Cleaning system and method for operating a cleaning system

Abstract

Cleaning system (10) comprising at least one nozzle (18) for conveying a cleaning fluid, at least one piezoelectric element for converting an electrical signal into mechanical vibrations and at least one signal generator (12) for generating the electrical signal, wherein the signal is transmitted to the piezoelectric element and the mechanical vibrations generated by the piezoelectric element are introduced into the cleaning fluid, wherein the at least one piezoelectric element is arranged in the at least one nozzle (18) and wherein the signal generator (12) has means for impedance detection in order to detect and monitor an electrical impedance of the piezoelectric element, in particular during the operation of the cleaning system.

Description

[0001] The invention relates to a cleaning system comprising at least one nozzle for passing a cleaning fluid, at least one piezoelectric element for converting an electrical signal into mechanical vibrations, and at least one signal generator for generating the electrical signal, wherein the signal is transmitted to the piezoelectric element and the mechanical vibrations generated by the piezoelectric element are introduced into the cleaning fluid. The invention also relates to a method for operating a cleaning system.

[0002] Cleaning systems with nozzles for passing a cleaning fluid, which is set into mechanical vibrations by means of piezoelectric elements, are used, among other things, for cleaning semiconductor components. A problem with such systems is that the aging of the piezoelectric elements can only be detected by an inadequate cleaning result. Another problem is that the piezoelectric elements can be damaged during dry running, i.e., when no cleaning fluid is passed through the nozzles.

[0003] The invention aims to improve a cleaning system and a method for operating a cleaning system.

[0004] According to the invention, a cleaning system with the features of claim 1 and a method for operating a cleaning system with the features of claim 5 are provided. Advantageous embodiments of the invention are described in the dependent claims.

[0005] A cleaning system according to the invention comprises at least one nozzle for passing a cleaning fluid through it, at least one piezoelectric element for converting an electrical signal into mechanical vibrations, and at least one signal generator for generating the electrical signal. The signal is transmitted from the signal generator to the piezoelectric element, and the mechanical vibrations generated by the piezoelectric element are introduced into the cleaning fluid. The at least one piezoelectric element is arranged in the at least one nozzle, and the signal generator includes means for impedance detection in order to detect and monitor the electrical impedance of the piezoelectric element, particularly during operation of the cleaning system.

[0006] The invention is based on the understanding that the impedance of a piezoelectric element changes when contact between the piezoelectric element and the cleaning fluid is lost. Furthermore, the invention is based on the understanding that the impedance of a piezoelectric element changes as it ages. Therefore, the cleaning system according to the invention makes it possible to detect both dry running of the piezoelectric element in the nozzle and aging of the piezoelectric element by measuring its electrical impedance. The impedance of the piezoelectric element can be measured either only during operation of the cleaning system and / or also outside of operation, for example, during a test run.The cleaning system according to the invention therefore makes it possible to detect dry running of the piezoelectric element and thus prevent damage to the piezoelectric element. This is because, when a change in the impedance of the piezoelectric element indicates that it is no longer in contact with the cleaning fluid or that only a thin layer of cleaning fluid is still wetting the piezoelectric element, the electrical signal supplied to the piezoelectric element is immediately switched off. Aging of the piezoelectric element can be detected by a change in its impedance.Therefore, if, for example, the impedance of the piezoelectric element approaches a predefined maximum or minimum value, the piezoelectric element can be replaced as a precautionary measure to prevent a defect during operation of the cleaning system. The cleaning system according to the invention thus enables predictive maintenance and assessment of the piezoelectric elements. This prevents the failure of the cleaning system's piezoelectric element during operation. Since, for example, semiconductor components are manufactured in highly automated production facilities, the cleaning system according to the invention can largely prevent interruptions to such automated production due to a defect in the cleaning system's piezoelectric element.

[0007] In a further development of the invention, the signal generator is designed to generate electrical signals in a frequency range from 400 kHz to 10 MHz.

