JP5133108B2 - Temperature measuring device and temperature measuring method - Google Patents

Description

  The present invention relates to a temperature measuring apparatus and method for measuring the temperature of a flat processing object such as a semiconductor wafer supported by a support.

In the manufacturing process of semiconductor devices, various processes such as film formation, etching, and heat treatment are performed on semiconductor wafers (mainly silicon wafers). The processing speed and processing results (crystallinity of silicon wafers, etc.) Depends greatly on the temperature of the semiconductor wafer in the process. For this reason, in the process of manufacturing semiconductor devices, it is important to measure the temperature of the semiconductor wafer being processed with high accuracy in terms of improving yield and manufacturing efficiency.
In general, in the manufacturing process of a semiconductor device, a semiconductor wafer is supported on a lower surface thereof by a wafer stage having a built-in heater, and various processes are performed on the semiconductor wafer whose temperature is adjusted by the heater.
Here, since a thermal resistance exists between the semiconductor wafer and the wafer stage, the temperature of the wafer stage and the temperature of the semiconductor wafer supported by the wafer stage do not necessarily match. Therefore, it is necessary to directly measure the temperature of the semiconductor wafer being processed.
It is also desirable to measure the temperature of the semiconductor wafer being processed without contacting a hard protrusion such as a thermocouple, in order to reduce the temperature measurement effort and prevent contamination of the semiconductor wafer.
For example, in Patent Document 1, when measuring the temperature of a semiconductor wafer accommodated in a process chamber through a window provided in the upper part of the process chamber in a non-contact manner using a radiation thermometer, measurement before processing the semiconductor wafer is performed. The values indicate that the emissivity is calibrated.
Patent Document 2 discloses a technique for indirectly measuring the temperature of a semiconductor wafer by bringing the diaphragm into close contact with the lower surface of the semiconductor wafer (the surface supported by the wafer stage) and measuring the temperature of the diaphragm. ing.
JP 2003-106902 A JP 2003-214957 A

However, since the infrared emissivity of a substance varies greatly depending on its surface condition (surface roughness, etc.), as shown in Patent Document 1, when the temperature of a semiconductor wafer is measured with a radiation thermometer, The measured value varies depending on the etching state. Furthermore, radiation thermometers are susceptible to radiation and reflections from the surrounding area other than the measurement section. For these reasons, the measurement of semiconductor wafers with a radiation thermometer has had the problem that it is difficult to measure temperature with stability and high accuracy. In particular, since the infrared emissivity of silicon, which is often used as a material for semiconductor wafers, is very low, measuring the temperature of a semiconductor wafer with a radiation thermometer is particularly disadvantageous in terms of accuracy.
Further, as shown in Patent Document 2, when the temperature of a semiconductor wafer is indirectly measured by measuring the temperature of an object brought into contact with the semiconductor wafer, the temperature between the semiconductor wafer and an object to be contacted (such as the diaphragm) is Due to the presence of thermal resistance, it was still difficult to measure temperature with high accuracy.
As another temperature measurement method, it is conceivable to measure the temperature by measuring the reflectance and Raman light of a semiconductor wafer. However, in the former, the change in reflectance with respect to temperature is very small, and in the latter the Raman light intensity is measured. Due to the weakness itself, there is a problem that stable and highly accurate temperature measurement is difficult.
Accordingly, the present invention has been made in view of the above circumstances, and the object of the present invention is to change the temperature of a flat processing object such as a semiconductor wafer subjected to various types of processing to a hard protrusion such as a thermometer. An object of the present invention is to provide a temperature measuring apparatus and method capable of measuring with high accuracy while avoiding contamination caused by contact with an object.

Temperature measurement apparatus according to the present invention in order to achieve the above object, a support base for supporting the plate-shaped semi-conductor weblog Ha In one aspect thereof, measure the temperature of the supported said semiconductor wafer by the support table And includes the components shown in the following (1-1) to (1-3).
(1-1) Ultrasonic wave output means for outputting ultrasonic waves to the semiconductor wafer from the support base side.
(1-2) Ultrasonic detection means for detecting reflected ultrasonic waves reflected on the semiconductor wafer .
(1-3) Temperature calculation means for calculating the temperature of the semiconductor wafer based on the detection signal of the ultrasonic detection means.
As shown in FIG. 7, the velocity of ultrasonic waves propagating in a substance (that is, the speed of sound) is highly correlated with the temperature of the substance. For example, when silicon, which is often used for semiconductor wafers, is an ultrasonic (longitudinal wave) transmission medium, the propagation speed (sound speed) of ultrasonic waves at room temperature is 8433 [m / s] (longitudinal wave). On the other hand, the propagation speed of the ultrasonic wave changes with a temperature coefficient of −0.4 [(m / s) / ° C.] according to the temperature change of silicon. Therefore, the ultrasonic waves irradiated to the semiconductor wafer, if measuring the propagation velocity of ultrasound (sonic speed) in the semiconductor wafer, can be the temperature of the semiconductor wafer corresponding to the speed measured (calculated).
On the other hand, when the semiconductor wafer is irradiated with ultrasonic waves, the ultrasonic waves are reflected on both the ultrasonic irradiation surface and the opposite surface of the semiconductor wafer . And the ultrasonic wave propagation speed (sound speed) in the semiconductor wafer can be calculated with high accuracy based on the known thickness of the semiconductor wafer (the distance between the ultrasonic irradiation surface and the opposite surface). it can.
Therefore, the temperature of the semiconductor wafer can be calculated with high accuracy by executing processing based on the detection signal of the ultrasonic detection means by the temperature calculation means.
In addition, the ultrasonic measurement does not cause contamination of the semiconductor wafer .
Here, the temperature calculation means specifies the resonance frequency of the ultrasonic wave in the semiconductor wafer based on the detection signal of the ultrasonic detection means or detects the propagation time or phase of the ultrasonic wave propagated in the semiconductor wafer . It was carried out, according to the result (i.e., the ultrasonic wave propagation as an indication of the speed of the results in the semiconductor wafer) is conceivable to calculate the temperature of the semiconductor wafer.

As the temperature calculation means in the present invention, for example, the following four examples can be considered.
First, the first example is an example in which the temperature measuring device according to the present invention includes frequency sweeping means for performing frequency sweeping of the ultrasonic wave output from the ultrasonic wave output means.
In this case, the temperature calculation means, said frequency sweep means by the ultrasonic wave intensity of the detection signal of the detection means (amplitude) and the semiconductor wafer on the basis of which changes according to the frequency sweep of the sweep frequency and ultrasonic ultrasound The resonance frequency of the ultrasonic wave inside is specified, and the temperature of the semiconductor wafer is calculated based on the resonance frequency.
Wherein when irradiated with ultrasonic waves in the surface of the semiconductor wafer (the supported surface), ultrasound between within the semiconductor wafer and the ultrasonic wave irradiation surface and its opposite surface is multiple reflection. At that time, if the relationship between the ultrasonic frequency, the propagation speed, and the thickness of the semiconductor wafer satisfies a predetermined resonance condition, a large ultrasonic vibration is generated, and the intensity of the detection signal of the ultrasonic detection means (the reflected ultrasonic wave) Strength) is relatively large. Therefore, if the frequency sweep of the ultrasonic wave applied to the semiconductor wafer is performed, the resonance frequency can be specified from the sweep frequency when the intensity of the reflected ultrasonic wave reaches a peak (when the resonance condition is satisfied), and the resonance frequency is based on, it can calculate the temperature of the semiconductor wafer corresponding to the propagation speed of the ultrasonic wave in the semiconductor wafer (speed of sound).

