JP5759856B2 - Ultrasonic treatment equipment - Google Patents

Description

  The present invention relates to an ultrasonic processing apparatus and an ultrasonic processing method, and for example, relates to a cleaning apparatus and a cleaning method for an object to be processed using ultrasonic waves.

  As background art of this technical field, for example, in Japanese Patent Laid-Open No. 8-243516 (Patent Document 1), an object to be cleaned is immersed in a solution, and a tip portion of an ultrasonic vibration horn is opposed to the object to be cleaned. Is a device for ultrasonic cleaning, in which the transverse dimension 2a of the tip surface of the ultrasonic vibration horn is larger than the wavelength λ in the solution of the applied ultrasonic wave during ultrasonic cleaning. An ultrasonic cleaning device using a horn is described.

  Japanese Patent Application Laid-Open No. 10-309548 (Patent Document 2) supplies a cleaning liquid to a moving object to be cleaned and applies an ultrasonic wave at a predetermined incident angle so as to leak a surface acoustic wave or a leakage plate to the object to be cleaned. An ultrasonic cleaning method is described in which a contaminant is removed from the surface of an object to be cleaned by exciting a wave, a surface acoustic wave or a plate wave.

  Further, JP 2008-085150 A (Patent Document 3) discloses that vacuum deaeration, surfactant contact, and permeability before cleaning with a cleaning solution (chemical solution) in contact with a material to be cleaned (semiconductor substrate). A cleaning method is described in which a surface of a material to be cleaned is degassed by contact with a solution, deaeration using ultrasonic waves, or the like, and a process for improving surface wettability of the material to be cleaned is performed.

JP-A-8-243516 JP-A-10-309548 JP 2008-085150 A

  Patent Documents 1 to 3 describe a cleaning apparatus or a cleaning method using a principle that micron-sized bubbles (cavitation bubbles) are generated in the cleaning liquid when ultrasonic vibration is transmitted to the cleaning liquid.

  The ultrasonic cleaning apparatus of Patent Document 1 and the ultrasonic cleaning method of Patent Document 2 are attached to the surface of an object to be cleaned by a strong liquid flow of the cleaning liquid generated by the movement of the cavitation bubbles such as translation, expansion / contraction and collapse. The removed particulate dust and film dust are removed (washed). However, for example, when a concave / convex pattern having a concave portion width of less than 1 μm and a concave / convex height larger than the concave portion width is formed on the surface of the object to be cleaned, the bottom and side walls of the concave pattern are sufficiently cleaned. It is difficult. Moreover, when the uneven | corrugated pattern with the width | variety of a convex part is less than 1 micrometer, and the height of an unevenness | corrugation is larger than the width | variety of a convex part, it is difficult to suppress destruction (damage) of a convex pattern.

  In the cleaning method of Patent Document 3, cavitation bubbles are continuously generated, and the dissolved gas concentration in the cleaning liquid is reduced to sufficiently clean the bottom and side walls of the concave pattern. However, since deaeration of the liquid with ultrasonic waves takes a long time, it is necessary to increase the output of ultrasonic waves to promote deaeration.However, since the movement of the cavitation bubbles described above is strengthened, damage to the convex pattern is similarly caused. It is difficult to suppress.

  Accordingly, an object of the present invention is to provide an ultrasonic processing apparatus and an ultrasonic processing method capable of suppressing damage to the convex pattern formed on the material to be cleaned and sufficiently cleaning the bottom and side walls of the concave pattern. is there.

A typical configuration of the present invention for solving the above problems is as follows. That is,
An ultrasonic processing apparatus for cleaning an object to be processed with ultrasonic waves,
An ultrasonic vibration part that radiates ultrasonic vibrations;
An oscillating unit for applying electric power to the ultrasonic vibrating unit;
A storage unit that stores the processing object and a processing liquid that processes the processing object, and a processing liquid supply unit that supplies the processing liquid into the storage unit,
The processing liquid supply unit includes a deaeration unit that degass the processing liquid before being supplied into the storage unit.

  According to the present invention, the surface acoustic wave excited on the object to be processed promotes the flow of the process liquid on the surface of the object to be processed, and the treatment liquid is sufficiently applied to the bottom and side walls of the concave pattern of the object to be processed. Penetration and good cleaning results are obtained. In addition, due to a decrease in the concentration of dissolved gas in the treatment liquid, the treatment liquid further penetrates into the bottom and side walls of the concave pattern of the object to be processed, and the amount of cavitation bubbles generated is reduced, resulting in damage to the convex pattern of the object to be processed. Is suppressed. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is an example of composition of an ultrasonic treatment device in an embodiment of the present invention. It is a structural example of the process liquid supply part in embodiment of this invention. It is a flowchart explaining a series of operation | movement of the ultrasonic treatment in embodiment of this invention. The figure which shows the voltage waveform and current waveform which the detection part in embodiment of this invention measures, The graph which shows the state where the phase of a voltage waveform and the phase of a current waveform match, and the amplitude of a current waveform becomes more than predetermined value It is. It is a figure which shows the voltage waveform and current waveform which the detection part in embodiment of this invention measures, and is a graph which shows the state where the phase of a voltage waveform and the phase of a current waveform do not match. It is a figure which shows the voltage waveform and current waveform which the detection part in embodiment of this invention measures, and is a graph which shows the state from which the amplitude of a current waveform is less than predetermined value. It is an example of the data which shows the relationship between the distance from the diaphragm in embodiment of this invention to the main surface of a to-be-processed object, and the electric power value (voltage value x electric current value) which a detection part measures. In the embodiment of the present invention, when the distance from the diaphragm to the main surface of the object to be processed is changed, the intensity (sound pressure) distribution of the ultrasonic vibration in the vicinity of the object to be processed is imaged by the Schlieren method. is there. It is an example of the oscillation waveform of the frequency modulation in the embodiment of the present invention. It is an example of the data which shows the relationship between the modulation width of the frequency in embodiment of this invention, and the electric power value (voltage value x electric current value) which a detection part measures. In the embodiment of the present invention, when the frequency modulation width is changed, the ultrasonic vibration intensity (sound pressure) distribution in the vicinity of the object to be processed is imaged by the Schlieren method. It is an example of the graph which shows the relationship between the dissolved gas concentration in the process liquid in embodiment of this invention, sound pressure, and the damage occurrence frequency with respect to a convex pattern. It is an example of the graph which shows the relationship between the dissolved gas density | concentration in the process liquid in embodiment of this invention, and the time required for a process liquid to reach the bottom part of a concave pattern.

