JPH07311181A - Method and apparatus for detecting surface state of substrate using sound wave - Google Patents

Abstract

PURPOSE:To detect variation in the surface state of a substrate, including a cleaning state or a state where transparent matters are adhering, by detecting a sound wave generated through interaction of a laser pulse and the surface of the substrate simultaneously with the cleaning on the surface of the substrate through irradiation with pulse laser. CONSTITUTION:A pulse beam from an KrF excimer laser oscillator 10 is fed to an optical system 12 where the energy density is made uniform and a substrate 18 on a stage 16 is irradiated with the pulse beam from the optical system 12 through a mirror 14. A sound wave generated through the irradiation is detected by means of a microphone 24, amplified through a preamplifier 26, and A/D converted 28 before being fed through an interface 20 to a RAM 22C at a control section 22 to be stored therein. A controller 30 delivers a pulse signal to the oscillator 10 and actuates a trigger 32 to cause the control section to deliver the digital sound wave signal to an oscilloscope 34. the oscilloscope 34 detects variation on the surface of the substrate 18 based on the amplitude, frequency spectrum, etc., of the detected sound wave.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound wave for detecting the state of the surface of a semiconductor, a metal, a ceramics, a magnetic material, an optical element or the like (hereinafter collectively referred to simply as "substrate surface"). More specifically, the present invention relates to a substrate surface detection method and apparatus using the same, and more specifically, a substrate surface cleaning state in a substrate surface cleaning method by pulsed laser irradiation to the substrate surface and pulse
The present invention relates to a method and an apparatus for detecting a substrate surface using sound waves capable of detecting in real time changes in the substrate surface state in a surface processing process other than the cleaning of the substrate surface caused by laser irradiation.

[0002]

BACKGROUND OF THE INVENTION At present, as a cleaning method for removing deposits such as organic stains and inorganic stains adhering to the surface of a substrate from the surface of the substrate, for example, an application by the applicant of the present application is applied. Japanese Patent Application 5-19
As disclosed in No. 5538 “Dry cleaning method for substrate surface”, a substrate having a deposit as an object to be removed on the surface is irradiated with a pulsed laser having a short wavelength pulsed output beam. Then, there is known a cleaning method for removing the deposits attached to the surface of the substrate.

Conventionally, when the substrate surface is cleaned by such a cleaning method using a pulsed laser, an image receiving device such as an eye microscope or an optical microscope or a CCD camera and a video monitor are used to detect the cleaning state of the substrate surface. A detection method using a display device such as the above has been used, and the observation and analysis of the substrate surface have been performed by this.

However, in the above-described detection method using the visual observation, the image receiving device such as the optical microscope or the CCD camera, and the display device such as the video monitor, the cleaning process of irradiating the substrate with the pulse laser is temporarily interrupted. After that, the detection must be performed by the above detection method, and there is a problem in that it cannot be detected in real time while performing the cleaning process. Therefore, the above-mentioned detection method has a problem that the work efficiency and the detection accuracy are not so good.

Further, there is a problem that the above-mentioned detection method using visible light cannot detect an adhered matter which is transparent to visible light and adheres to the surface of the substrate.

Further, as a highly accurate method for detecting a substrate surface, there are electron microscopy (SEM), Auger electron spectroscopy (AES), X-ray induced electron spectroscopy (XPS), etc. None of them have the problems that they cannot be detected in real time, the detection time is long, and an expensive device is required.

On the other hand, as a method for detecting the substrate surface in real time, a method for measuring the surface reflectance with a laser is known. In this method for measuring the surface reflectance with a laser, a local minute inside the laser spot is detected. There is a problem that it is not possible to detect only the state of the area, and it is also impossible to detect a transparent deposit.

Further, in addition to the cleaning method using a pulse laser as disclosed in Japanese Patent Application No. 5-195538 “Dry cleaning method for substrate surface”, by irradiating the substrate surface with a pulse laser, As a method for detecting a change in the substrate surface state in the surface processing process accompanied by a change in the substrate surface state, a detection method using an image receiving device such as a visual measurement or an optical microscope or a CCD camera, and a display device such as a video monitor, an electron microscope. A detection method such as the SEM method (SEM), Auger electron spectroscopy (AES) or X-ray induced electron spectroscopy (XPS), and a surface reflectance measurement method using a laser are generally known, but the same problems as described above are still encountered. Was pointed out.

