JP4813961B2 - Ultrasonic sound pressure measuring device - Google Patents

Description

  The present invention relates to cleaning of semiconductor wafers, glass masks, liquid crystal glass substrates, hard disk boards and the like by ultrasonic vibration, and more particularly to ultrasonic sound pressure measurement of ultrasonic vibration.

A high-frequency ultrasonic cleaning apparatus is used for precision cleaning of precision processed products such as semiconductor wafers, liquid crystal glass, and hard disk boards.
The dirt that is subject to precision cleaning is adhered particles of 1 μm or less, and the dirt is peeled off by the ultrasonic vibration transmitted through the cleaning liquid filled in the cleaning tank or the synergistic effect of the cleaning liquid and ultrasonic vibration. Is.
Every year, as represented by semiconductor wafers and glass for liquid crystals, the size of the object to be cleaned increases, and the circuit pattern becomes finer and high density circuits are formed. There has been an increasing demand for a cleaning apparatus that can perform uniform and high-precision cleaning that does not cause uneven cleaning even in a cleaning apparatus incorporated in the manufacturing process of glass for liquid crystals.
Therefore, ultrasonic sound pressure measurement is widely used as a method for investigating the cleaning effect of an ultrasonic cleaning apparatus capable of performing high-precision cleaning and for evaluating the performance of the cleaning apparatus itself. Conventionally, a portable ultrasonic sound pressure meter that displays instantaneous and instantaneous ultrasonic sound pressure on a display using voltage or the like has been used. The sound pressure detection probe provided in such an ultrasonic sound pressure meter has a deviation due to the ultrasonic frequency and the ambient temperature, and the indicator is an average value indication, so it cannot follow a sharp change in the ultrasonic sound pressure. In general, the absolute value of ultrasonic sound pressure cannot be measured.
2. Description of the Related Art In recent ultrasonic cleaning apparatuses for precision cleaning of semiconductors and the like, there has been a demand for a measuring instrument that requires ultrasonic sound pressure measurement using an SI unit system and that can perform quality evaluation based on time-lapse data.

FIG. 4 is a cross-sectional perspective view showing a state of cleaning of a cleaning object and a state of ultrasonic sound pressure measurement by an ultrasonic cleaning apparatus that cleans an object to be cleaned that has been enlarged using a conventional ultrasonic vibrator.
A cleaning liquid injection hole 13 having a slit shape which is a hole for spraying the ultrasonic cleaning liquid is formed on the lower surface of the cleaning liquid reservoir 11.
The jet cleaning liquid 14 accompanied by ultrasonic vibration is jetted from the cleaning liquid jet holes 13 (slits) onto the cleaning surface of the object 17 to remove the adhered foreign matter. The cleaning liquid is supplied into the cleaning liquid reservoir 11 by applying a predetermined liquid pressure from the cleaning liquid supply port 15.
Therefore, for example, in the case of a large cleaning object such as glass for liquid crystal, the entire surface of the cleaning object is cleaned while moving the object 17 to be cleaned in the direction of the arrow (X; perpendicular to the slit direction).
In the ultrasonic sound pressure measurement, the cleaning liquid sprayed from the sound pressure detection probe 21 of the portable ultrasonic sound pressure meter 20 is used instead of the cleaning object 17 in order to measure the ultrasonic sound pressure of the spray cleaning liquid 14 sprayed from the slit 13. 14, the ultrasonic sound pressure is detected while moving in the direction of the slit 13 and moving in the direction intersecting the slit 13. The detection current of the sound pressure sensor (piezoelectric element) included in the sound pressure detection probe 21 is input to the portable ultrasonic sound pressure meter 20, where it is displayed on a voltage value (Vrms) indicator and visually read as a sound pressure value. In this way, the change of the sound pressure on the entire surface of the slit 13 is recognized by reading the indicator.
Conventionally, when the ultrasonic sound pressure unevenness occurs in the cleaning portion, this is regarded as a change amount of the voltage value (Vrms). Since the voltage value (Vrms) is an average value display, it cannot follow a rapid and steep change.
FIG. 5 is a measurement position vs. sound pressure characteristic diagram measured by a conventional ultrasonic sound pressure measurement device. Although not shown in the figure, an ultrasonic sound pressure difference due to frequency and an ultrasonic sound pressure difference due to temperature are generated.