  The ultrasonic processing apparatus according to the present embodiment supplies an excitation unit that excites surface acoustic waves to the object to be processed, and a processing liquid in which the dissolved gas concentration is lowered to a predetermined concentration before the surface of the object to be processed is touched. And a processing liquid supply unit. The excitation unit includes an ultrasonic vibration unit that generates ultrasonic vibration, an oscillation unit that applies power to the ultrasonic vibration unit, and a detection unit that detects voltage and current in the ultrasonic vibration unit. The radiation surface of the ultrasonic vibration unit that radiates ultrasonic vibration is arranged so as to be parallel to the main surface of the object to be processed or at an inclination angle of 10 degrees or less, and the oscillation unit has a voltage phase and a current phase in the detection unit. Are adjusted and the modulation width of the oscillation frequency is changed and adjusted so that the current value is detected at a predetermined value or more.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration example of an ultrasonic processing apparatus according to this embodiment. In the present embodiment, an example of a single-wafer ultrasonic processing apparatus that processes the objects to be processed one by one while pouring a processing liquid over the surface of the object to be processed will be described. In this example, the workpiece W is a semiconductor wafer which is a substrate on which an IC (Integrated Circuit) is formed, for example, and has a disk shape. The workpiece W is subjected to ultrasonic cleaning processing, or cleaning processing and drying processing.
The ultrasonic processing apparatus 100 includes an ultrasonic vibration unit 110, an oscillation unit 120, a detection unit 130, a processing liquid supply unit 140 including a liquid supply pipe 144 and a storage unit 145, which will be described later, a control unit 160, and various types. A storage unit 161 that stores data and the like, an operation unit 162 that receives instructions from an operator, and a display unit 163 that displays various data and the like are provided.

  The ultrasonic vibration unit 110 includes a piezoelectric vibrator 111, a diaphragm 112, a vibrator case 113, and a power feeding cable 114, and has a circular cylindrical appearance when viewed from above as a whole (viewed from above). Have. Each of the piezoelectric vibrator 111 and the diaphragm 112 has a circular disk shape when viewed from above, and the circular main surface is substantially parallel to the circular main surface Wa of the workpiece W or has an inclination angle of 10 degrees. It is arranged to be as follows. Here, the main surface Wa of the workpiece W is a front surface on which irregularities are formed, and indicates the upper surface in FIG. The main surface of the piezoelectric vibrator 111 and the main surface of the diaphragm 112 refer to the lower surface in FIG. The main surface of the diaphragm 112 is a radiation surface 112 a that radiates ultrasonic vibrations into the housing portion 145. The ultrasonic vibration unit 110 translates between the center and the outer periphery of the object to be cleaned W along the main surface Wa of the object to be cleaned, and cleans the rotating object to be cleaned W.

  The piezoelectric vibrator 111 is, for example, a disc-shaped sintered body of zircon lead titanate (PZT), and the main surface thereof is bonded to the back surface of the vibration plate 112 (the surface opposite to the radiation surface 112a). The diameter of the main surface of the piezoelectric vibrator 111 is, for example, 14 mm. The diaphragm 112 is, for example, disk-shaped quartz, and the diameter of the radiation surface 112a is substantially equal to the diameter of the main surface of the piezoelectric vibrator 111. The radiation surface 112a of the vibration plate 112 is in contact with the surface of the processing liquid L and is maintained at a distance of about 3 mm from the main surface Wa of the workpiece W via the processing liquid L. Opposite.

The vibrator case 113 is a cylindrical fluororesin and includes the piezoelectric vibrator 111, the diaphragm 112, and the power supply cable 114. The bottom of the vibrator case 113 is open. At the bottom of the transducer case 113, a flange portion 113a bent inward by 90 degrees from a side wall extending in the vertical direction of the transducer case 113 is provided. The opening diameter of the bottom of the vibrator case 113, that is, the opening diameter of the flange portion 113 a is smaller than the diameter of the diaphragm 112.
The peripheral portion of the radiating surface 112a is placed on the upper portion of the flange portion 113a, and the diaphragm 112 is firmly fixed by an adhesive, packing, or the like. Thereby, the quartz diaphragm 112 is in contact with the processing liquid L, but the piezoelectric vibrator 111 containing a metal component is not in contact with the processing liquid L. Therefore, the metal of the workpiece W caused by the piezoelectric vibrator 111. Contamination can be suppressed.
A portion other than the peripheral edge portion on the radiation surface 112 a of the vibration plate 112 is exposed at the opening at the bottom of the vibrator case 113. The feeding cable 114 has one end connected to the piezoelectric vibrator 111 and the other end connected to the oscillation unit 120.

  The oscillating unit 120 applies an electrical signal (high frequency power) having a frequency of 250 kHz or more and a predetermined voltage amplitude to the piezoelectric vibrator 111 via the power supply cable 114. Here, the reason why the frequency is set to 250 kHz or more is to make it easy to adjust the intensity of surface acoustic wave vibration of the workpiece W by setting the half wavelength in the processing liquid L to 3 mm or less.

  The piezoelectric vibrator 111 to which the high frequency power is applied vibrates and contracts in the thickness direction (vertical direction) of the piezoelectric vibrator 111 at the same frequency as the applied high frequency power. The vibration of the piezoelectric vibrator 111 propagates to the diaphragm 112 and is radiated from the radiation surface 112a of the diaphragm 112 through the treatment liquid L to the workpiece W as ultrasonic vibration. When the power value of the high-frequency power output from the oscillating unit 120 is increased, the sound pressure amplitude of the ultrasonic vibration radiated from the diaphragm 112 increases.

