JP2009125645A - Ultrasonic washing device and ultrasonic washing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tank type ultrasonic washing device which cannot be influenced by properties of the bending mode and the like peculiar to a vibrator and which is capable of controlling the non-uniformity of washing in the surface to be washed even if when a plurality of sheets of vibration elements are fitted to the washing tank as a vibrator, and to provide an ultrasonic washing method. <P>SOLUTION: The ultrasonic washing device 10 for conducting the ultrasonic washing by immersing the material to be washed W in the washing liquid is provided with a washing tank 15 which is filled with a washing liquid 4 to wash the material to be washed, two vibrators 11, 12 to transmit the ultrasonic vibration to the washing liquid and an ultrasonic generators 16, 17 to apply high frequency voltage to the vibrators. The ultrasonic washing device 10 is characterized by washing the material to be washed by transferring the cavitation area generated within the washing liquid by sweeping the frequency of at least one of the vibrators among the two vibrators. Also the ultrasonic washing method utilizing the same is provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ultrasonic cleaning apparatus and an ultrasonic cleaning method for immersing an object to be cleaned such as a semiconductor wafer in a cleaning liquid and applying a ultrasonic vibration to the cleaning liquid to perform a cleaning process.

  In manufacturing a semiconductor element, if each substrate has particles or the like attached to it in each process of manufacturing a semiconductor silicon wafer or the like to be a substrate, uniform processing is not performed on the substrate surface, and indirect from such a substrate. In other words, cross-contamination is caused, resulting in a decrease in the yield of wafer manufacturing. Therefore, before processing a normal substrate, particles and the like are removed by cleaning the substrate with a cleaning device.

  Cleaning devices for cleaning precision substrates such as semiconductor substrates and glass substrates for liquid crystal displays can be broadly divided into two types: batch processing that processes multiple substrates simultaneously and single wafer processing that processes substrates one by one. is there. Furthermore, in order to improve the cleaning power in these two types of apparatuses, an ultrasonic cleaning method that applies ultrasonic vibration with a frequency of 500 kHz or more to the cleaning liquid may be employed (for example, Patent Documents 1 to 3 and the like). reference).

  In the batch type ultrasonic cleaning apparatus, the tank type is the mainstream. In this tank type ultrasonic cleaning apparatus, for example, a substrate is immersed in a cleaning tank filled with a cleaning liquid, and ultrasonic vibration is applied to the cleaning tank from a piezoelectric vibrator provided at the bottom of the tank, thereby cleaning an object to be cleaned. Can be washed. When a high frequency voltage is applied to the piezoelectric vibrator, ultrasonic vibration unique to the piezoelectric vibrator is generated. The ultrasonic vibration propagates to the cleaning liquid in the cleaning tank, so that cavitation occurs in the cleaning liquid, and the cleaning process with higher cleaning power can be performed by this cavitation. In addition to the cavitation, the ultrasonic cleaning action includes a particle acceleration, a straight flow, and a chemical action cleaning action.

  In such a tank-type ultrasonic cleaning apparatus, the size of the cleaning tank is increasing with the recent increase in diameter of wafers. When applying ultrasonic vibration to the cleaning liquid stored in a large-capacity cleaning tank, many vibration elements are bonded to the radiation plate in units of several to several tens of sheets. However, in-plane sound pressure unevenness has occurred due to a decrease in sound pressure at the joint between the piezoelectric vibration elements and the bending mode of each piezoelectric vibration element itself. For this reason, there is a problem that the sound pressure of the entire cleaning tank becomes non-uniform and uneven cleaning occurs. In addition, since the frequency of sound waves is increasing, it is difficult to make the sound field (vibration) uniform in the ultrasonic cleaning apparatus.

JP 2007-216209 A JP 2003-24889 A JP-A-11-156314

  The present invention has been made in view of the above problems, and the object of the present invention is not influenced by characteristics such as a bending mode unique to a vibrator in a tank-type cleaning apparatus, and a plurality of vibration elements. It is an object of the present invention to provide an ultrasonic cleaning apparatus and an ultrasonic cleaning method capable of suppressing uneven cleaning within a surface to be cleaned even when the is attached to a cleaning tank as a vibrator.