The second example is an example in which the ultrasonic output means outputs pulsed ultrasonic waves.
In this case, the ultrasonic calculation of the ultrasonic wave reflected by the surface of the semiconductor wafer supported by the support base and the surface opposite thereto based on the detection signal of the ultrasonic detection unit. A difference in arrival time at the means is detected, and the temperature of the semiconductor wafer is calculated based on the detection result.
In general, the propagation speed of ultrasonic waves is known, and the thickness of the measurement object is measured from the time interval between peaks in the detection signal of reflected ultrasonic waves. On the other hand, in the second example, the thickness of the semiconductor wafer is known, and the ultrasonic wave propagation speed (sound speed) in the semiconductor wafer is based on the time interval between peaks in the reflected ultrasonic detection signal. The temperature corresponding to is calculated.
The third example is an example in which the ultrasonic output means outputs pulsed ultrasonic waves.
In this case, the temperature calculation means identifies the resonance frequency of the ultrasonic wave in the semiconductor wafer based on the change in the detection signal of the ultrasonic detection means, and determines the temperature of the semiconductor wafer based on the resonance frequency. calculate.
As described above, since the ultrasonic waves are multiple-reflected in the semiconductor wafer , the resonance frequency component appears in the change in the detection signal of the ultrasonic detection means even if the resonance condition is not satisfied. Therefore, by performing waveform analysis of the detection signal of the ultrasonic detection means to identify the resonance frequency, based on the known thickness of the resonant frequency and the semiconductor wafer, the propagation velocity of the ultrasonic wave in the semiconductor wafer ( The temperature of the semiconductor wafer corresponding to the speed of sound) can be calculated.

The fourth example is an example in which the ultrasonic output means outputs a plurality of pulsed ultrasonic waves at a predetermined period, that is, a so-called burst wave-like state in which the ultrasonic wave is intermittent (with a constant frequency) at a predetermined period. It is an example which outputs an ultrasonic wave.
In this case, the temperature calculation means detects the phase of the reflected ultrasonic wave reciprocally reflected between the surface of the semiconductor wafer supported by the support base and the opposite surface thereof from the detection signal of the ultrasonic detection means. Then, the temperature of the semiconductor wafer is calculated based on the phase. For example, the temperature calculation means detects the phase of the ultrasonic waves reflected back and forth by mixing the detection signal of the ultrasonic detection means and the reference oscillation signal generated by the ultrasonic output means and oscillating at the ultrasonic frequency. To do.
As described above, the ultrasonic velocity propagating within the semiconductor wafer (speed of sound), the there are temperature and high correlation of the semiconductor wafer, and the ultrasonic phase propagated through the inside of the semiconductor wafer, the It depends on the propagation time (time required for propagation).
Therefore, in the fourth example, the thickness of the semiconductor wafer is known, and the temperature corresponding to the ultrasonic wave propagation speed (sound speed) in the semiconductor wafer is determined based on the phase of the detection signal of the reflected ultrasonic wave. calculate.
At that time, the temperature calculation means extracts a signal in a predetermined time zone synchronized with the output period of the burst wave-like ultrasonic wave output from the ultrasonic wave output means from the detection signal of the ultrasonic wave detection means, and the extraction It is conceivable to detect the phase of the ultrasonic wave reflected back and forth a plurality of times between the opposing surfaces by mixing the signal and the reference oscillation signal.
Since the phase of the ultrasonic wave propagating inside the semiconductor wafer changes greatly as the propagation time becomes longer, the phase of the ultrasonic wave reflected and reciprocated a plurality of times (that is, having a long propagation time) between the opposing surfaces is detected. By doing so, temperature calculation (temperature detection) with high sensitivity becomes possible.

Further, the ultrasonic output means has a plurality of ultrasonic transducers provided for each of a plurality of measurement positions on the support base and one AC signal supply unit for supplying an AC signal to the ultrasonic transducers. The ultrasonic detection means includes a plurality of ultrasonic transducers provided for each of the plurality of measurement positions, and one signal input unit to which detection signals of the reflected ultrasonic waves output from the ultrasonic transducers are input. It is conceivable that the temperature measuring device according to the present invention further includes the constituent elements shown in the following (1-4).
(1-4) Signal paths between the plurality of ultrasonic transducers and the AC signal supply unit in the ultrasonic output unit, and the plurality of ultrasonic transducers and the signal input unit in the ultrasonic detection unit Signal path switching means for sequentially switching the signal path between and.
In this case, each of the plurality of measurement positions on the semiconductor wafer is based on a detection signal of the reflected ultrasonic wave obtained through the signal input unit every time the signal path is switched by the signal path switching unit. The temperature at the position corresponding to is calculated.
Thereby, the temperature distribution of a plurality of locations of the semiconductor wafer can be measured with relatively few components.
In order to efficiently propagate the ultrasonic wave, it is preferable to provide an ultrasonic wave guide formed between the ultrasonic wave output means and the semiconductor wafer in the support base.

The present invention can also be understood as a temperature measuring method for measuring the temperature of the semiconductor wafer using the temperature measuring apparatus according to the present invention described above.
That is, the temperature measuring method according to the present invention is a method for measuring the temperature of the semiconductor wafer in a state where a predetermined semiconductor wafer is supported by a support on one surface thereof. It has each process shown in (2-3).
(2-1) An ultrasonic output step of outputting ultrasonic waves to the semiconductor wafer from the support base side by an ultrasonic output means.
(2-2) An ultrasonic detection step of detecting reflected ultrasonic waves reflected on the semiconductor wafer by the ultrasonic detection means.
(2-3) A temperature calculation step of calculating the temperature of the semiconductor wafer based on the detection signal in the ultrasonic detection step by the calculation means.
The temperature measuring method according to the present invention also exhibits the same operational effects as the above-described temperature measuring device according to the present invention.

According to the present invention, the temperature of the semiconductor weblog Ha various processes are performed, while avoiding contamination by contact, can be measured easily in a stable and high precision.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
1 is a schematic configuration diagram of the semiconductor wafer temperature measuring device X1 according to the first embodiment of the present invention, FIG. 2 is a flowchart showing a temperature measuring procedure by the semiconductor wafer temperature measuring device X1, and FIG. 3 is a semiconductor wafer temperature measuring device. The figure showing the relationship between the ultrasonic frequency obtained by apparatus X1, and reflected ultrasonic intensity, FIG. 4 is a schematic block diagram of semiconductor wafer temperature measuring apparatus X2 which concerns on 2nd Embodiment of this invention, FIG. 5 is semiconductor wafer temperature measurement FIG. 6 schematically shows a change in the reflected ultrasonic detection signal obtained by the apparatus X2, and FIG. 6 shows a change in the reflected ultrasonic detection signal obtained by the semiconductor wafer temperature measuring apparatus X3 according to the third embodiment of the present invention. FIG. 7 is a diagram showing the relationship between the temperature of the substance and the longitudinal wave propagation velocity in the substance, and FIG. 8 is a schematic configuration diagram of the semiconductor wafer temperature measuring apparatus X4 according to the fourth embodiment of the present invention. Figure 9 is a diagram schematically showing a change in the reflected ultrasonic wave detection signal obtained by the semiconductor wafer temperature measuring device X4.