  The detection unit 130 is connected to the power supply cable 114 via the branch cable 114 a, and acquires and measures time-dependent data of the voltage value and current value of the power applied from the oscillation unit 120 to the piezoelectric vibrator 111. When ultrasonic vibration is applied to the workpiece W at an optimal frequency, the ultrasonic vibration propagates in a direction along the main surface Wa of the workpiece W (a direction parallel to the main surface Wa) ( The surface acoustic wave) and the transmitted component that is transmitted to the back surface (surface opposite to the main surface Wa) of the workpiece W in the direction perpendicular to the main surface Wa of the workpiece W are strengthened. At this time, the reflected wave component reflected from the main surface Wa of the workpiece W to the diaphragm 112 is weakened, and the piezoelectric vibrator 111 vibrates strongly with a reduced mechanical load due to the reflected wave. Therefore, the detection unit 130 measures the temporal change of the voltage value and the current value so that the voltage value and the current phase are matched and the current value is increased. By using the above principle, it is possible to observe the strength of the surface acoustic wave of the workpiece W.

  FIG. 2 is a configuration example of the processing liquid supply unit 140 in the present embodiment. The processing liquid supply unit 140 supplies the processing liquid L to the main surface Wa and the back surface of the workpiece W. The processing liquid supply unit 140 accommodates the temperature control (temperature adjustment) tank 141 that temporarily stores the processing liquid L and raises it to a predetermined temperature, a vacuum degassing unit 143, the workpiece W, and the processing liquid L. The container 145 where ultrasonic treatment is performed, the supply pipe 142 for supplying the processing liquid L from the temperature control tank 141 to the vacuum degassing part 143, and the processing liquid L from the vacuum degassing part 143 to the container 145 The liquid supply pipe 144 is provided. The accommodating portion 145 has a circular disk shape when viewed from above.

The ceiling of the temperature control tank 141 is opened, and the atmosphere inside the temperature control tank 141 leads to the atmosphere outside the temperature control tank 141. The temperature adjustment tank 141 includes, for example, a resistance heater (not shown) outside the temperature adjustment tank 141 or inside the wall of the temperature adjustment tank 141, and is heated and degassed by heating the processing liquid L with this heater. It is the qi. The temperature adjustment tank 141 includes a temperature detector (not shown) that detects the temperature of the processing liquid L in the temperature adjustment tank 141, and a temperature detection signal from the temperature detector is output to the control unit 160. Is done. Based on the temperature detection signal from the temperature detector, the control unit 160 controls the heating condition of the heater of the temperature adjustment tank 141 and adjusts the temperature of the processing liquid L in the temperature adjustment tank 141 to a predetermined temperature.
When the processing liquid L is heated, the saturated dissolution concentration of the gas in the processing liquid L is reduced, so that removal of the gas contained in the processing liquid L, that is, degassing of the processing liquid L is promoted.
The processing liquid L heated in the temperature control tank 141 is supplied to the vacuum degassing unit 143 through the liquid supply pipe 142.

  The vacuum degassing unit 143 puts the ambient atmosphere in contact with the processing liquid L into a vacuum state. The vacuum degassing unit 143 includes a vacuum pump (not shown) that reduces the ambient atmosphere in contact with the processing liquid L and a pressure detector (not shown) that detects the pressure value of the ambient atmosphere in contact with the processing liquid L. The pressure detection signal from the pressure detector is output to the control unit 160. Based on the pressure detection signal from the pressure detector, the control unit 160 controls the pressure reduction state of the pressure reduction deaeration unit 143 and adjusts the pressure of the atmosphere in contact with the processing liquid L to a predetermined pressure. The vacuum degassing unit 143 also reduces the saturated dissolution concentration of the gas in the processing liquid L, so that the degassing of the processing liquid L is promoted.

Note that the temperature control tank 141 and the decompression deaeration unit 143 shown in FIG. 2 may be integrated, for example, the atmosphere in contact with the processing liquid L in the temperature control tank 141 may be reduced.
Further, a degassing unit for degassing the processing liquid L in the processing liquid supply unit 140 is added to the above-described heating degassing unit (temperature control tank) 141 and the vacuum degassing unit 143, and the processing liquid L is added using ultrasonic waves. It can also comprise from the ultrasonic deaeration part to deaerate. In this case, the ultrasonic deaeration unit is arranged in series with the heating deaeration unit 141 and the vacuum deaeration unit 143.
Moreover, the deaeration part in the process liquid supply part 140 can also be comprised only in any one of the heating deaeration part 141, the pressure reduction deaeration part 143, and an ultrasonic deaeration part, or arbitrary combinations. The degassing unit is configured by any two or more combinations. For example, as in the present embodiment, the degassing unit is configured by combining the heating degassing unit 141 and the vacuum degassing unit 143, thereby processing liquid. The time required for degassing L can be shortened.

The processing liquid L whose dissolved gas concentration is lowered to a concentration lower than a predetermined concentration by the temperature control tank 141 and the vacuum degassing unit 143 is connected to the main surface Wa of the workpiece W in the storage unit 145 via the liquid supply pipe 144. Supplied on the back side. At this time, a liquid film of the processing liquid L is formed in the gap between the main surface Wa of the workpiece W and the radiation surface 112a of the diaphragm 112. Further, since the processing liquid L is also supplied to the back surface of the workpiece W having no uneven pattern, the transmission of ultrasonic vibrations in the workpiece W is promoted, and the vibration plate 112 extends from the main surface Wa of the workpiece W. It is possible to weaken the reflected wave component reflected to the surface.
In the present embodiment, the processing liquid L is supplied to both the main surface Wa and the back surface of the workpiece W in the container 145, but the processing liquid L is supplied to the main surface Wa of the workpiece W in the container 145. It is also possible to have a configuration that supplies only to

  In the accommodating part 145, the to-be-processed object W is rotating in the horizontal direction at about 100 rpm, for example. Accordingly, the processing liquid L supplied from the liquid supply pipe 144 into the storage unit 145 is discharged out of the storage unit 145 from the drainage unit 145 a provided at the horizontal end of the storage unit 145. Thus, the main surface Wa and the entire back surface of the workpiece W are cleaned by the surface acoustic wave propagating in the direction along the main surface Wa of the workpiece W and the processing liquid L supplied into the container 145. Then, the processing liquid L containing dust or the like used for the cleaning is discharged from the drainage part 145a.