In order to achieve the above object, the present invention provides at least a cleaning tank filled with a cleaning liquid for cleaning an object to be cleaned, a plurality of vibrators for propagating ultrasonic vibrations in the cleaning liquid, and a high frequency for the vibrator. In an ultrasonic cleaning apparatus comprising an ultrasonic oscillator for applying a voltage and performing ultrasonic cleaning by immersing the object to be cleaned in the cleaning liquid,
The object to be cleaned is cleaned by moving a cavitation region generated in the cleaning liquid by sweeping a frequency of at least one of the plurality of oscillators. An ultrasonic cleaning apparatus is provided (claim 1).

Further, the present invention provides an ultrasonic vibration to the cleaning liquid by immersing an object to be cleaned in a cleaning liquid filled in the cleaning tank and applying a high frequency voltage from an ultrasonic oscillator to a plurality of vibrators arranged in the cleaning tank. In the method of ultrasonically cleaning the object to be cleaned by propagating cavitation in the cleaning liquid,
When the cavitation is generated, the object to be cleaned is cleaned by moving the cavitation region generated in the cleaning liquid by sweeping the frequency of at least one of the plurality of vibrators. An ultrasonic cleaning method is provided (claim 5).

  Thus, the so-called tank-type ultrasonic cleaning apparatus and ultrasonic cleaning method of the present invention sweeps the frequency of at least one of a plurality of vibrators to generate cavitation generated in the cleaning liquid. Since the region is moved, a cleaning effect by cavitation can be uniformly imparted to the object to be cleaned within the surface to be cleaned, and cleaning unevenness can be suppressed.

  In this case, it is preferable that the plurality of vibrators are arranged in the cleaning tank so that their vibration surfaces are orthogonal to the surface to be cleaned of the object to be cleaned (Claim 2). It is preferable that the vibrator is arranged in the cleaning tank so that the vibration surface thereof is orthogonal to the surface to be cleaned of the object to be cleaned.

  In this way, by arranging the plurality of vibrators in the cleaning tank so that the vibration surfaces of the plurality of vibrators and the surfaces to be cleaned are orthogonal to each other, the vibration surfaces propagated to the cleaning liquid and the objects to be cleaned are arranged. Since the surfaces to be cleaned are not parallel to each other and the vibration propagated to the cleaning liquid can be prevented from colliding with the surface to be cleaned, the cavitation generated by the propagated ultrasonic vibration is easily moved in the cleaning tank.

  In the present invention, it is preferable that the plurality of vibrators include at least a first vibrator capable of fixing a frequency and a second vibrator capable of sweeping the frequency (Claim 3). Preferably, the vibrator includes at least a first vibrator and a second vibrator, and when the cavitation is generated, the frequency of the first vibrator is fixed and the frequency of the second vibrator is swept ( Claim 7).

  As described above, the plurality of vibrators include the first vibrator capable of fixing the frequency and the second vibrator capable of sweeping the frequency, and the frequency of the first vibrator when the cavitation is generated. Is fixed and the frequency of the second vibrator is swept, the cavitation generation region can be easily controlled only by operating the frequency of the second vibrator.

  In this case, the plurality of vibrators include a third vibrator that is disposed opposite to the second vibrator with the cleaning tank interposed therebetween and that can sweep the frequency, and the second and third vibrators. The vibrators can alternately sweep each frequency at a predetermined cycle (Claim 4), and the plurality of vibrators sandwich the second vibrator and the cleaning tank. It is preferable that when the cavitation is generated, the frequencies of the second and third vibrators are alternately swept in a predetermined cycle when the cavitation is generated. ).

  As described above, if the frequency is alternately swept at a predetermined cycle by the two vibrators arranged opposite to each other with the frequency being swept, the cavitation can be moved to a wider range of the cleaning liquid. The object to be cleaned can be efficiently and effectively cleaned.

  In the ultrasonic cleaning apparatus and the ultrasonic cleaning method of the present invention, in the tank type cleaning apparatus, the cleaning tank is not affected by the characteristics such as the bending mode unique to the vibrator, and a plurality of vibration elements are used as the vibrator. Even if it is attached to the cleaning surface, uneven cleaning within the surface to be cleaned can be suppressed.