[First Embodiment]
First, the configuration of the semiconductor wafer temperature measuring device X1 (hereinafter referred to as the temperature measuring device X1) according to the first embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, the temperature measuring device X1 includes a wafer stage 2, an oscillator 3, a selector 4, an amplifier 5, a control / arithmetic unit 6, and an environmental temperature sensor 7.
The wafer stage 2 is accommodated in a process chamber 8, and a semiconductor wafer 1 (hereinafter referred to as a wafer), which is a flat processing object to be subjected to various processes such as a film forming process, an etching process, and a heat treatment. It is a support stand supported on the lower surface. The material constituting the wafer stage 2 is, for example, Teflon (registered trademark of DuPont) or ceramic.
The wafer stage 2 has a plurality of suction holes (not shown) at a plurality of locations. The suction hole forms a passage for air drawn in by a compressor (not shown), and the wafer 1 placed on the wafer stage 2 is attracted to the support surface of the wafer stage 2 by the suction force of the compressor. To be fixed.
Further, the wafer stage 2 incorporates a heater (not shown), and the wafer 1 on the wafer stage 2 is heated to a desired temperature by the heater.
The wafer stage 2 includes a temperature sensor for detecting its own temperature, a vertical mechanism for holding the wafer 1 up and down, a voltage application mechanism for the wafer 1, and the like (all not shown). The description is omitted.
The temperature measuring device X is a device that measures the temperature of the wafer 1 supported by the wafer stage 2 using ultrasonic waves.

Furthermore, the wafer stage 2 is provided with ultrasonic transmission / reception units 10 at a plurality of locations.
The ultrasonic transmission / reception unit 10 includes a transmission ultrasonic transducer 11, a reception ultrasonic transducer 12, and a waveguide 13.
The waveguide 13 is formed between the ultrasonic transmission / reception unit 10 and the wafer 1 in the wafer stage 2 and is a transmission path for the ultrasonic wave applied to the wafer 1 and its reflected wave (reflected ultrasonic wave). The hole formed in the support surface of the wafer stage 2 (the surface that supports the wafer 1) is filled with an elastic member such as silicon rubber. As the material of the elastic member, it is desirable to adopt a material that has a small propagation loss of ultrasonic waves and does not contaminate the wafer 1 even if it contacts the wafer 1. Further, as shown in an enlarged cross-sectional view (within a broken line frame) of the ultrasonic transmitting / receiving unit 10 in FIG. 1, when the wafer 1 is supported on the support surface of the wafer stage 2, The elastic member is filled in a hole provided in the support surface so that the wafer 1 protrudes slightly from the support surface of the stage 2 so that a gap is not generated between the waveguide 13 and the waveguide 13 as much as possible. Yes. This reduces the propagation loss of the ultrasonic wave.

The transmitting ultrasonic transducer 11 is provided for each of the waveguides 13 formed at a plurality of locations on the wafer stage 2, and an AC signal is supplied from the oscillator 3 (an example of the AC signal supply unit). , And outputs (irradiates) ultrasonic waves to the wafer 1 from the supported surface side through the waveguide 13. The oscillator 3 and the transmission ultrasonic transducer 11 are examples of the ultrasonic output means.
The reception ultrasonic transducer 12 is provided for each of the plurality of waveguides 13, detects reflected ultrasonic waves reflected on the wafer 1 and returning through the waveguides 13, and detects the detection signal (intensity of the reflected ultrasonic waves). (Electrical signal representing). The detection signal is input to the amplifier 5 (an example of the signal input unit), amplified by the amplifier 5, and then transmitted to the control / arithmetic unit 6. The reception ultrasonic transducer 12 and the amplifier 5 are examples of the ultrasonic detection means.

One oscillator 3 is provided for the plurality of transmission ultrasonic transducers 11 and supplies an AC signal to the transmission ultrasonic transducers 11. The oscillator 3 in the temperature measuring device X1 has a function of adjusting (changing) the frequency of the AC signal in accordance with a command from the control / arithmetic device 6, and output from the transmitting ultrasonic transducer 11 by adjusting the frequency. The frequency sweep of the ultrasonic wave to be performed can be executed (an example of the frequency sweep means). Of course, the oscillator 3 can also fix the frequency of the ultrasonic wave output from the ultrasonic transducer for transmission 11 to a specific frequency by fixing the frequency of the AC signal.
The selector 4 sequentially switches a plurality of signal paths between the transmission ultrasonic transducers 11 and the oscillator 3 and a plurality of signal paths between the reception ultrasonic transducers 12 and the amplifier 5. It is a signal switching device (an example of the signal path switching means).
The environmental temperature sensor 7 is a sensor (thermistor, thermocouple, etc.) for detecting the ambient temperature in the process chamber 8, that is, the temperature of the installation environment of the wafer 1, and the detected temperature is taken into the control / arithmetic unit 6. It is.
The control / arithmetic unit 6 includes a processor (arithmetic means) for executing a predetermined program stored in the storage unit in advance, and the processor controls the oscillator 3 and the reflected ultrasonic wave obtained through the amplifier 5 by the processor. The thickness calculation process and temperature calculation process of the wafer 1 based on the detection signal are executed.

Next, a procedure for measuring the temperature of the wafer 1 by the temperature measuring device X1 will be described with reference to the flowchart shown in FIG. Hereinafter, S1, S2,... Represent identification codes of processing procedures (steps). In addition, the process of S1-S10 shown below is performed in the state by which the wafer 1 which is a process target object was supported by the wafer stage 2 in the one surface (lower surface).
First, the control / calculation device 6 selects any one of the plurality of ultrasonic transmission / reception units 10, and the transmission ultrasonic transducer 11 and the oscillator 3 in the ultrasonic transmission / reception unit 10 The selector 4 is set (controlled) so that the signal path between the receiving ultrasonic transducer 12 and the amplifier 5 in the same ultrasonic transmission / reception unit 10 is connected. S1).
Further, the control / arithmetic unit 6 acquires the detected temperature (environment temperature) of the environment temperature sensor 7 (S2).
Next, the control / arithmetic unit 6 outputs an ultrasonic output command to the oscillator 3. As a result, the oscillator 3 and the transmitting ultrasonic transducer 11 output ultrasonic waves while performing frequency sweep on the supported surface (the lower surface in FIG. 1) of the wafer 1 (S3). In parallel with this, the control / calculation device 6 detects the ultrasonic sweep frequency and the reflected ultrasonic detection signal (the detection signal of the reception ultrasonic transducer 12) that changes according to the ultrasonic frequency sweep. ) Are recorded in a predetermined storage means in association with each other (S3). The range of the ultrasonic sweep frequency is, for example, about 11.2 [MHz] to 11.3 [MHz].
In the temperature measuring device X1, the control / arithmetic unit 6 does not need to acquire and record the reflected ultrasonic detection signal with a resolution that can grasp the waveform of the reflected ultrasonic detection signal. It is sufficient to be able to detect and record I _US (amplitude, rms, etc.).

Next, the control / arithmetic unit 6 detects the ultrasonic sweep frequency recorded in step S3 and the reflected ultrasonic intensity I _US (detection signal of the reception ultrasonic transducer 12) that changes according to the frequency sweep. Is determined based on the resonance frequency fr and the ambient temperature Ta acquired in step S2, and the ultrasonic frequency selected at that time is determined based on the resonance frequency fr. The thickness L of the wafer 1 at the position corresponding to the acoustic wave transmitting / receiving unit 10 is calculated and the calculation result is recorded in a predetermined storage means (S4, an example of the automatic thickness setting means). The process of step S4 is a process of automatically setting the thickness of the wafer 1 used in a temperature calculation process (S8) described later. Details of the process in step S4 will be described later.
Then, the control / arithmetic unit 6 discriminates the switching results of the selector 4 until the thickness measurement of the wafer 1 corresponding to all the ultrasonic transmitting / receiving units 10 at a plurality of locations is completed (S5). These processes are executed sequentially.
Through the processes in steps S1 to S5 described above, the thickness of the wafer 1 used in the temperature calculation process (S8) described later is set in advance (temperature measurement) for all measurement sites corresponding to the plurality of ultrasonic transmission / reception units 10. Set before).