The control unit 160 is signal-connected to each component of the ultrasonic processing apparatus 100, that is, the ultrasonic vibration unit 110, the oscillation unit 120, the detection unit 130, the processing liquid supply unit 140, and the like. The detection signal is received, and instructions are given to each component.
When the operation unit 162 receives an ultrasonic processing start instruction from the operator, the control unit 160 issues an ultrasonic processing start instruction to the oscillation unit 120, the processing liquid supply unit 140, and the like.
Further, the control unit 160 receives the temperature detection signal from the temperature control tank 141, and controls the temperature of the processing liquid L in the temperature control tank 141 to a predetermined temperature based on the received temperature detection signal.
In addition, the control unit 160 receives a pressure detection signal from the decompression deaeration unit 143, and controls the pressure of the atmosphere in the decompression deaeration unit 143 to a predetermined pressure based on the received pressure detection signal.
As a hardware configuration, the control unit 160 includes a CPU (Central Processing Unit) and a memory for storing an operation program of the control unit 160, and the CPU operates according to the operation program.

Next, ultrasonic processing in the ultrasonic processing apparatus 100 will be described with reference to FIG. FIG. 3 is a flowchart for explaining a series of processing operations in the ultrasonic processing apparatus 100.
First, when the operation unit 162 receives a processing start instruction from the operator, the control unit 160 instructs the oscillation unit 120 to start processing. Oscillating unit 120 receives an instruction processing start from the control unit 160 (S301), it starts the generation of the high frequency power at a predetermined voltage amplitude _{v 0} and a predetermined frequency _{f 0} (S302). Appropriate values of the voltage amplitude v ₀ and the frequency f ₀ have been confirmed by experiments and the like, and are stored in advance in the storage unit 161 via the operation unit 162 by the operator. The control unit 160 reads out processing data such as a voltage amplitude v ₀ and a frequency f ₀ stored in the storage unit 161 and a predetermined value I ₀ ′ of a current amplitude described later, and transmits the processing data to the oscillation unit 120 at the start of processing. To do.

Next, the oscillation unit 120 causes the detection unit 130 to start measurement (S303). The detection unit 130 acquires time-dependent data (waveform data) of the voltage value V and the current value I of the power applied to the piezoelectric vibrator 111 (S304), and the voltage waveform phase θ _V and the current waveform phase θ _I. Is matched (S305).
When the phase θ _V and the phase θ _I match (Yes in S305), the detection unit 130 further diagnoses whether the amplitude I _{0 of the} current waveform is equal to or greater than a predetermined value I ₀ ′ (S306). When the amplitude I ₀ is equal to or greater than the predetermined value (Yes in S306), the process proceeds to Step S308 described later. The predetermined value I ₀ ′ has been confirmed by an experiment or the like as an appropriate value, and is stored in advance in the storage unit 161 via the operation unit 162 by the operator. The detection unit 130 receives the predetermined value I ₀ ′ from the oscillation unit 120 at the start of processing.

On the other hand, when the phase θ _V and the phase θ _I do not match (No in S305), or when the amplitude I ₀ is less than a predetermined value (No in S306), the detection unit 130 is compared with the oscillation unit 120. A command is issued to change the frequency of the output power (S307). Specifically, the content of the command is to perform frequency modulation in a predetermined frequency range f ₀ −Δf to f ₀ + Δf with the voltage amplitude v ₀ maintained constant.
When the phase θ _V and the phase θ _I do not match in the modulation width of Δf or the amplitude I ₀ is less than a predetermined value (No in S305 or S306), the detection unit 130 sets the phase θ _V to the oscillation unit 120. Until the phase θ _I is matched and the amplitude I ₀ becomes equal to or greater than a predetermined value, the modulation width Δf is reset to the change value and frequency modulation is performed (S307). In the flow of FIG. 3, S304 to S308 are repeated until the phase θ _V and the phase θ _I are matched and the amplitude I ₀ becomes equal to or greater than a predetermined value, but the transition is made from S307 to S304, and S304 to S307 are repeated. May be.
Appropriate values for the initial value and change value of the modulation width Δf have been confirmed by experiments and the like, and are stored in advance in the storage unit 161 via the operation unit 162 by the operator. The oscillation unit 120 receives an initial value or a change value of the modulation width Δf from the control unit 160 at the start of processing.

For example, when the phase θ _V and the phase θ _I do not match (No in S305) or the amplitude I ₀ is less than a predetermined value (No in S306), Δf = 10 kHz at the beginning, that is, the frequency range f ₀ −10 kHz to f _0. + 10 kHz in to frequency modulation (S307), acquires the time course data of the voltage V and current I (S304), satisfy the processing conditions amplitude _{I 0} phase theta _V and the phase theta _I are matched is not less than a predetermined value (S305 and S306) and if the processing condition is satisfied (Yes in S305 and S306), frequency modulation in the frequency range f ₀ -10 kHz to f ₀ +10 kHz is continued. If the above processing conditions are not satisfied (No in S305 or S306), Δf = 20 kHz, that is, frequency modulation is performed in the frequency range f ₀ -20 kHz to f ₀ +20 kHz (S307), and the temporal change data of the voltage value V and current value I Is obtained (S304), and whether or not the above processing conditions are satisfied is diagnosed (S305 and S306). If the above processing conditions are satisfied (Yes in S305 and S306), the frequency range f ₀ -20 kHz to f _{0 is obtained.} Continue frequency modulation at +20 kHz. When the above processing conditions are not satisfied (No in S305 or S306), Δf = 30 kHz, that is, frequency modulation is performed in the frequency range f ₀ -30 kHz to f ₀ +30 kHz (S307), and the time-dependent change data of the voltage value V and current value I (S304), and whether or not the above processing conditions are satisfied is diagnosed (S305 and S306). If the above processing conditions are satisfied (Yes in S305 and S306), the frequency range f ₀ -30 kHz to f _{0 is obtained.} Continue frequency modulation at +30 kHz.