[0008] Such a frequency range allows for the fulfillment of a wide variety of cleaning tasks, and in particular, even very fine structures of semiconductor components can be reliably cleaned.

[0009] In a further development of the invention, at least two nozzles are provided, wherein the central longitudinal axes of the nozzles are arranged at an angle to each other, so that cleaning fluid exiting the nozzles meets each other at a distance from the nozzles.

[0010] In this way, jets of cleaning fluid emerging from two or more nozzles can be directed onto a small area of ​​a component to be cleaned.

[0011] In a further development of the invention, the piezoelectric element arranged in the first nozzle receives a first electrical signal with a principal component of a first frequency, and the piezoelectric element arranged in the second nozzle receives a second electrical signal with a principal component of a second frequency that differs from or is the same as the first frequency.

[0012] In this way, cleaning fluid oscillating at different frequencies can be applied to the same area of ​​a component being cleaned. Alternatively, cleaning fluid can be applied from two nozzles, with the fluid from the first and second nozzles oscillating at the same frequency. The application from the first nozzle can be at a different angle than the application from the second nozzle, regardless of the frequency at which the cleaning fluid from the first and second nozzles oscillates. By using different frequencies and / or different angles of impact of the cleaning fluid, structures with very different dimensions within the area to be cleaned can be reliably cleaned.

[0013] The problem underlying the invention is also solved by a method for operating a cleaning system according to the invention, in which the detection of an impedance of the at least one piezoelectric element is provided at least during the operation of the cleaning device.

[0014] In a further development of the invention, the comparison of the measured impedance with a predefined target impedance or with predefined maximum and minimum values ​​for the impedance is provided.

[0015] In a further development of the invention, it is provided to determine an aging state of the at least one piezoelectric element, in particular by determining a gradient of the detected electrical impedance and / or by comparing a detected impedance with at least one predefined impedance value.

[0016] Further features and advantages of the invention will become apparent from the claims and the following description of a preferred embodiment of the invention in conjunction with the drawings. The drawings show: Fig. 1 a section-by-section view of a cleaning system according to the invention, Fig. 2 a first side view of the nozzle unit of the cleaning system of the Fig. 1 , Fig. 3 a second side view of the nozzle unit of the cleaning system of the Fig. 1 and Fig. 4 further views of the nozzle unit of the cleaning system of the Fig. 1 from different perspectives.

[0017] Fig. 1 Figure 1 shows a cleaning system 10 according to the invention, comprising a signal generator 12, a so-called matching box 14 for impedance matching, and a nozzle unit 16. The nozzle unit 16 has two nozzle tips 18, 20, from which cleaning fluid emerges during operation of the cleaning system 10. Cleaning fluid is supplied to the nozzle unit 16 via two cleaning fluid lines (not shown), which are located in Fig. 1 indicated by two arrows 22, 24.

[0018] Cleaning fluid is supplied to the first nozzle 18 via the cleaning fluid line indicated by arrow 22. Cleaning fluid is supplied to the second nozzle 20 via the cleaning fluid line indicated by arrow 24.

[0019] Each of the two nozzles 18, 20 is equipped with a Fig. 1 The nozzles are equipped with an invisible piezoelectric element. This piezoelectric element can be set into vibration by means of an electrical signal. The first nozzle 18 is equipped with a piezoelectric element that can vibrate at a frequency of 1 MHz, whereas the second nozzle 20 is equipped with a piezoelectric element that can vibrate at a frequency of 3 MHz. The cleaning fluid passed through nozzles 18 and 20 is set into vibration by means of the respective piezoelectric element. Thus, after exiting the first nozzle 18, the emerging fluid vibrates at a frequency of 1 MHz, and the cleaning fluid emerging from the second nozzle 20 vibrates at a frequency of 3 MHz.

