JP2006513844A - Improved megasonic cleaning efficiency using automatic adjustment of RF generator with constant maximum efficiency - Google Patents

Abstract

【Task】
A system and method for cleaning a substrate (202) includes a megasonic chamber (206) that includes a transducer (210) and a substrate (202). The transducer (210) faces the substrate (202). The transducer (210) and the substrate (202) are separated by a variable distance d. The system (200) also includes a dynamically adjustable RF generator (212) having an output coupled to the transducer. The dynamically adjustable RF generator (212) can be controlled by comparing the phase of the output voltage of the oscillator (306) with the phase of the output voltage of the RF generator. The dynamically adjustable RF generator (212) is also controlled by monitoring the peak voltage of the output signal and controlling the RF generator to maintain the peak voltage within a predetermined voltage range. You can also. The dynamically adjustable RF generator (212) can also be controlled by dynamically controlling a variable DC voltage source.

Description

  The present invention generally relates to systems and methods for tuning an RF generator. More particularly, the present invention relates to a method and system for automatically tuning an RF generator used in a substrate cleaning system.

  The use of acoustic energy is small from substrates such as semiconductor wafers, flat panel displays, MEMS (micro electro mechanical systems) and optical MEMS (micro opto electro mechanical systems) in various manufacturing stages. It is a non-contact advanced cleaning technique for removing particles. This cleaning step generally removes particles from the substrate surface or cleans the substrate surface by propagating acoustic energy through the liquid medium. Acoustic energy is generally propagated at frequencies in the range of about 700 kHz (0.7 megahertz (MHz)) to about 1.0 MHz. The liquid medium may be deionized water, any one or more of several types of substrate cleaning chemicals, or combinations thereof. The propagation of acoustic energy through a liquid medium is mainly due to the generation and collapse of bubbles from dissolved gases in the liquid medium, called cavitation, through microstreaming, and by improved mass transport. When a chemical substance is used, or when activation energy that promotes a chemical reaction is provided by the chemical substance, non-contact type substrate cleaning is realized through enhancement of the chemical reaction.

  FIG. 1A illustrates a standard batch substrate cleaning system 10. FIG. 1B is a top view of the batch type substrate cleaning system 10. The tank 11 is filled with a cleaning solution 16 such as deionized water or other substrate cleaning chemicals. The substrate carrier 12 generally holds a group of substrates 14 that are targets for cleaning by taking the form of a substrate cassette. One or more transducers 18 A, 18 B, 18 C generate radiated acoustic energy 15 that is propagated through the cleaning liquid 16. The relative positions of the substrate 14 and the transducers 18A, 18B, 18C and the distance between them are generally determined by which group of substrates 14 by the mounting fixtures 19A, 19B that contact the substrate carrier 12 and position the substrate carrier 12. Is maintained almost constant.

  Radiant energy 15 was enhanced through cavitation and acoustic streaming, and whether cleaning chemicals were used, with or without the appropriate chemicals to control particle reattachment Substrate processing is realized through mass transport. The batch type substrate cleaning process generally requires a very long processing time and may consume excessive cleaning chemicals 16. Also, consistency and board-to-board control are difficult to achieve. In batch and other substrate megasonic processes, phenomena such as “shadowing” and “hot spots” are common. The shadowing is caused by at least one of reflection of the radiant energy 15 and destructive interference and constructive interference of the radiant energy 15. The shadowing deteriorates as the surface area of the plurality of substrates 14 and the walls of the processing tank increase. To do. Hot spots that arise primarily as a result of reflection and as a result of constructive interference due to the use of multiple transducers can also increase with increasing surface area of multiple substrates. These problems are generally addressed by the averaging effect provided to the substrate by multiple reflections of acoustic energy. This averaging action can reduce the average output to the surface of the substrate. In order to compensate for the decrease in average power and at the same time enable effective cleaning and particle removal, the power to the transducer is increased, thereby increasing the radiant energy 15, promoting cavitation and acoustic streaming, and effective cleaning It is done to improve the sex. It is also practiced to pulsate a plurality of transducer arrays 18A, 18B, 18C (ie, a duty cycle such as turning on the transducer for 20 milliseconds and turning off the transducer for the next 10 milliseconds). Provided.) The transducers 18A, 18B, 18C can also be actuated (eg, driven sequentially) to produce phase mismatch, thereby reducing complex reflections and interference.

  FIG. 1C is a schematic diagram 30 of a conventional RF power supply that powers one or more transducers 18A, 18B, 18C. An adjustable voltage controlled oscillator (VCO) 32 outputs a signal 33 to the RF generator 34 at a selected frequency. The RF generator 34 amplifies the signal 33 and generates a signal 35 with increased power. Signal 35 is output to transducer 18B and monitored by power sensor 36. The transducer 18B outputs radiant energy 15.

  The exact impedance of the transducer 18B can vary depending on a number of variables such as, for example, the number, size, and spacing of the substrates 14 in the carrier 12 and the distance between the substrate 14 and the transducer 18B. The exact impedance of transducer 18B can also vary due to aging with repeated use. For example, if the frequency of the signals 33 and 35 is about 1 MHz, the wavelength in a deionized water medium such as the cleaning liquid 16 is about 1.5 mm (0.060 inches). Thus, as can be seen again with reference to FIG. 1A, if the misalignment between the substrate 14 and the carrier 12 is only about 0.5 mm (0.020 inches) or less, the impedance of the transducer 18B is significantly greater. Can vary. Furthermore, if the substrates 24, 24A are rotated, the impedance can vary periodically.

  Adjusting the frequency of the VCO can adjust the impedance of the transducer 18B as a result of varying the frequency of the signals 33, 35 and the radiant energy 15, and thus the wavelength. In general, the carrier 12 carrying the substrate 14 is placed in the tank 11 and the VCO 32 is adjusted to change the frequency of the signals 33 and 35 and the radiant energy 15. This adjustment continues until the impedance of the transducer 18B matches, which is indicated by the reflected signal 38 detected by the wattmeter 36 having a minimum value. VCO 32 tuned until reflected signal 38 takes a minimum value is generally not readjusted until significant repairs or maintenance is performed on substrate cleaning system 10.

  If the impedance of transducer 18B is mismatched, a portion of the radiant energy (ie, energy wave) 17 emitted from transducer 18B is reflected back to transducer 18B. The reflected energy 17 can cause constructive and destructive interference by interfering with the radiant energy 15 at the surface of the transducer 18B. In the case of destructive interference, a portion of the radiant energy 15 is effectively canceled out by the reflected energy 17, so that the effective cleaning power by the radiant energy 15 is reduced. As a result, the efficiency of the RF generator 34 is reduced.

  Constructive interference causes excessive energy and can generate hot spots on the surface of the substrate 14 that is the target of the cleaning. Hot spots can exceed the energy threshold of the substrate 14 and damage the substrate 14. FIG. 1D is a standard transducer 18B. FIG. 1E is a graph 100 showing the distribution of energy emitted from the transducer 18B. A curve 102 shows the distribution of energy radiated from the transducer 18B in the x-axis direction. A curve 104 shows the distribution of energy radiated from the transducer 18B in the y-axis direction. A curve 120 shows the distribution of energy radiated from the transducer 18B in the x-axis direction and the y-axis direction. The combined distribution of energy emitted from transducer 18B in the x-axis and y-axis directions is typically caused by known variables (eg, substrate position, transducer degradation, and rotational substrate fluctuations relative to the transducer). As the impedance of the transducer 18B changes, the curve 120 and the curve 122 may fluctuate. The energy threshold level T is a threshold for damage to the substrate 14. Generally, the maximum power of the RF signal 35 and the corresponding radiant energy 15 output from the transducer 18B has a peak value (ie, the peak value of the curve 120) at which the maximum constructive interference occurs, and the energy threshold T of the substrate 14. The substrate 14 is prevented from being damaged by being reduced to a level that can be suppressed as follows. However, the reduction of the RF signal 35 and the radiant energy 15 increases the time required for the cleaning process required to achieve the desired cleaning result. The reduced RF signal 35 and radiant energy 15 may not be large enough to remove target particles from the substrate 14 in some cases. As shown in the figure, the effective radiant energy can move to a much lower level (represented by a valley in curve 122) and seriously affect the effectiveness of the cleaning process. This is because the effective energy is too low (about 3), resulting in an energy window ranging from about 3 to about 17 on the energy scale.