In this manner, the oscillation unit 120 generates high-frequency power while automatically repeating the adjustment for changing the modulation width Δf until the phase θ _V and the phase θ _I are matched and the amplitude I ₀ reaches a predetermined value or more. The detection unit 130 continues to measure the voltage value V and the current value I.
In a certain modulation width Δf, when the phase θ _V and the phase θ _I are matched and the amplitude I ₀ reaches a predetermined value or more, the oscillation unit 120 matches the phase θ _V and the phase θ _I and the amplitude I ₀ is predetermined. The frequency modulation in the frequency range f ₀ −Δf to f ₀ + Δf is continued using the modulation width Δf reaching the value or more.

The power output from the oscillation unit 120 is continuously frequency-modulated in a predetermined frequency range f ₀ −Δf to f ₀ + Δf, so that the phase θ _V and the phase θ _I do not match or the amplitude I ₀ is predetermined. Although a state of a frequency that is less than the value may occur intermittently, as a whole, a state in which the phase θ _V and the phase θ _I are matched and the amplitude I ₀ is a predetermined value or more is maintained. As described above, when frequency modulation is continuously performed in the frequency range f ₀ −Δf to f ₀ + Δf, the distance between the main surface Wa of the workpiece W and the radiation surface 112a of the vibration plate 112 is set to be equal to that of the workpiece W. Even if the state where the phase θ _V and the phase θ _I do not match or the state where the amplitude I ₀ is less than the predetermined value due to the variation in the distance as described above varies with the rotation, It is easy to maintain a state where the phase θ _V and the phase θ _I are matched and the amplitude I ₀ is equal to or greater than a predetermined value. The state in which the phase θ _V and the phase θ _I are matched as a whole and the amplitude I ₀ is equal to or greater than a predetermined value is, for example, that the phase θ _V and the phase θ _I are matched and the amplitude I _{0 in} one period of frequency modulation. Is a state in which the phase ratio of the phase θ _V and the phase θ _I do not match or is larger than the time ratio of the state in which the amplitude I ₀ is less than the predetermined value. Similarly, the diagnosis in steps S305 and S306 described above is also performed based on the time ratio that one phase of frequency modulation occupies when the phase θ _V and the phase θ _I are matched and the amplitude I ₀ is equal to or greater than a predetermined value. Is.

  Next, after diagnosing Yes in step S306 or after executing step S307, the oscillation unit 120 checks whether or not there is an instruction to stop processing from the control unit 160 (S308). For example, the control unit 160 reads out the ultrasonic processing time stored in advance in the storage unit 161, and instructs to stop the processing when the ultrasonic processing time is reached. Alternatively, the control unit 160 issues a process stop instruction in accordance with an operator stop instruction input from the operation unit 162. As a result of checking, if there is no instruction to stop the process (No in S308), the process returns to the step of S304, and the series of processes of steps S304 to S308 is continued. On the other hand, when there is an instruction to stop processing (Yes in S308), the oscillation unit 120 stops the generation of high-frequency power (S309) and causes the detection unit 130 to stop measurement (S310). Thus, a series of ultrasonic processing operations is completed.

In the above description, the oscillation unit 120 instructs the detection unit 130 to acquire data of the voltage value V and the current value I applied to the piezoelectric vibrator 111, and the detection unit 130 detects the phase θ _{V of the} voltage waveform and the current waveform. whether phase theta _I are matched in amplitude I ₀ of the current waveform was made to diagnose whether a predetermined value or more. However, the control unit 160 instructs the detection unit 130 to acquire data of the voltage value V and the current value I applied to the piezoelectric vibrator 111, and the voltage value V applied to the piezoelectric vibrator 111 acquired by the detection unit 130. Based on the data of the current value I and the current value I, the control unit 160 diagnoses whether the phase θ _V of the voltage waveform matches the phase θ _I of the current waveform and whether the amplitude I _{0 of the} current waveform is equal to or greater than a predetermined value. May be.

In the above description, in step S307, the power output from the oscillating unit 120 is continuously frequency-modulated in a predetermined frequency range f ₀ −Δf to f ₀ + Δf, and the phase θ _V and the phase θ _I are The frequency modulation is continued even after the matching and the amplitude I ₀ becomes a predetermined value or more. In this way, even when the distance between the main surface Wa of the workpiece W and the radiation surface 112a of the diaphragm 112 varies as the workpiece W rotates, the phase θ as a whole is increased. It becomes easy to maintain a state where _V and phase θ _I are matched and amplitude I ₀ is equal to or greater than a predetermined value.

However, instead of as described above, simply by changing the frequency of the power oscillation unit 120 outputs, for example, monotonically changing from f ₀ -.DELTA.f to f _{0 +} Delta] f, the phase theta _V and the phase theta _I Are matched and the amplitude I ₀ becomes a predetermined value or more, the frequency at that time may be continued. In this way, when the distance between the main surface Wa of the workpiece W and the radiation surface 112a of the diaphragm 112 does not vary much during the rotation of the workpiece W, the phase θ _V and the phase θ It is possible to continuously maintain a state where _I is matched and the amplitude I ₀ is equal to or greater than a predetermined value.

