JP3309749B2 - Ultrasonic cleaning equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic cleaning apparatus for irradiating an object to be cleaned in a solution with strong ultrasonic waves for cleaning.

[0002]

2. Description of the Related Art There are two types of devices generally called an ultrasonic cleaning device, one by cavitation and one by flowing water. The former is to remove dirt and the like on the surface of the object to be cleaned by using a powerful shock wave generated by a minute vacuum bubble generated when a strong ultrasonic wave propagates in the cleaning liquid and disappears at a certain moment. . Since cavitation is unlikely to occur at high frequencies, this cleaning method is at most several hundred K
It is performed at a low frequency of less than Hz. On the other hand, the latter type of flowing water type transmits ultrasonic waves having a relatively high frequency of I MHz or higher to a water flow flowing down to the object to be cleaned in a waterfall shape, and applies ultrasonic energy to the surface of the object to be cleaned to remove dirt. It is to be cleaned and removed. This method does not apply a large force to the object to be cleaned unlike the above-described cleaning by cavitation, so that the object to be cleaned is less damaged, and is used for cleaning relatively fine, eg, micrometer-order processed products such as semiconductor wafers. It is suitable.

[0003]

The object to be cleaned can be cleaned by the above-mentioned ultrasonic cleaning apparatus. However, when a large number of objects to be cleaned are accommodated in the cleaning tank and cleaned at the same time, the following is performed. Problems. FIG. 9 shows a state in which a plurality of plate-like objects 5 to be cleaned are housed in a cleaning tank 4 a in a state where they are juxtaposed at appropriate intervals, and are orthogonal to a cleaning surface (wave receiving surface) 8 of the object 5 to be cleaned. The oscillator 9 is arranged. In this case, as shown by the arrow, ultrasonic vibration is generated from the ultrasonic oscillator 9 along the wave receiving surface 8, and both surfaces of the wave receiving surface 8 are simultaneously cleaned. However, in this case, the wave receiving surface 8 of the cleaning object 5 close to the ultrasonic oscillator 9 is cleaned, but the ultrasonic vibration is attenuated as the distance increases, and sufficient vibration energy can be applied to the cleaning object 5. Insufficient cleaning results. Note that this attenuation is stronger as the frequency is higher.

On the other hand, as shown in FIG. 10, an ultrasonic oscillator 9 is disposed on the side surface of the cleaning tank 4a, and when the object 5 to be cleaned disposed in parallel with the ultrasonic oscillator 9 is cleaned, ultrasonic vibration is applied. At a right angle to the cleaning object 5, the applied portion is strongly cleaned. However, the ultrasonic wave which is incident on the object 5 at right angles is reflected by the wave receiving surface 8 and the vibration energy of the ultrasonic vibration transmitted through the object 5 is greatly reduced. Therefore, there is a problem that the object 5 to be cleaned disposed in the vicinity of the ultrasonic oscillator 9 is sufficiently cleaned, but the cleaning of a distant substrate becomes insufficient.

A cleaning apparatus with improved ultrasonic vibration propagation efficiency has been proposed, for example, as disclosed in Japanese Patent Application Laid-Open No. Hei 4-87675. The following is a brief description. FIG. 7 shows the inclination angle θ (°) of the incident direction of the ultrasonic vibration with respect to the normal direction of the wave receiving surface 8 of the object 5 to be cleaned and the transmittance [%] of the ultrasonic vibration energy transmitted through the object 5 to be cleaned. FIG. As shown in the figure, the transmittance becomes extremely large in a certain angle range of the value of θ. That is, in the case of the drawing, the transmittance is about 100 when θ is in the range of about 20 ° to 30 °.
There is a peak value of [%]. Therefore, the inclination angle θ in this range
When the ultrasonic vibration is applied to the object 5 to be cleaned, the vibration energy of the ultrasonic vibration is applied to all the objects 5 to be cleaned sequentially without being attenuated, and sufficient cleaning is performed. In addition,
The specific inclination angle θ is obtained as a function of the plate thickness, the material, the frequency of the incident ultrasonic vibration, the elastic constant of the object to be cleaned and the cleaning liquid, and the like.