  The transducer 18B is generally a piezoelectric element such as quartz. Constructive and destructive interference caused by the reflected energy 17 may exert sufficient force on the surface of the transducer 18B to generate a corresponding reflected signal 38. The power sensor 36 can detect a reflected signal 38 that is reflected from the transducer 18B to the RF generator 34. The reflected signal 38 may further reduce the efficiency of the RF generator 34 by interacting constructively or destructively with the signal 35 output from the RF generator 34.

  As can be seen, there is a need for an improved megasonic cleaning system that increases the efficiency of the RF generator and reduces the energy window of the emitted acoustic energy, reducing the possibility of damage to the substrate. .

  The present invention meets these needs by providing a transducer and a dynamically tuned RF generator that is constantly tuned to maintain resonance of the energy emitted by the transducer. Note that the present invention can be realized in various forms including a process, an apparatus, a system, a computer-readable medium, or a device. In the following, several embodiments of the invention will be described.

  One embodiment provides a method for dynamically adjusting the RF generator to the instantaneous resonant frequency of the transducer. The method includes inputting an RF input signal from an oscillator to an RF generator. The first phase of the input voltage of the RF input signal is then measured. Next, the second phase of the voltage of the RF signal output from the RF generator is measured. The RF signal output from the RF generator is coupled to the input of the transducer. If the first phase is not equal to the second phase, a frequency control signal is generated. The frequency control signal is applied to the frequency control input unit of the oscillator.

  Measuring the first phase may include scaling the measurement voltage of the first phase. The step of measuring the second phase may include scaling the measurement voltage of the second phase. Applying the frequency control signal to the frequency control input of the oscillator may include scaling the frequency control signal.

  The step of applying a frequency control signal to the frequency control input of the oscillator can also include combining the frequency control signal with a fixed value control signal.

  The step of generating the frequency control signal when the first phase is not equal to the second phase includes reducing the frequency of the oscillator by the frequency control signal if the first phase lags behind the second phase, When the phase of 1 precedes the second phase, the frequency of the oscillator is increased by the frequency control signal, and when the first phase is equal to the second phase, the frequency of the oscillator is not changed by the frequency control signal. The resonance of the transducer varies with variations in the distance between the transducer and the target.

  The measurement of the first phase and the second phase and the generation of the frequency control signal are performed every cycle of the RF input signal. The above method may also include applying at least one of a proportional control signal and an integral control signal to the frequency control signal.

  Another embodiment provides a system for applying RF to a transducer. The system includes an oscillator, an RF generator, and a voltage phase detector. The oscillator has a frequency control input and an RF signal output. The RF generator has an input coupled to the RF signal output of the oscillator and an RF generator output coupled to the transducer. The voltage phase detector includes a first phase input coupled to the RF signal output of the oscillator, a second phase input coupled to the RF generator output, and a frequency control voltage input of the oscillator. And a frequency control signal output unit coupled to the.

  The first phase input may be coupled to the RF signal output of the oscillator via a scale change device. The second phase input may also be coupled to the RF generator output via a scale change device.

  The frequency control signal output may be coupled to the frequency control input of the oscillator via a control amplifier. The control amplifier includes a first input coupled to the frequency control signal output, a second input coupled to the constant value control signal, and an output coupled to the frequency control input of the oscillator. You may have. The RF generator may be a Class E RF generator.

  The transducer may be directed toward a target that is a variable distance from the transducer. The transducer can be provided in a megasonic cleaning chamber. The target can be a semiconductor substrate. The RF generator may operate in the range from about 400 kHz to about 2 MHz.

  Another embodiment provides a transducer RF power source that includes a voltage controlled oscillator (VCO), a class E RF generator, and a voltage phase detector. The VCO has a frequency control voltage input unit and an output unit. Class E RF generators have an input coupled to the output of the VCO and an RF generator output coupled to a transducer having a variable impedance. The voltage phase detector includes a first phase input coupled to the output of the VCO, a second phase input coupled to the RF generator output, and a frequency control voltage of the VCO via a control amplifier. And a voltage control signal output unit coupled to the input unit. The control amplifier has a first input coupled to the voltage control signal output, a second input coupled to the constant value control signal, and an output coupled to the frequency control voltage input of the VCO. Part.

  One embodiment provides a substrate cleaning method including applying an RF signal to a transducer at a frequency f. The transducer faces the substrate so as to emit acoustic energy at a frequency f towards the substrate. The substrate is moved relative to the transducer. The RF signal is dynamically tuned to maintain acoustic energy resonance.

  The step of dynamically adjusting the frequency f may include automatically adjusting the frequency f every cycle of the RF signal. The step of moving the substrate relative to the transducer may include rotating the substrate.

  The substrate may be immersed in a cleaning liquid. The cleaning liquid may be deionized water. The cleaning liquid may contain one or more types of cleaning chemicals. Dynamically adjusting the RF signal to maintain the resonance of the acoustic energy may include maintaining the voltage of the RF signal applied to the transducer constant.

  The RF generator may apply an RF signal to the transducer, and maintaining the voltage of the RF signal applied to the transducer constant includes measuring a first voltage of the RF signal, and applying a first voltage to the transducer. Comparing with a desired voltage target value and adjusting the output voltage of the variable DC power supply by inputting a control signal to the variable DC power supply may be included. The variable DC power supply supplies DC power to the RF generator. Dynamically adjusting the RF signal to maintain acoustic energy resonance may include dynamically adjusting the frequency f of the RF signal applied to the transducer.

  The RF generator may apply an RF signal to the transducer, and the step of dynamically adjusting the frequency f of the RF signal applied to the transducer comprises measuring a power supply voltage applied to the RF generator, RF Measuring the peak voltage across the output amplifier provided in the generator, generating a frequency control signal when the peak voltage is not equal to the selection ratio of the power supply voltage, and the frequency control input of the oscillator generating the RF signal Applying a frequency control signal to the unit may be included.

  The RF generator may apply an RF signal to the transducer, and the step of dynamically adjusting the frequency f of the RF signal applied to the transducer inputs the RF input signal from the oscillator to the RF generator, and RF Amplifying the RF signal within the generator may be included. The first phase of the input voltage of the RF input signal is measured, and then the second phase of the voltage of the RF signal output from the RF generator is measured. If the first phase is not equal to the second phase, a frequency control signal is generated. The frequency control signal is applied to the frequency control input of the oscillator.

  Another embodiment provides a substrate cleaning system that includes a cleaning chamber having a transducer and a substrate. The transducer faces the substrate. The transducer and the substrate are separated by a variable distance d. The system also includes a dynamically adjustable RF generator having an output coupled to the transducer and a feedback circuit coupled to the control input of the adjustable RF generator. The substrate can be rotated. The distance d can vary by about ½ wavelength of the RF signal output from the RF generator as the substrate rotates.

  The dynamically adjustable RF generator may include a variable DC power source having a control input and a DC output coupled to the RF generator. The feedback circuit includes a first input coupled to the constant value control signal section, a second input coupled to the RF output section of the RF generator, and a control input section of the adjustable RF generator. A comparator having a control signal output coupled thereto. The control input unit may include a voltage control input unit for the variable DC power supply.