  As a measure to improve the above ultrasonic sound pressure measurement, it has sound pressure sensor means, measures the ultrasonic sound pressure value from the voltage value, calculates the frequency of the ultrasonic sound pressure waveform, and corresponds to this frequency There is an ultrasonic sound pressure measurement device that corrects an ultrasonic sound pressure value using a correction coefficient to display the corrected ultrasonic sound pressure value. (For example, refer to Patent Document 1).

Japanese Patent Laying-Open No. 2004-251845 (page 7, FIG. 1)

Every year, microfabricated products such as semiconductor wafers and liquid crystal glass, which are objects to be cleaned, are becoming larger in size and circuits, and there is a need for improved precision cleaning. Ultra-sound in the production line equipped with multiple ultrasonic cleaning devices of the same type as dirt particles such as fine particles due to non-uniformity of ultrasonic sound pressure due to sonic vibration, thorough removal of dirt, increase in size, and circuit miniaturization. The difference is that the difference in cleaning characteristics between sonic cleaning devices becomes non-negligible, and it is the same that causes more uniform ultrasonic vibrations and no difference in characteristics between the devices. There has been a demand for an ultrasonic cleaning apparatus having accuracy.
Along with the improvement in accuracy of ultrasonic cleaning devices, there has been a demand for higher accuracy in measuring devices that characterize the ultrasonic cleaning devices.
The sound pressure detection probe used in the ultrasonic sound pressure measurement device uses a piezoelectric element as a sensor built in the sound pressure detection probe. This piezoelectric element detects a sound pressure, and the ultrasonic sound pressure is converted and extracted as a change amount of voltage (current). Piezoelectric elements originally have frequency characteristics and temperature characteristics, and there is a problem that sensor sensitivity varies depending on the measurement environment.
Further, in an ultrasonic cleaning apparatus, cleaning is usually performed by irradiating a liquid such as pure water and other cleaning liquid with ultrasonic waves. When measuring the ultrasonic sound pressure in this liquid, the detection value of the ultrasonic sound pressure value varies greatly depending on the flow of the liquid, the reflection of ultrasonic waves on the liquid surface and the inner wall of the device, etc. There was a problem that it was difficult to express as a characteristic value of pressure.

  An object of the present invention is to solve the above-mentioned problems of the prior art, an ultrasonic sound pressure measuring device capable of performing measurement representing the absolute value of ultrasonic sound pressure and displaying the measured value of ultrasonic sound pressure. Is to provide.

In order to achieve this object, the ultrasonic sound pressure measuring device of the present invention is an ultrasonic sound device for measuring the sound pressure in a cleaning liquid of ultrasonic vibration irradiated from an ultrasonic vibration plate provided in the ultrasonic cleaning device. A pressure measuring device,
A sound pressure detection probe;
Voltage detection means having the detected voltage value detected by the sound pressure detection probe as input, displaying the detected voltage value, and having a communication interface terminal with a personal computer;
A personal computer that outputs the voltage measurement means and predetermined parameter information is input via the communication interface terminal, and performs necessary calculations, display, and recording;
A temperature sensor that detects the temperature of the tip of the sound pressure detection probe as temperature information;
A controller that receives the frequency information of the ultrasonic vibration of the ultrasonic cleaning device and the temperature information detected by the temperature sensor as the predetermined parameter information, converts the communication interface, and transmits the converted information to the personal computer. ,
The personal computer has a parameter table of frequency sensitivity of the sound pressure detection probe in a desired range of the frequency information of the ultrasonic vibration, and a parameter table of temperature sensitivity of the sound pressure detection probe in a desired range of the temperature of the tip of the probe; , And the voltage value / Pascal value conversion table are stored in advance in the memory,
By using the plurality of parameter tables to perform correction and conversion calculation processing on the input ultrasonic sound pressure voltage value, the frequency sensitivity and temperature sensitivity of the sound pressure probe at the time of sound pressure measurement are obtained. The ultrasonic sound pressure measurement value in absolute value units that does not cause an error due to the sound pressure detection probe is output accurately with a peak value and an average value corresponding to the distance in the moving direction of the sound pressure detection probe , and is displayed. .
Further, the voltage measuring means is an oscilloscope or a high frequency voltmeter.
Furthermore, the personal computer is configured to record temporal changes in the ultrasonic sound pressure measurement values and analyze the changes within a predetermined time by a statistical method.