FIG. 8 shows an example in which one side surface of the cleaning tank 4b is inclined by an angle θ and an ultrasonic oscillator 9 is fixed to the inclined portion.
A plurality of objects to be cleaned 5 are juxtaposed in the cleaning tank 4b. By setting the inclination angle θ to θ in the peak angle range shown in FIG. 7, the transmittance of the ultrasonic vibration energy to the object 5 to be cleaned is increased, and therefore, for each of the plurality of objects 5 to be cleaned. Sufficient and sufficient cleaning energy is applied by applying sufficient vibration energy from the ultrasonic oscillator 9. However, in this case, there are the following problems. That is, the object to be cleaned 5
The distance between the object and the ultrasonic oscillator 9 is shown in FIG.
, The degree of application of vibration energy to the object to be cleaned 5 is reduced, and the wave receiving surface 8 is not uniformly cleaned. Further, when the size of the object 5 to be cleaned becomes longer, it is necessary to extend the ultrasonic oscillator 9 accordingly, and there is a problem that the distance between the two increases more and more. The angle θ is fixedly set as the inclination angle of one side surface of the cleaning tank 4b, and the shape of the cleaning tank 4b itself changes according to the plate thickness, the material, and the like of the object 5 to be cleaned. It is necessary, very complicated, and requires high equipment costs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to simultaneously and reliably clean a large number of objects to be cleaned by a single cleaning tank, and to perform ultrasonic cleaning at a frequency of several MHz or more. It is an object of the present invention to provide an ultrasonic cleaning apparatus using vibration energy that sufficiently cleans a large wafer, a glass substrate, or the like, and that does not require relatively equipment cost.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an ultrasonic vibrator for generating ultrasonic vibration of wavelength .lambda. In a cleaning tank containing a plate-like object to be cleaned and a cleaning liquid. The direction of propagation of the ultrasonic vibration propagating in the cleaning liquid obliquely intersects the object to be cleaned, and the angle of inclination θ of the wave receiving surface of the object to be cleaned with respect to the normal direction to the surface to be cleaned. In an ultrasonic cleaning apparatus configured to have an angle range in which the transmittance of the vibration energy of the ultrasonic vibration transmitted through the cleaning object is significantly improved, the ultrasonic vibration body is disposed in parallel with the object to be cleaned. And an ultrasonic cleaning apparatus comprising an aggregate of transducers arranged at intervals P satisfying the equation of P = λ / sin θ or P ≦ λ / sin θ. Further, between the transducers arranged at the interval P and a signal supply source for supplying a drive signal to these transducers, an ultrasonic wave generation phase conversion circuit for adjusting the phase of a drive signal input to each transducer is provided. It is characterized by an ultrasonic cleaning device interposed. In addition, an ultrasonic vibrator that generates ultrasonic vibration is disposed in a cleaning tank that stores a plate-shaped object to be cleaned and a cleaning liquid, and a propagation direction of the ultrasonic vibration propagating in the cleaning liquid at a sound speed V is changed. The oblique angle to the object to be cleaned obliquely intersects with the normal direction of the wave receiving surface of the object to be cleaned. The transmittance of the vibration energy of the ultrasonic vibration transmitted through the object to be cleaned is significantly improved. In the ultrasonic cleaning apparatus configured to be in an angular range, the ultrasonic vibrator includes a vibration plate arranged in parallel with the object to be cleaned, and one or more oscillation elements attached thereto, The oscillation element has v = V / si
An elastic leaky wave is excited along the diaphragm at a phase velocity v that satisfies the equation of nθ, thereby applying ultrasonic vibration to the object to be cleaned at the desired inclination angle θ.
Further, the vibration plate is disposed in the cleaning tank, and the object to be cleaned is disposed with the vibration plate interposed therebetween.

