 32' via an inverting amplifier 60. The outputs of the two switching amplifier sections 32 and 32' are then supplied to the heating mechanism (heater) 20. This provides twice the power.

[0050] In the example shown in Figure 7, a series resonant circuit may be provided on the output side, or the two switching amplifier sections may be configured to include a feedback network and an error amplifier.

[0051] Examples 1 through 4 show the use of a PWM amplifier as the analog amplifier, but other amplifiers such as PFM (Pulse Frequency Modulation) may also be used.

[0052] [Fifth example of a power supply] Next, a fifth example of the power supply 30 will be described. This example describes a case where a digital amplifier is used as the switching amplifier section.

[0053] Figure 8 is a block diagram showing a fifth example of the power supply 30. In this example, the power supply 30 includes an input section 31, a switching amplifier section 35, and a low-pass filter 36.

[0054] The input unit 31 is the same as in the first example and includes a signal source 51 that emits a differentiable periodic waveform, such as a sine wave, at a specific frequency of 1 kHz or less, and a multiplier 52 that multiplies the control signal (U(t)) from the control unit 40 by the waveform of the signal source 51, inputting a periodic waveform with a amplitude corresponding to the manipulated amount to the switching amplifier unit 35.

[0055] The switching amplifier section 35 includes a ΔΣ conversion (ΔΣ modulation) circuit 71 and output transistors 72a and 72b. The ΔΣ conversion (ΔΣ modulation) circuit 71 includes a differentiator 81, an integrator 82, a comparator 83, a 1-bit DA converter 84, and a shifter 85.

[0056] The differentiator 81 takes the difference between the input signal and the feedback signal from the 1-bit DA converter 84 via the shifter 85. The integrator 82 integrates the signal from the differentiator 81. The comparator 83 compares the integrated signal with a reference value and outputs a pulse train of "1" or "0" depending on the magnitude. The "1" and "0" signals from the comparator 83 are amplified by output transistors 72a and 72b, corresponding to "1" and "0" respectively, to become a digital signal corresponding to the input signal. At the same time, the signal from the comparator 83 is sent to the 1-bit DA converter 84 as a feedback signal. The 1-bit DA converter 84 generates a voltage equal to either a positive reference voltage or a negative reference voltage depending on the output of the comparator 83. If the output of the comparator 83 is "1", the reference voltage is subtracted from the analog input signal. If the output is "0", the reference voltage is added to the analog input signal. The shifter 85 shifts the phase of the analog signal from the 1-bit DA converter 84.

[0057] Note that, for convenience, output transistors 72a and 72b are depicted as having the same structure as output transistors 56a and 56b in the first example, but in reality they have different conductivity types. Output transistors 72a and 72b may have the same conductivity type, in which case an inverter should be provided on one of them.

[0058] The low-pass filter 36 has a coil 36a and a capacitor 36b, and is located downstream of the switching amplifier section 35 to remove noise from the signal coming from the switching amplifier section 35.

[0059] In this example, by feeding the output signal of the comparator 83 back to the input signal via the 1-bit DA converter 84, modulation is applied such that the quantization error (noise) generated in the comparator 83 is small in the low-frequency range and large in the high-frequency range. In other words, noise shaping can be performed so that there is more noise in the high-frequency range. The noise-shaped signal can then be easily de-noised by the low-pass filter 36, resulting in a lower-noise signal. [Sixth example of a power supply] Next, a sixth example of the power supply 30 will be described.

[0060] Figure 9 is a block diagram showing the sixth example of power supply 30. In this example, the low-pass filter 36 in Figure 8 is replaced with a series resonant circuit 37 that resonates with the frequency of the input signal. The series resonant circuit 37 consists of a coil 37a and a capacitor 37b connected in series. By providing the series resonant circuit 37, noise other than the frequency of the input signal is removed. As a result, not only high-frequency noise but also low-frequency noise is removed, allowing a more accurate signal to be supplied to the heating mechanism (heater) 20.

[0061] In addition, both the low-pass filter 36 and the series resonant circuit 37 may be provided. In this case, it is preferable to provide the series resonant circuit 37 after the low-pass filter 36.

[0062] Examples 5 and 6 show examples using a ΔΣ conversion (ΔΣ modulation) circuit as a digital amplifier, but other amplifiers that implement PWM, PFM, etc. in software may also be used.

[0063] <Inspection process using inspection equipment> Next, an example of the inspection process for wafer W using inspection device 1 will be described. First, the wafer W is removed from the FOUP of loader 3 by a transport device and transported to stage 10, where it is placed.

[0064] In this state, the stage 10 is moved to bring the probe 12a located above the stage 10 into contact with the electrode E of the device D to be inspected on the wafer W, and an inspection signal is input to the probe 12a to start the inspection of the device D formed on the wafer W.

[0065] At this time, the heating mechanism (heater) 20 heats the device (Die) D formed on the wafer W via the stage 10 to a desired temperature. At this time, temperature information from a temperature sensor or a temperature measurement circuit incorporated in the device D is fed back to the temperature control unit 41 of the control unit 40, and a control signal is sent from the temperature control unit 41 to the power supply 30 based on the temperature set value set in the temperature control unit 41 and the fed-back temperature information. From the power supply 30, the desired power is supplied to the heating mechanism (heater) 20 based on the control signal, and the device D formed on the wafer W is controlled to a desired temperature. At this time, temperature control may be performed while a refrigerant is flowed to the stage 10 from a refrigerant flow path (not shown).