By carrying out the present invention, since the sensitivity of the sound pressure detection probe varies depending on various conditions at the time of measurement, an ultrasonic sound pressure value in absolute value units can be obtained by correcting this sensitivity. In addition, since the time lapse of the ultrasonic sound pressure value can be calculated statistically, the ultrasonic sound pressure can be identified as a distribution, so that the ultrasonic cleaning device can be measured with high accuracy and reliability. As a specific index that can be evaluated highly, the measurement position resolution about 7 times that of the conventional measurement position is obtained from the ultrasonic sound pressure distribution characteristic diagram in FIG. 2, and the frequency measurement accuracy is shown in FIG. An improvement of about three times that of the prior art was obtained, and a special effect of higher accuracy was obtained.

FIG. 1 is a system diagram of an ultrasonic sound pressure measuring apparatus according to the present invention.
Reference numeral 1 denotes a sound pressure detection probe, and an ultrasonic composite piezoelectric element is used for a sensor built in the probe. This ultrasonic composite piezoelectric element detects an ultrasonic sound pressure, and the ultrasonic sound pressure is converted and taken out as a change amount of voltage (current). Although not shown, it has a moving mechanism for moving the sound pressure detection probe, and can move the slit surface of the ultrasonic cleaning apparatus throughout.
Reference numeral 2 denotes a voltage measuring means, for example, an oscilloscope or a high-frequency voltmeter, which receives the voltage (Vp-p) detected by the ultrasonic composite piezoelectric element 1 and displays the change amount of this voltage as an ultrasonic sound pressure waveform. At the same time, an ultrasonic sound pressure signal is output via the GPIB interface.
3 is a personal computer, and the voltage (Vp-p) value indicating the ultrasonic sound pressure waveform output from the oscilloscope is input via the GPIB (communication) interface, and the inner wall shape information of the ultrasonic cleaning device is keyed in. The ultrasonic sound pressure data calculated and processed by the correction processing program, the absolute value conversion program, and the statistical processing program is stored and displayed.
Reference numeral 4 denotes a controller which inputs temperature information from the temperature sensor and frequency information from the excitation power source of the ultrasonic cleaning apparatus, converts this into a GPIB interface signal and transmits it to the personal computer. Here, power control of the ultrasonic sound pressure measuring device and the ultrasonic cleaning device may be performed.
Reference numeral 5 denotes a temperature sensor, which is added near the sound pressure sensor mounted on the sound pressure detection probe 1 and outputs temperature information.
The ultrasonic sound pressure measuring device of the present invention is provided with a moving mechanism for moving the ultrasonic sound pressure detecting probe 1, the oscilloscope 2, the personal computer 3, the controller 4, the temperature sensor 5, and the sound pressure detecting probe. .
10 is a jet type ultrasonic cleaning device, 11 is a cleaning liquid reservoir, 12 is an ultrasonic vibrator, 13 is a cleaning liquid injection hole (slit), 14 is a cleaning liquid, 15 is a cleaning liquid supply port, 16 is a high frequency excitation power source, and 17 is a target. It is a washed product.
The jet ultrasonic cleaning apparatus 10 is provided in a cleaning liquid reservoir 11 having a cleaning liquid injection hole (slit) 13 and a cleaning liquid supply port 15 which are holes for injecting the spray cleaning liquid 14, and in the cleaning liquid reservoir 11. The ultrasonic vibration body 12 is configured to be excited at a frequency near 1 MHz by a high-frequency excitation power source 16 for propagating ultrasonic waves.
In actual cleaning, the spray cleaning liquid 14 that is irradiated from the ultrasonic vibration plate and sprayed from the slit 13 with ultrasonic vibration flows out toward the cleaning object 17 that moves in the X direction, and cleaning is performed to remove adhered foreign matters. To do.

