EP1984125A1

EP1984125A1 - Ultrasound actuator for cleaning objects

Info

Publication number: EP1984125A1
Application number: EP07721911A
Authority: EP
Inventors: Christian Degel; Anette Jakob; Franz Josef Becker
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2006-02-17
Filing date: 2007-02-09
Publication date: 2008-10-29
Also published as: TW200800425A; WO2007093153A1; KR20080098422A; DE102006033372A1; US20090165830A1; JP2009526637A; DE102006033372B4

Abstract

The present invention relates to an ultrasound actuator for cleaning objects, having a propagation volume (3, 4, 13) for ultrasound, on which one or more ultrasonic transducers (5) are arranged. The propagation volume (3, 4, 13) is delimited by an acoustic coupling-out window (8) with a coupling face for acoustically coupling an object (1, 12) to be cleaned and by one or more reflection faces (6, 7) for coupled-in ultrasound. The ultrasonic transducers (5) are arranged on the propagation volume (3, 4, 13) such that the coupled-in ultrasound exits the propagation volume (3, 4, 13) via the coupling-out window (8) only after one or more reflections at the reflection faces (6, 7). The reflection faces are designed such that a predeterminable distribution of the ultrasound energy without intensity peaks results at the coupling-out window (8). The present ultrasound actuator is used to achieve gentle cleaning of the objects with economic use of cleaning liquid.

Description

Ultrasonic actuator for cleaning objects

Technical application

The present invention relates to an ultrasonic actuator for cleaning objects, which has a propagation volume for ultrasound and one or more ultrasonic transducers for coupling ultrasound into the propagation volume.

The cleaning of components plays an essential role in many technical areas. A particular problem is the cleaning of finely structured components, for example of etched wafers from microsystems technology. The increasingly smaller structures mean that particularly small particles pose a major threat to the functionality of the components. The adhesion forces of a surface on a near-surface particle increase sharply with decreasing particle size, so that these particles are very difficult to remove from the surface.

State of the art

Ultrasonic cleaning has been a common method in industrial cleaning technology for a long time. While ultrasonic frequencies in the range of up to 100 kHz are used to clean surfaces of larger particles, ultrasound frequencies in the range of 1 MHz are required for very small particles. The cleaning with these high Ultrasonic frequencies are also known by the term Megaschal1 purification.

Many technical solutions for cleaning components use the so-called immersion technique, in which the components to be cleaned are immersed in a liquid medium into which the ultrasonic waves are coupled. On the one hand, however, this technique suffers from an uneven cleaning action and, on the other hand, requires a large amount of cleaning fluid with the associated costs and problems with regard to environmentally sound disposal. An example of a cleaning system based on the immersion technique is described in EP 0546685 A2. The components to be cleaned are in this case introduced into a tank filled with the cleaning liquid, in which a tubular ultrasound actuator is arranged below the components. In this case, the ultrasonic actuator has a tubular housing, on the inner wall of which ultrasound transducers are mounted in the upper area. The radiation of the ultrasonic waves in the frequency range around 1 MHz takes place through the rohrförτnige housing in the direction of the objects in the tank.

In addition to this dipping technique, other solutions are known in which the ultrasonic actuators are arranged in the immediate vicinity of the components to be cleaned. These applications require only a small amount of cleaning fluid. However, locally very high intensities may occur, which in addition to the desired cleaning effect may also lead to the destruction of the sensitive structures. An example of such a technique can be found in WO 00/21692 A1, which uses a large-area ultrasound transducer in parallel and in the immediate vicinity of the wafer to be cleaned in this case.

Based on this prior art, the object of the present invention is to provide an ultrasonic actuator for cleaning objects, in particular for cleaning components with small structures, which allows gentle cleaning with little use of cleaning fluid.

DESCRIPTION OF THE INVENTION The object is achieved with the ultrasonic actuator according to patent claim 1. Advantageous embodiments of this Ultraschallaktors are the subject of the dependent claims or can be found in the following description and the embodiments.