Conventionally, in ultrasonic cleaning, the entire cleaning tank is caused by the sound pressure unevenness in the surface due to the bending mode etc. of the piezoelectric vibrator, the sound pressure drop at the joint of the piezoelectric vibration element and the piezoelectric vibration element attached to one surface with a large area, etc. There was a concern that the sound pressure of the water would become uneven, causing cleaning unevenness. As a countermeasure against this, the present inventors used a uniform acoustic transducer such as a composite transducer that can generate uniform acoustic waves. However, when uniform acoustic waves are generated in the tank, cavitation, which is a main factor in cleaning, is used. The problem of becoming difficult to occur has occurred.
In the piezoelectric vibrator, due to the bending mode or the like of the piezoelectric vibrator, a portion where the sound wave is focused in the tank is created, energy is concentrated on the portion, and cavitation is likely to occur. However, in the uniform sound wave vibrator, it becomes difficult to form a portion where the sound wave is focused, and cavitation is difficult to occur.

  Therefore, the present inventors have conducted intensive research to solve such problems. For example, a vibrator is attached to the bottom surface of the cleaning tank, and a similar vibrator is provided on one side surface of the cleaning tank to generate ultrasonic waves from the side surface. Then, the ultrasonic wave from the bottom surface and the ultrasonic wave from the side surface interfere with each other in the cleaning tank, and a place where cavitation is likely to occur is formed. However, this only causes local cavitation, resulting in uneven cleaning. For example, by fixing the frequency of one vibrator and sweeping (sweeping) the frequency of the other vibrator within a certain range. Then, a place where cavitation is likely to occur is moved like a wiper. The inventors have conceived that the surface of a silicon wafer or the like can be cleaned uniformly by utilizing this phenomenon, and the present invention has been completed.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings, but the present invention is not limited thereto.
First, a first embodiment of an ultrasonic cleaning apparatus according to the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a first embodiment of an ultrasonic cleaning apparatus according to the present invention.
The ultrasonic cleaning apparatus 10 of the present invention is to perform ultrasonic cleaning by immersing an object to be cleaned W in a cleaning liquid 4, and includes a cleaning tank 15, two vibrators 11 and 12, and two ultrasonic waves. And oscillators 16 and 17.

The cleaning tank 15 is filled with a cleaning liquid 4 for cleaning an object to be cleaned, for example, the substrate W. The cleaning tank 15 includes radiation plates 19 a and 19 b for propagating the ultrasonic vibration of the vibrator to the cleaning liquid 4, and includes two vibrators, that is, the first vibrator 11 and the second vibrator 12. Are joined to the radiation plates 19a and 19b, respectively. Further, the first vibrator 11 and the second vibrator 12 are driven by applying a high-frequency voltage by the first ultrasonic oscillator 16 and the second ultrasonic oscillator 17, respectively. Thereby, ultrasonic vibration is propagated to the cleaning liquid 4 by the first vibrator 11 and the second vibrator 12.
At this time, of the two vibrators, the second vibrator 12 can sweep the frequency, and is generated in the cleaning liquid 4 by sweeping the frequency of the second vibrator 12. The substrate W is cleaned by moving the cavitation region.

  For example, as illustrated in FIG. 1, the first vibrator 11 is attached to the bottom surface of the cleaning tank 15, and the second vibrator 12 is attached to the left side surface of the cleaning tank 15. However, the arrangement of the vibrators can be changed as appropriate. Regarding the arrangement of the vibrators, for example, the arrangements of the second embodiment and the third embodiment described below can be used.

  Thus, in the so-called tank-type ultrasonic cleaning apparatus 10 of the present invention, the cavitation region generated in the cleaning liquid is moved by sweeping the frequency of at least one of the two vibrators. Therefore, a cleaning effect by cavitation can be uniformly imparted to the object to be cleaned within the surface to be cleaned, and uneven cleaning can be suppressed.

Therefore, in the conventional tank type cleaning apparatus, when a piezoelectric vibrator is used as a vibrator, there is a problem that cavitation is localized due to the bending mode unique to the vibrator, and cleaning unevenness occurs. In the cleaning apparatus, since the cavitation can be intentionally generated and moved locally, the problem of uneven cleaning is solved. In addition, in the present invention, even if a large cleaning tank is used and a plurality of vibrating elements are attached as a single vibrator to a single radiation plate provided in the cleaning tank, the sound pressure of the entire cleaning tank is low. Although it is in a uniform state, cavitation can be intentionally generated locally and moved, so that uneven cleaning of the object to be cleaned can be suppressed.
Further, conventionally, when a single uniform sound wave vibrator is used as a vibrator for the purpose of uniform sound pressure, there is a problem that it becomes difficult to generate a portion where the sound wave is focused and cavitation is difficult to occur. However, in the present invention, even if a uniform sound wave vibrator is used as the vibrator, vibrations caused by a plurality of vibrators interfere with each other, so that cavitation is likely to occur.