An outline of the operation of the system of the ultrasonic sound pressure measuring apparatus according to the embodiment of the present invention will be described.
First, a normal cleaning operation in the ultrasonic cleaning apparatus 10 will be described. A cleaning liquid to which water pressure is applied is supplied from the cleaning liquid supply port 15 , the cleaning liquid is stored in the cleaning liquid reservoir 11, and a vibration plate that resonates vibrations oscillated by the ultrasonic vibration element forming the ultrasonic vibrator 12. The ultrasonic vibration is propagated to the cleaning liquid, and the pressurized jet cleaning liquid 14 accompanied by the ultrasonic vibration is jetted from the slit 13, and this jet cleaning liquid is radiated to the cleaning surface of the object 17 to be cleaned. The object 17 is cleaned in a slit shape, and the object 17 is cleaned in the X direction (perpendicular to the slit direction) so that the object 17 is cleaned with respect to the surface. This is an operation of cleaning all over and removing adhering foreign matter.
Next, the operation of ultrasonic sound pressure measurement of the ultrasonic sound pressure measurement apparatus of the present invention will be described.
In the ultrasonic sound pressure measurement, in order to measure the ultrasonic sound pressure of the spray cleaning liquid 14 sprayed from the slit 13, the sound pressure detection probe 1 in which an ultrasonic composite piezoelectric element or the like is incorporated is used instead of the cleaning object 17. The ultrasonic sound pressure is detected while moving in the direction of the slit 13 and the direction crossing the slit 13 while being applied to the spray cleaning liquid 14 to be applied .
A detection current (voltage) of a sound pressure sensor (such as an ultrasonic composite piezoelectric element) included in the sound pressure detection probe 1 is input to an oscilloscope 2, where an ultrasonic sound pressure waveform is displayed with an indication value of a voltage value (Vp-p). Then, it can be visually read as a change amount of the ultrasonic sound pressure value from the ultrasonic sound pressure waveform. At the same time, an ultrasonic sound pressure waveform signal representing the ultrasonic sound pressure waveform with the indicated value of the voltage value (Vp-p) is output from the GPIB interface of the oscilloscope 2 and input to the personal computer.
The personal computer converts the sound pressure value of the ultrasonic vibration in a desired range of the ultrasonic vibration frequency into a frequency (frequency sensitivity of the sound pressure detection probe) parameter table, and the sound of the ultrasonic vibration in the desired range of the probe tip temperature. The pressure value is a temperature (temperature sensitivity of the sound pressure detection probe) parameter table, and if necessary, the sound pressure value of ultrasonic vibration in the desired shape type of the inner wall shape of the ultrasonic cleaning device is changed to the inner wall shape parameter table. Each table converted to a Pascal value conversion table is stored in advance in a memory, and by using each table, a calculation process for correction and conversion is performed on the voltage value of the input ultrasonic sound pressure. An ultrasonic sound pressure measurement value in absolute value units that does not cause an error due to the frequency sensitivity of the sound pressure probe at the time of measurement or temperature sensitivity is obtained and output and displayed accurately.
Various correction processes such as correction by temperature parameter table and temperature information, correction by frequency parameter table and frequency information, correction by tank reflection by inner wall shape parameter table and inner wall shape information, and correction by water pressure by processing operation of correction processing program I do.
Next, the absolute value for converting the corrected ultrasonic sound pressure waveform signal from the voltage value (Vp-p) to the ultrasonic sound pressure value (SI unit kPa; pressure Pascal) by the processing operation of the absolute value conversion program. Calculations are made and stored and displayed.
Further, statistical processing is calculated by using the ultrasonic sound pressure data, which is the time-series absolute value stored in the memory, by the processing operation of the statistical processing program, and the result is stored and displayed.
In the correction processing program, how the ultrasonic sound pressure detected by the sound pressure detection probe changes with respect to the frequency change and temperature change of the ultrasonic vibration, this is used as correction data, and the frequency parameter is calibrated in advance. Four tables (tables) including a table, a temperature parameter table, an inner wall shape parameter table, and a voltage / pascal conversion table are provided for correction and conversion.
In this way, the ultrasonic sound pressure can be measured in the absolute value unit of the pressure in the ultrasonic cleaning liquid ejected from the slit 13, and the distribution of the sound pressure over the entire slit shape is recognized on the display or print of a personal computer. The cleaning characteristics of the ultrasonic cleaning apparatus 10 are evaluated with high accuracy.