The present ultrasonic actuator comprises a propagation volume for ultrasound and one or more ultrasound transducers arranged at the propagation volume for coupling ultrasound waves into the propagation volume during operation. The propagation volume is limited by an acoustic coupling-out window with a coupling surface for the acoustic coupling of an object to be cleaned and by one or more reflection surfaces for coupled-in ultrasound. In the present ultrasonic actuator, the one or more ultrasonic transducers are arranged on the propagation volume such that the coupled-in ultrasound does not arrive until after one or more reflections the reflection surfaces via the coupling window from the propagation volume exits. The ultrasonic transducers thus direct the ultrasound not directly to the coupling-out window, but to the one or more reflection surfaces. The one or more reflection surfaces are designed such that a predeterminable distribution of the ultrasound energy without intensity peaks results at the coupling-out window. This may be a uniform distribution or even another predefinable distribution, for example with a maximum in the central region of the coupling-out window for more intensive cleaning of the object in this area.

A uniform distribution may u.U. already be achieved by a multiple reflection on plan reflection surfaces. For a specific spatial or areal distribution of the sound energy at the coupling-out window, the reflection surfaces can also be curved, for example concave.

Preferably, the reflection surfaces are designed for diffuse reflection of the ultrasound during operation of the ultrasound actuator.

This embodiment of the ultrasound actuator with the reflection surfaces, in particular for the diffuse reflection of the ultrasound, achieves a distribution of the sound energy used at the coupling-out window without intensity peaks, for example a uniform distribution. The object to be cleaned is placed in the area of the coupling surface and, if necessary, coupled with a medium. This medium can be a process or cleaning fluid. Of the present ultrasonic actuator, which may be part of a cleaning device for objects, when used for cleaning an object thus requires no or only a small amount of cleaning or coupling liquid.

A cleaning device with the present ultrasonic actuator can, for example, be configured as described in WO 2004/114372 A1, the disclosure content of which with regard to the design of the cleaning device is included in the present patent application. In such an embodiment, the present ultrasonic actuator replaces the second plate with the ultrasonic elements, as can be seen for example in Figures 1 and 2 of WO 2004/114372 Al.

The propagation volume with its boundary surfaces can be designed in different ways. In one embodiment of the present

Ultrasonic actuator, the propagation volume through a solid, for example. From a metal or a ceramic is formed. The reflection surfaces can be obtained by surface structuring of surface areas of the solid.

In another embodiment of the present ultrasonic actuator, the propagation volume is occupied by a gas or a liquid. In this case, the reflection surfaces can be formed by suitably structured or shaped walls made of a solid material. Preferably, at least one of the reflection surfaces is so flexible formed so that it generates constantly changing reflection conditions during operation of the ultrasonic actuator, which lead to a corresponding diffuse reflection of the ultrasound. This can be achieved, for example, by the use of a membrane which is automatically set in motion by the coupled-in ultrasound. Of course, however, other variable, for example. Liquid, boundary surfaces are possible, which provide for correspondingly changing reflection conditions and thus for a changing energy distribution.

In principle, the reflection surfaces in the present ultrasound actuator can be arranged both regularly and randomly distributed around the propagation volume. The decoupling window or its coupling surface is preferably adapted in the present ultrasonic actuator to the shape of the surface of the object to be examined. Furthermore, one or more channels may be formed in the ultrasonic actuator, which open into the coupling surface, so that a liquid coupling or cleaning medium can be introduced via the channels between the coupling surface and the object surface.

The present ultrasonic actuator can be used advantageously for cleaning components with small structures that have to be cleaned by small particles in the size range of 1 μm or less. In this case, ultrasonic transducers are used which emit ultrasound in the wavelength range of> 500 kHz. Of course, the present Ultraschallaktor but also for cleaning of objects that are contaminated with larger particles. In this case, ultrasonic frequencies below 500 kHz are preferably used for the cleaning.