According to the first aspect of the present invention, an ultrasonic vibrator for generating ultrasonic vibration of wavelength λ in the cleaning tank uses an array in which a plurality of vibrators are arranged at intervals P. By arranging the transducers at intervals P determined from the equation of P = λ / sin θ based on the total transmission angle θ showing the peak of the transmittance, the Snell of the ultrasonic transducer as an aggregate of these According to the law, an elastic wave of ultrasonic vibration having an angle θ with respect to the normal direction of the wave receiving surface of the object to be cleaned can be applied. While this elastic wave travels in the cleaning tank at an inclination angle θ, the ultrasonic vibrator itself can be arranged parallel to the object to be cleaned, so even if the size of the object to be cleaned becomes longer, the ultrasonic vibration and Becomes constant. Further, when the thickness or material of the object to be cleaned is changed, P = λ / s based on the total transmission angle θ corresponding thereto.
What is necessary is just to change the arrangement of the ultrasonic vibrators at the interval P determined by inθ. Further, as shown in P ≦ λ / sin θ, if the interval between the vibrating elements of the array is formed small and the phase of the electric signal for oscillation applied to each ultrasonic vibrator is relatively adjusted, an arbitrary angle can be obtained. The object to be cleaned can be irradiated with ultrasonic energy with sufficient accuracy. According to the second aspect of the present invention, by providing a diaphragm and an oscillating element attached to the diaphragm on the inner or outer wall of the cleaning tank instead of the ultrasonic vibrator array, v = V / V Exciting a leaky wave having a phase velocity v determined by sin θ, and generating an ultrasonic vibration applied to the object to be cleaned at an angle θ from this leaky wave, as in the case of using the vibrator array described above, and Thorough cleaning is performed. In this case, if the oscillation condition of the oscillation element is changed so that the phase velocity v changes with the change of the angle θ according to the plate thickness or the material of the object to be cleaned, one cleaning device can be used to clean various plate-like articles. Applicable to ultrasonic cleaning.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an ultrasonic cleaning apparatus according to the present invention will be described in detail with reference to the drawings. As shown in FIG. 1 and FIG. 2, a large number of plate-shaped objects 5 to be cleaned are juxtaposed in the cleaning liquid inside the box-shaped cleaning tank 4. A plurality of ultrasonic transducers 1 are arranged in an array at intervals P on one flat side surface of the cleaning tank 4, and constitute an ultrasonic transducer as a whole. The wavelength of the ultrasonic vibration oscillated from each ultrasonic transducer 1 is λ,
Assuming that the electric signals applied to the respective ultrasonic transducers have the same phase, P = λ / sin between the wavelength λ, the interval P, and the angle θ.
The relational expression of θ holds. Is the inclination angle of the ultrasonic vibration with respect to the normal direction of the wave receiving surface of the object 5 to be cleaned. When the inclination angle (incident angle) θ is shown in FIG.
Is set, and P corresponding to this is obtained. The inclination angle θ is theoretically and experimentally obtained as a function of the thickness and material of the object 5 to be cleaned, the frequency of the ultrasonic vibration to be irradiated, and the elastic constants (density, sound velocity, etc.) of the object and the cleaning liquid. And is called the total transmission angle. Actually, the inclination angle θ
Does not need to match exactly the entire transmission angle, and the desired effect can be obtained in a certain angle range.

When the individual ultrasonic transducers 1 are arranged at intervals P as shown in FIGS. 1 and 2 and the ultrasonic transducers 1 are driven, the cleaning tank 4 has a tilt angle θ as shown in FIG. Ultrasonic vibration is generated and vibration energy is applied to the object 5 to be cleaned. Since the energy of the ultrasonic vibration has a transmittance close to 100 [%], the energy is transmitted through each of the cleaning objects 5 without being attenuated, and the entire cleaning of the cleaning object 5 can be performed. Of course, the front and back of the article 5 to be cleaned can be cleaned. When the shape, material, and the like of the article 5 to be cleaned change, the ultrasonic transducer 1 may be arranged with the interval P changed so as to generate a tilt angle θ corresponding to the change. Further, unlike the prior art shown in FIG. 8, the array of the ultrasonic transducers 1 can be arranged in parallel to the wave receiving surface 8 of the object 5 to be cleaned, so that uniform vibration energy is always applied to the object 5 to be cleaned. By applying the voltage to the entire surface, uniform cleaning can be performed.

Each ultrasonic transducer 1 has a frequency f from an original signal supply source (not shown) without passing through a phase conversion circuit.
Since the drive signals are uniformly incident, elastic waves having no phase delay are sent from the respective ultrasonic transducers 1 into the cleaning tank 4. FIGS. 5 and 6 show an example of an embodiment in which the phase of an electric signal applied to each ultrasonic transducer 1 is changed to give a phase shift to the ultrasonic wave sent into the cleaning tank 4. By giving the phase shift, the vibration energy of the elastic wave is applied to the object 5 to be washed in a wavy manner, so that the washing effect is further ensured. Also, if such a phase conversion circuit is used,
By reducing the interval P between the ultrasonic transducers, it is possible to irradiate the ultrasonic wave with high directivity to the intended angle with higher precision at the intended angle.