FIG. 4 is an example of data indicating the voltage waveform V and the current waveform I measured by the detection unit 130. The phase θ _V of the voltage value V matches the phase θ _I of the current value I, and the amplitude I ₀ is a predetermined value. It is in a state of I ₀ 'or higher. The horizontal axis is time t. In FIG. 4, for example, π / 2 of the phase θ _V and π / 2 of the phase θ _I coincide on the time axis, and it can be seen that the voltage and the current are matched. In this state, the oscillation unit 120 continues the steps S304 to S306 and S308 until there is an input to stop processing.

Figure 5 shows an example of data indicating a voltage waveform V and the current waveform I to the detection unit 130 is measured, the phase theta _I phase theta _V and the current value I of the voltage value V is a state of not matching. In Figure 5, for example, [pi / 2 phase theta _V of [pi / 2 and the phase theta _I are shifted on the time axis, it can be seen that the voltage and current do not match. In this state, the oscillation unit 120 starts frequency modulation based on the step of S307.

FIG. 6 is an example of data indicating the voltage waveform V and the current waveform I measured by the detection unit 130. The phase θ _V of the voltage value V and the phase θ I of the current value _I are matched, but the amplitude I ₀ is The state is less than the predetermined value I ₀ ′. Even in this state, the oscillation unit 120 starts frequency modulation based on the step of S307.

  The state shown in FIG. 5 or 6 appears when the incident wavelength λ of ultrasonic vibration in the processing liquid L is appropriate for the distance from the radiation surface 112a of the diaphragm 112 to the main surface Wa of the workpiece W. Because it is not. In this case, the ultrasonic vibration is performed based on the step of S307 so that the oscillation unit 120 can obtain the optimum wavelength λ ′ with respect to the distance from the radiation surface 112a of the vibration plate 112 to the main surface Wa of the workpiece W. The adjustment of the modulation width Δf of the frequency, that is, the frequency of the high frequency power is repeated.

FIG. 7 shows data indicating the relationship between the distance z from the radiation surface 112a of the diaphragm 112 to the main surface Wa of the workpiece W and the power value p (voltage value V × current value I) measured by the detection unit 130. It is an example. The treatment liquid L is water, the workpiece W is a silicon wafer having a thickness of 0.7 mm and a diameter of 200 mm, and the frequency f ₀ is fixed at 1232 kHz. The wavelength λ of the ultrasonic vibration in the processing liquid L at a frequency of 1232 kHz is λ≈1.2 mm.
In FIG. 7, it can be seen that the power value p increases when the distance z is (8/4) λ and (10/4) λ.

FIG. 8 shows the intensity (sound pressure) of ultrasonic vibration when the wavelength λ of the ultrasonic vibration is constant and the distance z from the radiation surface 112a of the diaphragm 112 to the main surface Wa of the workpiece W is changed. It is an example of the result of having imaged distribution by the schlieren method. Similar to the configuration of FIG. 1, the ultrasonic vibration unit 110 and the workpiece W are immersed and observed in a tank in which the processing liquid L (water) is stored. A location indicated by a dotted line indicates the position of the ultrasonic vibration unit 110, and a location indicated by an arrow indicates the position of the workpiece W.
8A shows a case where z = 2.4 mm = (8/4) λ, FIG. 8B shows a case where z = 2.7 mm = (9/4) λ, and FIG. , Z = 3.0 mm = (10/4) λ, FIG. 8D shows the case where z = 3.3 mm = (11/4) λ.
8 (a) and 8 (c), that is, when the distance z is (8/4) λ and (10/4) λ, the direction along the main surface Wa of the workpiece W is wide. A brightening state is observed across the area. This is a state where the sound pressure of the ultrasonic vibration is increasing. 8B and 8D, that is, when the distance z is (9/4) λ and (11/4) λ, the direction along the main surface Wa of the workpiece W A darkening state is observed. This is a state where the sound pressure of the ultrasonic vibration is lowered.

According to FIGS. 7 and 8, when the distance z is an even multiple of λ / 4, the power value p increases, and the sound pressure is increased over a wide region in the direction along the main surface Wa of the workpiece W. Increase. This means that the surface acoustic wave is strengthened on the main surface Wa of the workpiece W, while the mechanical load of the reflected wave on the piezoelectric vibrator 111 is reduced. On the other hand, when the distance z is an odd multiple of λ / 4, the power value p decreases, and the sound pressure decreases in the direction along the main surface Wa of the workpiece W. This means that the surface acoustic wave is weakened on the main surface Wa of the workpiece W, while the mechanical load of the reflected wave on the piezoelectric vibrator 111 is increased.
Thus, by setting the distance z to an appropriate value with respect to the wavelength λ of the ultrasonic vibration, the surface acoustic wave can be strengthened and the sound pressure of the ultrasonic vibration can be increased.

FIG. 9 is an example of an oscillation waveform of frequency modulation performed by the oscillation unit 120, which is executed in step S307 of FIG. The voltage amplitude v ₀ is constant, but the frequency continuously changes with the period T in the range of f ₀ −Δf to f ₀ + Δf. The frequency modulation shown in FIG. 9 is performed when the phase θ _{V of the} voltage waveform applied to the piezoelectric vibrator 111 does not match the phase θ _I of the current waveform or the amplitude I _{0 of the} current waveform is not equal to or greater than a predetermined value. 3 is started using the initial value of Δf. Even if the initial value of Δf is used, the phase θ _{V of the} voltage waveform applied to the piezoelectric vibrator 111 does not match the phase θ _{I of the} current waveform, or If the amplitude I _{0 of the} current waveform is not greater than or equal to the predetermined value, the value of Δf is reset at S307 in FIG. An appropriate value of the period T has been confirmed by experiments or the like, and is stored in advance in the storage unit 161 via the operation unit 162 by the operator. The oscillation unit 120 receives the value of the period T from the control unit 160 at the start of processing. The period T is constant in the example of FIG. 9, but may be changed.