  A dynamically adjustable RF generator may include an oscillator, an output amplifier coupled to the output of the oscillator, and a load network. The oscillator has a control signal input unit and an RF signal output unit. The load network is coupled between the output of the output amplifier and the output of the RF generator. The feedback circuit may include a peak voltage detector and a second comparator. A peak voltage detector may be coupled across the output amplifier. The second comparator includes a third input coupled to the output of the variable DC power supply, a fourth input coupled to the output of the peak voltage detector, and an adjustable RF generator. And a second output coupled to the control input. The control input unit may include an oscillator control signal input unit.

  The dynamically adjustable RF generator may include an oscillator and an RF generator input coupled to the RF signal output of the oscillator. The oscillator has a frequency control input unit and an RF signal output unit. The feedback circuit may include a voltage phase detector. The voltage phase detector includes a first phase input coupled to the RF signal output of the oscillator, a second phase input coupled to the RF generator output, and an adjustable RF generator. And a frequency control signal output unit coupled to the control input unit. The control input unit may include an oscillator frequency control voltage input unit.

  The dynamically adjustable RF generator includes a voltage source, an oscillator having a control signal input and an RF signal output, an output amplifier coupled to the output of the oscillator, an output of the output amplifier, and an RF And a load network coupled between the output of the generator. The feedback circuit may include a peak voltage detector coupled across the output amplifier and a comparator circuit. The comparator circuit is coupled to a first input coupled to the voltage source, a second input coupled to the output of the peak voltage detector, and a control input of the adjustable RF generator. And a comparator output unit. The control input unit may include an oscillator control signal input unit.

  The dynamically adjustable RF generator may include an oscillator and an RF generator input coupled to the RF signal output of the oscillator, and the feedback circuit may include a voltage phase detector. The oscillator has a frequency control input unit and an RF signal output unit. The voltage phase detector includes a first phase input coupled to the RF signal output of the oscillator, a second phase input coupled to the RF generator output, and an adjustable RF generator. And a frequency control signal output unit coupled to the control input unit. The control input unit may include an oscillator frequency control voltage input unit.

  The transducer may include two or more transducers. The dynamically tunable RF generator may include two or more dynamically tunable RF generators, each output coupled to one of two or more transducers. . The transducer may include a first transducer facing the active surface of the substrate and a second transducer facing the non-active surface of the substrate.

  One embodiment provides a method for dynamically adjusting the RF generator to the instantaneous resonant frequency of the transducer. The method includes applying an RF input signal from an oscillator to an RF generator and measuring a power supply voltage applied to the RF generator. The peak voltage is then measured in the RF generator. If the peak voltage is not equal to the power supply voltage selection ratio, a frequency control signal is generated. The frequency control signal is applied to the frequency control input unit of the oscillator.

  Measuring the peak voltage may include measuring the peak voltage of each cycle of the RF input signal. Measuring the peak voltage may include measuring a voltage across an output amplifier provided in the RF generator. The output amplifier may be a CMOS device, and the peak voltage is equal to the drain-source voltage of the output amplifier. Measuring the power supply voltage applied to the RF generator may include scaling the measured power supply voltage. Measuring the peak voltage may also include scaling the measured peak voltage.

  The selection ratio of peak voltage to power supply voltage may be equal to a range from about 3: 1 to about 6: 1. More specifically, the selection ratio of peak voltage to power supply voltage may be equal to about 4: 1 or about 3.6: 1. The above method may also include applying at least one of a proportional control signal and an integral control signal to the frequency control signal section. The above method may also include applying an amplified RF signal output from the RF generator to the transducer. It should be noted that the transducer faces the target and the distance between the transducer and the target is a variable distance.

  Another embodiment provides a system for generating RF. The system includes a voltage source, an oscillator, an output amplifier, a load network, a peak voltage detector, and a comparator circuit. The oscillator has a control signal input unit and an RF signal output unit. The output amplifier is coupled to the output of the oscillator. The load network is coupled between the output of the output amplifier and the output of the RF generator. A peak voltage detector is coupled across the output amplifier. The comparator circuit includes a first input coupled to the voltage source, a second input coupled to the output of the peak voltage detector, and a comparison coupled to the control signal input of the oscillator. Output unit. The RF generator output may also be coupled to a transducer.

  When the power supply voltage is not equal to the selection ratio of the peak voltage output by the peak voltage detector, a control signal can be output from the comparator output unit. The peak voltage detector may include a first capacitor connected in series with a second capacitor and a diode connected in parallel with the second capacitor. The first input of the comparator is coupled to a voltage source via a first scale change device. The peak voltage detector may include a second scale change device. The comparator may include an operational amplifier. The oscillator may operate in the range from about 400 kHz to about 2 MHz.

  Another embodiment includes a voltage source, a voltage controlled oscillator (VCO) having a control voltage input and an output, and an output amplifier coupled to the output of the VCO. A class E load network is also coupled between the output of the output amplifier and the output of the RF generator. A peak voltage detector is coupled across the output amplifier. The comparator circuit includes a first input coupled to the voltage source, a second input coupled to the output of the peak voltage detector, and a comparison coupled to the control voltage input of the VCO. If the peak voltage output from the peak voltage detector and the power supply voltage are not equal to a ratio of about 3.6: 1, a control voltage is output from the comparator output. The transducer is coupled to the RF generator output.

  One embodiment includes a method of maintaining an input voltage to a transducer constant. The method includes applying an RF signal from an RF generator to a transducer, measuring a first voltage of the RF signal, comparing the first voltage to a desired voltage target value, and a variable DC power supply And adjusting the output voltage of the variable DC power supply by inputting a control signal to. The variable DC power supply supplies DC power to the RF generator. Measuring the first voltage may include scaling the measured first voltage.

  The first voltage is a function of the impedance of the transducer. The impedance of the transducer can vary with variations in the distance between the transducer and the target.

  Comparing the first voltage with a desired voltage target value may include determining a control signal. The control signal is approximately equal to the difference between the first voltage and the desired voltage target value.

  The step of adjusting the output voltage of the variable DC power supply may include applying at least one of proportional control and integral control to the control signal. The above method may also include directing the transducer toward the target. Note that the distance between the transducer and the target is a variable distance.

  Another embodiment provides a system for generating RF that includes an RF generator, a variable DC power source, and a comparator. The RF generator has an RF output coupled to the input of the transducer. The variable DC power supply has a control input and a DC output coupled to the RF generator. The comparator is coupled to a first input coupled to the constant value control signal section, a second input coupled to the RF output section of the RF generator, and a voltage control input section for the variable DC power supply. A control signal output unit.

  The second input is coupled to the RF output of the RF generator via a voltage scale change device. The comparator may include at least one of a proportional control input unit and an integral control input unit. The RF generator may be a Class E RF generator. The voltage of the RF signal is a function of the impedance of the transducer. The impedance of the transducer varies with variations in the distance between the transducer and its target.

  The transducer may be provided in the megasonic cleaning chamber. The target of the transducer may be a semiconductor substrate. The comparator may be an operational amplifier.

  Another embodiment provides a transducer RF power source that includes a Class E RF generator, a variable DC power source, and a comparator. Class E RF generators have an RF output coupled to the input of the megasonic transducer in the megasonic cleaning chamber. The variable DC power supply has a control input and a DC output coupled to the RF generator. The comparator is coupled to a first input coupled to the target voltage source, a second input coupled to the RF output of the RF generator, and a voltage control input for the variable DC power supply. A control signal output unit.

  The present invention allows the use of higher power acoustic energy without damaging the substrate being cleaned (eg, without generating a “hot spot” of acoustic energy), thus greatly reducing the time of the cleaning process. Has the advantage of being The present invention can thus reduce the number of substrates that are damaged by excessive acoustic energy.

  Also, the self-tuning RF generator can be automatically adjusted in response to process changes such as changes in cleaning chemicals or substrate positions, thereby improving the flexibility and robustness of the cleaning process. be able to.

  Other features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

  The present invention can be readily understood by the following detailed description given with reference to the accompanying drawings. For ease of explanation, similar components will be denoted by similar reference numerals.