When the control / calculation device 6 detects that a predetermined temperature measurement start condition is satisfied (S6), the control / calculation device 6 performs various processes such as a film forming process, an etching process, and a heat treatment in the process chamber 8. The temperature measurement process (steps S7 to S10) of the wafer 1 when being performed is executed.
In the temperature measurement process, first, the control / arithmetic unit 6 performs the transmission ultrasonic transducer 11 and the oscillator 3 for any one of the plurality of ultrasonic transmission / reception units 10 as in step S1. And a signal path between the receiving ultrasonic transducer 12 and the amplifier 5 (S7).
Further, the control / arithmetic unit 6 outputs an ultrasonic output command to the oscillator 3 in the same manner as in step S3, so that an ultrasonic output process (by the oscillator 3 and the transmitting ultrasonic transducer 11) ( A process of outputting an ultrasonic wave while performing frequency sweep on the supported surface of the wafer 1 is executed (S8). In parallel with this, the control / arithmetic unit 6 detects the ultrasonic sweep frequency and the reflected ultrasonic detection signal (detection of the reception ultrasonic transducer 12) that changes in accordance with the ultrasonic frequency sweep. Signal) and the time at that time are correlated and recorded in a predetermined storage means (S8). In the temperature measurement apparatus X1, it is not necessary to acquire and record the reflected ultrasonic detection signal with a resolution that can grasp the waveform, and the intensity I _US (amplitude, effective value) of the reflected ultrasonic detection signal. Etc.) can be detected and recorded.

Next, the control / arithmetic unit 6 detects the ultrasonic sweep frequency recorded in step S8 and the intensity I _US of the reflected ultrasonic wave that changes according to the frequency sweep (the detection signal of the reception ultrasonic transducer 12). The resonance frequency fr of the ultrasonic wave in the wafer 1 is specified based on the intensity of the wafer 1 and the temperature of the wafer 1 is calculated based on the resonance frequency fr and the thickness d of the wafer 1 recorded in step S4. At the same time, the calculation result is recorded in a predetermined storage means (S9, an example of the temperature calculation means). Details of the process in step S8 will be described later.
Then, the control / arithmetic unit 6 sequentially executes the processes of steps S7 to S10 while determining the end condition (S10) until a predetermined temperature measurement end condition is satisfied.
In this manner, the control / arithmetic unit 6 performs a plurality of the waveguides 13 on the wafer 1 on the basis of the reflected ultrasonic detection signal obtained through the amplifier 5 each time the signal path is switched by the selector 4. The temperature of the position corresponding to each is calculated. Through the processes in steps S7 to S10 described above, the measured values of the temperature change of the wafer 1 being processed are recorded in the storage unit for all the measurement sites corresponding to the plurality of ultrasonic transmitting / receiving units 10.

Next, details of the temperature calculation process (S9) in the temperature measuring device X1 will be described.
As shown in FIG. 7, the speed of sound in a silicon single crystal that is often employed as a material for a semiconductor wafer has temperature dependence. The temperature coefficient is about −0.4 [(m / s) / ° C.] in the case of a silicon single crystal.
On the other hand, when the ultrasonic wave is irradiated to the wafer 1 from the thickness direction, the ultrasonic wave is subjected to multiple reflections between the ultrasonic wave irradiation surface of the wafer 1 and the opposite surface. Assuming that the wavelength of the ultrasonic wave is λ and the thickness of the wafer 1 is L, a large ultrasonic vibration is generated in the wafer 1 when the resonance condition expressed by the following equation (a1) is satisfied. The intensity of the sound wave detection signal becomes relatively large.
λ = 2L / n (where n = 1, 2,...) (a1)
If the resonance frequency when the resonance condition is satisfied is fr, the sound velocity (ultrasonic propagation velocity) Vt in the wafer 1 is expressed by the following equation (a2).
Vt = fr. (2L) / n (where n = 1, 2,...) (A2)
Note that “n” is a numerical value that can be assumed in advance from the range of the material and approximate thickness of the wafer 1 and the ultrasonic sweep frequency.

FIG. 3 is a graph showing the relationship between the frequency of the ultrasonic waves (horizontal axis) and the intensity of the reflected ultrasonic waves (vertical axis). As shown in FIG. 3, if the frequency sweep of the ultrasonic wave applied to the wafer 1 is performed, the peak is obtained at the sweep frequency at which the intensity of the reflected ultrasonic wave is changed. Therefore, if the frequency sweep of the ultrasonic wave applied to the wafer 1 is performed and the sweep frequency fp when the intensity of the reflected ultrasonic wave reaches a peak (when the resonance condition is satisfied) is specified, the frequency fp is the resonance of the wafer 1. It can be said that the frequency fr.
In step S9, the controller / arithmetic unit 6 first specifies the sweep frequency fp when the intensity of the reflected ultrasonic wave reaches a peak when the frequency of the ultrasonic wave applied to the wafer 1 is swept. The resonance frequency fr is specified. Further, the control / arithmetic unit 6 adds the resonance frequency fr to the equation obtained by applying the equation (a2) to the equation representing the relationship between the sound speed Vt and the temperature Tx shown in FIG. And the temperature Tx of the wafer 1 is calculated by applying the thickness L of the wafer 1.
Here, assuming that the thickness L of the wafer 1 is 0.8 [mm] and the temperature coefficient is −0.4 [(m / s) / ° C.], the resolution of 2 [° C.] is obtained for the measurement temperature of the wafer 1. In order to obtain it, it is necessary to measure the speed of sound in the wafer 1 with an accuracy of 1 [m / s] or less.
Further, from the equation (a2), in order to measure the speed of sound in the wafer 1 with an accuracy of 1 [m / s] or less, it is necessary to set the resolution (step size) of the sweep frequency to 1 [kHz] or less. .
On the other hand, it is sufficiently possible to set the step size (resolution) of the sweep frequency in step S8 to about 1 [kHz]. Therefore, the temperature measuring device X1 can measure the temperature of the wafer 1 with high accuracy with a temperature resolution of 2 [° C.] or less. In addition, since it is a non-contact measurement using ultrasonic waves, temperature measurement can be performed very easily, and the wafer 1 is not contaminated, and is also affected by the surface condition (surface roughness, etc.) of the wafer 1. Measurement stability is high due to difficulty.

By the way, before the temperature measurement, the temperature of the wafer 1 is the ambient temperature sensor 7 in a normal temperature state where the wafer 1 is not heated or in a state where the entire process chamber 8 containing the wafer 1 is maintained at a predetermined temperature. It can be regarded as being equal to the detected temperature (environment temperature).
Therefore, in step S4 before measuring the temperature of the wafer 1, the control / arithmetic unit 6 reverses the relationship between the known and unknown thickness L (known) and temperature Tx (unknown) of the wafer 1 in the temperature calculation process described above. By performing the calculation, the thickness L of the wafer 1 is calculated and automatically set based on the detection signal of the reflected ultrasonic wave under the known ambient temperature and the known ambient temperature.
When the wafer 1 is heat-treated, the thickness L of the wafer 1 being heated changes with respect to the thickness measured before heating due to thermal expansion. For example, the thermal expansion coefficient of silicon is 10 ⁻⁶ . Therefore, the effect can usually be ignored. It is also conceivable to correct the thickness L of the wafer 1 used for calculating the temperature of the wafer 1 (S9) in consideration of the thermal expansion of the wafer 1.