The present invention has been made in view of the above-mentioned various problems of the prior art as described above, and an object of the present invention is to irradiate a substrate surface by pulsed laser irradiation. In addition to being able to detect in real time the cleaning state in the cleaning method described above and the changes in the substrate surface state in the surface processing process that accompany changes in the substrate surface state due to pulsed laser irradiation to the substrate surface, the detection time and the device It is possible to significantly reduce the detection cost such as, and it is possible to deal with various kinds of deposits including the deposits adhered to the surface of the substrate which is transparent to visible light and light of other wavelengths and the substrate material. A method of detecting a substrate surface using a sound wave and an apparatus therefor are provided.

[0010]

In order to achieve the above object, a method and apparatus for detecting a substrate surface using a sound wave according to the present invention include a substrate surface cleaning and other surface processing by irradiation of the pulse laser described above. In order to detect changes in the substrate surface condition during
By irradiating the substrate surface with a laser, a sound wave generated from the substrate surface is detected, and based on the sound wave, a change in the substrate surface is detected in real time.

For example, for cleaning the substrate surface or other treatment, a pulsed laser is applied to a predetermined area on the substrate, and at the same time, a sound wave generated by the interaction between the laser pulse and the substrate surface is detected. .
At this time, a sound wave may be detected using a microphone or the like. Then, based on the detected amplitude and frequency spectrum of the sound wave, the change state of the substrate surface (such as the cleaning state of the adhered substances on the substrate surface) is detected.

[0012]

[Operation] Before the detection of the surface of the substrate, the sample formed by the same material as the substrate to be cleaned by irradiating a pulsed laser or to be surface-processed has the same shape. Clean the surface.
In cleaning the sample surface, not only the cleaning method by irradiating the substrate surface with the pulsed laser, but also any cleaning method may be used.

Next, the surface of the sample is irradiated with a pulse laser having the same parameters as the pulse laser used for cleaning the surface of the substrate, and the amplitude and frequency spectrum of the sound wave generated at this time are stored in advance. deep.

After that, for example, the substrate surface is irradiated with a pulse laser to start cleaning, and the amplitude and frequency spectrum of the sound wave generated from the surface of the substrate each time the laser pulse irradiates the surface of the substrate. Is compared with the amplitude and frequency spectrum of the sound wave generated from the sample surface stored in the storage means.

As the cleaning performed by irradiating the substrate with the pulsed laser progresses, the amplitude and frequency spectrum of the sound wave generated from the surface of the substrate approaches the amplitude and frequency spectrum of the sound wave generated from the surface of the sample. Come on.

Therefore, the cleaning condition of the substrate surface can be confirmed by detecting the amplitude and frequency spectrum of the sound wave generated from the sample surface.

By the way, it is considered that the above-described method and apparatus for detecting a substrate surface using sound waves are realized by the following three mechanisms acting comprehensively, and these three mechanisms are: (1) Generation of sound wave from substrate surface by laser pulse (2) Change in substrate surface reflectance due to cleaning or other treatment of substrate surface by irradiation of pulsed laser on substrate surface, (3) Adhesion to substrate surface This is an effect on the substrate surface vibration due to the presence of adhered substances.

First, the mechanism of (1) above will be explained. In the interaction between the pulse laser and the substrate surface, the photons in the laser pulse act on the substrate surface as an energy source and a momentum source. Here, the photons in the laser pulse have an energy of hν per photon and a momentum of h / λ (where “h: Planck's constant”, “ν: laser frequency” and “λ: laser wavelength”). ".).

That is, when the substrate is irradiated with the pulsed laser, the substrate absorbs a part of the laser light, and the energy and momentum of the photons are given to the substrate surface.

By the way, since the instantaneous energy density of the pulsed laser is extremely high, the impact of the energy and momentum of the laser light on the interface between the substrate surface and the deposits adhering to the substrate surface is momentarily large. Become. This impact causes a vibration on the substrate surface, and a sound wave is generated on the substrate surface.

The amplitude and frequency spectrum of the sound wave generated as described above include the energy density of the laser pulse, the wavelength, the pulse width, the surface condition of the substrate (presence and types of deposits on the substrate surface, reflectance, etc.). ), Depending on the substrate material and the size and shape of the substrate.