  In the following, several exemplary embodiments for automatically and dynamically adjusting the RF signal supplied to the transducer are described. It will be apparent to those skilled in the art that the present invention may be practiced without some or all of the details specified herein.

  As mentioned above, it is very important to increase the cleaning effectiveness, efficiency, and throughput rate of a substrate cleaning system while reducing the possibility of substrate damage. These needs are exacerbated by the fact that the device is becoming smaller and that many of the cleaning systems are evolving into a single substrate cleaning system.

  2A and 2B illustrate a dynamic single substrate cleaning system 200 in accordance with one embodiment of the present invention. FIG. 2A is a side view of a dynamic single substrate cleaning system 200. FIG. 2B is a top view of a dynamic single substrate cleaning system 200. The substrate 202 is immersed in a cleaning liquid 204 that fills the cleaning chamber 206. The cleaning liquid 204 may be deionized water (DI water) or other cleaning chemicals known in the art, or combinations thereof.

  The substrate 202 has a substantially circular shape and is held by three or more edge rollers 208A, 208B, 208C (or similar edge holding devices), so that with the cleaning process applied to the substrate 202, Can rotate (eg, in direction 209A). One or more of the three edge rollers 208A, 208B, 208C may be driven (eg, in direction 209B) to rotate the substrate 202 in direction 209A. The substrate 202 can rotate at a speed of up to about 500 RPM.

  The cleaning chamber 206 can also include a transducer 210 as part thereof. The transducer 210 may be a piezoelectric element such as quartz, for example, and can convert the RF signal 220 into acoustic energy 214 and radiate it into the cleaning liquid 204. The transducer 210 is formed by bonding a piezoelectric material such as piezoelectric ceramic, lead titanium zirconate, piezoelectric quartz, or gallium phosphate to a resonator such as ceramic, silicon carbide, stainless steel, aluminum, or quartz. Can be configured.

  As shown in FIG. 2B, the transducer 210 may be significantly smaller than the substrate 202. The smaller the transducer, the cheaper it can be manufactured, and the better it can control the small area of the substrate 202 to which the radiant energy 214 from the transducer strikes. The active surface 218 of the substrate 202 (ie, the surface having active elements) is generally the surface facing the transducer 210. However, in some embodiments, the opposite side of the substrate 202 from the transducer 210 is the active surface 218.

  While the substrate 202 rotates and passes the transducer 210, the three edge rollers 208A, 208B, and 208C are at a substantially fixed distance d1 from the transducer 210. The distance d1 can range from a few millimeters to about 100 millimeters or more. The distance d1 is selected as a distance that matches the impedance of the transducer 210. In one embodiment, distance d 1 is selected as the resonant distance for the frequency of radiant energy 214. Alternatively, the frequency of the radiant energy 214 can be selected to have the distance d1 as the resonance distance. In either case, the reflected energy 216 reflected by the substrate 202 and returning to the transducer 210 is minimized during resonance. As described above, the reflected energy 216 interferes with the radiant energy 214, thereby reducing the power efficiency of the RF signal 220 and reducing the effectiveness of cleaning the substrate 210 (eg, interference fringes).

  However, the substrate 202 can cause some “fluctuation”. This may vary the distance between the substrate 202 and the transducer 210 from the first distance d1 to the second distance d2 as the substrate 202 rotates past the transducer 210. The difference between the first distance d1 and the second distance d2 may be greater than or equal to about 0.5 mm (0.020 inches). Even though the improved edge rollers 208A, 208B, 208C and other similar techniques can hold the substrate 202 at a more consistent distance d1 from the transducer 210, it does not guarantee an absolute constant distance. Thus, the distance d1 can still vary. Further, the distance between the substrate 202 and the transducer 210 may vary due to other factors (eg, mounting of the substrate 202 to the edge rollers 208A, 208B, 208C). As will be described in detail later, variations in the distance between the substrate 202 and the transducer 210 can seriously affect the performance and efficiency of the cleaning system 200.

  Transducer 210 is coupled to RF generator 212. FIG. 2C illustrates a method step 250 of the method according to one embodiment of the present invention for an auto-tuning RF generator system used in, for example, a megasonic cleaning system 200 as described in FIGS. 2A and 2B. It is a flowchart. In step 255, the RF generator applies the RF signal 220 to the transducer 210. The RF signal 220 can have a frequency from about 400 kHz to about 2 MHz, and can generally have a frequency from about 700 kHz to about 1 MHz. The wavelength of the high frequency acoustic energy 214 emitted from the transducer 210 is approximately 1.5 mm (0.060 inches) long in the cleaning liquid 204.

  In step 260, the distance to the target (eg, substrate 202, etc.) varies with the relative movement of the target relative to the transducer 210. As the distance d1 changes, the amount of reflected energy 216 also changes because the radiant energy 214 does not necessarily remain in resonance (ie, the impedance of the transducer 210 becomes mismatched). In step 270, the RF generator 212 is automatically and dynamically tuned so that the RF signal 220 is tuned constantly to correct for impedance mismatches associated with variations in the distance d1.

  Since the wavelength of the radiant energy 214 is about 1.5 mm (0.060 inches), even a movement of only 0.50 mm (0.020 inches) can drastically change the impedance. As a result, for example, the voltage varies by 50%, and the power varies by about 25% to 100%. Thus, without an auto-tuning RF generator that cancels out the variation in distance d1, the peak energy level of radiant energy 214 is reduced to a value that is low enough not to exceed the energy absorption capability (energy threshold) of substrate 202. By doing so, it is necessary to prevent the substrate 202 from being damaged by the peak radiant energy.

  The auto-tuned RF generator 212 can perform auto-tuning to offset the variation of the distance d1 through various approaches. One embodiment maintains the RF generator 121 in a state that generates an RF signal 220 with a frequency that optimizes impedance by detecting the peak voltage. Another embodiment causes the RF signal 220 to be generated at a frequency that optimizes impedance by maintaining voltage phase. Yet another embodiment can adjust the power supply to a condition that allows the generation of an RF signal 220 that optimizes impedance. These various embodiments can also be used in combination within a single RF generator system that is self-tuning.

  FIG. 3 is a block diagram illustrating an auto-tuning RF generator system 300 in accordance with one embodiment of the present invention. The self-tuning RF generator 302 adjusts the frequency of the VCO RF signal 310 output from the VCO 306 by providing a feedback control signal to the voltage controlled oscillator (VCO) 306. The VCO 306 can also be incorporated into the RF generator 302 as part of the RF generator 302. The DC power supply 312 supplies a DC power supply for amplifying the VCO RF signal 310 in the RF generator 302. The self-tuning RF generator 302 has an inductor 314 at its input site. The RF generator 302 also includes one or more amplifiers 320 that amplify the VCO RF signal 310.

In one embodiment, amplifier 320 is CMOS and VCO RF signal 310 is applied to gate G. Drain D is coupled to DC bias rail 322 and source S is coupled to ground potential rail 324. A drain-source peak voltage (peak V _ds ) detector 326 for obtaining a drain-source peak voltage of the amplifier 320 is coupled between the drain D and the source S of the amplifier 320.

  The output of amplifier 320 is coupled to the input of class E load network 330. Class E load network 330 is a common well known in the art for performing large impedance matching functions between an RF power source (ie, RF generator 302) and an RF load (ie, transducer 332). Device. Class E load network 330 typically includes an LC network. The output of class E load network 330 is coupled to the input of transducer 332.

  FIG. 4 is a flowchart illustrating a method step 400 of the self-tuning RF generator system 300 when the RF generator 302 applies the RF signal 220 to the transducer 332 in accordance with one embodiment of the present invention. . In step 405, the DC power supply voltage is measured or detected by the comparator device 340. A voltage divider network 342 may also be provided to scale or reduce each voltage coupled from the DC power supply 312 to the comparator device 340 to a level usable by the comparator device 340. In addition, proportional / differential / integral control may be provided in the comparator device 340 in order to make it possible to select the change rate and change amount of the control signal.