Brief description of the drawings

The present ultrasound actuator will be briefly explained again below with reference to embodiments in conjunction with the drawings without limiting the scope given by the claims protection. Hereby show:

Fig. 1 shows schematically a first example of an embodiment of the present invention

Ultrasonic actuator;

Fig. 2 schematically shows a second example of an embodiment of the present ultrasonic actuator;

3 shows schematically another example of an embodiment of the present ultrasonic actuator;

4 shows an example of a cleaning device with the ultrasonic actuator in a highly schematic representation; such as

Fig. 5 shows schematically an example of the outer

Shape of the ultrasonic actuator. Ways to carry out the invention

FIG. 1 schematically shows a first example of an embodiment of the present ultrasound actuator. The ultrasonic actuator consists in this example of a metal body 3, which forms the propagation volume for ultrasound.

This metal body may, for example, consist of aluminum. In the front area where the object 1 to be cleaned is placed, the metal body 3 has an acoustic coupling-out window 8 whose outer surface, referred to in the present patent application as a coupling surface, is adapted to the shape of the object to be cleaned. In the example of FIG. 1, the object 1 to be cleaned is a sphere, so that the

Coupling surface of the acoustic decoupling window 8 is formed hemispherical. Between the ball and the coupling surface of the coupling-out window 8, a coupling liquid 2 is introduced. This coupling fluid for acoustic coupling can be supplied either from the outside or via a channel 10 optionally provided in the metal body 3, as indicated in FIG.

Furthermore, a plurality of ultrasonic transducers 5 are attached to the metal body 3 in such a way that they do not direct the ultrasound to the coupling-out window 8, but rather to a reflector surface 6 of the metal body 3 formed on the rear side. This reflector surface 6 is formed by structuring the back surface of the

Metal body 3 formed such that the incident ultrasound is diffusely reflected by this reflector surface. The ultrasonic transducers 5 are formed in this example as piezo actuators for a high frequency range (megasonic), which introduce the required sound energy into the metal body 3. The introduced energy is distributed due to the reflections on the reflector surface 6 and other boundary surfaces in the metal body 3 and can only emerge in the region of the coupling window 8 by the production of an acoustically conductive contact, for example by the cleaning or coupling liquid 2, and on the object 1 to be cleaned impinge. Due to the diffuse reflections, a uniform distribution of the energy in the region of the decoupling window and thus a gentle and uniform cleaning of the surface of the object 1 is achieved. The metal body 3 is in this example still embedded in a foam material 11 with flat outer surfaces to facilitate its handling.

Figure 2 shows another example of an ultrasonic actuator according to the present invention, in which a cubic object 1 is to be cleaned. Again, the coupling surface of the acoustic decoupling window 8 is adapted to the shape of the surface of the object 1. In this example, the propagation volume is filled by a gas 4 and is limited in the front region by the coupling-out window 8 and in the rear region by a flexible membrane 7. The remaining boundary walls 9 are made of a plastic material to which the ultrasonic transducers 5 are attached. The reflector surface is formed in this example by the membrane 7, which is set in motion due to the coupling of the ultrasound and thus causes a diffuse reflection of the incident ultrasonic waves due to the constant movement. Even with such a configuration, the coupled-in ultrasonic energy is thus distributed approximately uniformly by the diffuse reflection, so that no intensity peaks occur at the coupling-out window 8.

The ultrasonic actuator can also be used advantageously for the cleaning of disc-shaped objects, as indicated in FIG. The coupling surface of the acoustic decoupling window 8 is executed in this case to adapt to the disc-shaped object 12 plan. Between the object 12 to be cleaned and the coupling surface of the decoupling window 8, a coupling liquid 2 is also conducted in this example, which, for example, can also assume an additional cleaning function as a cleaning fluid. The supply of the coupling fluid 2 via a

Channel 10, which is formed in the propagation volume 13 with the reflection surfaces. In the figure, arranged on the propagation volume 13 ultrasonic transducer 5 are indicated.