Next, the mechanism of (2) above will be explained. When the substrate surface is irradiated with a pulsed laser to clean the substrate surface, the number of laser pulses irradiated on the substrate surface is increased. According to
The reflectivity (or absorptivity) of the substrate surface changes (in most cases the reflectivity increases). Thereby,
The energy (or momentum) of the laser pulse absorbed on the substrate surface changes.

Therefore, the amplitude and frequency spectrum of the sound wave generated from the substrate surface will change.

To explain the mechanism (3), the vibration characteristic of the surface of the substrate changes due to the presence of the deposits attached to the surface of the substrate.

Therefore, when the substrate surface is irradiated with the pulsed laser to clean the substrate surface, the vibration characteristics of the substrate surface change as the deposits on the substrate surface are removed. As a result, the amplitude and frequency spectrum of the sound wave generated from the substrate surface changes.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a substrate surface detecting method using a sound wave and its apparatus according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a schematic structure of an embodiment of a substrate surface detecting apparatus using sound waves according to the present invention.

The substrate surface detecting apparatus using a sound wave according to the present invention shown in FIG. 1 is cleaned by using a pulse laser as disclosed in Japanese Patent Application No. 5-195538, "Dry cleaning method for substrate surface". In the method, it is used when the cleaning state of the substrate surface is detected in real time.

That is, in the substrate surface detecting apparatus using this sound wave, a pulse laser for irradiating the substrate surface in order to remove adhering substances such as organic stains and inorganic stains adhering to the substrate surface from the substrate surface. The KrF excimer laser in the excimer laser is adopted as the reference numeral 10, and the reference numeral 10 indicates the KrF excimer laser oscillator 10.
Is shown. This KrF excimer laser oscillator 1
From 0, a pulsed output beam (pulse beam) having a wavelength of 248 nm and a pulse width of 20 ns is output.

Pulses other than excimer lasers
It is needless to say that a YAG laser, a CO ₂ laser, a semiconductor laser, or the like may be appropriately selected and used as the laser according to the type of the substrate material or the adhered substance, and the same effects as those of the present embodiment can be obtained. Obtainable.

Further, in the substrate surface detecting apparatus using this sound wave, the pulse beam output from the KrF excimer laser oscillator 10 is converted into a beam having a uniform light intensity distribution by an optical system such as a beam homogenizer. With the device 12, the energy density is homogenized and adjusted to a suitable value. Then, the direction is changed by the mirror 14, and the surface of the substrate 18 placed on the movable stage 16 is irradiated with the light.

The optical system device 12 and the stage 16 are connected to the CPUs 22a, R through the interface 20.
It is connected to and controlled by a control unit 22 including an OM 22b and a RAM 22c.

The ROM 22b stores a program for executing an algorithm of software related to the implementation of the present invention, which will be described in detail later with reference to the flowchart shown in FIG.

Further, the RAM 22c is in a clean state by irradiating one laser pulse from the KrF excimer laser oscillator 10 onto the surface of the substrate 18 in a clean state read from a database (not shown). An area for storing sound waves generated from the surface of the substrate 18 and an area used as a working area when the CPU 20a executes the program stored in the ROM 20b are set.

Further, a microphone 24 is arranged adjacent to the substrate 18 with an appropriate distance and angle with respect to the substrate 18, and the sound wave generated from the substrate 18 is detected by the microphone 24. It

The analog signal of the sound wave output from the microphone 24 is temporarily amplified by the preamplifier 26. Then, after being converted into a digital signal by the A / D converter 28, it is sent to the interface 20.

Further, the KrF excimer laser oscillator 1
0 is a controller 3 for controlling the output etc.
0 is connected. The controller 30 sends a pulse signal to the KrF excimer laser oscillator 10 and, at the same time, outputs a pulse signal from the synchro output to the trigger device 32. When the pulse signal output from the synchro output of the controller 30 is input to the trigger device 32, the trigger device 32 causes the interface device 20 to operate.
The trigger signal is output to.

That is, the KrF excimer laser oscillator 1
Whenever one laser pulse is emitted from 0, the trigger device 32 operates as a trigger to output a trigger signal to the interface 20, and the control unit 22 starts reading the digital signal of the sound wave transmitted from the microphone 24. It is done like this.