[Second Embodiment]
Next, a semiconductor wafer temperature measuring device X2 (hereinafter referred to as a temperature measuring device X2) according to a second embodiment of the present invention will be described with reference to FIG.
Since the temperature measuring device X2 is an application example of the temperature measuring device X1, only portions different from the temperature measuring device X1 will be described below. In FIG. 4, the same components as those of the temperature measuring device X1 are denoted by the same reference numerals.
As shown in FIG. 4, the temperature measuring device X2 includes a wafer stage 2, a selector 4 ′, an ultrasonic signal processing device 9, a control / arithmetic device 6 ′, and an environmental temperature sensor 7.
Further, the wafer stage 2 is provided with ultrasonic transmission / reception units 10 'at a plurality of locations.
The ultrasonic transmission / reception unit 10 ′ includes an ultrasonic transducer 11 ′ and a waveguide 13. The ultrasonic transducer 11 ′ in the ultrasonic transmission / reception unit 10 ′ serves both as the transmitting ultrasonic transducer 11 and the receiving ultrasonic transducer 12 in the temperature measuring device X 1. Is.
The ultrasonic signal processing device 9 has both functions of the oscillator 3 and the amplifier 5 in the temperature measuring device X1, but does not need to have a frequency sweep function, and the ultrasonic transducer 11 ′. By supplying a pulsed alternating current signal, a pulsed ultrasonic wave is output through the ultrasonic transducer 11 ′. The pulse width of the ultrasonic waves output from the ultrasonic signal processing device 9 and the ultrasonic transducer 11 ′ is, for example, about 30 [ns].
Further, the ultrasonic signal processing device 9 detects reflected ultrasonic waves reflected on the wafer 1 supported by the wafer stage 2 and returning through the waveguide 13 through the ultrasonic transducer 11 ′, and outputs the detection signal. To do. As described above, the ultrasonic transducer 11 ′ outputs pulsed ultrasonic waves and detects the reflected waves, thereby performing ultrasonic output and detection in a time-sharing manner. Note that the ultrasonic signal processing device 9 and the ultrasonic transducer 11 ′ are examples of both the ultrasonic output means and the ultrasonic detection means.
The control / arithmetic unit 6 ′ includes a processor (arithmetic unit) for executing a predetermined program stored in the storage unit in advance, like the control / arithmetic unit 6 in the temperature measuring device X1. The processor performs control of the ultrasonic signal processing device 9 and processing for calculating the thickness of the wafer 1 and temperature calculation processing based on the detection signal of the reflected ultrasonic wave obtained through the ultrasonic signal processing device 9.

Next, a procedure for measuring the temperature of the wafer 1 using the temperature measuring device X2 will be described.
In the temperature measuring device X2, the control / arithmetic device 6 ′ performs temperature measurement in the same procedure as shown in the flowchart of FIG.
However, in the temperature measurement device X2, the control / calculation device 6 ′ performs the ultrasonic output control and reflected ultrasonic detection processing executed in steps S3 and S8, and the wafer 1 executed in steps S4 and S9. The contents of the thickness calculation and the temperature calculation are different from the contents executed in the temperature measuring device X1. This will be described below.
In steps S 3 and S 8, the control / calculation device 6 ′ outputs a pulse ultrasonic output command to the ultrasonic signal processing device 9. As a result, the ultrasonic signal processing device 9 outputs pulsed ultrasonic waves to the supported surface of the wafer 1 (the lower surface in FIG. 1). In parallel with this, the control / calculation device 6 ′ records the data of the reflected ultrasonic detection signal (the detection signal of the reception ultrasonic transducer 12) in a predetermined storage means. In the temperature measuring device X2, the control / calculation device 6 ′ acquires and records the reflected ultrasonic wave detection signal with a resolution that can grasp the waveform.
In step S9, the control / arithmetic unit 6 ′ first starts the ultrasonic wave reflected on the supported surface and the opposite surface of the wafer 1 based on the reflected ultrasonic detection signal recorded in step S8. A difference in arrival time at each of the ultrasonic transducers 11 ′ is detected.

FIG. 5 is a diagram schematically showing a change in the detection signal of the reflected ultrasonic wave when the wafer 1 is irradiated with pulsed ultrasonic waves.
When the wafer 1 is irradiated with ultrasonic waves from a direction substantially perpendicular to the supported surface, a part of the ultrasonic waves is reflected on the supported surface of the wafer 1 and the remaining part enters the wafer 1. Multiple reflection is performed between the surface opposite to the supported surface (the upper surface in FIG. 4) and the supported surface. Therefore, as shown in FIG. 5, the ultrasonic signal processing device 9 causes the supported surface of the wafer 1 to pass after a time corresponding to the distance between the ultrasonic transducer 11 ′ and the supported surface of the wafer 1. The reflected ultrasonic signal (echo signal) reflected at 1 is detected, and each time a time corresponding to the thickness L of the wafer 1 (the time during which the ultrasonic wave travels a distance of 2L) elapses, the supported surface of the wafer 1 The reflected ultrasonic signal reflected on the surface opposite to the surface is detected.
In step S9, the control / arithmetic unit 6 ′ detects the time interval between the peaks of the detection signals of the reflected ultrasonic waves recorded in step S8, so that the supported surface of the wafer 1 and the opposite surface thereof are detected. An echo time difference tpp which is a difference in arrival time of each reflected ultrasonic wave to the ultrasonic transducer 11 ′ is detected.
Here, the ultrasonic wave propagation velocity (longitudinal wave velocity) Vt in the wafer 1 is expressed by the following equation (b1) based on the thickness L of the wafer 1 and the echo time difference tpp.
Vt = 2L / tpp (b1)
Accordingly, in step S9, the control / calculation device 6 ′ obtains an expression obtained by applying the expression (b1) to the expression (known relational expression) representing the relationship between the sound speed Vt and the temperature Tx shown in FIG. The temperature Tx of the wafer 1 is calculated by applying the echo time difference tpp detected based on the reflected ultrasonic detection signal and the thickness L of the wafer 1 calculated in step S4.

When the thickness L of the wafer 1 is 0.8 [mm] and the temperature coefficient is −0.4 [(m / s) / ° C.], a resolution of 2 [° C.] is obtained for the measurement temperature of the wafer 1. Therefore, it is necessary to measure the speed of sound in the wafer 1 with an accuracy of 1 [m / s] or less.
Further, from the equation (b1), in order to measure the sound speed in the wafer 1 with an accuracy of 1 [m / s] or less, it is necessary to measure the echo time difference tpp with a resolution of 20 [ps] or less. The time resolution (sampling period) of a general signal waveform observer is about several hundreds [ps]. However, by applying waveform analysis processing such as delayed correlation processing to the detection signal of reflected ultrasonic waves, 20 [ The echo time difference tpp can be measured with a resolution of [ps] or less.
Here, when pulsed ultrasonic waves are output, if the thickness of the wafer 1 is about 0.8 [mm], the echo time difference tpp is 200 [ns] or less, so the pulse width of the ultrasonic waves is set to 0. .1 [μs] or less is required.

Further, as described above, in the normal temperature state before the temperature measurement or the state in which the entire process chamber 8 is maintained at a predetermined temperature, the temperature of the wafer 1 is the detected temperature (environment temperature) of the environmental temperature sensor 7. Can be considered equal.
Therefore, in step S4 before measuring the temperature of the wafer 1, the control / arithmetic unit 6 ′ determines the relationship between the known and unknown thickness L (known) and temperature Tx (unknown) of the wafer 1 in the temperature calculation process described above. By performing the reverse calculation, the thickness L of the wafer 1 is calculated and automatically set based on the detection signal of the reflected ultrasonic wave under the known ambient temperature and the known ambient temperature.