FIG. 10 is an example of data indicating the relationship between the frequency modulation width Δf and the power value p (voltage value × current value) measured by the detection unit 130. As in FIG. 7, the treatment liquid L is water, the workpiece W is a silicon wafer having a thickness of 0.7 mm and a diameter of 200 mm, and the frequency f ₀ is fixed at 1232 kHz (wavelength λ≈1.2 mm). The distance z is 2.7 mm.
FIG. 10 shows that the power value p becomes the largest when Δf = 30 kHz.

FIG. 11 shows an example of the result of imaging the ultrasonic vibration intensity (sound pressure) distribution by the Schlieren method when the modulation width Δf of the ultrasonic vibration frequency is changed under the same conditions as in FIG. Similar to FIG. 8, the ultrasonic vibration unit 110 and the workpiece W are immersed and observed in a tank in which the processing liquid L (water) is stored. A location indicated by a dotted line indicates the position of the ultrasonic vibration unit 110, and a location indicated by an arrow indicates the position of the workpiece W.
11A shows a case where Δf = 0 kHz, FIG. 11B shows a case where Δf = 10 kHz, FIG. 11C shows a case where Δf = 20 kHz, and FIG. 11D shows a case where Δf = 30 kHz. In the case of FIG. 11D, that is, in the case of Δf = 30 kHz, a bright state is observed over a wide area in the direction along the main surface Wa of the workpiece W, and the sound pressure of ultrasonic vibration increases. I understand that

  The wavelength λ of the ultrasonic vibration in the processing liquid L is calculated by λ = c / f. c is a propagation velocity of ultrasonic vibration in the processing liquid L, and is about 1478 m / s. f is the frequency of ultrasonic vibration in the processing liquid L. Therefore, when Δf = 0 kHz, λ≈1.2 mm, and when Δf = 30 kHz, λ≈1.17 mm. Since the distance z is 2.7 mm, when Δf = 0 kHz, z≈2, 25λ≈ (9/4) λ, and when Δf = 30 kHz, z≈2.3λ ≠ (9/4) λ, An odd multiple of λ / 4 (a state in which the surface acoustic wave is weakest) can be avoided.

10 and 11, the power value p increases at the modulation width Δf = 30 kHz, and the sound pressure increases over a wide area in the direction along the main surface Wa of the workpiece W. This means that the surface acoustic wave is strengthened on the main surface Wa of the workpiece W, while the mechanical load of the reflected wave on the piezoelectric vibrator 111 is reduced.
Thus, when the distance z is constant, the surface acoustic wave can be strengthened and the sound pressure of the ultrasonic vibration can be increased by setting the modulation width Δf of the frequency of the ultrasonic vibration to an appropriate value.

Figure 12 is a dissolved gas concentration C ₀ of the processing liquid L, and the sound pressure amplitude P _a of the ultrasonic vibration, for example, the relationship between the damage occurrence frequency F for projecting the pattern formed on the main surface Wa of the workpiece W It is an example of the data which shows. The treatment liquid L is water at 25 ° C., and the dissolved gas is nitrogen. Incidentally, the saturated solubility concentration _{C S} of nitrogen to 25 ° C. water is about 18 ppm.

With increasing the dissolved gas concentration C _0, the sound pressure amplitude P _a is reduced. This is presumably because when the dissolved gas concentration C ₀ increases, the amount of bubbles generated increases, which prevents the propagation of sound waves. The dissolved gas concentration C ₀ is 0 to 1ppm vicinity, sound pressure amplitude P _a is the maximum, therefore, the flow of the treatment liquid L is most active state.
Meanwhile, the damage occurrence frequency F, the dissolved gas concentration C ₀ is most near 8 ppm, and decreased by the reduction in the generation amount of cavitation bubbles is lower than this concentration in the region, reduction of the sound pressure amplitude P _a in a high concentration in the region It decreases by weakening the movement of the cavitation bubble.
Thus, as the dissolved gas concentration C ₀ to less than 8 ppm, while the damage occurrence frequency F is decreased, it can be seen that the flow of the treatment liquid L becomes higher. Furthermore, if it is less than 1 ppm, the damage occurrence frequency F can be eliminated.

FIG. 13 shows the dissolved gas concentration C ₀ in the processing liquid L and the time required for the processing liquid L to reach the bottom of the concave pattern formed on the main surface Wa of the workpiece W (liquid intrusion time τ). It is an example of the graph which shows these relationships. Similar to FIG. 10, the treatment liquid L is water at 25 ° C., and the dissolved gas is nitrogen.
By 13, by reducing the dissolved gas concentration C _0, the processing liquid L is found to reach to the bottom of the concave pattern in a short time. Therefore, lowering the dissolved gas concentration C _0, with respect to the concave pattern, it can be seen that a short time with good cleaning results are obtained.

  When it is assumed that the concave pattern is a cylindrical deep hole, the liquid intrusion time τ can be roughly estimated by the following theoretical calculation formula.

Ｄ：処理液Ｌ中における溶存気体の拡散係数
Ｃ_Ｓ：処理液Ｌに対する気体の飽和溶解濃度
Ｃ_０：処理液Ｌ中の溶存気体濃度
ｈ：凹凸の高さ（凹パターンの深さ）
ｄ：凹パターンの直径
θ：被処理物Ｗに対する処理液Ｌの接触角
σ：処理液Ｌの表面張力
Ｐ_ｗ：処理液Ｌの圧力
Ｐ_ｖ：処理液Ｌの蒸気圧

D: Diffusion coefficient of dissolved gas in treatment liquid L C _S : Saturated dissolved concentration of gas in treatment liquid L C ₀ : Dissolved gas concentration in treatment liquid L h: Height of irregularities (depth of concave pattern)
d: Diameter of concave pattern θ: Contact angle of treatment liquid L to workpiece W σ: Surface tension of treatment liquid L P _w : Pressure of treatment liquid L P _v : Vapor pressure of treatment liquid L

In the above description, the processing liquid L is assumed to be water, and an embodiment has been described in which damage to the convex pattern is suppressed and the bottom and side walls of the concave pattern can be sufficiently cleaned. However, the treatment liquid L may be a highly volatile chemical liquid such as ethanol, isopropyl alcohol, or hydrofluoroether. Even when these chemical solutions are used, the dissolved gas concentration C ₀ is reduced to, for example, less than 1 ppm, and then supplied to the main surface of the workpiece W, as in the case where the processing solution L is water. It is possible to suppress damage to the convex pattern and sufficiently clean the bottom and side walls of the concave pattern. Furthermore, filling the concave pattern with the above highly volatile chemical solution shortens the drying time after cleaning, and also suppresses the phenomenon that the convex pattern is pulled by the surface tension of the processing liquid L and collapses. It becomes possible. This is because the surface tension of the highly volatile chemical solution is smaller than that of water.