FIG. 2 is an ultrasonic sound pressure distribution characteristic diagram of the ultrasonic sound pressure measuring apparatus of the present invention.
The horizontal axis represents the measurement position (unit: mm) and is the distance in the moving direction (Y) of the ultrasonic sound pressure detection probe 1. An exemplary measurement position is from the start (0 mm) to the end point (110 mm), and is the distance in the length direction of the slit 13 of the ultrasonic cleaning device 10.
The vertical axis represents the measured ultrasonic sound pressure value (unit: kPa), which is a value measured as the absolute value of the ultrasonic sound pressure.
The ultrasonic sound pressure distribution characteristic curve obtained from the ultrasonic sound pressure measuring apparatus of the present invention includes an A characteristic curve indicated by a solid line and a B characteristic curve indicated by a dotted line.
The A characteristic curve is a characteristic curve obtained by obtaining an instantaneous maximum value (peak detection) of the ultrasonic sound pressure so that a rapid change in the ultrasonic sound pressure can be captured. From this A characteristic curve, it is possible to evaluate a position where the ultrasonic sound pressure of the ultrasonic cleaning apparatus 10 to be measured instantaneously decreases and causes the ultrasonic sound pressure unevenness, and the ultrasonic sound pressure increases instantaneously. A position that damages the object to be cleaned can be evaluated. The A characteristic curve was displayed and printed out from a personal computer as a result of temperature and frequency correction processing and absolute value conversion processing for converting the ultrasonic sound pressure voltage value to the ultrasonic sound pressure Pascal pressure value. Is.
The B characteristic curve is a characteristic curve obtained by obtaining the average value of the ultrasonic sound pressure so that the average value resulting in a relatively slow change in the ultrasonic sound pressure can be captured. From this B characteristic curve, it is possible to evaluate by conceptually grasping the ultrasonic sound pressure distribution state of the entire ultrasonic sound pressure measurement position of the ultrasonic cleaning apparatus 10 as the measurement object. Although not shown, statistical quantities such as grasping the standard deviation and grasping the position where the ultrasonic sound pressure value deviates from the upper limit specified value / lower limit specified value are obtained, and the quality and reliability are evaluated. The B characteristic curve is displayed and printed from a personal computer as a result of temperature and frequency correction processing, absolute value conversion processing that converts the voltage value of ultrasonic sound pressure into Pascal pressure value of ultrasonic sound pressure, and statistical processing. Is the output.
Both the A characteristic curve and the B characteristic curve are not shown by repeating the measurement by changing the measurement position while moving the sound pressure detection probe 1 slightly in the X-axis direction and again moving in the Y-axis direction. It is also possible to obtain a three-dimensional ultrasonic sound pressure distribution characteristic diagram. Thereby, an ultrasonic sound pressure distribution characteristic diagram of the entire surface of the cleaning liquid ejected from the slit 13 is displayed.