[0066] As mentioned above, recent devices generate a large amount of heat, so in this embodiment, the aim is to improve the temperature controllability of device D by minimizing the heat capacity of stage 10 and shortening the control period. To achieve such temperature control with high efficiency and low noise, in this embodiment, as described above, the power supply 30 is used, which has an input section that receives an input signal in which the control signal U(t) is reflected in a differentiable periodic waveform with a frequency of 1 kHz or less, and a switching amplifier section that amplifies the signal input from the input section with a switching circuit and outputs it.

[0067] As described above, the power supply 30 with this configuration uses a differentiable periodic waveform with a frequency of 1 kHz or less, resulting in low radiated noise. Furthermore, since a switching amplifier is used as the amplifier, higher efficiency can be achieved compared to a linear amplifier. Therefore, the adverse effects of noise during inspection are reduced, and inspection costs can be lowered.

[0068] Furthermore, the inspection of electronic devices may be performed on multiple devices simultaneously, or on all electronic devices simultaneously, as is done with simultaneous contact probing used in DRAMs and the like.

[0069] <Other applications> Although embodiments have been described above, the embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The above embodiments may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims.

[0070] For example, in the above embodiment, the power supply described was a power supply used to power a heating mechanism used to heat a device under inspection when inspecting the electrical characteristics of a device formed on a wafer. However, it is not limited to this, and any power supply that powers a heating mechanism used to heat a device under inspection from which a measurement signal is detected may be used, for example, a power supply for a handler. [Explanation of Symbols]

[0071] 1; Inspection device 2; Inspection Department 3; Loader 4; Tester 10; Stage 12; Probe card 12a; probe 13; Interface 20; Heating mechanism (heater) 30;Power supply 31; Input section 32, 32a, 32; Switching amplifier section (analog amplifier) 33,37;Series resonant circuit 35; Switching amplifier section (digital amplifier) 36, 57, 57'; Low-pass filter 40; Control Unit 41; Temperature control unit 51;Signal source 52; Multiplier 53; Triangular wave generator 54, 54', 83; comparator 55,55'; PWM driver 56a, 56b, 56a', 56b', 72a, 72b; Output transistors 58; Feedback Network 59; Error amplifier 60; Inverting amplifier 71; ΔΣ Transform (ΔΣ Modulation) Circuit 81;differentiator 82;integrator 84; 1-bit DA converter 85; Shifter D; Device W; wafer

Claims

1. A power supply that provides power to a heating mechanism used to heat the object to be measured, which emits a measurement signal, An input unit receives an input signal that reflects a control signal from a temperature control unit that controls the temperature of the object to be measured, into a differentiable periodic waveform with a frequency of 1 kHz or less. A switching amplifier section that amplifies the signal input from the input section using a switching circuit and outputs it, It has, The switching amplifier section has a digital amplifier, The switching amplifier section further includes a series resonant circuit that resonates with the frequency of the input signal, The change in the control signal is performed at the point where the voltage of the periodic waveform, which is a voltage waveform, is zero, in the power supply.

2. The power supply according to claim 1, wherein the input unit comprises a signal source that generates a differentiable periodic waveform signal with a frequency of 1 kHz or less, and a multiplier that multiplies the control signal by the signal generated by the signal source.

3. The power supply according to claim 1 or claim 2, wherein the point of maximum voltage and the point of maximum current are shifted in time.

4. The power supply according to any one of claims 1 to 3, wherein the digital amplifier is a digital amplifier using ΔΣ conversion.

5. The power supply according to claim 4, wherein the switching amplifier section comprises a ΔΣ conversion circuit and an output transistor.

6. The power supply according to claim 5, wherein the ΔΣ conversion circuit comprises a differentiator that takes the difference between an input signal and a feedback signal, an integrator that integrates the signal from the differentiator, a comparator that compares the integrated signal with a reference value and outputs a pulse train of "1" or "0" to the output transistor depending on the magnitude, and a 1-bit DA converter that generates a voltage equal to a positive reference voltage or a negative reference voltage according to the output from the comparator and outputs it to the differentiator as a feedback signal.

7. The power supply according to any one of claims 1 to 6, further comprising a low-pass filter provided downstream of the switching amplifier section.

8. A stage on which a wafer with multiple devices formed on it is placed, An inspection mechanism for inspecting a device provided on a wafer on the stage by electrically contacting the device with a probe, A heating mechanism for heating the wafer placed on the aforementioned stage, A power supply for the heating mechanism, A control unit that sends a control signal to the aforementioned power supply, It has, The aforementioned power supply is An input unit receives an input signal that reflects a control signal from a temperature control unit that controls the temperature of the object to be measured, into a differentiable periodic waveform with a frequency of 1 kHz or less. A switching amplifier section that amplifies the signal input from the input section using a switching circuit and outputs it, It has, The switching amplifier section has a digital amplifier, The switching amplifier section further includes a series resonant circuit that resonates with the frequency of the input signal, The inspection device is characterized in that the change in the control signal is performed at the point where the voltage of the periodic waveform, which is a voltage waveform, is zero.

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