  On the other hand, in the present invention, materials of the radiation plates 19a and 19b to which the first and second vibrators 11 and 12 are joined include stainless steel, tantalum, quartz, and the like. However, the present invention is not limited to these, and can be appropriately selected according to the type of the substrate W to be cleaned. For example, when the object to be cleaned is a silicon wafer, it is more preferable that the material of the surface of the radiation plate in contact with the cleaning liquid is quartz, because metal contamination by the radiation plate can be prevented.

Moreover, it is preferable that the two vibrators 11 and 12 are arranged in the cleaning tank 15 so that their vibration surfaces are orthogonal to the surface to be cleaned of the substrate W as shown in FIG.
As described above, the two vibrators 11 and 12 are disposed in the cleaning tank 15 so that the vibration surfaces of the two vibrators 11 and 12 are orthogonal to the surface to be cleaned of the substrate W. And the surface to be cleaned of the substrate W is not parallel. Therefore, since the vibration propagated to the cleaning liquid 4 can be prevented from colliding with the surface to be cleaned, the cavitation generated by the propagated ultrasonic vibration is easily moved in the cleaning tank.
Furthermore, since the ultrasonic vibration propagated to the cleaning liquid 4 can be prevented from directly colliding with the surface to be cleaned of the substrate W, the occurrence of damage to the surface to be cleaned can be alleviated particularly for a silicon wafer that is easily damaged. Can do.

In the first embodiment, it is sufficient that at least one of the first vibrator 11 and the second vibrator 12 is frequency sweepable, but even if both vibrators can control the frequency sweep. Good.
In particular, in the present invention, among the plurality of vibrators, the first vibrator 11 can fix the frequency, and the second vibrator 12 can sweep the frequency.

  As described above, since the two vibrators 11 and 12 include the first vibrator 11 that can fix the frequency and the second vibrator 12 that can sweep the frequency, when the cavitation is generated, If the frequency of the second vibrator is fixed and the frequency of the second vibrator is swept, the cavitation generation region can be easily controlled only by operating the frequency of the second vibrator. In particular, when a vibrator is driven at a high frequency in MHz, the cavitation generation region moves greatly even if there is a subtle difference in frequency, so that the frequency is swept by fixing the frequency of one vibrator. The frequency adjustment of the vibrator becomes easy.

Next, a second embodiment of the ultrasonic cleaning apparatus of the present invention will be described with reference to FIG.
FIG. 2 is a diagram showing a second embodiment of the ultrasonic cleaning apparatus according to the present invention.
This form differs from the first embodiment particularly in the number and arrangement of vibrators.
The ultrasonic cleaning apparatus 20 according to the second embodiment of the present invention performs ultrasonic cleaning by immersing the substrate W in the cleaning liquid 4, and includes a cleaning tank 25, three vibrators 21, 22, 23, and the like. Three ultrasonic oscillators 26, 27, and 28 are provided.

  The cleaning tank 25 is filled with the cleaning liquid 4 and includes radiation plates 29a, 29b, and 29c for propagating the ultrasonic vibration of the vibrator to the cleaning liquid 4. Three vibrators, that is, the first vibrator 21, the second vibrator 22, and the third vibrator 23 are joined to the radiation plates 29a, 29b, and 29c, respectively. The first, second, and third vibrators 21, 22, and 23 are applied with a high-frequency voltage by a first ultrasonic oscillator 26, a second ultrasonic oscillator 27, and a third ultrasonic oscillator 28, respectively. Drive. Thereby, ultrasonic vibration propagates to the cleaning liquid 4 by the three vibrators 21, 22, and 23.

Regarding the three vibrators 21, 22, and 23, the first vibrator 21 can fix the frequency, and the second vibrator 22 and the third vibrator 23 can sweep the frequency. The arrangement is preferably as shown in FIG.
That is, the first vibrator 21 capable of fixing the frequency is disposed on the bottom surface of the cleaning tank 25. The second vibrator 22 capable of sweeping the frequency is disposed on the left side surface of the cleaning tank 25 in FIG. The third vibrator 23 capable of sweeping the frequency is disposed opposite to the second vibrator 22 with the cleaning tank 25 interposed therebetween.