[Third Embodiment]
Next, a semiconductor wafer temperature measuring device X3 (hereinafter referred to as a temperature measuring device X3) according to a third embodiment of the present invention will be described.
The device configuration of the temperature measuring device X3 is the same as that of the temperature measuring device X2. In this temperature measurement device X3, the pulse width of the ultrasonic waves output from the ultrasonic signal processing device 9 and the ultrasonic transducer 11 ′ is, for example, about 0.5 [μs].
The temperature measurement device X3 is different from the temperature measurement device X2 in the contents of the thickness calculation and temperature calculation of the wafer 1 executed in steps S4 and S9. The contents will be described below.
In step S9, the controller / arithmetic unit 6 'specifies the resonance frequency fr of the ultrasonic wave in the wafer 1 based on the change in the detection signal of the reflected ultrasonic wave recorded in step S8, and the resonance frequency fr. And the temperature Tx of the wafer 1 is calculated based on the thickness L of the wafer 1.
FIG. 6B is a graph showing a change in the detection signal of the reflected ultrasonic wave when the wafer 1 is irradiated with pulsed ultrasonic waves.
As described above, since the ultrasonic waves are multiple-reflected in the wafer 1, even if the resonance condition shown in the equation (a1) is not satisfied, the change in the detection signal of the reflected ultrasonic waves is shown in FIG. The component of the resonance frequency fr appears like the waveform of the section Pe shown.
FIG. 6A is a graph showing changes in detection signals of reflected ultrasonic waves when the wafer 1 does not exist on the wafer stage 2 in the temperature measurement device X2. From FIG. 6A, it can be seen that when the wafer 1 serving as a resonance medium does not exist, the component of the resonance frequency fr does not occur in the detection signal of the reflected ultrasonic wave.
Accordingly, in step S9, the control / arithmetic unit 6 ′ first identifies the resonance frequency fr (frequency of the signal in the section Pe) by performing a waveform analysis of the detection signal of the reflected ultrasonic wave.
Further, in step S9, the control / arithmetic unit 6 ′ applies the equation (a2) to the equation (known relational equation) representing the relationship between the sound speed Vt and the temperature Tx shown in FIG. The temperature Tx of the wafer 1 is calculated by applying the resonance frequency fr and the thickness L of the wafer 1.

Further, as described above, in the normal temperature state before the temperature measurement or the state in which the entire process chamber 8 is maintained at a predetermined temperature, the temperature of the wafer 1 is the detected temperature (environment temperature) of the environmental temperature sensor 7. Can be considered equal.
Therefore, in step S4 before measuring the temperature of the wafer 1, the control / arithmetic unit 6 ′ determines the relationship between the known and unknown thickness L (known) and temperature Tx (unknown) of the wafer 1 in the temperature calculation process described above. By performing the reverse calculation, the thickness L of the wafer 1 is calculated and automatically set based on the detection signal of the reflected ultrasonic wave under the known ambient temperature and the known ambient temperature.

In the embodiment described above, an example in which the waveguide 13 is formed on the wafer stage 2 has been described.
As another embodiment, for example, the ultrasonic transmission / reception unit 10 is provided inside or on the lower surface (surface opposite to the support surface of the wafer 1) of the wafer stage 2, and the wafer stage 2 itself propagates ultrasonic waves. The structure to make it possible is also considered.
Further, the ultrasonic wave emitting surface (upper surface) of the ultrasonic wave transmitting / receiving unit 10 is formed flush with the wafer 1 support surface of the wafer stage 2, and the ultrasonic wave is directly propagated from the ultrasonic wave transmitting / receiving unit 10 to the wafer 1. Configurations are also conceivable.

[Fourth Embodiment]
Next, a semiconductor wafer temperature measuring device X4 (hereinafter referred to as a temperature measuring device X4) according to a fourth embodiment of the present invention will be described with reference to FIG.
Since the temperature measuring device X4 is an application example of the temperature measuring device X1 and the temperature measuring device X2, only the parts different from the temperature measuring devices X1 and X2 will be described below. In FIG. 8, the same components as those of the temperature measuring devices X1 and X2 are denoted by the same reference numerals.
As shown in FIG. 8, the temperature measuring device X4 includes the wafer stage 2, the oscillator 3, the selector 4 ′, the amplifiers 5a and 5b, the control / calculation device 6 ″, the environmental temperature sensor 7, the distributor 20, and the burst. A circuit 21, a gate circuit 22 and a phase detection circuit 23 are provided.
Here, the wafer stage 2, the selector 4 ', and the environmental temperature sensor 7 provided with the ultrasonic transmission / reception units 10' at a plurality of locations are the same as those provided in the temperature measuring device X2.

In the temperature measuring device X4, the oscillator 3, the bursting circuit 21, the amplifier, and the ultrasonic transmission / reception unit 10 'constitute an example of an ultrasonic output unit.
That is, the oscillator 3 outputs a reference oscillation signal So that is a sinusoidal signal having a constant frequency fo, and the burst circuit 21 periodically interrupts the reference oscillation signal So, thereby causing the constant frequency fo. Is converted into a burst signal Sb that appears in a predetermined cycle (hereinafter referred to as an intermittent cycle Tp). The burst signal Sb is amplified by the amplifier 5a and then supplied to the ultrasonic transducer 11 ′ (see FIG. 4) in the ultrasonic transmission / reception unit 10 ′ through the selector 4 ′.
As a result, a burst wave ultrasonic wave having a constant frequency fo is output from the ultrasonic transducer 11 ′ at the intermittent period Tp. Thus, the temperature measuring device X4 outputs a so-called burst wave-like ultrasonic wave in which an ultrasonic wave having a constant frequency fo is intermittent at the intermittent period Tp. For example, the frequency fo is set to about 200 MHz, the ultrasonic pulse width is set to about 2 to 10 wavelengths (0.01 to 0.1 μs), and the intermittent period Tp is set to about 10 μs.
The reference oscillation signal So output from the oscillator 3 is branched into two by the distributor 20, one of the branch signals is transmitted to the burst circuit 21 and the other of the branch signals is sent to the phase detector circuit 23. Is transmitted.

The ultrasonic transducer 11 ′ detects reflected ultrasonic waves that are reflected back within the wafer 1 supported by the wafer stage 2, and the detection signal is sent to the gate circuit through the selector 4 ′ and the amplifier 5b. 22 is transmitted. As described above, the ultrasonic transducer 11 ′ outputs ultrasonic waves in the form of burst waves and detects the reflected waves, thereby performing ultrasonic output and detection in a time-sharing manner. The ultrasonic transducer 11 ′ and the amplifiers 5a and 5b are examples of both ultrasonic output means and ultrasonic detection means.
FIG. 9 is a diagram schematically showing changes in the detection signal of the reflected ultrasonic wave obtained by the temperature measuring device X4.
As shown in FIG. 9, in the temperature measuring device X4, similarly to the temperature measuring device X2, the first reflected ultrasonic wave reflected on the supported surface of the wafer 1 without entering the wafer 1 is detected. Reflected ultrasonic waves that have been reciprocally reflected (multiple reflected) once and a plurality of times between the echo signal and the supported surface of the wafer 1 and the opposite surface (hereinafter, both surfaces are collectively referred to as opposing surfaces). And the second and subsequent echo signals corresponding to. Hereinafter, the plurality of echo signals corresponding to one pulsed ultrasonic wave (output ultrasonic wave) are collectively referred to as an echo signal block Ebk.
Further, in the temperature measuring device X4, since burst wave-like ultrasonic waves that are intermittent at the intermittent period Tp are output, a plurality of echo signal blocks Ebk are detected at the intermittent period Tp as shown in FIG. Is done.