According to the embodiment described above, at least the following effects (1) to (9) are obtained.
(1) The surface acoustic wave excited by the object to be processed promotes the flow of the process liquid on the surface of the object to be processed, and the treatment liquid sufficiently penetrates into the bottom and side walls of the concave pattern of the object to be processed. Good cleaning results can be obtained.
(2) Due to the decrease in the concentration of dissolved gas in the processing liquid, the processing liquid further penetrates into the bottom and side walls of the concave pattern of the object to be processed, and the amount of cavitation bubbles generated is reduced. Damage is suppressed.
(3) The frequency of the power is changed so that the phase of the voltage value of the power applied to the ultrasonic vibration unit and the phase of the current value match each other and the current value is equal to or greater than a predetermined value. The treated product can be washed.
(4) Since the phase of the voltage value of the power applied to the ultrasonic vibration unit and the phase of the current value are matched with each other, and the frequency of the power is periodically changed so that the current value becomes a predetermined value or more, Even in the case where the distance between the workpiece and the diaphragm varies with the rotation of the workpiece, as a whole, the phase of the voltage value and the phase of the current value are matched with each other, and the current value is It becomes easy to maintain a state of a predetermined value or more.
(5) In the above (4), since the voltage value phase and the current value phase are matched with each other and the range of the frequency to be changed (modulation width) is changed until the current value becomes a predetermined value or more, the voltage value And the phase of the current value are matched with each other, and the current value can be easily set to a predetermined value or more.
(6) The radiation surface of the ultrasonic vibration unit is disposed so as to face the main surface on which the unevenness of the object to be processed is formed, and the space between the radiation surface and the main surface is filled with the degassed processing liquid. Therefore, the object to be processed can be cleaned efficiently.
(7) Since the degassing unit is configured by combining the heated degassing unit and the vacuum degassing unit, the time required for degassing the processing liquid can be shortened.
(8) Since the processing liquid is also supplied to the back surface of the object to be processed, it is possible to promote the transmission of ultrasonic vibrations in the object to be processed and weaken the reflected wave component from the main surface of the object to be processed. .
(9) When the treatment liquid is configured to contain any one or more of alcohols, ethers, and fluorinated solvents, the time required for the drying treatment after washing can be shortened.

  In addition, this invention is not limited to above-described embodiment, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described.

  In addition, each configuration, function, processing unit, processing unit, and the like of the above-described embodiments may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by interpreting and executing a program that realizes each function by the processor. Information such as programs, tables, and files for realizing each function is stored in a recording device such as a semiconductor memory, a hard disk, an SSD (Solid State Drive), or an IC card, an SD (Secure Digital) card, a DVD (Digital Versatile Disk). Etc. can be placed on a recording medium.

  In addition, the control lines and information lines in the drawings of the above-described embodiments are those that are considered necessary for explanation, and do not necessarily indicate all the control lines and information lines on the product. Actually, it may be considered that almost all the components are connected to each other.

  DESCRIPTION OF SYMBOLS 100 ... Ultrasonic processing apparatus, 110 ... Ultrasonic vibration part, 111 ... Piezoelectric vibrator, 112 ... Diaphragm, 112a ... Radiation surface, 113 ... Vibrator case, 113a ... Flange part, 114 ... Feeding cable, 114a ... Branch cable , 120 oscillating unit, 130 detecting unit, 140 processing liquid supply unit, 141 temperature control tank (heat deaeration unit), 142 liquid supply pipe, 143 decompression deaeration unit, 144 liquid supply pipe, 145 DESCRIPTION OF SYMBOLS ... Storage part, 145a ... Drainage part, 160 ... Control part, 161 ... Memory | storage part, 162 ... Operation part, 163 ... Display part, W ... To-be-processed object, Wa ... To-be-processed object main surface, L ... Processing liquid.

Claims (1)

An ultrasonic processing apparatus for cleaning an object to be processed with ultrasonic waves,
An ultrasonic vibration part that radiates ultrasonic vibrations;
An oscillating unit for applying electric power to the ultrasonic vibrating unit;
A treatment liquid supply part for containing the treatment object and a treatment liquid for treating the treatment object, and supplying the treatment liquid into the accommodation part;
A detection unit that measures a voltage value and a current value of power applied from the oscillation unit to the ultrasonic vibration unit, and
A radiation surface for radiating ultrasonic vibrations in the ultrasonic vibration part is disposed so as to face a main surface on which irregularities of the object to be processed housed in the housing part are formed,
The processing liquid supply unit includes a deaeration unit that degass the processing liquid before being supplied into the storage unit, and the main surface of the object to be processed stored in the storage unit and the main surface Supply the processing liquid degassed by the degassing part to the back surface ,
The oscillation unit cycles the frequency of the power output by the oscillation unit so that the phase of the voltage value and the phase of the current value measured by the detection unit are matched with each other and the current value is equal to or greater than a predetermined value. The frequency range to be changed is changed, and in the first frequency range, the phase of the voltage value and the phase of the current value measured by the detection unit match each other, and the current value is the predetermined value The ultrasonic processing apparatus characterized by periodically changing the frequency of the electric power output from the oscillating unit within the first frequency range when the value exceeds a value .

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