As shown in FIG. 5, an original signal supply source (not shown)
Sends an original signal of frequency f. An ultrasonic wave generating phase conversion circuit 6 is interposed between the original signal supply source and each of the ultrasonic transducers 1 provided in the cleaning tank 4. The ultrasonic wave generating phase conversion circuit 6 has a function of applying a drive signal to each ultrasonic transducer 1 by causing a phase shift of Δt from the original signal. As shown in FIGS. 5 and 6, the original signal of Δt = 0 is input as it is to the ultrasonic transducer 1 as a drive signal, and the ultrasonic transducer 1 is phase-shifted by Δt ₁ = Δt. A signal is input. Similarly, a drive signal shifted by Δt ₂ = 2Δt and a shift signal Δt ₃ = 3Δt are sent to the ultrasonic vibrator 1.
Of course, Δt ₄ and Δt ₅ are sequentially applied to the ultrasonic vibrator 1 other than the illustrated one.
.. Are input. Note that the phase shift amount Δt is determined by using the arrangement pitch P of the ultrasonic transducers 1 and the sound velocity V of the cleaning liquid as Δt = (P / V) · si
expressed as nθ. As described above, the elastic waves of the ultrasonic vibrations whose phases have been adjusted are emitted from the respective ultrasonic transducers 1 at the inclination angle θ and applied to the object 5 to be cleaned.

FIG. 3 shows another embodiment of the present invention. The cleaning tank 4 of this example uses a side plate having a thickness d as the diaphragm 3. The oscillation element 2 is mounted on the vibration plate 3 and constitutes an ultrasonic vibrator as a whole. Diaphragm 3
When the oscillation element 2 vibrates above, the diaphragm 3 has a phase velocity v
Leakage wave 7 is excited. The leaky wave 7 (for example, a leaky Lamb wave) generates an elastic wave of ultrasonic vibration having an inclination angle θ in the cleaning tank 4. Assuming that the sound speed of the ultrasonic vibration propagating in the cleaning liquid is V, the phase velocity v of the leaky wave is v = V / si
It is determined by nθ. Therefore, the inclination angle θ that makes the transmittance of vibration energy to the object 5 to be cleaned approximately 100 [%].
The oscillation condition of the oscillation element 2 that excites a leaky wave having a desired phase velocity v may be determined according to. With the cleaning apparatus of this embodiment, substantially the same effects as in the previous embodiment can be obtained.

FIG. 4 shows an application example of the embodiment shown in FIG. In this example, a vibration plate 3a is arranged inside the cleaning tank 4, and the oscillation element 2 is connected to the vibration plate 3a. In this case, the cleaning object 5 is disposed on both sides of the diaphragm 3a. Also in the case of this example, a leaky wave 7 is generated on the diaphragm 3a, and elastic waves of ultrasonic vibration are emitted from both sides thereof at an inclination angle θ, so that the objects 5 to be cleaned on both sides can be uniformly cleaned. Here, the diaphragm has a cantilever beam structure with one oscillation element, but by providing another oscillation element on the opposite surface of the diaphragm, more uniform and powerful ultrasonic waves can be applied to the object to be cleaned. Becomes possible.

[0016]

1) According to the ultrasonic cleaning apparatus of the first aspect of the present invention, an interval P = λ / si in an array in the cleaning tank.
By disposing the ultrasonic transducer at nθ, an elastic wave having a transmittance of about 100 [%] is applied to the object to be cleaned at an inclination angle θ,
The surfaces of a large number of objects to be cleaned are surely and sufficiently cleaned. In addition, it is possible to irradiate the object to be cleaned with ultrasonic waves having a frequency of several MHz or more in close proximity to the object to be cleaned,
The degree of cleaning can be improved. 2) According to the ultrasonic cleaning apparatus according to the second and third aspects of the present invention, since the phase of the elastic wave emitted from each ultrasonic transducer is adjusted, reliable cleaning is performed. 3) According to the ultrasonic cleaning apparatus of the fourth aspect of the present invention, the phase velocity v = V / sin θ is applied to the vibrator provided in the cleaning tank.
To excite the leaked wave, and from this leaked wave,
And the inclination angle θ is set near the total transmission angle of the transmittance of about 100 [%], whereby a large number of objects to be cleaned can be surely and sufficiently cleaned. 4) According to the ultrasonic cleaning apparatus of the fifth aspect of the present invention, more uniform and efficient cleaning is performed by directly inserting the vibrator into the cleaning tank.

[Brief description of the drawings]

FIG. 1 is a perspective view showing ultrasonic vibrators arranged in an array on the side surface of a box-shaped cleaning tank.