Reference numeral 34 is an oscilloscope for observing the sound wave waveform, and a monitor 36 for observing the state of the surface of the substrate 18 is connected to the controller 22.

FIG. 2 is a flow chart showing the software algorithm of the present invention. First, step S20.
2, before starting the cleaning process by irradiating the surface of the substrate 18 with the pulsed laser, the control unit 22 sets the substrate parameters of the substrate 18 such as the type, shape and size of the material of the substrate 18 as an object to be cleaned. To be stored in a predetermined area of the RAM 22c.

When the process of step S202 is completed, the process proceeds to step S204, and the energy of the pulse laser output from the KrF excimer laser oscillator 10,
Pulse width, wavelength and energy density
The laser parameters of the laser are input to the control unit 22 and stored in a predetermined area of the RAM 22c.

When the processing in step S204 is completed, the process proceeds to step S206, and the clean substrate corresponding to the substrate parameter set in step S202 is irradiated with the pulse laser corresponding to the laser parameter set in step S204. At this time, the parameters (amplitude and frequency spectrum, etc.) of the sound wave generated from the clean surface of the substrate are searched from a database created in advance, and this is used as a predetermined sound wave parameter indicating a standard sound wave waveform in a predetermined area of the RAM 22c. Store in the area.

When the processing of step S206 is completed, the process proceeds to the processing of step S208 and subsequent steps, and the surface of the substrate 18 is irradiated with the laser pulse from the KrF excimer laser oscillator 10 by the cleaning process, and the surface of the substrate 18 is irradiated. The sound wave generated is detected by the microphone 24 to detect the cleaning state of the surface of the substrate 18 in real time.

That is, in step S208, KrF
The surface of the substrate 18 is irradiated with one pulse of the laser pulse from the excimer laser oscillator 10.

When the process of step S208 is completed, the process proceeds to step S210, and a parameter of a sound wave (generated sound wave parameter) generated from the surface of the substrate 18 by the irradiation of one pulse of the laser pulse in step S208.
And the standard sound wave parameters.

When the process of step S210 is completed, the process proceeds to step S212, and it is determined from the comparison result of step S208 whether the sound wave generated from the surface of the substrate 18 and the sound wave generated from the surface of the clean substrate are the same. To do.

When the determination result of step S212 is negative (N), that is, when the sound wave generated from the surface of the substrate 18 and the sound wave generated from the surface of the clean substrate are different, the surface of the substrate 18 is clean. If not, the process returns to step S208, and the above-described processing is repeated. That is, the surface of the substrate 18 is cleaned by irradiating the surface of the substrate 18 again with one pulse of the laser pulse from the KrF excimer laser oscillator 10.
After that, the above step S210 → step S21
Process 2 is performed.

On the other hand, if the determination result of step S212 is affirmative (Y), that is, if the sound wave generated from the surface of the substrate 18 and the sound wave generated from the surface of the clean substrate are the same, the process proceeds to step S214. It is determined whether or not an uncleaned region remains on the substrate 18.

If the determination result of step S214 is affirmative, that is, if there is an uncleaned region on the substrate 18, the stage 16 is moved and the process returns to step S208 to repeat the above-described processing.

On the other hand, if the determination result in step S214 is negative, that is, if the entire surface of the substrate 18 has been cleaned, the cleaning process and the substrate surface detection processing using sound waves according to the present invention are terminated.

As described above, in this embodiment, when the cleaning process using the pulse laser is started, the sound wave generated from the surface of the substrate 18 is detected by the microphone 24 for each pulse, and the sound wave is converted into a digital signal. And outputs to the control unit 22. Then, the control unit 22
The generated sound wave parameter of the sound wave sent from the microphone 24 is compared with the standard sound wave parameter. When the difference between the generated sound wave parameter and the standard sound wave parameter satisfies the preset determination criterion, the control unit 22 determines that the sound wave sent from the microphone 24 and the sound wave from the clean surface of the substrate are the same, It is determined that the surface of the substrate 18 is clean. Then, the stage 16 is moved to clean the other area of the substrate 18.

Therefore, the substrate 18 can be cleaned with the minimum number of pulses without wasting the laser pulse from the KrF excimer laser oscillator 10.