Further, when the three vibrators are joined to the respective radiation plates so that the three vibrators are arranged around the cleaning tank as shown in FIG. 2, the second vibrator 22 and the third vibrator 23 have the frequency It is preferable that the sweeping is alternately performed at a predetermined cycle.
As described above, if the second vibrator 22 and the third vibrator 23 are arranged opposite to each other with the cleaning tank 25 interposed therebetween and frequency sweeping can be alternately performed at a predetermined cycle, cavitation in a wider range of the cleaning liquid 4 can be achieved. The ultrasonic cleaning apparatus can be moved efficiently, and the object to be cleaned can be cleaned efficiently and effectively.

  At this time, it is more preferable that the surface to be cleaned of the substrate W, which is the object to be cleaned, and the vibration main surfaces of the three vibrators are orthogonal to each other as shown in FIG. Thus, if the propagation direction of the vibration is parallel to the surface to be cleaned of the substrate, the cavitation generated by the transmitted ultrasonic vibration is easy to move in the cleaning tank, and the It is possible to suppress the acoustic vibration from directly colliding with the surface to be cleaned of the substrate W. For this reason, it is possible to alleviate the occurrence of damage to the surface to be cleaned, and to clean the surface to be cleaned uniformly, particularly for a silicon wafer that is easily damaged.

Next, a third embodiment of the ultrasonic cleaning apparatus of the present invention will be described with reference to FIG.
FIG. 3 is a diagram showing a third embodiment of the ultrasonic cleaning apparatus according to the present invention.
This form differs from the second embodiment particularly in the arrangement of the vibrators.
The ultrasonic cleaning apparatus 30 according to the third embodiment of the present invention is for ultrasonic cleaning by immersing the substrate W in the cleaning liquid 4, and includes a cleaning tank 35, three vibrators 31, 32, 33, Three ultrasonic oscillators 36, 37, and 38 are provided.

Of the three vibrators 31, 32, and 33, the first vibrator 31 can fix the frequency, and the second vibrator 32 and the third vibrator 33 can sweep the frequency. The arrangement can be as shown in FIG.
That is, the first vibrator 31 capable of fixing the frequency is disposed so as to float on the upper surface of the cleaning tank 35, that is, the cleaning liquid 4. The second vibrator 32 capable of sweeping the frequency is disposed on the left side surface of the cleaning tank 35 in FIG. The third vibrator 33 capable of sweeping the frequency can be disposed opposite to the second vibrator 32 with the cleaning tank 35 interposed therebetween.

At this time, when the three vibrators are joined to the respective radiation plates so as to be arranged around the cleaning tank as in the third embodiment, the second vibrator 32 and the third vibrator 33 is preferably one that alternately sweeps the frequency at a predetermined cycle.
As described above, if the second vibrator 32 and the third vibrator 33 are arranged to face each other with the cleaning tank 35 interposed therebetween, and the frequency sweep can be alternately performed at a predetermined cycle, the cavitation is further performed in a wider range of the cleaning liquid 4. The ultrasonic cleaning apparatus can be moved efficiently, and the object to be cleaned can be cleaned efficiently and effectively.

  As in the second embodiment, it is more preferable that the surface to be cleaned of the substrate W, which is the object to be cleaned, and the vibration main surfaces of the three vibrators are orthogonal to each other as shown in FIG. . Thus, if the propagation direction of the vibration is parallel to the surface to be cleaned of the substrate, the cavitation generated by the transmitted ultrasonic vibration is easy to move in the cleaning tank, and the It is possible to suppress the acoustic vibration from directly colliding with the surface to be cleaned of the substrate W. For this reason, it is possible to alleviate the occurrence of damage to the surface to be cleaned, and to clean the surface to be cleaned uniformly, particularly for a silicon wafer that is easily damaged.

  As in the example of the above embodiment, in the ultrasonic cleaning apparatus of the present invention, the vibrator to be used is generated in the cleaning liquid by sweeping the frequency of at least one of the vibrators. There is no particular limitation even if it is a piezoelectric vibrator having a unique bending mode or a uniform acoustic wave vibrator.