[0020] It is in Fig. 1 It can be seen that the central longitudinal axes of the two nozzles 18, 20 are at an angle to each other and are oriented such that, viewed in the direction of flow, the central longitudinal axes intersect after the respective outlet opening. The cleaning fluid exiting the first nozzle 18 thus meets the cleaning fluid exiting the second nozzle 20. Advantageously, a component 26 to be cleaned, which is in Fig. 1 The nozzle 18, shown only schematically, is located at the intersection of the two central longitudinal axes. Cleaning fluid oscillating at a frequency of 1 MHz, as well as cleaning fluid oscillating at a frequency of 3 MHz, thus impacts the component 26. This allows for the reliable cleaning of structures of varying sizes or widths on the component 26, which could, for example, be a semiconductor device. The cleaning fluid from nozzle 18 impacts the component 26 at a different angle than the cleaning fluid from nozzle 20.

[0021] To excite the piezoelectric elements in nozzles 18 and 20 to mechanical vibrations, an electrical signal is required for each. The piezoelectric element in the first nozzle 18 must be supplied with an electrical signal having a main component with a frequency of 1 MHz. The piezoelectric element in the second nozzle 20 must be supplied with an electrical signal having a main component with a frequency of 3 MHz. These two electrical signals are supplied to the nozzle unit 16 via a high-frequency line 28, which runs from the matching box 14 to the nozzle unit 16. The two electrical signals are generated in the signal generator 12. A first high-frequency line 30 runs from the signal generator 12 to the matching box 14 and is intended for the first electrical signal with a frequency of 1 MHz.A second high-frequency line 32 leads from the signal generator 12 to the matching box 14 and is intended for the second electrical signal with a frequency of 3 MHz. In the matching box 14, impedance matching takes place between the nozzle unit 16 and the signal generator 12 in order to transfer as much of the electrical power generated by the signal generator 12 as possible to the piezoelectric elements in the nozzles 18, 20 of the nozzle unit 16.

[0022] The two electrical signals can be transmitted from the matching box 14 to the nozzle unit 16 via a single high-frequency line 28, but separate high-frequency lines can of course also be used for this purpose within the scope of the invention.

[0023] The signal generator 12 includes means for impedance detection. These means for impedance detection are configured to detect the electrical impedance of the piezoelectric elements in the nozzles 18, 20.

[0024] The inventors have discovered that the electrical impedance of a piezoelectric element changes depending on whether or not the piezoelectric element is in contact with a cleaning fluid. By detecting the impedance using the signal generator 12, it is possible to determine whether cleaning fluid is being passed through nozzle 18 and nozzle 20, or whether the piezoelectric elements in nozzles 18 and 20 are running dry. The signal generator 12 is designed to detect the impedance of the piezoelectric element in the first nozzle 18 and the impedance of the piezoelectric element in nozzle 20 separately.

[0025] Running a piezoelectric element dry can lead to damage or complete destruction of the piezoelectric element. Therefore, if the impedance detection means in the signal generator 12 detect that no more cleaning fluid is being delivered to nozzle 18 and / or nozzle 20, the signal generator 12 can immediately stop the transmission of either the first or the second electrical signal. This prevents damage to the piezoelectric elements in nozzles 18 and 20.

[0026] According to the inventors, measuring the electrical impedance of the piezoelectric elements in the nozzles 18 and 20 can also be used to detect the aging of these elements. As piezoelectric elements age, their electrical impedance changes. Using the signal generator 12, the electrical impedance of the piezoelectric elements in the nozzles 18 and 20 can be continuously measured during operation of the cleaning system 10 or during a test run. If the measured electrical impedance is observed approaching a predefined minimum or maximum value, it is possible to determine how far the aging process of the respective piezoelectric element has progressed. The invention thus enables the predictive replacement of an already aged piezoelectric element.This significantly increases the operational readiness of the cleaning system 10 according to the invention, since already aged piezoelectric elements can be replaced proactively. Both the cleaning quality and the reliability of the cleaning system 10 can thus be considerably improved.