In step 410, the peak V _ds is detected by the peak V _ds detector 326 is supplied to a second input of the comparator device 340. Peak Vds detector 326 also includes circuitry for scaling or reducing each voltage coupled from peak V _ds detector 326 to comparator device 340 to a level usable by comparator device 340. it can.

For example, when the DC power supply 312 outputs 200 VDC and the comparator device 340 can compare 5 VDC signals, the voltage divider network 342 converts the DC power supply voltage of 200 VDC to a voltage of 5 VDC representing 200 VDC in the comparator device 340. Can be scaled. Similarly, the peak V _ds detector 326 can also include a scaling device, such as a voltage divider network, so that the actual peak V _ds applied to the comparator device 340 can be about 5 VDC.

In step 415, the comparator device 340 compares the peak V _ds with the DC power supply voltage from the DC power supply 312. If the DC power supply voltage is at the desired ratio of peak V _ds, no correction signal is output from the comparator device and the method proceeds to step 405 above.

If the DC supply voltage is not the desired ratio of peak V _ds , the method proceeds to step 420. In step 420, a corresponding correction signal is output from the comparator device 340 to the VCO 306 to adjust the frequency of the VCO output signal 310, after which the method proceeds to step 405 above. The correction signal can adjust the frequency of the VCO RF signal 310 to a higher or lower frequency as needed.

The desired ratio of the DC power supply voltage to the peak V _ds is the various components of the RF generator 302 and transducer 332 and of the system such as the substrate cleaning system 200 of FIG. 2 that may include the RF generator 302 and transducer 332. Depends on the specific value of. In one embodiment, the desired ratio ranges from about 3: 1 to about 6: 1, where the peak V _ds is greater than the DC power supply voltage. In one embodiment, the desired ratio is about 4: 1, more specifically about 3.6: 1, where the peak V _ds is equal to about 3.6 times the DC power supply voltage.

FIG. 5A is an illustration showing the peak V _ds detector 326 in accordance with one embodiment of the present invention. Capacitors 502 and 504 connected in series are coupled between the drain D and source S of the amplifier 320. Diode 506 is coupled in parallel with capacitor 504. In operation, capacitor 502 couples peak V _ds for each cycle of the amplified RF signal to capacitor 504. Capacitor 504 stores the peak V _ds of each cycle of the amplified RF signal output from amplifier 320. Diode 506 may obtain a peak V _ds, the peak V _ds, binds to a comparator device 340 through the peak V _ds terminal.

FIG. 5B is a graph 550 illustrating the waveform of the peak voltage (V _ds ) detected by the peak voltage detector 326 in accordance with one embodiment of the present invention. Since the amplifier device 320 hardly causes a voltage drop when in the energized state, the peak voltage detector 326 does not detect much voltage at this time. When the amplifier is de-energized, the current stored in the inductors and capacitors of the RF generator 302 and load network 330 is discharged, resulting in the voltage waveforms 552, 554, and 556 being detected by the peak voltage detector 326. The The amplifier 320 is designed to form a tuned amplifier circuit by starting to energize with a voltage (V _ds ) drop. The tuned amplifier circuit is affected by any change in resonance of the transducer 332 (eg, relative movement of the substrate 202 relative to the transducer 332). Such changes are reflected through the load network 330 and change the detected voltage waveforms 552, 554, 556. When in resonance, amplifier 320 functions as a well-tuned class E amplifier, producing wavelength 554. When not in resonance, the transducer 332 can have either capacitive or inductive reactance. This results in increased capacitive or inductive reactance and detunes the class E load network 330. Detuned class E load network 330 produces waveform 552 or waveform 556, resulting in either peak voltage V1 being too high or peak voltage V3 being too low.

As a result of experiments and calculations, the peak voltage (V _ds ) is a function of the resonance of the transducer 332, and the resonance ratio of the peak V _{ds to} the applied DC bias voltage is a function of the components of the RF generator circuit 302. It has been found that. For example, in a standard RF generator, the ratio of peak voltage to DC bias voltage from a DC power supply is about 4: 1. That is, the peak V _ds can indicate the resonance state of the transducer 332 when it is about four times the bias voltage from the DC power supply 312.

  FIG. 6 is a block diagram illustrating an auto-tuning RF generator system 600 in accordance with one embodiment of the present invention. The voltage phase P1 of the RF signal 310 output from the VCO 306 is compared with the voltage phase P2 input to the transducer 332. If the voltage phases P1 and P2 do not match, a correction signal is applied to the frequency control input of the VCO 306. The RF generator system 600 includes an RF generator 602. The RF generator 602 may be any type of RF generator known in the art. The phase detector 604 has two inputs 606 and 608. The first and second inputs 606, 608 are scale circuits 610, 612 (eg, that can scale the detected signals (eg, phase P1 and phase P2) to a level usable by the phase detector 604, for example. Each may have a voltage divider network, etc.). The phase detector 604 may be any type of phase detector known in the art as long as the phase of each input voltage signal can be detected and compared. The conventional phase detector compares the voltage phase of the output RF signal 220 with the current phase. However, as a result of the test, it is easier and easier to compare the voltage phase P1 and the voltage phase P2, and the signal required to adjust the VCO 306 is easier and easier. I found that I can provide it.

  FIG. 7 is a flowchart illustrating method steps of a self-tuning RF generator system 600 in accordance with one embodiment of the present invention. In step 705, the RF generator 602 is applied with the input RF signal 310 from the VCO 306, amplifies the input RF signal 310, and couples the amplified RF signal 220 to the transducer 332.

  In step 710, the first input 606 couples the first phase (P 1) of the voltage of the RF signal 310 output from the VCO 306 to the phase detector 604. In step 715, the second input 608 couples the second phase (P 2) of the voltage of the signal input to the transducer 332 to the phase detector 604.

  In step 720, the phase detector compares phase P1 and phase P2 to determine whether phase P1 and phase P2 match. 8A to 8C are graphs showing three examples of the relationship between the phase P1 and the phase P2 according to an embodiment of the present invention. In FIG. 8A, a graph 800 shows a state in which the phase P1 precedes the phase P2 (for example, the phase P1 reaches a peak at time T1, and the phase P2 reaches a peak at subsequent time T2). This means that the impedance of transducer 332 is in an unmatched state and that transducer 332 is applying reflected signal 222 to RF generator 602.

  In FIG. 8B, a graph 820 shows a state in which the phase P1 is delayed from the phase P2 (for example, the phase P2 reaches a peak at time T1, and the phase P1 reaches a peak at subsequent time T2). This means that the impedance of the transducer 332 is in an unmatched state and that the transducer 332 is also applying the reflected signal 222 to the RF generator 602. The reflected signal output from the transducer 332 can cause constructive or destructive interference with the signal output from the RF generator 602.

  In FIG. 8C, a graph 850 shows a state in which the phase P1 is equal to the phase P2 (for example, both the phase P1 and the phase P2 reach a peak at time T1). This means that the impedance of the transducer 332 is matched and that the transducer 332 is not applying any reflected signal to the RF generator 602.

  In step 720, if phase P1 and phase P2 are equal, the method proceeds to step 705 (repeat step 705). In step 720, if phase P1 and phase P2 are not equal, the method proceeds to step 730. In step 730, an appropriate control signal is applied to the frequency control input of the VCO 306 to adjust the frequency of the RF signal 310. The method then proceeds to step 705 (repeat step 705). The control signal applied to the frequency control input of the VCO 306 can adjust the frequency higher in response to a state where the phase P1 precedes the phase P2. Alternatively, the control signal applied to the frequency control input unit of the VCO 306 can adjust the frequency to be lower in response to a state in which the phase P1 is delayed from the phase P2.