Further, the arrangement and material of the vibrator are not particularly limited. In the first embodiment, the two vibrators are attached to the bottom surface and the left side surface of the cleaning tank 15, but the two vibrators may be disposed opposite to each other with the cleaning tank interposed therebetween. In addition, it may be the upper surface + the right side surface.
Furthermore, although the case of a rectangular parallelepiped was demonstrated as a shape of a washing tank, a cylindrical shape may be sufficient and this is not specifically limited, either. For example, the bottom surface of the cleaning tank can be V-shaped, and two vibrators can be arranged on the V-shaped bottom surface.
In the present invention, the “vibration plane” of the vibrator means a plane perpendicular to the vibration direction at the center of the vibrator, and in a normally used piezoelectric vibrator, a radiation plate or the like is used. It is the surface to be joined.

A method of cleaning the substrate W, which is an object to be cleaned, using the ultrasonic cleaning apparatus 10 of the present invention described in the first embodiment will be described with reference to FIG.
First, the cleaning liquid 4 is stored in the cleaning tank 15 included in the ultrasonic cleaning device 10. At this time, the cleaning liquid 4 to be added can be appropriately selected according to the purpose of cleaning and the object to be cleaned. For example, functional water such as pure water, concentration-controlled dissolved N ₂ water, or dissolved CO ₂ water, chemical liquid, etc. Can be used.
In particular, if functional water is used as the cleaning liquid, cavitation is likely to occur, and a higher cleaning effect can be expected.

Next, a plurality of substrates W arranged in parallel to a wafer carrier (not shown) are immersed in the cleaning liquid 4. Subsequently, a high frequency voltage is applied to the two vibrators 11 and 12 disposed in the cleaning tank 15 from the two ultrasonic oscillators 16 and 17, and ultrasonic vibration is applied to the cleaning liquid 4 via the radiation plates 19a and 19b. Propagation causes cavitation in the cleaning liquid 4.
When the cavitation is generated, the cavitation region generated in the cleaning liquid 4 is moved by sweeping the frequency of the second vibrator 12 out of the two vibrators 11 and 12.

  Thus, in the so-called tank-type ultrasonic cleaning apparatus 10 of the present invention, the cavitation region generated in the cleaning liquid is moved by sweeping the frequency of at least one of the two vibrators. Therefore, a cleaning effect by cavitation can be uniformly imparted to the object to be cleaned within the surface to be cleaned, and uneven cleaning can be suppressed.

  Accordingly, in contrast to the problem that cavitation is localized and cleaning unevenness is generated, the ultrasonic cleaning method of the present invention intentionally generates and moves cavitation locally, thereby eliminating the problem of cleaning unevenness. In addition, in the present invention, even if a large cleaning tank is used and a plurality of vibrating elements are attached as a single vibrator to a single radiation plate provided in the cleaning tank, the sound pressure of the entire cleaning tank is low. Although it is in a uniform state, since cavitation is intentionally generated and moved locally, cleaning unevenness of the object to be cleaned can be suppressed.

Further, as shown in FIG. 1, since the vibration surfaces of the two vibrators 11 and 12 are arranged in the cleaning tank 4 so as to be orthogonal to the surface to be cleaned of the substrate W, the vibration surface and the substrate propagated to the cleaning liquid 4 W surface to be cleaned is not parallel. Therefore, since the vibration propagated to the cleaning liquid 4 can be prevented from colliding with the surface to be cleaned, the cavitation generated by the propagated ultrasonic vibration is easily moved in the cleaning tank. Therefore, uniform cleaning can be performed within the surface.
Furthermore, since the ultrasonic vibration propagated to the cleaning liquid 4 can be prevented from directly colliding with the surface to be cleaned of the substrate W, damage to the surface to be cleaned can be alleviated particularly for a silicon wafer that is easily damaged. .

In the present invention, the first vibrator 11 and the second vibrator 12 may perform frequency sweeping in at least one, but the frequency sweep may be controlled in both vibrators.
In particular, among the plurality of vibrators, for example, the frequency of the first vibrator 11 is fixed to about 730 kHz, and the frequency of the second vibrator 12 is swept at about 729 to 731 kHz (730 ± 1 kHz). preferable.