4 shows an example of a cleaning device with the ultrasound actuator 16 in a highly schematic representation. The device has a holder 14 for the disc-shaped objects 12 to be cleaned, for example wafers, and a rotary drive 15 for this holder 14. The holder 14 is in this case formed with corresponding not shown in the figure gripping elements. The ultrasonic actuator 16, which is opposite the holder 14, is formed in this example according to FIG. This device allows the rotation of the object 12 to be cleaned during cleaning.

Finally, FIG. 5 schematically shows an example of the external shape of the ultrasound actuator 16 or of the body forming the propagation volume in perspective view, as it can also be used, for example, in the device according to FIG. 4. This polyhedral body has a first 17 and a second surface 18 which are parallel to each other, as well as a plurality of side surfaces 19 which each form an acute angle to the first surface 17. The ultrasonic vibrators are acoustically coupled to the side surfaces 19 of the polyhedral body, which may, for example, be a prismatic stump.

LIST OF REFERENCE NUMBERS

1 obj ect

2 coupling fluid

3 metal bodies

4 gas

5 ultrasonic transducers

6 reflector surface

7 membrane

8 coupling window

9 wall

10 channels

11 foam

12 disc-shaped object

13 Spread volume

14 bracket

15 rotary drive

16 ultrasonic actuator

17 first area

18 second area

19 side surfaces

Claims

claims

1. Ultrasonic actuator for cleaning objects,

- With a propagation volume (3, 4, 13) for ultrasound, of an acoustic coupling-out window (8) with a coupling surface for acoustic coupling of an object to be cleaned (l, 12) and of one or more reflection surfaces (6, 7) for coupled Ultrasound is limited, - and with one or more ultrasonic transducers (5), which are arranged for coupling of ultrasound at the propagation volume (3, 4, 13), that the coupled ultrasound only after one or more reflections at the reflection surfaces (6, 7 ) via the coupling window (8) from the propagation volume (3, 4, 13) emerges,

- Wherein the one or more reflection surfaces (6, 7) are formed such that on

Output window (8) gives a predetermined distribution of the ultrasonic energy without intensity peaks.

2. Ultrasonic actuator according to claim 1, characterized in that the one or more reflection surfaces (6, 7) are designed for a diffuse reflection of the ultrasound.

3. Ultrasonic actuator according to claim 1 or 2, characterized in that the propagation volume (3, 4, 13) is formed by a solid body, of which one or more surface regions are structured to produce the reflection surfaces with diffuse reflection.

4. Ultrasonic actuator according to claim 1 or 2, characterized in that the propagation volume (3, 4, 13) of a liquid or a gas (4) is taken.

5. Ultrasonic actuator according to claim 4, characterized in that at least one of the reflection surfaces (6, 7) is designed so flexible that it generates during operation of the ultrasonic actuator by moving constantly changing reflection conditions.

6. Ultrasonic actuator according to claim 5, characterized in that the at least one reflection surface (6, 7) is a membrane.

7. Ultrasonic actuator according to claim one of claims 1 to 6, characterized in that in the coupling surface of the coupling-out window (8) at least one channel (10) for the supply of a liquid coupling medium (2) opens.

8. Ultrasonic actuator according to claim one of the claims

1 to 7, characterized in that the ultrasonic transducer (5) for generating Ultrasound in the range ≥ 500 kHz are formed.

9. Use of an ultrasonic actuator according to one or more of the preceding claims for cleaning an object (1, 12), wherein the coupling surface is adapted to the shape of the object (1, 12) and between the object (1, 12) and the coupling surface a thin film of a liquid cleaning and / or coupling medium (2) is introduced.

10. A device for cleaning disc-shaped objects (12), which contains an ultrasonic actuator (16) according to one of claims 1 to 8.

A device according to claim 10, comprising a support (14) for a disc-shaped object (12) and a rotary drive (15) connected to the support (14) or the ultrasound actuator (16) for rotation during cleaning To generate relative movement between the disc-shaped object (12) and the ultrasonic actuator (16).