FIG. 3 is a frequency characteristic diagram of ultrasonic sound pressure of the ultrasonic sound pressure measuring apparatus of the present invention.
The C characteristic curve in FIG. 3 is a direct ultrasonic sound pressure versus frequency characteristic in units of mV measured and displayed by the oscilloscope 2 when the output of the sound pressure detection probe 1 is input to the oscilloscope 2. It can be seen that the frequency value fluctuates greatly compared to the reference value p. The variation q for each frequency is prepared in advance as a frequency parameter table (frequency correction table).
The D characteristic curve in FIG. 3 is an actually measured ultrasonic sound pressure (unit: kPa) -frequency characteristic curve corrected by the frequency correction table. It is shown that the value is substantially along the reference value p.
Although not shown in the drawing, the fluctuation with respect to the temperature of the sound pressure detection probe 1 is also provided in advance as a temperature correction table.
Although not shown, a temperature parameter table and an inner wall shape parameter table are obtained in the same manner.

  The present invention can be mainly used in manufacturing industries that require precision cleaning in a production line for precision processed products such as semiconductor wafers, glass masks, liquid crystal glass substrates, and hard disk boards.

1 is a system diagram of an ultrasonic sound pressure measuring apparatus according to the present invention. It is an ultrasonic sound pressure distribution characteristic figure of the ultrasonic sound pressure measuring device of the present invention. It is a frequency characteristic figure of the ultrasonic sound pressure of the ultrasonic sound pressure measuring device of the present invention. It is a system block diagram of the conventional ultrasonic sound pressure measuring device. It is a measurement position versus sound pressure characteristic figure measured with the conventional ultrasonic sound pressure measuring device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 21 Sound pressure detection probe 2 Oscilloscope 3 Personal computer 4 Controller 5 Temperature sensor 10 Injection type ultrasonic cleaning apparatus 11 Cleaning liquid reservoir 12 Ultrasonic vibrator 13 Cleaning liquid injection hole (slit)
14 Injected cleaning liquid 15 Cleaning liquid supply port 16 High frequency excitation power supply 17 Object to be cleaned 20 Ultrasonic sound pressure gauge

Claims (3)

An ultrasonic sound pressure measuring device for measuring the sound pressure in a cleaning liquid of ultrasonic vibration irradiated from an ultrasonic vibration plate provided in the ultrasonic cleaning device,
A sound pressure detection probe;
Voltage measuring means for receiving the detected voltage value detected by the sound pressure detecting probe; and
A personal computer that performs necessary calculations, display and recording from the output of the voltage measuring means and predetermined parameter information;
A temperature sensor that detects the temperature of the tip of the sound pressure detection probe as temperature information;
A controller for transmitting the frequency information of the ultrasonic vibration of the ultrasonic cleaning device and the temperature information detected by the temperature sensor to the personal computer as the predetermined parameter information,
The personal computer performs a calculation process of correction and conversion on the voltage value of the input ultrasonic sound pressure, thereby converting the ultrasonic sound pressure measurement value in absolute value units in the moving direction of the sound pressure detection probe. An ultrasonic sound pressure measuring device that displays a peak value and an average value according to the frequency .   The ultrasonic sound pressure measuring apparatus according to claim 1, wherein the voltage measuring means is an oscilloscope or a high-frequency voltmeter.   The ultrasonic sound pressure measurement according to claim 1 or 2, wherein the personal computer is configured to record a temporal change of the ultrasonic sound pressure measurement value and analyze a change within a predetermined time by a statistical method. apparatus.

Images