[0027] Fig. 2 Figure 1 shows a side view of the nozzle unit 16, into which both the cleaning fluid lines and the high-frequency line 28 open. Arrow 22 points in Fig. 2 Arrow 24 again designates the connection point for a cleaning fluid line leading to the first nozzle 18. Arrow 24 designates a connection point for the cleaning fluid line leading to the second nozzle 20, which is located in Fig. 2 is covered by the first nozzle 18.

[0028] In the side surface into which the high-frequency line 28 and the two cleaning fluid lines open, there are also bores, in particular threaded bores, provided to mount the nozzle unit 16 on a bracket not shown.

[0029] Fig. 3 shows the nozzle unit 16 in another side view, with the viewing angle changing in Fig. 3 from the perspective of Fig. 2 differs by 180°. Fig. 3 Only the second nozzle 20 is visible, which obscures the first nozzle 18.

[0030] Fig. 4 Figure 1 shows several views from different angles of a nozzle unit 160 according to a further embodiment of the invention. The nozzle unit 160 has a first nozzle 180, which is provided with a piezoelectric element that can oscillate at a frequency of 800 kHz. The nozzle unit 160 has a second nozzle 200, which has a piezoelectric element that can oscillate at a frequency of 1 MHz. The signal generator 21, which is located in Fig. 1 The signal generator 12, which is shown schematically, is designed to generate electrical signals that have a main component with a frequency between 400 kHz and 10 MHz. Fig. 1 It can therefore also be used for the operation of the nozzle unit 160.

[0031] Fig. 4 shows the end section of the high-frequency line 28, which leads into the nozzle line 160. Further details are shown in Fig. 4In the upper right view, a connection point 220 for supplying cleaning fluid to the first nozzle 180 can be seen. Furthermore, a connection opening 240 for supplying cleaning fluid to the second nozzle 200 can be seen in this view.

[0032] Nozzles 180 and 200 differ in size. They each form the respective piezoelectric element. The larger nozzle 180 can therefore oscillate at the lower frequency of 600 kHz, while the smaller nozzle 200 oscillates at the higher frequency of 1 MHz.

Claims

1. A cleaning system comprising at least one nozzle for passing a cleaning fluid, at least one piezoelectric element for converting an electrical signal into mechanical vibrations, and at least one signal generator for generating the electrical signal, wherein the signal is transmitted to the piezoelectric element and the mechanical vibrations generated by the piezoelectric element are introduced into the cleaning fluid, characterized in that the at least one piezoelectric element is arranged in the at least one nozzle and that the signal generator has means for impedance detection in order to detect and monitor an electrical impedance of the piezoelectric element, in particular during operation of the cleaning system.

2. Cleaning system according to claim 1, characterized in that the signal generator is designed to generate electrical signals in a frequency range from 400 kHz to 10 MHz.

3. Cleaning system according to claim 1 or 2, characterized in that at least two nozzles are provided, wherein central longitudinal axes of the nozzles are arranged at an angle to each other, so that cleaning fluid emerging from the nozzles meets each other at a distance from the nozzles.

4. Cleaning system according to claim 3, characterized in that the piezoelectric element arranged in the first nozzle receives a first electrical signal having a main component of a first frequency and the piezoelectric element arranged in the second nozzle receives a second electrical signal having a main component of a second frequency which is different from or equal to the first frequency.

5. Method for operating a cleaning system according to one of the preceding claims, characterized by Detecting an impedance of the at least one piezoelectric element at least during operation of the cleaning device.

6. Method according to claim 5, characterized by Compare the measured impedance with a predefined target impedance or with predefined maximum and minimum values for the impedance.

7. Method according to claim 5 or 6, characterized by Determining an aging state of the at least one piezoelectric element, in particular by determining a gradient of the detected electrical impedance and / or by comparing a detected impedance with at least one predefined value of the impedance.

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