  Thus, when the cavitation is generated, if the frequency of the first vibrator is fixed and the frequency of the second vibrator is swept, the cavitation generation region can be simplified simply by operating the frequency of the second vibrator. Can be controlled. In particular, when a vibrator is driven at a high frequency in MHz, the cavitation generation region moves greatly even if there is a subtle difference in frequency, so that the frequency is swept by fixing the frequency of one vibrator. The frequency adjustment of the vibrator becomes easy.

Next, a method for cleaning the substrate W as an object to be cleaned using the ultrasonic cleaning apparatus 20 according to the second embodiment of the present invention will be described.
First, the cleaning liquid 4 is stored in the cleaning tank 25 included in the ultrasonic cleaning device 20. At this time, as the cleaning liquid 4 to be added, as described above, functional water such as pure water, dissolved N ₂ water whose concentration is controlled, or dissolved CO ₂ water, a chemical solution, or the like can be used.
In particular, if functional water is used as the cleaning liquid, cavitation is likely to occur, and a higher cleaning effect can be expected.

Next, a plurality of substrates W arranged in parallel to a wafer carrier (not shown) are immersed in the cleaning liquid 4. Subsequently, a high frequency voltage is applied from three ultrasonic oscillators 26, 27, 28 to the three vibrators 21, 22, 23 arranged in the cleaning tank 25, and the cleaning liquid is passed through the radiation plates 29a, 29b, 29c. The ultrasonic vibration is propagated to 4 to generate cavitation in the cleaning liquid 4.
When generating cavitation, the frequency of the first vibrator 21 among the three vibrators 21, 22, and 23 is fixed to, for example, about 730 kHz, and the second and third are arranged opposite to each other with the cleaning tank 4 interposed therebetween. The cavitation regions generated in the cleaning liquid 4 are alternately moved by alternately sweeping the frequencies of the vibrators 22 and 23 at predetermined intervals, for example, at intervals of 5 seconds. At this time, the frequency sweep can be performed between about 729 to 731 kHz.

  As described above, the second vibrator 22 and the third vibrator 23 are arranged opposite to each other with the cleaning tank 25 interposed therebetween, and if the frequency sweep is alternately performed at a predetermined cycle, the cavitation is moved in a wider range of the cleaning liquid 4. The object to be cleaned can be cleaned efficiently and effectively.

  At this time, it is more preferable that the surface to be cleaned of the substrate W, which is the object to be cleaned, and the vibration main surfaces of the three vibrators are orthogonal to each other as shown in FIG. In this way, if the propagation direction of vibration is parallel to the surface to be cleaned of the substrate, the cavitation generated by the propagated ultrasonic vibration can easily move in the cleaning tank, and the object to be cleaned can be cleaned evenly. it can. In addition, it is possible to suppress the ultrasonic vibration propagated to the cleaning liquid 4 from directly colliding with the surface to be cleaned of the substrate W. Therefore, it is possible to alleviate the occurrence of damage to the surface to be cleaned, particularly for silicon wafers that are easily damaged.

  Finally, the ultrasonic cleaning device 30 according to the third embodiment of the present invention is different from the ultrasonic cleaning device 20 according to the second embodiment only in the arrangement of the first vibrator. The method of cleaning the substrate W when using the ultrasonic cleaning apparatus 30 of the embodiment can be substantially the same as the ultrasonic cleaning method using the ultrasonic cleaning apparatus 20 of the second embodiment.

The present invention will be described in more detail below with reference to examples of the present invention, but these examples do not limit the present invention.
(Example)
The ultrasonic cleaning apparatus 10 introduced in the first embodiment of the present invention was used to observe the cavitation generation region.
Detailed specifications of the used ultrasonic cleaning apparatus 10 and a cavitation generation method using the same are as follows.

The first ultrasonic transducer 11 and the second ultrasonic transducer 12 are provided on the bottom surface and the left side surface of the rectangular parallelepiped cleaning tank 15, the frequency of the bottom surface is fixed to 30 kHz, and the frequency of the side surface is 729 to 731 kHz. Swept with the width of. The state of cavitation generation at that time was observed with a cavitation emission observation device (not shown) (see FIG. 4).
FIG. 4 is a diagram observing the cavitation generation region. When the frequency of the first vibrator is fixed at 730 kHz, the frequency of the second vibrator is 729 kHz, (b) is 730 kHz, and (c) is This is a case of controlling to 731 kHz.