  The self-tuning RF generator system 600 can also include a control amplifier 620 that can scale the control signal output from the phase detector 604 to a signal level suitable for control of the VCO 306. The control amplifier 620 can also include a target value input, whereby the control amplifier 620 can combine the target value input and the control signal input from the phase detector. This allows the VCO RF signal 310 to be selected according to the target value, and thus allows the selected target value to be automatically adjusted by the control signal output by the phase detector 604.

  The systems and methods described in FIGS. 3-8C can automatically tune the RF generators 302, 602 with a very high correction factor (eg, every cycle of the input RF signal 310, the subsequent input RF signal 310 and the frequency of the output RF signal 220 can be corrected). Accordingly, the frequency of the input RF signal 310 can be corrected a plurality of times, for example, for each rotation of the substrate 202. This allows the acoustic energy 214 acting on the substrate 202 to be more precisely controlled.

  For example, if the substrate 202 rotates at 60 RPM (revolutions per second) and the RF signal 310 is approximately 1 MHz, the frequency of the RF signal 310 is approximately 1 million times per second (ie, 1 micron per revolution of the substrate 202). It can be corrected at a correction rate of once per second. Better control of the acoustic energy 214 acting on the substrate 202 means that the average energy can be very close to the energy minimum trough and energy maximum peak of the radiant energy 214. Accordingly, since higher average energy can be applied to the substrate 202, the cleaning time can be greatly shortened and the effectiveness of the cleaning can be greatly increased.

  FIG. 9 is a block diagram illustrating an auto-tuning RF generator system 900 in accordance with one embodiment of the present invention. The system has a VCO 306 coupled to the input of an RF generator 602. A variable DC power source 902 is coupled to the RF generator 602 and supplies a DC power source for amplifying the RF signal 310 from the VCO 306 to the RF generator. The output of the RF generator 602 is coupled to the transducer 322.

  Conventional standard acoustic energy cleaning systems focus on keeping the net power input to the transducer 322 (ie, the RF signal 220 input minus the reflected signal 222 output) constant. It has been found through experiments that the amplitude of the radiant energy 214 output from the transducer 332 is substantially constant if the voltage of the RF signal 220 is maintained at a constant voltage. Further, if the voltage of the RF signal 220 is maintained at a certain level below the energy limit value of the substrate 202, damage to the substrate can be prevented while maximizing the acoustic energy 214 acting on the substrate 202.

  FIG. 10 is a flowchart illustrating method steps of a self-tuning RF generator system 900 in accordance with one embodiment of the present invention. In step 1005, the RF generator 602 outputs an RF signal to the transducer 332. In step 1010, the voltage of the RF signal output to the transducer 332 is measured and coupled to the comparator 904.

  In step 1015, the comparator 904 compares the voltage of the RF signal output from the RF generator 602 with a desired voltage target value. If the output voltage is equal to the desired voltage target value, the method proceeds to step 1010. Alternatively, if the output voltage is not equal to the voltage target value, the method proceeds to step 1030.

  In Step 1030, the comparator 904 outputs a control signal to the control input unit of the variable DC power supply 902. For example, if the output voltage is too high (ie, greater than the desired voltage target), the control signal reduces the increase in amplification that occurs in the RF generator 602 by reducing the DC voltage output from the variable DC power supply 902. Further, the amplitude of the RF signal output from the RF generator 602 is reduced. Further, proportional / differential / integral control may be provided in the comparator 904 in order to enable selection of the change rate and change amount of the control signal.

  In addition, a scale changing circuit 906 may be provided in order to scale the voltage output from the RF generator 602 to a level that can be easily compared with the target value signal. For example, the scale change circuit 906 can scale the 200V RF signal to 5V for comparison with the 5V target value signal. The scale changing circuit 906 can include a voltage divider. The scale changing circuit 906 can also include a rectifier to rectify the voltage of the RF signal 220 output from the RF generator 602 into a DC voltage suitable for comparison with the DC target value signal.

  As described above, the method described in FIGS. 3-8C can automatically tune the RF generators 302, 602 with a very high correction factor (eg, once every few cycles of the RF signal 310). Conversely, the systems and methods described in FIGS. 9 and 10 can still autotune the RF generator 602, although its correction factor is slightly below that described in FIGS. 3-8C. The rate of change in impedance of the transducer 332 that may be caused by the movement of the substrate 202 is still exceeded.

  The systems and methods described in FIGS. 9 and 10 can also be used in combination with one or more of the systems and methods described in FIGS. 3-8C. Thus, the system and method described in FIGS. 3-8C can be used to control and adjust the tuning of the RF generator very finely, whereas the system described in FIGS. 9 and 10 And the method is used to tune the RF generator in a very diverse manner with respect to the dynamic resonance of the transducer 332.

  FIG. 11 is a diagram illustrating a megasonic module 1100 according to an embodiment of the present invention. The megasonic module 1100 may be a megasonic module, such as the material described in US patent application Ser. No. 10 / 259,023 “Megasonic Substrate Processing Module” dated September 26, 2002 by the same applicant. . This document is incorporated herein by reference in its entirety.

  The megasonic module 1100 includes a substrate processing tank 1102 (hereinafter referred to as a tank 1102) and a tank lid 1104 (hereinafter referred to as a lid 1104). A lid megasonic transducer 1108 and a tank megasonic transducer 1106 are provided on the lid 1104 and in the tank 1102, respectively, to provide megasonic energy for simultaneously processing the active and backside surfaces of the substrate 1110. Substrate 1110 is placed in drive wheel 1112 and secured in place by substrate stabilizing arm / wheel 1114. In one embodiment, the substrate stabilization arm / ring 1114 is provided with an actuator 1120 for opening and closing the stabilization arm / ring 1114 and a positioning rod 1122 to receive and secure the substrate 1110 to be processed in the megasonic module 1100. ,release. The lid 1104 can be located in either the open position or the closed position by an actuation system (not shown) that moves the lid 1104 up and down while the tank 1102 is stationary. Alternatively, the tank 1102 can move to engage the lid 1104.

  In one embodiment, the substrate stabilizer arm / ring 1114 is configured to fix and hold the substrate 1110 horizontally for processing and to allow the substrate 1110 to rotate. In another embodiment, the substrate processing is performed with the substrate 1110 held in the vertical direction. The drive wheel 1112 contacts the outer peripheral edge of the substrate 1110 and rotates the substrate 1110 during processing. The substrate stabilizing arm / ring 1114 can include a freely rotating wheel so that the substrate 1110 can be rotated while holding the substrate 1110 in a horizontal direction.

  Tank 1102 is filled with a processing fluid or chemical, including deionized (DI) water, as needed, once substrate 1110 is placed therein. When the desired processing fluid is filled in the closed megasonic module 1100, the substrate 1110 is immersed therein, and the megasonic processing of the substrate 1110 is performed by the tank megasonic transducer 1106 and the lid megasonic transducer 1108. The tank megasonic transducer 1106 directs megasonic energy to the surface of the substrate 1110 facing the tank megasonic transducer 1106, and the lid megasonic transducer 1108 is the surface of the substrate 1110 facing the lid megasonic transducer 1108. Toward megasonic energy. The drive wheel 1112 ensures that the entire surface of the active surface and the back surface of the substrate 1110 is processed completely and uniformly by rotating the substrate 1110 immersed in the processing chemical. In one embodiment, a drive motor 1116 is provided to drive the drive wheels 1112 via a mechanical coupling 1118 (eg, drive belts, gears, sprockets, chains, etc.).

  The self-tuning RF generator system described in FIGS. 3-10 allows each of the lid transducer 1108 and tank transducer 1106 to continually autotune to dynamic impedance as the substrate 1110 rotates. And can be coupled to one or both of the transducers 1108, 1106.