That is, by irradiating the surface of the substrate 18 with one pulse of the laser pulse from the KrF excimer laser oscillator 10, the substrate 18 read by the control unit 22.
The sound wave generated from the surface of the substrate 18 is a sound wave previously stored in the RAM 22c (the surface of the substrate 18 is irradiated with one pulse of the laser pulse from the KrF excimer laser oscillator 10 on the cleaned surface of the substrate 18). Sound waves generated from the. And the substrate 1
While repeating the irradiation of the laser pulse from the KrF excimer laser oscillator 10 onto the surface of the substrate 8, the substrate 18
When the waveform of the sound wave generated from the surface of the substrate approaches the waveform of the sound wave generated from the cleaned substrate 18 stored in the RAM 22c and the preset criteria are satisfied, the control unit 22 automatically sets the substrate. It is determined that the cleaning of the surface of 18 has been completed and the surface of the substrate 18 has become clean.

The experimental examples according to the present invention will be described below.

FIGS. 3A and 3B show an unclean substrate surface before cleaning by a pulse laser when a copper substrate is used as the substrate 18 (FIG. 3A).
FIG. 4 is an optical micrograph of a substrate surface magnified 400 times, showing a clean substrate surface after cleaning with a pulse laser (FIG. 3B).

As shown in FIG. 3 (a), contaminants such as oil can be observed as deposits on the surface of the substrate which is not clean before cleaning with the pulse laser. In order to clean such a copper substrate shown in FIG. 3A (which is "copper" as a material of the substrate parameter), a laser parameter of 248 nm is used.
The laser beam from the KrF excimer laser oscillator 10 having the wavelength of is narrowed down to “0.3 cm × 0.8 cm” by the quartz lens as the optical system device 12. Then, when the copper substrate was irradiated with 5 pulses at a pulse energy of 100 mJ, the clean substrate shown in FIG. 3B could be obtained.

In the following description, such a change in the cleaning state of the surface of the copper substrate will be detected.

First, the apparatus shown in FIG.
A pulsed laser from the KrF excimer laser oscillator 10 is radiated to the clean surface of the copper substrate shown in (1) to detect a sound wave generated from the surface of the copper substrate with the microphone 24, and a sound wave signal output from the microphone 24. When the (analog signal) is amplified 100 times by the preamplifier 26 and observed by the oscilloscope 34, a sound wave waveform as shown in FIG. 4 is observed. The sound wave waveform shown in FIG. 4 is obtained as a sound wave generated from a clean substrate surface, and standard sound wave parameters are obtained and stored in a database to store RA.
Make it read by M22c.

The scale in FIG. 4 has a vertical axis of 1
V / div and the horizontal axis is 500 μs / div.
As is clear from FIG. 4, the amplitude of the waveform on the clean substrate surface is extremely small.

Next, the apparatus shown in FIG.
When the pulsed laser from the KrF excimer laser oscillator 10 is radiated on the copper substrate surface on which the contaminant shown in (1) adheres, one pulse at a time, the waveform of the sound wave generated from the copper substrate surface is simultaneously measured according to the flowchart shown in FIG. Is done.

A sound wave waveform as shown in FIG. 5A is obtained depending on the first laser pulse. Figure 5 (a)
The waveform shown in () has a large amplitude enough to shake the output range of the preamplifier 26. This large amplitude indicates the presence of large amounts of contaminants on the copper substrate surface. As a matter of course, unlike the sound wave waveform shown in FIG. 5A and the sound wave waveform shown in FIG. 4, the generated sound wave parameter and the sound wave standard parameter do not match, so the determination in step S212 is negative and the step Return to S208.

Next, when the second laser pulse is irradiated, a sound wave waveform as shown in FIG. 5B is obtained. Comparing the acoustic wave waveform of FIG. 5 (a) and the acoustic wave waveform of FIG. 5 (b), the amplitude is significantly reduced, which indicates that the contaminants on the copper substrate surface are reduced. Shows.

Further, when the third laser pulse is irradiated, a sound wave waveform as shown in FIG.
When the th laser pulse is irradiated, a sound wave waveform as shown in FIG. 6B is obtained. In this way, the laser
Each time the copper substrate surface is irradiated with the pulse, the amplitude of the sound wave waveform becomes smaller.