  Note that the cavitation emission observation device (not shown) is a device capable of visualizing weak light emitted when cavitation occurs, such as an image intensifier, and its peripheral devices (CCD camera, video storage device). Etc.). According to this, strong light is observed in a portion where a lot of cavitation occurs.

  As a result of observation, when the frequency of one vibrator was fixed and the frequency of the vibrator arranged perpendicular to it was swept, it was confirmed that the light streak caused by cavitation moved like a wiper (FIG. 4 ( a) to (c)). This is presumably because a lot of cavitation occurs in the portion where the amplitude is strengthened by the mutual interference of the sound waves, and the portion moves by sweeping one frequency.

  The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical idea of the invention.

1 is a diagram showing a first embodiment of an ultrasonic cleaning apparatus according to the present invention. It is a figure which shows 2nd Embodiment of the ultrasonic cleaning apparatus which concerns on this invention. It is a figure which shows 3rd Embodiment of the ultrasonic cleaning apparatus which concerns on this invention. It is the figure which observed the generation | occurrence | production area | region of the cavitation in an Example, When it fixes with the frequency of 730 kHz of a 1st vibrator, the frequency of a 2nd vibrator is (729), (b) is 730 kHz, (c) is This is a case of controlling to 731 kHz.

Explanation of symbols

4 ... cleaning solution, 10, 20, 30 ... ultrasonic cleaning device,
11, 21, 31 ... first vibrator, 12, 22, 32 ... second vibrator,
23, 33 ... third vibrator, 15, 25, 35 ... cleaning tank,
16, 26, 36 ... 1st ultrasonic oscillator, 17, 27, 37 ... 2nd ultrasonic oscillator,
19a, 19b, 29a, 29b, 29c ... radiation plate,
28, 38 ... third ultrasonic oscillator, W ... object to be cleaned (substrate).

Claims (8)

At least a cleaning tank filled with a cleaning liquid for cleaning an object to be cleaned, a plurality of vibrators for propagating ultrasonic vibrations to the cleaning liquid, and an ultrasonic oscillator for applying a high frequency voltage to the vibrators. In the ultrasonic cleaning apparatus for ultrasonic cleaning by immersing the object to be cleaned in the cleaning liquid,
The object to be cleaned is cleaned by moving a cavitation region generated in the cleaning liquid by sweeping a frequency of at least one of the plurality of oscillators. Ultrasonic cleaning device.   2. The ultrasonic cleaning apparatus according to claim 1, wherein the plurality of vibrators are arranged in the cleaning tank so that vibration surfaces thereof are orthogonal to a surface to be cleaned of the object to be cleaned. .   The ultrasonic cleaning according to claim 1 or 2, wherein the plurality of vibrators include a first vibrator capable of fixing at least a frequency and a second vibrator capable of sweeping the frequency. apparatus.   The plurality of vibrators include a third vibrator that is disposed opposite to the second vibrator with the cleaning tank interposed therebetween and capable of sweeping a frequency, and the second and third vibrators are 4. The ultrasonic cleaning apparatus according to claim 3, wherein sweeping of each frequency is alternately performed at a predetermined cycle. An object to be cleaned is immersed in a cleaning liquid filled in a cleaning tank, and a high frequency voltage is applied from an ultrasonic oscillator to a plurality of vibrators disposed in the cleaning tank to propagate ultrasonic vibrations to the cleaning liquid. In the method of ultrasonically cleaning the object to be cleaned by generating cavitation inside,
When the cavitation is generated, the object to be cleaned is cleaned by moving the cavitation region generated in the cleaning liquid by sweeping the frequency of at least one of the plurality of vibrators. Ultrasonic cleaning method characterized by.   The ultrasonic cleaning method according to claim 5, wherein the plurality of vibrators are arranged in the cleaning tank so that vibration surfaces thereof are orthogonal to a surface to be cleaned of the object to be cleaned.   The plurality of vibrators include at least first and second vibrators, and when the cavitation is generated, the frequency of the first vibrator is fixed and the frequency of the second vibrator is swept. The ultrasonic cleaning method according to claim 5, wherein the method is ultrasonic cleaning.   The plurality of vibrators include a third vibrator that is disposed opposite to the second vibrator with the cleaning tank interposed therebetween and capable of sweeping a frequency. When the cavitation is generated, the second and third vibrators are provided. The ultrasonic cleaning method according to claim 7, wherein the frequency of the vibrator is alternately swept in a predetermined cycle.

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