  FIG. 12 is a graph 1200 illustrating energy distribution in a transducer in accordance with one embodiment of the present invention. Compared to the conventional energy window shown by curves 120 and 122, the self-tuning RF generator can obtain a very narrow energy window 1202 sandwiched between curves 1210 and 1212. Since the energy window 1202 is very thin, the effectiveness of the cleaning process with acoustic energy can be increased by raising and approaching the energy threshold T of the substrate.

  The expression “about” as used in the description of the present invention means plus or minus 10%. For example, the expression “about 250” means a range from 225 to 275. Further, the instructions shown in the steps of FIGS. 4, 7, and 10 do not necessarily have to be executed in the order illustrated, and all the processes shown in the steps are not necessarily required to implement the present invention. It is not done.

  Although the invention has been described above with some specific details for clarity of understanding, it will be apparent to those skilled in the art that certain modifications can be made within the scope of the appended claims. It is possible to realize. Accordingly, the above-described embodiments are intended to be illustrative and not limiting, and the present invention is not limited to the details specified herein, and is not limited to the appended claims. Changes can be made within the scope and range of any equivalent form thereof.

1 is a diagram of a standard batch type substrate cleaning system. FIG. It is a top view of a batch type substrate cleaning system. 1 is a schematic diagram of a conventional RF power supply that provides power to one or more transducers. FIG. FIG. 6 is a diagram of a standard transducer 18B. It is the graph which showed the energy distribution in a transducer. 1 illustrates a dynamic single substrate cleaning system in accordance with one embodiment of the present invention. 1 illustrates a dynamic single substrate cleaning system in accordance with one embodiment of the present invention. FIG. 4 is a flowchart illustrating the method steps of an auto-tuning RF generator system used in a megasonic cleaning system, according to one embodiment of the present invention. 1 is a block diagram illustrating an auto-tuning RF generator system in accordance with one embodiment of the present invention. FIG. FIG. 4 is a flowchart illustrating the method steps of a self-tuning RF generator system when an RF generator applies an RF signal to a transducer, in accordance with one embodiment of the present invention. It is explanatory drawing which showed the peak _Vds detector according to one Embodiment of this invention. 5 is a graph showing a waveform of a peak voltage (V _ds ) detected by a peak voltage detector according to an embodiment of the present invention. 1 is a block diagram illustrating an auto-tuning RF generator system in accordance with one embodiment of the present invention. FIG. FIG. 4 is a flowchart illustrating method steps of a self-tuning RF generator system in accordance with an embodiment of the present invention. FIG. It is the graph which showed an example of the relationship between the phase P1 and the phase P2 according to one Embodiment of this invention. It is the graph which showed an example of the relationship between the phase P1 and the phase P2 according to one Embodiment of this invention. It is the graph which showed an example of the relationship between the phase P1 and the phase P2 according to one Embodiment of this invention. 1 is a block diagram illustrating an auto-tuning RF generator system in accordance with one embodiment of the present invention. FIG. FIG. 4 is a flowchart illustrating method steps of a self-tuning RF generator system in accordance with an embodiment of the present invention. FIG. FIG. 2 illustrates a megasonic module according to an embodiment of the present invention. 6 is a graph illustrating energy distribution in a transducer according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Batch type substrate cleaning system 11 ... Tank 12 ... Substrate carrier 14 ... Substrate 15 ... Radiant energy 16 ... Cleaning liquid 17 ... Reflected energy 18A, 18B, 18C ... Transducer 19A, 19B ... Mounting tool 30 ... Voltage controlled oscillator (VCO)
33 ... Signal 34 ... RF generator 35 ... Signal 36 ... Power sensor 38 ... Reflected signal 200 ... Dynamic single substrate cleaning system 202 ... Substrate 204 ... Cleaning fluid 206 ... Cleaning chamber 208A, 208B, 208C ... Edge roller 210 ... Transducer 212 ... RF generator 214 ... acoustic energy 216 ... reflected energy 218 ... active surface 220 ... RF signal 222 ... reflected signal 300 ... auto-tuning RF generator system 302 ... auto-tuning RF generator 306 ... voltage controlled oscillator (VCO)
310 ... VCO RF signal 312 ... DC power supply 314 ... Inductor 320 ... Amplifier 322 ... DC bias rail 324 ... Ground potential rail 326 ... Peak voltage detector 330 ... Load network 332 ... Transducer 340 ... Comparator device 342 ... Voltage divider network 502 , 504 ... Capacitor 506 ... Diode 600 ... Automatic tuning RF generator system 602 ... RF generator 604 ... Phase detector 606 ... First input 608 ... Second input 610, 612 ... Scale changing circuit 900 ... Auto-tuning RF generator system 902 ... Variable DC power supply 904 ... Comparator 906 ... Scale change circuit 1100 ... Megasonic module 1102 ... Substrate processing tank 1104 ... Lid 1106 ... Tank megasonic transducer 1108 ... Lid megasoni 1110... Substrate 1112... Driving wheel 1114... Stabilizing arm / wheel 1116... Driving motor 1118 .. Mechanical coupling 1120.

Claims (33)