Then, when the fifth laser pulse was irradiated, a sound wave waveform as shown in FIG. 7 was obtained. The sound wave waveform shown in FIG. 7 is almost the same as the sound wave waveform shown in FIG. 4, which means that the surface of the copper substrate has become clean. At this time, the generated sound wave parameter and the sound wave standard parameter substantially match, and the control unit 22 determines that the surface of the copper substrate has become clean.

As described above, the sound wave generated from the surface of the copper substrate changes each time the laser pulse is irradiated, so that the sound wave generated from the surface of the copper substrate becomes the same as the sound wave generated from the surface of the clean copper substrate. It can be determined that the surface of the copper substrate is also clean.

Next, an example of an experiment for cleaning a copper substrate whose surface is filled with a felt pen will be described.

FIG. 8A is an optical micrograph of the surface of a copper substrate whose surface is painted with a felt pen. Such felt pen fills result in surface-attached contaminants with a thickness of a few μm. On the other hand, when the first laser pulse is irradiated, a sound wave waveform as shown in the lower part of FIG. 8B is obtained. Then, when pulse laser irradiation is continued for 20 pulses, the result of FIG.
The sound wave waveform as shown in the upper part of (b) is obtained, which shows that the surface of the copper substrate is clean.

Therefore, according to the present invention, it is possible to surely perform cleaning on a substrate having an adhered substance unevenly distributed on the substrate surface without irradiating useless laser pulses. Therefore, it is not necessary to perform useless work, and the risk of damaging the substrate can be eliminated.

Further, visual measurement using light, an optical microscope, C
It becomes possible to reliably detect a transparent substrate surface adhering matter that cannot be discriminated by a CD camera or the like.

In the above embodiment, the detection of the cleaning state in the method of cleaning the substrate surface by irradiating the substrate surface with the pulsed laser is described, but the present invention is not limited to this.
Needless to say, the present invention may be used to detect changes in the substrate surface state in the surface processing process that accompanies other changes in the substrate surface state due to laser irradiation.

[0071]

Since the present invention is constructed as described above, it has the following effects.

A cleaning state in a method for cleaning a substrate surface by irradiating a pulsed laser on the substrate surface and a change in the substrate surface state in a surface processing process accompanied by a change in other substrate surface states by the pulsed laser irradiation on the substrate surface It is possible to detect in real time, and it is possible to significantly reduce the detection time and the detection cost of the device and the like as compared with the conventional technology.

Further, when detecting the cleaning state in the method of cleaning the substrate surface by irradiating the substrate surface with a pulsed laser, the adhered matter adhering to the substrate surface is transparent to visible light and light of other wavelengths. It is possible to reliably detect the presence of an adhering substance on the surface of the substrate even if it is an adhering substance, and it is possible to detect the state of the surface of the substrate regardless of the material of the substrate.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of an embodiment of a substrate surface detection apparatus using a sound wave according to the present invention.

FIG. 2 is a flow chart showing an algorithm of software of the substrate surface detection apparatus using a sound wave according to the present invention.

FIGS. 3 (a) and 3 (b) show a non-clean substrate surface before cleaning with a pulsed laser (FIG. 3 (a)) and a pulsed substrate when a copper substrate is used as a substrate.
FIG. 4 shows a clean substrate surface (FIG. 3B) after cleaning with a laser, and is an optical microscope photograph in which the substrate surface is magnified 400 times.

FIG. 4 shows a clean surface copper substrate shown in FIG.
A pulse laser from a KrF excimer laser oscillator is irradiated for one pulse, a sound wave generated from the surface of the copper substrate is detected by a microphone, and a sound wave signal (analog signal) output from the microphone is amplified 100 times by a preamplifier, It is a photograph of a sound wave waveform when observed with an oscilloscope, and the scale has a vertical axis of 1 V / div and a horizontal axis of 500 μs / div.

FIG. 5: The copper substrate surface on which the contaminants shown in FIG. 3 (a) adhere is irradiated with a pulse laser from a KrF excimer laser oscillator, and the sound wave generated from the copper substrate surface is detected by a microphone. It is a photograph of the sound wave waveform when the sound wave signal (analog signal) output from the device is amplified 100 times with a preamplifier and observed with an oscilloscope, and the scale is 1 V / div on the vertical axis and 50 on the horizontal axis.
It is 0 μs / div, and FIG. 5A shows a state by irradiation with the first pulse laser, and FIG. 5B shows a state by irradiation with the second pulse laser.