Further, the gate circuit 22 detects the intermittent period Tp of the ultrasonic output from the detection signal of the ultrasonic transducer 11 ′ (that is, the output cycle of the pulsed ultrasonic wave output by the ultrasonic transducer 11 ′). ) Is a circuit for extracting a signal in a predetermined time zone (hereinafter referred to as an extraction time zone) synchronized with the above. The gate circuit 22 acquires a timing signal synchronized with the intermittent period Tp from the bursting circuit 21, and sets the extraction time zone based on the timing signal.
Here, the gate circuit 22 extracts a detection signal of an ultrasonic wave (reflected ultrasonic wave) reciprocally reflected a plurality of times (for example, 2 to 4 times) between the opposing surfaces by signal extraction in the extraction time period. To do. In FIG. 8, a time zone surrounded by a wavy line is an example of the extraction time zone.

The phase detection circuit 23 mixes the extraction signal (a part of the detection signal of the reflected ultrasonic wave) from the gate circuit 22 and the reference oscillation signal So obtained from the oscillator 3 through the distributor 20. This is a circuit that detects the phase of an ultrasonic wave that is reciprocally reflected a plurality of times (for example, 2 to 4 times) between the opposing surfaces by detection and outputs the detection signal. The phase detection signal is transmitted to the control / arithmetic unit 6 ″. The phase detected by the phase detection circuit 23 is the extracted signal of the gate circuit 22 based on the phase of the reference oscillation signal So. Phase (phase difference).
For example, the waveform of the reference oscillation signal So (the signal level Lso at time t) and the signal waveform of the nth (n = 1, 2, 3,...) Echo in each echo signal block Ebk (at time t) The signal level En at the time point can be expressed by the following equations (c1) and (c2), respectively.
Lso = A · sin (2πft + φo) (c1)
En = Bn.sin (2πft + φn) (c2)
In the equation (c1), A is the amplitude of the reference oscillation signal So, φo is the initial phase of the reference oscillation signal So, and A and φo are values that can be set by the oscillator 3. In equation (c2), Bn is the amplitude of the nth echo, and φn is the phase of the nth echo. The initial phase φo can be set by the oscillator 3.

The level Ld of the detection signal obtained by mixing detection of the reference oscillation signal So and the nth echo signal can be expressed by the following equation (c3).
Ld = C.Bn.cos (.phi.n-.phi.o) (c3)
Note that C in the equation (c3) is a constant.
Here, the phase detection circuit 23 performs mixing detection of the reference oscillation signal So and a plurality of echo signals (i-th to j-th (2 ≦ i <j)). The level Ld ′ of the actual detection signal obtained is expressed by the following equation (c4) based on the average amplitude Bn ′ of the i-th to j-th echoes and the average phase φn ′ of the i-th to j-th echoes. Can be expressed as
Ld ′ = C · Bn ′ · cos (φn′−φo) (c4)
As shown in FIG. 7, the velocity (sound velocity) of the ultrasonic wave propagating inside the wafer 1 has a high correlation with the temperature of the wafer 1, and the supersonic wave propagating inside the wafer 1 (reciprocal reflection). The phase of the sound wave is determined according to its propagation time (time required for propagation). The same applies to the average phase φn ′ of the i-th to j-th echoes.

By the way, the equation (c4) includes the unknown numerical value C · Bn ′ in addition to the echo phase φn ′ to be detected. The oscillator 3 changes the initial phase φo of the reference oscillation signal So. By performing the measurement a plurality of times, φn ′ can be detected as the phase of the echo based on the equation (c4). The amplitude A of the reference oscillation signal So is assumed to be constant.
Therefore, the phase detection circuit 23 performs detection under a plurality of conditions in which the initial phase φo of the reference oscillation signal So is changed, and from a plurality of detection signals (signal level Ld ′) obtained by the detection, (c4) Based on the equation, the phase φn ′ (the average phase of the i-th to j-th echoes) of the detection signal of the reflected ultrasonic wave is detected.
As described above, the phase detection circuit 23 is a super-reflector that has been reciprocally reflected a plurality of times (for example, 2 to 4 times) between the opposing surfaces by mixing the extraction signal from the gate circuit 22 and the reference oscillation signal So. The phase φn ′ of the sound wave is detected.
Since the phase of the ultrasonic wave propagating inside the wafer 1 changes greatly as the propagation time becomes longer, the phase φn ′ of the ultrasonic wave reflected and reciprocated a plurality of times (that is, having a long propagation time) between the opposing surfaces By detecting it, it becomes possible to detect the phase with high sensitivity, and in turn, temperature calculation (temperature detection) with high sensitivity becomes possible.

Further, the control / arithmetic apparatus 6 ″ includes a processor (calculation means) for executing a predetermined program stored in the storage unit in advance, like the control / arithmetic apparatus 6 in the temperature measuring devices X1 and X2. The processor executes control of the oscillator 3 and processing for calculating the thickness and temperature of the wafer 1 based on the detection signal of the phase φn ′ obtained through the phase detection circuit 23.
If the thickness L of the wafer 1 is constant, there is a certain correlation between the phase φn ′ of the reflected ultrasonic detection signal and the temperature of the wafer 1.
Therefore, the storage / control unit 6 ″ stores the thickness / temperature / phase correspondence indicating the correspondence between the thickness L, temperature, and phase φn ′ of the wafer 1 obtained in advance by actual measurement of the wafer 1 of known thickness. Information (such as correspondence table or correspondence formula) is stored in advance.
Further, as described above, in a normal state before temperature measurement or in a steady state where the entire process chamber 8 is maintained at a predetermined temperature, the temperature of the wafer 1 is detected by the environmental temperature sensor 7 (environment temperature). Can be regarded as equal.
Therefore, in the steady state, the control / arithmetic unit 6 ″ uses the detected temperature of the environmental temperature sensor 7, the phase φn ′ detected by the phase detection circuit 23, and the thickness / temperature / phase correspondence information. Based on this, the thickness L of the wafer 1 is calculated and automatically set (corresponding to step S4 in FIG. 2).
Further, the control / arithmetic unit 6 ″, after the wafer 1 is heated, has a phase φn ′ detected by the phase detection circuit 23, a preset thickness L of the wafer 1, and the thickness / temperature / phase correspondence. Based on the information, the temperature Tx of the wafer 1 is calculated (corresponding to step S9 in FIG. 2).
Also with the temperature measuring device X4 shown above, the temperature of the processing object such as the wafer 1 can be easily measured stably and with high accuracy while avoiding contamination due to contact.
In the temperature measurement device X4, the gate circuit 22, the phase detection circuit 23, and the control / calculation device 6 ″ are examples of the temperature calculation means.

  The present invention is applicable to a temperature measuring apparatus and method for measuring the temperature of an object to be processed such as a semiconductor wafer.