FIG. 2 is a schematic diagram showing a propagation state of ultrasonic vibration in FIG.

FIG. 3 is a schematic diagram showing a state in which a vibration plate and an oscillation element are provided on a side surface of a cleaning tank to excite leaky waves and propagate ultrasonic vibrations in the tank.

FIG. 4 is a schematic view showing an embodiment in which the diaphragm shown in FIG. 3 is arranged in a cleaning tank;

FIG. 5 is a configuration diagram for converting an original signal having a frequency f into a drive signal phase-shifted to an ultrasonic transducer and inputting the drive signal to each ultrasonic transducer.

FIG. 6 is a waveform chart showing an example of a phase-shifted drive signal in FIG. 5;

FIG. 7 is a diagram showing the relationship between the inclination angle of ultrasonic vibration applied to an object to be cleaned and transmittance.

FIG. 8 is a sectional view showing an example of a conventional cleaning method using an inclination angle θ.

FIG. 9 is a schematic view showing a conventional cleaning method.

FIG. 10 is a schematic view showing a conventional cleaning method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ultrasonic vibrator 2 Oscillating element 3 Vibrating plate 3a Vibrating plate 4 Cleaning tank 5 Object to be cleaned 6 Phase conversion circuit for generating ultrasonic waves 7 Leaky wave 8 Receiving surface 9 Ultrasonic oscillator

Claims (5)

(57) [Claims] 1. An ultrasonic vibrator for generating ultrasonic vibration having a wavelength of λ is disposed in a cleaning tank containing a plate-shaped object to be cleaned and a cleaning liquid, the ultrasonic vibration being transmitted through the cleaning liquid. The propagation direction obliquely intersects the object to be cleaned, and the inclination angle θ to the normal direction of the wave receiving surface of the object to be cleaned is such that the transmittance of the vibration energy of the ultrasonic vibration transmitted through the object to be cleaned is remarkable. In the ultrasonic cleaning apparatus configured to have an improved angle range, the ultrasonic vibrator is a vibrator arranged in parallel with the object to be cleaned and arranged at an interval P satisfying the following relational expression. An ultrasonic cleaning device comprising an aggregate. P = λ / sin θ 2. An ultrasonic vibrator for generating ultrasonic vibration having a wavelength of λ is disposed in a cleaning tank containing a plate-shaped object to be cleaned and a cleaning liquid, the ultrasonic vibration being transmitted through the cleaning liquid. The propagation direction obliquely intersects the object to be cleaned, and the inclination angle θ to the normal direction of the wave receiving surface of the object to be cleaned is such that the transmittance of the vibration energy of the ultrasonic vibration transmitted through the object to be cleaned is remarkable. In the ultrasonic cleaning apparatus configured to have an improved angle range, the ultrasonic vibrator is a vibrator arranged in parallel with the object to be cleaned and arranged at an interval P satisfying the following relational expression. An ultrasonic cleaning device comprising an aggregate. P ≦ λ / sin θ 3. An ultrasonic wave generating phase for adjusting a phase of a drive signal input to each transducer between the transducers arranged at the interval P and a signal supply source for supplying a drive signal to the transducers. The ultrasonic cleaning device according to claim 2, wherein a conversion circuit is interposed. 4. An ultrasonic vibrator for generating ultrasonic vibration is disposed in a cleaning tank containing a plate-shaped object to be cleaned and a cleaning liquid, and the ultrasonic vibration propagating in the cleaning liquid at a sound speed V is provided. The propagation direction obliquely intersects with the object to be cleaned, and the inclination angle θ to the normal direction of the wave receiving surface of the object to be cleaned has a remarkable transmittance of the vibration energy of the ultrasonic vibration transmitted through the object to be cleaned. In an ultrasonic cleaning apparatus configured to be in an improved angle range, the ultrasonic vibrator includes a vibration plate disposed in parallel with the object to be cleaned, and one or more oscillation elements attached thereto. And the oscillation element comprises:
An ultrasonic wave is excited along the diaphragm at a phase velocity v that satisfies the following relational expression, whereby ultrasonic vibration is applied to the object to be cleaned at the desired inclination angle θ. Cleaning equipment. v = V / sin θ 5. The ultrasonic cleaning apparatus according to claim 4, wherein the vibration plate is disposed in the cleaning tank, and the object to be cleaned is disposed across the vibration plate.