FIG. 6 is a diagram illustrating a case where a copper substrate surface having contaminants shown in FIG. 3A is irradiated with a pulse laser from a KrF excimer laser oscillator, and sound waves generated from the copper substrate surface are detected by a microphone. It is a photograph of the sound wave waveform when the sound wave signal (analog signal) output from the device is amplified 100 times with a preamplifier and observed with an oscilloscope, and the scale is 1 V / div on the vertical axis and 50 on the horizontal axis.
It is 0 μs / div, and FIG. 6A shows the state by the irradiation of the third pulse laser, and FIG. 6B shows the state by the irradiation of the fourth pulse laser.

FIG. 7: The fifth pulse laser from the KrF excimer laser oscillator is applied to the surface of the copper substrate on which the contaminant shown in FIG. 3 (a) is attached, and the sound wave generated from the surface of the copper substrate is detected by the microphone. Then, the sound wave signal (analog signal) output from the microphone is 100
It is a photograph of a sound wave waveform when double-amplified and observed with an oscilloscope. The vertical axis of the scale is 1 V / div and the horizontal axis is 500 μs / div.

FIG. 8 (a) is an optical micrograph of a copper substrate surface whose surface is painted with a felt pen, magnified 400 times, and FIG. 8 (b) is a KrF excimer film shown in FIG. 8 (a).
Sound wave signal (analog signal) output from microphone by radiating pulse laser from laser oscillator, detecting sound wave generated from copper substrate surface with microphone
Is a photograph of the sound wave waveform when it was amplified 100 times with a preamplifier and observed with an oscilloscope. The vertical axis of the scale is 1
V / div, the horizontal axis is 500 μs / div, the upper part of FIG. 8 (b) shows the state by irradiation of the 20th pulse laser, and the lower part of FIG. 8 (b) shows the state of the first pulse laser. The state by irradiation is shown.

[Explanation of symbols]

 10 KrF Excimer Laser Oscillator 12 Optical System Device 14 Mirror 16 Stage 18 Substrate 20 Interface 22 Control Unit 22a CPU 22b ROM 22c RAM 24 Microphone 26 Preamplifier 28 A / D Converter 30 Controller 32 Trigger Device 34 Oscilloscope 36 Monitor

Claims (8)

[Claims] 1. A substrate surface is irradiated with a pulsed laser,
A substrate surface state detection method using a sound wave, characterized in that the state of the substrate surface is detected based on a sound wave generated from the substrate surface by irradiation of the pulsed laser. 2. The method for detecting a substrate surface state using a sound wave according to claim 1, wherein the pulsed laser is a pulsed laser which irradiates the substrate surface to clean the substrate surface. 3. The substrate surface state detecting method using a sound wave according to claim 1, wherein the state of the substrate surface is detected in the atmosphere or gas. 4. The state of the substrate surface is detected based on the amplitude or frequency spectrum of a sound wave generated from the substrate surface by the irradiation of the pulsed laser. Method of substrate surface condition using the sound wave of. 5. A pulsed laser irradiation means for irradiating a pulsed laser, and when the pulsed laser irradiation means irradiates the desired substrate surface with a pulsed laser, the pulsed laser irradiation means is generated from the desired substrate surface. Detecting means for detecting a sound wave to be generated, and storing a sound wave generated from the clean substrate surface detected by the detecting means when the pulse laser irradiation means irradiates the clean substrate surface with a pulse laser. Storage means, comparing means for comparing the sound wave detected by the detecting means with the sound wave stored in the storing means, and judging means for judging the state of the substrate surface based on the comparison result by the comparing means. A substrate surface state detecting apparatus using a sound wave, characterized by comprising: 6. The sound wave according to claim 5, wherein the pulsed laser irradiation means is a pulsed laser irradiation means for irradiating the desired substrate surface with a pulsed laser for cleaning the desired substrate surface. Substrate surface condition detector using. 7. The substrate surface state detection device using a sound wave according to claim 5, wherein the desired state of the substrate surface can be determined in air or gas. 8. The method according to claim 5, wherein the comparing means compares the amplitude or frequency spectrum of the sound wave detected by the detecting means with the amplitude or frequency spectrum of the sound wave stored in the storage means. A substrate surface state detecting device using the sound wave according to claim 1.