1 is a schematic configuration diagram of a semiconductor wafer temperature measuring device X1 according to a first embodiment of the present invention. The flowchart showing the temperature measurement procedure by the semiconductor wafer temperature measurement apparatus X1. The figure showing the relationship between the ultrasonic frequency obtained by the semiconductor wafer temperature measuring apparatus X1, and reflected ultrasonic intensity. The schematic block diagram of the semiconductor wafer temperature measuring apparatus X2 which concerns on 2nd Embodiment of this invention. The figure which represented typically the change of the detection signal of the reflected ultrasonic wave obtained by the semiconductor wafer temperature measuring apparatus X2. The graph showing the change of the detection signal of the reflected ultrasonic wave obtained by the semiconductor wafer temperature measuring apparatus X3 which concerns on 3rd Embodiment of this invention. The figure showing the relationship between the temperature of a substance, and the longitudinal wave propagation velocity in the substance. The schematic block diagram of the semiconductor wafer temperature measuring apparatus X4 which concerns on 4th Embodiment of this invention. The figure which represented typically the change of the detection signal of the reflected ultrasonic wave obtained by the semiconductor wafer temperature measuring apparatus X4.

Explanation of symbols

X1, X2, X3, X4: Semiconductor wafer temperature measuring device 1: Semiconductor wafer 2: Wafer stage 3: Oscillator 4, 4 ′: Selector 5, 5a, 5b: Amplifier 6, 6 ′, 6 ″: Control / arithmetic unit 7 : Environmental temperature sensor 8: Process chamber 9: Ultrasonic signal processing device 10, 10 ': Ultrasonic transmitter / receiver 11: Ultrasonic transducer for transmission 12: Ultrasonic transducer for reception 11': Ultrasonic transducer 13: Guide Waveguide 20: Distributor 21: Burst circuit 22: Gate circuit 23: Phase detection circuit

Claims (10)

A temperature measuring device comprising a support table for supporting a flat semiconductor wafer on one surface thereof, and measuring the temperature of the semiconductor wafer supported by the support table,
Ultrasonic output means for outputting ultrasonic waves to the semiconductor wafer from the support base side;
Ultrasonic detection means for detecting reflected ultrasonic waves reflected on the semiconductor wafer ;
Temperature calculation means for calculating the temperature of the semiconductor wafer based on a detection signal of the ultrasonic detection means;
An ultrasonic wave formed of an elastic member formed between the ultrasonic wave output means and the semiconductor wafer in the support base and having a small ultrasonic wave propagation loss and does not contaminate the semiconductor wafer even if it comes into contact with the semiconductor wafer. A waveguide;
Equipped with,
The ultrasonic output means outputs ultrasonic waves to the semiconductor wafer through the waveguide;
The ultrasonic detection means detects reflected ultrasonic waves reflected on the semiconductor wafer and returning through the waveguide;
The temperature calculating means is configured to set a temperature of the semiconductor wafer based on a thickness of the semiconductor wafer set in advance based on a detection signal from the ultrasonic detection means and a detection signal from the ultrasonic detection means. The temperature measuring device characterized by calculating . The temperature calculating means is
The subjected to ultrasonic particular or the semiconductor of the ultrasonic wave propagated in the wafer propagation time or detection of the phase of the resonance frequency in said semiconductor wafer on the basis of a detection signal of the ultrasonic detection means, in response to said result The temperature measuring apparatus according to claim 1, wherein the temperature of the semiconductor wafer is calculated. Frequency sweeping means for performing frequency sweeping of the ultrasonic wave output by the ultrasonic wave output means,
The temperature calculating means is
Identifying the resonance frequency of the ultrasonic wave in the semiconductor wafer based on the sweep frequency of the ultrasonic wave by the frequency sweeping unit and the intensity of the detection signal of the ultrasonic wave detection unit that changes according to the frequency sweep of the ultrasonic wave, The temperature measuring device according to claim 2, wherein the temperature of the semiconductor wafer is calculated based on the resonance frequency. The ultrasonic output means outputs pulsed ultrasonic waves,
The temperature calculating means is
Based on the detection signal of the ultrasonic detection means, a difference in arrival time of the ultrasonic waves reflected by the surface of the semiconductor wafer supported by the support base and the opposite surface thereof to the ultrasonic detection means is detected. The temperature measuring device according to claim 2, wherein the temperature of the semiconductor wafer is calculated based on the detection result. The ultrasonic output means outputs pulsed ultrasonic waves,
The temperature calculating means is
The ultrasonic wave resonance frequency in the semiconductor wafer is specified based on a change in a detection signal of the ultrasonic wave detection means, and the temperature of the semiconductor wafer is calculated based on the resonance frequency. Temperature measuring device. The ultrasonic output means outputs a plurality of burst wave ultrasonic waves having a constant frequency at a predetermined period,
The temperature calculation means calculates the phase of the reflected ultrasonic wave reflected back and forth between the surface of the semiconductor wafer supported by the support base and the opposite surface which is the opposite surface from the detection signal of the ultrasonic detection means. The temperature measuring apparatus according to claim 2, wherein the temperature is detected and the temperature of the semiconductor wafer is calculated based on the phase.   The temperature calculation unit is configured to mix the detection signal of the ultrasonic detection unit and the reference oscillation signal generated by the ultrasonic output unit and oscillated at the frequency of the ultrasonic wave. The temperature measuring device according to claim 6, wherein the temperature is detected.   The temperature calculating means extracts a signal in a predetermined time period synchronized with the burst wave-like ultrasonic wave output period by the ultrasonic wave output means from the detection signal of the ultrasonic wave detecting means, and the extracted signal and the reference oscillation signal The temperature measuring device according to claim 7, wherein the phase of the ultrasonic wave reflected and reciprocated a plurality of times between the opposing surfaces is detected by mixing with the counter. The ultrasonic output means includes a plurality of ultrasonic transducers provided for each of a plurality of measurement positions on the support base, and one AC signal supply unit that supplies an AC signal to the ultrasonic transducers,
The ultrasonic detection means includes a plurality of ultrasonic transducers provided for each of the plurality of measurement positions, and one signal input unit to which the detection signals of the reflected ultrasonic waves output from the ultrasonic transducers are input. Have
The temperature measuring device includes a signal path between the plurality of ultrasonic transducers and the AC signal supply unit in the ultrasonic output unit, and the plurality of ultrasonic transducers and the signal input in the ultrasonic detection unit. Signal path switching means for sequentially switching the signal path to the unit,
The temperature calculation unit corresponds to each of the plurality of measurement positions on the semiconductor wafer based on the detection signal of the reflected ultrasonic wave obtained through the signal input unit every time the signal path is switched by the signal path switching unit. The temperature measuring device according to claim 1, wherein the temperature of the position is calculated. A temperature measuring method for measuring the temperature of a semiconductor wafer in a state where a flat semiconductor wafer is supported by a support on one surface thereof,
An ultrasonic output step of outputting ultrasonic waves to the semiconductor wafer from the support table side by an ultrasonic output means;
An ultrasonic detection step of detecting reflected ultrasonic waves reflected on the semiconductor wafer by an ultrasonic detection means;
A temperature calculating step of calculating a temperature of the semiconductor wafer based on a detection signal in the ultrasonic detection step by an arithmetic means;
Have,
In the ultrasonic output step, the ultrasonic output means is formed between the ultrasonic output means and the semiconductor wafer on the support base and is in contact with the semiconductor wafer with a small ultrasonic propagation loss. And outputting ultrasonic waves to the semiconductor wafer through an ultrasonic waveguide made of an elastic member that does not contaminate the semiconductor wafer,
In the ultrasonic detection step, the ultrasonic detection means detects reflected ultrasonic waves that are reflected by the semiconductor wafer and returned through the waveguide,
In the temperature calculation step, the calculation means is based on the thickness of the semiconductor wafer set in advance based on the detection signal from the ultrasonic detection means and the detection signal from the ultrasonic detection means, A temperature measuring method comprising calculating a temperature of the semiconductor wafer .

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