A method of dynamically adjusting an RF generator to the instantaneous resonant frequency of a transducer, comprising:
Inputting an RF input signal from an oscillator to the RF generator;
Measuring a first phase of an input voltage of the RF input signal;
Measuring a second phase of a voltage of an RF signal output from the RF generator and coupled to an input of a transducer;
Generating a frequency control signal when the first phase is not equal to the second phase;
Applying the frequency control signal to a frequency control input of the oscillator. The method of claim 1, comprising:
Applying the frequency control signal to a frequency control input of the oscillator comprises combining the frequency control signal with a constant value control signal. The method of claim 1, comprising:
Generating a frequency control signal when the first phase is not equal to the second phase;
If the first phase lags behind the second phase, the frequency control signal decreases the frequency of the oscillator;
If the first phase precedes the second phase, the frequency control signal increases the frequency of the oscillator;
The method, wherein the frequency control signal does not change the frequency of the oscillator if the first phase is equal to the second phase. The method of claim 1, comprising:
The method of measuring the first phase and the second phase and generating the frequency control signal is performed every cycle of the RF input signal. A transducer RF power source,
An oscillator having a frequency control input unit and an RF signal output unit;
An RF generator having an input coupled to the RF signal output of the oscillator; and an RF generator output coupled to the transducer;
A first phase input coupled to the RF signal output of the oscillator; a second phase input coupled to the RF generator output; and the frequency control voltage input of the oscillator. A transducer RF power source comprising: a voltage phase detector having a frequency control signal output coupled thereto. The transducer RF power source of claim 5, comprising:
The transducer RF power source, wherein the frequency control signal output is coupled to the frequency control input of the oscillator through a control amplifier. The transducer RF power supply of claim 6, comprising:
The control amplifier is
A first input coupled to the frequency control signal output;
A second input coupled to the constant value control signal portion;
An output coupled to the frequency control input of the oscillator. The transducer RF power source of claim 5, comprising:
The transducer is a transducer RF power source provided in a megasonic cleaning chamber. A transducer RF power source,
A voltage controlled oscillator (VCO) having a frequency controlled voltage input and an output;
A class E RF generator having an input coupled to the output of the VCO, and an RF generator output coupled to the transducer having a variable impedance;
A first phase input coupled to the output of the VCO; a second phase input coupled to the RF generator output; and the frequency control voltage input of the VCO through a control amplifier. A voltage phase signal output unit coupled to the voltage phase detector,
The control amplifier is coupled to a first input coupled to the voltage control signal output, a second input coupled to a constant value control signal, and the frequency control voltage input of the VCO. A transducer RF power source, comprising: A method for cleaning a substrate, comprising:
Applying an RF signal to a transducer at a frequency f, the transducer facing the substrate to radiate acoustic energy at the frequency f toward the substrate;
Moving the substrate relative to the transducer;
Dynamically adjusting the RF signal to maintain resonance of the acoustic energy. The method of claim 10, comprising:
The method of dynamically adjusting the RF signal to maintain resonance of the acoustic energy includes maintaining a constant voltage of the RF signal applied to the transducer. The method of claim 10, comprising:
An RF generator applies the RF signal to the transducer;
Maintaining the voltage of the RF signal applied to the transducer constant;
Measuring a first voltage of the RF signal;
Comparing the first voltage to a desired voltage target value;
Adjusting the output voltage of the variable DC power supply by inputting a control signal to a variable DC power supply that supplies DC power to the RF generator. The method of claim 10, comprising:
The method of dynamically adjusting the RF signal to maintain resonance of the acoustic energy includes dynamically adjusting a frequency f of the RF signal applied to the transducer. 14. A method according to claim 13, comprising:
The RF signal is applied by an RF generator;
Dynamically adjusting the frequency f of the RF signal applied to the transducer;
Measuring a power supply voltage applied to the RF generator;
Measuring a peak voltage applied to an output amplifier provided in the RF generator;
Generating a frequency control signal when the peak voltage is not equal to the selection ratio of the power supply voltage;
Applying the frequency control signal to a frequency control input of an oscillator that generates the RF signal. 14. A method according to claim 13, comprising:
The RF signal is applied by an RF generator;
Dynamically adjusting the frequency f of the RF signal applied to the transducer;
Inputting an RF input signal from an oscillator to the RF generator and amplifying the RF signal in the RF generator;
Measuring a first phase of an input voltage of the RF input signal;
Measuring a second phase of a voltage of the RF signal output from the RF generator;
Generating a frequency control signal when the first phase is not equal to the second phase;
Applying the frequency control signal to a frequency control input of the oscillator. A cleaning system,
A cleaning chamber comprising a substrate and a transducer facing the substrate, wherein the transducer and the substrate are separated by a variable distance d;
A dynamically adjustable RF generator having an output coupled to the transducer;
A feedback circuit coupled to a control input of the adjustable RF generator. A cleaning system according to claim 16, comprising:
The substrate can rotate;
The distance d varies by about ½ wavelength of the RF signal output from the RF generator as the substrate rotates. A cleaning system according to claim 16, comprising:
The dynamically adjustable RF generator includes a variable DC power source having a control input and a DC output coupled to the RF generator;
The feedback circuit includes: a first input coupled to a constant value control signal; a second input coupled to the RF output of the RF generator; and an adjustable RF generator. And a control signal output unit coupled to the control input unit, the control input unit including a voltage control input unit for the variable DC power supply. A cleaning system according to claim 18,
The dynamically adjustable RF generator is
An oscillator having a control signal input unit and an RF signal output unit;
An output amplifier coupled to the output of the oscillator;
A load network coupled between the output of the output amplifier and the output of the RF generator;
The feedback circuit includes:
A peak voltage detector coupled across the output amplifier;
A third input coupled to the output of the variable DC power source; a fourth input coupled to the output of the peak voltage detector; and the control input of the adjustable RF generator. A second comparator including a second comparator output coupled to the control unit, wherein the control input includes the control signal input of the oscillator. A cleaning system according to claim 18,
The dynamically adjustable RF generator is
An oscillator having a frequency control input unit and an RF signal output unit;
An RF generator input coupled to the RF signal output of the oscillator;
The feedback circuit includes a first phase input coupled to the RF signal output of the oscillator, a second phase input coupled to the RF generator output, and the adjustable RF A cleaning system, comprising: a voltage phase detector including a frequency control signal output coupled to the control input of a generator, wherein the control input includes the frequency control voltage input of the oscillator. A cleaning system according to claim 16, comprising:
The dynamically adjustable RF generator is
A voltage source;
An oscillator having a control signal input unit and an RF signal output unit;
An output amplifier coupled to the output of the oscillator;
A load network coupled between the output of the output amplifier and the output of the RF generator;
The feedback circuit includes:
A peak voltage detector coupled across the output amplifier;
A first input coupled to the voltage source; a second input coupled to the output of the peak voltage detector; and the control input of the adjustable RF generator. And a comparator circuit including: a comparator circuit, wherein the control input includes the control signal input of the oscillator. A cleaning system according to claim 16, comprising:
The dynamically adjustable RF generator is
An oscillator having a frequency control input unit and an RF signal output unit;
An RF generator input coupled to the RF signal output of the oscillator;
The feedback circuit includes a first phase input coupled to the RF signal output of the oscillator, a second phase input coupled to the RF generator output, and the adjustable RF A cleaning system, comprising: a voltage phase detector including a frequency control signal output coupled to the control input of a generator, wherein the control input includes the frequency control voltage input of the oscillator. A method of dynamically adjusting an RF generator to the instantaneous resonant frequency of a transducer, comprising:
Applying an RF input signal from an oscillator to the RF generator;
Measuring a power supply voltage applied to the RF generator;
Measuring a peak voltage in the RF generator;
Generating a frequency control signal when the peak voltage is not equal to the selection ratio of the power supply voltage;
Applying the frequency control signal to a frequency control input of the oscillator. 24. The method of claim 23, comprising:
The method of measuring the peak voltage comprises measuring a peak voltage across an output amplifier provided in the RF generator. 24. The method of claim 23, comprising:
The method wherein the selection ratio of the peak voltage to the power supply voltage is equal to a range from about 3: 1 to about 6: 1. An RF generator,
A voltage source;
An oscillator having a control signal input unit and an RF signal output unit;
An output amplifier coupled to the output of the oscillator;
A load network coupled between the output of the output amplifier and the output of the RF generator;
A peak voltage detector coupled across the output amplifier;
A first input coupled to the voltage source; a second input coupled to the output of the peak voltage detector; and a comparator coupled to the control signal input of the oscillator. And a comparator circuit including an output unit. 27. The RF generator of claim 26, wherein
An RF generator in which a control signal is output from the comparator output unit when the power supply voltage is not equal to the selection ratio of the peak voltage output by the peak voltage detector. An RF generator,
A voltage source;
A voltage controlled oscillator (VCO) having a control voltage input and an output;
An output amplifier coupled to the output of the VCO;
A class E load network coupled between the output of the output amplifier and the output of the RF generator;
A peak voltage detector coupled across the output amplifier;
A first input coupled to the voltage source; a second input coupled to the output of the peak voltage detector; and a comparator coupled to the control voltage input of the VCO. A comparator circuit comprising: an output section; if the peak voltage output by the peak voltage detector and the power supply voltage are not equal to a ratio of about 3.6: 1, control from the comparator output section A comparator circuit from which a signal is output;
An RF generator comprising a transducer coupled to the output of the RF generator. A method of maintaining a constant input voltage to a transducer, comprising:
Applying an RF signal from an RF generator to the transducer;
Measuring a first voltage of the RF signal;
Comparing the first voltage to a desired voltage target value;
Adjusting the output voltage of the variable DC power supply by inputting a control signal to a variable DC power supply that supplies DC power to the RF generator. 30. The method of claim 29, comprising:
The first voltage is a function of the impedance of the transducer, and the impedance of the transducer varies with variations in the distance between the transducer and the target. 30. The method of claim 29, comprising:
Comparing the first voltage with a desired voltage target value includes determining a control signal, the control signal being approximately equal to a difference between the first voltage and the desired voltage target value; Method. A transducer RF power source,
An RF generator having an RF output coupled to the input of the transducer;
A variable DC power supply having a control input and a DC output coupled to the RF generator;
A first input coupled to a constant value control signal, a second input coupled to the RF output of the RF generator, and a voltage control input for the variable DC power source. And a comparator including a control signal output unit. A transducer RF power source,
A class E RF generator having an RF output coupled to the input of the megasonic transducer in a megasonic cleaning chamber;
A variable DC power supply having a control input and a DC output coupled to the RF generator;
A first input coupled to a target value voltage source; a second input coupled to the RF output of the RF generator; and a voltage control input for the variable DC power source. A transducer RF power supply comprising a comparator including a control signal output.

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